Experimental Study On Combustion And Emission Characteristics Of RCCI Mode Fueled With N-heptane/alcohol-like Fuels

Global energy problems, environmental pollution and increasingly strict emission regulations urge people to seek high efficiency, low emission combustion mode. Reactivity Controlled Compression Ignition(RCCI) mode adopts port injection of high octane number fuels and in-cylinder directly injected high cetane number fuels. In recent years, RCCI is proved to be a combustion mode which can achieve high efficiency and low emission.Firstly, an experimental study of RCCI mode on combustion and emissions characters was conducted fueled with n-heptane/gasoline and n-heptane/ethanol. Results show that the latent heat of vaporization and cetane number of port injection fuel play important roles in RCCI combustion. When the premixed ratio is constant, the higher latent heat and lower cetane number of ethanol lead to combustion delay. Port injection of ethanol will benefit the smoke emissions and NOx emissions. In the small load, larger premixed ratio will lead to incomplete combustion and will cause higher HC emissions and CO emissions. In the small load, when fueled with n-heptane/gasoline, the indicated thermal efficiency is higher than with n-heptane/ethanol. However, at high load, the conclusion is opposite.Secondly, combustion and emission properties of RCCI mode were analyzed with port injection of ethanol, butanol and n-amyl alcohol, respectively. Studies show that when fueled with n-heptane/n-butanol, n-heptane/n-amyl alcohol and overall heating values per cycle are constant, the differences between combustion characteristics increase. And when adopts high premixed ratio, NOx emissions and smoke emissions decrease simultaneously. Meanwhile, compared to ethanol RCCI, the combustion phases of n-butanol and n-amyl alcohol would not be greatly delayed. When premixed ratio is constant, with the increase of overall heating values per cycle, the differences of port injection of butanol, n-amyl alcohol would become smaller. And when in high overall heating values per cycle, the NOx and soot emissions of ethanol, butanol and n-amyl alcohol RCCI would be at high levels.