Ramp Heating in High-Speed Transient Thermal Measurement With Reduced Uncertainty

Ma, Haiteng; Wang, Z.; Wang, L.; Zhang, Q.; Zhou, Yang; Bao, Yiwang

doi:10.1115/gt2015-43012

Cited by 6 publications

(2 citation statements)

References 8 publications

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“…Step heating method (Ma et al. 26 ) is adopted to raise the inlet total temperature T 0,i in a short period. 2 s of the transient thermal measurement data were used for data processing.…”

Section: Experimental Validationmentioning

confidence: 99%

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

Wang

Jiang

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

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“…Step heating method (Ma et al. 26 ) is adopted to raise the inlet total temperature T 0,i in a short period. 2 s of the transient thermal measurement data were used for data processing.…”

Section: Experimental Validationmentioning

confidence: 99%

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

Wang

Jiang

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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show abstract

“…One default assumption was that the major tip flow structures at high speed condition could be reproduced by a redesigned low speed blade with a matched loading. Wheeler et al [23] reported different flow structures at high and low speed conditions, especially when the tip flow accelerates to a supersonic regime and involves shock structures. However, even without the impact of shock waves on the OTL, it still remains unclear if the conventional scaling method would work for high subsonic conditions.…”

Section: Introductionmentioning

confidence: 99%

On Scaling Method to Investigate High-Speed Over-Tip-Leakage Flow at Low-Speed Condition

Jiang

Zhang

et al. 2018

Journal of Engineering for Gas Turbines and Power

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Modern high-pressure turbine blades operate at high-speed conditions. The over-tip-leakage (OTL) flow can be high-subsonic or even transonic. From the consideration of problem simplification and cost reduction, the OTL flow has been studied extensively in low-speed experiments. It has been assumed a redesigned low-speed blade profile with a matched blade loading should be sufficient to scale the high-speed OTL flow down to the low-speed condition. In this paper, the validity of this conventional scaling approach is computationally examined. The computational fluid dynamics (CFD) methodology was first validated by experimental data conducted in both high- and low-speed conditions. Detailed analyses on the OTL flows at high- and low-speed conditions indicate that, only matching the loading distribution with a redesigned blade cannot ensure the match of the aerodynamic performance at the low-speed condition with that at the high-speed condition. Specifically, the discrepancy in the peak tip leakage mass flux can be as high as 22%, and the total pressure loss at the low-speed condition is 6% higher than the high-speed case. An improved scaling method is proposed hereof. As an additional dimension variable, the tip clearance can also be “scaled” down from the high-speed to low-speed case to match the cross-tip pressure gradient between pressure and suction surfaces. The similarity in terms of the overall aerodynamic loss and local leakage flow distribution can be improved by adjusting the tip clearance, either uniformly or locally.

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Heat Transfer of Winglet Tips in a Transonic Turbine Cascade

Zhong

Zhou

et al. 2016

Journal of Engineering for Gas Turbines and Power

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Understanding the heat transfer of winglet tips is crucial for their applications in high-pressure turbines. The current paper investigates the heat transfer performance of three different winglet-cavity tips in a transonic turbine cascade at a tip gap of 2.1% chord. A cavity tip is studied as the baseline case. The cascade operates at engine representative conditions of an exit Mach number of 1.2 and an exit Reynolds number of 1.7 × 106. Transient infrared thermography technique was used to obtain the tip distributions of heat transfer coefficient for different tips in the experiment. The CFD results were validated with the measured tip heat transfer coefficients, and then used to explain the flow physics related to heat transfer. It is found that on the pressure side winglet, the flow reattaches on the top winglet surface and results in high heat transfer coefficient. On the suction side winglet, the heat transfer coefficient is low near the blade leading edge but is higher from the midchord to the trailing edge. The suction side winglet pushes the tip leakage vortex further away from the blade suction surface and reduces the heat transfer coefficient from 85% to 96% span on the blade suction surface. However, the heat transfer coefficient is higher for the winglet tips from 96% span to the tip. This is because the tip leakage vortex attaches on the side surface of the suction side winglet and results in quite high heat transfer coefficient on the front protrusive part of the winglet. The effects of relative endwall motion between the blade tip and the casing were investigated by CFD method. The endwall motion has a significant effect on the flow physics within the tip gap and near-tip region in the blade passage, thus affects the heat transfer coefficient distributions. With relative endwall motion, a scraping vortex forms inside the tip gap and near the casing, and the cavity vortex gets closer to the pressure side squealer/winglet. The tip leakage vortex in the blade passage becomes closer to the blade suction surface, resulting in an increase of the heat transfer coefficient.

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Ramp Heating in High-Speed Transient Thermal Measurement With Reduced Uncertainty

Cited by 6 publications

References 8 publications

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

On Scaling Method to Investigate High-Speed Over-Tip-Leakage Flow at Low-Speed Condition

Heat Transfer of Winglet Tips in a Transonic Turbine Cascade

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