Lower value of CA90-CA50 indicates fast combustion rate in the late combustion phase and vice versa. The comparison of the combustion rate in the late combustion phase between diesel, PODE15 and PODE25 is shown in fig6. it shows that blending PODE have the tendency to accelerate the combustion rate in the late combustion phase, which can compensate the longer injection duration caused by the lower LHV of PODE. With the increase of EGR, the ambient oxygen concentration decreases, leading to the reduction of combustion rate for all fuels. Moreover, the superior volatility and high oxygen content in PODE can also be beneficial to promote the combustion rate. Therefore, with the increase of blending ratio, the CA90-CA50 decrease, which means faster combustion rate in the late combustion phase.