Abstract: In order to investigate the combustion characteristics of dimethyl ether (DME)， the experiments are conducted under the initial temperature of 293 K, the driving gas pressure of 0.6 MPa, the initial pressure of 0.04~0.08 MPa, the nitrogen dilution ratio of 47.29~60.81% and the compression ratio of 8.82~12.02. The effects of the initial pressures， nitrogen dilution ratio and compression ratio on the ignition delay time and peak combustion pressure of the DME-O₂-N₂ mixtures are investigated using a rapid compression machine (RCM). The two-stage heat release and two-stage ignition delay time are observed. The negative temperature coefficient (NTC) behavior of the mixtures is observed with the increase in compression ratio. The temperature in the presence of NTC increases with the increase in initial pressure. The temperature in the presence of NTC decreases with the increase in nitrogen dilution ratio. Under a certain initial pressure， with the increase in nitrogen dilution ratio， the peak combustion pressure and the second ignition delay time show the opposite trend under different compression ratios. Under a certain nitrogen dilution ratio，with the increase in compression ratio，the peak combustion pressure and overall ignition delay time show the opposite trend under different initial pressures.

Key words: engineering thermophysics, rapid compression machine, ignition delay time, negative temperature coefficient