Abstract
In order to protect the vulnerable turbine components from extreme high temperature, coolant flow is introduced from the compressor to the disk cavity, inevitably interacting with the main flow. This paper describes an experimental investigation of the interaction between the main flow and the purge flow in a low-speed turbine cascade with three purge flow rates, Cm = 0, Cm = 1%, and Cm = 2%. In order to study the effect of the interaction between the main flow and the purge flow on the secondary flows, a Rortex method developed by Liu Chaoquan is introduced to identify the vortex in the flow field. In the meantime, a method to calculate the mean entropy production rate based on the particle image velocimetry (PIV) result is adopted to investigate the flow loss. The PIV result indicates that the purge flow has a prominent impact on the flow field of the cascade passage, changing the velocity distribution that induces a local blockage area. The results of vortex identification show that the purge flow promotes the generation of the passage vortex near the suction side. In addition, the purge flow makes the passage vortex migrate to the tip wall direction, enlarging the region affected by the secondary flow. The mean entropy production (MEP) result shows that the flow loss is mainly caused by the passage vortex. The coincidence of the high-MEP region and the location of the passage vortex indicates that the purge flow increases the secondary flow loss by affecting the formation and the migration of the passage vortex.
Highlights
With the demand of higher thermal efficiency, the inlet temperature of modern gas turbines has been increasing over the past decades, intensifying hot gas ingestion
The particle image velocimetry (PIV) result indicates that the purge flow has a prominent impact on the flow field of the cascade passage, changing the velocity distribution that induces a local blockage area
The coincidence of the high-mean entropy production (MEP) region and the location of the passage vortex indicates that the purge flow increases the secondary flow loss by affecting the formation and the migration of the passage vortex
Summary
With the demand of higher thermal efficiency, the inlet temperature of modern gas turbines has been increasing over the past decades, intensifying hot gas ingestion. In order to protect the vulnerable turbine components from hot gas ingestions, coolant air from the high-pressure compressor is introduced to the disk cavity between the rotor and stator. Excess purge flow has a negative effect on the turbine as the purge flow does not work on the turbine blades. The purge flow will interact with the main flow, causing secondary flow loss. In the last few decades, there has been a number of studies on the hot gas ingestion and the interaction of the main flow with the purge flow. Studies mainly focused on the hot gas ingestion induced by rotation of the rotor disk
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