Energy and Exergy Analysis on a Waste Heat Recovery Module for Helicopters

The exhaust of turboshaft engines contains a big amount of waste heat but does not provide propulsion power to the helicopter. Reusing the heat can increase fuel efficiency and reduce carbon emissions of the engine. This paper implements energy analyses and weight penalty estimations to a waste heat recovery module of the turboshaft engine. The components are a fuel preheating process and a power generation unit based on the organic Rankine cycle (ORC). The fuel penalty of the module consists of the fuel consumption of the following: carrying the instruments, overcoming the additional drag, and powering from the engine. Considering the high-temperature situation, working fluid of the module is chosen from benzene, R365mfc, and R245fa. The exergetic efficiency model has been validated using data from the Makila 1A1 turboshaft engine. Simulation based on a different engine, the T700 turboshaft engine, and a complete flight mission validate the energy efficiency improvement produced by the module. Results show that the module having existing technologies of the expander always cost additional fuel while increasing energy efficiency for the helicopter, but negative fuel penalties can be achieved by increasing the power-to-weight ratio of the module larger than 5.5. This research is trying to develop the field of application of ORC-based power units to a new sector of helicopters.