Abstract
Ethanol–diesel dual-fuel premixed charge compression ignition combustion was investigated in a diesel engine with a compression ratio of 18.2:1, where the ethanol was delivered via port fuel injection and the diesel was injected through common-rail high-pressure direct injection. The paper presents the test results highlighting the effect of the fuel ratio, the exhaust gas recirculation and the diesel start of injection on the dual-fuel combustion and the emissions from medium to high loads. The results showed that the usage of ethanol can effectively suppress the nitrogen oxide emissions and the soot emissions with less aggressive exhaust gas recirculation levels than with diesel-only low-temperature combustion. The combustion phasing was responsive to the in-cylinder diesel injection over a wide range of timings. The dual-fuel operation load was increased to an indicated mean effective pressure of 18 bar (nearly the full load of the test engine), with a boost intake pressure of up to 2.5 bar and the ethanol ratio increased to about 0.9. The high-load premixed charge compression ignition was realized through adequate control of the exhaust gas recirculation level, the intake boost pressure, the injection pressure, the injection scheduling and the fuel ratio. The challenges and the approaches to suppress the nitrogen oxide emissions and the soot emissions simultaneously at a high load were demonstrated. The nitrogen oxide level was constrained to within 0.2 g/kW h and the soot level was simultaneously below 0.01g/kW h at a stable operation load with an indicated mean effective pressure of 16 bar and a moderate pressure rise rate.
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