Heat transfer in the low pressure turbine interdisc cavity of an aero gas turbine engine with a closed rotating outer-rim and forced radially outward jetflow directed along the downstream disc-cob front face was partially investigated by experiment and theory as part of an advanced cooling design concept study. Within the interdisc cavity, several metal temperature transient and steady state measurements in the circumferential direction as well as the 2-D axisymmetric plane at rotating speeds of 1500 rpm and 7000 rpm were made. The results are based on matching the measured metal and air temperature at both speed levels as well as the transient behavior between the two speed levels to those predicted by the 2-D axisymmetric transient thermal model. A qualitative description of the 3-D nature of the flow field is given with the aid of CFD studies. The results indicate that the skewed forced jetflow produces a stronger variation to the level of heat transfer at high rotating speed. The jetflow partially penetrates outward through the cavity providing enhanced free-disc forced convection heat transfer (approximately 25%) at high rotating speed to about 70% of the downstream disc radial length only. Toward the rim subcavities, the level of heat transfer drops considerably compared to that of a free-disc and heat transfer along the hot rotating rim and colder flange surfaces are described by flat plate natural convection. The jetflow exits the cavity at the bore of the upstream disc by turning forward within the cavity, substantially reducing the level of heat transfer along the diaphragm of this disc, and providing forced convection heat transfer on the cob whose level is higher than the rest of the upstream disc represented by natural convection. At low rotating speed, a dominating mixed convection mechanism is evident throughout the interdisc cavity with significantly lesser variation in heat transfer. A critical Gr/Re2 value of 0.02 was established as the minimum where both natural and forced convection are important. The resulting behavior in local heat transfer coefficient and Nusselt number along the hot bolted rim and the discs are compared with those of previous investigators looking at heat transfer in a rotating cavity.

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