علي اكبر مهدوي

About one third of fuel energy in internal combustion engines is wasted through exhaust gases and only about one third of fuel energy is converted into useful work. The development of organic Rankine cycles for the vehicle application in order to recover the waste heat energy of the engine are challenged by transient conditions, variable operating profiles, low efficiency, cost and limited space. This work investigated the performance of organic Rankine cycle with the aim of maximum utilization of the wasted heat and minimization of carbon dioxide emission in accordance with recovery limits. At first, in order to determine the design point of the cycle and the boundary conditions, the base engine powertrain was simulated in the GT-Power software. The organic Rankine cycle was modeled at the design point and initial boundary conditions in the EES software. After eva‎luating the operational conditions of the cycle, the heat recovery system was modeled in the MATLAB software environment and the capacity and operational points of the cycle components were determined. At the end, multi-objective optimization was done with sensitivity analysis regarding the heat exchangers surface. The results showed that at a constant engine load, the cooling fluid at low engine speed, and the exhaust gases at high engine speed are suitable for utilization from the viewpoint of exergy. The most share of total exergy destruction is related to evaporator, turbine, condenser and pump respectively. In the best case, the total exergy efficiency reaches about 22%. According to the carbon footprint analysis, it was considered necessary to reduce the carbon cost rate for pump and evaporator components. Maximum output power in the extra-urban phase of the driving cycle, was obtained 3 kW. The average thermal and exergy efficiency in the urban and extra-urban phases was reached to 13% and 25.53% respectively in the highest value. In the urban and extra-urban phase, the maximum pressure drop of exhaust gases was limited to 0.8 kPa and 2.5 kPa, respectively. According to the sensitivity analysis, the considered heat exchange surfaces for purposes such as cycle output power, energy efficiency, allowable pressure drop and carbon dioxide production, the optimal range was obtained.

سيكل آلي رانكين , حرارت اتلافي موتور , ردپاي كربني , آناليز اگزرژي , سيكل رانندگي

organic rankine cycle , Waste Heat Recovery , Carbon footprint , Exergy Analysis , Driving cycle

Ali Akbar Mahdavi

Amir Hossein Kakaei