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The influences of cold exhaust gas recirculation (EGR) and cetane number (CN) improver-di-tertiary butyl peroxide (DTBP) on the combustion characteristics and emissions of the Homogenous Charge Compression Ignition (HCCI) combustion engines fueled with PRF90 fuels (a mixture of 90% iso-octane and 10% n-heptane by volume) were studied in this paper. The experiments were performed using 0%, 1%, 2%, 3%, and 4% (by volume) DTBP-PRF90 blends. The experimental results show that the operating range was remarkably extended to lower temperature and lower engine load with the DTBP addition in PRFRON90 fuel. With the improvement of HCCI combustion at the lower temperature and light load by CN improver, the combustion phase of higher temperature and large load can be retarded to the top dead center (TDC) by appropriated EGR rate. As a result, the indicated thermal efficiency and indicated specific fuel consumption (ISFC) were improved.

This article investigates the inhibition effects of a 2-propanol additive on n-heptane homogeneous charge compression ignition (HCCI) combustion, analyzes the relationship between the emissions with the combustion parameters and fuel component, and evaluates the influence of cold exhaust gas recirculation (EGR) on HCCI combustion and emissions. The experiments were conducted on a single-cylinder HCCI engine using neat n-heptane and 10∼60% (by volume) 2-propanol/n-heptane blend fuels at 1800 rpm. The experimental results reveal that the ignition timing of the low-temperature reaction (LTR) is retarded, and the peak values of heat release during the LTR are decreased with an increase of 2-propanol in blend fuels. As a result, the ignition timing of the high-temperature reaction is delayed, both the maximum and lowest indicated mean efficient pressures (IMEP) are increased, and the combustion efficiency is also decreased. Parametric studies on CO and HC emissions show that the fuel volume with a high cetane ...