An investigation of optimum control of injection timing/injection pressure for a multicylinder common rail direct injection engine fueled with AB20 blend

A multicylinder turbocharged common rail direct injection engine was tested at part load (62.4 Nm) and high load (156 Nm) to determine the optimum combination of injection pressure (IP) and injection timing (IT) for AB20 blended fuel. IP and IT were varied from default settings, that is, 9.2 degrees before top dead center (BTDC), 45 MPa at part load; 9.8 degrees BTDC, 95 MPa at high load, as specified in the calibration map of the engine. As a result of the experimental results, brake thermal efficiency (BTE) increased up to 5.36% when IP increased from 35 MPa to 45 MPa and 0.72% when IP increased from 45 MPa to 55 MPa under the part load condition. At high load, the maximum BTE of 38.22% was attained at 105 MPa IP and 9.8 degrees BTDC IT. At this condition, nitrogen oxide (NOx) emission was noted as 1353 ppm, which is 12.28% higher than the NOx noted for diesel fuel at the default IP and IT conditions. When IP increases from 35 to 55 MPa at part load and 85-105 MPa at high load, cylinder pressure, heat release rate, and rate of pressure rise increase at all tested ITs. At high load, the condition of retarded IT (8.8 degrees BTDC) and default IP (95 MPa) shows (a) 2.35% higher BTE and (b) almost similar NOx and improved HC, CO, and smoke emissions for the AB20 blend. Moreover, at the same experimental conditions, premixed heat release for the AB20 blend was noted to be 70.16 J/Deg./C.A, with heat release rate peak at 6 degrees ATDC.