Utökning av mätområdet för turbinverkningsgraden på avgasturbo
The Goal with this Master of Science thesis is to expand the possible turbine efficiencymeasurements on an exhaust turbocharger. It was done as a part of the CICERO competencecentre. To feed the turbine with air a special flow rig has been used. Instead of loading theturbine by just restricting the compressor flow a docking system for an electrical dynamometer isdesigned to use the dynamometer as an additional loading source. By using an electricaldynamometer as loading device for the turbine, measurements are not depending on compressorperformance.A large part of the work consists in designing accessories for the dynamometer. In order toload the turbine, the turbine shaft is slightly modified in one end. Another separate shaft thenconnects the turbine shaft with the dynamometer. Along this shaft there are 4 bearings to avoidcritical speeds of the shaft. The dynamometer consists in an electrical motor mounted in apendulum suspension in order to measure the induced torque. The Torque is measured by straingages applied to a thin steel plate which is attached to the pendulum suspension. The load on theturbine shaft is controlled by altering an applied resistance to the electrical motor. Different testsare made to validate the test-setup and to compare measurements when loading with thecompressor to those when loading by dynamometer.The focus in this report lies on lower rotational speeds of the turbine and the dynamometer isdesigned to run at a maximum design speed of 50000 rpm?s. The efficiency is illustrated atdifferent blade speed ratios for different turbine speeds. There are also results describingpressure ratio as a function of reduced mass flow at different turbine speeds.Several calibrations of the measuring equipment are made and above all the dynamometerproved hard to calibrate with good accuracy.