In order to realize the Paris Agreement, which aims to strengthen the global
response to climate change, conventional internal combustion engines (ICE) need
to contribute to reducing carbon emissions and improving thermal efficiency.
More importantly, in the face of energy shortages, it is urgent to search for
sustainable fuels. Poly-oxymethylene dimethyl ethers (PODE) and methanol are
both regard as important low-carbon, alternative fuels due to their high oxygen
content. Using PODE can overcome the characteristics of methanol as a
low-reactivity fuel with a low cetane number and poor ignition properties. In
this study, the combustion and emission characteristics of PODE/methanol blends
were investigated in a two-stroke direct injection engine. Firstly, the
performance of the engine under pure PODE (P100) and PODE/methanol blends (P50)
was compared. The results show that at BMEP of 0.31 MPa and injection timing of
-8°CA ATDE, P50 blends have lower CO2, CO, NOX and THC
emissions than P100 fuel. However, the start of combustion of P50 is delayed
slightly and ITE is lower than that of P100. Then, the effect of injection
timing on the performance of the P50 engine was investigated. With the delay of
fuel injection timing, NOX emissions decrease, but CO2,
CO, and THC emissions increase. Moreover, as the injection timing is delayed,
the engine COVIMEP was reduced and combustion stability was improved.
The engine indicated mean effective pressure (IMEP) reaches its maximum value of
0.441MPa at -8°CA ATDC and decreases as injection timing is delayed. However,
the indicated thermal efficiency (ITE) decreases with the delay of injection
timing, reaching a maximum of 41.8% at -8°CA ATDC. This study provides a
theoretical foundation for adopting PODE/methanol blends in diesel engines,
highlighting their potential to reduce conventional emissions while maintaining
operational feasibility. Further research on varying methanol ratios and load
conditions is recommended.