【作者】 赵延辉；

【导师】 梁剑寒；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2011， 硕士

【摘要】 本文以基于凹腔-支板火焰稳定器的超声速燃烧室为研究对象,采用NPLS技术获得了高空间分辨率的流场结构图,运用PIV原理计算得到了超声速速度场和涡量分布,同时用混合RANS/LES方法进行了数值模拟,通过实验与数值模拟分析了超声速来流条件下支板绕流和燃烧室流动特性。对支板绕流进行研究发现:水平支板和竖直支板前缘均产生弓形激波,侧壁边界层很薄,流体流经支板两表面后在后缘转向,剪切层脱落在尾部壁面附近形成回流区,绕过回流区的两股流体汇合后被迫转向形成斜激波,汇合后的流体向下游发展形成卡门涡街,竖直支板顶部在前缘转角处产生了两股流向涡,水平支板在悬空的短边一侧也发现较弱的流向涡。对正常流态下的超声速燃烧室冷态流场进行研究发现:单凹腔燃烧室中凹腔与侧壁面相互作用可以有效实现主流与凹腔内部流动的质量和动量交换,增强混合作用;水平支板前缘激波促使凹腔剪切层涡结构进一步破碎,波后压强升高促使流体进入凹腔,凹腔后壁面处产生的回流区对混合增强和火焰稳定有重要作用;流体绕过竖直支板后因流道扩张产生膨胀波,剪切层脱落形成大回流区,有利于混合增强和火焰稳定,流体流经转向产生的激波后压强升高,流速降低,形成的凹腔剪切层偏向凹腔底壁,在凹腔前缘产生了膨胀波,诱使两侧高速流体转向进入凹腔,促进了主流与凹腔的质量和动量交换。对高背压条件下的超声速燃烧室冷态流场进行研究发现:单凹腔燃烧室凹腔剪切层在凹腔后壁面大回流区输运作用下很容易产生大尺度涡结构,这有利于混合增强和火焰传播,但大涡破坏了凹腔前缘斜激波,并挤压周围流体产生杂乱的波系;水平支板可以有效抑制大涡结构对主流的干扰,增强混合,但大涡结构在支板前缘激波和凹腔后壁面回流区双重作用下前移到凹腔前缘处,易影响到来流边界层,使其厚度增加,对主流产生干扰;竖直支板后方大回流区在高背压作用下被大涡结构充满,对混合增强和火焰稳定有重要作用,但容易产生壅塞。更多还原

【Abstract】 was focused on in this paper. The flow field was observed by means of NPLS technology, with which the complex supersonic flow structures could be imaged at high spatiotemporal resolution, and the velocity field as well as the vortices distribution could be calculated by supersonic PIV system. The hybrid RANS/LES strategy was employed in numerical simulation of the scramjet combustor. The characters of the flow field about the strut and the combustor could be analyzed by means of experimental and simulant methods.The flow field around the strut was drawn a conclusion as follows. Arched shock was formed in front of both the horizontal strut and the vertical strut. The boundary layer on the side surfaces of the strut was thin. The recirculation zone was formed by the fallen boundary layers of the side surfaces at the rear of the strut where the flow coming from both sides turned around and struck against each other, as a result, the flow was forced to turn around again and Carmen vortex was developed downstream. A pair of vortex flow was generated from the head of the vertical strut, which was smaller on the short side of the horizontal strut.The characters of non-reaction flow field in scramjet combustor were resulted from the study as follows. Exchange of mass and momentum was promoted by the intersection of cavity and sidewall in the scramjet combustor. Vortex was broken up due to the intersection of the arched shock wave and the shear layer belonging to horizontal strut and cavity respectively. The flow was driven into the cavity under the power of high pressure behind the shock wave. The recirculation zone at the back wall of the cavity was beneficial to mixing enhancement and flame holding. As for the vertical strut, the recirculation zone at the rear was bigger and good for mixing and flame holding. The flow was slowed while the pressure was higher after passing through the oblique shock waves behind the vertical strut, so the shear layer over the cavity leaned to the bottom resulting in expansion waves at the front of the cavity and induced the high speed flow beside to enter into the cavity, which was good for flame holding obviously.The situation of the scramjet combustor was studied under the condition of high back pressure in this paper, and the conclusion was arrived as follows. Large vortex was often generated due to the recirculation zone at the rear of cavity, which was beneficial for mixing enhancement and flame spread, but the large vortex could also generate complex shock waves by extruding the supersonic flow, which broke the oblique shock wave at the front of the cavity and disturb the core flow. The vortex disturbing the core flow could be restrained by horizontal strut effectively while the enhancement of mixing was kept, but the large vortex was induced to the front of the cavity by both the shock wave at the front of the strut and the recirculation zone at the rear of the cavity, therefore, the boundary layer of the coming flow become thicker probably and the core flow might be influenced. The recirculation zone was filled with large vortex on condition of high back pressure, which could perform well in mixing enhancement and flame holding but also might choke in the working process of scramjet combustor.更多还原