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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Computational Fluid Dynamic Modeling of Rocket Based Combined Cycle Engine Flowfields

Computational Fluid Dynamic techniques are used to study the flowfield of a fixed geometry Rocket Based Combined Cycle engine operating in rocket ejector mode. Heat addition resulting from the combustion of injected fuel causes the subsonic engine flow to choke and go supersonic in the slightly divergent combustor-mixer section. Reacting flow computations are undertaken to predict the characteristics of solutions where the heat addition is determined by the flowfield. Here, adaptive gridding is used to improve resolution in the shear layers. Results show that the sonic speed is reached in the unheated portions of the flow first, while the heated portions become supersonic later. Comparison with results from another code show reasonable agreement. The coupled solutions show that the character of the combustion-based thermal choking phenomenon can be controlled reasonably well such that there is opportunity to optimize the length and expansion ratio of the combustor-mixer.

Daines, Russell L.↗
NASA NTRS1992

HSR combustion analytical research

Increasing the pressure and temperature of the engines of a new generation of supersonic airliners increases the emissions of nitrogen oxides (NO(x)) to a level that would have an adverse impact on the Earth's protective ozone layer. In the process of evolving and implementing low emissions combustor technologies, NASA LeRC has pursued a combustion analysis code program to guide combustor design processes, to identify potential concepts of the greatest promise, and to optimize them at low cost, with short turnaround time. The computational analyses are evaluated at actual engine operating conditions. The approach is to upgrade and apply advanced computer programs for gas turbine applications. Efforts were made in further improving the code capabilities for modeling the physics and the numerical methods of solution. Then test cases and measurements from experiments are used for code validation.

Nguyen, H. Lee↗
NASA NTRS1982

Effect of vacuum exhaust pressure on the performance of MHD ducts at high B-field

The effect of area ratio variation on the performance of a supersonic Hall MHD duct showed that for a given combustion pressure there exists an area ratio below which the power generating region of the duct is shock free and the power output increases linearly with the square of the magnetic field. For area ratios greater than this, a shock forms in the power generating region which moves upstream with increasing magnetic field strength resulting in a less rapid raise in the power output. The shock can be moved downstream by either increasing the combustion pressure or decreasing the exhaust pressure. The influence of these effects upon duct performance is presented in this paper.

Smith, J. M.↗
NASA NTRSDate not supplied

CFD Evaluation Of Sustainable Aviation Fuel Blends for Commercial Supersonics Technology

An overview is provided of a CFD study on the impacts of fuel blends on NOx emissions and flame structure in an axially staged combustor operating at a supersonic cruise condition. The Open version of the National Combustion Code (OpenNCC) was used to perform two-phase reacting flow computations with various blending ratios of an ‘average’ Jet-A (A2) and Gevo Alcohol-to-Jet (C1) for RTRC’s Axially Controlled Stoichiometry (ACS) combustor. The predicted flame structures in the ACS combustor with three different blending ratios of the A2 and C1 fuel were very similar. The predicted NOx emissions for all fuel blends were within 10% of the experimentally measured range of NOx emissions for 100% A2 fuel.

gas turbine combustion↗
NASA NTRSDate not supplied

NASA's Compact High-Efficiency Rotating Detonation Rocket Engine for Mars Interplanetary Missions

NASA has successfully test fired a novel and compact liquid propulsion system known as a Rotating Detonation Rocket Engine. This is a specially designed ring-shaped thrust chamber that leverages additive manufacturing techniques and novel alloys such as GRCop-42 and GRX-810. The extreme combustion event, known as a detonation, reduces the combustion chamber length requirements down to a few inches while equivalent constant pressure rocket thrust chambers are on the order of feet. This is primarily due to rapid completion of combustion by the high-pressure detonation, an order of magnitude faster than deflagration combustion. In addition, the ring shape allows for rapid expansion of the combustion products. Depending on the thrust class and design supersonic area ratio, the full RDRE can be anywhere from 10% to 50% shorter than a traditional liquid rocket assuming the same exit diameter but is dependent on a number of design assumptions. This may enable substantial mass savings, cost savings, and broader design trade space for various mission architectures. Finally, the engine system has potential for higher Isp at identical average chamber pressure, which is currently being assessed by NASA. Experimental data obtained from testing in 2022 identified the feasibility of the novel propulsion system while multiple test series scheduled throughout 2023 and 2024 target closing the remaining critical technical gaps preventing widespread use of the technology amongst industry.

Thomas Teasley↗
NASA NTRS2006

Evaporating Spray in Supersonic Streams Including Turbulence Effects

Evaporating spray plays an important role in spray combustion processes. This paper describes the development of a new finite-conductivity evaporation model, based on the two-temperature film theory, for two-phase numerical simulation using Eulerian-Lagrangian method. The model is a natural extension of the T-blob/T-TAB atomization/spray model which supplies the turbulence characteristics for estimating effective thermal diffusivity within the droplet phase. Both one-way and two-way coupled calculations were performed to investigate the performance of this model. Validation results indicate the superiority of the finite-conductivity model in low speed parallel flow evaporating sprays. High speed cross flow spray results indicate the effectiveness of the T-blob/T-TAB model and point to the needed improvements in high speed evaporating spray modeling.

Balasubramanyam, M. S.↗
NASA NTRS1974

Analytical chemical kinetic investigation of the effects of oxygen, hydrogen, and hydroxyl radicals on hydrogen-air combustion

Quantitative values were computed which show the effects of the presence of small amounts of oxygen, hydrogen, and hydroxyl radicals on the finite-rate chemical kinetics of premixed hydrogen-air mixtures undergoing isobaric autoignition and combustion. The free radicals were considered to be initially present in hydrogen-air mixtures at equivalence ratios of 0.2, 0.6, 1.0, and 1.2. Initial mixture temperatures were 1100 K, 1200 K, and 1500 K, and pressures were 0.5, 1.0, 2.0, and 4.0 atm. Of the radicals investigated, atomic oxygen was found to be the most effective for reducing induction time, defined as the time to 5 percent of the total combustion temperature rise. The reaction time, the time between 5 percent and 95 percent of the temperature rise, is not decreased by the presence of free radicals in the initial hydrogen-air mixture. Fuel additives which yield free radicals might be used to effect a compact supersonic combustor design for efficient operation in an otherwise reaction-limited combustion regime.

Carson, G. T., Jr.↗
NASA NTRS1974

Heat conduction controlled combustion for scramjet applications

The use of heat conduction flame generated in a premixed supersonic stream is discussed. It is shown that the flame is controlled initially by heat conduction and then by chemical reaction. Such a flame is shorter than the diffusion type of flame and therefore it requires a much shorter burner. The mixing is obtained by injecting the hydrogen in the inlet. Then the inlet can be cooled by film cooling.

Ferri, A.↗
NASA NTRS1987

A subsonic to Mach 5.5 subscale engine test facility

The NASA-Langley Mach 4 facility, in which air-hydrogen combustion is used to heat the test gas, was modified to make the facility suitable for tests of ramjet-type models at subsonic and transonic, as well as supersonic, Mach numbers. The construction details and the instrumentation of this facility, designated the Combustion-Heated Scramjet Test Facility, are described, and modifications to enhance the test capability range from the subsonic/transonic and Mach 3.5 to 5.5 are discussed. Design diagrams and test result graphs are included.

Andrews, Earl H., Jr.↗
DOE OSTI2019

Tetrafluoroethylene as a fuel component for an atomic fluorine generator of a supersonic continuous-wave chemical HF laser

A cheap and widely accessible combination (one of non-saturated perfluorocarbons), i.e. C{sub 2}F{sub 4} tetrafluoroethylene, is proposed as an alternative fuel component for an atomic fluorine generator of a supersonic cw chemical HF laser of self-contained type. Combustion products of the hypergolic F{sub 2} – C{sub 2}F{sub 4} – He mixture do not contain active relaxants of vibrationally excited HF(v) molecules. According to estimates, the atomic fluorine yield under comparable conditions is about 70 % in relation to that of the atomic fluorine generator operating on the F{sub 2} – D{sub 2} – He mixture which is the ‘basic’ one for a HF laser. The specific power is reduced by 23 % with an improvement in a set of the fuel performance and a significant reduction in the cost of triggering the laser in the course of its bench tests. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1975

Some effects of combustion on turbulent mixing

Mixing and combustion of near-sonic central hydrogen jets and coaxial supersonic air or nitrogen streams are discussed. Results of concentration measurements in these flows are presented.

Bangert, L. H.↗
NASA NTRS1986

Progress in the development of parabolized Navier-Stokes (PNS) methodology for analyzing propulsive jet mixing problems

A brief review of 2D PNS methodology is first presented which describes the specialized features of supersonic shock-capturing and subsonic pressure-split models required for the analysis of aircraft, rocket and scramjet jet mixing problems. These features include techniques for dealing with various types of embedded and interfacing subsonic regions, the inclusion of finite-rate chemistry and the direct-coupling with potential flow solutions. Preliminary 3D extensions of this PNS methodology geared to supersonic and subsonic rectangular free jet mixing problems are also reviewed. New 3D PNS work will be described which includes the development of a hybrid supersonic/subsonic free jet mixing model, and, a supersonic model geared to the analysis of turbulent mixing and combustion processes occurring in scramjet combustor/nozzle flowfields.

Dash, S. M.↗
NASA NTRS1993

Fuels and Combustion Technology for Advanced Aircraft Engines [Les Propergols et les Systèmes de Combustion pour les Moteurs d'Aéronefs]

The Conference Proceedings contains the 38 papers presented at the Propulsion and Energetics Panel 81st Symposium on "Fuels and Combustion Technology for Advanced Aircraft Engines" which was held from 10th-14th May 1993, in Fiuggi, Italy. The Technical Evaluation Report and the Keynote Address are included at the beginning, and discussions follow most papers. The Symposium was arranged in the following Sessions: Technology Overview Papers (2); Modelling: Pollutant Formation (4); Modelling: Combustor Design (5); High Temperature Fuels and Fuel Systems (6); Combustion Research: Performance (6); Combustion Research: Emissions (5); Fuel Atomization: Diagnostics and Modelling (5); and Combustion Research: Flowfleld and Mixing (4). The last paper is a contribution from Russia not allocated to a session. New technologies for low NOx combustors and advanced high-pressure/high temperature cycle engines result in unique problems in design and performance. There have been significant advances in modelling and diagnostics to aid the development of these technologies. The purpose of the Symposium was to bring together experts from industry, research establishments and universities to discuss fundamental and applied research in these areas as relevant to the development of advanced gas turbine engines, to exchange practical experience and to discuss the state of the art.

Fuels for aircraft↗
NASA NTRS2005

Large Engine Technology Program. Task 22: Variable Geometry Concepts for Rich-Quench-Lean Combustors

The objective of the task reported herein was to define, evaluate, and optimize variable geometry concepts suitable for use with a Rich-Quench-Lean (RQL) combustor. The specific intent was to identify approaches that would satisfy High Speed Civil Transport (HSCT) cycle operational requirements with regard to fuel-air ratio turndown capability, ignition, and stability margin without compromising the stringent emissions, performance, and reliability goals that this combustor would have to achieve. Four potential configurations were identified and three of these were refined and tested in a high-pressure modular RQL combustor rig. The tools used in the evolution of these concepts included models built with rapid fabrication techniques that were tested for airflow characteristics to confirm sizing and airflow management capability, spray patternation, and atomization characterization tests of these models and studies that were supported by Computational Fluid Dynamics analyses. Combustion tests were performed with each of the concepts at supersonic cruise conditions and at other critical conditions in the flight envelope, including the transition points of the variable geometry system, to identify performance, emissions, and operability impacts. Based upon the cold flow characterization, emissions results, acoustic behavior observed during the tests and consideration of mechanical, reliability, and implementation issues, the tri-swirler configuration was selected as the best variable geometry concept for incorporation in the RQL combustor evolution efforts for the HSCT.

Tacina, Robert R.↗
NASA NTRS1990

Comparisons of a Three-Dimensional, Full Navier Stokes Computer Model with High Mach Number Combuster Test Data

Comparisons between scramjet combustor data and a three-dimensional full Navier-Stokes calculation have been made to verify and substantiate computational fluid dynamics (CFD) codes and application procedures. High Mach number scramjet combustor development will rely heavily on CFD applications to provide wind tunnel-equivalent data of quality sufficient to design, build and fly hypersonic aircraft. Therefore. detailed comparisons between CFD results and test data are imperative. An experimental case is presented, for which combustor wall static pressures were measured and flow-fieid interferograms were obtained. A computer model was done of the experiment, and counterpart parameters are compared with experiment. The experiment involved a subscale combustor designed and fabricated for the National Aero-Space Plane Program, and tested in the Calspan Corporation 96" hypersonic shock tunnel. The combustor inlet ramp was inclined at a 20 angle to the shock tunnel nozzle axis, and resulting combustor entrance flow conditions simulated freestream M=10. The combustor body and cowl walls were instrumented with static pressure transducers, and the combustor lateral walls contained windows through which flowfield holographic interferograms were obtained. The CFD calculation involved a three-dimensional time-averaged full Navier-Stokes code applied to the axial flow segment containing fuel injection and combustion. The full Navier-Stokes approach allowed for mixed supersonic and subsonic flow, downstream-upstream communication in subsonic flow regions, and effects of adverse pressure gradients. The code included hydrogen-air chemistry in the combustor segment which begins near fuel injection and continues through combustor exhaust. Combustor ramp and inlet segments on the combustor lateral centerline were modelled as two dimensional. Comparisons to be shown include calculated versus measured wall static pressures as functions of axial flow coordinate, and calculated path-averaged density contours versus an holographic Interferogram.

Watkins, William B.↗
NASA NTRS1991

The 3D computation of single-expansion-ramp and scramjet nozzles

A description of the computations for three-dimensional nonaxisymmetric nozzles and an analysis of the flowfields are presented. Two different types of nozzles are investigated for compressible flows at high Reynolds numbers. These are the single-expansion-ramp and scramjet nozzles. The computation for the single-expansion-ramp nozzle focuses on the condition of low pressure ratio, which requires the simulation for turbulent flow that is not needed at high pressure ratios. The flowfield contains the external quiescent air, and the internal regions of subsonic and low supersonic flows. The second type is the scramjet nozzle, which typically has a very large area ratio and is designed to operate at high speeds and pressure ratios. The freestream external flow has a Mach number of 6, and the internal flow leaving the combustion chamber is at a Mach number of 1.62. The flowfield is mostly supersonic except in the viscous region near walls. The computed results from both cases are compared with experimental data for the surface pressure distributions.

Lai, H. T.↗