Heat Transfer Characteristics of an Oblique Jet Impingement Configuration in a Passage With Ribbed Surfaces

Abstract

Heat transfer measurements of a confined impingement cooling configuration with ribs on the target surfaces are presented. The assembly consists of four non-perpendicular walls of which one holds two rows of staggered inclined jets, each impinging on a different adjacent wall. The ribs are aligned with the inclined jet axes, have the same pitch and are staggered to the impinging jets. The flow exhausts through two staggered rows of holes opposing the impingement wall. The passage geometry is related to a modern gas turbine blade cooling configuration. A transient liquid crystal technique was used to take spatially resolved surface heat transfer measurements for the ground area between the ribs. A comparison with the smooth baseline configuration reveals local differences and a generally reduced heat transfer for the rib-roughened case. Furthermore, lumped heat capacity measurements of the ribs yielded area averaged heat transfer information for the ribs. From the combination of ground and rib heat transfer measurements it is concluded that the overall performance of the ribbed configuration depends on the Reynolds number. Of the five investigated jet Reynolds numbers from 10,000 up to 75,000, only for the highest Re the averaged Nusselt numbers increase slightly compared to the smooth baseline configuration.

A comparative study of the local heat transfer distributions around various surface mounted obstacles

“…These values correspond to approximately 1.66%, 1.86% and 1.95% uncertainty level in the calculation of the heat transfer coefficient. Note that the flow temperature measurements indicate a slightly increased uncertainty level for the heated flow similar to Hoefler et al [19]. The contribution of model thermal properties on the total uncertainty is independent of the heat transfer coefficient and remains constant at 5%.…”

Heat Transfer Augmentation Technologies for Internal Cooling of Turbine Components of Gas Turbine Engines

“…Recent investigations of rib turbulators address different rib configurations [143][144][145][146][147][148][149][150][151][152][153][154], as well as a variety of other geometric parameters, such as continuous and truncated ribs [155,156], semiattached rib configurations [157], and effects of a turning vane arrangement within a ribbed internal cooling channel [11,149,158]. A variety of internal flow arrangements are addressed, including extraction flow effects and bleed holes [159,160], different crossflow schemes [161], conjugate heat transfer with crossing jets [162], and impingement and effusion cooling with ribbed surfaces [163,164]. Other recent investigations focus on the effects of rib arrays in combination with steam cooling [165,166] and mist/air cooling [167].…”

Basic Aspects of Gas Turbine Heat Transfer

“…The use of inclined impingement jets on shaped turbulators in irregular shaped passages can also result in very high heat transfer. In a recent study [29,30], and as shown in Figure 25, it was highlighted that directed inclined impingement can result in relatively high heat transfers from the target walls and additionally produces intense convective fluid mixing within the passage. In a turbine blade, such a combination can result in greater total heat removal by the coolant from the hot airofoil walls.…”