Experimental investigation of a splitting CO2 transcritical power cycle in engine waste heat recovery

Abstract

Since the great potential to improve engine efficiency was found in engine waste heat recovery, the recuperative CO2 transcritical power cycle (CTPC) was supposed to be a promising technological path, whereas high irreversibility in recuperator and low engine exhaust utilization were also found. Hence, a novel splitting design as well as the experimental system was constructed to improve the irreversibility and exhaust utilization.The main purpose of this study is to explore the splitting effect on system performances, to reveal the optimal splitting parameters and to verify the feasibility of the developed turbo-generator (TG) and print circuit heat exchangers (PCHE). Four cases were compared under various splitting ratios, and initial test results were given to reveal the performances of the developed TG and PCHE.In conclusion, the splitting design has been proved an effective way to improve the recuperative CTPC. Meanwhile, there exist different optimized splitting ratios under various operating conditions, which provides the instruction on application. The generating capacity of the TG reaches 7.57 kW, at the rotational speed of 23,875 RPM. The developed PCHE for exhaust-sCO2 (supercritical CO2) heat exchanger has also been verified a feasible exchanger with an acceptable exhaust pressure drop of 1.32 kPa in average.