Research Initiation Award: Combustion in an Asymmetric Configuration

这个项目的目的是了解燃烧和剪切层控制技术的相互作用。研究小宽高比矩形通道突然膨胀燃烧的流体力学问题。这种配置结合了几种控制技术。主动强迫将用于驱动系统的声学共振，并组织切变层的涡旋结构进行锁相分析。被动强迫将通过构型几何引入；剪切层中形成的椭圆涡旋环发生自感应，使射流截面变形，引入了平面和轴对称构型中没有的横向速度。该方法采用实验方法，利用激光多普勒风速法和流动可视化技术对矩形突然膨胀过程中的速度场和预混火焰进行了研究。等效比的范围从低到高，即后面向阶跃下游剪切层中火焰的稳定受被动、主动和三维控制技术的影响，到高，即火焰/流相互作用由声学共振主导。这样就可以确定这些控制方法在这种配置中有效的程度。这项研究最初将局限于预混燃烧。这些结果可以扩展到解决非预混燃烧的问题，例如优化燃油喷射位置，以利用控制技术产生的流场。这项研究预计将对燃烧应用产生重大影响，从工业脉冲燃烧器和有毒废物焚烧炉到冲压发动机的亚音速和超音速燃烧。了解剪切层控制技术对混合和燃烧的影响，可以立即提高燃烧效率和控制。

The objective of this project is to understand the interaction of combustion and shear layer control techniques. The proposal is to study the fluid mechanics of combustion of a small aspect ratio rectangular channel sudden expansion. This configuration utilizes a combination of several control techniques. Active forcing will be used to drive the system's acoustic resonances and to organize the shear layer vortical structures for phase locked analysis. Passive forcing will be introduced via the configuration geometry; the elliptic vortex rings formed in the shear layer undergo self-induction, deforming the jet cross section and introducing transverse velocities not found in plane and axi-symmetric configurations. The approach is experimental, using laser doppler anemometry and flow visualization to examine the velocity field and premixed flame in a rectangular sudden expansion. The equivalence ratio will range from lean, where the stabilization of the flame in the shear layer downstream of the backward facing step is affected by the passive, active and three dimensional control techniques, to rich, where the flame/flow interaction is dominated by acoustic resonances. This will allow determination of the extent to which these control methods are effective in this configuration. The study will be initially limited to premixed combustion. The results can later be extended to address issues in nonpremixed combustion such as the optimization of fuel injection locations to take advantage of the flowfields produced by the control techniques. This research is expected to have a significant impact on combustion applications ranging from industrial pulse combustors and toxic waste incinerators to subsonic and supersonic combustion in ramjets. The understanding of the effects of shear layer control techniques on mixing and combustion can produce immediate results in increased combustion efficiency and control.