超燃冲压发动机燃烧室的准一维计算与分析

Quasi-One-Dimensional Prediction and Analysis of Scramjet Combustor

关键词:  准一维Euler方程  有限速率化学反应  一步反应  超燃冲压发动机  燃烧室

摘要:

在考虑有限速率化学反应的准一维Euler方程基础上，通过增加截面面积变化、壁面摩擦和添质的源项，发展了适用于超燃燃烧室性能分析的准一维计算方法。依次以中国空气动力研究与发展中心（CARDC）和日本国家航空与航天实验室（NAL）的氢燃料燃烧室模型作为验证算例，分别采用传统的一步反应模型和发展的有限速率反应模型，模拟了燃烧室流场，并基于NAL燃烧室，计算分析了不同当量比和进口压强对燃烧室流动特性的影响。结果表明：两种方法都能得到与实验数据吻合良好的结果；和一步反应模型相比，有限速率反应模型不仅可以更细致地捕捉流场细节，而且能够初步分析化学非平衡效应的影响；对于NAL燃烧室，当量比≥0.6时，压强随当量比的升高而增大，当达到1.0时，反压已推进隔离段，且推进速度随当量比增大而增加；进口压强不大于110.444kPa时，反压随进口压强增大而升高，且当反压不小于82.833kPa时，反压被隔离在等直段燃烧室入口处；过小的当量比和过大的进口压强均会导致燃烧室出口马赫数严重下降，甚至出现亚声速出流状态。

Abstract:

Based on the quasi-one-dimensional Euler equations with finite-rate chemical reactions, a quasi-one-dimensional computational method for scramjet combustor performance analysis was developed by adding the source terms for the cross-sectional area variation, wall friction and fuel addition. One-dimensional numerical investigations of the hydrogen-fueled CARDC scramjet and NAL scramjet were simulated and compared with the common single-step reaction equilibrium model and our finite-rate reaction model. The characteristics of combustion flow field of the NAL scramjet under different hydrogen equivalence ratios and inlet pressures were also numerically simulated and analyzed. The results indicate that the accuracy and effectiveness of the two models are validated by good agreement between the predictions and experimental data. Furthermore, the finite-rate reaction model not only captures more details of the flow field, but also analyzes the effects of equivalent ratios, inlet pressures and other parameters. For the NAL scramjet, the pressure increases gradually as the equivalent ratio increases when the hydrogen equivalence ratio is not less than 0.6. The combustion induced back pressure begins to disturb into the isolator if the hydrogen equivalence ratio reaches 1.0, and the disturbing speed increases with the further increase of equivalence ratio. When the inlet pressure is not greater than 110.444kPa, the back pressure increases as the inlet pressure increases and when the inlet pressure is not less than 82.833kPa, the back pressure is isolated at the entrance of the straight section of combustor. An excessively small equivalent ratio and an excessively large inlet pressure can result in a serious decrease of the outlet Mach number, or even a subsonic outflow condition.