反压对超燃冲压发动机隔离段内流场的影响

Influence of Back Pressure on the Inner Flow Field in Scramjet Isolator

结合燃烧室工作稳定性的问题,采用FLUENT6.2软件对轴对称等截面隔离段的内流场进行了数值模拟,分析了当来流马赫数Ma=2时通过改变反压条件来研究其对不同长高比等截面隔离段激波串起始位置、结构以及性能的影响。结果表明:反压对隔离段内的激波串具有"前传"模式,促使激波串结构复杂和隔离段出口畸变度降低;隔离段长高比对反压与激波串的起始位置之间的关系有非常大的影响,当长高比不是非常大(5<L/D<9.667)时,激波串起始位置与反压呈线性关系,且变化快慢与长高比成正比,当长高比超过此范围后,线性关系不再成立。

Isolator is a key component of Scramjet in achieving dual - mode and mode transition, and it separates the inlet from the combustion chamber, thus preventing the effect of combustion back pressure on the inlet and guaranteeing the security and stabilization of aircraft. Combined with the problem of combustion chamber work stability, a numerical simulation of axial symmetry isolators with same cross section is performed with FLUENT6.2. When the Mach number of the inflow is 2, isolator with different ratios of length to height is investigated and the influence of back pressure on the location and structure of the shock train and on the performance of the isolator is analyzed. The results show that the back pressure has ahead transmission on the shock train of the isolator, which resuits in the complexity of the shock train structure and the decrease of the outlet distortion degree. The ratio of length to height has a great influence on the correlation between the location of the shock train and the back pres- sure. If the ratio of length to height is not too high, the location of the first shock wave will have a linear relation with the back pressure, and the changing speed is in direct proportion to the ratio of length to height. Otherwise, the linear correlation will not hold true.