超声速内流道摩擦阻力分析及减阻技术研究

针对带有后向台阶的等截面受限空间,通过三维数值模拟开展了超声速内流道摩擦阻力分析及减阻技术研究。分析对比了飞行马赫数为5、6、6.5及7对应的燃烧室入口条件下相同质量氢气喷注、燃烧对壁面摩擦阻力的影响机制以及不同喷注压力对喷孔下游壁面剪应力的影响。研究结果表明,同等质量的氢气,低速喷注优于高速喷注(507、50.7 kPa喷注压力分别得到10%、5%左右的减阻效果)。近壁区燃烧得到接近70%的减阻效果;气流经过突扩结构之后,壁面剪应力呈现规律地不均匀变化,最大差异达100%;剪应力与密度变化趋势基本吻合。因此,发动机内流道减阻的关键在于营造近壁区低密度场;稳定、有效的减阻区域发生在靠后方的位置,但由于流动掺混、燃料的燃烧消耗,减阻效果沿流向逐渐减弱。 

Research on skin-friction drag and drag reduction technics in a supersonic inner flow path

In a constant-cross-confined-space with rearward facing steps, the skin-friction drag and drag reduction technics in a supersonic inner flow path was developed by three-dimensional numerical simulation. The influential mechanism of skin-friction drag in the same mass hydrogen injection and combustion but under different air inlet conditions and combustor entry conditions when the scramjet engine operated from flight Mach number 5, 6, 6.5 and 7, and different injecting pressure effects on the wall shear stress beheading the injectors were analyzed and compared. The results show that the drag reduction effect under low injection speed is more obvious than that under high injection speed. 507 kPa obtains 10% drag reduction and 50.7 kPa obtains 5%. Boundary layer combustion achieves almost 70% drag reduction. When the fluid passes backward facing step, regularly uneven changes of wall shear stress will appear and the biggest difference is 100%. The trends of wall shear stress and density are basically the same. Therefore, the key point of skin-friction drag reduction in inner flow path is building low density field near the wall surface. The area with stable and effective drag reduction effect is located more backwards of the injectors. However, due to the mixing and consumption of fuel, the drag reduction effect gradually decreases along the flow direction.