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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 NTRS1956

Simulated afterburner performance with hydrogen peroxide injection for thrust augmentation

Combustion performance of three afterburner configurations was evaluated at simulated altitude flight conditions with liquid augmentation to the primary combustor. Afterburner combustion efficiency and stability were better with injection of high-strength hydrogen peroxide than with no injection or with water injection. Improvements were observed in afterburner configurations with and without flameholders and in a short-length afterburner. At a peroxide-air ratio of 0.3, combustion was stable and 85 to 90 percent efficient in all configurations tested. Calculated augmented net-thrust ratios for peroxide injection with afterburning were approximately 60 percent greater than those for water injection.

Metzler, Allen J↗
NASA NTRS1927

A Preliminary Study of Fuel Injection and Compression Ignition as Applied to an Aircraft Engine Cylinder

This report summarizes some results obtained with a single cylinder test engine at the Langley Field Laboratory during a preliminary investigation of the problem of applying fuel injection and compression ignition to aircraft engines. For this work a standard Liberty Engine cylinder was fitted with a high compression, 11.4 : 1 compression ratio, piston, and equipped with an airless injection system, including a primary fuel pump, an injection pump, and an automatic injection valve. The results obtained during this investigation have indicated the possibility of applying airless injection and compression ignition to a cylinder of this size, 8-inch bore by 7-inch stroke, when operating at engine speeds as high as 1,850 R. P. M. A minimum specific fuel consumption with diesel engine fuel oil of 0.30 pound per I. HP. Hour was obtained when developing about 16 B. HP. At 1,730 R. P. M.

Gardiner, Arthur W↗
NASA NTRS1932

Coefficients of discharge of fuel-injection nozzles for compression-ignition engines

This report presents the results of an investigation to determine the coefficients of discharge of nozzles with small, round orifices of the size used with high-speed compression-ignition engines. The injection pressures and chamber back pressures employed were comparable to those existing in compression-ignition engines during injection. The construction of the nozzles was varied to determine the effect of the nozzle design on the coefficient. Tests were also made with nozzles assembled in an automatic injection valve, both with a plain and with a helically grooved stem. It was found that a smooth passage before the orifice is requisite for high flow efficiency. A beveled leading edge before the orifice gave a higher coefficient of discharge than a rounded edge. The results with the nozzles assembled in an automatic injection valve having a plain stem duplicated those with the nozzles assembled at the end of a straight tube of constant diameter. Lower coefficients were obtained with the nozzles assembled in an injection valve having a helically grooved stem. When the coefficients of nozzles of any one geometrical shape were plotted against values of corresponding Reynold's numbers for the orifice diameters and rates of flow tested, it was found that experimental points were distributed along a single curve.

Gelalles, A G↗
NASA NTRS1934

Penetration and Duration of Fuel Sprays from a Pump Injection System

High-speed motion pictures were taken of individual fuel sprays from a pump injection system. The changes in the spray-tip penetration with changes in the pump speed, injection-valve opening and closing pressures, discharge-orifice area, injection-tube length and diameter, and pump throttle setting were measured. The pump was used with and without a check valve. The results show that the penetration of the spray tip can be controlled by the dimensions of the injection tube, the area of the discharge orifice, and the injection-valve opening and closing pressures.

Rothrock, A M↗
NASA NTRS1941

An Apparatus for Measuring Rates of Discharge of a Fuel-Injection System

A portable apparatus for rapidly determining rates of discharge of a fuel-injection system is described. Satisfactory operation of this apparatus with injection-pump speeds up to 2400 r.p.m was obtained. Rate-of-discharge tests were made with several cam-plunger-valve injection systems with long injection tubes. A check valve designed to reduce secondary discharges was tested. This check valve was operated with injection-pump speeds up to 2400 r.p.m without the occurrence of large secondary discharges.

Dutee, Francis J↗
NASA NTRS1994

Injection profiles of solar energetic particles as functions of coronal mass ejection heights

Previous studies with Skylab and Solwind coronal mass ejections (CMEs) have shown that nearly all large E greater than 10 MeV solar energetic particle (SEP) events are associated with fast (v greater than 400 km/sec) CMEs. We compare heights of CMEs observed on the SMM spacecraft with the flux-time profiles of five associated SEP events observed by the GOES spacecraft, including three events observed as ground-level events (GLEs) by neutron monitors. The SEP injection profiles as functions of the CME heights are estimated from the 'solar release times' and the effects of interplanetary scattering. We find that the peaks of the 470 MeV to 4 GeV injection profiles of the GLEs occur when CME heights reach 5 to 15 R(sub 0) or greater and that the onsets occur no earlier than the maxima of the flare impulsive phases. In those events SEP injection appears to result only from a single CME-driven shock and not from the flare impulsive phase or from separate coronal and interplanetary shocks. In one small SEP event an impulsive flux-time profile is consistent with injection during the flare impulsive phase but could also be due to injection from a coronal shock over a limited time.

Kahler, S.↗
NASA NTRS1994

Localized injection of large-amplitude Pc 1 waves and electron temperature enhancement near the plasmapause observed by DE2 in the upper ionosphere

The relation between electron temperature enhancement and large amplitude Pc 1 wave injections in the upper ionosphere is investigated using the data obtained by the Dynamics Explorer 2 spacecraft. Results can be summarized as follows: (1) The region of the temperature enhancement coincides with that of the wave injection which is latitudinally very narrow (less than 100 km) in comparison with the wavelength along the ambient magnetic field (several hundred kilometers). (2) The duration of the wave injection (or the temperature enhancement) seems to be less than a few hours even under quiet geomagnetic conditions, and/or the injection seems to be very localized, not only latitudinally, but also longitudinally. (3) The appearance and the magnitude of temperature enhancement depend on both the wave amplitude and the satellite altitude. (4) Two of the 22 events that were analyzed show a clear enhancement of low-energy electron flux (5 to 30 eV) at the wave injection, and the flux is field-aligned both downward and upward. The region of the temperature enhancement coincides with that of the downward electron flux. From these results, it is suggested that the temperature enhancement which accompanies large-amplitude waves with Pc 1 pulsation frequencies (0.2 to 5 Hz) is caused by the direct acceleration of thermal electrons at low altitudes by the parallel electric field (0.01 to 0.001 mV/m) of the ion-cyclotron waves (kinetic Alfven waves) having an oblique wave normal.

Iyemori, T.↗
NASA NTRS1994

Experimental and numerical study of swept ramp injection into a supersonic flowfield

Time-averaged measurements of pressure, temperature, velocity, and injectant mole fraction are presented using the planar laser-induced iodine fluorescence technique in the complex three-dimensional compressible flowfield around a swept ramp fuel injector. Within the range of thermodynamic conditions present in the test case studied, the technique's accuracy is estimated to be 4% for pressure, temperature, and velocity and 3% for injectant mole fraction. Comparisons with numerical simulations using the SPARK three-dimensional Navier-Stokes computer code with an algebraic turbulence model are made at the centerplane of the flowfield as well as on three crossflow planes downstream of the injector. Calculations and measurements are in good agreement throughout the flowfield, with deviations on the order of 5%; however, in specific regions, such as in the base of the ramp, deviations are larger. A weak asymmetry in the incoming flowfield appears to be amplified by boundary-layer separation occurring when the ramp-generated shock reflects off the tunnel walls. Ramp-generated vortices are weaker in the calculated results due to the effects of numerical viscosity in the vortex cores. This leads to less turning and mixing of the jet plume than observed in the experiments. The rate of decay of the maximum injectant mole fraction with streamwise distance is greater for the present ramp injection scheme than for previously measured transverse injection schemes. In this recirculation region at the base of the injector, laminar calculations show better agreement with the measurements than turbulent calculations.

Donohue, James M.↗
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 NTRS2000

Mixing of an Airblast-atomized Fuel Spray Injected into a Crossflow of Air

The injection of a spray of fuel droplets into a crossflow of air provides a means of rapidly mixing liquid fuel and air for combustion applications. Injecting the liquid as a spray reduces the mixing length needed to accommodate liquid breakup, while the transverse injection of the spray into the air stream takes advantage of the dynamic mixing induced by the jet-crossflow interaction. The structure of the spray, formed from a model plain-jet airblast atomizer, is investigated in order to determine and understand the factors leading to its dispersion. To attain this goal, the problem is divided into the following tasks which involve: (1) developing planar imaging techniques that visualize fuel and air distributions in the spray, (2) characterizing the airblast spray without a crossflow, and (3) characterizing the airblast spray upon injection into a crossflow. Geometric and operating conditions are varied in order to affect the atomization, penetration, and dispersion of the spray into the crossflow. The airblast spray is first characterized, using imaging techniques, as it issues into a quiescent environment. The spray breakup modes are classified in a liquid Reynolds number versus airblast Weber number regime chart. This work focuses on sprays formed by the "prompt" atomization mode, which induces a well-atomized and well-dispersed spray, and which also produces a two-lobed liquid distribution corresponding to the atomizing air passageways in the injector. The characterization of the spray jet injected into the crossflow reveals the different processes that control its dispersion. Correlations that describe the inner and outer boundaries of the spray jet are developed, using the definition of a two-phase momentum-flux ratio. Cross-sections of the liquid spray depict elliptically-shaped distributions, with the exception of the finely-atomized sprays which show kidney-shaped distributions reminiscent of those obtained in gaseous jet in crossflow systems. A droplet trajectory analysis overpredicts the liquid mass penetration, and indicates a need for a more rigorous model to account for the three-dimensional mixing field induced by the jet-crossflow interaction. Nonetheless, the general procedures and criteria that are outlined can be used to efficiently assess and compare the quality of sprays formed under different conditions.

Leong, May Y.↗
NASA NTRS2003

Active Flow Separation Control of a Stator Vane Using Surface Injection in a Multistage Compressor Experiment

Micro-flow control actuation embedded in a stator vane was used to successfully control separation and improve near stall performance in a multistage compressor rig at NASA Glenn. Using specially designed stator vanes configured with internal actuation to deliver pulsating air through slots along the suction surface, a research study was performed to identify performance benefits using this microflow control approach. Pressure profiles and unsteady pressure measurements along the blade surface and at the shroud provided a dynamic look at the compressor during microflow air injection. These pressure measurements lead to a tracking algorithm to identify the onset of separation. The testing included steady air injection at various slot locations along the vane. The research also examined the benefit of pulsed injection and actively controlled air injection along the stator vane. Two types of actuation schemes were studied, including an embedded actuator for on-blade control. Successful application of an online detection and flow control scheme will be discussed. Testing showed dramatic performance benefit for flow reattachment and subsequent improvement in diffusion through the use of pulsed controlled injection. The paper will discuss the experimental setup, the blade configurations, and preliminary CFD results which guided the slot location along the blade. The paper will also show the pressure profiles and unsteady pressure measurements used to track flow control enhancement, and will conclude with the tracking algorithm for adjusting the control.

Culley, Dennis E.↗
NASA NTRS1998

PAB3D Simulations of a Nozzle with Fluidic Injection for Yaw Thrust-Vector Control

An experimental and computational study was conducted on an exhaust nozzle with fluidic injection for yaw thrust-vector control. The nozzle concept was tested experimentally in the NASA Langley Jet Exit Test Facility (JETF) at nozzle pressure ratios up to 4 and secondary fluidic injection flow rates up to 15 percent of the primary flow rate. Although many injection-port geometries and two nozzle planforms (symmetric and asymmetric) were tested experimentally, this paper focuses on the computational results of the more successful asymmetric planform with a slot injection port. This nozzle concept was simulated with the Navier-Stokes flow solver, PAB3D, invoking the Shih, Zhu, and Lumley algebraic Reynolds stress turbulence model (ASM) at nozzle pressure ratios (NPRs) of 2,3, and 4 with secondary to primary injection flow rates (w(sub s)/w(sub p)) of 0, 2, 7 and 10 percent.

Deere, Karen A.↗
NASA NTRS2006

Jupiter Icy Moons Orbiter interplanetary injection period analysis

This paper investigates the sensitivity of the planned Jupiter Icy Moons Orbiter mission to variations in interplanetary injection date, magnitude, and direction, starting in a low-Earth assembly orbit. These results are used to determine the frequency and number of injection opportunities from a processing assembly obit. It is shown that the use of a low-thrust propulsion system with a nuclear-electric power source would allow the interplanetary trajectory performance to be relatively insensitive to variations in injection conditions. This result yields many injection opportunities due to the long injection period and consecutive orbits with favorable geometry.

trajectory↗
NASA NTRS2007

Impact of Air Injection on Jet Noise

The objective of this viewgraph presentation is to review the program to determine impact of core fluidic chevrons on noise produced by dual stream jets (i.e., broadband shock noise - supersonic, and mixing noise - subsonic and supersonic). The presentation reviews the sources of jet noise. It shows designs of Generation II Fluidic Chevrons. The injection impacts shock structure and stream disturbances through enhanced mixing. This may impact constructive interference between acoustic sources. The high fan pressures may inhibit mixing produced by core injectors. A fan stream injection may be required for better noise reduction. In future the modification of Gen II nozzles to allow for some azimuthal control: will allow for higher mass flow rates and will allow for shallower injection angles A Flow field study is scheduled for spring, 2008 The conclusions are that injection can reduce well-defined shock noise and injection reduces mixing noise near peak jet noise angle

Henderson, Brenda↗
NASA NTRS2000

Lean direct wall fuel injection method and devices

A fuel combustion chamber, and a method of and a nozzle for mixing liquid fuel and air in the fuel combustion chamber in lean direct injection combustion for advanced gas turbine engines, including aircraft engines. Liquid fuel in a form of jet is injected directly into a cylindrical combustion chamber from the combustion chamber wall surface in a direction opposite to the direction of the swirling air at an angle of from about 50.degree. to about 60.degree. with respect to a tangential line of the cylindrical combustion chamber and at a fuel-lean condition, with a liquid droplet momentum to air momentum ratio in the range of from about 0.05 to about 0.12. Advanced gas turbines benefit from lean direct wall injection combustion. The lean direct wall injection technique of the present invention provides fast, uniform, well-stirred mixing of fuel and air. In addition, in order to further improve combustion, the fuel can be injected at a venturi located in the combustion chamber at a point adjacent the air swirler.

Choi, Kyung J.↗
NASA NTRS2008

Injecting Artificial Memory Errors Into a Running Computer Program

Single-event upsets (SEUs) or bitflips are computer memory errors caused by radiation. BITFLIPS (Basic Instrumentation Tool for Fault Localized Injection of Probabilistic SEUs) is a computer program that deliberately injects SEUs into another computer program, while the latter is running, for the purpose of evaluating the fault tolerance of that program. BITFLIPS was written as a plug-in extension of the open-source Valgrind debugging and profiling software. BITFLIPS can inject SEUs into any program that can be run on the Linux operating system, without needing to modify the program s source code. Further, if access to the original program source code is available, BITFLIPS offers fine-grained control over exactly when and which areas of memory (as specified via program variables) will be subjected to SEUs. The rate of injection of SEUs is controlled by specifying either a fault probability or a fault rate based on memory size and radiation exposure time, in units of SEUs per byte per second. BITFLIPS can also log each SEU that it injects and, if program source code is available, report the magnitude of effect of the SEU on a floating-point value or other program variable.

Bornstein, Benjamin J.↗
NASA NTRS2007

Reverse-Tangent Injection in a Centrifugal Compressor

Injection of working fluid into a centrifugal compressor in the reverse tangent direction has been invented as a way of preventing flow instabilities (stall and surge) or restoring stability when stall or surge has already commenced. The invention applies, in particular, to a centrifugal compressor, the diffuser of which contains vanes that divide the flow into channels oriented partly radially and partly tangentially. In reverse-tangent injection, a stream or jet of the working fluid (the fluid that is compressed) is injected into the vaneless annular region between the blades of the impeller and the vanes of the diffuser. As used here, "reverse" signifies that the injected flow opposes (and thereby reduces) the tangential component of the velocity of the impeller discharge. At the same time, the injected jet acts to increase the radial component of the velocity of the impeller discharge.

Skoch, Gary J.↗
NASA NTRS2010

Fluidic Injection for Jet Noise Reduction

Investigations into fluidic injection for jet noise reduction began over 50 years ago. Studies have included water and air injection for the reduction of noise in scale model jets and jet engines and water injection for the reduction of excess overpressures on the Space Shuttle at lift-off. Injection systems have included high pressure microjets as well as larger scale injectors operating at pressures that can be achieved in real jet engines. An historical perspective highlighting noise reduction potential is presented for injection concepts investigated over the last 50 years. Results from recent investigations conducted at NASA are presented for supersonic and subsonic dual-stream jets. The noise reduction benefits achieved through fluidic contouring using an azimuthally controlled nozzle will be discussed.

Henderson, Brenda↗