Showing papers on "Total pressure published in 1969"

The interaction of shock waves and heat addition in the design of supersonic combustors

Abstract: Analytical models are needed that will permit the prediction of thrust efficiency of a supersonic combustor as a function of combustor geometry and heat release. An earlier, more general procedure for the one-dimensional analysis of supersonic combustors was developed on the basis of exponential pressure-area dependence. This paper extends that analysis by establishing three regimes for specific pseudo-one-dimensional solutions for thrust efficiency: (1) a low-heat-release regime in which the flow can be considered essentially shock-free; (2) an intermediate regime in which an oblique shock wave is sustained with a pressure ratio equal to or greater than that required for turbulent boundary-layer separation; and (3) a high-heat-release regime in which the combustion is preceded by a normal shock. The key to solution is the formulation for the wall-pressure force needed for the momentum equation. With it, a set of integral equations can be solved simultaneously for relationships between pressure ratio, total temperature ratio and area ratio across the combustor in the three regimes. It is argued that the most probable solutions are those that yield the lowest back pressure without violating the entropy limit (second law of thermodynamics). It is shown that such limiting processes, including shock waves, can yield higher over-all efficiencies than shock-free solutions, because the total pressure loss across the shock is more than compensated by the reduction in total pressure loss due to heat addition, which occurs at a lower Mach number. Results of a typical substantiating experiment falling in this class are presented, for a combustor-inlet Mach number of 3.2 and an alkyl borane fuel.

Kinetic mechanisms in nitrogen-chlorine radical systems. Part 1.—The formation and detection of the NCl2 and N3 free radicals using time-resolved absorption spectrophotometry

Abstract: The ultra-violet, infra-red and mass spectra of gaseous NCl3, N3Cl and N3Br are reported. The use of an ultra-violet absorption spectrophotometric system for the measurement of small optical densities in a low-pressure discharge-flow apparatus is described. The radicals NCl2(from the reaction Cl + NCl3) and N3(from the reaction Cl + N3Cl) were detected by means of their ultra-violet absorption spectra, using this system. The rate of removal of NCl2 radicals at 298 K and from 1–3 torr total pressure was second-order in [NCl2] and independent of total pressure, and a mean value for the second-order rate constant, k2=(5.5 ± 0.4)× 1011 cm3 mol–1 s–1, was found under these conditions.

Method of and apparatus for supercharging externally ignited internal combustion engines

Abstract: IN SUPERCHARGED INTERNAL COMBUSTION ENGINES PART OF THE COMPRESSED INTAKE AIR IS DISCHARGED FROM THE INTAKE CONDUIT BY MEANS OF A BYPASS ADJUSTING MECHANISM WHICH IS RESPONSIVE TO PRESSURE CONDITIONS IN SAID CONDUIT AND WHICH CONTROLS BYPASS OPENINGS THEREIN WITH A VARYING PRESSURE DERIVED FROM THE DIFFERENCE BETWEEN AT LEAST ONE STATIC PRESSURE AND THE TOTAL PRESSURE OF THE COMPRESSED INTAKE AIR.

The photochemistry of Jupiter above 1000 Å.

Abstract: Jovian photochemistry above 1000 A appears to consist of four zones: 1) photolysis of methane at 1216 A and a total pressure of less than 10−5 atm; 2) photolysis of ammonia at 1700–2200 A and a total pressure of less than 5×10−4 atm; 3) photolysis of both methane and ammonia at 1350–1450 A at a total pressure of about 10−4 atm; and 4) photolysis of ammonia at 1450–1700 A at a total pressure 1000 A because of the reducing atmosphere. Methane and ammonia persist in the atmosphere because photochemical mechanisms for their destruction ultimately results in their reformation by reaction of such species as CH2, NH and NH2 with H2.

Incremental method for surface area and pore size determination

Abstract: AN APPARATUS FOR PRECISELY MEASURING THE SURFACE OF SOLIDS, PARTICULARLY THOSE IN PARTICULATE FORM. IN ESSENCE, THE MEASURING TECHNIQUE INVOLVES THE FLOWING OF TWO GASES WHICH ARE MIXED IN KNOWN PROPORTIONS AND ARE ALLOWED TO FLOW THROUGH A COOLED SAMPLE CELL CONTAINING A POWDER SAMPLE (ADSORBENT). ONE OF THE GASES (ADSORBATE) IS ADSORBED ON THE POWDER AND THE RESULTING CHANGE IN CONCENTRATION IS DETECTED. THE IMPROVEMENT IS CHARACTERIZED IN THAT THE RELATIVE PRESSURE OF THE ADSORBATE IS VARIED IN SLIGHT INCREMENTS WHEREBY THE ENTIRE ISOTHERM CAN BE OBTAINED, BUT THE VARIATION IS ACHIEVED BY VARYING THE FLOW RATES OF THE INDIVIDUAL GASES WHILE HOLDING THE TOTAL PRESSURE ALWAYS SUBSTANTIALLY AT ATMOSPHERIC.

Method of treating solids with high dynamic pressure

Abstract: A PROCESS FOR TREATING SOLID MATERIALS WITH CONTROLLED, VERY HIGH, DYNAMIC PRESSURES ALL OR A PORTION OF THE TOTAL PRESSURE RISE OCCURING IN A SHOCK COMPRESSION AND ANY REMAINING PORTION OCCURING AS A SMOOTH, RAPID (NONSHOCK) COMPRESSION, THE PRESSURE BEING RELEASED SMOOTHLY TO AMBIENT CONDITIONS, COMPRISING SUBJECTING THE LATERAL BOUNDARIES OF A BODY OF A SOLID MATERIAL TO A PRESSURE PULSE MOVING AT PRACTICALLY CONSTANT VELOCITY IN THE DIRECTION OF THE BODY''S AXIAL DIMENSION AND HAVING PRACTICALLY UNIFORM MAGNITUDE AND DURATION OVER THE LATERAL BOUNDARIES, THE MAGNITUDE AND DURATION BEING SUFFICIENT TO SUSTAIN A SHOCK WAVE OF SUBSTANTIALLY UNIFORM INTENSITY SPANNING A MAJOR PORTION OF THE BODY BETWEEN THE LATERAL BOUNDARIES. THE PROCESS IS USEFUL IN CONVERTING NONDIAMOND CARBON TO DIAMOND AND HEXAGONAL BORON NITRIDE TO CUBIC AND WURTZLIC BORON NITRIDE AND IN COMPACTING SOLID MATERIALS SUCH AS SILICON CARBIDE POWDER.

Studies of the Nitrogen Yellow Afterglow at Low Pressures

Abstract: The visible emission from the B 3Πg state of molecular nitrogen caused by the recombination of atoms has been studied in a fast flow system over the pressure range 35–1000 mtorr. Both N2 and argon have been used as major third bodies, and investigations have been made at a number of different wavelengths. In the case of the pure nitrogen system, the results clearly show the change from second‐order to third‐order kinetics as the total pressure is decreased. Half‐quenching pressures are calculated and are in accord with the idea that electronic quenching is the main means of deactivation of the 3B state. When argon is the major third body, the light emission is still pressure dependent at 1 torr, and considerably higher half‐quenching pressures are calculated. Several reaction mechanisms which might account for the observations are discussed.

Diffusion Coefficients of Vapors Measured with a Moving Boundary

Abstract: A method for the measurement of diffusion coefficients of vapors in gases is described in which the motion of a bead of volatile liquid is observed in a tube with a microporous membrane at one end. Results are given for air with ethyl acetate, benzene, ethanol, and methanol at 22.3° ± 0.3°C and 1 atm total pressure. The determined behavior of the diffusion‐tube system may be considered in studies and measurements of diffusion coefficients of vapors.

Infrared Absorptance of Ammonia—20 to 35 Microns*

Abstract: Experimental absorptance data are given for atmospheres of pure ammonia and for mixtures of ammonia and nitrogen at wavelengths between 20 and 35 μ. The wavelength interval is subdivided into five regions and the total absorptance is tabulated as a function of ammonia pressure and nitrogen pressure for each region. The average absorptance for each region is plotted as a function of the parameter U = WP*, in which W is the ammonia concentration and P* is an effective pressure. This effective pressure is the sum of the total pressure and the ammonia partial pressure multiplied by a self-broadening factor. A single absorptance function fits each region, indicating that the absorption is in the strong line region for the gas pressures used. This absorptance function does not agree with the strong-line limit of either the Goody or Elsasser models of band absorptance.

Thermodynamics of the solubility and permeation of hydrogen in metals at high temperature and low pressure

Abstract: The solubility and permeation of hydrogen in metals is analyzed on the basis of classical thermodynamics plus a minimum of kinetic theory. Expressions are derived for x, the number of H atoms absorbed per solid atom, and J, the permeation rate, in the limiting cases of continuum and free‐molecule flow. For most conditions of temperature (T) and total pressure (pt = pH + pH2), the expressions reduce to the familiar equations for solubility and permeation, i.e., a curve for constant pt appears as a straight line on Arrhenius plots of logx vs 1 / T and of logJ vs 1 / T. However, for extreme conditions of high temperature and low pressure, the expressions predict that a curve of constant pt will become increasingly nonlinear as T increases, and it may even pass through a maximum when T becomes sufficiently high to produce almost complete dissociation of the gaseous H2. Also, under certain conditions neither x nor J is proportional to the square root of the total pressure. The analysis provides a simple explan...

A study of the effects of internal rib and channel geometry in rectangular channels. Part I. Pressure drop

Abstract: Plexiglas models of rectangular channels were fabricated with various rib shapes to determine the effects of rib and channel geometry on the pressure drop. Pressure drops in twenty-four individual variations of channel geometry were investigated using plexiglas models. From this investigation, an empirical correlation for the pressure drop across the ribbed section of the channel was determined as a function of the linear fluid velocity and the geometric characteristics of the channels. This empirical correlation involves functions of seven geometric parameters of rib pattern and channel geometry. Ribbed section pressure drops for commercial plate heat exchanger channels were predicted using the geometric characteristics of the commercial plates with the empirical correlations developed from the plexiglas channel studies. The total pressure drop for commercial channels was predicted by adding an average entrance and exit pressure drop to the predicted ribbed section pressure drop. The correlations developed in this work allow one to determine the pressure drop in a ribbed rectangular channel from the geometric characteristics of the ribs and the channel in question.

Analysis of total-pressure loss and airflow distribution for annular gas turbine combustors

Abstract: Computer analysis of total pressure loss and air flow distribution in annular flow gas turbine combustion chambers

Full-scale development of lift engine inlets for the XV-4 B aircraft.

Abstract: An experimental investigation of lift engine inlet total pressure recovery and total and static pressure distortion during simulated hover and transitional flight has been conducted on a full-scale XV-4B model. The objectives were to develop fixed-geometry inlets for the four vertical-mounted lift engines that were independent of inlet closure door considerations and to provide satisfactory inlet pressure conditions for all modes of VTOL flight. The results indicate that satisfactory inlet pressures can be achieved with a design having single fixed auxiliary lips only in the forward inlets. Engine stalls, surges, and critical vibration levels were absent throughout the test program, which included numerous starts and accelerations at 200 knots relative wind speed. The total pressure recovery at static hover conditions was optimum, while total and static pressure distortions were always less than 13% and generally less than 10% in the VTOL transitional flight regimes for the final inlet configuration. A compact and flexible method of correlating inlet performance data is presented.

Carbon dioxide removal system of the regenerable solid adsorbent type

Abstract: : The development of a regenerable carbon dioxide removal system is discussed. The system utilizes solid zeolites to adsorb carbon dioxide and silica gel for predrying the gas stream. The system is completely regenerable, operates automatically and continuously, and provides for storage of the removed carbon dioxide. It is operable over a wide range of cabin environments and provides flexibility in varying the system operating parameters. It may be used to determine the thermodynamic requirements of a flight-type system for a particular cabin gas composition. The system can remove the carbon dioxide from four crewmen and maintain the carbon dioxide partial pressure between 4 and 5 mm Hg absolute at atmospheric pressure operation and between 6 and 7 mm Hg when operating at 350 mm Hg total pressure. It has this removal capacity when the cabin atmosphere is composed of 13 mm Hg water vapor partial pressure, 160 mm Hg oxygen partial pressure and either nitrogen or helium as the makeup gas. An external control console is provided which permits the system to be operated in an unmanned chamber. The system is not optimized for power and weight; as a laboratory model the total average power required is 4000 watts and the total weight including the mounting frame is 250 pounds. (Author)

Some Measurement Problems Encountered When Determining the Performance of Certain Turbine Stator Blades From Total Pressure Surveys

Abstract: This paper presents some of the problems encountered in determining turbine stator blade performance from total pressure surveys downstream of the blade row. The stator blades were suitable for turbine cooling and incorprated thick trailing edges having a large included wedge angle between the suction and pressure surfaces. Blade performance was rated in terms of kinetic energy loss coefficients, which relate the frictional and mixing losses to the ideal kinetic energy that could be developed at a given overall pressure ratio. The loss coefficients were calculated from the results of total pressure surveys and flow conditions as determined by measurements at the inlet and outlet of the blade row. For the type of blading involved, it was determined that these loss coefficients were sensitive to the size of support stem of the total pressure probe used and the size and axial location of the probe sensing element. The effect of these variables on the results obtained are presented and desirable manners of taking survey data for this type of blading are discussed.© 1969 ASME

Harmonic generation in TR tubes

Abstract: Spurious harmonic power generated in TR tubes was investigated to determine if intersystem interference problems exist and to provide design criteria for controlling spurious signal generation. Harmonic power radiated from typical TR tubes was measured as a function of incident power, pressure, and geometry for discharges in chlorine, water vapor, hydrogen, nitrogen, and argon. Harmonic power decreased by about 20 dB for each decade increase in total pressure in the 0.2 to 20 torr range. Conversion loss varied from 28 to 70 dB. Harmonic power was radiated in a series of resonant peaks which varied with incident power and pressure. TR tubes meet the desired requirements for spurious radiation of -40 dBm/kHz for incident pulse widths less than 1.0 µs when filled to total pressures in the usual 10 to 15 torr range. At pulse widths greater than about 10 µs it becomes necessary to suppress spurious radiation by either filtering or harmonic trapping to reduce intersystem interference.

Gas phase photochlorination of perfluorocyclohexene

Abstract: The kinetics of the gas phase photochemical reaction between perfluorocyclohexene and chlorine was studied between 10 and 50 °C. The system was irradiated with light of 4360 A. The rate of the photochlorination was independent of the perfluorocyclohexene pressure and of the total pressure. It was found to be proportional to the first power of the pressure of Cl2 and to the square root of the intensity of absorbed light. At 30 °C, the quantum yield was found to be 200 when the initial Cl2 pressure was 100 Torr, and intensity of light absorbed 9.89 × 10−9 einstein l−1s−1.An activation energy of 5.1 kcal/mole could be assigned to the reaction C6F10Cl + Cl2.

A method for determining the bulk properties of arc-heated argon

Abstract: : The total temperature and total pressure of argon gas at the exit of a direct-current arc jet are determined by using a corrected version of the one- dimensional, constant-area, heat-addition analysis. The corrections are formulated in terms of the thrust produced by the arc jet and are determined by measuring the actual thrust. To assess the validity of properties determined in this manner, a method of characteristics solution of the general potential flow equations was obtained for the flow field resulting from a free expansion of the gas from these properties into a low pressure. Mach numbers given by this solution were then compared with those derived from measured pitot pressures in the expanded stream. The agreement between the predicted and the average measured values of Mach number is within about 4 percent. This would allow the average static temperature to be predicted within about 8 percent and the average static pressure to be predicted within about 18 percent. This indicates that the method of predicting the gas properties at the exit of the arc jet can be used as a first approximation.

Analysis on the Pressure Distribution around the Impeller of Volute Pumps

Abstract: When a volute pump is operated under various off-design conditions, the impeller sufferes radial thrust due to the pressure varying around the impeller. The author analyzes the pressure distribution around the impeller under the assumption that the total pressure and the velocity of the fluid leaving the impeller depends upon the local static pressure. In the analysis the impeller periphery is replaced by a straight line, the volute by a wedge shape space, and the flow in the wedge shape space is disintegrated into potential flows and a flow with vortices so that the combined flow many satisfy the boundary conditions along the impeller periphery as well as along the volute wall.The theory predict that the pressure near the tang is contant regardless of the flow rate of pump and that the pressure variation along the periphery is little near the tang and is significant near the exit of the volute. These predictions agree well with experimental facts quoted in the literature.

Vaporization of Cuprous Oxide and Other Dissociating Oxides

Abstract: The behavior of dissociating oxides at high temperatures is briefly reviewed. At low pressures the composition of the oxide will correspond to an equilibrium oxygen pressure quite different from the ambient oxygen pressure. Evaporation rate studies on cuprous oxide in various atmospheres show that this oxide dissociates according to Cu2O (solid) → 2Cu (gas) + 1/2O2 (gas).