Evaluation of Combustion and Emission Characteristics of CI Engines Operating Dual-Fuel with BioCNG/Diesel and BioCNG/HVO

This paper presents experimental research results on dual-fuel engines using diesel, HVO, bioCNG/diesel, and bioCNG/HVO fuels. The dual-fuel engine was converted from Cummins' diesel engine 4.5L. The purpose is to analyze each fuel type's combustion process and emission characteristics. The experiments were carried out at a fixed speed of 1900 rpm, and the load increased gradually from low to maximum load, with a jump of 100 Nm. The experimental results show that the dual-fuel engine (bioCNG/diesel or bioCNG/HVO) was retarded premixed combustion of diesel, leading to a prolonged ignition delay compared to the operation with liquid fuel (diesel or HVO). As a result, there is more time for a more homogenized dual-fuel mixture, accelerated diffusion combustion, and shorter combustion times at this stage. The disadvantage of dual-fuel engines is that there is detonation in some cycles. In this study, the Knock peak method was used to determine the detonation limit, and the cycles with detonation in a set of 200 cycles were measured. In addition, BTE increases when part of the energy of liquid fuel is replaced by bioCNG fuel. At low loads, the largest percentage ratio of bioCNG can replace 74% in dual-fuel engines using bioCNG/diesel and 66% in dual-fuel engines using bioCNG/HVO. Dual-fuel engines have significantly reduced CO2 and PM emissions concentrations compared to engines using liquid fuel. Especially when operating with bioCNG/HVO dual-fuel, the concentration emission is reduced by 20% CO2 and 50% PM compared to diesel; and vice versa, the concentration of CO, HC, and NOx emissions increased many times.