Decrease Of Inlet Pressure Research Articles

Unsteady Two-Dimensional Nitrogen Flow in Long Microchannels with Uniform Wall Heat Flux

The time-dependent characteristics of pressure-driven nitrogen flow in long microchannels under uniform wall heat flux input are numerically studied. The two-dimensional momentum and energy equations are solved, with variable properties, rarefaction, involving velocity slip, thermal creep and temperature jump, compressibility, and viscous dissipation effects taken into account. Two cases of unsteady convection are studied. The first one arises due to a sudden heat flux change at the channel wall and the second due to a sudden inlet pressure change. The resulting thermal field and fluid dynamics are determined, described, and discussed in detail. The approach to steady-state conditions and the overall transient response are investigated. It is found that the transient response for the case with a sudden increase in wall heat flux input is slower than that for the case with a sudden decrease in wall heat flux input. The transient response for the case with a sudden increase in inlet pressure is much faster than that for the case with a sudden decrease in inlet pressure. These trends are quantified and discussed on the basis of the underlying transport mechanisms. The difference in overall transient response is caused by the flow rate change and the energy taken up by the pressure work.

ロケットエンジン用ターボポンプの入口配管の音響効果を考慮したキャビテーションサージの一次元解析 : 第1報,変動周波数の不連続性(流体工学,流体機械)

In a liquid rocket engine, cavitation in the inducer of a turbopump sometimes cause instability phenomena when the inlet pressure of the inducer is decreased. Cavitation surge, one such instability phenomenon, has been discussed mainly in connection with an inertia model. When such a model is used, the frequency of oscillation changes continuously as the inlet pressure decreases. However, we obtained interesting data on an experimental turbopump that showed that the surge frequency changed disconnectedly. With the aim of explaining this phenomenon, we conducted a one-dimensional analysis applying an acoustic model, combining the inlet pipeline with the sonic velocity of liquid oxygen. It was found that this phenomenon is a kind of self-excited vibration coupling the cavitation characteristics with the acoustic resonance of the inlet pipeline. Furthermore, as the inlet pressure decreases, the characteristic of the turbopump changes from a closed boundary condition to an open boundary condition, the frequency of the cavitation surge slightly decreasing.

1116 ロケットエンジン用ターボポンプ試験設備における音響効果を考慮したキャビテーションサージの1次元解析(OS11-3 流体機械の諸問題,オーガナイズドセッション)

In a liquid rocket engine, cavitations around the inducer of the turbopump sometimes cause the instability phenomena when the inlet pressure decreases. The cavitation surge, one of the instability phenomena, has been discussed mainly "the inertia model". A data of the surge mode oscillation on a experimental turbopump in JAXA showed that its frequency was not changed continuously related to the decrease of inlet pressure, but changed disconnectedly. In this article, aiming at explaining this phenomena, an one-dimensional analysis is examined applying "an acoustic model" combined the inlet line with the sonic velocity of liquid oxygen.