Liquid Crystal Thermography in Gas Turbine Heat Transfer: A Review on Measurement Techniques and Recent Investigations

Srinath V Ekkad,Prashant Singh

doi:10.3390/cryst11111332

Srinath V Ekkad, Prashant Singh

Open Access

https://doi.org/10.3390/cryst11111332

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Abstract

Liquid Crystal Thermography is a widely used experimental technique in the gas turbine heat transfer community. In turbine heat transfer, determination of the convective heat transfer coefficient (h) and adiabatic film cooling effectiveness (η) is imperative in order to design hot gas path components that can meet the modern-day engine performance and emission goals. LCT provides valuable information on the local surface temperature, which is used in different experimental methods to arrive at the local h and η. The detailed nature of h and η through LCT sets it apart from conventional thermocouple-based measurements and provides valuable insights into cooling designers for concept development and its further iterations. This article presents a comprehensive review of the state-of-the-art experimental methods employing LCT, where a critical analysis is presented for each, as well as some recent investigations (2016–present) where LCT was used. The goal of this article is to familiarize researchers with the evolving nature of LCT given the advancements in instrumentation and computing capabilities, and its relevance in turbine heat transfer problems in current times.

Highlights

Gas turbine blade cooling innovation is driven by the constant push for higher turbine inlet temperatures for higher overall gas turbine efficiency and reduced coolant usage, for overall efficient fuel management, with a broader goal to achieve lower emissions [1]
Liquid crystal and infrared thermography methods are common in the gas turbine heat transfer community, where both methods have been explored in extensive detail over the past three decades or so, where liquid crystal thermography has been in existence since the early 1980s
Liquid crystal thermography has evolved into a robust technique over the years, which is very popular in the turbine cooling community due to its ease of application on a surface and simple conversion to a local wall temperature

Summary

Introduction

Gas turbine blade cooling innovation is driven by the constant push for higher turbine inlet temperatures for higher overall gas turbine efficiency and reduced coolant usage, for overall efficient fuel management, with a broader goal to achieve lower emissions [1] Both propulsion and power generation industry-based gas turbine engines are poised to play a vital role in determining the global carbon footprint. To this end, several innovative cooling technologies have been developed and adopted in present-day turbines and these concepts are used widely in other areas involving the need for high heat dissipation rates. Earlier work by Jones and Ireland [3] from the University of Oxford was amongst the first to showcase liquid crystals and their usage in gas turbine heat transfer

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