Chamber pressure

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

Method and apparatus for pressure and mix ratio control

Abstract: The present invention provides apparatus and method for controlling mix ratio of gas supplied to a processing chamber integrated with chamber pressure. In one embodiment, an integrated controller is used to adjust mix ratio and chamber pressure. In one embodiment, the mix ratio and chamber pressure may be adjusted using a flow sensor and a control valve disposed in each gas supply line. In one embodiment, the flow sensor used in each gas supply line is insensitive to upstream pressure perturbations.

An ultrasonic fuel regression rate measurement technique for mixture ratio control of a hybrid motor

Abstract: A method for real-time control of mixture ratio and chamber pressure in a hybrid motor using an ultrasonic pulse-echo technique is discussed. The technique allows rapid sequential measurement of fuel web thickness during motor operation at multiple combustion port axial locations, thereby enabling direct computation of instantaneous fuel regression rate, fuel flow rate, and, ultimately, motor operating mixture ratio. Using such data, oxidizer flows into motor combustion ports and the aft mixing chamber of a hybrid motor can be varied to achieve operation at a constant pressure and constant mixture ratio. This technique can be used to generate a constant enthalpy combustion gas environment useful for a variety of ablative material thermal response and characterization studies. In related work, the technique can provide accurate spatialltemporal regression rate histories to assist in anchoring computational fluid dynamics analytical models used for regression rate prediction. Methods of coupling ultrasonic transducers to the fuel grains of 11and 24-in. hybrid motors during motor operation, to image the regressing fuel surface with a portable ultrasonic regression rate analysis system, are discussed, and data resulting from system feasibility testing is presented. INTRODUCTION results in measuring regressing fuel or solid propellant surfaces in operating ramjets and solid rocket motors were reported using transducers operating at a frequency of 2.25 MHz to penetrate fuel or solid propellant web thicknesses of approximately 1.5 in. In the application discussed here, ultrasonic pulse-echo methods were developed to penetrate approximately 5 in. of a highdensity hybrid fuel and image the regressing fuel surface. The work was conducted as part of an initiative to develop a feedback control system for regulation of mixture ratio and chamber pressure in a hybrid motor for NASA's Large Scale Solid Rocket Combustion Simulator (LSSRCS) program (NAS~-39874).4 The objective of the LSSRCS program is to reproduce the nozzle throat aerothermodynarnic environment generated during solid rocket combustion by using a hybrid gas generator. To accomplish this task, both mixture ratio and combustion pressure must be controlled to specified levels during tests in the LSSRCS. These tasks may be best accomplished by providing real-time data on hybrid fuel consumption, which can be compared with instantaneous data for oxygen flow rate and motor pressure. A control system can then make adjustments to motor oxygen flow rate to ensure that both motor pressure and mixture ratio always remain within the tolerances desired for solid rocket combustion simulation. Combustion Simulation Use of ultrasonic techniques to measure the burning rate in solid rocket motors and fuel surface regression rate in solid fuel ramjets has been explored by ort tin^,' ~ r a i n e a u , ~ and ~ i j k s t r a . ~ Ultrasonic methods employed by these and other experimenters have been oriented toward furthering the understanding of motor internal combustion and grain burnback mechanisms. Good Figure 1 illustrates the conceptual operation of a constant-pressure, constant-mixture ratio hybrid gas generator. Given a specific fuel formulation, the general problem of constant enthalpy operation is one of varying the oxidizer flow rates to the fuel grain combustion ports (mOF) and aft mixing chamber (mOA) so as to maintain constant chamber pressure and mixture ratio as the throat

Sterilization method employing a circulating gaseous sterilant

Abstract: A sterilization method comprising subjecting a sterilization chamber to an initial vacuum and then introducing steam to increase chamber pressure. The introduction of steam is interrupted and the chamber is brought into communication with a solution in a gaseous sterilant generator. The mixture of gaseous sterilant and chamber atmosphere are continuously circulated whereby equilibrium is established and the material to be sterilized is subject to constant temperature, pressure, sterilant concentration, and relative humidity for a period of time sufficient for sterilization. Also disclosed is an apparatus capable of performing the sterilization method comprising a sterilization chamber in combination with a gaseous sterilant generator. Formaldehyde is the preferred sterilizing agent.

Splat microstructure of plasma sprayed cast iron with different chamber pressures

Abstract: Achieving a plasma sprayed cast iron coating containing graphite requires stringent control on spray parameters that synergistically influence the coating properties and thus the performance. The microstructure of cast iron splats greatly depends on spray parameters such as substrate temperature, chamber pressure, and spray distance. This paper presents the effect of chamber pressure on the splat microstructure, including oxides and graphite. At low chamber pressures, most splats exhibit a disk shape with high flattening ratios, whereas star-shaped splats extensively appear at high chamber pressures. Spraying at high chamber pressures causes the formation of pores and thick oxide zones at the splat/substrate interface, mainly due to the atmospheric gases, which are responsible for a decrease in splat adhesion. Spraying in Ar atmosphere reduces the splat oxidation due to a decrease in the oxygen partial pressure. Small deformed substrate ridges are observed adjacent to the periphery of splats sprayed at low chamber pressures whereas no ridges are detected at high chamber pressures. Ridge formation generates a kind of mechanical bond, which increases the adhesive strength. Since the molten droplets impinge with high velocity and thus high flattening ratio at low chamber pressures, the solidification rate becomes faster, and graphite formation is resultantly hindered.