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.