The present work discusses a novel oxyfuel combustion method named internal combustion rankine cycle (ICRC) used in reciprocating engines. Water is heated up through heat exchanger by exhaust gas and engine cooling system, and then injected into the cylinder near top dead center to control the combustion temperature and in-cylinder pressure rise rate, meanwhile to enhance the thermo efficiency and work of the combustion cycle. That is because injected water increases the mass of the working fluid inside the cylinder, and can make use of the combustion heat more effectively. Waste heat carried away by engine coolant and exhaust gas can be recovered and utilized in this way.
This study investigates the effect of water injection temperature on the combustion and emission characteristics of an ICRC engine based on self-designed test bench.
The results indicate that both indicated work and thermal efficiency increase significantly due to water injection process. The increase of water injection temperature results in higher peak in-cylinder pressure and improves MEP. This phenomenon is more obvious under higher engine load. The optimal water injection duration for the best performance and thermal efficiency rises with the increase of water temperature. Furthermore, engine stability becomes better under higher water injection temperature. Higher Water injection temperature cause lower HC emissions and higher NOx emissions. However, NOx emissions stay under low level because water injection process reduces in-cylinder temperature significantly.