Energy recovery efficiency analysis of organic Rankine cycle system in vehicle engine under different road conditions

•Simulation model of vehicle is established using GT-Suite.•Actual engine operating condition is obtained under different road conditions.•The road condition which is suitable for ORC system to use is obtained. The organic Rankine cycle (ORC) system can effectively recover the waste heat energy of the engine, but its performance is substantially affected by the operating conditions of the engine. The road conditions control the operating conditions of the engine, which determine the amount of waste heat energy of the engine and the performance of the ORC system. Therefore, the energy recovery efficiency of the ORC system in a vehicle engine under different road conditions must be studied. This study establishes a vehicle model including engine, ORC system, power transmission system, and control system, and verifies the accuracy of the engine and ORC system. The vehicle model is used to simulate and analyze the operating characteristics and energy recovery efficiency of the engine and ORC system under New York City Cycle (NYCC) and motorway of Common Artemis Driving Cycles (CADC) road conditions. Results show that the exhaust energy is low and fluctuates frequently under NYCC road condition, ranging from 5.45 kW to 24.28 kW, with an average exhaust energy of 10.4 kW and an average energy recovery efficiency of 1.43%. The exhaust energy is high and fluctuates slightly under motorway of CADC road condition, ranging from 5 kW to 44.5 kW, with an average exhaust energy of 26.9 kW and an average energy recovery efficiency of 5.50%. Therefore, the ORC waste heat recovery system is more suitable for motorway road conditions with high, stable vehicle velocity, while the urban road conditions with low or fluctuant vehicle velocity must be avoided as much as possible.