Thermal performance, emission and combustion characteristics of Manilkara Zapota seed oil biodiesel with hydrogen enrichment in CRDI diesel engine— An experimental approach

The present experimental investigation aims to improve the thermal performance and combustion characteristics and minimize the emission characteristics of a CRDI diesel engine fueled using an MZO20 biodiesel blend with varying flow rates of hydrogen fuel (0-12 LPM). A biodiesel blend containing 20% Manilkara Zapota oil (MZO20) is used as the pilot fuel, while hydrogen is introduced through the intake manifold. A detailed analysis on the thermal performance in terms of specific fuel consumption (SFC) and thermal efficiency (BTE) is made between the proposed fuel (MZO20 and MZO20 with hydrogen induction) along with diesel fuel for increased engine load. From the experimental findings, it may be concluded that the induction of hydrogen with increased flow rates leads to an improvement in thermal efficiency with reduced fuel consumption for higher loads of engine compared to diesel fuel. Similarly, for a wide range of engine loads, the emission characteristics of the proposed fuel, along with different flow rates of hydrogen induction, are compared with the base fuel. On analyzing the emission parameters, it is revealed that the CO emissions from the engine increase for diesel and MZO20 biodiesel blend, and with higher induction of hydrogen with MZO20 biodiesel blend, the CO emissions are reduced. Also, the experimental findings revealed that with a higher rate of hydrogen flow through the port of intake manifold with MZO20 biodiesel blend, the emission parameters such as unburnt hydrocarbon, CO 2 and smoke opacity, however, due to the higher combustion rates and escalated temperatures, the NOx formation increases. With the maximum flow rate of hydrogen flow through the port of the intake manifold with MZO20 biodiesel blend, the peak cylinder pressure enhanced by 6.34% compared to diesel fuel with the engine operated under peak load conditions. Moreover, the increase in cylinder pressure developed during the combustion process using 12 LPM of hydrogen flow rates leads to higher heat release rates by 15.95 and 10.41% compared to the MZO20 biodiesel blend and diesel fuel, respectively, at the maximum engine load condition.