Thermal analysis and efficiency optimization of diesel- stirling combined cycle with CI engine exhaust heat recovery

Abstract

Nowadays, because of their widespread applications in thermal efficiency enhancement, combined power cycles have attracted the attention and interest of the researchers. This research is devoted to provide a comprehensive modeling and thermal analysis of a new arrangement of combined cycle based on a compression ignition (CI) engine and α-type Stirling engine. Furthermore, the influences of the diesel exhaust gas temperature and Stirling working pressure on Stirling and combined engines power and efficiency are examined considering various scenarios. The Stirling engine cycle is combined with a CI engine cycle to recover the CI engine exhaust gas waste heat. OM355 experimental results have been considered for generated power, thermal balance and exhaust gas temperature analysis. According to thermal analysis and the obtained results, it is revealed that about 34% of input energy wastes by the exhaust gas. The simulation of α-type Stirling engine is also performed and the Solo V161 experimental results were employed for validation. Furthermore, Stirling engine heater is suggested for installation on the exhaust pipe in order to analyze the new proposed combined cycle properties. Thermodynamic analysis of combined cycle is implemented and thermal efficiency and net power are obtained for Striling engine, diesel engine and combined cycle for various Stirling engine and diesel exhaust temperatures. The results indicate that, by installing a Stirling engine heater on the exhaust pipe of the CI engine, about 9.3 kW of the wasted heat could be recovered. Compared to the ordinary engine, coupled engines heat balance reveals higher thermal efficiency and combined cycle power which increase by 7.3% and 5.6%, respectively.

Keywords: CI engine; Combined cycle; Heat recovery; Stirling engine; Thermal efficiency.