WASTE HEAT RECOVERY RANKINE BASED SYSTEM MODELING FOR HEAVY DUTY TRUCKS FUEL ECONOMY ASSESSMENT

asme-orc2015 Tracking Number 67

Even in nowadays heavy duty (HD) engines which can reach 45% of efficiency, a high amount of energy is released as heat to the ambient. The increase in oil prices compels manufacturers to focus on new solutions to improve fuel efficiency of truck powertrain such as Waste Heat Recovery Systems (WHRS) [1]. Over the last few years, a lot of studies have proven that there are a lot of hurdles (cooling margin, expansion machines, control, …) [2 , 3] for a perfect match of such a system with a vehicle. This paper intends to present realistic fuel economy figures over dynamic driving cycle representative of a real long haul truck usage. The system is optimized to minimize the total vehicle fuel consumption taking into account the different penalties induced by a waste heat recovery Rankine based system installation into a truck. This analysis present and quantify all these penalties thanks to simulation model representing the engine, the vehicle driveline, the cooling system and the WHRS. This new simulation tool allows to analyse the fuel consumption under various boundary conditions (e.g. ambient conditions, different driving cycles). It also shows the importance of the application when designing WHRS and yields to a better understanding when it comes to a vehicle integration of a Rankine cycle into a truck. Means of improvements are presented and discussed, since the base fuel saving figures presented could be lower to what is usually found in the literature [4] and the design and validation of WHRS components are based on prototypes and do not represent the optimum in terms of components sizing and transient performances.