Impact of advanced blade configuration on small scale cryogenic axial turbine performance

Abstract

Cryogenic Energy Storage (CES) technology which uses liquid air/nitrogen as energy carrier has attracted considerable attention recently due to its high exergy density (762kJ/kg) compared to other energy storage technologies. Liquid air/nitrogen occupies about 1/700 of the volume of its gaseous phase making it easier to store and transport. The stored energy can be recovered through a direct expansion process where the expander design and performance have a major effect on the efficiency of the energy conversion process. In this work the effects of blade configuration including lean (-15° to +15°) and twist (-20° to +30°) angels for rotor and stator of a small scale axial cryogenic turbine have been investigated using ANSYS CFX 3D modelling. Results showed that at rotor lean angle of -10°, twist angle of 0° and hub / tip ratio of 0.83, the improvement in efficiency is 4.28% while for the same angles and hub / tip ratio of 0.66, the efficiency improvement is 1.35%. On the other hand, for rotor lean angle of 0° and twist angle of 30°, the improvement in efficiency for hub / tip ratio of 0.83 is 4.2% and for rotor lean angle of 0° and twist angle of 150, the improvement in efficiency for hub / tip ratio of 0.66 is 2.66%. the improvement was noticed when twist and lean angles for both the rotor and stator were changed simultaneously.