Abstract
In this paper, an extensive numerical study on pressure characteristics in the configuration of sudden expansion with central restriction and suction has been carried out. During study, Reynolds numbers (Re) are considered from 50 to 200, suction (S) from 2% to 10% of inlet mass flow, percentage of central restriction (CR) from 0% to 40% and aspect ratio (AR) from 2 to 6. The effects of each variable on average static pressure distribution and average stagnation pressure distribution have been studied in detail. The results have been compared with the configuration of plain sudden expansion, and sudden expansion with central restriction only. From the study, it is noted that maximum magnitude of average static pressure rise from throat increases with the increase in percentage of suction, flow Reynolds number and percentage of central restriction. This magnitude is higher at lower aspect ratio. Also, it is observed that maximum magnitude of average static pressure rise from throat is always more in case of suction configuration compared to the case of configuration of without suction. Average stagnation pressure drop at any section increases with the increase in percentage of suction and percentage of central restriction, but it decreases with the increase in Reynolds number. It is noted that higher pressure drop at any section occurs at higher aspect ratio. This pressure drop at a section is more in case of suction configuration compared to the case of without suction.
Highlights
In plain sudden expansion configuration, the fluid is required to flow through a passage of sudden increasing cross-sectional area; this results in a recovery of static pressure
Reynolds number and aspect ratio, the magnitude of average static pressure rise at a section is more in case of sudden expansion with central restriction and suction configuration compared to the case of configuration of sudden expansion with central restriction only
It is found that for all the considered Reynolds number, the average stagnation pressure drop at a section is more in case of sudden expansion with central restriction and suction configuration compared to the case of sudden expansion with central restriction only, like earlier observation
Summary
In plain sudden expansion configuration, the fluid is required to flow through a passage of sudden increasing cross-sectional area; this results in a recovery of static pressure. Since the flow is subjected to adverse pressure gradient, the flow separates from the walls resulting in substantial loss of stagnation pressure. As stagnation pressure is a matter of utmost significance in assessing the performance of various components and the cycle of a gas turbine based power plant, such losses in stagnation pressure in sudden expansion geometry may drop the overall plant efficiency. Study on pressure characteristics of fluid passing through sudden expansion configuration has been carried out by incorporating central restriction in the inlet zone and suction at the top corner on side wall. The most remarkable feature of this study is that it clearly shows the advantages of sudden expansion with central restriction and suction over the plain sudden expansion configuration or sudden expansion with central restriction only as far as the maximum magnitude of the static pressure rise is concerned
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