Direct Exhaust heat recovery into Water cooled Charge Air Cooler as technical brick for improved cold start functionality

摘要

Further reduction of pollutant emissions and fuel consumption is one of the major challenges that automotive engineers currently have to overcome. Low ambient temperature testing for diesel engines will be mandatory in the near future, making cold engine start and warm up analysis important topics for researchers. In order to improve the engine operation under those critical conditions, different systems have been proposed in recent years. Previous studies have shown that heating the intake air is one of the most effective solutions to boost engine performance during warm up. In this paper a novel exhaust heat recovery system combined with a Water cooled Charge Air Cooler is presented. A gas/liquid heat exchanger, the Twin Function Exchanger, fulfilling two different functions is firstly used to recover energy from the exhaust side transferring it to the intake, and later as low pressure EGR cooler. Moreover, a complete thermal management strategy to control the intake air temperature has been put in place in order to optimize the engine behavior to be as close as possible as running conditions at 20°C. Experiments were carried out in transient load conditions of NEDC and WLTC cycles with a 2.0 liter turbocharged diesel engine, installed in a climatic test cell. Using this new system, intake air temperature was increased improving the combustion process during the engine warm up at -7°C. Important benefits on HC and CO were obtained in both cycles.