Measurements of Heat Transfer in Circular, Rectangular and Triangular Ducts, Representing Typical Turbine Blade Internal Cooling Passages Using Transient Techniques

Abstract

Internal convection cooling of turbine blades and nozzle guide vanes in jet engines is a method used to prolong the life of those components, which are subjected to very high temperature flows from the engine’s combustion chambers. The cooling is effected by passing cold gas through the internal coolant passages situated in the core of the components, the shape of these passages in many cases being simple duct geometries. Experiments are described in which transient techniques were used in an Internal Flow Facility to measure the flow property variation and heat transfer in various geometries simulating typical internal coolant passages, at conditions representative of those found in engines. Results obtained from the three geometries studied (circular, rectangular, and triangular ducts) are compared with existing experimental data and an integral-approach theoretical prediction. In addition, flow in the circular duct with mass removal representing film cooling mass flow was also studied experimentally, and these results are compared with theoretical predictions.

Internal Cooling Passage Heat Transfer Near the Entrance to a Film Cooling Hole: Experimental and Computational Results

“…Although some areaaveraged results for different, but related geometries indicate that heat transfer enhancement does occur, the results are not in sufficient detail to provide insight into the flow field phenomena which could explain the reason for the enhancement. Ainsworth and Jones (1979) used a transient technique based on point measurements from thin film gauges to examine the effect of mass removal through discrete holes from a circular duct with the main flow at Mach 0.6. Enhancement factors on the order of 2 were observed immediately downstream of the hole, the effects being confined to a small portion of the circular periphery.…”

Gas Turbine Studies at Oxford 1969–1987

“…In the mid-1970's it became clear that short duration techniques could be employed to study the heat transfer in blade internal cooling systems and the ILPT was used in this manner [14]. Relatively simple cooling ducts were initially studied but in order to examine the detailed effects of heat transfer enhancers within these passages thermal paints were employed in a new form of tunnel.…”

“…An ILPT was used in the late 1970's to examine the heat transfer within simple ducts with film cooling holes extracting film cooling air from the duct. TFG's were used to measure local heat transfer and an integral analysis used to predict the observations [14]. This experimental method was difficult to apply when the more complex cooling duct geometries were examined.…”

Techniques for Obtaining Detailed Heat Transfer Coefficient Measurements Within Gas Turbine Blade and Vane Cooling Passages

“…Previous transient experiments on turbine cooling passages have been reported in Ref. (4) although discrete surface temperature sensors were used in this case.…”