Vibration-based condition monitoring, performance and emission evaluation of a diesel engine fueled with Karanja biodiesel

This study aims to experimentally investigate the performance, combustion, emissions, and vibration characteristics of a single-cylinder, four-stroke, water-cooled variable compression ratio (VCR) diesel engine fueled with diesel and Karanja biodiesel blends (B20 and B30). Experiments were conducted under varying engine load, compression ratio (CR), and hot exhaust gas recirculation (EGR-HOT) conditions. Engine vibration was evaluated using root mean square acceleration (RMS Accel), and a novel integrated approach was adopted to correlate vibration behavior with performance and emission characteristics. The results show that vibration increases with engine load but decreases with higher compression ratios, while under EGR conditions it initially decreases and then rises at higher rates. The results show that vibration increases with engine load but decreases with higher compression ratios, while under EGR-HOT conditions it initially decreases and then rises at higher rates. Compared to diesel, RMS acceleration decreased by 4.3 and 8.49% under load variation, 3.01 and 7.18% under CR variation, and 2.66 and 6.75% under EGR-HOT conditions for B20 and B30, respectively. Emission analysis revealed reductions of 13.3% in hydrocarbon (HC), 6.58% in carbon monoxide (CO), and 17.98% in smoke opacity for B30, although nitric oxide (Nox) increased by 15.8% as compared to diesel. Combustion analysis indicated a 3.43% increase in maximum cylinder pressure (CPMax) and a 14.94% decrease in net heat release (NHR). In terms of performance, brake thermal efficiency (BTHE) decreased by 10.74%, while brake-specific fuel consumption (BSFC) increased by 18.52%. Overall, the study demonstrates that biodiesel blends improve emission and vibration characteristics but slightly compromise performance, while the integrated analysis provides deeper insight into combustion behavior and engine condition.