Testing and analysis of a boundary layer turbine in steam

This paper describes the test and analysis of a small (0.42 m diameter, kW scale) Tesla style steam turbine. The machine was a bladeless disc type turbine with a radial entry and an axial exit. The work supported the commercial development of the machine by determining performance in representative environments and obtaining a realistic model of the device for use in design exploration. The results obtained also have a wider interest as they provide some insights into bladeless turbine operation in steam at the kW scale. The test programme took place in the Department of Engineering at Durham University using two facilities. The first set of testing took place in a short duration blow down rig using air and provided a general characterisation of machine performance and validation of mechanical aspects of the machine design. The second set of tests took place in a continuous running steam facility with steam provided by a hired package boiler. A feature of this rig was the supply of wet steam at turbine entry. The steam testing provided characterisation of machine performance operating at the pressure, temperatures, and with the working fluid that would be used in application. The paper contains the first published full performance maps of a boundary layer turbine operating in a steam environment. An analytic model of a boundary layer turbine was combined with simple models of the control valve, inlet nozzles and exit losses. Excellent agreement is shown between the test data and the hybrid model produced. The results of the work can be used to estimate the performance of new configurations of the boundary layer turbine and determine the viability of boundary layer turbines for different applications.