SEARCH · Engineering Papers

Results for “high-pressure engineering”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15

All sources NASA NTRS DOE OSTI

NASA NTRS1990

Supercritical microgravity droplet vaporization

Supercritical droplet vaporization is an important issue in many combustion systems, such as liquid fueled rockets and compression-ignition (diesel) engines. In order to study the details of droplet behavior at these conditions, an experiment was designed to provide a gas phase environment which is above the critical pressure and critical temperature of a single liquid droplet. In general, the droplet begins as a cold droplet in the hot, high pressure environment. In order to eliminate disruptions to the droplet by convective motion in the gas, forced and natural convection gas motion are required to be small. Implementation of this requirement for forced convection is straightforward, while reduction of natural convection is achieved by reduction in the g-level for the experiment. The resulting experiment consists of a rig which can stably position a droplet without restraint in a high-pressure, high temperature gas field in microgravity. The microgravity field is currently achieved by dropping the device in the NASA Lewis 2.2 second drop tower. The performance of the experimental device and results to date are presented.

Hartfield, J.↗

NASA NTRS1991

Space Shuttle Main Engine nozzle mounted optic for throat plane spectroscopy

A program intended to develop a flight-capable nozzle mounted optic for monitoring emissions from metals entrained in the Space Shuttle Main Engine (SSME) flowfield is described. The optic will collect light emitted from metal atoms within the high-temperature, high-pressure SSME chamber and transfer the optical signal to a high-resolution spectrometer via a fiber-optic cable. The nozzle mounted optic makes it possible to conduct earth-to-orbit monitoring of flowfield emissions without requiring modifications to the SSME.

Bickford, R. L.↗

NASA NTRS1991

Rayleigh-Brillouin scattering for high-pressure gas temperature measurements

An experiment was set up to evaluate the feasibility of using Rayleigh-Brillouin scattering as a diagnostic technique for measuring gas temperature in high pressure environments, such as the Space Shuttle Main Engine (SSME) Preburner. A high pressure furnace is used as the scattering chamber. Either nitrogen or hydrogen may be used. An argon ion laser beam is focused into the furnace. Light backscattering from the gas in the furnace is collected and analyzed with a 5-pass scanning Fabry-Perot interferometer and photon counting electronics. The multi-pass configuration provides the high frequency selectively needed to measure the Brillouin peaks in the presence of large amounts of spuriously scattered light at the laser frequency. Preliminary measurements were made at room temperature in nitrogen at pressures up to 2000 psia. The free spectral range of the interferometer and frequency separation of the Brillouin peaks are determined from measured spectra. Temperature measurements are then obtained using the simple continuum theory with low frequency values of specific heat ratio and shear viscosity. The measured temperatures are within 10 percent of the true value.

Seasholtz, Richard G.↗

NASA NTRS1938

The N.A.C.A. Optical Engine Indicator

An optically recording engine-pressure indicator of simple and rugged construction has been developed for use in high-pressure and high temperature combustion research. This instrument is of the diaphragm type and has a natural frequency of about 10,000 cycles per second.

Tozier, Robert E↗

NASA NTRS1931

Pressure Fluctuations in a Common-Rail Fuel Injection System

This report presents the results of an investigation to determine experimentally the instantaneous pressures at the discharge orifice of a common-rail fuel injection system in which the timing valve and cut-off valve were at some distance from the automatic fuel injection valve, and also to determine the methods by which the pressure fluctuations could be controlled. The results show that pressure wave phenomena occur between the high-pressure reservoir and the discharge orifice, but that these pressure waves can be controlled so as to be advantageous to the injection of the fuel. The results also give data applicable to the design of such an injection system for a high-speed compression-ignition engine.

Rothrock, A M↗

NASA NTRS1993

Brief summary of the evolution of high-temperature creep-fatigue life prediction models for crack initiation

The evolution of high-temperature, creep-fatigue, life-prediction methods used for cyclic crack initiation is traced from inception in the late 1940's. The methods reviewed are material models as opposed to structural life prediction models. Material life models are used by both structural durability analysts and by material scientists. The latter use micromechanistic models as guidance to improve a material's crack initiation resistance. Nearly one hundred approaches and their variations have been proposed to date. This proliferation poses a problem in deciding which method is most appropriate for a given application. Approaches were identified as being combinations of thirteen different classifications. This review is intended to aid both developers and users of high-temperature fatigue life prediction methods by providing a background from which choices can be made. The need for high-temperature, fatigue-life prediction methods followed immediately on the heels of the development of large, costly, high-technology industrial and aerospace equipment immediately following the second world war. Major advances were made in the design and manufacture of high-temperature, high-pressure boilers and steam turbines, nuclear reactors, high-temperature forming dies, high-performance poppet valves, aeronautical gas turbine engines, reusable rocket engines, etc. These advances could no longer be accomplished simply by trial and error using the 'build-em and bust-em' approach. Development lead times were too great and costs too prohibitive to retain such an approach. Analytic assessments of anticipated performance, cost, and durability were introduced to cut costs and shorten lead times. The analytic tools were quite primitive at first and out of necessity evolved in parallel with hardware development. After forty years more descriptive, more accurate, and more efficient analytic tools are being developed. These include thermal-structural finite element and boundary element analyses, advanced constitutive stress-strain-temperature-time relations, and creep-fatigue-environmental models for crack initiation and propagation. The high-temperature durability methods that have evolved for calculating high-temperature fatigue crack initiation lives of structural engineering materials are addressed. Only a few of the methods were refined to the point of being directly useable in design. Recently, two of the methods were transcribed into computer software for use with personal computers.

Halford, Gary R.↗

NASA NTRS1995

High-pressure combustion of binary fuel sprays

The ultimate objective of this study is to obtain fundamental information relevant to combustion processes that occur in fuel sprays of practical interest at high pressures in internal combustion engines. Since practical fuels are multicomponent and derived from petroleum, the present work involves the model alkane mixture of n-heptane and n-hexadecane. Since burning droplets in sprays can interact with each other, the present work involves investigation of the effects of this interaction on flame shapes and droplet burning times. The small droplets in practical combustion chambers are not significantly influenced by buoyancy. Since such small droplets are difficult to study experimentally, the present work takes advantage of microgravity to lessen buoyancy and enable information about droplet interactions to be obtained by studying larger droplets. The results are intended to provide fundamental understanding that can be used in improving descriptions of practical spray combustion.

Mikami, Masato↗

NASA NTRS1977

Space Shuttle Main Engine: Part Number RS007001

Topics considered include: low-pressure oxidizer turbopump; low-pressure fuel turbopump; high-pressure oxidizer turbopump; high-pressure oxidizer turbopump turbine; high-pressure fuel turbopump; and SSME propellant flow schematic.

Guinzburg, A.↗

NASA NTRS1999

The Effects of LOX Post Biasing on SSME Injector Wall Compatibility

An experimental investigation has been carried out to examine the effects of LOX post biasing of a shear coaxial injector on the behavior of the spray near a chamber wall. The experimental work was performed with inert propellant simulants in a high-pressure chamber. Injector flow rates and chamber pressure were designed to match the Space Shuttle Main Engine (SSME) injector gas-to-liquid density and velocity ratio at the point of propellant injection. Measurements of liquid mass flux, gas phase velocity and droplet size were made using mechanical patternation and phase Doppler interferometry techniques. The measurements revealed that the liquid mass flux distribution shifts away from the wall with increasing LOX post bias away from the wall. The shift in the liquid flux distribution was much greater than that caused by the angling of the LOX post alone. Gas velocity near the wall simultaneously increased with increasing LOX post bias away from the wall. The increase in wall side gas velocity was due to the higher fraction of gas injected on the wall side of the injector as a result of the eccentricity at the injector exit. The net result is a decrease in mixture ratio near the wall. Estimates of heat transfer and engine performance relative to the unbiased case are presented.

Strakey, P. A.↗

NASA NTRS1999

SiC and Si3N4 Recession Due to SiO2 Scale Volatility Under Combustor Conditions

Silicon carbide (SiC) and Si3N4 materials were tested in various turbine engine combustion environments chosen to represent either conventional fuel-lean or fuel-rich mixtures proposed for high-speed aircraft. Representative chemical vapor-deposited (CVD), sintered, and composite materials were evaluated by furnace and high-pressure burner rig exposures. Although protective SiO2 scales formed in all cases, the evidence presented supports a model based on paralinear growth kinetics (i.e., parabolic growth moderated simultaneously by linear volatilization). The volatility rate is dependent on temperature, moisture content, system pressure, and gas velocity. The burner tests were thus used to map SiO2 volatility (and SiC recession) over a range of temperatures, pressures, and velocities. The functional dependency of material recession (volatility) that emerged followed the form A[exp(-Q / RT)](P(sup x)v(sup y). These empirical relations were compared with rates predicted from the thermodynamics of volatile SiO and SiOxHy reaction products and a kinetic model of diffusion through a moving boundary layer. For typical combustion conditions, recession of 0.2 to 2 micrometers/hr is predicted at 1200 to 1400 C, far in excess of acceptable long-term limits.

Smialek, James L.↗

NASA NTRS2000

Optical Measurement and Visualization in High-Pressure, High-Temperature, Aviation Gas Turbine Combustors

Planar laser-induced fluorescence (PLIF), planar Mie scattering (PMie), and linear (1-D) spontaneous Raman scattering are applied to flame tube and sector combustors that burn Jet-A fuel at a range of inlet temperatures and pressures that simulate conditions expected in future high-performance civilian gas turbine engines. Chemiluminescence arising from C2 in the flame was also imaged. Flame spectral emissions measurements were obtained using a scanning spectrometer. Several different advanced concept fuel injectors were examined. First-ever PLIF and chemiluminescence data are presented from the 60-atm Gas turbine combustor facility.

Hicks, Yolanda R.↗

NASA NTRS1999

Venus Surface Sample Return: A Weighty High-Pressure Challenge

A mission to return a sample to Earth from the surface of Venus faces a multitude of multidisciplinary challenges. In addition to the complications inherent in any sample return mission, Venus presents the additional difficulties of a deep gravity well essentially equivalent to Earth's and a hot-house atmosphere which generates extremes of high temperature, density, and pressure unmatched at any other known surface in the solar system. The Jet Propulsion Laboratory of the California Institute of Technology recently conducted a study to develop an architecture for such a mission; a major goal of this study was to identify technology developments which would need to be pursued in order to make such a mission feasible at a cost much less than estimated in previous. The final design of this mission is years away but the study results presented here show our current mission architecture as it applies to a particular mission opportunity, give a summary of the engineering and science trades which were made in the process of developing it, and identify the main technology development efforts needed.

Sweetser, Ted↗

NASA NTRS2000

Testing Plant Responses to Rarified Atmospheres for Inflatable Greenhouses

Reduced atmospheric pressures will likely be used to minimize mass and engineering requirements for plant growth habitats used in extraterrestrial applications. A chamber with high vacuum capability was used to design and begin construction of a system for testing plant responses to reduced pressure atmospheres. Several preliminary tests were conducted to evaluate chamber suitability for plant tests and to determine performance of thermal and vacuum systems at ambient and reduced pressure atmospheres down to 0.1 atm. The first tests consisted of measurements of internal gas volume and leakage rate. The method for volume determination was quite sensitive and will be needed for plant gas exchange measurements and calculations. This information will also be used in conjunction with the leak rate. Measured leak rates on the order of 0.46 mm Hg/min at 76 mm Hg pressure are low enough to conduct sensitive carbon dioxide exchange rate measurements at reduced pressure given an adequate plant sample (0.5 to 1.0 sq m area). A test rack with lighting provided by three high-pressure sodium vapor lamps was built to accommodate both short-term and long-term plant responses. Initial short-term experiments with lettuce showed that a pressure of 77 mm Hg resulted in a 6.1-fold increase in the rate of water loss compared to water loss at ambient pressure. Plants were severely wilted after 30 minutes exposure to 77 mm Hg. Water loss was found to be inversely correlated with atmospheric pressure over the range of pressures from 0.2 to 1.0 atm; the rate of water loss at 0.2 atm was 4.3 times higher than water loss at ambient pressure. Older leaves showed moderate wilting during exposure to 156 mm Hg, but those exposed to 345 mm, Hg remained turgid. Results suggest a reduced atmospheric pressure limit of 0.2 to 0.3 atm for lettuce grown in a solid medium. Follow-up experiments with carbon dioxide control and control at high relative humidity (> 90 %) will be needed to further confirm and define safe reduced pressure limits that are feasible for plant tolerance and growth.

Corey, Kenneth A.↗

NASA NTRS1998

Evaluation of dual-tip micromanometers during 21-day implantation in goats

Investigative research efforts using a cardiovascular model required the determination of central circulatory haemodynamic and arterial system parameters for the evaluation of cardiovascular performance. These calculations required continuous beat-to-beat measurement of pressure within the four chambers of the heart and great vessels. Sensitivity and offset drift, longevity, and sources of error for eight 3F dual-tipped micromanometers were determined during 21 days of implantation in goats. Subjects were instrumented with pairs of chronically implanted fluid-filled access catheters in the left and right ventricles, through which dual-tipped (test) micromanometers were chronically inserted and single-tip (standard) micromanometers were acutely inserted. Acutely inserted sensors were calibrated daily and measured pressures were compared in vivo to the chronically inserted sensors. Comparison of the pre- and post-gain calibration of the chronically inserted sensors showed a mean sensitivity drift of 1.0 +/- 0.4% (99% confidence, n = 9 sensors) and mean offset drift of 5.0 +/- 1.5 mmHg (99% confidence, n = 9 sensors). Potential sources of error for these drifts were identified, and included measurement system inaccuracies, temperature drift, hydrostatic column gradients, and dynamic pressure changes. Based upon these findings, we determined that these micromanometers may be chronically inserted in high-pressure chambers for up to 17 days with an acceptable error, but should be limited to acute (hours) insertions in low-pressure applications.

Non-NASA Center↗

NASA NTRS1947

Recent Results on High-Pressure Axial Blowers

Considerable progress has, in recent times, been attained in the development of the high-pressure axial blower by well-planned research. The efforts are directed toward improving the efficiencies, which are already high for the axial blower, and in particular the delivery pressure heads. For high pressures multistage arrangements are used. Of fundamental importance is the careful design of all structural parts of the blower that are subject to the effects of the flow. In the present report, several recent results and experiences are reported, which are based on results of German engine research.

Eckert, B.↗

NASA NTRS1995

High-Aspect-Ratio Cooling Channel Concept Tested in Lewis' Rocket Engine Test Facility

Rocket combustion chamber walls are exposed to the high-temperature environment caused by the combustion of propellants. Even with the walls actively cooled by the fuel, the hot gases can deteriorate the walls severely and limit any possibility for reusing the combustion chamber. For many years, the NASA Lewis Research Center has performed subscale investigations of potential improved cooling concepts to extend the life and reliability of the combustion chamber. Results from previous subscale tests have shown that, by increasing the coolant channel height-to-width aspect ratio, the rocket combustion chamber hot gas side wall temperature can be reduced by as much as 28 percent, without an increase in the coolant pressure drop. Recently, a series of experiments were completed in Lewis' Rocket Engine Test Facility (RETF) to validate the benefits of high aspect ratio cooling channels with a high-pressure, contoured rocket combustion chamber.

Source record↗

NASA NTRS1998

Three-Dimensional Measurements of Fuel Distribution in High-Pressure, High- Temperature, Next-Generation Aviation Gas Turbine Combustors

In our world-class, optically accessible combustion facility at the NASA Lewis Research Center, we have developed the unique capability of making three-dimensional fuel distribution measurements of aviation gas turbine fuel injectors at actual operating conditions. These measurements are made in situ at the actual operating temperatures and pressures using the JP-grade fuels of candidate next-generation advanced aircraft engines for the High Speed Research (HSR) and Advanced Subsonics Technology (AST) programs. The inlet temperature and pressure ranges used thus far are 300 to 1100 F and 80 to 250 psia. With these data, we can obtain the injector spray angles, the fuel mass distributions of liquid and vapor, the degree of fuel vaporization, and the degree to which fuel has been consumed. The data have been used to diagnose the performance of injectors designed both in-house and by major U.S. engine manufacturers and to design new fuel injectors with overall engine performance goals of increased efficiency and reduced environmental impact. Mie scattering is used to visualize the liquid fuel, and laser-induced fluorescence is used to visualize both liquid and fuel vapor.

Hicks, Yolanda R.↗

NASA NTRS1997

High-Pressure Combustion Testing Reveals Promise of Low-Emission Combustors for Advanced Subsonic Gas Turbines

NASA Lewis Research Center's new, world-class, 60-atm combustor research facility, the Advanced Subsonic Combustion Rig (ASCR), is in operation and producing highly unique research data. At operating pressures to 800 psia, emissions of nitrogen oxides were reduced by greater than 70 percent with an advanced fuel injector designed at NASA Lewis. Data, including exhaust emissions and pressure and temperature distributions, were acquired at high pressures and temperatures representative of future subsonic engines. Results to date represent an improved understanding of the formation of nitrogen oxides at these high pressures (twice the pressure of previous combustor tests) and temperatures.

Lyons, Valerie J.↗