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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

An analysis of cross-coupling of a multicomponent jet engine test stand using finite element modeling techniques

A two axis thrust measuring system was analyzed by using a finite a element computer program to determine the sensitivities of the thrust vectoring nozzle system to misalignment of the load cells and applied loads, and the stiffness of the structural members. Three models were evaluated: (1) the basic measuring element and its internal calibration load cells; (2) the basic measuring element and its external load calibration equipment; and (3) the basic measuring element, external calibration load frame and the altitude facility support structure. Alignment of calibration loads was the greatest source of error for multiaxis thrust measuring systems. Uniform increases or decreases in stiffness of the members, which might be caused by the selection of the materials, have little effect on the accuracy of the measurements. It is found that the POLO-FINITE program is a viable tool for designing and analyzing multiaxis thrust measurement systems. The response of the test stand to step inputs that might be encountered with thrust vectoring tests was determined. The dynamic analysis show a potential problem for measuring the dynamic response characteristics of thrust vectoring systems because of the inherently light damping of the test stand.

Schweikhard, W. G.↗
NASA NTRS1984

On optimal design for the blade-root/hub interface in jet engines

Two major problems identified with the design of the blade-root/hub interface are discussed. The first is the so-called friction contact problem which has two special features: unilateral contact and Coulomb's friction. One of the difficulties in this problem is that the portions of contact and sticking/sliding surfaces are not known a priori. The second is the shape optimization problem which is characterized either by the minimization of the maximum contact pressure or by the minimization of the equivalent stress on the boundary. Design variables are the shapes of the blade-root and the hub. It is noted that friction contact and shape optimization problems are strongly coupled in the present design problem.

Kikuchi, N.↗
NASA NTRS1987

Liquid Engine Jet Atomization Workshop report

The workshop was oriented to disclose information and unsettled problems to understand the fundamental physical mechanism of the droplet formation process. Based on presentation and discussion of results, recommendations were made which should lead to associated future activities. To accomplish this task, existing observations and experiments, contributing to the basic knowledge, providing data for analytical concept verification, and forming a basis for empirical correlations were solicited. Advanced analytical modeling methods or results from specific studies were requested as well as the experience and advice from injector designers. All effort is directed to advance current analytical techniques, simulating the flow behavior downstream of the injection elements in a liquid rocket combustion chamber. Such a tool can be used to optimize injector designs with respect to short length weight savings, wall material protection, or large heat energy transport to a regenerative cooling fluid, while simultaneously achieving the maximum specific impulse in performance. The liquid atomization process also forms a sound basis for combustion instability analysis.

Gross, Klaus W.↗
NASA NTRS1988

Sensor failure detection for jet engines

The use of analytical redundancy to improve gas turbine engine control system reliability through sensor failure detection, isolation, and accommodation is surveyed. Both the theoretical and application papers that form the technology base of turbine engine analytical redundancy research are discussed. Also, several important application efforts are reviewed. An assessment of the state-of-the-art in analytical redundancy technology is given.

Merrill, Walter C.↗
NASA NTRS1989

The determination of third order linear models from a seventh order nonlinear jet engine model

Results are presented that demonstrate how good reduced-order models can be obtained directly by recursive parameter identification using input/output (I/O) data of high-order nonlinear systems. Three different methods of obtaining a third-order linear model from a seventh-order nonlinear turbojet engine model are compared. The first method is to obtain a linear model from the original model and then reduce the linear model by standard reduction techniques such as residualization and balancing. The second method is to identify directly a third-order linear model by recursive least-squares parameter estimation using I/O data of the original model. The third method is to obtain a reduced-order model from the original model and then linearize the reduced model. Frequency responses are used as the performance measure to evaluate the reduced models. The reduced-order models along with their Bode plots are presented for comparison purposes.

Lalonde, Rick J.↗
NASA NTRS1990

Sensor failure detection for jet engines

The use of analytical redundancy to improve gas turbine engine control system reliability through sensor failure detection, isolation, and accommodation is surveyed. Both the theoretical and application papers that form the technology base of turbine engine analytical redundancy research are discussed. Also, several important application efforts are reviewed. An assessment of the state-of-the-art in analytical redundancy technology is given.

Merrill, Walter C.↗
NASA NTRS1992

Computer Jet-Engine-Monitoring System

"Intelligent Computer Assistant for Engine Monitoring" (ICAEM), computer-based monitoring system intended to distill and display data on conditions of operation of two turbofan engines of F-18, is in preliminary state of development. System reduces burden on propulsion engineer by providing single display of summary information on statuses of engines and alerting engineer to anomalous conditions. Effective use of prior engine-monitoring system requires continuous attention to multiple displays.

Disbrow, James D.↗
NASA NTRS1990

Large-scale wind tunnel studies of a jet-engined powered ejector-lift STOVL aircraft

A full-scale model of a supersonic STOVL single engine flighter aircraft employing an ejector to augment lift in hover and in low-speed flight was tested in the 40- by 80-ft and 80- by 120-ft test sections of the National Full-Scale Aerodynamics Complex located at the NASA Ames Research Center. The measured ejector augmentation ratio in hover met the design requirement of 1.6 and continued to provide the lift necessary in forward flight for good transition qualities. The up-and-away aerodynamics (ejector system stowed) were found to be conventional for this class of vehicle. The pitch control provided by the full-span blown flaps is sufficient to control the large pitching moments generated by ventral exhaust nozzle vectoring and propulsion induced aerodynamic effects such as the turning of the flow entrained into the ejectors.

Dudley, Michael R.↗
NASA NTRS1993

Effect of jet engine exhaust on SOFIA straylight performance

The Stratospheric Observatory For Infrared Astronomy (SOFIA) is being designed at NASA's Ames Research Center as a replacement for the Kuiper Airborne Observatory (KAO). A 2.5-m Nasmyth telescope will be mounted in a Boeing 747 SP and flown at 41,000 ft, above most of the H2O in the earth's atmosphere. In the original SOFIA design, the telescope is located in front of the wings, as it is in the KAO. An alternative design with the telescope placed behind the wings is being studied as part of an effort to reduce cost and weight. In this location, the emission from the engines and the hot H2O molecules in the exhaust become significant straylight sources. The engines and exhaust radiate into the telescope cavity, and illuminate the primary and tertiary mirrors at low telescope elevation angles. The APART/PADE program was used to analyze the straylight at the SOFIA focal plane as a function of wavelength and telescope elevation angle. The emission from the engines and exhaust gas is compared to that from the earth and the telescope itself. Based on the results of this analysis, the SOFIA telescope has been moved behind the wings.

St. Clair Dinger, Ann↗