Researchers developing a new engine combustion system are experimenting with an 80% diesel/20% petrol blend to simultaneously reduce both nitrogen oxides and particulate matter in the engine exhaust gases. The project is a joint venture between Shanghai Jiao Tong University in China and the University of Michigan in the US.
The research is developing an engine using low temperature combustion. By keeping combustion temperatures low, the system avoids the usual trade off between nitrogen oxide and particular matter. In conventional engines higher combustion temperatures equate to lower particulate matter but higher nitrogen oxides, lower temperatures normally increase particulates and lower NOx.
The fuel is premixed before injection into the combustion chamber in an engine with a decreased compression ratio. The EGR rate is around 40% but is lowered when the engine is working hard. The study has found it is possible to run an engine with low combustion temperatures producing much lower levels of exhaust gas emissions than had previously been expected, without resorting to after treatment.
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