缸内湍流运动对复合燃烧燃料活性分布的作用机制

缸内受限条件下燃料与湍流的相互作用是燃料分层控制复合燃烧的关键问题。针对该问题，通过向缸内直喷高活性燃料二甲醚（Dimethyl ether，DME），形成高活性燃料浓度分层。基于光学可视化发动机实验平台，利用粒子图像测速（Particle Image Velocimetry，PIV）、Rayleigh散射、Mie散射以及高速摄影结合放热分析等手段对复合燃烧这一缸内受限空间下的流动及燃烧过程进行了观测，并通过三维计算流体力学（Computational Fluid Dynamics，CFD）仿真手段对观测到的现象进行解释。结果表明:缸内存在大范围逆时针涡流场，DME的蒸发和扩散过程受到流场的作用；在流场的作用下，缸内燃烧过程呈现DME集聚区域自燃-火焰传播-多点自燃放热特征。

Mechanism of in-cylinder turbulence on the distribution of fuel activity in hybrid combustion

The interaction between fuel and turbulence under the in-cylinder limited conditions is the key issue for hybrid combustion controlled by fuel activity stratification. Dimethyl ether (DME) is injected to the cylinder to produce high activity fuel stratification. Particle image velocimetry, laser Rayleigh scattering, Mie scattering and high speed imaging combined with heat release analysis on the optical engine experiment platform are used to observe the flow field and combustion process of hybrid combustion in the limited space of cylinder. 3D Computational Fluid Dynamics (CFD) simulation are used to explain the experimental phenomena. Result shows that there is a large range of counter-clockwise vortex field in the cylinder, and the diffusion and evaporation process of DME is influenced by the flow. Under the flow field, the combustion process in the cylinder shows characteristics of DME auto-ignition in the distribution area, flame propagation, multi-point auto-ignition.