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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

A numerical study of mixing and combustion in hypervelocity flows through a scramjet combustor model

Interest in high speed, air-breathing propulsion systems such as scramjets has revived in recent years fueled to a large extent by the National Aerospace Plane (NASP) program. These vehicles are expected to fly trans-atmospheric and as a consequence, the Mach number level within the engine/combustor would be rather high (M greater than 5). Ground based testing of such scramjet engines requires a facility that can not only achieve the right Mach number, but also have the proper pressures and temperatures to simulate the combustion processes. At present, only pulse type facilities can provide such high enthalpy flows. The newest of these is the free-piston shock tunnel, T5 located at GALCIT. Recently, a generic combustor model was tested in T5, and the experimental data from that study is analyzed in the present report. The available experimental data from T5 are essentially the static pressures on the injection wall and the one opposite to it. Thus, a principal aim of the present study was to validate the available experimental data by using a proven CFD tool and then investigate the performance characteristics of the combustor model, such as, the mixing efficiency and combustion efficiency. For this purpose, in this study, the code GASP has been used.

Krishamurthy, Ramesh↗
NASA NTRS2002

Laboratory Studies of the Optical Properties and Condensation Processes of Cosmic Dust Particles

A laboratory facility for levitating single isolated dust particles in an electrodynamics balance has been developing at NASA/Marshall Space Flight Center for conducting a variety of experimental, of astrophysical interest. The objective of this research is to employ this innovative experimental technique for studies of the physical and optical properties of the analogs of cosmic grains of 0.2-10 micron size in a chamber with controlled pressure/temperatures simulating astrophysical environments. In particular, we will carry out three classes of experiments to investigate the microphysics of the analogs of interstellar and interplanetary dust grains. (1) Charge characteristics of micron size single dust grains to determine the photoelectric efficiencies, yields, and equilibrium potentials when exposed to UV radiation. These measurements will provide the much-needed photoelectric emission data relating to individual particles as opposed to that for the bulk materials available so far. (2) Infrared optical properties of dust particles obtained by irradiating the particles with radiation from tunable infrared diode lasers and measuring the scattered radiation. Specifically, the complex refractive indices, the extinction coefficients, the scattering phase functions, and the polarization properties of single dust grains of interest in interstellar environments, in the 1-25 micron spectral region will be determined. (3) Condensation experiments to investigate the deposition of volatile gases on colder nucleated particles in dense interstellar clouds and lower planetary atmospheres. The increase in the mass or m/q ratio due to condensation on the particle will be monitored as a function of the dust particle temperature and the partial pressure of the injected volatile gas. The measured data wild permit determination of the sticking efficiencies of volatile gases of astrophysical interest. Preliminary results based on photoelectric emission experiments on 0.2-6.6 micron size silica particles exposed to UV radiation in the 120-200 nm spectral region will be presented.

Abbas, Mian M.↗
NASA NTRS2004

[Predicting Spectra of Accretion Disks Around Galactic Black Holes]

The purpose of this grant was to construct detailed atmosphere solutions in order to predict the spectra of accretion disks around Galactic black holes. Our plan of action was to take an existing disk atmosphere code (TLUSTY, created by Ivan Hubeny) and introduce those additional physical processes necessary to make it applicable to disks of this variety. These modifications include: treating Comptonization; introducing continuous opacity due to heavy elements; incorporating line opacity due to heavy elements; adopting a disk structure that reflects readjustments due to radiation pressure effects; and injecting heat via a physically-plausible vertical distribution.

Krolik, Julian H.↗
NASA NTRS1950

Performance of J33-A-27 Turbojet-Engine Compressor: Over-All Performance Characteristics of Modified Compressor with Water Injection at Design Equivalent Speed of 11,800 RPM - III

An investigation was conducted to determine the effects of water injection on the over-all performance of a modified J33-A-27 turbojet-engine compressor at the design equivalent speed of 11,800 rpm. The water-air ratio by weight was 0.05. With water injection the peak pressure ratio increased 9.0 per- cent, the maximum efficiency decreased 15 percent (actual numerical difference 0.12), and. the maximum total weight flow increased 9.3 percent.

Withee, Joseph R., Jr.↗
NASA NTRS2006

Use, Assessment, and Improvement of the Loci-CHEM CFD Code for Simulation of Combustion in a Single Element GO2/GH2 Injector and Chamber

This document is a viewgraph presentation of a paper that documents a continuing effort at Marshall Space Flight Center (MSFC) to use, assess, and continually improve CFD codes to the point of material utility in the design of rocket engine combustion devices. This paper describes how the code is presently being used to simulate combustion in a single element combustion chamber with shear coaxial injectors using gaseous oxygen and gaseous hydrogen propellants. The ultimate purpose of the efforts documented is to assess and further improve the Loci-CHEM code and the implementation of it. Single element shear coaxial injectors were tested as part of the Staged Combustion Injector Technology (SCIT) program, where detailed chamber wall heat fluxes were measured. Data was taken over a range of chamber pressures for propellants injected at both ambient and elevated temperatures. Several test cases are simulated as part of the effort to demonstrate use of the Loci-CHEM CFD code and to enable us to make improvements in the code as needed. The simulations presented also include a grid independence study on hybrid grids. Several two-equation eddy viscosity low Reynolds number turbulence models are also evaluated as part of the study. All calculations are presented with a comparison to the experimental data. Weaknesses of the code relative to test data are discussed and continuing efforts to improve the code are presented.

Westra, Douglas G.↗
NASA NTRS2010

In-Line Capacitance Sensor for Real-Time Water Absorption Measurements

A capacitance/dielectric sensor was designed, constructed, and used to measure in real time the in-situ water concentration in a desiccant water bed. Measurements were carried out with two experimental setups: (1) passing nitrogen through a humidity generator and allowing the gas stream to become saturated at a measured temperature and pressure, and (2) injecting water via a syringe pump into a nitrogen stream. Both water vapor generating devices were attached to a downstream vertically-mounted water capture bed filled with 19.5 g of Moisture Gone desiccant. The sensor consisted of two electrodes: (1) a 1/8" dia stainless steel rod placed in the middle of the bed and (2) the outer shell of the stainless steel bed concentric with the rod. All phases of the water capture process (background, heating, absorption, desorption, and cooling) were monitored with capacitance. The measured capacitance was found to vary linearly with the water content in the bed at frequencies above 100 kHz indicating dipolar motion dominated the signal; below this frequency, ionic motion caused nonlinearities in the water concentration/capacitance relationship. The desiccant exhibited a dielectric relaxation whose activation energy was lowered upon addition of water indicating either a less hindered rotational motion or crystal reorientation.

Nurge, Mark A.↗
NASA NTRS2013

Effects of Gravity on Supercritical Water Oxidation (SCWO) Processes

The effects of gravity on the fluid mechanics of supercritical water jets are being studied at NASA to develop a better understanding of flow behaviors for purposes of advancing supercritical water oxidation (SCWO) technologies for applications in reduced gravity environments. These studies provide guidance for the development of future SCWO experiments in new experimental platforms that will extend the current operational range of the DECLIC (Device for the Study of Critical Liquids and Crystallization) Facility on board the International Space Station (ISS). The hydrodynamics of supercritical fluid jets is one of the basic unit processes of a SCWO reactor. These hydrodynamics are often complicated by significant changes in the thermo-physical properties that govern flow behavior (e.g., viscosity, thermal conductivity, specific heat, compressibility, etc), particularly when fluids transition from sub-critical to supercritical conditions. Experiments were conducted in a 150 ml reactor cell under constant pressure with water injections at various flow rates. Flow configurations included supercritical jets injected into either sub-critical or supercritical water. Profound gravitational influences were observed, particularly in the transition to turbulence, for the flow conditions under study. These results will be presented and the parameters of the flow that control jet behavior will be examined and discussed.

aqueous solutions↗
NASA NTRS2022

2019 ARIA Proposal Final Report Public Abstract: What Happens to Life in an Ocean World Plume?

The NASA Cassini mission to Saturn discovered persistent jets of water being ejected into space from a subsurface ocean on the small moon Enceladus and evidence that this ocean is habitable for life. The ice resulting from these plumes forms the E Ring of Saturn. Missions are under study to fly through these plumes and collect and analyze samples to look for evidence of life. To support design and instrument selection for these missions, there is a critical need to understand what happens to microbial life adapted to a liquid environment when suddenly ejected into the vacuum of space. We experimentally determined the structural changes in microbial cells in liquid medium when ejected into vacuum. We first developed a vacuum chamber fitted with a feedthrough and nozzle allowing fluid to be injected into vacuum. The nozzle dispersed the fluid into micron-sized droplets. Fluid containing a population of E. Coli microbes was injected into the chamber and droplets were collected on microscope slides and small cups for imaging with a Scanning Electron Microscope (SEM). Epifluorescence microscopy, using a lipid stain, and SEM imaging were used to evaluate the cellular integrity of E. coli after injection through the pressurized nozzle into vacuum. The experimental samples showed a 94% decrease in visible intact E. coli cells as compared with control samples but showed a fluorescent residue in the shape of the sublimated droplets that indicated the presence of lipids. E. coli was selected for testing although other cell types could vary physiologically which could affect their response to a vacuum environment. More testing is needed to determine whether other types of microbial cells can survive the plume environment. However, these results suggest that lipids may be directly detectable evidence of life in icy world plumes, but organisms are unlikely to survive due to disruption of their cell walls.

C. R. Stoker↗
NASA NTRS1990

Pressure and current balance conditions during electron beam injections from spacecraft

Electrostatic charging level of a conducting surface in response to injections of electron beams into space plasma is investigated by means of one-dimensional Vlasov code. Injections of Maxwellian beams into a vacuum shows that the surface can charge up to an electric potential phi sub s greater than W sub b, where W sub b is the average electron beam energy. Since Maxwellian beams have extended trails with electrons having energies greater than W sub b, it is difficult to quantify the charging level in terms of the energies of the injected electrons. In order to quantitatively understand the charging in excess of W sub b, simulations were carried out for water-bag types of beam with velocity distribution functions described by f(V) = A for V sub min approx. less than V approx. less than V sub max and f(V) = O otherwise, where A is a constant making the normalized beam density unity. It is found that V sub max does not directly determine the charging level. The pressure distribution in the electron sheath determines the electric field distribution near the surface. The electric field in turn determines the electrostatic potential of the vehicle. The pressure distribution is determined by the beam parameters such as the average beam velocity and the velocity spread of the beam.

Hwang, K. S.↗
NASA NTRS1992

Tangential-Entry Injector With Internal Reed Valve

Liquid-spray-injecting device provides designed pressure drop versus rate of flow to help meter flow. Includes cylinder with tangential entry slots and internal reed valve. Tangential entry imparts swirling motion to liquid, resulting in finely atomized liquid spray. Reeds vary flow areas of entry slots by deflecting in response to pressure of liquid. Variation alters pressure-versus-flow characteristic. Device used to provide wide range of throttleability for liquid fuel injected into combustion chamber or engine.

Cox, George B., Jr.↗
NASA NTRS2004

Parametric Studies of Flow Separation using Air Injection

Boundary Layer separation causes the airfoil to stall and therefore imposes dramatic performance degradation on the airfoil. In recent years, flow separation control has been one of the active research areas in the field of aerodynamics due to its promising performance improvements on the lifting device. These active flow separation control techniques include steady and unsteady air injection as well as suction on the airfoil surface etc. This paper will be focusing on the steady and unsteady air injection on the airfoil. Although wind tunnel experiments revealed that the performance improvements on the airfoil using injection techniques, the details of how the key variables such as air injection slot geometry and air injection angle etc impact the effectiveness of flow separation control via air injection has not been studied. A parametric study of both steady and unsteady air injection active flow control will be the main objective for this summer. For steady injection, the key variables include the slot geometry, orientation, spacing, air injection velocity as well as the injection angle. For unsteady injection, the injection frequency will also be investigated. Key metrics such as lift coefficient, drag coefficient, total pressure loss and total injection mass will be used to measure the effectiveness of the control technique. A design of experiments using the Box-Behnken Design is set up in order to determine how each of the variables affects each of the key metrics. Design of experiment is used so that the number of experimental runs will be at minimum and still be able to predict which variables are the key contributors to the responses. The experiments will then be conducted in the 1ft by 1ft wind tunnel according to the design of experiment settings. The data obtained from the experiments will be imported into JMP, statistical software, to generate sets of response surface equations which represent the statistical empirical model for each of the metrics as a function of the key variables. Next, the variables such as the slot geometry can be optimized using the build-in optimizer within JMP. Finally, a wind tunnel testing will be conducted using the optimized slot geometry and other key variables to verify the empirical statistical model. The long term goal for this effort is to assess the impacts of active flow control using air injection at system level as one of the task plan included in the NASAs URETI program with Georgia Institute of Technology.

Zhang, Wei↗
NASA NTRS1999

Effects of Jet Swirl on Mixing of a Light Gas Jet in a Supersonic Airstream

A non reacting experiment was performed to investigate the effects of jet swirl on mixing of a light gas jet in a supersonic airstream. The experiment consisted of two parts. The first part was an investigation of the effects of jet swirl and skew on the mixing and penetration of a 25 deg. supersonic jet injected from a flat surface (flush wall injection) into a supersonic ducted airflow. Specifically, the objective was to determine whether the jet would mix more rapidly if the jet were swirling, and whether swirl, with and without skew, causes the injectant-air plume to have a net circulation (i.e., a single or dominant vortex). The second part was a preliminary study of the mixing of swirling jets injected from the base of a skewed ramp. The hypothesis was that favorable interactions between vorticity generated by the swirling jet and vortices generated by the ramp could produce mixing enhancements. Both parts of the experiment were conducted at equal injectant mass flow rate and total pressure. The results for the flush wall injection cases indicate that, except relatively close to the injection point, swirl, with or without skew, does not enhance the mixing of the jet, and can in fact reduce penetration. In addition, a plume with significant net circulation is not generated, as had previously been believed. The results for the ramp cases indicated no improvements in mixing in comparison with the baseline (swept ramp injector) case. However, it was not possible to determine the vorticity mechanisms underlying the poor performance, since no measurements of vorticity were made. Thus, since many geometric parameters were chosen arbitrarily, the results are inconclusive for this class of injector.

Doerner, Steven E.↗
NASA NTRS2011

Reduction of Altitude Diffuser Jet Noise Using Water Injection

A feasibility study on the effects of injecting water into the exhaust plume of an altitude rocket diffuser for the purpose of reducing the far-field acoustic noise has been performed. Water injection design parameters such as axial placement, angle of injection, diameter of injectors, and mass flow rate of water have been systematically varied during the operation of a subscale altitude test facility. The changes in acoustic far-field noise were measured with an array of free-field microphones in order to quantify the effects of the water injection on overall sound pressure level spectra and directivity. The results showed significant reductions in noise levels were possible with optimum conditions corresponding to water injection at or just upstream of the exit plane of the diffuser. Increasing the angle and mass flow rate of water injection also showed improvements in noise reduction. However, a limit on the maximum water flow rate existed as too large of flow rate could result in un-starting the supersonic diffuser.

Allgood, Daniel C.↗
NASA NTRS2014

Reduction of Altitude Diffuser Jet Noise Using Water Injection

A feasibility study on the effects of injecting water into the exhaust plume of an altitude rocket diffuser for the purpose of reducing the far-field acoustic noise has been performed. Water injection design parameters such as axial placement, angle of injection, diameter of injectors, and mass flow rate of water have been systematically varied during the operation of a subscale altitude test facility. The changes in acoustic far-field noise were measured with an array of free-field microphones in order to quantify the effects of the water injection on overall sound pressure level spectra and directivity. The results showed significant reductions in noise levels were possible with optimum conditions corresponding to water injection at or just upstream of the exit plane of the diffuser. Increasing the angle and mass flow rate of water injection also showed improvements in noise reduction. However, a limit on the maximum water flow rate existed as too large of flow rate could result in un-starting the supersonic diffuser.

Allgood, Daniel C.↗
NASA NTRS1995

Computational study of inlet injection for a Pre-Mixed, Shock-Induced Combustion (PM/SIC) engine

A computational simulation of reacting 2-D and 3-D flowfields in a model inlet section of a Pre-Mixed, Shock-Induced Combustion (PM/SIC) engine concept was performed. LARCK, a multi-dimensional Navier-Stokes code with finite-rate kinetics chemistry developed at NASA LaRC by J.A. White, was adapted for this simulation. The flow conditions in the simulation match those envisioned for the PM/SIC engine experiments currently planned at LaRC. The reacting flowfields were Mach 6.3 freestream air and Mach 2 hydrogen at various pressure and temperature conditions injected through a slot injector at the base of the inlet section. In the PM/SIC engine, fuel is injected at the inlet section upstream of the combustor, and reaction is initiated by the shock wave at the inlet which increases the gas temperature and pressure beyond the kinetic limits for reaction. Many challenges exist prior to establishing shock-controlled combustion as a practical engine concept. These challenges include fuel injection schemes that can provide proper fuel-air mixing without creating large losses in the inlet section, and control of the combustion process so that early ignition or combustion propagation through the inlet boundary layer does not occur. For this project, a parametrics study was carried out to model the fuel injection of hydrogen at different flow conditions. It was found that, as the fuel temperature and pressure were increased, the potential for pre-ignition was high at a short distance downstream of the slot injector. The next stage of this work will investigate injection techniques for enhancing mixing of fuel and air in a manner that prevents or reduces the potential for premature ignition observed numerically.

Gonzalez, D. E.↗
NASA NTRS1981

An investigation of air solubility in Jet A fuel at high pressures

Problems concerned with the supercritical injection concept are discussed. Supercritical injection involves dissolving air into a fuel prior to injection. A similar effect is obtained by preheating the fuel so that a portion of the fuel flashes when its pressure is reduced. Flashing improves atomization properties and the presence of air in the primary zone of a spray flame reduces the formation of pollutants. The investigation is divided into three phases: (1) measure the solubility and density properties of fuel/gas mixtures, including Jet A/air, at pressures and correlate these results using theory; (2) investigate the atomization properties of flashing liquids, including fuel/dissolved gas systems. Determine and correlate the effect of inlet properties and injector geometry on mass flow rates, Sauter mean diameter and spray angles; (3) examine the combustion properties of flashing injection in an open burner flame, considering flame shape and soot production.

Faeth, G. M.↗
NASA NTRS1978

Characterization of a swept-strut hydrogen fuel-injector for scramjet applications

Results of an experimental investigation of a swept-strut hydrogen fuel-injector simulating the center strut of a three strut scramjet module at Mach 6 flight conditions are presented. Detailed wall pressure distributions from over 100 separate tests with overall fuel flow from 0.1 to 1.3 times stoichiometric and test gas stagnation temperature from 1100 to 2400 K were recorded. The distance for pressure rise from the point of injection was found to increase with increasing test stagnation temperature. This trend indicates that chemical kinetics in the immediate region of perpendicular injection are not likely to be the mechanism controlling the onset of pressure rise. A fluid dynamic mechanism is suggested involving separation of the boundary layer downstream of injection which is forced upstream from the trailing edge by pressure rise due to combustion occurring in the base region of the strut. The results obtained indicate that the swept-strut fuel-injector concept can be adapted to a wide range of flight conditions by varying the amount of perpendicular fuel injection.

Northam, G. B.↗