The recovery of waste heat from HCCI engine via ORC towards optimal energy conversion

In this study, the heat recovery from HCCI (Homogeneous Charge Compression Ignition) engine exhaust gas using organic Rankine cycle (ORC) to convert to power is presented. Refrigerants R141b, R123, R245ca, R245fa and toluene have been employed as working fluids for efficiency analyses. Their performances were also compared under different turbine inlet temperature. Toluene shows the highest efficiency and least mass flow rate among these working fluids; however, R141b can generate more work than other working fluids. R141b has also been compared with toluene under the same engine working condition. Results indicate that R141b generates more power than toluene but its mass flow rate is much more than that of toluene. The inlet air pressure of the engine significantly influences the thermal efficiency of ORC and the overall efficiency of HCCI-ORC system; low speed with high engine inlet pressure performs higher efficiency.