Showing papers on "Chamber pressure published in 1973"

Theoretical Analysis of Wankel Engine Combustion

Abstract: A one-dimensional model for. the spark ignition Wankel engine combustion is presented, The model is based on the use of a turbulent diffusivity for heat and mass transfer by which the motion of the finite-thickness, unsteady turbulent flame is calculated. A one-step second order reaction rate equation is used and wall heat transfer losses are included. The instantaneous chamber pressure and the local and instantaneous gas temperature, density, and velocity are calculated. Results are presented for a typical engine design. Initial results of two parametric studies are also reported, but their generalization is not undertaken, at this point, due to the complexity of the process.

Pneumatic flexible bumper

Abstract: A flexible, pneumatic bumper adapted for motor vehicle applications. A plurality of individual chambers are defined by a resiliently deformable outer bumper shell, a supporting plate secured to the vehicle structural members and a plurality of separator elements extending from the bumper shell and removably connected to the supporting plate. When the outer bumper shell is forced inwardly due to an impact force, resultant chamber deformation causes an increase in chamber pressure that is relieved by air being forced out of chamber through pressure relief valves that vent each chamber. Following impact, return of the bumper shell to its original shape is slowed by a restricted air flow into the chambers through the valves, thereby preventing bumper rebound forces.

Hydraulically powered impact device

Abstract: A hydraulic impact device has a hammer member carrying a piston which is reciprocally disposed in a cylinder chamber to form an expansible chamber. When the expansible chamber is pressurized, the hammer is retracted against an air spring or other energy storage device by the high pressure. A sleeve valve is reciprocally disposed in the cylinder chamber between the piston and the energy storage device and is held against the piston by an imbalanced fluid pressure as the hammer is retracted against the spring. When the piston and sleeve valve have been retracted to a predetermined position, high pressure fluid is ported between the sleeve valve and piston to hydraulically separate the two members. The chamber pressure is then equalized on both sides of the piston at the return line pressure so that the air spring can accelerate the hammer to deliver an impact blow to an anvil and thence a tool with minimum resistance to movement of the piston by the hydraulic fluid as the chamber pressure is reduced to return line pressure. The sleeve valve is then again moved downwardly against the piston member by an imbalanced pressure condition. When the sleeve valve moves downwardly and seats against the piston, the piston and sleeve are again retracted by the high pressure and the cycle is repeated. The chamber wall is shaped to provide a hydraulic cushion for the hammer near the end of its impact stroke and to provide a seat for the piston apart from the sleeve valve so that high pressure fluid is bypassed to reservoir until a predetermined load is placed on the hammer.

Dynamic Responses of Solid Rockets during Rapid Pressure Change

Abstract: Solid rocket performance during rapid pressure excursions differs greatly from predictions based on steady-state burning rate data. Rapid pressurization (150-250 kpsi/sec) following a sudden throat area decrease in a low L* combustor produces pressure overshoots of 10% and indicated burning rate overshoots in excess of 50%. A transient internal ballistics model was developed incorporating nonsteady continuity and energy equations for the chamber, nonsteady energy equation for the propellant condensed phase, and a modified Zeldovich heat feedback function for the propellant (which for the conditions considered is known to burn with a thin quasi-steady reaction zone). Sensitivity analyses using the model indicate that accurate surface temperature and temperature sensitivity data are needed. With reasonable estimates of surface reaction zone temperature and measurements of temperature sensitivity of burning rate, good agreement between the measured and the calculated p vs t was found for a nonmetallized composite propeliant in a low L* combustor. High pressure exponent, high temperature sensitivity of burning rate, high dAJdt, low burning rate, and low L* prominently increase the dynamic effects.

Accumulator with temperature compensation

Abstract: A vessel for storing fluid under pressure includes a housing having a chamber in one end thereof into which concentric pistons of differential areas are urged by resilient means. Admission of fluid under pressure to the chamber acts on the differential areas of the pistons moving them simultaneously against the resilient means until the pressure and volume of fluid respectively, each attains a first predetermined value, at which time the pistons are held against further movement, with the piston having the larger area being held against a fixed stop and the piston having the smaller area being held by the resilient means up to a second predetermined value of chamber pressure which represents the maximum fluid working pressure of the system to which the vessel is connected. Any pressure increase in the chamber above the second predetermined value, due to fluid expansion caused by temperature increase, is effective across the differential area between the concentric pistons so that as the chamber pressure exceeds the second predetermined pressure value the piston with the smaller area will move against the resilient means to compensate for volumetric increase.

Analysis of gas flow through a multilayer insulation system.

Abstract: A theoretical investigation of gas flow inside a multilayer insulation system has been made for the case of the broadside pumping process. A set of simultaneous first-order differential equations for the temperature and pressure of the gas mixture was obtained by considering the diffusion mechanism of the gas molecules through the perforations on the insulation layers. A modified Runge-Kutta method was used for numerical experiment. The numerical stability problem was investigated. It has been shown that when the relaxation time is small compared with the time period over which the gas properties change appreciably, the set of differential equations can be replaced by a set of algebraic equations for solution. Numerical examples were given and comparison with experimental data was made.

Pressure regulating valve assembly

Abstract: A pressure regulating valve assembly for use in an anti-skid brake control system in which a flow restrictor is provided between the pilot valve and the diaphragm valve of the valve assembly which is operable in a low brake chamber pressure range to provide a gradual re-application of brake pressure following the end of a skid.

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.

Optimum Design of Space Storable Gas/Liquid Coaxial Injectors

Abstract: Results from an experimental program are presented whose objective was to establish performance and chamber compatibility design criteria for circular coaxial injector concepts for application with the space storable gas/liquid propellant combination FLOX (82.6% F2, 17.4% O2)/CH4(g) at high pressure. The primary goal of the program was to obtain high characteristic velocity efficiency (77^ > 99%) in conjunction with acceptable injector/chamber compatilibity. Subscale (single-element) cold-flow and hot-fire experiments were employed to establish design criteria for a 3000 Ibf (sea level) engine operating at 500 psia. The subscale experiments characterized both high performance "core" elements and "peripheral" elements with enhanced injector/chamber compatibility. The full-scale injector which evolved from the study demonstrated a performance level of 99 % of the theoretical shifting characteristic exhaust velocity with low chamber heat flux levels. At the design condition (Pc = 500 psia), measured heat flux levels were approximately 2 to 3 Btu/in.2-sec in the graphite cylindrical chamber; the heat flux levels were predicted by initial program efforts with subscale, low-cost, single-element hardware. Full-scale injector durability was demonstrated during a 44-sec firing; additionally, dynamic stability was demonstrated by a 15-msec recovery to a 1100 psi chamber overpressure.

Hydraulic Flip Behavior in Typical Liquid Rocket Operating Regimes

Abstract: : An experimental investigation on hydraulic flip behavior at typical liquid rocket injector design and operating conditions was completed. Both nitrogen tetroxide and water were used as test fluids. The results were analyzed to show the effect of chamber pressure, orifice L/D, orifice diameter and cross-flow velocity on the occurrence of hydraulic flip. Comparison of experimental results with the theoretical models developed by Ito was made. It was concluded that chamber pressure and orifice L/D strongly affect the occurrence of hydraulic flip while orifice diameter and cross-flow velocity influence hydraulic flip to a much lesser degree. The theoretical models were found to be inadequate for predicting hydraulic flip. The conditions for the occurrence of flip appear nearly the same for both nitrogen tetroxide and water.

Area ratio excess flow shutoff valve system

Abstract: A spool of a normally open valve has an orificed passage for gas flow from a source chamber to a control pressure chamber. The spool has an area facing control pressure which exceeds the area of the spool facing source pressure. The spool is kept in its open position during normal operation because the product of control chamber pressure and spool area seeing the control chamber and normal to the axis of the spool is maintained equal to or greater than the product of source pressure and spool area seeing source pressure and normal to the axis of the spool. Downstream from the control pressure chamber, a second orifice maintains the pressure in the control pressure chamber during normal operation at a value great enough to keep the spool control area control chamber pressure product high enough to keep the valve open. When there is a leak, however, between the valve and the second orifice, the second orifice cannot maintain a sufficiently high control pressure and the product of source pressure and spool source area will exceed the offsetting product and the spool will move to a closed position preventing gas flow through the valve. The orifice in the spool assures that there will be sufficient pressure drop between the two chambers to cause the spool to close.

Investigation of Thermal Fatigue in Non-Tubular Regeneratively Cooled Thrust Chambers. Volume 2

Abstract: : Long life non-tubular teneratively cooled thrust chambers were fabricated and hot-fire cyclic tested to verify the life prediction techniques established in Volume I of this report. Chambers incorporating copper alloy (NARLoy-Z and zirconium copper) and nickel for the hot gas wall material and electroformed nickel closures were fabricated by Rocketdyne and hot fire cyclic tested by Rocketdyne and hot fire cyclic tested by the AFRPL. Propellants were LO2/H2 at a nominal mixture ratio of 6:1. Chamber pressure was 750 psia and thrust (corrected to vacuum and with a full area ratio nozzle) was 3300 pounds. A calorimeter thrust chamber assembly (calorimeter thrust chamber and coaxial injector) were also fabricated and hot-fire tested to establish the heat flux profile. Post-test analysis and metallurgical evaluation of the chamber were performed to locate and define fatigue cracks.

Attitude compensation method and system for ground-effect machines

Abstract: A ground-effect machine is designed for travelling along a bearing surface through the medium of a lift cushion system provided with a suspension system which includes a deformable pneumatic chamber interposed between the machine frame and the cushion proper. This cushion and this chamber have an associated fluid circuit which may comprise a passage intercommunicating them and which is so designed that the cushion pressure or lift pressure is, depending on the type of ground-effect machine, either greater or smaller than ambient pressure but in any event closer thereto than the pneumatic chamber pressure or suspension pressure.

Pressure and current effects on the thermal efficiency of an MPD arc used as a plasma source

Abstract: Measurements of arc voltage and energy loss to the cooled electrodes of a magnetoplasmadynamic (MPD) arc, operating without an applied magnetic field, were made at chamber pressures of 26 to 950 torr, argon mass flow rates of 0.08 to 44 g/s and current of 200 to 2000 A. The resulting arc thermal efficiency varied from 22% at a chamber pressure of 26 torr to 88% at 950 torr. Thermal efficiency was only weakly dependent on arc current. It is concluded that the MPD arc operating without an applied magnetic field and at higher pressure than normally used in thruster applications is a reliable and efficient steady-state plasma source.

A Study of Electrodeless Arc Discharge Using Argon, Nitrogen, and Air

Abstract: : A study of the bluff-body stabilized electrodless arc was undertaken to extend the operation to greater mass flow rates and power input. A small arc chamber, operating at a frequency of 3.5 MHz, was operated with mass flows up to 1.026 gm/sec of argon at atmospheric pressure with a power input of 6.79 KW. Under these conditions a plasma bulk temperature of 2305K was obtained with a heating efficiency of 18%. It was found that heating efficiency increased with chamber pressure, but bulk temperature depends primarily upon the power input. A larger arc chamber was designed for a nominal power input of 200 KW at a frequency of 377 MHz. This chamber was operated at mass flow rates up to 2.4 gm/sec of argon at a pressure of two atmospheres. A plasma bulk temperature of 5856K was obtained at a power input of 76KW. Attempted operation using air as a working fluid was unsuccessful at pressures in excess of 2/3 atmosphere due to inefficient coupling to the arc plasma.

An Experimental Investigation of a Vortex Stabilized Arc in an Axial Magnetic Field

Abstract: : An experimental program has been conducted to investigate the physical processes occurring in vortex stabilized arcs, with and without an applied axial magnetic field. Arc temperature measurements indicate centerline temperature to be insensitive to arc current and chamber pressure. Centerline temperature was found to decrease when arc length was increased, when orifice area was decreased and when axial magnetic field strength was increased. Magnetic field strength could only be increased to a 'critical' value, at which point the discharge moved off the centerline line of the chamber and attached to its walls. A stability criterion has been derived to estimate the strength of the critical magnetic field. Experimental data agrees very well with the derived expression.

Technique for predicting high-frequency stability characteristics of gaseous-propellant combustors

Abstract: A technique for predicting the stability characteristics of a gaseous-propellant rocket combustion system is developed based on a model that assumes coupling between the flow through the injector and the oscillating chamber pressure. The theoretical model uses a lumped parameter approach for the flow elements in the injection system plus wave dynamics in the combustion chamber. The injector flow oscillations are coupled to the chamber pressure oscillations with a delay time. Frequency and decay (or growth) rates are calculated for various combustor design and operating parameters to demonstrate the influence of various parameters on stability. Changes in oxidizer design parameters had a much larger influence on stability than a similar change in fuel parameters. A complete description of the computer program used to make these calculations is given in an appendix.

High pressure plasma-arc burner - with coolant pressure regulation

Abstract: A plasma arc burner in which the coolant supply to the burner is regulated by a control valve which maintains the coolant system press. at least equal to or above the burner chamber pressure. Control is effected through a pneumatic pressure controller to which chamber press. as a nominal value and coolant system press. as a measured value are supplied as inputs and in which the controller output is to the control valve regulating the gas supply pressurising the coolant supply tank. Coolant from the supply tank is circulated through a distribution manifold with flow and temp. measuring elements and returns to the tank via a return manifold and series linked heat exchangers with separate secondary cooling systems.

Press plunger speed control - in injection and compaction phases, for casting machines

Abstract: Press plunger speed and pressure control system, esp. for cold chamber pressure casting machines used in the mfr. of thin-walled and complicated workpieces, provides for only the face of the press plunger to be acted upon during the first phase (introduction of the pressing operation); during the second working phase the press plunger is acted upon by a second pressure line (during injection), and during the third working phase (compaction) the compressor piston is acted upon by a pressure line that is independent of the other pressure lines. The compression vol. of the compressor is directly connected to a pressure-variable storage unit for compressed pressure medium.

Regeneratively cooled rocket engine for space storable propellants

Abstract: Analyses and experimental studies were performed with the OF2 (F2/O2)/B2H6 propellant combination over a range in operating conditions to determine suitability for a space storable pressure fed engine configuration for an extended flight space vehicle configuration. The regenerative cooling mode selected for the thrust chamber was explored in detail with the use of both the fuel and oxidizer as coolants in an advanced milled channel construction thrust chamber design operating at 100 psia chamber pressure and a nominal mixture ratio of 3.0 with a 60:1 area ratio nozzle. Benefits of the simultaneous cooling as related to gaseous injection of both fuel and oxidizer propellants were defined. Heat transfer rates, performance and combustor stability were developed for impinging element triplet injectors in uncooled copper calorimeter hardware with flow, pressure and temperature instrumentation. Evaluation of the capabilities of the B2H6 and OF2 during analytical studies and numerous tests with flow through electrically heated blocks provided design criteria for subsequent regenerative chamber design and fabrication.

Experimental investigation of combustor effects on rocket thrust chamber performance

Abstract: The results are reported of a program to develop special instrumentation systems and engine hardware, conduct tests using LOX/GH2 propellants wherein radial mixtures ratio stratification was controlled, and subsequently compare the results of four selected tests with the predictions of the JANNAF performance-prediction computer programs. During the experiments, the overall propellant mixture ratio was varied from 4.4 to 6.6, while the mixture ratios in the core and outer zone were varied from 5.7 to 8.8 and from 3.7 to 7.2, respectively. A nominal 10 percent of the total fuel flow was used as boundary layer collant in a majority of the firings. Nominal chamber pressure was either 225 or 250 psia, with nozzle expansion ratios of either 25:1 or 4:1. Measurements of the axial chamber pressure and wall heat flux profiles, together with samples of the exhaust gas, were obtained. The corrected experimental specific impulse and characteristic exhaust velocity efficiencies were approximately 97.5 and 98.5 percent, respectively.