A novel organic Rankine cycle system for heavy duty Diesel engines

Due to increasing CO2 emissions and fuel costs there is a growing interest in heat to power conversion techniques for Heavy Duty Diesel Engines (HDDE). The use of Rankine Cycle (RC) and Organic Rankine Cycles (ORC) on long-haul HDDE is seen as a possible way to improve the overall system efficiency. The key consideration in the research and development efforts for ORCs is to investigate and identify technical paths that may improve the practicality of such a concept. For this, simple solutions are vital for a timely deployment of the technology to meet the anticipated CO2 regulations. To provide a potential solution, this paper presents a novel ORC system to address the shortcomings of the conventionally proposed cascade system. This novel system is a function of a new working fluid (i.e. water-propanol blend), its associated cycle operating mode (i.e. superheated expansion) and an innovative architecture (i.e. direct engine block heat recovery). Simulations conducted in Aspen HYSYS showed that the system delivered a 20% improvement in power, a 2/3rd reduction in the total heat exchanger footprint, and a reduced complexity compared to the cascade system. Implementation of this system at rated HDDE condition generated 6.9% of additional engine crankshaft power.