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  • Weitere Quellen  (179)
  • Aircraft Propulsion and Power
  • Cell & Developmental Biology
  • Seismology
  • 2005-2009  (179)
  • 1940-1944
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  • 2006  (179)
  • 1
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    Advanced Thermal HPT Clearance Control (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-08-17
    Beschreibung: OBJECTIVE: Develop a fast acting HPT Active Clearance Control System to improve engine efficiency and reduce emissions CHALLENGE: Reduction of HPT blade clearance throughout engine operation System complexity, reliability and cost must remain comparable or surpass today s engines Reduced clearance may increase possibility of rubs
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: 2005 NASA Seal/Secondary Air System Workshop, Volume 1; 167-178; NASA/CP-2006-214383/VOL1
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 2
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    Endwall Treatment and Method for Gas Turbine (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-08-13
    Beschreibung: An endwall treatment for a gas turbine engine having at least one rotor blade extending from a rotatable hub and a casing circumferentially surrounding the rotor and the hub, the endwall treatment including, an inlet formed in an endwall of the gas turbine engine adapted to ingest fluid from a region of a higher-pressure fluid, an outlet formed in the endwall and located in a region of lower pressure than the inlet, wherein the inlet and the outlet are in a fluid communication with each other, the outlet being adapted to inject the fluid from the inlet in the region of lower pressure, and wherein the outlet is at least partially circumferentially offset relative to the inlet.
    Schlagwort(e): Aircraft Propulsion and Power
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 3
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    PAB3D: Its History in the Use of Turbulence Models in the Simulation of Jet and Nozzle Flows (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This is a review paper for PAB3D s history in the implementation of turbulence models for simulating jet and nozzle flows. We describe different turbulence models used in the simulation of subsonic and supersonic jet and nozzle flows. The time-averaged simulations use modified linear or nonlinear two-equation models to account for supersonic flow as well as high temperature mixing. Two multiscale-type turbulence models are used for unsteady flow simulations. These models require modifications to the Reynolds Averaged Navier-Stokes (RANS) equations. The first scheme is a hybrid RANS/LES model utilizing the two-equation (k-epsilon) model with a RANS/LES transition function, dependent on grid spacing and the computed turbulence length scale. The second scheme is a modified version of the partially averaged Navier-Stokes (PANS) formulation. All of these models are implemented in the three-dimensional Navier-Stokes code PAB3D. This paper discusses computational methods, code implementation, computed results for a wide range of nozzle configurations at various operating conditions, and comparisons with available experimental data. Very good agreement is shown between the numerical solutions and available experimental data over a wide range of operating conditions.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: 44th AIAA Aerospace Sciences Meeting and Exhibit; Jan 09, 2006 - Jan 12, 2006; Reno, NV; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 4
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    Two Point Space-Time Correlation of Density Fluctuations Measured in High Velocity Free Jets (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Two-point space-time correlations of air density fluctuations in unheated, fully-expanded free jets at Mach numbers M(sub j) = 0.95, 1.4, and 1.8 were measured using a Rayleigh scattering based diagnostic technique. The molecular scattered light from two small probe volumes of 1.03 mm length was measured for a completely non-intrusive means of determining the turbulent density fluctuations. The time series of density fluctuations were analyzed to estimate the integral length scale L in a moving frame of reference and the convective Mach number M(sub c) at different narrow Strouhal frequency (St) bands. It was observed that M(sub c) and the normalized moving frame length scale L*St/D, where D is the jet diameter, increased with Strouhal frequency before leveling off at the highest resolved frequency. Significant differences were observed between data obtained from the lip shear layer and the centerline of the jet. The wave number frequency transform of the correlation data demonstrated progressive increase in the radiative part of turbulence fluctuations with increasing jet Mach number.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2006-214222 , AIAA paper 2006-0006 , E-15470 , 44th Aerospace Sciences Meeting and Exhibit; Jan 09, 2006 - Jan 12, 2006; Reno, NV; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Model-Based Self-Tuning Multiscale Method for Combustion Control (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A multi-scale representation of the combustor dynamics was used to create a self-tuning, scalable controller to suppress multiple instability modes in a liquid-fueled aero engine-derived combustor operating at engine-like conditions. Its self-tuning features designed to handle the uncertainties in the combustor dynamics and time-delays are essential for control performance and robustness. The controller was implemented to modulate a high-frequency fuel valve with feedback from dynamic pressure sensors. This scalable algorithm suppressed pressure oscillations of different instability modes by as much as 90 percent without the peak-splitting effect. The self-tuning logic guided the adjustment of controller parameters and converged quickly toward phase-lock for optimal suppression of the instabilities. The forced-response characteristics of the control model compare well with those of the test rig on both the frequency-domain and the time-domain.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2006-213855 , AIAA Paper 2005-3593 , E-15225 , 41st Joint Propulsion Conference and Exhibit; Jul 10, 2005 - Jul 13, 2005; Tucson, AZ; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 6
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    Rate-Based Model Predictive Control of Turbofan Engine Clearance (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: An innovative model predictive control strategy is developed for control of nonlinear aircraft propulsion systems and sub-systems. At the heart of the controller is a rate-based linear parameter-varying model that propagates the state derivatives across the prediction horizon, extending prediction fidelity to transient regimes where conventional models begin to lose validity. The new control law is applied to a demanding active clearance control application, where the objectives are to tightly regulate blade tip clearances and also anticipate and avoid detrimental blade-shroud rub occurrences by optimally maintaining a predefined minimum clearance. Simulation results verify that the rate-based controller is capable of satisfying the objectives during realistic flight scenarios where both a conventional Jacobian-based model predictive control law and an unconstrained linear-quadratic optimal controller are incapable of doing so. The controller is evaluated using a variety of different actuators, illustrating the efficacy and versatility of the control approach. It is concluded that the new strategy has promise for this and other nonlinear aerospace applications that place high importance on the attainment of control objectives during transient regimes.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2006-214419 , E-15692 , 42nd AIAA Joint Propulsion Conference and Exhibit; Jul 09, 2006 - Jul 12, 2006; Sacramento, CA; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
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    Adaptive Engine Technologies for Aviation CO2 Emissions Reduction (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Adaptive turbine engine technologies are assessed for their potential to reduce carbon dioxide emissions from commercial air transports.Technologies including inlet, fan, and compressor flow control, compressor stall control, blade clearance control, combustion control, active bearings and enabling technologies such as active materials and wireless sensors are discussed. The method of systems assessment is described, including strengths and weaknesses of the approach. Performance benefit estimates are presented for each technology, with a summary of potential emissions reduction possible from the development of new, adaptively controlled engine components.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2006-214392 , E-15670 , AIAA Paper 2006-5105 , 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference; Jul 09, 2006 - Jul 12, 2006; Sacreamento, CA; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 8
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    Predicting the Effects of Test Media in Ground-Based Propulsion Testing (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This paper discusses the progress of work which began in mid-2004 sponsored by the Office of the Secretary of Defense (OSD) Test & Evaluation/Science & Technology (T&E/S&T) Program. The purpose of the work is to improve the state of the art of CFD capabilities for predicting the effects of the test media on the flameholding characteristics in scramjet engines. The program has several components including the development of advance algorithms and models for simulating engine flowpaths as well as a fundamental experimental and diagnostic development effort to support the formulation and validation of the mathematical models. The paper will provide details of current work involving the development of phenomenological models for Reynolds averaged Navier-Stokes codes, large-eddy simulation techniques and reduced-kinetics models. Experiments that will provide data for the modeling efforts will also be described, along with with the associated nonintrusive diagnostics used to collect the data.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: 2006 Annual ITEA Technology Review; Aug 07, 2006 - Aug 10, 2006; Cambridge, MA; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 9
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    Technologies for Aircraft Noise Reduction (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Technologies for aircraft noise reduction have been developed by NASA over the past 15 years through the Advanced Subsonic Technology (AST) Noise Reduction Program and the Quiet Aircraft Technology (QAT) project. This presentation summarizes highlights from these programs and anticipated noise reduction benefits for communities surrounding airports. Historical progress in noise reduction and technologies available for future aircraft/engine development are identified. Technologies address aircraft/engine components including fans, exhaust nozzles, landing gear, and flap systems. New "chevron" nozzles have been developed and implemented on several aircraft in production today that provide significant jet noise reduction. New engines using Ultra-High Bypass (UHB) ratios are projected to provide about 10 EPNdB (Effective Perceived Noise Level in decibels) engine noise reduction relative to the average fleet that was flying in 1997. Audio files are embedded in the presentation that estimate the sound levels for a 35,000 pound thrust engine for takeoff and approach power conditions. The predictions are based on actual model scale data that was obtained by NASA. Finally, conceptual pictures are shown that look toward future aircraft/propulsion systems that might be used to obtain further noise reduction.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: West Park Airport Committee Meeting; Feb 16, 2006; Cleveland, OH; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 10
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    A Theoretical Solid Oxide Fuel Cell Model for System Controls and Stability Design (2006)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: As the aviation industry moves towards higher efficiency electrical power generation, all electric aircraft, or zero emissions and more quiet aircraft, fuel cells are sought as the technology that can deliver on these high expectations. The Hybrid Solid Oxide Fuel Cell system combines the fuel cell with a microturbine to obtain up to 70 percent cycle efficiency, and then distributes the electrical power to the loads via a power distribution system. The challenge is to understand the dynamics of this complex multi-discipline system, and design distributed controls that take the system through its operating conditions in a stable and safe manner while maintaining the system performance. This particular system is a power generation and distribution system and the fuel cell and microturbine model fidelity should be compatible with the dynamics of the power distribution system in order to allow proper stability and distributed controls design. A novel modeling approach is proposed for the fuel cell that will allow the fuel cell and the power system to be integrated and designed for stability, distributed controls, and other interface specifications. This investigation shows that for the fuel cell, the voltage characteristic should be modeled, but in addition, conservation equation dynamics, ion diffusion, charge transfer kinetics, and the electron flow inherent impedance should also be included.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2006-214104 , GT2006-91247 , E-15439 , Turbo Expo 2006; May 08, 2006 - May 11, 2006; Barelona; Spain
    Format: application/pdf
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