Exergy Analysis of Organic Rankine Cycle and Electric Turbo Compounding for Waste Heat Recovery

Abstract

With such tough legislation on current emission standards, car manufacturers are focusing on increasing the efficiency of their engines with the development of advance waste heat recover (WHR) technology. Organic Rankine Cycle (ORC) and Electric Turbo Compounding (ETC) system have a good potential to be used as exhaust energy recovery. This paper compares the exergy availability and losses between the ORC and the ETC. In this particular study, exhaust data from the Proton 1.6L CamPro CFE turbocharged engine was used. This particular engine already has a main turbocharger, making the added WHR as a secondary recovery system to further increase the engine efficiency. Both systems are coupled to a 1 kW electric generator for ease of comparisons. At first the available exer gy is calculated for both WHR technologies. Exergy losses from rotating the generator are analysed to finally determine the thermal effi ciency of the overall system. Exergy calculation is simplified to only account for chemical and physical exergy since kinetic and potential energy are negligible in comparison. Available exergy for ORC was significantly high which went up to 12.5 kW with the exergy losses recorded at 9.7 kW. The ETC achieved only 5 kW but had a small loss at 8x10-3 kW. Average thermal efficiency of the ORC systems was 10.7% compared to ETC which was 58.7%. It can be concluded that the complexity of the ORC system contributes to its downfall where multiple components increase its exergy losses compared to the simplistic design of an ETC.

Simulation of the Performance of an Electrically Turbocharged Engine Over an Urban Driving Cycle

“…The CFE engine was chosen because it came from a small passenger car, had a readily available brake torque curve, and had a one-dimensional model that had been verified by Ismail et al [31] when studying the turbocharger marching for residual concentration reduction. The model was found to have an accuracy of 72.6 percent on average across the entire engine speed range and 99 percent between 2000 and 6500 rpm [11]. Table 1 shows the engine specification of the CamPro CFE turbocharged engine.…”