Combined 3-D Flow and Heat Transfer Measurements in a 2-Pass Internal Coolant Passage of Gas Turbine Airfoils

Abstract

A study of the flow and heat transfer in a stationary model of a two-pass internal coolant passage is presented, which focuses on the flow characteristic effects on the wall heat transfer distribution. Results are given in the upstream fully developed region. Heat transfer measurements were made with a transient technique using thermochromic liquid crystal technique to measure a surface temperature. The technique allows full surface heat transfer coefficient measurements on all the walls. Flow measurements were made with a stereoscopic digital PIV system, which measures all three-velocity components simultaneously. The coolant passage model consists of two square ducts, each having a 20 hydraulic diameter length. The ducts are connected by a sharp 180 deg bend with a rectangular outer wall. 45 deg ribs are mounted in a staggered arrangement on the bottom and top walls of both legs. The height of the ribs is equal to 0.1 hydraulic diameters. They are spaced 10 rib heights apart. The flow and heat transfer measurements were obtained at one flow condition with an inlet flow Reynolds number, based on the hydraulic diameter, of 50,000. The paper presents detailed measurement results of the flow characteristics and of the heat transfer distribution in the upstream straight leg of the passage and describes how the main and secondary flows influence the heat transfer distribution in the fully developed regions of the channel.

Comparison of Hybrid RANS-LES Simulations of Turbulent Flow and Heat Transfer in a Ribbed Duct

“…The rib height to hydraulic diameter (e/Dh) is 0.1. The Reynolds number of 50,000 was selected based on the range of real gas turbine cases, as well as to compare with the experimental test case [4]. The test section involves the inlet section of 600 mm, which allows the flow to fully develop before the ribbed section.…”

“…The simulation results are compared to the experimental results of Chanteloup et al [4] where the practical geometries and the results of 45° angled ribbed duct were provided. Therefore, the configuration of the test case is based on the experiments [4]. Their experimental uncertainty was estimated as 8 % for both the heat transfer and flow measurements.…”

“…The fluid domain was defined by four boundary conditions: velocity inlet, pressure outlet, no-slip wall and symmetry boundary conditions. At the inlet, the velocity of the air was specified at 7.82 m/s in order to give a Reynolds number of 50,000 (corresponding to the flow conditions of the experiment [4]). In order to analyse the thermal performance by scrutinizing the nondimensional heat transfer coefficient, Nusselt number, the wall heat flux to heat the main flow was specified as 300 W/m 2 .…”

“…Firstly, the mean velocity profiles of the DES solutions are compared to the experimental measurement for the quantitative analysis. The time averaged velocity profiles in the central plane of the duct (z/W = 0.5) and at the middle point between the fitth and sixth ribs are plotted against the experiments [4] in Fig. 2.…”

Numerical study of the influence of rib orientation on heat transfer enhancement in two-pass ribbed rectangular channel

“…The results indicate that the parallel ribs obtain higher heat convection strength compared with the crossed ribs. Chanteloup, Juaneda, and Bölcs (2002) study the flow field in the channel with U-shaped turn and 45 degree ribs by PIV to visualize the streamline behind the ribs. The three-dimensional velocity measurements show the position of the vortices generated by the ribs while two streams of individual secondary flows are generated at the same time.…”