A Review of Turbine Blade Tip Heat Transfer

Abstract

This paper presents a review of the publicly available knowledge base concerning turbine blade tip heat transfer, from the early fundamental research which laid the foundations of our knowledge, to current experimental and numerical studies utilizing engine‐scaled blade cascades and turbine rigs. Focus is placed on high‐pressure, high‐temperature axial‐turbine blade tips, which are prevalent in the majority of today's aircraft engines and power generating turbines. The state of our current understanding of turbine blade tip heat transfer is in the transitional phase between fundamentals supported by engine‐based experience, and the ability to a priori correctly predict and efficiently design blade tips for engine service.

Aerothermal Performance of Shroudless Turbine Blade Tips with Relative Casing Movement Effects

“…This reconstruction is described by O'Dowd et al [34]. The linear relationship between tip heat flux and wall temperature during each blow-down run determines local heat transfer coefficients (1).…”

“…Early findings on high pressure turbine blades were presented in a comprehensive review by Bunker [1], summarizing and outlining the complex aspects with shroudless turbine design. Bunker et al [2] presented detailed tip heat transfer measurements.…”

Effect of Relative Movement between the Shroud and Blade on Tip Leakage Flow Characteristics

“…The blade's tip is one of the regions with the highest heat transfer rate in the entire rotor blade, because the leakage flow driven by the large pressure difference between pressure side and the suction side is accelerated in the tip gap region and impinges on the tip. Bunker et al [1] provided a review of the previous experimental and computational investigations into the tip leakage, and pointed out that the tip surface is exposed in the most extreme aero-thermal environment within gas turbines. Kwak et al [2] reported that the overall heat transfer coefficient on the blade tip showed a higher value than that on the shroud and in the near tip regions of the blade pressure and suction sides, through their experiment.…”

Material needs for turbine sealing at high temperature

“…In the first, the blade has a flattened end, known as a shroud, which forms a circumferential link with adjacent blades, giving a high sealing efficiency. 3,4 However, the shroud increases the stresses acting on the blade, effectively reducing the turbine entry temperature or decreasing the creep life, 5 so that despite the improved sealing, removing the shroud may offer benefits. In this case, sealing is achieved by cutting a track through a porous ceramic abradable.…”