椭圆形超燃燃烧室内燃料喷射和掺混性能研究

Injection and Mixing Performance in an Elliptical Scramjet Combustor

关键词:  椭圆形燃烧室  横向喷流  壁面曲率  喷嘴直径  激波干扰  相似性

Key words:  Elliptical combustor  Transverse jet  Wall curvature  Injector diameter  Shock interaction  Similarity

摘要:

为了优化超燃燃烧室的工作效率和性能，针对椭圆形超燃燃烧室内的燃料壁面垂直喷射方案，通过求解雷诺平均Navier-Stokes方程的数值模拟方法对不同燃料喷射方案进行研究，着重分析了不同喷注位置的壁面曲率值、喷嘴直径以及反射激波干扰对流场特征及燃料掺混特性的影响。研究表明，喷注位置的壁面曲率对燃料掺混的影响程度与喷嘴直径相关。当喷嘴直径较大时，壁面曲率值越小，燃料的掺混效率越高，但总压恢复系数越低；当喷嘴直径较小时，壁面曲率的改变对燃料横向喷流方案的掺混效率和总压恢复影响很小。在相同喷射动压比下，不同喷嘴直径方案的流场特征以及燃料喷射掺混特性均存在相似性，缩小喷嘴直径能够提高燃料的掺混效率。就本文的研究状态，喷嘴直径为4mm的方案在燃烧室出口处的掺混效率比直径为10mm方案的高出约46.7%。此外，通道中的激波/掺混层相互干扰会大幅降低燃料穿透深度，但产生的剧烈剪切运动能够提高燃料掺混效率。

Abstract:

In order to optimize operating efficiency for a scramjet combustor，different injection cases in an elliptical scramjet combustor were numerically investigated by using Reynolds-Averaged Navier-Stokes (RANS)，and effects of wall curvature of different injection positions，injector diameters and reflected shock interaction on injection and mixing performance of transverse jet were analyzed. Results show that effects of wall curvature of injection positions on mixing performance are highly related to injector diameters. For the case with larger injector diameter，decreasing the wall curvature enhances mixing efficiency of the fuel，but damps out the total pressure recovery. However，for the smaller diameter case，variation of wall curvature rarely affects the mixing performance and total pressure recovery. At the same momentum ratio condition，similarities of different diameter cases are found regarding the flow characteristics，injection and mixing performance of different diameter cases. To reduce the injector diameter can effectively improve mixing efficiency of the fuel. For the cases studied in this paper，the mixing efficiency at the combustor outlet of 4mm injector diameter case is higher than that of 10mm case by 46.7%. Additionally，interaction between reflected shock and mixing layer in the combustor substantially reduces penetration height of the jet，but enhances mixing efficiency due to the intense shearing motion induced by the interaction.