Therefore, as the blending ratio increase, the peak HRR is lowered because of lower LHV and shorter mixing time. As the load increase, the temperature in the cylinder increase while the ignition delays of these fuels are mostly affected by the high temperature. Thus, the ignition delays of these fuels are almost the same at medium and high loads. As the temperatures are getting higher, the combustion process shifts from a predominantly kinetic control to a predominantly thermodynamic control, the effects of fuel properties on combustion are getting smaller. Therefore, the difference in HRR is getting smaller among these fuels as the load increases. During the diffusion combustion period at each load, the HRR of PODE15 and PODE25 are slightly higher than diesel. This illustrates that blending PODE can promote the air-fuel mixing rate and accelerate the combustion rate of diesel/PODE blends. This conclusion was also found by Pellegrini et al. |26| in a single cylinder optical engine. Nevertheless, at different operation conditions, the in-cylinder pressure characteristics have no significant difference among diesel,PODE15 and PODE25.