激波风洞流场建立过程对进气道流动的影响

Effects of Flow Field Establishment Processof Shock Tunnel on Inlet Flow

关键词:  高超声速进气道  脉冲起动  激波风洞  喷管起动  初始间断面

Key words:  Hypersonic inlet  Pulse-starting  Shock tunnel  Nozzle starting  Initial discontinuity

摘要:

由于激波风洞喷管起动与进气道起动相“耦合”的流动过程复杂，喷管起动过程中的波系结构对进气道脉冲起动过程的影响规律难以准确把握。本文从简化问题的研究思路出发，将激波风洞喷管流动与进气道流动进行一定程度的“解耦”，以揭示喷管起动波系各组成部分对进气道脉冲起动过程的影响机制。“解耦”方法先采用准一维变截面非定常流动模拟激波风洞喷管的起动过程；然后，将喷管出口参数作为来流条件，对二元进气道的脉冲起动过程进行非定常粘性数值模拟。采用“解耦”方法考察了初始压强对喷管起动波系以及进气道脉冲起动的影响，并与不考虑喷管起动过程，在进气道入口设置初始间断面的模拟方法进行了比较。结果表明，喷管起动波系中的非定常膨胀波和二次激波是影响进气道脉冲起动的主要因素。在初始压强较低时，采用在进气道入口设置初始间断面的方法，可以快速评估进气道的脉冲起动能力；而当初始压强较高时，采用本文的“解耦”方法模拟，能够得到更为可靠的脉冲起动能力。

Abstract:

Due to the complexity of the coupling process of a nozzle starting flow of a shock tunnel and an inlet starting flow， the effects of the starting shock system of the nozzle on the pulse-starting of the inlet have not been well investigated. To simplify the problem and reveal the mechanism of the inlet pulse-starting in a shock tunnel， the nozzle starting flow of the tunnel was decoupled from the inlet starting process to some extent. At first， the decoupling method adopts a quasi-one-dimensional unsteady flow solver of variable section duct to solve the nozzle starting process of a shock tunnel. And then， an unsteady viscous simulation is performed by setting the flow parameters at the nozzle exit as the inflow conditions of a two-dimensional inlet. The effects of the initial pressure on the nozzle starting process and the pulse-starting of the inlet were investigated by applying the decoupling method， and compared with that obtained by a method of setting an initial discontinuity at the inlet entrance without regard for?the nozzle starting process. The results indicate that the unsteady expansion waves and the secondary shock in nozzle starting process dominate the pulse-starting of the inlet. When the initial pressure is relatively low， a fast estimation of the ability to pulse-start can be performed by setting an initial discontinuity at an inlet entrance. However， when the initial pressure is relatively high， more reliable results of the pulse-starting ability of an inlet can be obtained by applying the decoupling method in the present paper.