Optimization of engine operating variables on performance and emissions characteristics of biogas fuelled CI engine by the design of experiments: Taguchi approach

Biogas obtained from renewable resources is a viable solution for solving energy scarcity and environmental degradation. A single-cylinder 4-stroke natural aspirated variable compression ratio research engine was fuelled with biogas as primary and diesel as a pilot injection in this work. Experiments were designed based on Taguchi L-9 OA (orthogonal array) choosing biogas flow rate, compression ratio, and engine load as input factors, while brake thermal efficiency (BTE), BSEC, CO, HC, NOx, and smoke were targeted responses. The effects level of factors on responses was analysed by using MINITAB software. The higher value of raw data and S/N ratios for BTE was observed with low biogas flow rate, higher compression ratio, and full engine load. On the other hand, lower raw data and high S/N ratio analysis for emissions characteristics (CO, HC, NOx, and smoke) were achieved in the order of rank, that is, engine load > biogas flow rate > compression ratio. With the analysis of results, optimum levels of various factors were evaluated. These results showed that the Taguchi method design was an effective tool for optimizing the elements in terms of combustion performance and emissions characteristics.