Heat Transfer and Pressure Loss Measurements of Matrix Cooling Geometries for Gas Turbine Airfoils

Abstract

Matrix cooling systems are relatively unknown among gas turbines manufacturers of the western world. In comparison to conventional turbulated serpentines or pin-fin geometries, a lattice-matrix structure can potentially provide higher heat transfer enhancement levels with similar overall pressure losses. This experimental investigation provides heat transfer distribution and pressure drop of four different lattice-matrix geometries with crossing angle of 45 deg between ribs. The four geometries are characterized by two different values of rib height which span from a possible application in the mid chord region up to the trailing edge region of a gas turbine airfoil. For each rib height two different configurations have been studied: one having four entry channels and lower rib thickness (open area 84.5%), one having six entry channels and higher rib thickness (open area 53.5%). Experiments were performed varying the Reynolds number Res, based on the inlet sub-channel hydraulic diameter, from 2000 to 12000. Heat transfer coefficients were measured using steady state tests and applying a regional average method; test models have been divided into 20 stainless steel elements in order to have a Biot number similitude with real conditions. Elements are 10 per side, 5 in the main flow direction and 2 in the tangential one. Metal temperature was measured with embedded thermocouples and 20 thin-foil heaters were used to provide a constant heat flux during each test. A specific data reduction procedure has been developed so as to take into account the fin effectiveness and the increased heat transfer surface area provided by the ribs. Pressure drops were also evaluated measuring pressure along the test models. Uniform streamwise distributions of Nusselt number Nus have been obtained for each Reynolds number. Measurements show that the heat transfer enhancement level Nus/Nu0 decreases with Reynolds but is always higher than 2. Results have been compared with previous literature data on similar geometries and show a good agreement.

Evaluation of Wall Heat Transfer in Blade Trailing-Edge Cooling Passage

“…Tarchi et al [4] have conducted an experimental study of an innovated trailing-edge internal cooling design with streamwise/spanwise staggered elliptic pin-fins and pentagonal arranged circular pin-fins. Similar configuration was also investigated by Carcasci and Simonetti [5], Facchini et al [6] and Bianchini et al [7] on the effect of trailing-edge turning flow on cooling effectiveness. A recent U.S. patent proposed by Liang [8] demonstrated a novel turbine blade with multiple trailing-edge cooling holes design.…”

Effect of Mesh Topologies on Wall Heat Transfer and Pressure Loss Prediction of a Blade Coolant Passage

“…Among these studies, Tarchi et al [6] carried out an experimental research by proposing some innovated trailing-edge internal cooling designs with a pentagonal arranged circular pin-fin and staggered elliptical pin-fin. Similar configurations were further investigated by Carcasci and Simonetti [7] with involving turning flow effect in front of cooling passage.…”

“…A comprehensive review paper by Han and Rallabandi [1] summarized recent advancements in this field including both internal cooling passage and external film cooling jets. For internal cooling, a common technique is to insert pins, ribs or other obstacles to enhance wall heat transfer [2] and the blade cooling passage performance has been studied experimentally and numerically for many years using various configurations of staggered or in-line arrangement with cylindrical [3][4][5][6][7][8][9][10] or elliptical pin-fins [4,6,8] (see Table 1). Among these studies, Tarchi et al [6] carried out an experimental research by proposing some innovated trailing-edge internal cooling designs with a pentagonal arranged circular pin-fin and staggered elliptical pin-fin.…”

Film Cooling Effectiveness Downstream of Optimised Cross Corrugated Slot Geometry with Exit Shaping

“…This forms a vortex where the flow moves along the channels on one side, reflect from the side wall and continue in the opposing channels. A number of studies have been conducted on lattice geometries including stationary experiments by Bunker (2004) and Carcasci et al (2014) and rotating experiments by Acharya et al (2004) to obtain heat transfer and pressure loss characteristics. Goreloff et al (1990) also measured cooling effectiveness around the external surface of a blade.…”