Analysis of Thermal Balance of Diesel Engine and Identification of Scope for Waste Heat Recovery

Diesel engines as prime movers for passenger cars are becoming popular, primarily due to their superior thermal efficiency. However, the peak thermal efficiency does not exceed 35 to 40% even in the best engines. Huge efforts are being put in to improve engine efficiencies to meet ever stringent fuel economy requirements. Such efforts are mainly focused on combustion improvement and parasitic losses reduction. However, a large part of the energy input to engine is lost to cooling system, exhaust gases and other heat losses. Such losses are higher at part and low loads which is where the engine operates in normal usage conditions.

This paper analyses in detail the various energy losses at different engine operating regimes. Quantification of losses and understanding of loss mechanism serves as a starting point for future technologies to recover the lost energy.

• Quantification of losses: Losses in different systems are quantified at different engine operating regimes.
• Mechanisms of energy loss at different regimes are analyzed and presented.
• Waste heat recovery: Energy lost in the exhaust stream over the engine operating map is presented. Experiments and analysis for energy recovery are not examined in this paper.