Chamber pressure

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

Analysis of indicator diagrams of a water injected twin-shaft screw-type expander.

Abstract: Twin-shaft screw-type expanders offer a high potential for energy conversion in the lower and medium power range, for instance as expansion engines in Rankine cycles for exhaust heat recovery. With regard to minimizing internal leakages and lubricating moving machine parts, an auxiliary liquid or liquid working fluid, for example in organic Rankine cycles (ORC)1, can be fed to the screw expander. In this paper, indicator diagrams of a twin-shaft screw-type expander prototype SE 51.2 designed at the Chair of Fluidics at TU Dortmund University are presented and analyzed in detail. The experimental investigations are carried out on a hot-air test rig with an expander inlet manifold water injection. The time-dependent working chamber pressure is recorded by means of high-resolution absolute pressure transmitters. Hereby, specific aspects of working chamber pressure measurements are mentioned. Based on the indicator diagrams, relevant influence mechanisms on the expander's operational behavior resulting from water injection are determined. Additionally, the impact of the injected water on the expander’s delivery rate and mechanical efficiency is presented.

Method and apparatus for melting and pouring specialty metals

Abstract: Specialty metals and alloys are melted in a crucible typically holding no more than about 100 lbs. of the metal and disposed in a furnace the interior of which is filled with a desired, e.g. inert, gas and subjected to a vacuum in the range of about 5% to 32% of atmospheric pressure. For special circumstances, it would be possible to start in the specified pressure range and then increase the melt chamber pressure to atmospheric or above. The vacuum permits the initiation and formation of long electric discharge arcs between the electrode of an immovable plasma torch mounted to the furnace and the inside of the crucible to provide enough space for charging of the crucible with fresh metal laterally through a charge opening in the upright side wall of the furnace and a vacuum chamber operatively connected with the charge opening. The melted metal is drained from the crucible through a drain hole in the bottom into molds which typically have close to the desired finished shape of the article and which can be removed from the furnace without the need to break the vacuum therein. A skull forming along the inside surfaces of the crucible is lifted off the crucible surfaces after each pour with a closure plate that is pushed from below into the drain hole. The skull is then melted with the plasma torch so that resulting melted metal collecting in the drain forms a drain plug upon solidification.

p-Channel and n-Channel Thin-Film-Transistor Operation on Sprayed ZnO Nanoparticle Layers

Abstract: Both n-channel and p-channel thin-film transistors have been realized on ZnO nanoparticle (NP) layers sprayed onto quartz substrates. In this study, nitrogen-doped ZnO-NPs were synthesized using an arc-discharge-mediated gas-evaporation method that was recently developed. Sprayed NP layers were characterized by scanning electron microscopy and Hall effect measurements. It was confirmed that p-type behaving NP layers can be obtained using ZnO-NPs synthesized with lower chamber pressure, whereas n-type conductivity can be obtained with higher chamber pressure. pn-junction diodes were also tested, resulting in clear rectifying characteristics. The possibility of particle-process-based ZnO-NP electronics was confirmed.

Efficient Thrust Distribution with Adaptive Pressure Control for Multinozzle Solid Propulsion System

Abstract: An integrated approach for chamber pressure control and thrust distribution for multiple nozzles of a solid propulsion system is presented. In this study, a solid propulsion system with variable nozzle throat area controlled by a pintle actuator is considered. To keep the hardware configuration simple and lightweight, multiple nozzles share a combustion chamber. Consequently, changing the throat area of one nozzle results in an unintended change of chamber pressure and thrust from other nozzles. Therefore, pressure stabilization and thrust distribution for multiple nozzles should be conducted simultaneously to achieve the desired performance. For the inner control loop, an adaptive sliding mode controller with feedback linearization is used for pressure stabilization. With the pressure control loop working properly, a thrust distribution algorithm into 10 nozzles for translation and attitude maneuver is developed as an outer control loop.

Experimental study of helium leakage parameters in flexible composite

Abstract: The helium leakage characterizations of flexible composites are experimentally studied in this article. Three data processing techniques (Defining method, Fourier series method, and Fast series method) are used to evaluate the helium leakage parameters including the diffusion coefficient D, the solubility S, and the permeant rate k. The chamber pressure variation for helium permeation in flexible composite is measured by the differential pressure method. The results indicate that Fast series method is an effective technology in extracting the helium leakage parameters for flexible composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010