Time Period: November 2013 to November 2017
Total Budget: 1 m€
Financing: STW (Dutch Technology Foundation), Dana Spicer
The efficiency of automotive engines arguably peaked, and only marginal increments are possible by evolving today’s technologies. However, still approximately 60% of the fuel energy is wasted as heat. If part of this energy were converted into useful work, a drastic increase in fuel-economy can be achieved. The goal of this project is to develop a combined-cycle (CC) powertrain for trucks, by coupling a heat-recovery mini‑ORC turbogenerator to the reciprocating engine, in order to attain a thermal efficiency beyond 50%. However, scaling the combined-cycle concept from the megawatts range down to tens of kilowatts, and making the system compact, light, efficient, and dynamic, as required for transport, is a formidable challenge. Achieving these objectives requires the solution of the two main unsolved problems highlighted by recent studies: 1) is it possible to identify a new suitable working fluid? 2) How can the low efficiency of small expanders be increased? The latter largely depends upon a better understanding of the gasdynamics of suitable organic fluids in the supercritical and dense-vapor regime. The applicant has already conceived a number of solutions to these problems, by leveraging on the results of previous investigations. A new method for the determination of the optimal working fluid will be developed in this project. The procedure involves the detailed simulation of the ORC system, taking as design variables, among others, the molecular model parameters of the fluid, pure or mixture. Therminol will be consulted about molecular and manufacturability aspects of the obtained theoretical fluid. Fluid property measurements and thermodynamic model development will be conducted on the best candidates. With regard to the fluid dynamics of the expander, unprecedented experiments are planned in a dedicated facility, leading to detailed measurements of the flow field of dense/supercritical organic vapors through and after supersonic and transonic nozzles. The data will be used to validate our CFD codes, in order to use them for the design of the turbine. The results of this project will be i) a novel working fluid for mini-ORC turbogenerators, and, ii) the aerodynamic design of a new high-speed turbine. Based on these results a prototype of the CC-powertrain will be realized and tested at Dana’s laboratories, in cooperation with the all project partners.