Showing papers on "Chamber pressure published in 1974"

Combustion Response Function Measurements by the Rotating Valve Method

Abstract: A study has been conducted to evaluate the rotating valve method of measuring the combustion response of solid propellants to small amplitude pressure oscillations. The method is based on producing pressure oscillations in a small rocket motor by varying the area of a secondary exhaust nozzle in a periodic manner. This is accomplished by using a rotating valve as the secondary orifice. The valve apparatus operates concurrently with a primary nozzle which controls the steady-state pressure. The frequency of the oscillations is determined by the rotational speed of the valve. A theoretical analysis was conducted to relate the combustion response function to measurable ballistic properties of the combustion chamber. Assuming that the combustion chamber is small in comparison to the acoustic wavelength, the combustion response function can be calculated from the amplitude of the oscillating pressure and the phase angle between the oscillating pressure and oscillating nozzle area. Cold flow tests were conducted using nitrogen and helium to test the validity of the analysis. Excellent agreement was found between the measured and predicted amplitudes and phase angles. Combustion tests then were conducted using two aluminized propellant formulations and three nonaluminized formulations. There was excellent agreement between the T-burner and rotating valve tests conducted on the same batch of propellant. For two nonaluminized propellants, the comparisons were based on different batches of propellant. Differences in combustion response and variations in burning rate and characteristic exhaust velocity were observed for these two formulations. It was concluded that the rotating valve method is a valid substitute for the T-burner. Substantial reductions in the cost of characterizing propellants also were obtained using this new approach.

Detonation Propulsion for High Pressure Environments

Abstract: One limitation encountered by chemical rocket propulsion in high-pressure planetary atmospheres is illustrated by the conflict between the dependence of specific impulse on the ratio of chamber pressure to ambient pressure and the dependence of the motor structural design on the difference between the pressures. This work proposes to resolve the difficulty by employing detonating propellant in which the high pressures necessary for efficient propulsion are developed over a short time and need not be contained statically. Experimental results are presented to substantiate this claim of relatively high performance, together with an analytical development that approximately describes the flow dynamics. Nomenclature A = nozzle cross-sectional area ca — speed of sound in ambient gas CD = flow coefficient ea = specific energy released in explosion, EJme Ea — energy released in explosion Ea' = energy released per solid angle, Ejai /i/2 = functions of y, Eq. (15) /3 = function, Eq. (19) F = axial thrust g = acceleration of gravity gc = conversion constant G = integral, Eq. (16) H = integral, Eq. (16) Ht = total enthalpy A/I = height / = specific impulse L = axial length of nozzle m = mass of gas ma = mass of ambient gas contained in nozzle me = mass of explosive material ra = mass flow rate M = mass of equipment Mw = molecular weight P = static pressure Pa = ambient pressure Po = plateau pressure Ap = pressure difference, Pt — Pa r — radial distance from apex of cone re = effective radial length of nozzle, Table 4 R = gas constant Ru = universal gas constant Ri = characteristic radial length, Eq. (17) t — time T = temperature u = velocity V = volume z = elevation a = function of y, Table 3 y = specific heat ratio

Hydraulic oscillator and systems utilizing the same

Abstract: A hydraulic oscillator which produces a pulsed output from a steady flow input. The oscillator utilizes a rigid pressure chamber containing a charge of gas under pressure. A conduit passes through this chamber, and the conduit includes an inlet passage, an outlet passage, and, interconnecting and extending between these passages, a flexible, resilient, collapsible-walled tubular portion. The outside of this portion is fully peripherally exposed to gas pressure in the chamber. When the impedance and resistance to liquid flow through the inlet and outlet passages, the elasticity and dimensions of the tubular portion, and the gas pressure in the chamber, are appropriately selected, then a liquid stream entering the inlet passage at a suitable pressure relative to the chamber pressure, will emerge as a pulsating flow. This pulsating flow is particularly suited to many purposes, including the cleaning, irrigating and massaging of biological living tissue, the creation of cavitation in a flowing stream, and the momentary and cyclical reversal of the direction of flow in a generally forwardly flowing system. Systems for utilizing this oscillator for these purposes are disclosed.

Dump Combustor Parametric Investigation

Abstract: : A series of scale model coaxial dump combustors from 2 inch to 5 inch D were tested on a thrust stand with JP-4 fuel over a wide range of ramjet test conditions. Baseline conditions were selected to approximate 'pressure scaling criteria' in which chamber pressure times combustor diameter remains constant. JP-4 fuel was injected perpendicular to the airstream from eight plane tube injectors. Fuel/air ratio, chamber pressure and nozzle throat diameter were varied for each size chamber. Lean blow-out limit, combustion efficiency, combustor pressure drop, and combustion instability characteristics were obtained for each test point.

Appartus for limiting vacuum and pressure in a furnace

Abstract: A furnace system having a combustion chamber, and heat transfer surfaces, forced and induced draft fans for moving gas through the burner, chamber, and heattransfer surfaces, first controls for maintaining predetermined gas flows and furnace pressure or draft dependent upon the desired normal operating conditions, and second controls responsive to the flow of the gas exterior to the chamber, e.g., at the inlet or outlet of the induced draft fan and, if desired, at the outlet of the forced draft fan, for controlling a damper or dampers in the gas path or the speed of the fans so as to limit the vacuum which can be developed in the chamber by the induced draft fan to a value less than the chamber vacuum withstanding design value. Also, if desired, the second controls at the outlet of the forced draft fan can limit pressure which can be developed in the chamber by the forced draft fan to a value less than the chamber pressure withstanding design value.

Significance of variably confined triaxial testing

Abstract: Two types of tests were performed in an earlier study - the constant confining pressure (CCP) test, in which the chamber pressure is held constant during application of the repeated axial stress and the variable confining pressure (VCP) test, in which the chamber pressure is applied dynamically and varied simultaneously with the axial stress. A sensitivity analysis, consisting of finite element analyses of typical flexible pavement sections, is examined. The granular material resilient parameters are varied over a wide range of laboratory-derived values. The importance of accounting for the stress-dependent properties of paving materials in pavement structural analysis is demonstrated by the drastic changes in stress and deflection distribution effected by the inclusion of stabilized layers beneath unbound granular base courses. The significance of differences in material parameters derived from the two types of triaxial tests are assessed, and it is shown that the less complicated CCP test yields sufficiently accurate results to warrant its continued use as a means of characterizing granular pavement materials.

Method and apparatus for sterilizing with a heavier-than-air gas

Abstract: Sterilizing apparatus and method in which a heavier-than-air sterilizing gas is introduced at a substantially constant flow rate into the bottom of the sterilizing chamber. Air in the chamber is displaced upwardly by the gas and out of the chamber through a restricted exhaust which is open throughout the gas introduction period. The pressure at the top of the chamber is monitored and the restricted exhaust is closed when the pressure has increased to a preselected level, the pressure level being directly related to the gas concentration. The gas inlet remains open for a time to provide a chamber pressure which will help to displace air trapped in the material being sterilized.

Cold chamber pressure die casting machine - with heater in pressure chamber to avoid metal residues

Abstract: Pref. the chamber is heated to above the metal liquidns temp. near its inside wall and generally along the length between the front end of the injection piston and the facing end of the chamber. The piston may also be heated. The heaters are pref. resistance heaters and insulation is provided between the chamber and adjacent machine parts. The machine is esp. used for Mg casting under a protective atmos.

Numerical Investigation of Nonlinear Axial Instabilities in Solid Rocket Motors

Abstract: : Nonlinear axial-mode combustion instability remains a serious problem in the development of solid propellant rocket motors. Although the use of metal- loaded solid propellants which produce solid particles in the flow has reduced the occurrence of high frequency instabilities, it has not eliminated the axial-mode intermediate frequency (100 - 1000 Hz.) problem. If such an instability reaches a large amplitude limit cycle, it may lead to an increase in mean chamber pressure and burning rate, excessive heat transfer rates, and a severe vibration level. The objective of this report is to investigate the complex coupling between the chamber flow conditions and the solid propellant combustion process which may lead to large amplitude longitudinal instabilities.

Fuel pump for internal combustion engines

Abstract: A fuel pump for an internal combustion engine of the type wherein cyclic pressure fluctuations are produced in the engine crankcase chamber during engine operation by the reciprocating motion of an engine piston. The pump embodies fuel pumping means including a pulsatory pumping member or pulsator, such as a diaphragm, and is mounted directly on the engine with the pumping pulsator exposed directly to the engine crankcase chamber in such a way that the chamber pressure fluctuations drive the pulsator in its pulsating pumping motion to pump fuel from the fuel inlet to the fuel outlet of the pump. Also embodied in the pump are a novel fuel pressure regulating valve for maintaining a substantially constant fuel outlet pressure regardless of engine speed and an automatic fuel shut-off valve for blocking fuel leakage through the pump under the action of head pressure or other forces when engine operation ceases.

Evacuable membrane apparatus for tire recapping

Abstract: Evacuable membrane apparatus permits vulcanizing pre-formed tread strips to tire casings in a pressure chamber without danger of leakage of its pressurized air between the evacuated membranes. The outer margins of upper and lower membranes are clamped between a pressure bar hoop and the inflated resilient face of a pressure-resisting rim. By applying inflation pressure to the rim in excess of the chamber pressure, the membrane edges are clamped so tightly that the chamber air will not enter between them even after the membranes are evacuated.

Pressure die casting melt dispenser - with two separate compressed gas operating systems

Abstract: The device comprises a gas supply into one chamber of a two chamber pressure vessel with a pressure adjustable gas tight partition, the second chamber of which is connected by a pressure transmission line with an enclosed space above the melt level, which second system is filled with a gas which is inert both in regard to the melt and the system construction materials. Dispensing is effected by the timed application of pressure to the melt surface. The partition in the pressure vessel consists pref. of a membrane. The pref. inert gases are either N or one of the noble gases. The system employs inert gas only for the last stage of pressure transmission thus economising in the use of this gas, permitting the use of e.g. compressed air for the other system.

High Chamber Pressure Blast Tube and Nozzle Material Evaluation. Volume 1

Abstract: : The objectives were to evaluate the effects of propellant corrosivity and blast tube contraction ratio on candidate nozzle materials in high chamber pressure rocket motor environments (3,000 and 3,500 psia). A total of 16 lightweight aft closures and nozzles were designed, fabricated, and test fired. High velocity blast tubes with contraction ratios of 2.0 and 1.3, respectively, were used on all nozzles. The effects of propellant flame temperature and corrosivity were evaluated by testing with both 18% and 5% aluminized, 88% solids loaded CTPB propellants. The effects of both cylindrical and keyhole port grain configurations also were evaluated. Conventional state-of-the-art phenolic, elastomeric, graphite materials were used.

Variation of Atomic Hydrogen Density in a Propane/Oxygen Flame as a Function of Chamber Pressure

Abstract: Atomic hydrogen profiles were determined for a 5.8% propane/94.2% oxygen flame over the pressure range of 10 to 40 torr by utilizing the electron spin resonance (ESR) spectroscopy techniques originally developed by Fristrom and Westenberg (1965). These profiles were compared with the predicted theoretical behavior and correlated with temperature profiles obtained over the same pressure range. Two factors affecting the results of the Fristrom-Westenberg experiment were also observed.

Investigations on Powder Rocket System

Abstract: Results of investigations on powder rockets using LiAlH4 as energetic fuel are discussed. Theoretical evaluatioll of Isp shows that maximum Isp is 350sec for LiAlH4-H2O2 (90% aq) system in vacuum with nozzle expansion ratio 40. Experiments of the powder rocket system are conducted to study the problems concerning to the feed system and the combustion efficiency. Tested fuel is LiAlH4: polyethylene of 1:1 mixture which is hyperbolic with H2O2. Firing tests with 4-5sec of duration have shown relatively smooth operation. 90% of efficiency has been derived with respect to speific impulse perform-ance despite small chamber size and low chamber pressure in the experimental conditions.

Some aspects of flox-methane rocket engine throttling

Abstract: Four injector designs and two chamber profiles were experimentally evaluated for structural integrity, combustion efficiency, and resistance to combustion instabilities. Vacuum thrust measurements were used as a primary measure of combustion efficiency. Stability rating to test the sensitivity of the injectors to high frequency combustion was conducted, but not extensively. To map the boundary between stable operation and chugging instability, chamber pressure was throttled downward from 689.5 to 206.9 kN/sq m abs (100 to 30 psia). Best operational results were obtained with an injector configuration having no hydraulic swirlers, a 0.00102-m (0.040-in.) recessed FLOX tube, and a nonflared exit in the methane annulus. This injector design exhibited stable combustion and good integrity of hardware, and it exceeded the design goal efficiency (88 percent) at the 10 to 1 throttled condition.