Measurements of the Performance of an Air Turbine Stage at Positive and Negative Mass Flow and Rotational Speed (Four-Quadrant Characteristics)

Abstract

In the mass flow range −1.3 ≤ m/m N ≤ + 1.3 (N = nominal point) and in the speed range −1.0 ≤ n/n N ≤ +1.0 the four-quadrant characteristic of a turbine stage was completely measured. A turbine stage delivers power only at a positive speed above a certain mass flow rate and at very low negative speed and negative mass flow. In all other ranges it absorbs power. The power requirement is very high in the case of positive mass flow and negative speed. At 80 percent of the nominal mass flow and negative nominal speed the power absorbed amounts to 2.5 times the nominal power. The torque curves are very smooth. The standstill torque at nominal mass flow amounts to 2.1 times the nominal torque. At a very low mass flow the turbine works as a compressor. The four-quadrant characteristics can be represented in the form of φ, ψ curves.