An experimental approach to modeling and improvement of net heat loss based on combustion efficiency in SI engines

In this paper, an improved methodology for modeling and measurement of net heat loss from the combustion process, along with a case study demonstrating its enhancement, has been developed and experimentally validated. The methodology begins with the modeling and measurement of combustion efficiency, utilizing lambda sensor measurements of oxygen concentration during intake, in-cylinder, residual gas fraction (RGF), and exhaust processes. Subsequently, based on the combustion efficiency measurements and the principles of energy conservation, net heat loss from the cylinder walls, crevices, and lubricant oil is calculated. Experimental results indicate that heat loss reaches a reasonable level near stoichiometric conditions across the full range of operating conditions tested, validating findings from other research. As part of the case study, a combustion phase control strategy (CA50) aimed at reducing heat loss has been developed and experimentally validated. The results demonstrate that net heat loss can be effectively reduced while simultaneously improving thermal efficiency in leaner zones through combustion phase control. Furthermore, the validation process included assessing improved combustion efficiency across various gasoline properties and calibrating data against existing literature, which confirmed consistent trends and magnitudes in the transition from rich to lean zones. Finally, experimental validation was conducted on a full-scale gasoline engine test bench to showcase the effectiveness of the proposed models for combustion efficiency and net heat loss, along with their improvements.