Analysis of recoverable exhaust energy from a light-duty gasoline engine

While EER (Exhaust Energy Recovery) has been widely pursued for improving the total efficiency and reducing CO2 emissions of internal combustion engines, the improvement on engine efficiency has been investigated with experimental work and numerical simulation based on a steam Rankine cycle EER system. The test was conducted on a light-duty gasoline engine connected with a multi-coil helical heat exchanger. Combining those experimental and modelling results, it demonstrates that the flow rate of working fluid plays a very important and complex role for controlling the steam outlet pressure and overheat degree. For achieving required overheat and steam pressure, the flow rate must be carefully regulated if the engine working condition changes. The flow rate has also significant influence on the heat exchanger efficiency. To achieving better heat transfer efficiency, the flow rate should be maintained as high as possible. From the simulation, it is found the EER system based on the light-duty test engine could increase the engine fuel conversion efficiency up to 14%, though under general vehicle operating conditions it was just between 3% and 8%. From the test, it is found the installation of heat exchanger can increase the exhaust back pressure slightly, the total fuel saving of the engine could be up to 34% under some operating condition.