Experimental analysis of effective combustion heat release rate for improving the performance of synthetic biogas-diesel dual-fuel engine

To analyze the effect of combustion mode on performance and emission characteristics of dual-fuel engines, an experimental study of heat release rate is conducted for biogas as main fuel. Parametric investigations are needed to establish the effect of heat release rate on performance of dual-fuel engines. A new parameter, Combustion Time Coefficient (CTC), is defined to quantify the combustion timing and heat release patterns to study its effect on the performance parameters. It is used along with a heat release rate (HRR) related coefficient, called as HRR-Balanced Coefficient (HBC). These combustion indicators are used for experimental analysis of reactivity-controlled compression ignition (RCCI) strategies for biogas diesel dual-fuel engine. Experiments were performed on a variable compression ratio, single-cylinder compression ignition (CI) engine run on dual-fuel mode. Synthetic biogas energy shares of 0%, 20%, 40%, 60%, and 80% are provided for RCCI at various compression ratios of 18, 17, 16 ,and 15. The results show that an increase in CTC and a reduction in HBC have a positive effect on BTE, HC, and CO emission, while emissions of NOx increase. The ranges of CTC and HBC are found for low- and high-load conditions to reduce emissions and enhance the performance of the engine. A set of working and design parameters like compression ratio (CR), percentage energy share (PES) of biogas and load are identified to maintain the CTC and HBC within these ranges. For low-load operations, PES of 60% with 18 CR and for full load operations PES of 40% with 17 CR give the favorable performance. For the full range of the loads, CTC and HBC are good parameters to identify the operating range of PES and CR for dual-fuel engines.