Modelling, sizing and testing a scroll expander for a waste heat recovery application on a gasoline engine

Waste heat recovery technologies in a mobile application emerge every time energy becomes a valuable resource. It has been the case in the 70s with oil crisis and it is starting to regain some interests now due to the continuously rising price of oil and due to the restrictive standards imposed by the different governments. This paper deals with the recovery on the exhaust gases of an internal combustion engine by using a Rankine system. The study focuses on the expander, which is one of the most important components of the system. The use of a scroll expander operating with steam is currently investigated through simulation and experimentation. This paper presents the modelling of a scroll expander. The model is a detailed model including various losses such as leakage, friction or under or over expansion. This model has been used to design and size a tailor-made scroll expander. This was necessary due to the small amount of expanders on the market and also to have a machine that fits our application. After designing the machine, a prototype has been built. It has also been tested on our prototype bench of waste heat recovery on a gasoline engine, by means of a Rankine cycle. Measured performance will be presented, analysed and compared to predictions by the model. The first results will be presented here and discussed in order to give recommendations for the design of next prototypes.