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  • Other Sources  (585)
  • AERODYNAMICS  (366)
  • AIRCRAFT PROPULSION AND POWER  (219)
  • Animals
  • 1980-1984  (585)
  • 1925-1929
  • 1981  (585)
  • 1
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    Curved-flow, rolling-flow, and oscillatory pure-yawing wind-tunnel test methods for determination of dynamic stability derivatives (1981)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: The test capabilities of the Stability Wind Tunnel of the Virginia Polytechnic Institute and State University are described, and calibrations for curved and rolling flow techniques are given. Oscillatory snaking tests to determine pure yawing derivatives are considered. Representative aerodynamic data obtained for a current fighter configuration using the curved and rolling flow techniques are presented. The application of dynamic derivatives obtained in such tests to the analysis of airplane motions in general, and to high angle of attack flight conditions in particular, is discussed.
    Keywords: AERODYNAMICS
    Type: AGARD Dyn. Stability Parameters; 13 p
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  • 2
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    An analytic solution to the classical two-body problem with drag (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The two body problem was analyzed with a specific drag model. The model treats drag as a force proportional to the vector velocity and inversely proportional to the distance to the center of attraction. The solution is expressed in terms of known functions and is of a simple and compact form. The time of flight is expressed as a quadrature in the true anomaly. The results are: (1) development of a vector differential equation which allows analysis of an infinite number of gravitational and drag models; and (2) obtaining the solution of a linear differential equation using the inverse method of laplace transforms.
    Keywords: AERODYNAMICS
    Type: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 22 p
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  • 3
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    Langley high-lift research on a high-aspect-ratio supercritical wing configuration (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: To determine the low speed performance characteristics of a representative high aspect ratio supercritical wing, two low speed jet transport models were fabricated. A 12-ft. span model was used for low Reynolds number tests in the Langley 4- by 7-Meter Tunnel and the second, a 7.5-ft. span model, was used for high Reynolds number tests in the Ames 12-foot Pressure Tunnel. A brief summary of the results of the tests of these two models is presented and comparisons are made between the data obtained on these two models and other similar models. Follow-on two and three dimensional research efforts related to the EET high-lift configurations are also presented and discussed.
    Keywords: AERODYNAMICS
    Type: Advan. Aerodyn.: Selected NASA Res.; p 55-77
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  • 4
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    Measured transonic unsteady pressures on an energy efficient transport wing with oscillating control surfaces (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Highlight results are presented from subsonic and transonic pressure measurement studies conducted in the Langley Transonic Dynamics Tunnel on a supercritical wing model representative of an energy efficient transport design. Steady- and unsteady-pressure data were acquired on the upper and lower wing surface at an off-design Mach number of 0.60 and at the design Mach number of 0.78, for a Reynolds number of 2.2 x 10(6) (based on the wing average chord). The model configuration consisted of a sidewall-Mounted half-body fuselage and a semi-span wing with an aspect ratio of 10.76, a leading-edge sweepback angle of 28.8 degrees, and supercritical airfoil sections. The wing is instrumented with 252 static pressure orifices and 164 dynamic pressure gages. Model test variables included wing angle of attack, control-surface mean deflection angle, control-surface oscillating deflection angle and frequency, and phasing between oscillating leading-edge and trailing-edge controls when used together.
    Keywords: AERODYNAMICS
    Type: Advan. Aerodyn.: Selected NASA Res.; p 21-36
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  • 5
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    Vortex-flow aerodynamics - An emerging design capability (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Promising current theoretical and simulational developments in the field of leading edge vortex-generating delta, arrow ogival wings are reported, along with the history of theory and experiment leading to them. The effects of wing slenderness, leading edge nose radius, Mach number and incidence variations, and planform on the onset of vortex generation and redistribution of aerodynamic loads are considered. The range of design possibilities in this field are consequential for the future development of strategic aircraft, supersonic transports and commercial cargo aircraft which will possess low-speed, high-lift capability by virtue of leading edge vortex generation and control without recourse to heavy and expensive leading edge high-lift devices and compound airfoils. Attention is given to interactive graphics simulation devices recently developed.
    Keywords: AERODYNAMICS
    Type: Astronautics and Aeronautics; 19; May 1981
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  • 6
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    Longitudinal grooves for bluff body drag reduction (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Wind tunnel test results are presented for four axisymmetric bluff body configurations in order to determine their effect on form and pressure drag. It was found that drag reductions on the order of 40% are obtainable with an afterbody incorporating four longitudinal 'V' grooves. Although this effect may be due to the functioning of the grooves as longitudinal, continuous vortex generators, it is concluded that further research is needed to elucidate the physical basis of the test results. Optimization of the effect will be useful in base drag reduction for such vehicles as automobiles and cargo aircraft with sharply upswept afterbodies.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Apr. 198
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  • 7
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    Vectored injection into compressible laminar and turbulent boundary layers (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A fundamental analysis of two-dimensional supersonic boundary layer flow, both laminar and turbulent, is presented for a wide range of normal and nonnormal mass-transfer velocities. The analysis is based on the numerical solution of the Navier-Stokes equations, and results are compared with available theoretical and experimental data. Certain cases of practical importance, for which results are not presently available, are referred to.
    Keywords: AERODYNAMICS
    Type: Computer Methods in Applied Mechanics and Engineering; 25; Jan. 198
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  • 8
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    Report of the panel on theoretical aerodynamics (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Interactions between theoretical aerodynamics and the NTF are discussed. The development and validation of computational fluid dynamics computer codes, the determination of Reynolds number scaling laws, and extension of the data bases of entrainment type turbulence models to include high Reynolds number data are recommended areas of study. The major benefit theoretical aerodynamics could have on the NTF is in the quantitative description of wind tunnel wall interference effects.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 277-286
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  • 9
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    High Reynolds number research requirements for space vehicle design (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Requirements of entry vehicle design requiring high Reynolds number wind tunnel testing are discussed. The space shuttle orbiter, development of future space transportation systems, and planetary entry data analysis are considered.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 265-274
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  • 10
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    Report of the panel on aeroelasticity and unsteady aerodynamics (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The status of recommended areas of study for the NTF are reviewed. Transonic and control surface unsteady aerodynamics, and buffet onset and loads are considered. Testing of dynamically scaled flutter models is discussed.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 237-246
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  • 11
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    Model experience in the Langley 0.3-m transonic cryogenic tunnel (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The model building, development, and testing experience gained during 8 years of operation of the 0.3-m Transonic Cryogenic Tunnel (TCT) is summarized. The summary is divided into four portions: (1) models tested in the 0.3-m TCT's original octagonal test section; (2) models tested in the present two dimensional test section; (3) models tested as a part of tunnel calibration and the development of advanced technology airfoils; and (4) development of a new way to construct two dimensional airfoil models. Design requirements imposed on the models by high Reynolds number testing at cryogenic temperatures are reviewed.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 53-73
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  • 12
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    Quiet propulsive-lift technology ready for civil and military applications (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Quiet Short-Haul Research Aircraft (QSRA) was designed as research aircraft for investigating terminal-area operations with an advanced propulsive-lift aircraft. The QSRA is a modified De Havilland C-8 Buffalo. The modification to the C-8 consisted of adding a new swept wing with four top-mounted Lycoming YF-102 turbofan engines to provide high levels of propulsive-lift through upper-surface blowing. The state of the art has reached the point where consideration can be given to various applications, including military transport aircraft, civil transports, and business jets. Attention is also given to a ground attack plane with QSRA, the payload advantage resulting from applying propulsive-life technology, and aspects of takeoff performance
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Astronautics and Aeronautics; 19; Apr. 198
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  • 13
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    Effectiveness of leading-edge vortex flaps on 60 and 75 degree delta wings (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A series of wind tunnel tests were run on 60 and 75 deg sweep delta wings to examine the effectiveness of leading-edge vortex flaps. Tests results showed that leading-edge vortex flaps are effective in giving large increases in lift-to-drag ratio and decreases in drag over a wide range of angle of attack. Tests on inverted flaps on the 60 deg delta wing showed substantial increases in lift and drag and may indicate a possibility of using inverted flaps on delta wings in the landing portion of flight. The 60 deg data were compared with that for a 75 deg sweep delta wing confirming that leading-edge vortex flap effectiveness is stronger as sweep is increased. Pitching moment effects due to vortex flaps use were also examined.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; Apr. 198
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  • 14
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    Partially confined multiple jet mixing (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results of hot-wire measurements in an incompressible partially confined jet issuing from an array of rectangular nozzles, equally spaced with their small dimensions aligned are presented. The quantities measured include mean velocity and the Reynolds stress in the two central planes of the jet at stations covering up to 115 widths (small dimension of a nozzle) downstream of the nozzle exit. For downstream distances greater than 60 widths, the flowfield is observed to be nearly homogenous and the turbulence appears to be quite similar to that of a grid generated turbulence.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 15
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    Unsteady Newton-Busemann flow theory. I - Airfoils (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Newtonian flow theory for unsteady flow at very high Mach numbers is completed by the addition of a centrifugal force correction to the impact pressures. The correction term is the unsteady counterpart of Busemann's centrifugal force correction to impact pressures in steady flow. For airfoils of arbitary shape, exact formulas for the unsteady pressure and stiffness and damping-in-pitch derivatives are obtained in closed form, which require only numerical quadratures of terms involving the airfoil shape. They are applicable to airfoils of arbitrary thickness having sharp or blunt leading edges. For wedges and thin airfoils these formulas are greatly simplified, and it is proved that the pitching motions of thin airfoils of convex shape and of wedges of arbitrary thickness are always dynamically stable according to Newton-Busemann theory. Leading-edge bluntness is shown to have a favorable effect on the dynamic stability; on the other hand, airfoils of concave shape tend toward dynamic instability over a range of axis positions if the surface curvature exceeds a certain limit. As a byproduct, it is also shown that a pressure formula recently given by Barron and Mandl for unsteady Newtonian flow over a pitching power-law shaped airfoil is erroneous and that their conclusion regarding the effect of pivot position on the dynamic stability is misleading.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 16
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    Evidence of imbedded vortices in a three-dimensional shear flow (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Vortex phenomena encountered in an investigation of the streamwise development of the three-dimensional wake region behind the tip of a three-dimensional wedge model are reported. Pressure profiles were measured by pitot probes downstream of a tip with a nearly constant surface pressure level and a nearly continuous surface curvature in a blowdown air tunnel operating at Mach 6. Rather than the simple three-dimensional quasi-parallel shear flow expected, the measurements indicated the presence of a flow with large deficits in longitudinal pitot pressure, which are usually associated with the core region of quasi-steady longitudinal vortices. Vapor screen flow visualizations also support the presence of longitudinal vortices located primarily in the tip region and evidently forming in the vicinity of the wake neck. An increase in overall wake thickness by 100% is also observed. The origin of the vortices as quasi-steady Taylor-Gortler vortices generated in the concavely curved shear layer near the wake neck is considered. It is pointed out that the existence of longitudinal vortexes suggests that three-dimensional turbulence modeling may be much more difficult than previously supposed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 17
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    Proposed aeroelastic and flutter tests for the National Transonic Facility (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Tests that can exploit the capability of the NTF and the transonic cryogenic tunnel, or lead to improvements that could enhance testing in the NTF are discussed. Shock induced oscillation, supersonic single degree control surface flutter, and transonic flutter speed as a function of the Reynolds number are considered. Honeycombs versus screens to smooth the tunnel flow and a rapid tunnel dynamic pressure reducer are recommended to improve tunnel performance.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 153-161
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  • 18
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    Report of the wind tunnel/flight correlation panel (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Basic calibration of the tunnel prior to conducting any tests, the areas requiring wind tunnel/flight test correlation for validating the NTF, and recommendations for achieving validation of the NTF are discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 249-262
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  • 19
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    High lift technology (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The NASA Langley high lift technology program is reviewed and elements of the program which are considered Reynolds number sensitive are discussed. The Energy Efficient Transport (EET) and Supersonic Cruise Research (SCR) models proposed for high lift studies in the National Transonic Facility (NTF) are described. Recommendations regarding the NTF facility and test techniques are presented.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 197-213
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  • 20
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    Wall interference effects: Status review (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interference technology incorporated into the NTF design (hardware) and the emerging transonic wall interference assessment correction procedures (software) to be employed when the NTF becomes operational was reviewed. It is anticipated that the early experiments will provide data relevant to wall interference effects.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 123-241
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  • 21
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    Configuration aerodynamics (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Static aerodynamic research related to aircraft configurations in their cruise or combat modes is discussed. Subsonic transport aircraft, transonic tactical aircraft, and slender wing aircraft are considered. The status and plans of Langley's NTF configuration research program are reviewed. Recommendations for near term configuration research are made.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 217-234
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  • 22
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    Comments on Reynolds number effects and the role of NTF in the development of air vehicles (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The National Transonic Facility (NTF) capability to match the full scale Reynolds numbers of all but the largest airplanes is discussed. Conversion factors to enable calculation of Sl-unit equivalents for all U.S. units are listed. Using data from several facilities, analytic methods, and flight test data, a competetive aircraft in the relatively low Reynolds number was developed. The NTF offers the capability to obtain data at full scale Reynolds numbers in the cruise condition for most of the products, and will be much closer than previous tunnels to full scale Reynolds number for the operating envelopes. It is primarily on the operating envelope that Reynolds number effects are most important and least predictable.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 143-148
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  • 23
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    Solution of the transonic full potential equation in conservative form using an implicit algorithm (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The paper presents numerical solutions of the full potential equation in conservative form. The iteration scheme used is a fully implicit approximate factorization technique and provides a significant improvement in convergence speed relative to standard successive line overrelaxation algorithms. The spatial differencing algorithm is centrally differenced in both subsonic and supersonic regions to maintain stability. This effectively approximates rotated differencing, thereby greatly improving the reliability of the algorithm.
    Keywords: AERODYNAMICS
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  • 24
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    Computation of airfoil buffet boundaries (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The ILLIAC IV computer has been programmed with an implicit, finite-difference code for solving the thin layer compressible Navier-Stokes equation. Results presented for the case of the buffet boundaries of a conventional and a supercritical airfoil section at high Reynolds numbers are found to be in agreement with experimentally determined buffet boundaries, especially at the higher freestream Mach numbers and lower lift coefficients where the onset of unsteady flows is associated with shock wave-induced boundary layer separation.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Nov. 198
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  • 25
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    Application of unsteady airfoil theory to rotary wings (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A clarification is presented on recent work concerning the application of unsteady airfoil theory to rotary wings. The application of this theory may be seen as consisting of four steps: (1) the selection of an appropriate unsteady airfoil theory; (2) the resolution of that velocity which is the resultant of aerodynamic and dynamic velocities at a point on the elastic axis into radial, tangential and perpendicular components, and the angular velocity of a blade section about the deformed axis; (3) the expression of lift and pitching moments in terms of the three components; and (4) the derivation of explicit expressions for the components in terms of flight velocity, induced flow, rotor rotational speed, blade motion variables, etc.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; July 198
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  • 26
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    The coupling between flow instabilities and incident disturbances at a leading edge (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is now generally agreed that an external disturbance field, such as an incident acoustic wave, can effectively couple to instabilities of a flow past a trailing edge. One purpose of the present paper is to show that there are situations where a similar coupling can occur at a leading edge. The process is analyzed and the effects of experimentally controllable parameters are assessed. It is important to account for such phenomena when evaluating the effect of external disturbances on transition.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 104; Mar. 198
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  • 27
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    A discrete vortex method for the non-steady separated flow over an airfoil (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A discrete vortex method was used to analyze the separated non-steady flow about a cambered airfoil. The foil flow modelling is based on the thin lifting-surface approach, where the chordwise location of the separation point is assumed to be known from experiments or flow-visualization data. Calculated results provided good agreement when compared with the post-stall aerodynamic data of two airfoils. Those airfoil sections differed in the extent of travel of the separation point with increasing angle of attack. Furthermore, the periodic wake shedding was analyzed and its time-dependent influence on the airfoil was investigated.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 102; Jan. 198
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  • 28
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    Pathfinder model program for the National Transonic Facility (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An overview of the Pathfinder Models Program is presented. The Pathfinder program is a major research and development activity in support of the National Transonic Facility Activation Plan. The program scope, models design approach, and Pathfinder model configurations are presented along with a discussion of major supportive program activities. The anticipated design criteria for NTF models are presented.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 37-52
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  • 29
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    Trailing edge noise prediction using Amiet's method (1981)
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    Publication Date: 2011-08-18
    Description: Amiet's (1976, 1978) solution to the problem of airfoil trailing edge noise prediction is discussed in light of the results of evanescent wave theory's application to the measured surface pressure behavior near the trailing edge of an airfoil with a turbulent boundary layer. The method employed by Amiet has the advantage of incorporating the effect of finite chord in its solution. The assumed form of the pressure distribution is examined as well as the constant turbulent boundary layer convection assumption, which is found to be unnecessarily restrictive.
    Keywords: AERODYNAMICS
    Type: Journal of Sound and Vibration; 77; Aug. 8
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  • 30
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    Forebody drag reduction (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is shown that the mechanisms of forebody drag reduction by means of either a spike or a forward-facing jet are similar, with the maximum achievable drag reduction being of the same order. Because the jet may be a relatively cool gas, however, the forward facing jet has the additional capability of reducing the aerodynamic heating that is so severe at high Mach numbers. By means of the correlation presented, jet ejection parameters may be chosen to achieve maximum permissible forebody drag reduction. The correlation method uses a momentum coefficient that characterizes jet efflux and freestream conditions.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Oct. 198
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  • 31
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    Unsteady Newton-Busemann flow theory. II - Bodies of revolution (1981)
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    Publication Date: 2011-08-18
    Description: A complete Newtonian flow theory is presented for unsteady flow past oscillating bodies of revolution of general shape at very high Mach numbers, consideration being given to a centrifugal force correction to the impact pressures. Expressions are obtained for the unsteady pressure and the stability derivatives are presented in closed form. It is stressed that the correction for the centrifugal force, which arises because of the curved trajectories that fluid particles follow along the surface subsequent to their impact, must not be neglected. If the correction is included, the theory is shown to be in excellent agreement with experimental results for relatively sharp cones. Theoretical results are in poor agreement with experimental results in air for bodies having moderate or large-nose bluntness.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Oct. 198
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  • 32
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    Component research for future propulsion systems (1981)
    In:  CASI
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    Publication Date: 2017-10-02
    Description: The factors affecting the helicopter market for the past, present, and future are reviewed. Acquisition cost, mission reliability, life cycle cost and civil and military aspects are reviewed. The potential for advanced vehicle configurations with substantial improvements in energy efficiency, operating economics, and characteristics to satisfy the demands of the future market are identified. Advanced propulsion systems required to support these vehicle configurations and the component technology for the engine systems are discussed. The selection of components in areas of economics and efficiency is considered.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AGARD Helicopter Propulsion Systems; 12 p
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  • 33
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    Top-mounted inlet system feasibility for transonic-subsonic fighter aircraft applications (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: To inlet flow field and engine inlet performance data for an advanced fighter aircraft configuration were obtained over the Mach 0.6 to 2.0 range. The studies not only provided extensive data for the baseline arrangement, but also evaluated the effects of key aircraft configuration variables (inlet location, canopy-dorsal integration, wing leading-edge extension planform area, and variable incidence canards) on top inlet performance. In order to set these data in the context of practical aircraft systems top inlet performance is compared with that of more conventional inlet/airframe integrations. The results of these evaluations show that, for the top inlet configuration tested, relatively good inlet performance and compatibility characteristics are maintained during subsonic and transonic maneuver. However, at supersonic speeds, flow expansion over the forebody and wings causes an increase in local inlet Mach number subsequently reduces inlet performance levels. These characteristics infer that although top inlets many not pose a viable design option for aircraft requiring a high degree of supersonic maneuverability, they have distinct promise for vehicles with subsonic and transonic maneuver capabilities.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Power Plant Installation; 17 p
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    Impact of high-alpha aerodynamics on dynamic stability parameters of aircraft and missiles (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The aerodynamic phenomena associated with high angles of attack and their effects on the dynamic stability characteristics of airplane and missile configurations are examined. Information on dynamic effects is limited. Steady flow phenomena and their effects on the forces and moments are reviewed. The effects of asymmetric vortices and of vortex bursting on the dynamic response of flight vehicles are reviewed with respect to their influence on: (1) nonlinearity of aerodynamic coefficients with attitude, rates, and accelerations; (2) cross coupling between longitudinal and lateral directional models of motion; (3) time dependence and hysteresis effects; (4) configuration dependencey; and (5) mathematical modeling of the aerodynamics.
    Keywords: AERODYNAMICS
    Type: AGARD Dyn. Stability Parameters; 18 p
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  • 35
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    Investigation of performance deterioration of the CF6/JT9D high bypass ratio turbofan engines (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The extent and magnitude of performance deterioration of the Pratt and Whitney JT9D, and the General Electric CF6 engine models is presented. Overall engine and contributing module performance deterioration with respect to flight cycles and/or time are analyzed. The overall engine performance deterioration analyses are based on data obtained from historical records, special engine tests, and tests for specific effects. Hardware inspection data from overhaul shops and special module tests are the basis for the modular performance deterioration data used in the analyses. Various damage mechanisms such as seal rubs, erosion, surface roughness and thermal distortion, and how they contribute to performance deterioration are included in the modular analyses. Results indicate that early performance deterioration occurring within the first few flights of these engines is less than 1 percent in cruise specific fuel consumption (SFC), that it is event oriented, and that it is the result of increased blade tip clearances. This performance deterioration gradually increases to about 2.5 to 3.0 percent (including the initial short term deterioration) after 2500 to 3000 flights where increased blade tip clearances, airfoil quality degradation, and thermal distortion are the contributing causes.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AGARD Turbine Engine Testing; 14 p
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  • 36
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    An assessment of theoretical models for viscous and transonic flow (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Topics discussed include shear flow models, simplified models for treating separation, classical linear theory, a local linearization theory, a transonic linear theory, a transonic nonlinear theory, the experiment of Davis, and the experiment of Tijdeman. It is concluded that shear flow models, which have proven very accurate in taking into account boundary layer effects for panel flutter, are likely to be less so for lifting surface flutter. For many applications in transonic flow, transonic linear theory will be adequate.
    Keywords: AERODYNAMICS
    Type: AGARD Boundary Layer Effects on Unsteady Airloads; 28 p
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  • 37
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    Experimental studies of scale effects on oscillating airfoils at transonic speeds (1981)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Scale effects are discussed with reference to a conventional airfoil (NACA 64A010) and a supercritical airfoil (NLR 7301) at mean flow conditions that support both weak and strong shock waves. During the experiment the Reynolds number was varied from 3 x 10 to the sixth power at time history data are presented over the range of reduced frequencies that are important in aeroelastic applications. The experimental data show that viscous effects are important in the case of the supercritical airfoil at all flow conditions and in the case of the conventional airfoil under strong shock wave conditions. Some frequency dependent viscous effects were also observed.
    Keywords: AERODYNAMICS
    Type: AGARD Boundary Layer Effects on Unsteady Airfoils; 13 p
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  • 38
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    Natural laminar flow data from full-scale flight and wind-tunnel experiments (1981)
    In:  Other Sources
    Details
    Publication Date: 2018-12-01
    Description: Experimental results obtained at NASA Langley during studies of natural laminar flow (NLF) over commercially produced aircraft surfaces are reported. The general aviation aircraft examined were light aircraft, yet displayed NLF extents close to the maximum available and equivalent to high performance business aircraft flying envelopes. Sublimating chemicals and acoustic detection techniques were employed to measure the boundary layer transition. Theoretical predictions of boundary layer stability were found to match well with the experimental data, with consideration given to both swept wings and the amplitudes of allowable waves on the airfoil surfaces. The presence of the NLF on the airfoil surfaces confirmed the benefits available from use of composite materials for airfoil surfaces.
    Keywords: AERODYNAMICS
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  • 39
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    Advanced turboprop installation aerodynamics (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The expected aerodynamic effects of a propfan installed on a thick supercritical wing are summarized qualitatively. Nacelle/wing and jet interactions, slipstream incremental velocity, nonuniform inflow, and swirl loss recovery are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Langley Research Center Advan. Aerodyn. and Active Controls; p 171-181
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  • 40
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    An overview of SAE ARP 1587: Aircraft gas turbine engine monitoring system guide (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A systematic approach to developing an engine monitoring system (EMS) is outlined. An extensive shopping list of EMS capabilities and benefits are included. A team approach to developing an EMS is emphasized with a description of the responsibilities of each team member.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 377-380
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  • 41
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    Engine health monitoring systems: Tools for improved maintenance management in the 1980's (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The performance monitoring aspect of maintenance, characteristic of the engine health monitoring system are discussed. An overview of the system activities is presented and a summary of programs for improved monitoring in the 1980's are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 323-340
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  • 42
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    Who needs engine monitoring? (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Operational evaluations of engine monitoring systems (EMS) are discussed. Options for each required EMS phase are reviewed along with the guidance provided for EMS on new systems.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 209-224
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  • 43
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    Advanced turbine blade tip seal system (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An advanced blade/shroud system designed to maintain close clearance between blade tips and turbine shrouds and at the same time, be resistant to environmental effects including high temperature oxidation, hot corrosion, and thermal cycling is described. Increased efficiency and increased blade life are attained by using the advanced blade tip seal system. Features of the system include improved clearance control when blade tips preferentially wear the shrouds and a superior single crystal superalloy tip. The tip design, joint location, characterization of the single crystal tip alloy, the abrasive tip treatment, and the component and engine test are among the factors addressed. Results of wear testing, quality control plans, and the total manufacturing cycle required to fully process the blades are also discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 137-152
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  • 44
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    Conservation of Strategic Aerospace Materials (COSAM) (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Research efforts to reduce the dependence of the aerospace industry on strategic metals, such as cobalt (Co), columbium (Cb), tantalum (Ta), and chromium (Cr), by providing the materials technology needed to minimize the strategic metal content of critical aerospace components for gas turbine engines are addressed. Thrusts in three technology areas are identified: near term activities in the area of strategic element substitution; intermediate-range activities in the area of materials processing; and long term, high risk activities in the area of 'new classes' of high temprature metallic materials. Specifically, the role of cobalt in nickel-base and cobalt-base superalloys vital to the aerospace industry is examined along with the mechanical and physical properties of intermetallics that will contain a minimum of the stragetic metals.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Aircraft Engine Diagnostics; p 189-207
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  • 45
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    The nature of operating flight loads and their effect on propulsion system structures (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Past diagnostics studies revealed the primary causes of performance deterioration of high by-pass turbofan engines to be flight loads, erosion, and thermal distortion. The various types of airplane loads that are imposed on the engine throughout the lifetime of an airplane are examined. These include flight loads from gusts and maneuvers and ground loads from takeoff, landing, and taxi conditions. Clarification is made in definitions of the airframer's limit and ultimate design loads and the engine manufacturer's operating design loads. Finally, the influence of these loads on the propulsion system structures is discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 175-188
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  • 46
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    Performance retention of the RB211 powerplant in service (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An understanding of the mechanisms of deterioration is essential in order that features to counteract performance degradation can be built into the basic design of an engine and nacelle. Furthermore, the interpretation must be continued in service for effective feedback to provide modifications which may be necessary in maintaining a satisfactory performance retention program. The in service assessment must be accurate as to magnitude and causes and this requires consideration of: (1) the powerplant as a complete entity, i.e., the engine components and nacelle including the thrust reverser; (2) measurement of performance in flight rather than by sole reliance on the scaling of test cell data to flight conditions (although some correlation should be possible); and (3) the relationship of engine parts condition to overhaul performance and in flight deterioration level of that engine. These aspects are addressed by consideration of the RB211 engine in service in both the Lockheed L1011 Tristar and Boeing 747 aircraft.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 83-102
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  • 47
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    CF6 High Pressure Compressor and Turbine Clearance Evaluations (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In the CF6 Jet Engine Diagnostics Program the causes of performance degradation were determined for each component of revenue service engines. It was found that a significant contribution to performance degradation was caused by increased airfoil tip radial clearances in the high pressure compressor and turbine areas. Since the influence of these clearances on engine performance and fuel consumption is significant, it is important to accurately establish these relatonships. It is equally important to understand the causes of clearance deterioration so that they can be reduced or eliminated. The results of factory engine tests run to enhance the understanding of the high pressure compressor and turbine clearance effects on performance are described. The causes of clearance deterioration are indicated and potential improvements in clearance control are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 19-42
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  • 48
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    JT8D engine performance retention (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The attractive performance retention characteristics of the JT8D engine are described. Because of its moderate bypass ratio and turbine temperature, and stiff structural design, the performance retention versus flight cycles of the JT8D engine sets a standard that is difficult for other engines to equal. In addition, the significant benefits of refurbishment of the JT8D engine are presented. Cold section refurbishment offers thrust specific fuel consumption improvements of up to 2 percent and payback in less than a year, making a very attractive investment option for the airlines.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 63-81
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  • 49
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    CF 6 engine diagnostics (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A summary of the activities which led to defining deterioration rates of the CF6 family of engines, a description of what was learned, and an identification of means of conserving fuel based upon the program findings are presented. The program to define the deterioration levels and modes for the CF6 family of engines involved four distinct phases: analysis of inbound engine test results, analysis of airline cruise data, analysis of airline test cell data resulting from testing of refurbished engines, and inspection of engine hardware.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 1-17
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  • 50
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    Natural Laminar Flow Flight Experiment (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A supercritical airfoil section was designed with favorable pressure gradients on both the upper and lower surfaces. Wind tunnel tests were conducted in the Langley 8 Foot Transonic Pressure Tunnel. The outer wing panels of the F-111 TACT airplane were modified to incorporate partial span test gloves having the natural laminar, flow profile. Instrumentation was installed to provide surface pressure data as well as to determine transition location and boundary layer characteristics. The flight experiment encompassed 19 flights conducted with and without transition fixed at several locations for wing leading edge sweep angles which varied from 10 to 26 at Mach numbers from 0.80 to 0.85 and altitudes of 7620 meters and 9144 meters. Preliminary results indicate that a large portion of the test chord experienced laminar flow.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center Advan. Aerodyn. and Active Controls; p 135-144
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  • 51
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    Aerodynamic drag reduction tests on a box-shaped vehicle (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The intent of the present experiment is to define a near optimum value of drag coefficient for a high volume type of vehicle through the use of a boattail, on a vehicle already having rounded front corners and an underbody seal, or fairing. The results of these tests will constitute a baseline for later follow-on studies to evaluate candidate methods of obtaining afterbody drag coefficients approaching the boattail values, but without resorting to such impractical afterbody extensions. The current modifications to the box-shaped vehicle consisted of a full and truncated boattail in conjunction with the faired and sealed underbody. Drag results from these configurations are compared with corresponding wind tunnel results of a 1/10 scale model. Test velocities ranged up to 96.6 km/h (60 mph) and the corresponding Reynolds numbers ranged up to 1.3 x 10 to the 7th power based on the vehicles length which includes the boattail. A simple coast-down technique was used to define drag.
    Keywords: AERODYNAMICS
    Type: NASA-CR-176982 , NAS 1.26:176982
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  • 52
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    Why use case studies rather than simulation-gaming techniques or library research? (1981)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: Method which present a student with a more challenging and true to life situation of needing to conduct research in a problem solving context--and not thinking about organization of format until research and thinking are complete are investigated. Simulation-gaming techniques which attempt to teach initiative and creativity that library research are used for this purpose. However, it is shown case studies provide the greatest opportunities to engage the students in problem solving situations in which they develop skills as researchers and writers.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center Tech. Commun., Pt. 1; p 99-103
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  • 53
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    The phenomenon of dynamic stall (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Dynamic stall and its consequences which are important to aircraft design and operation are discussed. A certain degree of unsteadyness always accompanies the flow over streamlined bodies at high angle of attack, however, the stall of lifting surface undergoing unsteady motion is more complex than static stall. Dynamic stall remains a major unsolved problem with a variety of applications in aeronautics, hydrodynamics and wind engineering.
    Keywords: AERODYNAMICS
    Type: Von Karman Inst. for Fluid Dynamics Unsteady Airloads and Aeroelastic Probl. in Separated and Transonic Flow; 28 p
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  • 54
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    A-10/TF34 Turbine Engine Monitoring System (TEMS) (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The hardware and software development of the A-10/TF34 turbine engine monitoring system (TEMS) is described. The operation and interfaces of the A-10/TF34 TEMS hardware are discussed with particular emphasis on function, capabilities, and limitations. The TEMS data types are defined and the various data acquisition modes are explained. Potential data products are also discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 271-283
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  • 55
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    Improving turbine engine compressor performance retention through airfoil coatings (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In order to evaluate the potential effectiveness of coatings in limiting erosive damage to compressor airfoils, an effort was initiated to evaluate candidate coatings for substrate alloys typically used in commercial engine high compressor blades. Laboratory and rig erosion testing of plasma deposited and diffusion coatings described in this paper have shown the potential of a two to four fold improvement in erosion life. The selective application of these coatings to approximately the outer third of the airfoil avoids coating the fatigue critical region of the blade, thus providing erosion resistance potentially without compromising the fatigue strength of the blade. Both the plasma and the diffusion coatings also offer the advantage of low initial cost and a multi-source production base.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 109-117
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  • 56
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    Engine condition monitoring: CF6 family 60's through the 80's (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The on condition program is described in terms of its effectiveness as a maintenance tool both at the line station as well as at home base by the early detection of engine faults, erroneous instrumentation signals and by verification of engine health. The system encompasses all known methods from manual procedures to the fully automated airborne integrated data system.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 341-356
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  • 57
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    Review of AIDS development (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The operation and implementation of the aircraft integrated data system AIDS are described. The system is described as an engineering tool with strong emphasis on analysis of recorded information. The AIDS is primarily directed to the monitoring of parameters related to: the safety of the flight; the performance of the aircraft; the performance of the flight guidance system; and the performance and condition of the engines. The system provide short term trend analysis on a trend chart that is updated by the flight engineer on every flight that lasts more than 4 flight hours. Engine data prints are automatically presented during take-off and in the case of limit excedance, e.g., the print shows an automatically reported impending hotstarts on engine nr. 1. Other significant features are reported.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 285-310
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  • 58
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    F100 engine diagnostic system status to date (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An engine diagnostic system, proposed for the F100 engine, was tested in five specially modified Tactical Air Command F-15 aircraft during a 16-month flight evaluation. After more than 3300 engine operating hours encompassing almost 900 flights during the flight evaluation, these aircraft provided a data base, still being analyzed, that has shown successful demonstration of the original functional characteristics. Four general design requirements, recording engine operating time/low cycle fatigue event detection, engine trim, and trend and performance data collection were demonstrated. Also, validation of maintenance actions taken and indicated needed maintenance were successfully demonstrated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 225-242
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  • 59
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    An introduction to NASA's turbine engine hot section technology (HOST) project (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An overview of research to develop and improve the accuracy of current analysis methods so that increased durability can be designed into future engines is presented. Emphasis is placed on improved accuracy in life prediction. Component design, including description of the thermal and aerodynamic environments, the material's mechanical response, the interactions between environmental and structural response, and high temperature instrumentation capable of measuring near-engine environment effects are addressed. Component tests, improved modeling of the physical phenomena, and tests to verify the proved models are also discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Aircraft Engine Diagnostics; p 153-173
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  • 60
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    Performance deterioration: An airline perspective (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Certain features of engine design and installation are clearly demonstrating important advantages in engine performance retention. Bearing arrangement no doubt has an important role in performance retention. Four bearings seem to be insufficient while six are probably more than are required. A well designed five-bearing system would seem to be an optimum configuration. Bearings with over-hung components such as fans, should be designed to minimize such over-hang to limit associated wobble, which in turn leads to shroud rub, or to allow closer running clearances. Almost any effort to improve stiffness and generally reduce flexing of the engine structure will pay off significantly in performance retention, even at a weight penalty. For this reason cowl load sharing to provide additional rigidity at a low cost in additional weight and complexity is favored.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Engine Diagnostics; p 103-108
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  • 61
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    Prediction of blade vortex interaction noise from measured blade pressure (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: The impulsive nature of noise due to the interaction of a rotor blade with a tip vortex is studied. The time signature of this noise is calculated theoretically based on the measured blade surface pressure fluctuation of an operational load survey rotor in slow descending flight and is compared with the simultaneous microphone measurement. Particularly, the physical understanding of the characteristic features of a waveform is extensively studied in order to understand the generating mechanism and to identify the important parameters. The interaction trajectory of a tip vortex on an acoustic planform is shown to be a very important parameter for the impulsive shape of the noise. The unsteady nature of the pressure distribution at the very leading edge is also important to the pulse shape. The theoretical model using noncompact linear acoustics predicts the general shape of interaction impulse pretty well except for peak amplitude which requires more continuous pressure information along the span at the leading edge.
    Keywords: AERODYNAMICS
    Type: DGLR Seventh European Rotorcraft and Powered Lift Aircraft Forum; 20 p
    Format: text
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  • 62
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    Two-dimensional aerodynamic characteristics of an airfoil designed for two (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An airfoil designed for helicopter rotor application is investigated. The airfoil is designed to increase maximum normal force coefficient while maintaining favorable drag divergence and pitching moment characteristics. Two modifications are also tested. Maximum normal force coefficient varies from 1.14 to 0.90 at Mach numbers from about 0.35 to 0.65. Both modifications decreased drag coefficient at zero normal force coefficient for Mach numbers near drag divergence, but were less beneficial at a normal force coefficient of -0.2.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1965 , L-14825 , NAS 1.60:1965 , AVRADCOM-TR-81-B-6
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  • 63
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    Selected advanced aerodynamic and active control concepts development (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A task for the Energy Efficient Transport program conducted: (1) The design and wind tunnel development of high-aspect-ratio supercritical wings, investigating the cruise speed regime and also high-lift. (2) The preliminary design and evaluation of an aircraft combining a high-aspect-ratio supercritical wing with a winglet. (3) Active Controls: The determination of criteria, configuration, and flying qualities associated with augmented longitudinal stability of a level likely to be acceptable for the next generation transport; and the design of a practical augmentation system. The baseline against which the work was performed and evaluated was the Douglas DC-X-200 twin engine derivative of the DC-10 transport. The supercritical wing development showed that the cruise and buffet requirements could be achieved and that the wing could be designed to realize a sizable advantage over today's technology. Important advances in high lift performance were shown. The design study of an aircraft with supercritical wing and winglet suggested advantages in weight and fuel economy could be realized. The study of augmented stability, conducted with the aid of a motion base simulator, concluded that a negative static margin was acceptable for the baseline unaugmented aircraft.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3469 , NAS 1.26:3469
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  • 64
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    Bladed-shrouded-disc aeroelastic analyses: Computer program updates in NASTRAN level 17.7 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In October 1979, a computer program based on the state-of-the-art compressor and structural technologies applied to bladed-shrouded-disc was developed. The program was more operational in NASTRAN Level 16. The bladed disc computer program was updated for operation in NASTRAN Level 17.7. The supersonic cascade unsteady aerodynamics routine UCAS, delivered as part of the NASTRAN Level 16 program was recorded to improve its execution time. These improvements are presented.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165428 , NAS 1.26:165428 , D2536-941006
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  • 65
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    Subsonic and transonic pressure measurements on a high-aspect-ratio supercritical-wing model with oscillating control surfaces (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static orifices and 164 in situ dynamic pressure gases for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Data from the present test (this is the second in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60 and 0.78 and are presented in tabular form.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83201 , L-14831 , NAS 1.15:83201
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  • 66
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    Energy efficient engine high-pressure turbine supersonic cascade technology report (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The performance of two vane endwall geometries and three blade sections for the high-pressure turbine was evaluated in terms of the efficiency requirements of the Energy Efficient Engine high-pressure turbine component. The van endwall designs featured a straight wall and S-wall configuration. The blade designs included a base blade, straightback blade, and overcambered blade. Test results indicated that the S-wall vane configuration and the base blade configuration offered the most promising performance characteristics for the Energy Efficient Engine high-pressure turbine component.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165567 , NAS 1.26:165567 , PWA-5594-152
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  • 67
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    Unpowered Aerodynamic Characteristics of a 15-Percent Scale Model of a Twin-Engine Commuter Aircraft (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted in the Ames 12-Foot Pressure Wind Tunnel to determine the unpowered aerodynamic characteristics of a 15-percent-scale model of a twin-engine commuter aircraft. Model longitudinal aerodynamic characteristics were examined at discrete flap deflections for various angle-of-attack and wind-tunnel-velocity ranges with the empennage on and off. Data are presented for the basic model configuration consisting of the fuselage, wing, basic wing leading edge, double slotted flaps, midengine nacelles, and empennage. Other configurations tested include a particle-span drooped leading edge (dropped outboard of the engine nacelles), a full-span drooped leading edge, low- and high-mounted engine nacelles, and a single-slotted flap. An evaluation was made of the model mounting system by comparing data obtained with the model mounted conventionally on the wind-tunnel model-support struts and the model inverted.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81284 , A-8552
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  • 68
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    The influence of unsteady aerodynamics on hingeless rotor ground resonance (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Calculations of the model frequency and damping for a hingeless rotor on a gimballed support in hover are compared with measured results for two configurations (differing in blade flap stiffness). Good correlation is obtaned when an inflow dynamics model is used to account for the influence of the unsteady aerodynamics. The effect of the unsteady aerodynamics is significant for this rotor system. The inflow dynamics model introduces additional states corresponding to perturbations of the wake-induced velocity at the rotor disk. The calculations confirm the experimental observation that the inflow mode introduced by these additional states is measurable for one configuration but not for the other.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81302 , A-8635 , USAAVRADCOM-TR-81-B-16
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  • 69
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    Cold-air performance of compressor-drive turbine of Department of Energy upgraded automobile gas turbine engine. 1: Volute-manifold and stator performance (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The aerodynamic performance of the inlet manifold and stator assembly of the compressor drive turbine was experimentally determined with cold air as the working fluid. The investigation included measurements of mass flow and stator-exit fluid torque as well as radial surveys of total pressure and flow angle at the stator inlet and annulus surveys of total pressure and flow angle at the stator exit. The stator-exit aftermixed flow conditions and overall stator efficiency were obtained and compared with their design values and the experimental results from three other stators. In addition, an analysis was made to determine the constituent aerodynamic losses that made up the stator kinetic energy loss.
    Keywords: AERODYNAMICS
    Type: NASA-TM-82682 , DOE/NASA/1011-34 , E-572 , AVRADCOM-TR-80-C-20
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  • 70
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    An experimental investigation of the aerodynamics and cooling of a horizontally-opposed air-cooled aircraft engine installation (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A flight-test based research program was performed to investigate the aerodynamics and cooling of a horizontally-opposed engine installation. Specific areas investigated were the internal aerodynamics and cooling mechanics of the installation, inlet aerodynamics, and exit aerodynamics. The applicable theory and current state of the art are discussed for each area. Flight-test and ground-test techniques for the development of the cooling installation and the solution of cooling problems are presented. The results show that much of the internal aerodynamics and cooling technology developed for radial engines are applicable to horizontally opposed engines. Correlation is established between engine manufacturer's cooling design data and flight measurements of the particular installation. Also, a flight-test method for the development of cooling requirements in terms of easily measurable parameters is presented. The impact of inlet and exit design on cooling and cooling drag is shown to be of major significance.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3405
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  • 71
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    Performance of semi-transportation-cooled liner in high-temperature-rise combustors (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Results from tests with the Lamilloy combustor liner are compared with results obtained from a conventionally designed, film cooled, step-louver liner. Operation of the Lamilloy liner with counterrotating swirl combustor fuel modules with mixing venturis was possible to a fuel-air ratio of 0.065 without obtaining excessive liner metal temperatures. At the 0.065 fuel-air condition the average liner metal temperature was 140 K and the maximum local temperature 280 K above the inlet air temperature. Combustion efficiency, pattern factor, and smoke data are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TP-1806 , E-494
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  • 72
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    Exhaust emission survey of an F100 afterburning turbofan engine at simulated altitude flight conditions (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Emissions of carbon monoxide, total oxides of nitrogen, unburned hydrocarbons, and carbon dioxide from an F100, afterburning, two spool turbofan engine at simulated flight conditions are reported. For each flight condition emission measurements were made for two or three power levels from intermediate power (nonafterburning) through maximum afterburning. The data showed that emissions vary with flight speed, altitude, power level, and radial position across the nozzle. Carbon monoxide emissions were low for intermediate power (nonafterburning) and partial afterburning, but regions of high carbon monoxide were present downstream of the flame holder at maximum afterburning. Unburned hydrocarbon emissions were low for most of the simulated flight conditions. The local NOX concentrations and their variability with power level increased with increasing flight Mach number at constant altitude, and decreased with increasing altitude at constant Mach number. Carbon dioxide emissions were proportional to local fuel air ratio for all conditions.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-81656 , E-673
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  • 73
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    Aerodynamic and acoustic behavior of a YF-12 inlet at static conditions (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An aeroacoustic test program to determine the cause of YF-12 inlet noise suppression was performed with a YF-12 aircraft at ground static conditions. Data obtained over a wide range of engine speeds and inlet configurations are reported. Acoustic measurements were made in the far field and aerodynamic and acoustic measurements were made inside the inlet. The J-58 test engine was removed from the aircraft and tested separately with a bellmouth inlet. The far field noise level was significantly lower for the YF-12 inlet than for the bellmouth inlet at engine speeds above 5500 rpm. There was no evidence that noise suppression was caused by flow choking. Multiple pure tones were reduced and the spectral peak near the blade passing frequency disappeared in the region of the spike support struts at engine speeds between 6000 and 6600 rpm.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-163106 , LR-29623
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  • 74
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    An experimental and analytical investigation of the aerodynamics of a hypersonic vehicle at free stream Mach 6 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The goal of this research is the assessment of the validity of existing three dimensional numerical programs in the prediction of the flow fields about general three dimensional hypersonic bodies. A detailed experimental research program was performed in which surface and flow field pressures were mapped. The results of the experimental work were compared with existing inviscid programs. Improvements were made on the existing numerical methods to include angle of attack. A summary of this work is presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-164133
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  • 75
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    Aerodynamic preliminary analysis system 2. Part 2: User's manuals (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An aerodynamic analysis system based on potential theory at subsonic/supersonic speeds and impact type finite element solutions at hypersonic conditions is described. Three dimensional configurations having multiple nonplanar surfaces of arbitrary planform and bodies of noncircular contour may be analyzed. Static, rotary, and control longitudinal and lateral directional chracteristics may be generated. The analysis has been implemented on a time sharing system in conjunction with an input tablet digitizer and an interactive graphics input/output display and editing terminal to maximize its responsiveness to the preliminary analysis problem. Typical simulation indicates that program provides an efficient analysis for systematically performing various aerodynamic configuration tradeoff and evaluation studies.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165628 , NA-80-374-PT-2
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  • 76
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    Aerodynamic prediction techniques for hypersonic configuration design (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation of approximate theoretical techniques for predicting aerodynamic characteristics and surface pressures for relatively slender vehicles at moderate hypersonic speeds was performed. Emphasis was placed on approaches that would be responsive to preliminary configuration design level of effort. Potential theory was examined in detail to meet this objective. Numerical pilot codes were developed for relatively simple three dimensional geometries to evaluate the capability of the approximate equations of motion considered. Results from the computations indicate good agreement with higher order solutions and experimental results for a variety of wing, body, and wing-body shapes for values of the hypersonic similarity parameter M delta approaching one.
    Keywords: AERODYNAMICS
    Type: NASA-CR-165651 , NA-80-611
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  • 77
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    The phenomenon of dynamic stall (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The general features of dynamic stall on oscillating airfoils are explained in terms of the vortex shedding phenomenon, and the important differences between static stall, light dynamic stall, and deep stall are described. An overview of experimentation and prediction techniques is given.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81264 , A-8464
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  • 78
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    Spectral flame radiance from a tubular-can combustor (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation was conducted to determine the effects of fuel type, fuel-air ratio, and inlet-air pressure on the spectral flame radiance emanating from a JT8D can combustor. Spectral radiance measurements from 1.55 to 5.5 micrometers of wavelength were recorded and analyzed to determine soot concentration and flame temperature at various axial locations in the combustor. Two fuels differing in volatility, viscosity, and chemical composition were used in this investigation.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TP-1722 , E-509
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  • 79
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    Integrated control system for a gas turbine engine (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A control system for a turbofan engine receives signals from a number of engine sensors and from the engine operator, and generates control signals. One control signal regulates the fan exhaust nozzle area in order to control inlet throat Mach number to maintain a low level of engine noise. Additional control signals regulate fuel flow to control engine thrust and fan pitch to control fan speed. A number of schedules are utilized to maintain a predetermined relationship between the controlled parameters and a number of fixed and calculated limits can override the control signals to prevent unsatisfactory engine performance.
    Keywords: AIRCRAFT PROPULSION AND POWER
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  • 80
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    Apparatus for sensor failure detection and correction in a gas turbine engine control system (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A gas turbine engine control system maintains a selected level of engine performance despite the failure or abnormal operation of one or more engine parameter sensors. The control system employs a continuously updated engine model which simulates engine performance and generates signals representing real time estimates of the engine parameter sensor signals. The estimate signals are transmitted to a control computational unit which utilizes them in lieu of the actual engine parameter sensor signals to control the operation of the engine. The estimate signals are also compared with the corresponding actual engine parameter sensor signals and the resulting difference signals are utilized to update the engine model. If a particular difference signal exceeds specific tolerance limits, the difference signal is inhibited from updating the model and a sensor failure indication is provided to the engine operator.
    Keywords: AIRCRAFT PROPULSION AND POWER
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  • 81
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    Aeropropulsive characteristics of twin nonaxisymmetric vectoring nozzles installed with forward-swept and aft-swept wings (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation was conducted in the Langley 16 Foot Transonic Tunnel to determine the aeropropulsive characteristics of a single expansion ramp nozzle (SERN) and a two dimensional convergent divergent nozzle (2-D C-D) installed with both an aft swept and a forward swept wing. The SERN was tested in both an upright and an inverted position. The effects of thrust vectoring at nozzle vector angles from -5 deg to 20 deg were studied. This investigation was conducted at Mach numbers from 0.40 to 1.20 and angles of attack from -2.0 deg to 16 deg. Nozzle pressure ratio was varied from 1.0 (jet off) to about 9.0. Reynolds number based on the wing mean geometric chord varied from about 3 million to 4.8 million, depending upon free stream number.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1778 , L-13902
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  • 82
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    Experimental investigation of vortices shed by various wing fin configurations (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Forty-six different fins, which were members of twelve plan-form families, were tested. A two dimensional Boeing single element airfoil at an angle of attack of eight degrees and a sweepback angle of thirty-two was used to simulate a portion of the wing of a generator aircraft. Various free stream velocities were used to test any individual fin at its particular angle of attack. While the fin itself was mounted on the upper surface of the generator model, the angle of attack of each fin was varied until stall was reached and/or passed. The relative fin vortex strengths were measured in two ways. First, the maximum angular velocity of a four blade rotor placed in the fin vortex center was measured with the use of a stroboscope. Second, the maximum rolling moment on a following wing model placed in the fin vortex center was measured by a force balance.
    Keywords: AERODYNAMICS
    Type: NASA-CR-163874 , ISU-ERI-AMES-81112
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  • 83
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    Model aerodynamic test results for two variable cycle engine coannular exhaust systems at simulated takeoff and cruise conditions. Comprehensive data report. Volume 3: Graphical data book 2 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Graphical data from wind tunnel tests of variable cycle engine coannular exhaust nozzles are given. Specifically, aerodynamic data for takeoff conditions are presented.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159819-VOL-3-BK-2 , PWA-5550-50-VOL-3-BK-2
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  • 84
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    Model aerodynamic test results for two variable cycle engine coannular exhaust systems at simulated takeoff and cruise conditions. Comprehensive data report. Volume 3: Graphical data book 1 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A graphical presentation of the aerodynamic data acquired during coannular nozzle performance wind tunnel tests is given. The graphical data consist of plots of nozzle gross thrust coefficient, fan nozzle discharge coefficient, and primary nozzle discharge coefficient. Normalized model component static pressure distributions are presented as a function of primary total pressure, fan total pressure, and ambient static pressure for selected operating conditions. In addition, the supersonic cruise configuration data include plots of nozzle efficiency and secondary-to-fan total pressure pumping characteristics. Supersonic and subsonic cruise data are given.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159819-VOL-3-BK-1 , PWA-5550-50-VOL-3-BK-1
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  • 85
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    Model aerodynamic test results for two variable cycle engine coannular exhaust systems at simulated takeoff and cruise conditions. Comprehensive data report. Volume 2: Tabulated aerodynamic data book 3 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tabulated data from wind tunnel tests evaluating the aerodynamic performance of coannular exhaust nozzles are given for test runs 37 through 65.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159819-VOL-2-BK-3 , PWA-5550-5-VOL-2-BK-3
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  • 86
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    Model aerodynamic test results for two variable cycle engine coannular exhaust systems at simulated takeoff and cruise conditions. Comprehensive data report. Volume 2: Tabulated aerodynamic data book 2 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tabulated aerodynamic data from coannular nozzle performance tests are given for test runs 26 through 37. The data include nozzle thrust coefficient parameters, nozzle discharge coefficients, and static pressure tap measurements.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159819-VOL-2-BK-2 , PWA-5550-50-VOL-2-BK-2
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  • 87
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    Model aerodynamic test results for two variable cycle engine coannular exhaust systems at simulated takeoff and cruise conditions. Comprehensive data report. Volume 1: Design layouts (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The design layouts and detailed design drawings of coannular exhaust nozzle models for a supersonic propulsion system are presented. The layout drawings show the assembly of the component parts for each configuration. A listing of the component parts is also given.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159819-VOL-1 , PWA-5550-50-VOL-1
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  • 88
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    Model aerodynamic test results for two variable cycle engine coannular exhaust systems at simulated takeoff and cruise conditions. Comprehensive data report. Volume 2: Tabulated aeroynamic data book 1 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tabulated data from wind tunnel tests conducted to evaluate the aerodynamic performance of an advanced coannular exhaust nozzle for a future supersonic propulsion system are presented. Tests were conducted with two test configurations: (1) a short flap mechanism for fan stream control with an isentropic contoured flow splitter, and (2) an iris fan nozzle with a conical flow splitter. Both designs feature a translating primary plug and an auxiliary inlet ejector. Tests were conducted at takeoff and simulated cruise conditions. Data were acquired at Mach numbers of 0, 0.36, 0.9, and 2.0 for a wide range of nozzle operating conditions. At simulated supersonic cruise, both configurations demonstrated good performance, comparable to levels assumed in earlier advanced supersonic propulsion studies. However, at subsonic cruise, both configurations exhibited performance that was 6 to 7.5 percent less than the study assumptions. At takeoff conditions, the iris configuration performance approached the assumed levels, while the short flap design was 4 to 6 percent less. Data are provided through test run 25.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159819-VOL-2-BK-1 , PWA-5550-50-VOL-2-BK-1
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  • 89
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    Combustor liner durability analysis (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An 18 month combustor liner durability analysis program was conducted to evaluate the use of advanced three dimensional transient heat transfer and nonlinear stress-strain analyses for modeling the cyclic thermomechanical response of a simulated combustor liner specimen. Cyclic life prediction technology for creep/fatigue interaction is evaluated for a variety of state-of-the-art tools for crack initiation and propagation. The sensitivity of the initiation models to a change in the operating conditions is also assessed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165250 , PWA-5684-19
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  • 90
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    Steady and nonsteady supersonic turbulent afterbody flow (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effect of the specific heat ratio gamma of the incoming ideal gas on the flow properties, especially on pressure distributions along the base and sting surfaces and on reattachment distance, was investigated. The specific heat ratios considered were gamma = 1.2, 1.4, and 1.667. Also, effects of other major parameters, such as eddy-viscosity coefficient (or effective Reynolds number) and Mach number, on the afterbody pressure and reattachment distance were studied and are discussed. Evolution of shock induced flow and stabilization time were examined and are discussed for a transient problem. The important influence of the flow-field geometry, pressure distributions, and reattachment distance on the aerodynamics radiative heat transfer for an atmosphere entry probe in high speed flight are briefly described.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1769 , A-8271
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  • 91
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    Prediction of laminar and turbulent primary and secondary flows in strongly curved ducts (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The analysis is based on a primary secondary velocity decomposition in a given coordinate system, and leads to approximate governing equations which correct an a priori inviscid solution for viscous effects, secondary flows, total pressure distortion, heat transfer, and internal flow blockage and losses. Solution of the correction equations is accomplished as an initial value problem in space using an implicit forward marching technique. The overall solution procedure requires significantly less computational effort than Navier-Stokes algorithms. The solution procedure is effective even with the extreme local mesh resolution which is necessary to solve near wall sublayer regions in turbulent flow calculations. Computed solutions for both laminar and turbulent flow compared very favorably with available analytical and experimental results. The overall method appears very promising as an economical procedure for making detailed predictions of viscous primary and secondary flows in highly curved passages.
    Keywords: AERODYNAMICS
    Type: NASA-CR-3388 , R80-900007-12
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  • 92
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    Thermal-barrier-coated turbine blade study (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effects of coating TBC on a CF6-50 stage 2 high-pressure turbine blade were analyzed with respect to changes in the mean bulk temperature, cooling air requirements, and high-cycle fatigue. Localized spallation was found to have a possible deleterious effect on low-cycle fatigue life. New blade design concepts were developed to take optimum advantage of TBCs. Process and material development work and rig evaluations were undertaken which identified the most promising combination as ZrO2 containing 8 w/o Y2O3 applied by air plasma spray onto a Ni22Cr-10Al-1Y bond layer. The bond layer was applied by a low-pressure, high-velocity plasma spray process onto the base alloy. During the initial startup cycles the blades experienced localized leading edge spallation caused by foreign objects.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165351 , SRD-81-083
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  • 93
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    Development of low modulus material for use in ceramic gas path seal applications (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Three candidate materials were examined: Brunsbond (R) Pad; plasma sprayed porous NiCrAlY; and plasma sprayed low modulus microcracked zirconia. Evaluation consisted of mechanical, thermophysical, and oxidation resistance testing along with optical microscopy and a feasibility demonstration of attaching the material to a suitable substrate. The goals of the program were the following: feasibility of fastening or depositing the low modulus system onto a broad range of substrate alloys; feasibility of depositing or forming the low modulus system to a thickness of 0.19 cm to 0.38 cm; potential to attain a modulus of elasticity in the range of 3.4 to 6.9 GPa (0.5 to 1.0 MSI), and an ultimate strength of 17.2 MPa (2.5 ksi); suitable thermal conductivity; and static oxidation life of at least 1000 hours at 1311 K. The results of the program indicate that all three systems offer attractive properties as a strain isolator material.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165469 , R81-915188-13
    Format: application/pdf
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  • 94
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    A new solution-adaptive grid generation method for transonic airfoil flow calculations (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The clustering algorithm is controlled by a second-order, ordinary differential equation which uses the airfoil surface density gradient as a forcing function. The solution to this differential equation produces a surface grid distribution which is automatically clustered in regions with large gradients. The interior grid points are established from this surface distribution by using an interpolation scheme which is fast and retains the desirable properties of the original grid generated from the standard elliptic equation approach.
    Keywords: AERODYNAMICS
    Type: NASA-TM-81330 , A-8733
    Format: application/pdf
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  • 95
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    Effect of leading-edge vortex flaps on aerodynamic performance of delta wings (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effect of leading-edge vortex flaps on the aerodynamic characteristics of highly swept-back wings is analytically investigated, using the free vortex sheet method. The method, based on a three-dimensional inviscid flow model, is an advanced panel type employing quadratic doublet distributions to represent the wing surface, rolled-up vortex sheet and wake and is capable of computing forces, moments and surface pressures.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; Sept
    Format: text
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  • 96
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    Unknown
    Instability and transition in rotating disk flow (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The stability of three-dimensional rotating disk flow is investigated, including the effects of Coriolis forces and streamline curvature. The numerical results show that the critical Reynolds number for establishment of stationary vortex flow is 287. These vortices spiral outward at an angle of about 11.2 deg, and transition to turbulence occurs when their total amplification is about e to the 11th. New experimental results are also reported on the spatial growth rates of the stationary vortices. It is shown that the analysis gives growth rates that compare much better with the experimental results than do results obtained using the Orr-Sommerfeld equation. The experimental results tend to support the numerical prediction that the number of stationary vortices varies directly with the Reynolds number. The calculations also indicate the existence of weakly unstable propagating (type II) modes at low Reynolds numbers (Critical Reynolds Number being approximately equal to 49).
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Sept
    Format: text
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  • 97
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    Effect of sweep angles on aerodynamic performance of double arrow wing - An analytical study (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Hybrid wing planforms are studied for adoption on supersonic transport and fighter aircraft. The free vortex sheet method is used to determine effects of the leading-edge sweep angles on the aerodynamic performance of a double arrow wing with a strake. Results show lift and drag increase with the increase of the inboard and outboard leading-edge sweep angles. However, the lift-to-drag ratio is little influenced by the changes in these sweep angles. Spanwise surface pressure distributions on the aft region are influenced by the inboard sweep angle while the outboard sweep angle has no effect on these pressures. Finally, the experimental data and predicted results are compared to show good agreement.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; Aug. 198
    Format: text
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  • 98
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    Stability and control characteristics of a three-surface advanced fighter configuration at angles of attack up to 45 deg (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The tests were conducted at Mach numbers from 0.40 to 0.90, at angles of attack up to 45 deg for the lower Mach numbers, and at angles of sideslip up to 15 deg. The model variations under study included adding a canard surface and deflecting horizontal tails, ailerons, and rudders.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83171 , L-14433
    Format: application/pdf
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  • 99
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    An experimental study of combustion: The turbulent structure of a reacting shear layer formed at a rearward-facing step (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A premixed propane-air flame is stabilized in a turbulent free shear layer formed at a rearward-facing step. The mean and rms averages of the turbulent velocity flow field were determined by LDV for both reacting and non-reacting flows. The reaching flow was visualized by high speed schlieren photography. Large scale structures dominate the reacting shear layer. The growth of the large scale structures is tied to the propagation of the flame. The linear growth rate of the reacting shear layer defined by the mean velocity profiles is unchanged by combustion but the virtual origin is shifted downstream. The reacting shear layer based on the mean velocity profiles is shifted toward the recirculation zone and the reattachments lengths are shortened by 30%.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165427
    Format: application/pdf
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  • 100
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    Experimental study of the effects of secondary air on the emissions and stability of a lean premixed combustor (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tests were run using a perforated plate flameholder with a relatively short attached recirculation zone and a vee gutter flameholder with a relatively long attached recirculation zone. Combustor streamlines were traced in cold flow tests at ambient pressure. The amount of secondary air entrainment in the recirculation zones of the flameholders was determined by tracer gas testing at cold flow ambient pressure conditions. Combustion tests were caried out at entrance conditions of 0.5 MPa/630K and emission of NOx, CO and unburned hydrocarbons were measured along with lean stability and flashback limits. The degree of entrainment increases as dilution air injection decreases. Flashback appears to be a function of overall equivalence ratio and resistance to flashback increases with increasing combustor entrance velocity. Lean stability limit appears to be a function of both primary zone and flameholder recirculation zone equivalence ratios and resistance to lean blowout increases with increasing combustor entrance velocity.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165422 , GASL-TR-258
    Format: application/pdf
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