The cold start performance of a spark-ignited dimethyl ether engine

Dimethyl ether (DME) seems to be a potential approach for improving the cold start performance for spark-ignited (SI) engines. In this paper, the cold start performance of an SI engine fueled with pure DME was experimentally investigated and compared with that of the original SI gasoline engine. The engine was successfully cold started with pure DME and pure gasoline, respectively. The test results demonstrated that, the fuel energy flow rate of the SI DME engine was only 30% of that of the original SI gasoline engine whereas the imep (indicated mean effective pressures) of the SI DME engine was effectively enhanced in the first 5 cycles. The SI DME engine had a shortened flame development period compared with the original SI gasoline engine. Meanwhile, the HC emissions were averagely decreased by 80% under the pure DME mode. The instantaneous CO and NOx emissions from the SI DME engine were slightly increased in the initial seconds after the onset of cold start and then markedly reduced compared with those from the original SI gasoline engine. In view of the above, starting an SI engine with pure DME could improve the combustion and emissions performance.