Operating range, combustion, performance and emissions of an HCCI engine fueled with naphtha

In this study, it was aimed that the effects of naphtha on homogeneous charged compression ignition (HCCI) combustion, performance, exhaust emissions and operating range were researched experimentally in an HCCI engine. The test engine was able to operate with HCCI mode between 800 and 2000 rpm and lambda = 1.61-lambda = 2.93 lambda values range at constant inlet air temperature of 60 degrees C. Pure n-heptane and naphtha, N25, N50 and N75 fuel blends were used as test fuels. Experiments showed that knocking tendency reduced with the increase of lambda. Similarly, more stable combustion was obtained with the addition of naphtha into n-heptane due to higher octane number. Test results showed that HCCI combustion was delayed when naphtha fraction increased in the test fuels. MPRR was obtained as 15.6 bar/degrees CA and 11.9 bar/degrees CA with n-heptane and naphtha respectively at X = 2 and 1000 rpm. ITE increased from 29% to 37% with naphtha according to n-heptane at lambda = 2 and 1000 rpm. On the contrary, HC and CO increased from 331 ppm to 411 ppm and 0.051% to 0.075% with naphtha compared to n-heptane at lambda = 2 and 1000 rpm, respectively. It was also seen that Naphtha showed wider HCCI operating range according to n-heptane especially knocking zone.

Automated summary

This study experimentally investigated the effects of naphtha on HCCI combustion in an engine, finding that knocking tendency decreased as lambda value increased and more stable combustion was achieved with the addition of naphtha. The addition of naphtha led to delayed HCCI combustion and wider operating range compared to n-heptane.