Thermal Performance Analysis Of Vehicle Energy-Supplying System With ICE Waste Heat Recovery

Thermal power conversion efficiency of the internal combustion engine(ICE) accounts for 30% to 40%, the remaining heat main emissions to the environment in the form of waste heat. In the ICE waste heat, the coolant heat accounts for 20% to 30%, the exhaust waste heat accounts for 30% to 40%. Waste heat recovery with the bottom cycle of the ICE can not only effectively improve the engine fuel efficiency, but also can reduce the pollution of the environment under the condition of the same traffic capacity.Based on the background of ICE waste heat recovery, this paper analyzes features of waste heat of ICE and energy demand for vehicle under different ICE operation mode. Three kinds of ICE waste heat recovery energy-supplying systems are proposed and their energy-saving potential are analyzed.First of all, involved in the exhaust gas waste heat recovery for the engine, an vehicle energy-supplying system with exhaust gas heat recovery using organic rankine cycle(ORC) is proposed. Conduct mathematical modeling and simulation to the energy-supplying system and analyze its maximum energy saving potential. Then conduct fixed structure dimension evaporator design and analyze its actual energy saving potential. Results show that considering the maximum energy saving potential, the bottom cycle net power and overall thermal efficiency improving rate has maximum value when the engine rotational speed, which ranges from 1500 r/min to 6000 r/min, is highest. Considering the actual energy saving potential, the bottom cycle net power still has maximum value when the engine rotational speed is highest, but the overall thermal efficiency improving rate has maximum value when the engine rotational speed is 2000 r/min. In winter, considering the maximum energy saving potential, the maximum value of the bottom cycle net power and overall thermal efficiency improving rate is respectively 6.08 kW and 9.6%; Considering the actual energy saving potential, the maximum value of the bottom cycle net power and overall thermal efficiency improving rate is respectively 3.32 kW and 8.5%.Secondly,involved in waste heat recovery of exhaust gas waste heat and coolant, an vehicle energy-supplying system with ICE waste heat recovery using ORC and an vehicle energy-supplying system with ICE waste heat recovery using Kalina cycle is proposed respectively. And then conduct mathematical modeling, simulation and thermal performance analysis. Results show that the bottom cycle net power of ORC and Kalina cycle has maximum value when the engine rotational speed is highest, but the overall thermal efficiency improving rate of ORC and Kalina cycle has maximum value when the engine rotational speed is respectively 4000 r/min and 3000 r/min. In winter, the bottom cycle net power and overall thermal efficiency improving rate of ORC is respectively 10.36 kW and 18.3%; The bottom cycle net power and overall thermal efficiency improving rate of Kalina cycle is respectively 14.8 kW and 25.7%.At last, conduct the key parameters affecting analysis and exergy analys is to the energy-supplying system based on exhaust gas waste heat recovery using ORC. Explore the key parameters of ORC on the thermal performance of the system and the weak links exist in the process of energy transfer and conversion to provide guidance for system improvement.