Chamber pressure

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

Atomization characteristics on the surface of a round liquid jet

Abstract: Fundamental mechanisms of liquid jet breakup are identified and quantified. The quality of the atomization of liquids is an important parameter of many technological processes and is, e.g. for fuels and propellants critical in defining engine performance. This investigation takes a look at the jet behavior for a single injector element to determine the influence of the injection conditions on a round liquid jet. The study focuses on the atomization of a liquid forming a classical spray. To adjust the relative velocity between the liquid jet and the gaseous ambient a wind tunnel-like coaxial flow configuration was used. This made it possible to distinguish between effects of aerodynamic forces, chamber pressure and jet velocity, which determine the liquid Reynolds number and thereby the internal jet turbulence. Shadowgraphy and a novel image-processing approach was used to determine the jet surface characteristics: wavelength and amplitude. The absolute injection velocity of the jet seems to affect the structures the most with an increasing velocity causing the wavelengths to be smaller. An increase in chamber pressure seemed to have little influence on the jet with no relative velocity between the gas and liquid jet, but increased the amplitude and drop formation frequency at other testing conditions with relative motion. The wave amplitude trends provide information about the likelihood of drop formation but are limited in maximum size due to this breakup phenomenon of the jet. The study of the direction of the relative velocity demonstrated that injector performance cannot simply be described by scalar geometrical and operational injection parameters (e.g., We , Re or Oh), but has to include the injection direction of the atomizing fluids in relation to each other and to the ambient (e.g., combustion chamber). The undisturbed jet length and the spread angle were investigated, and a correlation for the droplet separation position was proposed. The data led to an extended classification of liquid jet breakup regimes. Large wave instabilities were experimentally analyzed and compared with linear stability theory.

Plasma-enhanced CVD process using TEOS for depositing silicon oxide

Abstract: A high pressure, high throughput, single wafer, semiconductor processing reactor is disclosed which is capable of thermal CVD, plasma-enhanced CVD, plasma-assisted etchback, plasma self-cleaning, and deposition topography modification by sputtering, either separately or as part of in-situ multiple step processing. The reactor includes cooperating arrays of interdigitated susceptor and wafer support fingers which collectively remove the wafer from a robot transfer blade and position the wafer with variable, controlled, close parallel spacing between the wafer and the chamber gas inlet manifold, then return the wafer to the blade. A combined RF/gas feed-through device protects against process gas leaks and applies RF energy to the gas inlet manifold without internal breakdown or deposition of the gas. The gas inlet manifold is adapted for providing uniform gas flow over the wafer. Temperature-controlled internal and external manifold surfaces suppress condensation, premature reactions and decomposition and deposition on the external surfaces. The reactor also incorporates a uniform radial pumping gas system which enables uniform reactant gas flow across the wafer and directs purge gas flow downwardly and upwardly toward the periphery of the wafer for sweeping exhaust gases radially away from the wafer to prevent deposition outside the wafer and keep the chamber clean. The reactor provides uniform processing over a wide range of pressures including very high pressures. A low temperature CVD process for forming a highly conformal layer of silicon dioxide is also disclosed. The process uses very high chamber pressure and low temperature, and TEOS and ozone reactants. The low temperature CVD silicon dioxide deposition step is particularly useful for planarizing underlying stepped dielectric layers, either alone or in conjunction with a subsequent isotropic etch. A preferred in-situ multiple-step process for forming a planarized silicon dioxide layer uses (1) high rate silicon dioxide deposition at a low temperature and high pressure followed by (2) the deposition of the conformal silicon dioxide layer also at high pressure and low temperature, followed by (3) a high rate isotropic etch, preferably at low temperature and high pressure in the same reactor used for the two oxide deposition steps. Various combinations of the steps are disclosed for different applications, as is a preferred reactor self-cleaning step.

Benchmark Wall Heat Flux Data for a GO2/GH2 Single Element Combustor

Abstract: Wall heat flux measurements in a 1.5 in. diameter circular cross-section rocket chamber for a uni-element shear coaxial injector element operating on gaseous oxygen (GOz)/gaseous hydrogen (GH,) propellants are presented. The wall heat flux measurements were made using arrays of Gardon type heat flux gauges and coaxial thermocouple instrumentation. Wall heat flux measurements were made for two cases. For the first case, GOZ/GHz oxidizer-rich (O/F=l65) and fuel-rich preburners (O/F=1.09) integrated with the main chamber were utilized to provide vitiated hot fuel and oxidizer to the study shear coaxial injector element. For the second case, the preburners were removed and ambient temperature gaseous oxygen/gaseous hydrogen propellants were supplied to the study injector. Experiments were conducted at four chamber pressures of 750, 600, 450 and 300psia for each case. The overall mixture ratio for the preburner case was 6.6, whereas for the ambient propellant case, the mixture ratio was 6.0. Total propellant flow was nominally 0.27-0.29 Ibm/s for the 750 psia case with flowrates scaled down linearly for lower chamber pressures. The axial heat flux profile results for both the preburner and ambient propellant cases show peak heat flux levels a t axial locations between 2.0 and 3.0 in. from the injector face. The maximum heat flux level was about two times greater for the preburner case. This is attributed to the higher injector fuel-to-oxidizer momentum flux ratio that promotes mixing and higher initial propellant temperature for the preburner case which results in a shorter reaction zone. The axial heat flux profiles were also scaled with respect to the chamber pressure to the power 0.8. The results at the four chamber pressures for both cases collapsed to a single profile indicating that at least to first approximation, the basic fluid dynamic structures in the flow field are pressure independent as long as the chamber/njector/nozzle geometry and injection velocities remain the same.

Flux Chamber Design and Operation for the Measurement of Municipal Solid Waste Landfill Gas Emission Rates

Abstract: This paper describes a hybrid Flux Chamber-Soil Gas Probe methodology for measuring municipal solid waste (MSW) gas emission rates. Following the design of the flux chamber, the chamber was laboratory tested to define its mixing characteristics and optimum operating parameter values. Flux chamber operating parameters included: chamber pressure, sweep air flow rate, landfill surface insertion depth, and sweep air velocity. Optimum operating parameter values were determined by operating the flux chamber on a simulated subsurface emission source and varying the operating parameters. The laboratory tests indicated that the flux chamber could be operated to provide zero biasing of gas emission rates, resulting in accurate measurement of gas emission rates.