Research Initiation Award: Combustion in an Asymmetric Configuration

本项目的目的是了解燃烧和剪切层控制技术之间的相互作用。建议对小展弦比矩形通道突扩燃烧的流体力学进行研究。这种配置利用了多种控制技术的组合。主动强迫将被用来驱动系统的声学共振，并组织切变层涡旋结构以进行锁相分析。被动强迫将通过位形几何引入；在剪切层中形成的椭圆涡环经历自感应，使喷流截面变形，并引入平面和轴对称位形所没有的横向速度。该方法是一种实验方法，使用激光多普勒测速和流动显示来研究矩形突然膨胀中的速度场和预混火焰。当量比将从后向台阶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而变化，从LINE到RICH，其中火焰/流动相互作用以声学共振为主。这将允许确定这些控制方法在此配置中的有效程度。这项研究最初将仅限于预混燃烧。这些结果以后可以扩展到解决非预混燃烧中的问题，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产生提高燃烧效率和控制的结果。

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.