• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.54-62
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• 2007

The knock characteristics in an engine were investigated under homogeneous charge compression ignition (HCCI) operation. Liquefied petroleum gas (LPG)and gasoline were used as fuels and injected at the intake port using port fuel injection equipment. Di-methyl ether (DME) was used as an ignition promoter and was injected directly into the cylinder near compression top dead center (TDC). A commercial variable valve timing device was used to control the volumetric efficiency and the amount of internal residual gas. Different intake valve timingsand fuel injection amounts were tested to verify the knock characteristics of the HCCI engine. The ringing intensity (RI) was used to define the intensity of knock according to the operating conditions. The RI of the LPG HCCI engine was lower than that of the gasoline HCCI engine at every experimental condition. The indicated mean effective pressure (IMEP) dropped when the RI was over 0.5 MW/m2and the maximum combustion pressure was over 6.5MPa. There was no significant relationship between RI and fuel type. The RI can be predicted by the crank angle degree (CAD) at 50 CA. Carbon monoxide (CO) and hydrocarbon (HC) emissions were minimized at high RI conditions. The shortest burn duration under low RI was effective in achieving low HC and CO emissions.

• Journal of ILASS-Korea
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• v.19 no.4
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• pp.204-210
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• 2014

Experimental study was conducted to investigate the effect of EGR(exhaust gas recirculation) on engine noise using single cylinder combustion ignition engine. Under constant engine rotary speed of 1200 RPM, 8 mg fuel quantity was injected with 15, 18 and 21% of oxygen ratio and 1400 bar of injection pressure. Using the in-cylinder pressure data acquired by a piezoelectric transducer, the engine performance parameters were calculated. Radiated engine noise measured for 10 seconds was analyzed using spectral characteristics and sound quality metrics such as loudness, sharpness, roughness. From the obtained engine performance parameters and sound quality metrics, effect of oxygen ratio of the premixed air, start of injection timing on frequency characteristic and sound quality metrics were analyzed. Correlation analysis was conducted between MPRR(maximum pressure rise rate), RI(ringing intensity) and sound quality metrics. RI was identified as the most important factor having influence on the sound quality metrics.