Experimental Investigation on the Heat Transfer of a Leading Edge Impingement Cooling System for Low Pressure Turbine Vanes

Abstract

Impingement cooling through jet holes is a very attractive cooling system for heat rejection at high heat loaded areas as the leading edge of turbine vanes. Although some correlations and tools are available to dimension such systems, the variety and complexity of the flow features present in those systems still require experimental validation of real engine designs. Among the experimental techniques possible to be used, transient liquid crystal method offers good resolution as well as sufficient accuracy. Under this investigation, an impingement cooling system for the leading edge of a contrarotating power turbine (PT) representative of a small turboshaft engine was investigated experimentally. The PT vane features a very thin leading edge with high curvature and side channels rapidly turning backward. Constraints on cooling flow consumption and distribution led to a leading edge configuration with two rows of staggered jets. This particular configuration was experimentally investigated for three different Reynolds numbers around the design point by using a transient liquid crystal technique, which allows the measurement of surface distribution of heat transfer coefficient at the area of interest. Heat transfer results are presented in terms of surface distributions, impingement rows stagnation line local distributions, streamwise distributions along planes over the impingement stagnation points, span averaged streamwise local distributions, and surface averaged values. These results are then compared with available correlations from existing literature showing good matching for both maximum and averaged values. The results are also used as baseline data to discuss some of the flow features that can have effect on the heat transfer on this particular configuration.

On heat transfer and flow characteristics of jets impinging onto concave surface with varying bleeding arrangements

“…Yang et al (2014) numerically conducted unsteady predictions of flow characteristics in a cylinder channel with a single row impingement jets at a constant jet Reynolds number 15,000. For arrays of jet arrangements, the Nusselt number distributions of two staggered arrays of impingement jets on a confined concave channel with changing jet Reynolds number were experimentally investigated with the transient liquid crystal technique by Calzada and Alvarez (2012). Jung et al (2018) performed an investigation numerically and experimentally about the influence of injection angle on fluid flow and heat transfer for three staggered arrays of impingement jets.…”

Stagnation Heat Transfer on a Concave Surface Cooled by Unconfined Slot Jet

“…J ET impingement cooling/heating provides high rate of heat transfer compared with other single-phase heat transfer schemes, which has led to numerous engineering applications requiring high heat removal capacity [1][2][3][4]. Analysis of impinging jet heat transfer is complex and involves many parameters, including 1) jet Reynolds number, 2) jet-to-flat plate distance, 3) jet nozzle shape (twodimensional [slot] jet or three-dimensional [round] jet), 4) jet arrangement, for example, single or multiple arrays, 5) target surface geometry (flat plate, concave surface, and convex surface, e.g., circular cylinder), and 6) turbulence within the jet.…”