氢气超音速燃烧非定常过程数值模拟

A NUMERICAL SIMULATION OF UNSTEADY SUPERSONIC COMBUSTION WITH TRANSVERSE HYDROGEN

关键词:  超音速燃烧  冲压喷气发动机  非定常流  数值模拟

Key words:  Supersonic combustion  Ramjet engine  Unsteady flow  Numerical simulation

摘要:

用有限差分法求解二维Ｎ－Ｓ方程和组分守恒方程，使用代数涡粘性湍流模型，两步化学反应模型和ＭａｃＣｏｒｍａｃｋ时间分裂法，模拟超音速气流中横喷氢气自动着火及火焰传播过程，清晰地描述了喷氢、火焰传播到主流、稳定燃烧过程中，温度、压力、速度和油气当量比的变化。计算结果表明，高温附面层和喷嘴前回流区能促使氢气自动着火，进口气流的静温是火焰向主流传播的重要影响因素。计算还证明了喷嘴后氢与空气两股流呈现平行流动，其间存在着强烈的湍流交换和化学反应边界层，超音速燃烧效率则主要取决于两股气流的混合速率。

Abstract:

The processes of auto-ignition and combustion in supersonic air flow I with transverse hydrogen injection were calculated by means of the solution of two-dimensional N-S equations,using an algebraic eddy-viscosity model,a two-step global chemical model and MacCormack explicit timesplit method.The results stated clearly the variation of static temperature,static pressure,velocity and fuel-air equivalent ratio in the process from hydrogen injection,flame propagation to steadily combustion.The results also indicated that auto-ignition could occur in the thermal boundary layer and recirculation zone ahead of injector,and the static temperature of inlet air flow is a decisive factor which ef feets flame propagating from recirculation zone to turbulent mixing layer between air stream and hydrogen stream.The hydrogen stream in field behind injector is parallel to air flow,and there is strong turbulent mixing and reacting layer between them.Supersonic combustion efficiency is decided mainly by the mixing efficiency of these two streams.