NUMERICAL STUDY ON FLOW AND HEAT TRANSFER IN A RECTANGULAR CHANNEL WITH 45 DEG RIB TURBULATORS AND BLEED HOLES

摘要

In this paper, the fluid flow and heat transfer in a rectangular channel with 45 deg (to the flow direction) ribs and bleed holes are studied, which is the simplification of internal passages in gas turbine blades. The influences of the bleed holes and rotation onflow and heat transfer process were investigated in three cases. In the present model, the 45 deg parallel ribs are placed on both leading and trailing surfaces. Bleed holes are drilled on the leading surface. The Reynolds number is 20,000 and the corresponding rotation number is 0.086. The inlet wall-to-coolant density ratio is maintained at 0.366 for all surfaces in the channel. The rib height to hydraulic diameter ratio is 0.096 and the rib pitch-to-height ratio is 10. A stationary case and two channel orientations cases (90 and 135 deg to the direction of the rotational plane) were investigated. Analysis of the numerical results leads to the following conclusions: Periodic distributions of flow and heat transfer coefficient are observed in all of the cases. Compared with the trailing surface, the heat transfer coefficient in the downstream region of the bleed holes increases, while in the upstream region of the holes it is not obviously influenced on the leading surface. The peak heat transfer coefficient appears on the top of the rib wall. In the two rotation cases, heat transfer on the trailing surface is enhanced by rotation while weakened on the leading surface. The average Nusselt number ratio of the whole channel is increased by 5.2% for the 90 deg rotation case while it is increased by 8.4% for the 135 deg rotation case.