Effect of boost pressure on combustion, performance and emission characteristics of a multicylinder CRDI engine fueled with argemone biodiesel/diesel blends

Abstract

The problem of higher NOx emissions with the utilization of biodiesel is a grim prospect indeed. Engine boost pressure has a significant impact on the performance, emission, and combustion characteristics of the engine, therefore, its effect has been studied on 1.9 L multi-cylinder CRDI fueled with AB20 blend. The experiments were performed in two stages with two different modes, Mode-I (part load) and Mode-II (high load). In Stage-I testing, the ECU maps designed and calibrated for diesel fuel were used for testing argemone biodiesel/diesel blends (AB10, AB20, AB30, and AB50) in the engine and an optimized blend (AB20) among these tested fuels was selected for testing in Stage-II. Stage-II testing involves variation of boost pressure from 110 to 140 kPa at Mode- I, and 150 to 180 kPa at Mode-II. It was observed that at part load the default map boost pressure (120 kPa) seems beneficial for AB20 blend with improved performance and emission characteristics of the engine. However, at higher load lower boost pressure improves both the NOx emissions (6%↓) and brake thermal efficiency (4.04%↑) in comparison to diesel fuel. For AB20 blend, lowering the boost increases the ignition delay. Consequently, cylinder pressure peak and heat release rate peak shifts away from TDC. On the other hand, increasing the boost lowers the ignition delay and premixed heat release phase, thereby promoting the diffusion phase of combustion.