An experimental study on the spray structure of oxygenated fuel using laser-based visualization and particle image velocimetry

The oxygenated fuels such as dimethoxy methane (DMM), dimethyl carbonate (DMC), dimethyl ether (DME) are regarded as hopeful alternative fuels as well as fuel additive to resolve the trade-off relation between NOx and smoke in normal diesel engine. The better understanding for the effect of oxygenated fuel on the atomization is helpful for the combustion optimization. This paper presents an experimental study on the spray structure of oxygenated fuel by laser-based 2D visualization and particle image velocimetry (PIV). The fuels are injected from a single-hole nozzle at an injection pressure of 40 MPa into a room condition. A signal synchronization system is developed to obtain the spray at an arbitrary injection delay time. The spray structures of diesel fuel and oxygenated fuel are visualized by 2D Mie scattering imaging. A direct cross-correlation DPIV technique is applied to analyze the instantaneous droplet velocity vector field. It is found that the spray of oxygenated fuel shows an umbrella-shape structure, a lager spray angle, and a shorter spray tip penetration than diesel fuel. The spray of oxygenated fuel presents a weak large-scale heterogeneity and branch-like structure, a finer droplet, a stronger interface between fuel spray and surrounding gas, and a more violent vortical motion. The viscosity of property of oxygenated fuel plays a significant effect on the improvement of atomization behavior.