Performance analysis of free piston linear generator coupling organic Rankine cycle system for waste heat recovery

As a novel energy conversion device, free piston linear generator (FPLG) has high potential for organic Rankine cycle (ORC) system. In this study, a FPLG simulation model has been established and the accuracy is verified, then the ORC-FPLG combined system simulation model is established for the first time. The performance study and parameter analysis has been performed. The results show that the simulation results are consistent with the experiments, all the relative errors are in the range of +/- 10%, which indicates the accuracy of FPLG simulation model. The operation parameters (such as speed, operation frequency and condenser temperature) have significant influence on the ORC-FPLG combined system. The lower the pump speed is, the higher the maximum power output and minimum power input are. The net power output of combined system increases with operation frequency, exhaust temperature, exhaust mass flow rate and cooling water flow rate. Thermal efficiency decreases with condenser temperature and pump speed. There exists an optimal operation frequency achieving the maximum net power output. When operation frequency is 16 Hz, the maximum value of net power output and thermal efficiency can reach up to 2.26 kW and 1.72%.