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High-pressure transition in crystalline orthorhombic sulfur has been investigated, using a diamond indentor pressed against a diamond flat to produce pressures up to 300 kbar and an opposed-anvil apparatus to obtain lower pressures. The first indication of sulfur transition using the indentor technique was seen when resistance measured 3 times 10 to the 12th ohm. Transition was found to be sluggish and highly time-dependent.
An improved high pressure turbine stator reducing fuel consumption in current CF6-50 turbofan engines was developed. The feasibility of the roundness and clearance response improvements was demonstrated. Application of these improvements will result in a cruise SFC reduction of 0.22 percent for new engines. For high time engines, the improved roundness and response characteristics results in an 0.5 percent reduction in cruise SFC. A basic life capability of the improved HP turbine stator in over 800 simulated flight cycles without any sign of significant distress is shown.
An apparatus for testing and evaluating the spray pattern of high pressure fuel injector elements for use in supplying fuel to combustion engines is presented. Prior art fuel injector elements were normally tested by use of low pressure apparatuses which did not provide a purge to prevent mist from obscuring the injector element or to prevent frosting of the view windows; could utilize only one fluid during each test; and had their viewing ports positioned one hundred eighty (180 deg) apart, thus preventing optimum use of laser diagnostics. The high pressure fluid injector test apparatus includes an upper hub, an upper weldment or housing, a first clamp and stud/nut assembly for securing the upper hub to the upper weldment, a standoff assembly within the upper weldment, a pair of window housings having view glasses within the upper weldment, an injector block assembly and purge plate within the upper weldment for holding an injector element to be tested and evaluated, a lower weldment or housing, a second clamp and stud/nut assembly for securing the lower weldment to the upper hub, a third clamp and stud/nut assembly for securing the lower hub to the lower weldment, mechanisms for introducing fluid under high pressure for testing an injector element, and mechanisms for purging the apparatus to prevent frosting of view glasses within the window housings and to permit unobstructed viewing of the injector element.
An apparatus for testing and evaluating the spray pattern of high pressure fuel injector elements for use in supplying fuel to combustion engines is presented. Prior art fuel injector elements were normally tested by use of low pressure apparatuses which did not provide a purge to prevent mist from obscuring the injector element or to prevent frosting of the view windows; could utilize only one fluid during each test; and had their viewing ports positioned one hundred eighty (180 deg) apart, thus preventing optimum use of laser diagnostics. The high pressure fluid injector test apparatus includes an upper hub, an upper weldment or housing, a first clamp and stud/nut assembly for securing the upper hub to the upper weldment, a standoff assembly within the upper weldment, a pair of window housings having view glasses within the upper weldment, an injector block assembly and purge plate within the upper weldment for holding an injector element to be tested and evaluated, a lower weldment or housing, a second clamp and stud/nut assembly for securing the lower weldment to the upper weldment, a lower hub, a third clamp and stud/nut assembly for securing the lower hub to the lower weldment, mechanisms for introducing fluid under high pressure for testing an injector element, and mechanisms for purging the apparatus to prevent frosting of view glasses within the window housings and to permit unobstructed viewing of the injector element.
The high-pressure carbon monoxide (HiPco) process for producing single-wall carbon nanotubes (SWNTs) uses iron pentacarbonyl as the source of iron for catalyzing the Boudouard reaction. Attempts using nickel tetracarbonyl led to no production of SWNTs. This paper discusses simulations at a constant condition of 1300 K and 30 atm in which the chemical rate equations are solved for different reaction schemes. A lumped cluster model is developed to limit the number of species in the models, yet it includes fairly large clusters. Reaction rate coefficients in these schemes are based on bond energies of iron and nickel species and on estimates of chemical rates for formation of SWNTs. SWNT growth is measured by the conformation of CO2. It is shown that the production of CO2 is significantly greater for FeCO because of its lower bond energy as compared with that of NiCO. It is also shown that the dissociation and evaporation rates of atoms from small metal clusters have a significant effect on CO2 production. A high rate of evaporation leads to a smaller number of metal clusters available to catalyze the Boudouard reaction. This suggests that if CO reacts with metal clusters and removes atoms from them by forming MeCO, this has the effect of enhancing the evaporation rate and reducing SWNT production. The study also investigates some other reactions in the model that have a less dramatic influence.
Obtaining quantitative measurements of NO concentration via laser-induced fluorescence (LIF) at high pressure requires application of a suitable calibration. While it is best to calibrate as close to the measurement condition as possible, this is not always feasible. To assess the transportability of a calibration factor at high pressure, we have calculated ratios between linear LIF signals corresponding to a constant NO concentration at different measurement and calibration conditions for high-pressure ethane flames. We find that pressure broadening limits the utility of calibrating at a pressure different from that of the measurement, although a calibration performed at a higher pressure is applicable over a wider range of pressures than one performed at atmospheric pressure. If one calibrates at the same pressure, it is best to calibrate at a temperature within 500 K of the measurement temperature. In general, the calculations indicate that a judicious choice of a calibration condition will guarantee a measured NO concentration within a factor of two of the actual NO concentration.
The dynamics and evolution of a magma ocean depend significantly on the structure and physical properties of silicate liquids at high pressure. Viscosity is particularly important because of its effect on the dynamics of convection and crystal setting. Traditionally, the viscosities of silicate liquids have been measured at high pressure by falling sphere viscometry but, due to some limitations of this technique, few measurements have been made at pressures exceeding 2.5 GPa. An alternative approach, which has previously been proven up to 2 GPa, is to use high pressure measurements of oxygen self-diffusivity (D) to estimate viscosity (eta) from the Eyring relationship eta = kT/D lambda (where k is the Boltzmann constant, T is absolute temperature, and lambda is the diffusive jump distance). We have performed preliminary experiments on Na2Si4O9 liquid in order to explore the feasibility of this method up to pressures in excess of 10 GPa. Diffusion couples were prepared from glass starting materials with one half of the sample enriched in O-18 and the other half containing the natural abundance (0.2 wt percent). Diffusion experiments were performed at 1600 to 1800 C at pressures in the range of 2.5 to 10 GPa for times up to 6 minutes using a 1200 ton multianvil apparatus. Oxygen diffusivities were derived from the resulting O-18 concentration profiles, which were analyzed using an ion microprobe. At 1800 C, oxygen diffusivities increase continuously from 1 x 10(exp -10) m(exp -2) s(exp -1) at 2.5 Gpa to 5 x 10(exp -10) m(exp -2) s(exp -1) at 10 GPa. From the Eyring relationship, the viscosity of Na2SiO9 liquid is predicted to decrease by approx. 0.7 log units over this pressure range at 1800 C. These trends, which can be related to changes in the structure of the liquid at high pressure, are in agreement with results of molecular dynamics calculations. These results suggest that it should be possible to estimate the viscosities of silicate liquids up to at least 15 GPa and 2200 C by this method.
High pressure valve used in testing certain spacecraft systems is safely opened and closed by a remotely stationed operator. The valve is self-regulating in that if the incoming pressure drops below a desired value the valve will automatically close, warning the operator that the testing pressure has dropped to an undesired level.
High pressure seals for rotating shafts are machined from a polyimide resin. It is more durable and cheaper than the older seals of plastic coated metal and works at temperatures between - 400 degrees and plus 900 degrees f.
High pressure gaseous hydrogen oxygen auxiliary propulsion systems /APS/ thrustor design and cold flow and hot fire testing for space shuttle requirements
The High Pressure Space Suit Glove Program yielded one prototype glove assembly with an operating pressure of 8.0 psi. The following developments are reported: (1) A new layup technique for incorporation of the mini-convolute systems; (2) modification in the mini-convolute construction to assure cycle life at 8.0 psi in excess of 100,000 cycles; (3) the development of a unique non-orthogonal low torque wrist joint; (4) the development of a low torque single axis joint for use in the thumb and finger first metacarpal joints; and (5) a number of approaches to 1st metacarpal joints were fabricated and tested to establish the joint technqiues.
A high pressure, liquid hydrogen turbopump was designed, fabricated, and tested to a maximum speed of 9739 rad/s and a maximum pump discharge pressure of 2861 N/sq. cm. The approaches used in the analysis and design of the turbopump are described, and fabrication methods are discussed. Data obtained from gas generator tests, turbine performance calibration, and turbopump testing are presented.
A new high pressure turbine shroud material has been developed from the consolidation of prealloyed powders of Ni, Cr, Al and Y. The new material, a filler for cast turbine shroud body segments, is called Genaseal. The development followed the identification of oxidation resistance as the primary cause of prior shroud deterioration, since conversion to oxides reduces erosion resistance and increases spalling under thermal cycled engine conditions. The NICrAlY composition was selected in preference to NIAL and FeCRALY alloys, and was formulated to a prescribed density range that offers suitable erosion resistance, thermal conductivity and elastic modulus for improved behavior as a shroud.
A high pressure, low capacity, liquid hydrogen turbopump was designed, fabricated, and tested. The design configuration of the turbopump is summarized and the results of the analytical and test efforts are presented. Approaches used to pin point the cause of poor suction performance with the original design are described and performance data are included with an axial inlet design which results in excellent suction capability.
A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.
A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.
This is the final report for a research project aimed at developing planar laser-induced fluorescence (PLIF) techniques for quantitative 2-D species imaging in fuel-lean, high-pressure combustion gases, relevant to modem aircraft gas turbine combustors. The program involved both theory and experiment. The theoretical activity led to spectroscopic models that allow calculation of the laser-induced fluorescence produced in OH, NO and 02 for arbitrary excitation wavelength, pressure, temperature, gas mixture and laser linewidth. These spectroscopic models incorporate new information on line- broadening, energy transfer and electronic quench rates. Extensive calculations have been made with these models in order to identify optimum excitation strategies, particularly for detecting low levels (ppm) of NO in the presence of large 02 mole fractions (10% is typical for the fuel-lean combustion of interest). A promising new measurement concept has emerged from these calculations, namely that excitation at specific wavelengths, together with detection of fluorescence in multiple spectral bands, promises to enable simultaneous detection of both NO (at ppm levels) and 02 or possibly NO, 02 and temperature. Calculations have been made to evaluate the expected performance of such a diagnostic for a variety of conditions and choices of excitation and detection wavelengths. The experimental effort began with assembly of a new high-pressure combustor to provide controlled high-temperature and high-pressure combustion products. The non-premixed burner enables access to postflame gases at high temperatures (to 2000 K) and high pressures (to 13 atm), and a range of fuel-air equivalence ratios. The chamber also allowed use of a sampling probe, for chemiluminescent detection of NO/NO2, and thermocouples for measurement of gas temperature. Experiments were conducted to confirm the spectroscopic models for OH, NO and 02.
New experimental results are reported for structural transitions at high pressure in several III-V compounds and two II-VI compounds. These data, together with earlier results, are then compared with the predictions of model calculations of Van Vechten. Experimental transition pressures are often at variance with calculated values. However, his calculation assumes that the high pressure phase is metallic, with the beta-Sn structure. The present results show that several compounds assume an ionic NaCl structure at high pressure, while others have neither the beta-Sn nor NaCl structure.