COMPUTATIONAL STUDY OF THE EFFECT OF INLET VELOCITY PROFILE AND RIB ORIENTATION ON HEAT TRANSFER IN ROTATING RIBBED RADIAL TURBINE COOLING PASSAGES

摘要

This study investigates the effect of inlet velocity profiles and rib orientations on the Nusselt number distribution within ribbed radial turbine cooling passages representative of systems used in current engines. A triple-pass serpentine passage is investigated, which includes rib turbulators angled at 45° and 180° bends. The first two passes are radially outward and inward respectively and both have an aspect ratio of 1:4, with the third pass radially outward with an aspect ratio of 1:2. Multiple inlet velocity profiles are studied in RANS CFD simulations under both stationary and rotating conditions. The rotating simulations have Reynolds, Rotation and Buoyancy numbers representative of a passage within a HP turbine blade of a gas turbine engine. The flow structure and Nusselt number distributions are discussed in detail with the inlet velocity profile found to have a very large influence in the first pass under both stationary and rotating conditions, with smaller differences observed in the later passes. The rib orientation in the second pass was also investigated, with simulations of reversed and non-reversed rib orientation compared. Improved heat transfer characteristics were found in simulations where the ribs were orientated in the same direction for all three passages. These simulations are compared to experimental results in order to explain previous discrepancies found between experimental and CFD data from an experimental setup with complex inlet geometry.