Performance test rig and its measuring system for centripetal turbines of micro-gas-turbines

For the purpose of developing micro-gas-turbines of 100 kW capacity, a high speed precision performance test rig for centripetal turbines has been designed and built. Intensive analyzing and exploring work has been performed concerning key problems of its principal components, like ways of supporting the rotor and their dynamic balancing. A hydraulic dynamometer for a maximal rotational speed of 50000r. p. m and with a maximal power absorbing capacity of 150 kW is provided. A simple and practical way of calibrating the hydraulic dynamometer, which had been a problem before, is proposed and has been used. Errors committed in determining the turbine's efficiency by using the torque-speed method, or by using the calculation method with the help of thermodynamic measurements, are being analyzed together with the influencing factors concerned. Results show, that the error of the former method is less than that of the latter, respectively being (0.382% and 0.988%. Regardless of which method is being used, the efficiency error's influencing factors of total temperature and of mass flow are smaller by an order of one or two than those of physical quantities like pressure, torque and rotational speed. Therefore, endeavors should be made to raise the measuring precision of total temperature and mass flow as much as possible. Figs 4, tables 3 and refs 11.