Chamber pressure

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

A new generation of high performance engines for spacecraft propulsion

Abstract: Experimental data validating advanced engine designs at three thrust levels (5, 15, and 100 lbF) is presented. All of the three engine designs considered employ a Moog bipropellant torque motor valve, platelet injector design, and iridium-lined rhenium combustion chamber. Attention is focused on the performance, robustness, duration, and flexibility characteristics of the engines. It is noted that the 5- and 15-lbF thrust engines can deliver a steady state specific impulse in excess of 310 lbF-sec/lbm at an area ratio of 150:1, while the 150-lbF thrust engines deliver a steady state specific impulse of 320 lbF-sec/lbm at an area ratio of 250:1. The hot-fire test results reveal specific impulse improvements of 15 to 25 sec over conventional fuel film cooled columbium chamber designs while operating at maximum chamber temperatures.

Constant pressure end burning gas generator

Abstract: End burning gas generators for use either as propulsion systems or means for generating large volume of gases for various purposes such as the generation of the fuel for a ducted rocket engine, the rapid inflation of air bags for personal protection or recovery of submersed items or the expulsion of projectiles from subsurface launch tubes are currently widely utilized. End burning gas generator grains are ignited at one end of a generally cylindrical charge mounted within a combustion chamber which is fixed with a suitable exhaust means. For many of the applications described above, it is desirable that the gas generator burn in a uniform manner such that a constant volume of gas is generated per unit of time so that the chamber pressure and the mass flow rate of gas remain constant. It has been observed, however, that rather than regressing at a uniform rate, the propellant grain burns in a manner which produces a convex cone, the angle of which increases with time thereby causing the burning surface to increase with time and to result in a progressive pressure trace within the combustion chamber and a corresponding continually increasing mass flow rate through the nozzle. According to this invention, it has been found that an end burning propellant grain can be caused to produce a substantially uniform pressure trace throughout its burn time if the interface between the grain and its container has a length greater than the axial length of the grain. The relationship between the length of the interface and the length of the grain is selected to compensate for the increased burning rate which is observed to occur at the interface and which produces the coning effect. The increased interfacial length can be easily obtained by the use of the corrugated member between the propellant grain and the case, the length across the corrugations providing the increase over the axial length of the grain. For typical gas generator propellant compositions, it has been found that if the interface is between 1.4 and 1.6 times the axial length of the grain that a substantially uniform pressure trace can be obtained. The corrugated interface also acts to improve the bond strength between the grain and the case.

Impact of chamber pressure and material properties on the deformation response of corneal models measured by dynamic ultra-high-speed Scheimpflug imaging.

Abstract: PURPOSE: To study the deformation response of three distinct contact lenses with known structures, which served as corneal models, under different chamber pressures using ultra-high-speed (UHS) Scheimpflug imaging. METHODS: Three hydrophilic contact lenses were mounted on a sealed water chamber with precisely adjustable pressure: TAN-G5X (41% hydroxyethylmethacrylate/glycolmethacrylate, 550 µm thick), TAN-40 (62% hydroxyethylmethacrylate, 525 µm thick) and TAN-58 (42% methylmethacrylate, 258 µm thick). Each model was tested five times under different pressures (5, 15, 25, 35 and 45 mmHg), using ultra-high-speed Scheimpflug imaging during non-contact tonometry. 140 Scheimpflug images were taken with the UHS camera in each measurement. The deformation amplitude during non-contact tonometry was determined as the highest displacement of the apex at the highest concavity (HC) moment. RESULTS: At each pressure level, the deformation amplitude was statistically different for each lens tested (p<0.001, ANOVA). Each lens had different deformation amplitudes under different pressure levels (p<0.001; Bonferroni post-hoc test). The thicker lens with less polymer (TAN-G5X) had a higher deformation (less stiff behavior) than the one that was thinner but with more polymer (TAN-40), when measured at the same internal pressure. The thinnest lens with less polymers (TAN-58) had a lower deformation amplitude (stiffer behavior) at higher pressures than the thicker ones with more polymer (TAN-40 and TAN-G5X) at lower pressures. CONCLUSIONS: UHS Scheimpflug imaging allowed for biomechanical assessment through deformation characterization of corneal models. Biomechanical behavior was more influenced by material composition than by thickness. Chamber pressure had a significant impact on deformation response of each lens.