An experimental investigation of wide distillation fuel based on CTL on the combustion performance and emission characteristics from a CI engine

Abstract Coal to liquid (CTL) has promising application prospects as an alternative diesel fuel, but the direct application of coal-based synthetic diesel with high cetane number (CN) in compression ignition (CI) engines also has problems. Therefore, the CTL is blended with gasoline to adjust the physicochemical properties of the fuel, which is expected to meet the requirements of efficient and clean combustion. From the perspective of fuel design and combustion boundary condition control, the effects of CTL/gasoline blends on the combustion performance and emission characteristics in a CI engine are investigated in this study. Meanwhile, the variation in the start of injection (SOI) along with the addition of exhaust gas recirculation (EGR) permit achieving clean combustion with CTL/gasoline blends. Experimental results present that the wide distillation fuel (WDF) formed by adding gasoline to CTL, which is conducive to reducing the required mixing timescale and lengthening the chemical preparation timescale. CTL/gasoline blends bring in a higher premixed combustion ratio (PCR) and keep NOx and soot emissions at the lowest level after introducing EGR. Simultaneously, the inhibition effects of CTL/gasoline blends on particulate emissions are apparent with or without EGR due to prolonged ignition delay (ID) and improved mixing quality of fuel-air mixture, and the mass of the total particulates for CG60 is significantly reduced above 90% compared to pure CTL. In addition, the CTL/gasoline blends show refined engine characteristics for broad SOI, and the addition of gasoline to CTL is valid to alleviate the deterioration of combustion processes and emissions caused by EGR. In brief, Coupling EGR and gasoline addition is an effective way to break the trade-off relationship between NOx and particulate emissions for CTL.