Simulation of Thermodynamic Performance and Thermal Loss Characteristics of High Power Density Engines

Addressing the engineering challenges of high thermal load, limited engine compartment space, and complex cooling conditions in high-power-density diesel engines, this study establishes a multi-domain coupled simulation model integrating a turbocharged diesel engine with its cooling system. The cooling component modeling innovatively combines thermal balance equations with ϵ-NTU heat exchanger theory, significantly enhancing computational efficiency. Model validation is performed against dynamometer test data. Furthermore, the Specific Heat Dissipation Rate (SHDR) is introduced as an evaluation metric for cooling efficiency. Simulation studies reveal the impacts of synergistic optimization between the Miller cycle and the Geometric Compression Ratio (GCR) on engine performance. Results demonstrate that under 3800 r/min operation, employing an intake valve closing advance of 40° CA combined with increasing the GCR from 14 to 17 led to 1.9% improvement in brake efficiency, 12g/(kW·h) reduction in brake specific fuel consumption (BSFC), and 8.73% decrease in SHDR. This approach enhances both power performance and fuel economy while significantly alleviating thermal management pressure.