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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Design and application of electromechanical actuators for deep space missions

This progress report documents research and development efforts performed from August 16, 1993 through February 15, 1994 on NASA Grant NAG8-240, 'Design and Application of Electromechanical Actuators for Deep Space Missions.' Following the executive summary are four report sections: Motor Selection, Tests Stand Development, Health Monitoring and Fault Management, and Experiment Planning. Three specific motor types have been considered as prime movers for TVC EMA applications: the brushless dc motor, the permanent magnet synchronous motor, and the induction motor. The fundamental finding was that, in general, the primary performance issues were energy efficiency and thermal dissipation (rotor heating). In terms of all other issues, the three motor types were found to compare quite equally. Among the design changes made to the test stand since the last progress report is the addition of more mounting holes in the side beams. These additional holes allow the movable end beam to be attached in a greater number of positions than previously. With this change the movable end beam can move from full forward to full back in three inch increments. Specific mathematical details on the approach that have been employed for health monitoring and fault management (HMFM) have been reported previously. This approach is based on and adaptive Kalman filter strategy. In general, a bank of filters can be implemented for each primary fault type. Presently under consideration for the brushless dc machine are the following faults: armature winding open-circuits, armature winding short-circuits (phase-to-phase and phase-to-ground), bearing degradation, and rotor flux weakening. The mechanically oriented experiments include transient loading experiments, transverse loading experiment, friction experiment, motor performance experiment, and HMFM experiment.

Haskew, Tim A.↗
NASA NTRSDate not supplied

Computational Study of Modeling Fully-coupled Combustor-Turbine Interactions by the Open National Combustion Code (OpenNCC)

We investigate the flow fields inside the combustor and the high-pressure turbine including the stator and moving rotors, from the Energy Efficient Engine (E3) program. We then compare the fully-coupled simulations results with the prior results from the sequential approach, where key performance metrics for the combustor and HPT are compared. The results will provide one example of the impact of performing fully-coupled combustor/HPT simulations relative to sequential (one-way coupled) combustor and HPT simulations.

CFD↗
NASA NTRSDate not supplied

Computational Study of Modeling Fully-coupled Combustor-Turbine Interactions by the Open National Combustion Code (OpenNCC)

We investigate the flow fields inside the combustor and the high-pressure turbine including the stator and moving rotors, from the Energy Efficient Engine (E3) program. We then compare the fully-coupled simulations results with the prior results from the sequential approach, where key performance metrics for the combustor and HPT are compared. The results will provide one example of the impact of performing fully-coupled combustor/HPT simulations relative to sequential (one-way coupled) combustor and HPT simulations.

CFD↗
NASA NTRSDate not supplied

Numerical Study of Combustor-Turbine Interactions Using Open-National Combustion Code (OpenNCC)

We investigate the flow fields inside the combustor and the high-pressure turbine including the stator and moving rotors, from the Energy Efficient Engine (E3) program. We then compare the fully-coupled simulations results with the prior results from the sequential approach, where key performance metrics for the combustor and HPT are compared. The results will provide one example of the impact of performing fully-coupled combustor/HPT simulations relative to sequential (one-way coupled) combustor and HPT simulations.

CFD↗
NASA NTRS1981

Reasons for low aerodynamic performance of 13.5-centimeter-tip-diameter aircraft engine starter turbine

The reasons for the low aerodynamic performance of a 13.5 cm tip diameter aircraft engine starter turbine were investigated. Both the stator and the stage were evaluated. Approximately 10 percent improvement in turbine efficiency was obtained when the honeycomb shroud over the rotor blade tips was filled to obtain a solid shroud surface. Efficiency improvements were obtained for three rotor configurations when the shroud was filled. It is suggested that the large loss associated with the open honeycomb shroud is due primarily to energy loss associated with gas transportation as a result of the blade to blade pressure differential at the tip section.

Haas, J. E.↗
NASA NTRS1991

Fluid flow rate control device

A poppet is modulated between closed and full open positions by a brushless DC motor operating magnetically through a housing to drive a permanent magnet rotor which carries the poppet. The rotor is supported on several parallel cables which are stationarily fixed at one end and attached to the rotor at the other end, whereby rotation of the rotor twists the cables, causing axial foreshortening and axial translation of rotor and poppet. Axial translation is enhanced by placing a spacer between the cables, intermediate their ends. A permanent magnet ring is disposed around the valve seat directly axially attracting the rotor to a valve closed position.

Reinicke, Robert H.↗
NASA NTRS2001

Compressor Stall Recovery Through Tip Injection Assessed

Aerodynamic stability is a fundamental limit in the compressor design process. The development of robust techniques for increasing stability has several benefits: enabling higher loading and fewer blades, increasing safety throughout a mission, increasing tolerance to stage mismatch during part-speed operation and speed transients, and providing an opportunity to match stages at the compressor maximum efficiency point, thus reducing fuel burn. Mass injection upstream of the tip of a high-speed axial compressor rotor is a stability enhancement approach known to be effective in suppressing stall in tip-critical rotors if the injection is activated before stall occurs. This approach to stall suppression requires that a reliable stall warning system be available. Tests have recently been performed to assess whether steady injection can also be used to recover from fully developed stall. If mass injection is effective in recovering from stall quickly enough to avoid structural damage or loss of engine power, then a stall warning system may not be required. The stall recovery tests were performed on a transonic compressor rotor at its design tip speed of 1475 ft/sec using four injectors evenly spaced around the compressor case upstream of the rotor. The injectors were connected to an external air source. In an actual engine application, the injected air would be supplied with compressor bleed air. The injectors were isolated from the air source by a fast-acting butterfly valve. With the injectors turned off, the compressor was throttled into stall. Air injection was then activated with no change in throttle setting by opening the butterfly valve. The compressor recovered from stall at a fixed throttle setting with the aid of tip injection. The unsteady operating characteristic of the rotor was measured during these tests using high-response pressure sensors located upstream and downstream of the rotor. The figure shows the results, where the unsteady pressure and mass flow are superimposed on the steady operating characteristic. The total injected mass flow was equal to 1.3 percent of the compressor flow. The solid line with no solid squares on it denotes the operating point during the beginning of throttle closure and the initial drop into stall. The gray traces denote the operating point during an additional throttle closure that occurred over the next 1200 rotor revolutions (4 sec). The dashed line denotes the recovery from stall that occurred during 90 rotor revolutions (0.3 sec) after the injectors were activated with no change in throttle setting. Tip injection not only recovers the compressor from stall, but also restores the compressor to its pre-stall level of pressure rise. In contrast, standard stall recovery schemes such as compressor bleed, stator vane actuation, or engine throttle modulation result in a loss of pressure rise across the compressor, which results in a loss of engine power.

Suder, Ken L.↗
NASA NTRSDate not supplied

Urban Air Mobility: A Control-Centric Approach to Addressing Technical Challenges

Urban Air Mobility (UAM) is an emerging aviation sector and is playing an integral part in the on-demand mobility revolution. UAM is powered by the convergence of advances in distributed electrical propulsion (DEP) and vehicle autonomy. The complexity of operations in the urban environment and the unconventional vehicle configurations designed to take advantage of new propulsion technologies, result in numerous challenges that benefit from a control-centric approach. In this talk we outline some of these challenges and present our current approach to addressing them. For example, in order to achieve full market potential and access to UAM, vehicle autonomous flight is required. A key barrier to autonomous flight in a large multi-agent system is dealing with off-nominal situations and contingencies in a safe and predictable manner. We present our approach to intelligent contingency management, and share recent results and open problems. Additionally, we discuss another major barrier to ubiquitous UAM – the noise signature produced by vehicles with multiple rotors. We present our approach to minimizing such noise within the framework of the acoustically-aware vehicle.

UAM↗
NASA NTRS2002

Room Temperature Characterization of a Magnetic Bearing for Turbomachinery

Open loop, experimental force and power measurements of a three-axis, radial, heteropolar magnetic bearing at room temperature for rotor speeds up to 20,000 RPM are presented in this paper. The bearing, NASA Glenn Research Center's and Texas A&M's third generation high temperature magnetic bearing, was designed to operate in a 1000 F (540 C) environment and was primarily optimized for maximum load capacity. The experimentally measured force produced by one C-core of this bearing was 630 lb. (2.8 kN) at 16 A, while a load of 650 lbs (2.89 kN) was predicted at 16 A using 1D circuit analysis. The maximum predicted radial load for one of the three axes is 1,440 lbs (6.41 kN) at room temperature. The maximum measured load of an axis was 1050 lbs. (4.73 kN). Results of test under rotating conditions showed that rotor speed has a negligible effect on the bearing's load capacity. A single C-core required approximately 70 W of power to generate 300 lb (1.34 kN) of magnetic force. The room temperature data presented was measured after three thermal cycles up to 1000 F (540 C), totaling six hours at elevated temperatures.

Montague, Gerald↗
NASA NTRS1980

An investigation of a stoppable helicopter rotor with circulation control

A stoppable helicopter rotor with circulation control was investigated in the Ames 40 by 80 foot wind tunnel. The model was tested as a rotating wing, a fixed wing, and during transition start/stop sequences. The capability of the model's control system to maintain pitch and roll moment balance during the start/stop sequence, the ability of the blades to withstand the start/stop loads, the adequacy of the control system to maintain balance in the helicopter mode, and the control system capabilities in the fixed-wind mode were assessed. Time-history data of several start/stop sequences of the X-wing rotor, and the steady-state data relating to the model as both a rotor and as a fixed-wing aircraft are presented. In addition, stability data are presented which were acquired during open-loop and closed-loop tests of the hub moment feedback control system.

Ballard, J. D.↗
NASA NTRS1993

Optimal open multistep discretization formulas for real-time simulation

The performance of digital real-time simulations is considered. A figure of merit is derived that quantifies a simulation's fidelity in terms of the time-domain discrepancy between its output and that of the plant it simulates, assuming that the plant is linearizable and asymptotically stable. This performance index is then used in deriving an easily automated procedure for calculating optimal values for free parameters in plant discretizations based on a generalized form of open linear multistep integration formulas. The theory is demonstrated in simulating the rigid-body dynamics of a fully articulated helicopter rotor blade system.

Moerder, Daniel D.↗
NASA NTRS1996

Parameter Design and Optimal Control of an Open Core Flywheel Energy Storage System

In low earth orbit (LEO) satellite applications spacecraft power is provided by photovoltaic cells and batteries. To overcome battery shortcomings the University of Maryland, working in cooperation with NASA/GSFC and NASA/LeRC, has developed a magnetically suspended flywheel for energy storage applications. The system is referred to as an Open Core Composite Flywheel (OCCF) energy storage system. Successful application of flywheel energy storage requires integration of several technologies, viz. bearings, rotor design, motor/generator, power conditioning, and system control. In this paper we present a parameter design method which has been developed for analyzing the linear SISO model of the magnetic bearing controller for the OCCF. The objective of this continued research is to principally analyze the magnetic bearing system for nonlinear effects in order to increase the region of stability, as determined by high speed and large air gap control. This is achieved by four tasks: (1) physical modeling, design, prototyping, and testing of an improved magnetically suspended flywheel energy storage system, (2) identification of problems that limit performance and their corresponding solutions, (3) development of a design methodology for magnetic bearings, and (4) design of an optimal controller for future high speed applications. Both nonlinear SISO and MIMO models of the magnetic system were built to study limit cycle oscillations and power amplifier saturation phenomenon observed in experiments. The nonlinear models include the inductance of EM coils, the power amplifier saturation, and the physical limitation of the flywheel movement as discussed earlier. The control program EASY5 is used to study the nonlinear SISO and MIMO models. Our results have shown that the characteristics and frequency responses of the magnetic bearing system obtained from modeling are comparable to those obtained experimentally. Although magnetic saturation is shown in the bearings, there are good correlations between the theoretical model and experimental data. Both simulation and experiment confirm large variations of the magnetic bearing characteristics due to air gap growth. Therefore, the gap growth effect should be considered in the magnetic bearing system design. Additionally, the magnetic bearing control system will be compared to other design methods using not only parameter design but H-infinity optimal control and mu synthesis.

Pang, D.↗
NASA NTRS2004

Exo-Skeletal Engine: Novel Engine Concept

The exo-skeletal engine concept represents a new radical engine technology with the potential to substantially revolutionize engine design. It is an all-composite drum-rotor engine in which conventionally heavy shafts and discs are eliminated and are replaced by rotating casings that support the blades in spanwise compression. Thus the rotating blades are in compression rather than tension. The resulting open channel at the engine centerline has immense potential for jet noise reduction and can also accommodate an inner combined-cycle thruster such as a ramjet. The exo-skeletal engine is described in some detail with respect to geometry, components, and potential benefits. Initial evaluations and results for drum rotors, bearings, and weights are summarized. Component configuration, assembly plan, and potential fabrication processes are also identified. A finite element model of the assembled engine and its major components is described. Preliminary results obtained thus far show at least a 30-percent reduction of engine weight and about a 10-dB noise reduction, compared with a baseline conventional high-bypass-ratio engine. Potential benefits in all aspects of this engine technology are identified and tabulated. Quantitative assessments of potential benefits are in progress.

Chamis, Cristos C.↗
NASA NTRS2009

Simulated Tip Rub Testing of Low-Density Metal Foam

Preliminary acoustic studies have indicated that low-density, open-cell, metal foams may be suitable acoustic liner material for noise suppression in high by-pass engines. Metal foam response under simulated tip rub conditions was studied to assess whether its durability would be sufficient for the foam to serve both as a rub strip above the rotor as well as an acoustic treatment. Samples represented four metal alloys, nominal cell dimensions ranging from 60 to 120 cells per inch (cpi), and relative densities ranging from 3.4 to 10 percent. The resulting rubbed surfaces were relatively smooth and the open cell structure of the foam was not adversely affected. Sample relative density appeared to have significant influence on the forces induced by the rub event. Acoustic responses of various surface preparations were measured using a normal incidence tube. The results of this study indicate that the foam s open-cell structure was retained after rubbing and that the acoustic absorption spectra variation was minimal.

Bowman, Cheryl L.↗
NASA NTRS2003

Experimental High Temperature Characterization of a Magnetic Bearing for Turbomachinery

Open loop, experimental force and power measurements of a radial, redundant-axis, magnetic bearing at temperatures to 1000 F (538 C) and rotor speeds to 15,000 RPM along with theoretical temperature and force models are presented in this paper. The experimentally measured force produced by a single C-core using 22A was 600 lb. (2.67 kN) at room temperature and 380 lb. (1.69 kN) at 1000 F (538 C). These values were compared with force predictions based on a 1D magnetic circuit analysis and a thermal analysis of gap growth as a function of temperature. Tests under rotating conditions showed that rotor speed has a negligible effect on the bearing s load capacity. One C-core required approximately 340 W of power to generate 190 lb. (8.45 kN) of magnetic force at 1000 F (538 C); however the magnetic air gap was much larger than at room temperature. The data presented is after the bearing had already operated six thermal cycles and eleven total (not consecutive) hours at 1000 F (538 C).

Montague, Gerald↗
NASA NTRS2015

SMART Rotor Wind Tunnel Test Report

The Boeing Company, Mesa Arizona, has been developing smart material actuated rotor technology (SMART) under in-house, DARPA (Defense Advanced Research Projects Agency), NASA and Army funding. A whirl tower test of the SMART active flap rotor system was successfully conducted at the remote test facility (RTF) in Mesa, Arizona, in 2003. Under DARPA and NASA funding, the SMART rotor system was tested in the NASA Ames National Full Scale Aerodynamic Complex (NFAC) 40- by 80-Foot Wind Tunnel in 2008. The DARPA program objectives were to demonstrate the active flap impact on rotor acoustics in forward flight and establish a validation database for noise prediction tools. Under NASA funding, additional wind tunnel tests were conducted, with the objective to demonstrate and quantify vibration, noise, and performance improvements.Wind tunnel testing was successfully and safely concluded, meeting all high priority objectives. The authority, effectiveness, and reliability of the flap actuation system were demonstrated in 65 hours of testing at up to 155 knots and 7,700 pound thrust. Validation data was successfully acquired for four test conditions; blade loads were too high for the high speed condition. The effectiveness of the flap for noise and vibration control was demonstrated conclusively, with results showing significant reductions in BVI (Blade-Vortex Interaction) and in-plane noise as well as vibratory hub loads. The impact of the flap on control power and rotor smoothing was also demonstrated. Data evaluating any benefits in aerodynamic performance and impact on flight controls were acquired, but will need more detailed evaluation. Both open loop control and closed loop feedback control, using continuous time and higher harmonic controllers, were applied.The purpose of the Test Report is to provide a comprehensive document that describes the preparation for and conduct of the wind tunnel test and summarizes the processing and evaluation of wind tunnel test data for the DARPA and the NASA portion of the test. An overview of the wind tunnel test and results can be found in Reference 1. Details on the testing and results for BVI noise, in-plane noise, and vibrations can be found in References 2-4, respectively. These references are four papers, presented at the American Helicopter Society Annual Forum in 2009. A brief description of the delivered electronic data is provided in Reference 5.

Rotor↗
NASA NTRS1987

Results of acoustic tests of a Prop-Fan model

Results of acoustic tests in a low speed open jet anechoic wind tunnel are presented for a counter rotation Prop-Fan model. The model tested had 5 front and 5 rear rotor blades with swept planform. Noise spectra are presented showing the influence of operating and configuration variables such as: (1) power absorption, (2) tip speed, (3) rotor-rotor spacing, (4) power split between the front and rear blade rows, (5) variation of the RPM ratio between front and rear blade rows, (6) tractor versus pusher (pylon effects), and (7) angle of attack. In addition to model scale results, calculated levels derived from test are presented showing the influence of the above variables on Effective Perceived Noise Level of a 13.1 ft diameter Prop-Fan at a flyover distance of 1500 ft. It was found that the strongest effects are caused by tip speed and power absorption. A significant finding was that there is an optimum operating tip speed for minimum noise for a given power absorption. Effects of other parametric variations are generally small but measurable. In order to minimize noise to meet airplane certification limits, operation at moderate tip speeds and power absorption is shown to be desirable. Accuracy of predicted Effective Perceived Noise Level is shown to be good with the best accuracy in the 590 to 670 ft/sec tip speed range.

Metzger, F.B.↗
NASA NTRS1996

Two-Dimensional Computational Model for Wave Rotor Flow Dynamics

A two-dimensional (theta,z) Navier-Stokes solver for multi-port wave rotor flow simulation is described. The finite-volume form of the unsteady thin-layer Navier-Stokes equations are integrated in time on multi-block grids that represent the stationary inlet and outlet ports and the moving rotor passages of the wave rotor. Computed results are compared with three-port wave rotor experimental data. The model is applied to predict the performance of a planned four-port wave rotor experiment. Two-dimensional flow features that reduce machine performance and influence rotor blade and duct wall thermal loads are identified. The performance impact of rounding the inlet port wall, to inhibit separation during passage gradual opening, is assessed.

Welch, Gerard E.↗