Chamber pressure

About: Chamber pressure is a research topic. Over the lifetime, 2988 publications have been published within this topic receiving 30725 citations.

Method for predicting the optimum transition between constant and sliding pressure operation

Abstract: A method for improving operational efficiency of a partial-arc steam turbine power plant during power output variations by dynamically adjusting valve point values during turbine operation. Impulse chamber pressure at each of a plurality of valve points is first determined during operation of the steam turbine at constant pressure. For each adjacent pair of valve points, an optimum constant pressure transition point pressure for transitioning from one to the other of the sliding pressure mode and constant pressure mode is then computed. The optimum constant pressure transition point pressure for each pair of valve points is converted to a corresponding percentage of the pressure difference between the adjacent pairs of valve points. The impulse chamber pressure at each valve point is then used to calculate a corresponding impulse chamber pressure for transitioning from the one mode to the other mode based upon the percentage pressure difference. The calculated impulse chamber pressures for transitioning are compared to measured values of impulse chamber pressure and the system force transition from one of the modes to the other mode when the measured value is substantially equal to the calculated transition pressure.

Control system and method of controlling ion nitriding apparatus

Abstract: A control system and method for an apparatus to glow discharge treat (such as ion nitride) a workpiece. The apparatus includes a housing to receive a workpiece and a low pressure atmosphere of ionizable gas (nitrogen and hydrogen for nitriding), and connectors for establishing a glow discharge in the gas with the workpiece connected as the cathode. The control system and method automatically control the apparatus throughout the process, utilizing operator selected parameters (such as warm-up time, processing time, workpiece operating temperature and chamber pressure). The control system divides the selected operating temperature by the selected warm-up time to provide a straight line increase per unit time of the workpiece temperature. Initially the control system accumulates the increases at a rate higher than the straight line increase and then, as the workpiece approaches the selected operating temperature, the control system accumulates the increases at a rate less than the straight line increase. This provides a profile of the desired workpiece temperature. The control system compares the accumulated increases with the measured workpiece temperature and compares the rate of change of the accumulated increases with the rate of change of the measured workpiece temperature. It adjusts the level of electrical energy being supplied to the glow discharge in accordance with the comparison results. When the operator selected operating temperature is reached the control system terminates the profile and operates to maintain that temperature. The control system divides the selected operating pressure by the selected warm-up time to provide a profile of increasing pressure per unit time during warm-up and operates to provide the desired pressure at any time.

Experimental investigation of a metallized cryogenic hybrid rocket engine

Abstract: Hybrid propulsion systems offer many attractive characteristics such as their inherent simplicity, safe and inexpensive operations, environmentally friendly exhaust, and the capability for throttling. However, the slow burning nature of the classical hybrid fuels requires complex grain geometries and relatively large initial port volumes to achieve the required surface area for producing sufficient fuel mass flow rates, and consequently, thrust levels. Substantial increases in hybrid regression rates could eliminate the need for these complex geometries and would enable more efficient volumetric loading of the fuel through a reduction in both initial port volume requirements and grain sliver mass at burnout. Orbital Technologies Corporation has addressed these issues by the development and testing of a new class of cryogenic hybrid rocket engines that regress 20 to 40 times faster than conventional HTPB-based fuels. Many different hybrid propellant combinations have been tested. This paper focuses on subscale SCHVGOX and SCHt-Al/GOX hybrid development that was conducted under a Phase II NASA/LeRC SBIR. The objectives of the program were to: (1) research the liquid to solid fuel grain formation process, (2) research the gas to solid fuel grain formation process, (3) conduct parametric testing of SCHt/GOX and SCEU-Al/GOX hybrids, and (4) investigate the effects of different types and amounts of aluminum loading. The major findings were: (1) the SCHVGOX and SCHt-AyGOX hybrid firings exhibit smooth, relatively flat and predictable chamber pressure traces, (2) the SCEL^/GOX and SCHt-Al/GOX hybrids obey the classical hybrid regression law and have a similar dependence on mass flux as HTPB-based fuels, but regress 10-20 times faster, (3) as the percent of Al in the grain was increased, the hybrid regression rate decreased, and (4) reducing the initial temperature of SCH4 grains reduces the fuel regression rate. In addition to exhibiting extremely high regression rates, these propellant combinations offer substantial increases in * Member AIAA f Associate Fellow AIAA * Senior Member AIAA * Member AIAA Isp compared to classical hybrid fuels, and are competitive alternatives to bi-propellant and solid propulsion systems. Potential applications include: upper stages, orbit transfer, planetary ascent/decent, and launch vehicles. TEST ENGINES AND SUPPORTING HARDWARE Two hybrid engines were developed and tested during the program. A Low-Cost Hybrid Engine/Freezer was used to research the liquid to solid grain formation process and investigate the effects of different Al loadings. ORBITEC's Mark II engine was used to research the gas to solid fuel formation process and to conduct SCHt/GOX and SCH»Al/GOX firings. The concept behind the Low-Cost Cryogenic Hybrid Engine was to keep it simple, inexpensive, and versatile. This was accomplished by making the main engine components from off-the-shelf pipe fittings. A schematic and photograph of the hardware are shown in Figures 1 and 2, respectively. The engine chamber consisted of a 5-cm ID pipe surrounded by a coolant bath open to the atmosphere. A 5-cm pipe coupling welded to the center of the base plate allowed the main chamber to be screwed into the top and the aft chamber to be screwed into the bottom. A pipe cap with threaded ports for the ignitor, main oxygen, and pressure transducer, screwed onto the top of the main chamber and a copper heat sink nozzle screwed onto the aft chamber. An insulation ring surrounded the coolant bath. The main oxygen, ignitor oxygen, and ignitor methane solenoid valves along with the ignitor glow plug were all computer controlled with ORBrrEC's flexible computer control system. The computer recorded event timing and chamber pressure. A schematic of the Mark II Engine is shown in Figure 3. The engine is encased in a vacuum chamber to Copyright © 1998 by Orbital Technologies Corporation (ORBITECTM) Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. 1 American Institute of Aeronautics and Astronautics allow the radiation shield (not shown) to function. A coolant (LHe or LN2) fills the outer engine dewar and chills the wall of the center tube. The methane gas is admitted into the chamber which is maintained at a pressure below the methane triple point, causing the methane gas to freeze directly onto the inner wall of the center tube. When the engine is ready to fire, the inner chamber is exposed to an atmospheric GHe purge and then an ignitor flame. Gaseous oxygen is then injected at the top of the grain. The firing begins and the grain is depleted over time, producing a hot gas emission/thrust. Figure 4 shows the side view of the Mark-II system located in ORBITEC's test facility. All event timing and data acquisition were computer controlled using ORBITEC's cryogenic touchscreen control system.

Parameter study of the axisymmetric hydromechanical deep drawing process

Abstract: In this paper, hydromechanical deep drawing and the effect of process parameters on the process have been studied using the finite element (FE) method. In order to verify the results of FE simulations, a study has also been carried out using experimental tooling. Numerical results indicate a working zone with a maximum chamber pressure in which the maximum limit drawing ratio (LDR) can be achieved and where the effect of chamber pressure on the process can be shown. Also, the effect of parameters such as initial chamber pressure, die profile radius, blank thickness, and friction effect has been investigated. It is shown that initial chamber pressure has an optimum value in which the maximum LDR can be achieved. Increasing the die profile radius increases the LDR at lower chamber pressures but has no marked effect at higher pressures. The numerical result also shows that increasing the friction between blank and die or blank and blank-holder decreases the LDR value, while increasing the friction between blank and punch increases the LDR value.

Large area spray cooling by inclined nozzles for electronic board

Abstract: To cool a 1 kW 6U electronic card, an innovative inclined spray chamber with multiple nozzles has been developed and investigated with a closed-loop refrigeration system. A large heated surface (12.3 × 15.5 cm2) was sprayed by four gas-assisted nozzles with an inclined angle of 39° relative to the normal direction. A reasonable spray coverage area can be obtained by the inclined spray chamber while enabling a relatively lower spray chamber height than that required by a normal spray chamber. R134a was implemented as the working fluid in this study. The mass flow rate, pressure drop across the nozzles, and the spray chamber pressure were varied experimentally, and the results suggest that the increases of the mass flow rate, the pressure drop across the nozzles, and the spray chamber pressure can improve the thermal performance of the inclined spray. The average heated surface temperature can be maintained within 20.0°C, and the maximum heat transfer coefficient of 4742.2 W/m2·K can be achieved at a suitable working condition.