Flow Development Through HP ＆ LP Turbines, Part II： Effects of the Hub Endwall Secondary Sealing Air Flow on the Turbine＇s Mainstream Flow

Although many literatures have been focused on the underneath flow and loss mechanism, very few experiments and simulations have been done under the engines＇ representative working conditions or considering the real cav- ity structure as a whole. This paper aims at realizing the goal of design of efficient turbine and scrutinizing the velocity distribution in the vicinity of the rim seal. With the aid of numerical method, a numerical model describ- ing the flow pattern both in the purge flow spot and within the mainstream flow path is established, fluid migra- tion and its accompanied flow mechanism within the realistic cavity structure （with rim seal structure and consi- dering mainstream ＆ secondary air flow＇s interaction） is used to evaluate both the flow pattern and the under- neath flow mechanism within the inward rotating cavity. Meanwhile, the underneath flow and loss mechanism are also studied in the current paper. The computational results show that the sealing air flow＇s ingestion and ejection are highly interwound with each other in both upstream and downstream flow of the rim seal. Both the down- stream blades＇ potential effects as well as the upstream blades＇ wake trajectory can bring about the ingestion of the hot gas flow within the cavity, abrupt increase of the static pressure is believed to be the main reason. Also, the results indicate that sealing air flow ejected through the rear cavity will cause unexpected loss near the outlet section of the blades in the downstream of the HP rotor passages.