Bulb-type small-scale model turbine has been developed with various measurement instruments especially for accurate torque measurement. Main torque generated from a runner is transmitted through bearings, sealings, and a gear system to a dynamometer.
When a torque tranducer is installed between a dynamometer and a model turbine, main torque decreased by a friction from bearings, sealings, a gear system, etc. is measured. Therefore a friction torque should be compensated or main torque including friction torque should be measured in order to obtain main torque accurately. There is two methods to measure a shaft torque considering a friction torque. One is that main torque is measured by a high-accuracy torque meter and friction torque produced by bearings, sealings, and gears is measured separately and it can be compensated. The other is that mechanical torque including friction torque is directly measured with a hydrostatic bearing. In the study, a torque sensitivity measuring device of a horizontal hydrostatic bearing for a bulb-type model turbine has been developed, and the torque sensitivity has been measured under various axial thrust.