高速进气道低马赫数不起动特性及马赫数影响规律

Unstart Characteristics of High Speed Inlet at Low Mach Number and Influence Law of Mach Number

关键词:  高速进气道  低马赫数不起动  非定常  气动力  自起动

Key words:  High speed inlet  Low Mach number unstart  Unsteady  Aerodynamic force  Self-start

摘要:

为了探究进气道低马赫数不起动时的振荡特性，本文结合一体化前体/进气道构型，通过非定常仿真手段，对比研究了来流马赫数变化对进气道低马赫数不起动振荡流场以及飞行器气动力的影响规律。结果表明：低马赫数不起动时出现了稳定的振荡周期，且周期随着来流马赫数的增大而增长。由于拥塞发生在喉道处，其振荡流场单纯地表现为口部分离包的涨大和缩小，并且沿程压力的均值和幅值都呈现出喉道高两头低的分布趋势，而马赫数的增大会加剧此趋势。喘振周期中升力系数C_L和阻力系数C_D的变化趋势大致相反，升阻比曲线则表现为随分离包吐出而增大、吞入而缩小的趋势。C_L和C_D随着马赫数增大是整体下降的，但是脉动幅值变化不大，升阻比对马赫数的变化也并不敏感。此外，在进气道实现自起动过程中，当喉道瞬时流量高于起动时的流量一定程度，口部分离包将完全吞入。但定常仿真难以准确模拟该吞入过程，因此定常仿真得到的自起动马赫数偏高。

Abstract:

In order to explore the oscillation characteristics of the inlet unstart induced by the low Mach number inflow， an unsteady simulation study of a specific integration of the forebody and the inlet was carried out. A comparison of the oscillation flow field and the aerodynamic force of the aircraft under different incoming Mach numbers were performed. The results show that a stable periodic oscillation appears when the inlet is unstart at the low Mach number. And the cycle length of the periodic oscillation increases with the increase of the incoming Mach number. Due to the throttling in the inlet throat， the oscillation flow field can be divided into two stages， which are the increasing and decreasing stages of the separation bubble in the throat. Meanwhile， the distribution trends of the mean and amplitude of the pressure along the tunnel both exhibit high at throat and low at both ends. And the increase of inflow Mach number will increase such trend. In the oscillation period， the variation trends of the lift coefficient C_L and the drag coefficient C_D are quite different， while the lift drag ratio curve is manifested as the trend of increasing with the throwing up of the separation bubble and decreasing with the swallowing of the separation bubble. C_L and C_D decrease with the increase of Mach number， but the amplitude of pulsation changes little， and the lift drag ratio is not sensitive to the change of Mach number. C_L and C_D both decrease with the increase of Mach number， but the amplitude of oscillation changes little. And the lift-drag ratio is not sensitive to the change of Mach number. In addition， in the process of self-starting， it is found that once the instantaneous flow in the throat is higher than that in the starting to a certain extent， the separation bubble at the throat can be swallowed completely. Because the swallowing process cannot be simulated by the steady simulation accurately， the self-starting Mach number obtained by the steady simulation is higher.