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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 487 records · Page 27

All sources NASA NTRS DOE OSTI

NASA NTRS1991

Optimizing aircraft performance with adaptive, integrated flight/propulsion control

The Performance-Seeking Control (PSC) integrated flight/propulsion adaptive control algorithm presented was developed in order to optimize total aircraft performance during steady-state engine operation. The PSC multimode algorithm minimizes fuel consumption at cruise conditions, while maximizing excess thrust during aircraft accelerations, climbs, and dashes, and simultaneously extending engine service life through reduction of fan-driving turbine inlet temperature upon engagement of the extended-life mode. The engine models incorporated by the PSC are continually upgraded, using a Kalman filter to detect anomalous operations. The PSC algorithm will be flight-demonstrated by an F-15 at NASA-Dryden.

Smith, R. H.↗

NASA NTRS1991

Linear quadratic servo control of a reusable rocket engine

A design method for a servo compensator is developed in the frequency domain using singular values. The method is applied to a reusable rocket engine. An intelligent control system for reusable rocket engines was proposed which includes a diagnostic system, a control system, and an intelligent coordinator which determines engine control strategies based on the identified failure modes. The method provides a means of generating various linear multivariable controllers capable of meeting performance and robustness specifications and accommodating failure modes identified by the diagnostic system. Command following with set point control is necessary for engine operation. A Kalman filter reconstructs the state while loop transfer recovery recovers the required degree of robustness while maintaining satisfactory rejection of sensor noise from the command error. The approach is applied to the design of a controller for a rocket engine satisfying performance constraints in the frequency domain. Simulation results demonstrate the performance of the linear design on a nonlinear engine model over all power levels during mainstage operation.

Musgrave, Jeffrey L.↗

NASA NTRS1975

Gas turbine combustor stabilization by heat recirculation

The feasibility of heat recirculation for stabilization of lean mixtures and emission reduction has been studied in detail for a typical aircraft gas turbine combustor. Thermodynamic calculations have indicated temperature and heat recirculation rates for operation of the combustor over a range of combustion zone equivalence ratios and for varying modes of desired engine operation. Calculations indicate the feasibility of stabilizing the combustion zone at equivalence ratios as low as 0.2 with achievable heat recirculation rates. Detailed chemical kinetic calculations suggest that combustor heat release is maintained with reaction completion substantially before the NO forming reactions, even though CO is rapidly oxidized in this same region.

Ganji, A.↗

NASA NTRS1977

Identification and measurement of combustion noise from a turbofan engine using correlation and coherence techniques

Fluctuating pressure measurements within the combustor and tailpipe of a turbofan engine are made simultaneously with far field acoustic measurements. The pressure measurements within the engine are accomplished with cooled semi-infinite waveguide probes utilizing conventional condenser microphones as the transducers. The measurements are taken over a broad range of engine operating conditions and for 16 far field microphone positions between 10 deg and 160 deg relative to the engine inlet axis. Correlation and coherence techniques are used to determine the relative phase and amplitude relationships between the internal pressures and far field acoustic pressures. The results indicate that the combustor is a low frequency source region for acoustic propagation through the tailpipe and out to the far field. Specifically, it is found that the relation between source pressure and the resulting sound pressure involves a 180 deg phase shift. The latter result is obtained by Fourier transforming the cross correlation function between the source pressure and acoustic pressure after removing the propagation delay time. Further, it is found that the transfer function between the source pressure and acoustic pressure has a magnitude approximately proportional to frequency squared. These results are shown to be consistent with a model using a modified source term in Lighthill's turbulence stress tensor, wherein the fluctuating Reynolds stresses are replaced with the pressure fluctuations due to fluctuating entropy.

Karchmer, A. M.↗

NASA NTRS1980

Advanced Technology Spark-Ignition Aircraft Piston Engine Design Study

The advanced technology, spark ignition, aircraft piston engine design study was conducted to determine the improvements that could be made by taking advantage of technology that could reasonably be expected to be made available for an engine intended for production by January 1, 1990. Two engines were proposed to account for levels of technology considered to be moderate risk and high risk. The moderate risk technology engine is a homogeneous charge engine operating on avgas and offers a 40% improvement in transportation efficiency over present designs. The high risk technology engine, with a stratified charge combustion system using kerosene-based jet fuel, projects a 65% improvement in transportation efficiency. Technology enablement program plans are proposed herein to set a timetable for the successful integration of each item of required advanced technology into the engine design.

Stuckas, K. J.↗

NASA NTRS1983

The spark-ignition aircraft piston engine of the future

The advanced technology, spark ignition, aircraft piston engine design study was conducted to determine the improvements that could be made by taking advantage of technology that could reasonably be expected to be made available for an engine intended for production by January 1, 1990. Two engines were proposed to account for levels of technology considered to be moderate risk and high risk. The moderate risk technology engine is a homogeneous charge engine operating on avgas and offers a 40% improvement in transportation efficiency over present designs. The high risk technology engine, with a stratified charge combustion system using kerosene-based jet fuel, projects a 65% improvement in transportation efficiency. Technology enablement program plans are proposed herein to set a timetable for the successful integration of each time of required advanced technology into the engine design.

Stuckas, K. J.↗

NASA NTRS1986

Software engineering environment tool set integration

Space Transportation System Division (STSD) Engineering has a program to promote excellence within the engineering function. This program resulted in a capital funded facility based on a VAX cluster called the Rockwell Operational Engineering System (ROSES). The second phase of a three phase plan to establish an integrated software engineering environment for ROSES is examined. It discusses briefly phase one which establishes the basic capability for a modern software development environment to include a tool set, training and standards. Phase two is a tool set integration. The tool set is primarily off-the-shelf tools acquired through vendors or government agencies (public domain). These tools were placed into categories of software development. These categories are: requirements, design, and construction support; verification and validation support; and software management support. The integration of the tool set is being performed through concept prototyping and development of tools specifically designed to support the life cycle and provide transition from one phase to the next.

Selfridge, William P.↗

NASA NTRS2013

Dynamic Mechanical Analysis (DMA) to Help Characterize Vespel SP-211 Polyimide Material for Use as a 750 F Valve Seal on the Ares I Upper Stage J-2X Engine

DuPont (TM) Vespel (R) SP-211 polyimide was selected as the top candidate seal material for use in the Oxidizer Turbine Bypass Valve (OTBV) on NASA's Ares I Upper Stage J-2X engine. In the OTBV, the seal material would get exposed to temperatures up to 750degF for approx 10 minutes at a time. Although the J-2X engine is not reusable, the valve material could be exposed to multiple temperature cycles up to 750 F during engine operation. The Constellation Program that included the Ares I rocket was eventually cancelled, but the J-2X engine was chosen for continued use for development of NASA's Space Launch System (SLS). The SLS is a heavy-lift launch vehicle that will have capability of taking astronauts and hardware to the Moon, Mars and asteroids. Dynamic mechanical analysis (DMA) was one of several test techniques used to characterize Vespel SP-211 to help prove its worthiness for use on the OTBV of the J-2X engine.

Wingard, Doug↗

NASA NTRS2013

Dynamic Mechanical Analysis (DMA) to Help Characterize Vespel SP-211 Polyimide Material for Use as a 750 F Valve Seal on the Ares I Upper Stage J-2X Engine

DuPont(tm) Vespel(R) SP-211 polyimide was selected as the top candidate seal material for use in the Oxidizer Turbine Bypass Valve (OTBV) on NASA's Ares I Upper Stage J-2X engine. In the OTBV, the seal material would get exposed to temperatures up to 750degF for approx 10 minutes at a time. Although the J-2X engine is not reusable, the valve material could be exposed to multiple temperature cycles up to 750degF during engine operation. The Constellation Program that included the Ares I rocket was eventually cancelled, but the J-2X engine was chosen for continued use for development of NASA's Space Launch System (SLS). The SLS is a heavy-lift launch vehicle that will have capability of taking astronauts and hardware to the Moon, Mars and asteroids. Dynamic mechanical analysis (DMA) was one of several test techniques used to characterize Vespel SP-211 to help prove its worthiness for use on the OTBV of the J-2X engine.

Wingard, Doug↗

DOE OSTI2021

Fuel properties effects on wall-wetting and fuel-in-lube dilution under stochastic pre ignition prone conditions

Fuel-engine interactions have been shown to influence stochastic pre-ignition (SPI), however there is uncertainty on the root causes, participially if effects are primarily physical or chemical in nature. To better delineate the physical and chemical dependencies of fuel properties on SPI, this work studies interactions between aromatics, distillation, and particle matter index on SPI with a laser induced fluorescence (LIF) diagnostic to observe wall wetting. Fuels with high aromatic components or higher distillation temperatures tend to increase SPI events, but it is not well understood if the increased fuel dilution or a chemical aspect of this process is the primary mechanism for SPI. By employing the novel LIF in this work we measure fuel dilution in real-time in a running single cylinder research engine operated at SPI conditions. Three fuels were used in the present work, with the LIF diagnostic. Each fuel was operated at two injection timings, generating fuel specific effects on wall wetting. The LIF measurements are coupled with engine combustion measurements and SPI event counts. Results enable a deconvolution of fuel physical and chemical properties on SPI propensity, providing unique and novel insights into the dominant fuel effects affecting SPI.

Splitter, Derek↗

NASA NTRS2005

Particle Size Distributions Measured in the B757 Engine Plume During EXCAVATE

The Experiment to Characterize Aircraft Volatile Aerosols and Trace Species Emissions (EXCAVATE) took place at NASA Langley Research Center during January 2002. This ground based study was conducted to examine the role of fuel sulfur content on particulate emissions. Size distributions as a function of engine operating conditions were measured in the exhaust plume of a B-757 at four downstream axial locations (1 m, 10 m, 25 m and 35 m). The engine was run on JP-5 with three different sulfur concentrations, 810 ppm, 1050 ppm, 1820 ppm; and was operated over a range of power settings from idle to near-full power. Zalabsky differential-mobility analyzers DMAS), Met One condensation-nuclei counters (CNCs), and a TSI 3022 condensation-particle counter (CPC) were used to measure the size distributions. The total number-count (particle concentration), number-based Emissions Index (EInumber) and mass-based Emissions Index (E1-J increased with fuel sulfur-content and engine pressure ratio (EPR). Count Mean Diameter (Ch4D) also increased with EPR yet remained fairly constant with fuel sulfur-content for a fixed location in the exhaust plume. Also the mode and CMD both increased with distance in the plume.

Sanders, Terry↗

NASA NTRS1982

Improved Stirling engine performance using jet impingement

Of the many factors influencing the performance of a Stirling engine, that of transferring the combustion gas heat into the working fluid is crucial. By utilizing the high heat transfer rates obtainable with a jet impingement heat transfer system, it is possible to reduce the flame temperature required for engine operation. Also, the required amount of heater tube surface area may be reduced, resulting in a decrease in the engine nonswept volume and a related increase in engine efficiency. A jet impingement heat transfer system was designed by Rasor Associates, Inc., and tested in the GPU-3 Stirling engine at the NASA Lewis Research Center. For a small penalty in pumping power (less than 0.5% of engine output) the jet impingement heat transfer system provided a higher combustion-gas-side heat transfer coefficient and a smoothing of heater temperature profiles resulting in lower combustion system temperatures and a 5 to 8% increase in engine power output and efficiency.

Johnson, D. C.↗

NASA NTRS1987

Support of the eight-foot high temperature tunnel modification project

In order to meet the need for propulsion testing in the high supersonic range from Mach 4 to Mach 7, NASA has undertaken the modification of the Langley Eight Foot High Temperature Tunnel to add alternate Mach number capability and oxygen enrichment to allow the testing of operating engines at these Mach numbers and at true temperature tunnel. The transfer of liquid oxygen (LOX) from a storage vessel to a rocket engine generally requires the use of a pressurizing gas at high pressures. Although nitrogen is preferred, unfortunately, when gaseous nitrogen (GN2) is used as the pressurant to transfer liquid oxygen from a storage tank to the tunnel combustor, it contaminates the liquid oxygen and effects a loss of performance in the engine. The contamination of the LOX by the pressurizing GN2 is described, which may prove to be an important operational constraint. It is desirable to have reliable data concerning the penetration of GN2 into LOX during pressurization and the subsequent of self cleaning after blowdown.

Ngo, Kim Chi↗

NASA NTRS1997

Sensor Validation Software

Under a Small Business Innovation Research contract from Lewis Research Center, Expert Microsystems, Inc. developed SureSense, real-time sensor data validation software. This ultra-reliable control and sensing system product was produced through a partnership in 1994 between Expert Microsystems and Intelligent Software Associates, Inc. SureSense was created in response to a NASA need for verifying the reliability of sensor input that operated advanced automation and control systems. The immediate applications included improving the safety and reliability of Space Shuttle Main Engine operations. The company has structured the software to enable application to virtually any process control environment, such as computer integrated manufacturing, power plants, and hazardous gas sensing and control systems.

Source record↗

NASA NTRS2012

Analysis of Buzz in a Supersonic Inlet

A dual-stream, low-boom supersonic inlet designed for use on a small, Mach 1.6 aircraft was tested experimentally in the 8- by 6-Foot Supersonic Wind Tunnel (SWT) at the NASA Glenn Research Center (GRC). The tests showed that the inlet had good recovery and stable operation over large mass flow range. The inlet went into buzz at mass flows well below that needed for engine operation, and the experiments generated a wealth of data during buzz. High frequency response pressure measurements and high-speed schlieren videos were recorded for many buzz events. The objective of the present work was to use computational fluid dynamics (CFD) to predict some of the experimental data taken during buzz, compare those predictions to the experimental data, and to use both datasets to explain the physics of the buzz cycle. The calculations were done with the Wind-US CFD code using a second-order time-accurate differencing scheme and the SST turbulence model. Computed Mach number contours were compared with schlieren images, and ensemble-averaged unsteady pressures were compared to data. The results showed that the buzz cycle consisted partly of spike buzz, an unsteady oscillation of the main shock at the spike tip while the inlet pressure dropped, and partly of choked flow while the inlet repressurized. Most of the results could be explained by theory proposed by Dailey in 1954, but did not support commonly used acoustic resonance explanations.

Chima, Rodrick V.↗

DOE OSTI2021

Determination of a most representative cycle from cylinder pressure ensembles via statistical method using distribution skewness

In internal combustion engine research, cylinder pressure measurements provide valuable information about the underlying thermodynamic and combustion processes, and are typically collected in ensembles of several 100 traces. Although in some particular fields of combustion research all traces are analyzed, in most cases only one trace is studied because analyzing all the traces is impractical due to the large number of collected samples. Instead, an ensemble-averaged pressure trace is commonly calculated and used for analysis. However, this pressure trace is highly smoothed and dynamic information is lost during the averaging process. With the average trace, pressure rise rates are lower and pressure oscillations such as the ones resulting from combustion knock are lost. In this work, a statistical method was developed to determine the “most representative cycle,” which is the cycle from the ensemble that has the pressure trace most representative of the engine operating condition. Eleven characteristic parameters are computed from each pressure trace and probabilistic distributions are obtained for each of the parameters using all the traces in the ensemble. Finally, the most representative cycle is selected by means of a cost function minimization. The benefits of this method are illustrated using experimental data from four very different engine platforms, under four different combustion modes and over a range of operating conditions.

42 ENGINEERING↗

NASA NTRS1994

Mars methane engine

The feasibility of an internal combustion engine operating on a mixture of methane, carbon dioxide, and oxygen has been verified by previous design groups for the Mars Methane Engine Project. Preliminary stoichiometric calculations examined the theoretical fuel-air ratios needed for the combustion of methane. Installation of a computer data acquisition system along with various ancillary components will enable the performance of the engine, running on the described methane mixture, to be optimized with respect to minimizing excess fuel. Theoretical calculations for stoichiometric combustion of methane-oxygen-carbon dioxide mixtures yielded a ratio of 1:2:4.79 for a methane-oxygen-carbon dioxide mixture. Empirical data shows the values to be closer to 1:2.33:3.69 for optimum operation.

Bui, Hung↗

NASA NTRS2015

Progress of a Cross-Correlation Based Optical Strain Measurement Technique for Detecting Radial Growth on a Rotating Disk

The modern turbine engine operates in a harsh environment at high speeds and is repeatedly exposed to combined high mechanical and thermal loads. The cumulative effects of these external forces lead to high stresses and strains on the engine components, such as the rotating turbine disks, which may eventually lead to a catastrophic failure if left undetected. The operating environment makes it difficult to use conventional strain gauges, therefore, non-contact strain measurement techniques is of interest to NASA and the turbine engine community. This presentation describes one such approach; the use of cross correlation analysis to measure strain experienced by the engine turbine disk with the goal of assessing potential faults and damage.

cross-correlation↗