Aiming at calculating and studying the flow field characteristics of engine exhaust plume and comparative analyzing the effects of different chemical reaction mechanisms on the engine exhaust plume flow field characteristics, a method considering fully the combustion state influence is put forward, which is applied to exhaust plume flow field calculation of multinozzle engine. On this basis, a three-dimensional numerical analysis of the effects of different chemical reaction mechanisms on LOX/ kerosene engine exhaust plume flow field characteristics was carried out. It is found that multistep chemical reaction can accurately describe the combustion process in the LOX/kerosene engine, the average chamber pressure from the calculation is 4.63% greater than that of the test, and the average chamber temperature from the calculation is 3.34% greater than that from the thermodynamic calculation. The exhaust plumes of single nozzle and double nozzle calculated using the global chemical reaction are longer than those using the multistep chemical reaction; the highest temperature and the highest velocity on the plume axis calculated using the former are greater than that using the latter. The important influence of chemical reaction mechanism must be considered in the study of the fixing structure of double nozzle engine on the rocket body.
Thermoacoustic instability of n-decane at subcritical pressure in a small-scale channel is investigated from three aspects: the flow pattern, the fluctuations of temperature and pressure, and the dynamic model. The results show that the thermoacoustic instability is a type of dynamic instability and experiences three stages: that is, appearance, development, and disappearance. Oscillations happen for the pressure drop, fluid temperature, and wall temperature when thermoacoustic instability appears. The thermoacoustic instability is driven by a positive and a negative feedback. When the outlet oil temperature reaches saturation temperature, the positive feedback loop is on, and the thermoacoustic oscillation happens. After that, the flow pattern near the outlet recovers to annular flow and then transforms to a single-gas flow, which leads the thermoacoustic oscillation to happen again.
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