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Liquid Crystal Thermography for Gas Turbine Heat Transfer Measurements

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Special Issue Editors

Dr. Prashant Singh

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Guest Editor

Mechanical Engineering Department, Mississippi State University, Starkville, MS 39762, USA
Interests: liquid crystal thermography; infrared thermography; porous media heat transfer; phase change materials; carbonaceous materials; additive manufacturing

Dr. Lesley Wright

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Guest Editor

J. Mike Walker ’66 Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA
Interests: heat transfer enhancement; film cooling; convective heat transfer; heat transfer measurement techniques

Special Issue Information

Dear Colleagues,

With the ever-increasing push for achieving higher turbine inlet temperatures in gas turbines, the hot gas path components, such as nozzle guide vanes, 1st-stage stator vanes and rotor blades, their endwalls, are subjected to extremely harsh environments with gas temperatures in excess of 1500 °C. To protect these components, relatively coder air bled off from the compressor section is routed to the internal cooling passages of vanes and blades and eventually allowed to escape into the hot gas path via film cooling holes. The fundamental objective of cooling designers is to enhance the convective heat transfer coefficient between internally routed air and airfoil internals, and enhanced film cooling effectiveness and its coverage of the airfoil outer skin, with resourceful coolant usage. This task requires dedicated studies on the development of advanced heat exchangers with complex flow paths. Liquid crystal thermography enables the determination of local surface temperature through image processing of the color change when the surface temperature on which the encapsulated thermochromic liquid crystals (TLC) are sprayed upon reaches a certain temperature. This information is then used for the determination of local convective heat transfer coefficients and adiabatic film cooling effectiveness through direct or inverse heat transfer techniques.

This topic invites papers focused on the broad areas of gas turbine heat transfer where liquid crystal thermography is employed under both stationary and rotating operating conditions for detailed measurements of heat transfer quantities. Papers focused on image processing, image noise reduction, color perception, calibration methods, advanced instrumentations for image acquisition, TLC surface illumination, TLC surface preparation methods, TLC spray coating effects, TLC degradation, etc. are also invited. Papers are also sought which employ advanced solid heat diffusion modeling techniques using detailed surface temperature data through liquid crystals for the determination of the above heat transfer quantities.

Dr. Prashant Singh
Prof. Dr. Lesley Wright

Guest Editors

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Keywords

Liquid crystal thermography
Gas turbines
Heat transfer
Film cooling performance
Inverse heat transfer

Published Papers (2 papers)

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Research

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17 pages, 8099 KiB

Open AccessArticle

Systematic Comparison on Convective Heat Transfer Characteristics of Several Pin Fins for Turbine Cooling

by Jin Xu, Ke Zhang, Jingtian Duan, Jiang Lei and Junmei Wu

Crystals 2021, 11(8), 977; https://doi.org/10.3390/cryst11080977 - 17 Aug 2021

Cited by 7 | Viewed by 2563

Abstract

This paper is focused on the heat transfer augment ability and friction factor of different cross-section pin fins. An experimental study is conducted in a wide rectangular channel. The steady-state thermochromic liquid crystals (TLC) method is applied to measure the tested surface temperature. Nine sets of pin fins are employed in the experiment. The nominal diameter of all pin fins is the same value. Nine sets of pin fins have three roundness shapes (Circle, Ellipse and Oblong), three streamline shapes (Dropform, NACA and Lancet) and three quadrangle shapes (Diamond, Diamond-s and Square), respectively. The arrangement parameters of all nine shapes are kept the same. As they have the same nominal diameter and arrangement, the channel blockage ratio is the same for each pin fin set. Reynolds numbers range from 10,000 to 60,000. The pressure losses of pin fin arrays are measured to obtain friction factor. Meanwhile, the overall thermal performances of all nine sets are also considered and compared. The results show heat transfer enhancement abilities of quadrangle shape pin fins are relatively higher than the roundness and streamline shapes. Diamond-s pin fins present the largest averaged Nusselt number and overall thermal performance on the endwall for all the nine pin fins under different Re. Concerning overall thermal performance, the traditional Circle pin fin is the second best. The pressure loss of streamline shape pin fins is the lowest in these three shape types. Moreover, the characteristic of local heat transfer distribution varies substantially for different pin shapes at low Re. Full article

(This article belongs to the Special Issue Liquid Crystal Thermography for Gas Turbine Heat Transfer Measurements)

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Review

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20 pages, 3408 KiB

Open AccessEditor’s ChoiceReview

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

by Srinath V. Ekkad and Prashant Singh

Crystals 2021, 11(11), 1332; https://doi.org/10.3390/cryst11111332 - 31 Oct 2021

Cited by 12 | Viewed by 3096

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. Full article

(This article belongs to the Special Issue Liquid Crystal Thermography for Gas Turbine Heat Transfer Measurements)

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