Loss analysis of the shrouded radial-inflow turbine for compressed air energy storage

Abstract

The shrouded radial-inflow turbine is widely employed as a power generation device in the compressed air energy storage (CAES) system. The loss mechanism and off-designed performance of the shrouded radial turbine are lesser known hitherto and should be deeply understood. Loss analyses of a shrouded radial turbine are conducted numerically based on the first and second laws of thermodynamics in the current study. The relationship between losses and the secondary flow has been discussed in detail. A high proportion of loss in the rotor and outblock passage is found under off-designed conditions. The secondary vortex cores and wake are the primary sources of energy dissipation, while the entropy generation mainly appears at the edge of secondary vortices. The suction-surface separation expands as the velocity ratio is decreased, making the high entropy generation scope on the cross-sectional plane wider. Reducing the seal clearance and avoiding the low velocity ratio conditions are quite necessary to reduce losses. It is recommended the outlet passage should be designed longer than the length of rotor axial chord for a uniform outflow.

Leakage flow characteristic of radial inflow turbine adopted in CAES system: Review on progress

“…Shao et al. 22 further investigated the shroud-casing leakage flow in a shrouded radial-inflow turbine for CAES system. It can be found that the wake and leakage vortex related to the case-shroud leakage flow generated primary flow loss in the outlet region of rotor, the detailed results can be observed in Figure 11.…”

“…As mentioned in reference, 22 although the case-shroud leakage flow leakage flow only performed a disturbance at outlet of rotor, its negative effect on isentropic efficiency can not be neglected. Therefore, further investigation on the case-shroud leakage flow reduction of CAES radial-inflow turbine is conducted.…”