Comparative Assessment of Engine Vibration, Combustion, Performance, and Emission Characteristics Between Single and Twin-Cylinder Diesel Engines in Unifuel and Dual-Fuel Mode

The persistent efforts among the researchers are being done to reduce emissions by the exploration of different alternative fuels. The application of alternative fuel is also found to influence engine vibration. The present study explores the potential connection between the change of the engine operating parameters and the engine vibration pattern. The objective is to analyze the effect of alternative fuel on engine vibration and performance. The experiments are performed on two different engines of single cylinder (SC) and twin-cylinder (TC) variants at the load range of 0-34 Nm, with steps of 6.8 Nm and at the constant speed of 1500 rpm. The single cylinder engine, fueled with only diesel mode, is tested at two compression ratios (CRs) of 16.5 and 17.5. However, the twin-cylinder engine with a constant compression ratio of 16.5 is tested at both diesel unifuel and diesel-compressed natural gas (CNG) dual-fuel modes. Further, in dual-fuel mode, tests are conducted with compressed natural gas substitutions of 40%, 60%, and 80% for given loads and speed. The engine vibration signatures are measured in terms of root mean square (RMS) acceleration, representing the amplitude of vibration. The combustion parameters considered are cylinder pressure, rate of pressure rise, heat release rate (HRR), and ignition delay. At higher loads, the vibration amplitude increases along with the cylinder pressure. The maximum peak cylinder pressure (PCP) of 95 bar is found in the case of the single cylinder engine at the highest load condition that also produced a peak vibration of 3219 m/s(2).