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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1969

Scaled lunar module jet erosion experiments

An experimental research program was conducted on the erosion of particulate surfaces by a jet exhaust. These experiments were scaled to represent the lunar module (LM) during landing. A conical cold-gas nozzle simulating the lunar module nozzle was utilized. The investigation was conducted within a large vacuum chamber by using gravel or glass beads as a simulated soil. The effects of thrust, descent speed, nozzle terminal height, particle size on crater size, and visibility during jet erosion were determined. Results indicate that, from an erosion and visibility standpoint, the best landing mode for a lunar module type of vehicle would involve: site inspection and selection above the incipient erosion height, and a fast descent to the highest drop-in altitude that the vehicle structure could withstand. A slow and cautious descent with hovering just above the lunar surface would greatly increase crater size and impair visibility.

Norman S Land↗
NASA NTRS1974

Sealing technology for aircraft gas turbine engines

Experimental evaluation under simulated engine conditions revealed that conventional mainshaft seals have disadvantages of high gas leakage rates and wear. An advanced seal concept, the self-acting face seal, has a much lower gas leakage rate and greater pressure and speed capability. In endurance tests (150 hr) to 43,200 rpm the self-acting seal wear was not measurable, indicating that noncontact sealing operation was maintained even at this high rotative speed. A review of published data revealed that the leakage through gas path seals has a significant effect on thrust specific fuel consumption, stall margin, and engine maintenance. Reducing leakages by reducing seal clearances results in rubbing contact, and then the seal thermal response and wear determines the final seal clearances.

Ludwig, L. P.↗
NASA NTRS1975

Hamilton Standard Q-fan demonstrator dynamic pitch change test program, volume 1

Tests of a full scale variable pitch fan engine to obtain data on the structural characteristics, response times, and fan/core engine compatibility during transient changes in blade angle, fan rpm, and engine power is reported. Steady state reverse thrust tests with a take off nozzle configuration were also conducted. The 1.4 meter diameter, 13 bladed controllable pitch fan was driven by a T55 L 11A engine with power and blade angle coordinated by a digital computer. The tests demonstrated an ability to change from full forward thrust to reverse thrust in less than one (1) second. Reverse thrust was effected through feather and through flat pitch; structural characteristics and engine/fan compatibility were within satisfactory limits.

Demers, W. J.↗
NASA NTRS1976

An in-flight simulation of approach and landing of a STOL transport with adverse ground effect

The results of an in-flight simulation program undertaken to study the problems of landing a representative STOL transport in the presence of adverse ground effects are presented. Landings were performed with variations in ground effect magnitude, ground effect lag, and thrust response. Other variations covered the effects of augmented lift response, SAS-failures, turbulence, segmented approach, and flare warning. The basic STOL airplane required coordinated use of both stick and throttle for consistently acceptable landings, and the presence of adverse ground effects made the task significantly more difficult. Ground effect lag and good engine response gave noticeable improvement, as did augmented lift response.

Ellis, D. R.↗
NASA NTRS1977

Two-dimensional nozzle/airframe integration technology - An overview

The paper reviews the objectives and some of the accomplishments of a number of programs to develop nonaxisymmetric nozzle technology for future tactical aircraft applications. Specific existing fighter aircraft model tests and preliminary studies are discussed which are designed to generate installed nozzle data, including the effects of thrust vectoring and reversal.

Richey, G. K.↗
NASA NTRS1977

NAVTOLAND and flying qualities

The V/STOL operational capability is reviewed with emphasis on pilot workload and all-weather landing guidance systems. A research and development program to correlate and integrate the development of all systems and techniques involved in enabling the pilot to fly V/STOL aircraft onto ships and tactical sites is described. Aircraft design parameters that affect its control in the vertical takeoff and landing flight regimes are emphasized. Topics considered include: (1) integrated flight controls and displays; (2) low speed sensor; (3) air traffic control appraoch and landing guidance systems; (4) visual landing aids; (5) ground effect induced thrust variation problems; and (6) handling qualities.

Momiyama, T. S.↗
NASA NTRS1977

Optimal controls for an advanced turbofan engine

Linear optimal control theory is applied to the control synthesis of a high bypass ratio, variable pitch, turbofan engine. The basic control philosophy is to use only a low order dynamic model of the plant coupled with the concept of integral-output states so as to maintain control simplicity yet guarantee integral control of thrust, turbine temperature and other important engine outputs. Linear simulation results indicate that the control system developed provides rapid control of small thrust perturbations and quickly eliminates the effect of unmodelled thrust and temperature disturbances. Large thrust accelerations are obtained in about one half second while the control maintains negligible overshoot in temperature and stall margins.

Slater, G. L.↗
NASA NTRS1979

Flap-lag-torsion flutter analysis of a constant life rotor

The constant lift rotor (CLR) employs a control input of pitch moment to several airfoil sections which are free to pivot on a continuous spar, allowing them to change their pitch to obtain the desired lift. A flap-lag-torsion flutter analysis of a constant lift rotor blade in hover was developed. The blade model assumes rigid body flap and lead-lag motions at the root hinge and each strip undergoes an independent torsional motion. The results are presented in terms of root locus plots of complex eigenvalues as a function of thrust. The effects of several parameters (including structural damping, center of gravity and elastic axis offset from aerodynamic center, compressibility pitch-lag and pitch-flap coupling) on the blade dynamics are examined. With a suitable combination of lag damper and pitch-flap coupling, it is possible to design a constant lift rotor blade free from flutter instability.

Chopra, I.↗
NASA NTRS1980

Computer simulation of engine systems

The use of computerized simulations of the steady state and transient performance of jet engines throughout the flight regime is discussed. In addition, installation effects on thrust and specific fuel consumption is accounted for as well as engine weight, dimensions and cost. The availability throughout the government and industry of analytical methods for calculating these quantities are pointed out.

Fishbach, L. H.↗
NASA NTRS1980

Investigation of axisymmetric and nonaxisymmetric nozzles installed on a 0.10 scale F-18 prototype airplane model

The Langley 16 foot transonic tunnel was used to investigate the afterbody/nozzle longitudinal aerodynamic characteristics of three different two dimensional nozzles and a base-line axisymmetric nozzle installed on a 0.10 scale model of the F-18 airplane. The effects of thrust vectoring and in-flight thrust reversing were also studied. Horizontal-tail deflections of 0 deg, -2 deg, and -5 deg were tested. Test data were obtained at static conditions and at Mach numbers from 0.60 to 1.20 over an angle-of-attack range from -2 deg to 10 deg. Nozzle pressure ratio was varied from jet off to about 10.

Capone, F. J.↗
NASA NTRS1981

Aeropropulsive characteristics of twin nonaxisymmetric vectoring nozzles installed with forward-swept and aft-swept wings

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.

Capone, F. J.↗
NASA NTRS1981

Effect of time-dependent flight loads on turbofan engine performance deterioration

An analytic evaluation of the dynamic effects of two flight load conditions of the JT9D-7/747 propulsion system is conducted. Predicted performance changes associated with a once-per-flight vertical gust and a typical revenue service landing are calculated. The predicted dynamic load effects on thrust specific fuel consumption are found to be negligible. The results indicate that the quasi-steady state approach to flight loads modeling is adequate to investigate the factors important to the deterioration process.

Lewis, B. L.↗
NASA NTRS1983

Effects of varying podded nacelle-nozzle installations on transonic aeropropulsive characteristics of a supersonic fighter aircraft

The aeropropulsive characteristics of an advanced twin engine fighter designed for supersonic cruise was investigated in the 16 foot Transonic Tunnel. The performance characteristics of advanced nonaxisymmetric nozzles installed in various nacelle locations, the effects of thrust induced forces on overall aircraft aerodynamics, the trim characteristics, and the thrust reverser performance were evaluated. The major model variables included nozzle power setting; nozzle duct aspect ratio; forward, mid, and aft nacelle axial locations; inboard and outboard underwing nacelle locations; and underwing and overwing nacelle locations. Thrust vectoring exhaust nozzle configurations included a wedge nozzle, a two dimensional convergent divergent nozzle, and a single expansion ramp nozzle, each with deflection angles up to 30 deg. In addition to the nonaxisymmetric nozzles, an axisymmetric nozzle installation was also tested. The use of a canard for trim was also assessed.

Capone, F. J.↗
NASA NTRS1988

Investigation of difficult component effects on FEM vibration prediction for the AH-1G helicopter

Under the NASA-sponsored Design Analysis Methods for Vibrations program, a series of ground vibration tests and NASTRAN finite element model correlations were conducted on the Bell AH-1G helicopter gunship to investigate the effects of difficult components on the vibration response of the airframe. Secondary structure and damping were found to have significant effects on the frequency response of the airframe above 15 Hz. The nonlinear effects of thrust stiffening and elastomeric mounts on the low-frequency pylon modes below the main rotor were also significant.

Dompka, Robert V.↗
NASA NTRS1989

Investigation of difficult component effects on finite element model vibration prediction for the Bell AH-1G helicopter. Volume 1: Ground vibration test results

Under the NASA-sponsored Design Analysis Methods for VIBrationS (DAMVIBS) program, a series of ground vibration tests and NASTRAN finite element model (FEM) correlations were conducted on the Bell AH-1G helicopter gunship to investigate the effects of difficult components on the vibration response of the airframe. Previous correlations of the AH-1G showed good agreement between NASTRAN and tests through 15 to 20 Hz, but poor agreement in the higher frequency range of 20 to 30 Hz. Thus, this effort emphasized the higher frequency airframe vibration response correlations and identified areas that need further R and T work. To conduct the investigations, selected difficult components (main rotor pylon, secondary structure, nonstructural doors/panels, landing gear, engine, fuel, etc.) were systematically removed to quantify their effects on overall vibratory response of the airframe. The entire effort was planned and documented, and the results reviewed by NASA and industry experts in order to ensure scientific control of the testing, analysis, and correlation exercise. In particular, secondary structure and damping had significant effects on the frequency response of the airframe above 15 Hz. Also, the nonlinear effects of thrust stiffening and elastomer mounts were significant on the low frequency pylon modes below main rotor 1p (5.4 Hz). The results of the ground vibration testing are presented.

Dompka, R. V.↗
NASA NTRS1989

Investigation of difficult component effects on finite element model vibration prediction for the Bell AG-1G helicopter. Volume 2: Correlation results

Under the NASA-sponsored DAMVIBS (Design Analysis Methods for VIBrationS) program, a series of ground vibration tests and NASTRAN finite element model (FEM) correlations were conducted on the Bell AH-1G helicopter gunship to investigate the effects of difficult components on the vibration response of the airframe. Previous correlations of the AG-1G showed good agreement between NASTRAN and tests through 15 to 20 Hz, but poor agreement in the higher frequency range of 20 to 30 Hz. Thus, this effort emphasized the higher frequency airframe vibration response correlations and identified areas that need further R and T work. To conduct the investigations, selected difficult components (main rotor pylon, secondary structure, nonstructural doors/panels, landing gear, engine, furl, etc.) were systematically removed to quantify their effects on overall vibratory response of the airframe. The entire effort was planned and documented, and the results reviewed by NASA and industry experts in order to ensure scientific control of the testing, analysis, and correlation exercise. In particular, secondary structure and damping had significant effects on the frequency response of the airframe above 15 Hz. Also, the nonlinear effects of thrust stiffening and elastomer mounts were significant on the low frequency pylon modes below main rotor 1p (5.4 Hz). The results of the NASTRAN FEM correlations are given.

Dompka, R. V.↗
NASA NTRS1990

A comparison of analytical results for 20 K LOX/hydrogen instabilities

Test data from NASA Lewis' Effect of Thrust Per Element on Combustion Stability Characteristics of Hydrogen-Oxygen Rocket Engines test program are used to validate two recently released stability analysis tools. The first tool is a design methodology called ROCCID (ROCket Combustor Interactive Design). ROCCID is an interactive design and analysis methodology that uses existing performance and combustion stability analysis codes. The second tool is HICCIP (High frequency Injection Coupled Combustion Instability Program). HICCIP is a recently developed combustion stability analysis model. Using a matrix of models, results from analytic comparisons with 20 K LOX/H2 experimental data are presented.

Klem, Mark D.↗