Thermal Performance of V-Shaped and X-Shaped Ribs in Trapezoidal Cooling Channels

Wei-Jie Su,Yao-Hsien Liu

doi:10.3390/en14164826

Abstract

Convective heat transfer enhancement using rib turbulators is effective for turbine blade internal cooling. Detailed heat transfer measurement of X-shaped ribs in a trapezoidal cooling channel was experimentally conducted using infrared thermography. The novel X-shaped ribs were designed by combining two V-shaped ribs, and more secondary flows generated by the X rib delivered higher heat transfer enhancement. The Reynolds numbers in this study were 10,000, 20,000, and 30,000. These ribs were installed on two opposite walls of a trapezoidal channel in a staggered arrangement. The rib pitch-to-height ratios were 10 and 20, and the rib height-to-hydraulic diameter ratio was 0.128. Results indicated that higher heat transfer distribution was observed in the vicinity of the shorter base in the trapezoidal channel. The full X-shaped ribs and the V-shaped ribs demonstrated the highest Nusselt number ratios among all the cases. Although full X-shaped ribs contributed to higher heat transfer improvement due to intensified secondary flows, they also caused significant pressure loss. Therefore, the cutback X-shaped ribs were proposed by removing a segment in the rib at either upstream or downstream region. Consequently, the upstream cutback X-shaped rib and the V-shaped rib produced the highest thermal performance in this trapezoidal channel.

Highlights

Internal cooling channels in gas turbine blades are generally roughened with ribs to achieve higher heat transfer enhancement [1]
Heat transfer and pressure loss caused by these ribs are related to the parameters such as rib angle of attack, pitch-to-height ratio (P/e), height-to hydraulic diameter ratio (e/Dh), channel aspect ratio, and Reynolds number [2,3,4]
A numerical investigation found that W-shaped ribs increased heat transfer enhancement at the cost of higher pressure drop and the optimal pitch-to-rib height ratio was 10 [17]

Summary

Introduction

Internal cooling channels in gas turbine blades are generally roughened with ribs to achieve higher heat transfer enhancement [1]. Heat transfer and pressure loss caused by these ribs are related to the parameters such as rib angle of attack, pitch-to-height ratio (P/e), height-to hydraulic diameter ratio (e/Dh), channel aspect ratio, and Reynolds number [2,3,4]. It was found that the correlation for the average heat transfer coefficient in the ribbed channel can be developed using the rib spacing, height, and Reynolds number [5].

Results

Conclusion