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

•Naphtha is an attractive and economical fuel for low-temperature combustion.•Naphtha can be utilized without modifications in internal combustion engines.•Engine performance, exhaust emissions and operating range were determined.•HCCI operating range can be extended with naphtha fuel blends.•Combustion was retarded via naphtha due to high octane number compare to n-heptane. 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 λ = 1.61–λ = 2.93 lambda values range at constant inlet air temperature of 60 °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/°CA and 11.9 bar/°CA with n-heptane and naphtha respectively at λ = 2 and 1000 rpm. ITE increased from 29% to 37% with naphtha according to n-heptane at λ = 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 λ = 2 and 1000 rpm, respectively. It was also seen that Naphtha showed wider HCCI operating range according to n-heptane especially knocking zone.