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  • 1
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    A moments-based algorithm for optimizing the information mined in post-processing spray images (2016)
    Springer
    Details
    Publication Date: 2016-01-20
    Print ISSN: 0723-4864
    Electronic ISSN: 1432-1114
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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    PAPER CURRENT
  • 2
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    Aspects of the mechanisms of smoke generation by burning materials (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An investigation of smoke generation during the burning of natural and synthetic solid materials (relevant to fire safety problems), under simulated fire conditions, is presented. Smoke formation mechanisms, including flaming and nonflaming combustion, are reviewed, and the complex physical, chemical, and electrical processes, important in smoke particulate production, are identified. With reference to the smoke formation mechanisms, measured experimental data are discussed, and include effects of ventilation gas temperature, dependence on material composition, and chemical analysis of smoke particulates. Significant differences in smoke characteristics are observed between flaming and nonflaming conditions, which is attributed to specific differences in controlling mechanisms and resultant ways leading to particulate formation. The effects of polymer substrate properties and effects of additives for a given substrate on smoke properties are also discussed in terms of basic processes. It is shown that many of the measured trends can be interpreted by considering postulated mechanisms of particulate formation.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Combustion and Flame; 41; June 198
    Format: text
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  • 3
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    A Theoretical Study of Nonlinear Transverse Combustion Instability in Liquid Propellant Rocket Motors (1966)
    In:  CASI
    Details
    Publication Date: 2019-05-29
    Description: Nonsteady flow conditions in subsonic section of Laval nozzle to investigate nonlinear transverse combustion instability in liquid propellant rocket motors
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-75894
    Format: application/pdf
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  • 4
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    A parametric study of the effect of inlet lip shape upon the radiated sound field (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Far field sound radiation predictions for four different axisymmetric inlet lips excited by different tangential acoustic modes at several cut-off ratios are presented. These results were obtained by numerical integration of a special cylindrically symmetric integral representation of the external solutions of the Helmholtz equation which yields unique solutions at all wave numbers. The paper presents plots which detail the dependence of the relative SPL (dB) in the field upon the engine inlet lip shape, the modal input, and the cut-off ratio. Examination of these data indicate that: (1) as the inlet lip becomes larger the predominant acoustic radiation peak in the field becomes narrower and moves towards the centerline of the inlet; (2) as the order of the tangential acoustic mode of the driver increases the radiated sound peak again becomes narrower but moves away from the inlet centerline; and (3) as the cut-off ratio is increased for a specific tangential acoustic mode the predominant radiation peak becomes narrower and moves towards the centerline of the inlet.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 84-0498
    Format: text
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  • 5
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    Experimental determination of the admittances of aluminized propellants by the impedance tube method (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The adaptation of the impedance tube concept for the determination of the pressure coupled admittances and response functions of burning solid propellants is discussed. The results obtained in experiments with UTP-3001 and UTP-19360 aluminized propellants are presented. It is shown that the admittance Y remains constant during the quasi-steady burn period of a test, indicating constant driving of the gas phase disturbance by the burning solid propellant. The measured real part of the admittance is positive, indicating that the burning aluminized propellant is driving the gas phase oscillations. In addition, the measured high gas phase damping, provided by the aluminum oxide particles in the gas phase, suggests that the latter can significantly increase the damping in unstable solid rockets over the investigated frequency range. Finally, it is shown that the wave structure obtained by numerically solving the impedance tube wave equations which utilize the determined propellant admittance as an initial condition and the determined value of G to describe the gas phase losses is in excellent agreement with the measured wave structure.
    Keywords: PROPELLANTS AND FUELS
    Type: NASA. Langley Research Center The 17th JANNAF Combust. Meeting, Vol. 1; p 133-148
    Format: text
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  • 6
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    Theoretical determination of nozzle admittances using a finite element method (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A finite element method (FEM) is used to predict the admittances of axisymmetric nozzles. The flow in the nozzle is assumed to be isentropic and the disturbances are assumed to be small so that linear analyses apply. An approximate two dimensional compressible flow model is used to describe the steady flow in the nozzle. The propagation of acoustic disturbances is governed by the complete linear acoustic wave equation. This partial differential wave equation is transformed to an integral equation using Galerkin's method and Green's theorem is applied so that the acoustic boundary conditions can be introduced through the boundary residuals. A two dimensional finite element method using linear triangular elements is used to solve the integral acoustic equation. A one dimensional FEM is used to solve the reduced nozzle acoustic equation developed by Crocco and the solution is used to verify the sufficiency of the boundary residual formation. It is shown that agreement between predicted values of the admittance and experimental data is quite good.
    Keywords: PROPELLANTS AND FUELS
    Type: APL The 16th JANNAF Combust. Meeting, Vol. 2; p 273-286
    Format: text
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  • 7
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    Measurements of reactive gaseous rocket injector admittances (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper describes the results of an experimental study of the quantitative determination of the capabilities of the combustion processes associated with coaxial gaseous propellant rocket injectors to drive combustor pressure oscillations. The data, obtained by employing the modified impedance tube technique with compressed air as the oxidizer and acetylene gas as the fuel, describe the frequency dependence of the admittance of the combined injector-combustion process. The measured data are compared with the predictions of the Feiler and Heidmann analytical model utilizing different values for the characteristic combustion time tau sub b. The values of tau sub b which result in a best fit between the measured and predicted data are indicated for different equivalence ratios. It is shown that for the coaxial injector investigated in this study the tau sub b varies between 0.7 and 1.2 msec for equivalence ratios in the range of 0.57 to 1.31. In addition, the experimental data indicate that the tested injector system could drive combustion instabilities over a frequency range that is in qualitative agreement with the predictions of the Feiler and Heidmann model.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Combustion Science and Technology; 20; 5-6,; 1979
    Format: text
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  • 8
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    Development of a spinning wave heat engine (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A theoretical analysis and an experimental investigation were conducted to assess the feasibility of developing a spinning wave heat engine. Such as engine would utilize a large amplitude traveling acoustic wave rotating around a cylindrica chamber, and it should not suffer from the inefficiency, noise, and intermittent thrust which characterizes pulse jet engines. The objective of this investigation was to determine whether an artificially driven large amplitude spinning transverse wave could induce a steady flow of air through the combustion chamber under cold flow conditions. In the theoretical analysis the Maslen and Moore perturbation technique was extended to study flat cylinders (pancake geometry) with completely open side walls and a central opening. In the parallel experimental study, a test moel was used to determine resonant frequencies and radial pressure distributions, as well as oscillatory and steady flow velocities at the inner and outer peripheries. The experimental frequency was nearly the same as the theoretical acoustic value for a model of the same outer diameter but without a central hole. Although the theoretical analysis did not predict a steady velocity component, simulaneous measurements of hotwire and microphone responses have shown that the spinning wave pumps a mean flow radially outward through the cavity.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165611 , NAS 1.26:165611
    Format: application/pdf
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  • 9
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    Experimental determination of three-dimensional liquid rocket nozzle admittances. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The three-dimensional nozzle admittance, an important parameter in combustion instability studies, was experimentally measured for several nozzle configurations. The admittance values were obtained using a modification of the classical impedance tube technique. The modified impedance tube method measures the admittance of a duct termination in the presence of one-dimensional mean flow and three-dimensional oscillations. Values of the nozzle admittance were obtained from pressure amplitude measurements taken at discrete points along the length of the tube. To determine the effects of nozzle geometry, nozzles were tested with half-angles of 15, 30, and 45 deg and entrance Mach numbers of 0.08, 0.16, and 0.20. The admittance results are presented as functions of nondimensional frequency for mixed first tangential-longitudinal modes. These results are compared with available theoretical predictions, and good agreement between theory and experiment is shown.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: AIAA Journal; 11; Mar. 197
    Format: text
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  • 10
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    The prediction of nonlinear longitudinal combustion instability in liquid propellant rockets (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analytical technique was developed to solve nonlinear longitudinal combustion instability problems. The analysis yields the transient and limit cycle behavior of unstable motors and the threshold amplitude required to trigger a linearly stable motor into unstable operation. The limit cycle waveforms were found to exhibit shock wave characteristics for most unstable engine operating conditions. A method of correlating the analytical solutions with experimental data was developed. Calculated results indicate that a second-order solution adequately describes the behavior of combustion instability oscillations over a broad range of engine operating conditions, but that higher order effects must be accounted for in order to investigate engine triggering.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-120904
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