Experiment and analysis for an improved design of the inlet and nozzle in Tesla disc turbines

Abstract

In this article, the performance of the inlet to a Tesla disc turbine has been studied. The losses in the inlet and nozzle are known to be a major reason why the overall efficiency of disc turbines is not high. A new nozzle utilizing a plenum chamber inlet has been designed and tested here. Experiments have demonstrated less than 1 per cent loss in total pressure in the new design compared to losses in the range 13–34 per cent for the original nozzle and inlet. Other than the dramatic improvement in loss reduction, the new plenum-integrated nozzle achieves a considerable enhancement in the uniformity of the jet. This has been demonstrated here both by experimental traverses of Pitot tubes as well as computational fluid dynamics studies. The greater uniformity of the jet means that a single Pitot measurement approximately positioned at the centre of the jet would record a value close to the true centre-line total pressure, and that calculations based on centre-line values of total pressure would give, to a good accuracy, the average loss coefficient of the nozzle—inlet assembly. The uniformity of the jet also means that all disc passages would receive uniform inlet conditions; this should improve the performance of the rotor thereby further enhancing the overall efficiency of the Tesla turbine.