• Title/Summary/Keyword: Transient Liquid Crystals Technique

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Measurement of Heat Transfer Coefficient in a Duct with Double Imingement Jets (이중 충돌 제트를 갖는 내부 유로의 열전달 계수 측정)

  • Kwak, Jae-Su
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.14 no.1
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    • pp.9-14
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    • 2006
  • Averaged heat transfer coefficients in the trailing edge model of a turbine blade with double impingements were measured using transient liquid crystals technique and conventional copper plate-thermocouple technique. The detailed distributions of heat transfer coefficients by transient liquid crystals technique were also presented. Results showed that increased heat transfer coefficient due to the inpingements and the averaged heat transfer coefficients increased as Reynolds number increased. Results by transient liquid crystals technique showed that the heat transfer coefficient strongly depended on the main stream temperature used in heat transfer coefficient calculation. The averaged heat transfer coefficients measured by different methods showed similar trend as Reynolds number changed, but the value varied up to 40% depending on the measurement technique.

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Improvement of Accuracy in Evaluating Hue Change Time in the Hue Detection Based Transient Liquid Crystals Technique (색상 검출방식의 천이 액정법에서 색상 변화 시간 산정의 정확도 향상)

  • Shin, So-Min;Jeon, Chang-Soo;Jung, Yong-Wun;Kwak, Jae-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.11
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    • pp.918-925
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    • 2007
  • In this paper, different criteria fur determining hue change time in the hue detection based transient liquid crystals technique were compared. Results showed that methods utilizing threshold of intensity or saturation gave many missing points and quality of the calculated results were strongly depends on the value of threshold. Wider bandwidth in the hue bandwidth method showed better distribution of calculated hue change time, but induced ambiguity in the hue change time. In the time-hue curve fitting method, the distribution of evaluated hue change time was smooth and reasonable, and, by the nature of curve fitting, the noise effect on the hue was successfully considered in calculating of the hue change time. Compared to other methods, it is expected that the time-hue curve fitting method would provide better and accurate hue change time in the hue detection based transient liquid crystals technique.

Effect of Blade Tip Geometry on Heat Transfer Coefficients on Gas Turbine Blade Tips and Near Tip Regions (가스터빈 블레이드 끝단 형상에 따른 블레이드 끝단 및 그 주변에서의 열전달 계수 변화)

  • Kwak Jae-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.4 s.247
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    • pp.328-336
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    • 2006
  • Detailed heat transfer coefficient distributions an two. types of gas turbine blade tip, plane tip and squealer tip, were measured using a hue-detection base transient liquid crystals technique.. The heat transfer coefficients an the shroud and near tip regions of the pressure and suction sides af the blade were also. measured. The heat transfer measurements were taken at the three different tip gap clearances af 1.0%, 1.5%, and 2.5% of blade span. Results shaw the overall heat transfer coefficients on the tip and shroud with squealer tip blade were lower than those with plane tip blade. By using squealer tip, however, the reductions af heat transfer coefficients near the tip regions of the pressure and suction sides were nat remarkable.

Measurement of Heat Transfer and Pressure Distributions on a Gas Turbine Vane Endwall (가스터빈 베인 끝벽의 열전달 특성 및 정압분포 측정)

  • Lee, Yong-Jin;Shin, So-Min;Kwak, Jae-Su
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.14 no.2
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    • pp.33-38
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    • 2006
  • Heat transfer coefficients and static pressure distributions on a gas turbine vane endwall were experimentally investigated in a 5 bladed linear cascade. The Reynolds number based on an axial chord length and the cascade exit velocity was 500,000. Both heat transfer and pressure measurements on the vane endwall were made at the two different turbulence intensity levels of 6.8% and 10.8%. Detailed heat transfer coefficient distributions on the vane endwall region were measured using a hue detection based transient liquid crystals technique. Results show various regions of high and low heat transfer coefficients on the vane endwall surface due to several types of secondary flows and vortices. Heat transfer coefficient and endwall static pressure distributions showed similar trends for both turbulence intensity, however, the averaged heat transfer coefficients for higher turbulence intensity case was higher than the lower turbulence intensity case by 15%.

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Effect of Groove Shape of Blade Tip on Tip Surface Heat Transfer Coefficient Distributions of a Turbine Cascade (블레이드 팁의 Groove 형상이 터빈 캐스케이드 팁 열전달 계수분포에 미치는 영향에 대한 실험적 연구)

  • Nho, Young-Cheol;Jo, Yong-Hwa;Lee, Yong-Jin;Kim, Hark-Bong;Kwak, Jae-Su
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.6
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    • pp.60-68
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    • 2010
  • In this study, the conventional plane tip, double squealer tip, and various groove tip blades were tested in a linear cascade in order to measure the effect of the tip shapes on tip surface heat transfer coefficient distributions. Detailed heat transfer coefficient distributions were measured using a hue-detection based transient liquid crystals technique. Two tip gap clearances of 1.5% and 2.3% of blade span were investigated and the Reynolds number based on cascade exit velocity and chord length was $2.48{\times}10^5$. Results showed that the overall heat transfer coefficients on the tip surface with various grooved tips were lower than those with plane tip blade. The overall heat transfer coefficient on grooved along suction side tip was lower than that on the squealer tip.

Effect of Groove Shape of Blade Tip on Tip Surface Heat Transfer Coefficient Distributions of a Turbine Cascade (블레이드 팁의 Groove 형상이 터빈 캐스케이드 팁 열전달 계수분포에 미치는 영향에 대한 실험적 연구)

  • Nho, Young-Cheol;Jo, Yong-Hwa;Lee, Youn-Jin;Kim, Hark-Bong;Kwak, Jae-Su
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.05a
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    • pp.311-318
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    • 2010
  • In this study, the conventional plane tip, double squealer tip, and various groove tip blades were tested in a linear cascade in order to measure the effect of the tip shapes on tip surface heat transfer coefficient distributions. Detailed heat transfer coefficient distributions were measured using a hue-detection based transient liquid crystals technique. Two tip gap clearances of 1.5% and 2.3% of blade span were investigated and the Reynolds number based on cascade exit velocity and chord length was $2.48{\times}10^5$. Results showed that the overall heat transfer coefficients on the tip surface with various grooved tips were lower than those with plane tip blade. The overall heat transfer coefficient on grooved along suction side tip was lower than that on the squealer tip.

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Heat Transfer Coefficients on a Gas Turbine Blade Tip and Near Tip Regions (가스 터빈 블레이드 팁과 그 주변에서의 열전달 계수)

  • Kwak, Jae-Su
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.430-435
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    • 2003
  • Detailed heat transfer coefficient distributions on a gas turbine blade tip were measured using a hue-detection base transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of a blade were also measured. Both plane tip and squealer tip blade were considered. The heat transfer measurements were taken at the three different tip gap clearance of 1.0%, 1.5%, and 2.5% of blade span. Results show the overall heat transfer coefficients on the tip and shroud with squealer tip blade were lower than those with plane tip blade. However, the reductions of heat transfer coefficients near the tip regions of the pressure and suction sides were not remarkable.

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