燃料射流隔板对受限超声速反应混合层流场和燃烧特性影响

Effects of Fuel Injector Clapboard on Flow and Combustion Characteristic of Confined Supersonic Reacting Mixing Layer

关键词:  燃料  射流  超声速流动  燃烧  隔板  回流区  混合层  流场

Key words:  Fuel  Injection  Supersonic flow  Combustion  Clapboard  Recirculation zone  Mixing layer  Flow field

摘要:

为了研究燃料射流隔板壁面扰动对于受限超声速反应混合层流场和燃烧特性的影响，基于抽象物理模型激波和膨胀波理论推演，得到了隔板诱发壁面扰动下的受限超声速反应混合层流场结构，并采用数值模拟方法进行了验证。数值结果表明，隔板诱发壁面扰动下的受限超声速反应混合层流场主要由冷态主导，且相对无隔板扰动多了回流区、激波、膨胀波、波与反应混合层相互作用等复杂现象。在此基础上，对于不同隔板厚度计算的结果表明，随着隔板厚度的增加，隔板下游的回流区增大，上下膨胀产生的压力不平衡加剧，反应混合层会产生偏斜，回流区厚度和偏斜距离与隔板厚度成正比。此外，第一道反射激波存在降低点火延迟的作用，且存在一个隔板厚度阈值，阈值以下随着厚度增加点火延迟随之降低。同时，后续的多道反射激波导致混合层发展的局部起伏和局部燃烧增强。

Abstract:

In order to study the effects of wall disturbance caused by fuel injector clapboard on the flow field and combustion characteristics of the confined supersonic reacting mixing layer， a theoretical deduction based on abstract physical model and wave theory is conducted. The flow structure of the confined supersonic reacting mixing layer is obtained. The theoretical analysis is verified by numerical simulation. The numerical results show that the flow field structure in the confined supersonic reacting mixing layer is dominated by the cold flow， and additional complex flow phenomenon such as recirculation zone， shock/expansion wave and shock/mixing layer interaction have been included compared to the one with no wall disturbance. On this basis， the calculation results for different clapboard thickness show that with the increase of the clapboard thickness， the recirculation zone downstream increases， the pressure imbalance caused by the upper and lower expansion increases which leads to the deflection of reacting mixing layer. The length of the recirculation zone and the deflection distance are directly proportional to the thickness of the clapboard. In addition， the first reflected shock wave can promote the reduction of ignition delay， and there is a thickness threshold below which the ignition delay decreases with the increase of thickness. At the same time， the subsequent reflected shock waves in the duct lead to local fluctuation of mixing layer development and enhancement of local combustion.