【作者】 任春雷；

【导师】 刘卫东；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2009， 硕士

【摘要】 本文以超燃冲压发动机支板喷射燃料的混合机理为研究对象,利用基于纳米粒子的平面激光成像(NPLI)技术和高速纹影等实验手段与数值模拟相结合,重点对各种构型支板的通流流场特性和燃料的混合特性进行了研究。采用纹影实验与RANS数值模拟方法相结合,对各种构型支板的通流流场特性进行研究。结果表明:采用RANS模拟结果与实验结果吻合较好,本文所用的RANS模拟可以准确的模拟超声速支板流场;基准支板尾部形成的超声速可压混合层发展缓慢,影响了燃料与空气的混合。采用交错尾部支板可以在支板尾部产生流向涡,增强对剪切层的扰动,加快剪切层的发展,同时这种褶皱型的混合层结构增大了质量和动量交换的表面积。凹腔支板在其凹腔内和尾部均可提供大面积的驻涡区,有利于火焰的稳定,但尾部剪切层发展比基准支板更加缓慢。利用NPLI技术与RANS数值模拟方法相结合,对支板燃料的混合特性进行了研究,结果表明:基准支板尾部通流剪切层限制了燃料向展向扩散,混合效果较差。引入流向涡可以有效提高燃料与空气的混合能力,燃料喷入流场后迅速充满流向涡,流向涡的发展引导了燃料在流场中的分布和扩散。因而流向涡的发展速度决定了燃料的混合性能。综合膨胀角的大小决定了流向涡的生成和发展,最佳综合膨胀角不是固定值,而是受到喷注方式、喷注压降、还有燃烧的综合影响。采用带凹腔结构的支板时,受到剪切层的制约,燃料主要集中在支板尾迹区内,无法得到良好的展向分布。更多还原

【Abstract】 The fuel/air mixing mechanism of scramjet with strut was studied in the presented dissertation. Nanoparticle-based Planar Laser Imaging (NPLI), high speed photography and schlieren, as well as numerical simulations, are applied to in-depth investigations on characteristics of non-injection flow and fuel/air mixing with different strut configurations in supersonic flow.The characteristics of non-injection flow field with different strut configurations were investigated by schlieren and numerical simulation. The numerical results accord with the experimental results very well which indicates that the supersonic flow field with strut can be properly forecasted by the presented simulation method with RANS(Reynolds Averaged Navier–Stokes). Since the compressible shear layer with basic strut configuration in supersonic flow develops slowly, further fuel/air mixing was impacted. The streamwise vortexs produced by Alternating-Wedge struts can promote the development of shear layer and increase the mass and momentum exchanging interface. A wide range of Recirculation zone which appears both in the curve and at the tail of curve-strut is conducive to the stability of the flame. But the development of shear layer induced by curve-strut was slower than that of basic-strut.The fuel/air mixing characteristics were investigated by NPLI and RANS simulation. The results show that the fuel/air mixing performance was poor for basic strut configuration on account of that the spanwise diffusion of the fuel was limited by the shear layer. The streamwise vortexs were filled with fuel as soon as the fuel was injected, and the development of streamwise vortexs conducted the distribution and diffusion of the fuel. Thus the fuel/air mixing performance was determined by the growth rate of streamwise vortexs. The generation and growth of streamwise vortexs was limited by the Total Expansion Angle(TEA). The optimal TEA was affected by the injection mode, the pressure differential of injection, as well as combustion. For curve-strut, fuel mainly concentrated in the wake of strut which limited its spanwise distribution.更多还原