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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 sources NASA NTRS DOE OSTI

NASA NTRS1981

A study of external fuel vaporization

Candidate external vaporizer designs for an aircraft gas turbine engine are evaluated with respect to fuel thermal stability, integration of the vaporizer system into the aircraft engine, engine and vaporizer dynamic response, startup and altitude restart, engine performance, control requirements, safety, and maintenance. The selected concept is shown to offer potential gains in engine performance in terms of reduced specific fuel consumption and improved engine thrust/weight ratio. The thrust/weight improvement can be traded against vaporization system weight.

Szetela, E. J.↗

NASA NTRS1981

Deposit formation in liquid fuels. II - The effect of selected compounds on the storage stability of Jet A turbine fuel

The influence of substituted pyridines, pyrroles, indoles, and quinolines on the storage stability of conventional Jet A turbine fuel is evaluated. Significant increases in the amount of deposit formed in accelerated storage tests are found upon addition of these compounds at levels as low as one ppm nitrogen. While the effect is correlated with basicity of the nitrogen compound within a given compound class, the correlation does not hold between classes (pyridines, quinolines, etc.). Steric hindrance at the nitrogen atom greatly inhibits deposit promotion. The characteristics, but not the elemental composition, of deposits vary with the identity of the added nitrogen compound and with deposition temperature.

Worstell, J. H.↗

NASA NTRS1982

Experimental study of external fuel vaporization

The fuel properties used in the design of a flash vaporization system for aircraft gas turbine engines were evaluated in experiments using a flowing system to determine critical temperature and pressure, boiling points, dew points, heat transfer coefficients, deposit formation rates, and deposit removal. Three fuels were included in the experiments: Jet-A, an experimental referree broad specification fuel, and a premium No. 2 diesel fuel. Engine conditions representing a NASA Energy Efficient Engine at sea-level take-off, cruise, and idle were simulated in the vaporization system and it was found that single phase flow was maintained in the heat exchanger and downstream of the throttle. Deposits encountered in the heat exchanger represented a thermal resistance as high as 1300 sq M K/watt and a deposit formation rate over 1000 gC/sq cm hr.

Szetela, E. J.↗

NASA NTRS1983

Fabrication and quality assurance processes for superhybrid composite fan blades

The feasibility of fabricating full-scale fan blades from superhybrid composites (SHC) for use large, commercial gas turbine engines was evaluated. The type of blade construction selected was a metal-spar/SHC-shell configuration, in which the outer shell was adhesively bonded to a short, internal, titanium spar. Various aspects of blade fabrication, inspection, and quality assurance procedures developed in the investigation are described. It is concluded that the SHC concept is feasible for the fabrication of prototype, full-scale, metal-spar/SHC-shell fan blades that have good structural properties and meet dimensional requirements.

Lark, R. F.↗

NASA NTRS1985

Dynamic stall progress in analysis and prediction

A comprehensive review of research in dynamic stall is presented with applications for helicopters, fighter aircraft, and wind turbines illustrated and evaluated. Emphasis is placed on review of research contributing to better understanding of the dynamic stall mechanism, including influence of type of motion, Mach number, Reynolds number, and three-dimensional effects.

Carr, L. W.↗

NASA NTRS1986

Advanced technology payoffs for future rotorcraft, commuter aircraft, cruise missile, and APU propulsion systems

In connection with the significant advances made regarding the performance of larger gas turbines, challenges arise concerning the improvement of small gas turbine engines in the 250 to 1000 horsepower range. In response to these challenges, the NASA/Army-sponsored Small Engine Component Technology (SECT) study was undertaken with the objective to identify the engine cycle, configuration, and component technology requirements for the substantial performance improvements desired in year-2000 small gas turbine engines. In the context of this objective, an American turbine engine company evaluated engines for four year-2000 applications, including a rotorcraft, a commuter aircraft, a supersonic cruise missile, and an auxiliary power unit (APU). Attention is given to reference missions, reference engines, reference aircraft, year-2000 technology projections, cycle studies, advanced engine selections, and a technology evaluation.

Turk, M. A.↗

NASA NTRS1984

Constitutive modeling for isotropic materials

The unified constitutive theories for application to typical isotropic cast nickel base supperalloys used for air-cooled turbine blades were evaluated. The specific modeling aspects evaluated were: uniaxial, monotonic, cyclic, creep, relaxation, multiaxial, notch, and thermomechanical behavior. Further development of the constitutive theories to model thermal history effects, refinement of the material test procedures, evaluation of coating effects, and verification of the models in an alternate material will be accomplished in a follow-on for this base program.

Ramaswamy, V. G.↗

NASA NTRS1986

Fabrication and quality assurance processes for superhybrid composite fan blades

Lark, R. F.↗

NASA NTRS1959

Performance of Two Boron-Modified S-816 Alloys in a Turbojet Engine Operated at 1650 F

S-816+B and modified S-816+B cast cobalt-base alloys were evaluated as turbine-bucket materials at 16500 F. Stress-rupture and tensile data obtained from these alloys had indicated satisfactory strength for engine operation at 1650 F. Although both alloys exhibited a limited ductility in room-temperature laboratory impact tests, there was a significant increase in impact resistance in the 1650 F tests. Bucket failures began after 10 hours of engine testing and continued at various intervals during the 107.5-hour test. Bucket lives were short relative to the predicted lives based on stress-rupture considerations (280 hr for S-816+B and 1750 hr for modified S-816+B). No significant difference was apparent in the performance of the two alloy groups. The primary cause of bucket failures in both alloys was mechanical fatigue. Impact damage occurred as a direct result of bucket tip fatigue failures and was a secondary cause of bucket failures. The impact of small pieces of fractured bucket tips on surrounding buckets caused a relatively large amount of impact damage to buckets of both alloys. The amount of impact damage from induced fractures at the bucket midspan, which provided relatively large failed fragments, was no greater than that which occurred as a result of tip failures.

Waters, William J.↗

NASA NTRS1999

Study of Boundary Layer Development in a Two-Stage Low-Pressure Turbine

Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical simulations have been performed to study the boundary layer development in a two-stage low-pressure turbine, and to evaluate the transition models available for low Reynolds number flows in turbomachinery. The results of the simulations have been compared with experimental data, including airfoil loadings and integral boundary layer quantities. The predicted unsteady results display similar trends to the experimental data, but significantly overestimate the amplitude of the unsteadiness. The time-averaged results show close agreement with the experimental data.

Dorney, Daniel J.↗

NASA NTRS2007

Transition Models for Engineering Calculations

While future theoretical and conceptual developments may promote a better understanding of the physical processes involved in the latter stages of boundary layer transition, the designers of rotodynamic machinery and other fluid dynamic devices need effective transition models now. This presentation will therefore center around the development of of some transition models which have been developed as design aids to improve the prediction codes used in the performance evaluation of gas turbine blading. All models are based on Narasimba's concentrated breakdown and spot growth.

Fraser, C. J.↗

NASA NTRS2018

Advanced Environmental Barrier Coating and SA Tyrannohex SiC Composites Integration for Improved Thermomechanical and Environmental Durability

The development of 2700 degF capable environmental barrier coating (EBC) systems, particularly, the Rare Earth "Hafnium" Silicon bond coat systems, have significantly improved the temperature capability and environmental stability of SiC/SiC Ceramic Matrix Composite Systems. We have specifically developed the advanced 2700 degF EBC systems, integrating the EBC to the high temperature SA Tyrannohex SiC fiber composites, for comprehensive performance and durability evaluations for potential turbine engine airfoil component applications. The fundamental mechanical properties, environmental stability and thermal gradient cyclic durability performance of the EBC - SA Tyrannohex composites were investigated. The paper will particularly emphasize the high pressure combustion rig recession, cyclic thermal stress resistance and thermomechanical low cycle fatigue testing of uncoated and environmental barrier coated Tyrannohex SiC SA composites in these simulated turbine engine combustion water vapor, thermal gradients, and mechanical loading conditions. We have also investigated high heat flux and flexural fatigue degradation mechanisms, determined the upper limits of operating temperature conditions for the coated SA composite material systems in thermomechanical fatigue conditions. Recent progress has also been made by using the self-healing rare earth-silicon based EBCs, thus enhancing the SA composite hexagonal fiber columns bonding for improved thermomechanical and environmental durability in turbine engine operation environments. More advanced EBC- composite systems based on the new EBC-Fiber Interphases will also be discussed.

Tyrannohex SiC Ceramics↗

DOE OSTI2020

Comparison of loads from HAWC2 and OpenFAST for the IEA Wind 15 MW Reference Wind Turbine

Reference wind turbines (RWTs) that reflect the state-of-the-art of current wind energy technology are necessary in order to properly evaluate innovative methods in wind turbine design and evaluation. The International Energy Agency (IEA) Wind Technology Collaboration Platform (TCP) Task 37 has recently developed a new RWT geared towards offshore floating-foundation applications: the IEA Wind 15 MW. The model has been implemented in two aeroelastic codes, OpenFAST and HAWC2, based on an underlying common ontology. However, these toolchains result in slightly different structural parameters, and the two codes utilise different structural models. Thus, to increase the utility of the model, it is necessary to compare the aeroelastic responses. This paper compares aeroelastic loads calculated using different fidelities of the blade model in OpenFAST (ElastoDyn and BeamDyn) and HAWC2 (prismatic Timoshenko without torsion and Timoshenko with fully populated stiffness matrix), where both codes use the DTU Basic controller and the same turbulence boxes to reduce discrepancies. The aeroelastic responses to steady wind, step wind and turbulent wind (per IEC 61400-1 wind class IB) are considered. The results indicate a generally good agreement between the loads dominated by aerodynamic thrust and force, especially for the no-torsion blade models. Discrepancies were observed in other load channels, partially due to differences in the asymmetric loading of the rotor and partially due to differing closed-loop dynamics, and they will be the subject of future investigations.

17 WIND ENERGY↗

NASA NTRS1992

A critical evaluation of a three-dimensional Navier-Stokes CFD as a tool to design supersonic turbine stages

Three-dimensional flow phenomena in a supersonic turbine blade row were studied numerically to evaluate CFD as a tool to design supersonic turbine stages. The details of the three-dimensional flow structure inside the supersonic turbine blade row and the overall aerodynamic performance at design and off-design conditions are analyzed and the results are compared between the experimental data and the numerical results.

Hah, C.↗

NASA NTRS2008

Fatigue Crack Growth Behavior Evaluation of Grainex Mar-M 247 for NASA's High Temperature, High Speed Turbine Seal Test Rig

The fatigue crack growth behavior of Grainex Mar-M 247 is evaluated for NASA s Turbine Seal Test Facility. The facility is used to test air-to-air seals primarily for use in advanced jet engine applications. Because of extreme seal test conditions of temperature, pressure, and surface speeds, surface cracks may develop over time in the disk bolt holes. An inspection interval is developed to preclude catastrophic disk failure by using experimental fatigue crack growth data. By combining current fatigue crack growth results with previous fatigue strain-life experimental work, an inspection interval is determined for the test disk. The fatigue crack growth life of the NASA disk bolt holes is found to be 367 cycles at a crack depth of 0.501 mm using a factor of 2 on life at maximum operating conditions. Combining this result with previous fatigue strain-life experimental work gives a total fatigue life of 1032 cycles at a crack depth of 0.501 mm. Eddy-current inspections are suggested starting at 665 cycles since eddy current detection thresholds are currently at 0.381 mm. Inspection intervals are recommended every 50 cycles when operated at maximum operating conditions.

Delgado, Irebert R.↗

NASA NTRS2006

Mach 4 Test Results of a Dual-Flowpath, Turbine Based Combined Cycle Inlet

An experimental study was conducted to evaluate the performance of a turbine based combined cycle (TBCC) inlet concept, consisting of a low speed turbojet inlet and high speed dual-mode scramjet inlet. The main objectives of the study were (1) to identify any interactions between the low and the high speed inlets during the mode transition phase in which both inlets are operating simultaneously and (2) to determine the effect of the low speed inlet operation on the performance of the high speed inlet. Tests were conducted at a nominal freestream Mach number of 4 using an 8 percent scale model representing a single module of a TBCC inlet. A flat plate was installed upstream of the model to produce a turbulent boundary layer which simulated the full-scale vehicle forebody boundary layer. A flowmeter/back pressure device, with remote actuation, was attached aft of the high speed inlet isolator to simulate the back pressure resulting from dual-mode scramjet combustion. Results indicate that the inlets did not interact with each other sufficiently to affect inlet operability. Flow spillage resulting from a high speed inlet unstart did not propagate far enough upstream to affect the low speed inlet. Also, a low speed inlet unstart did not cause the high speed inlet to unstart. The low speed inlet improved the performance of the high speed inlet at certain conditions by diverting a portion of the boundary layer generated on the forebody plate.

Albertson, Cindy w.↗

NASA NTRS2013

Advanced Shock Position Control for Mode Transition in a Turbine Based Combined Cycle Engine Inlet Model

A dual flow-path inlet system is being tested to evaluate methodologies for a Turbine Based Combined Cycle (TBCC) propulsion system to perform a controlled inlet mode transition. Prior to experimental testing, simulation models are used to test, debug, and validate potential control algorithms. One simulation package being used for testing is the High Mach Transient Engine Cycle Code simulation, known as HiTECC. This paper discusses the closed loop control system, which utilizes a shock location sensor to improve inlet performance and operability. Even though the shock location feedback has a coarse resolution, the feedback allows for a reduction in steady state error and, in some cases, better performance than with previous proposed pressure ratio based methods. This paper demonstrates the design and benefit with the implementation of a proportional-integral controller, an H-Infinity based controller, and a disturbance observer based controller.

Csank, Jeffrey T.↗

DOE OSTI2022

Evaluation of dynamic testing of full-scale wind turbine drivetrains with hardware-in-the-loop

Dynamometer testing of full-scale wind turbine drivetrains involves subjecting integrated components to extreme static loads, fatigue loads, or dynamic loads to replicate field conditions. This paper provides a detailed evaluation of the uncertainty and errors in applied loads and measured responses, and their magnitude relative to established repeatability bounds for a drivetrain subjected to static and dynamic loads on the 7.5 MW test bench at the Clemson University Wind Turbine Drivetrain Testing Facility. An ideal drivetrain simulation model is utilized to isolate the influence of load tracking errors on test article responses. It is shown that the test article response variations are mainly driven by run out and clearances inherent to the drivetrain. For the dynamic profiles, the load tracking errors are within acceptable limits. Furthermore, a frequency analysis is used to show that the test bench controller tracking performance is acceptable for profiles with frequency content up to 1.5 Hz.

17 WIND ENERGY↗