LAYOUT, INSTALLATION AND OPERATION OF A TEST BENCH FOR THE INVESTIGATION OF RANKINE-CYCLE WASTE HEAT RECOVERY SYSTEMS

Recent discussions concerning propulsion systems for commercial vehicles as well as passenger cars are mainly dominated by emissions issues, tending to forget the important role of efficiency. In the latter field, combustion engines have undergone a long evolutionary improvement during the last decades. Now, technology has reached a level where advances can only be made in small steps. For a further reduction of fuel consumption, the use of waste heat is the next logical step.
Investigation and development of such waste heat recovery systems, based on the Rankine Cycle (RC), are preferably carried out on dedicated test benches providing reproducible boundary conditions and versatile measurement options. For this purpose, a test bed has been installed at the Institute of Internal Combustion Engines and Thermodynamics at Graz University of Technology, providing superheated steam of various media, ranging from water to alcohols and other organic working fluids. The facility serves as a means for the investigation of single elements of RC waste heat recovery systems, such as the expansion engine, pumps, valves, heat exchangers or other components. This requires a modular and flexible design. The measurement of all relevant variables of state, efficiencies and output values is a challenging task, requiring some special approaches. Additionally, the system control is especially demanding, considering the complexity of the cycle.
The layout, installation and the following commissioning and operation of this system at Graz University of Technology will be treated in this paper, focusing particularly on requirements for reliable and accurate measurements.