Experimental studies on the key parameters controlling the combustion and emission in premixed charge compression ignition concept based on diesel surrogates

Abstract

Compared with the traditional diesel combustion mode, the premixed charge compression ignition mode only changes the fuel injection strategy combined with a certain ratio of exhaust gas recirculation, which needs little change to the overall engine. Studies on the effects of the cetane number and volatility of the diesel fuels are critical to the combustion, emissions and load range expansion of the premixed charge compression ignition mode. Based on the multi-component surrogate fuels, this paper controlled the cetane number and the volatility of diesel surrogates by changing the components and their proportions combined with the adjustment of fuel injection parameters to study the factors that affect the combustion and emissions of the premixed charge compression ignition mode. The cetane number of fuels played a decisive role in the combustion phase under the same injection strategy. The decrease of cetane number of the direct injected fuels led to the increase of CO and HC emissions. Low cetane fuels helped to inhibit premature combustion of pilot injected fuel. The decrease in fuel cetane number could suppress the emissions of accumulated particles. Changing the volatility of the fuel had limited effects on the combustion phase and combustion speed. High volatility fuel could effectively reduce the CO and HC emissions in the premixed charge compression ignition mode although it cannot fundamentally solve the high CO and HC emission problems caused by the premixed strategy. Increasing the volatility of the fuel could reduce the concentration of accumulated particles. Under the premise of ensuring that the NOx emissions were lower than 200 ppm via adjusting the injection parameters, increasing fuel volatility may decrease the indicated fuel consumption as low as 178 g/kWh.