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Numerical Analtsis of Unsteady Wake on Heat Transfer Characteristics of Blade

Author: WangMeiLi
Tutor: GuoZuoZuo
School: Tohoku Electric Power University
Course: Thermal Power Engineering
Keywords: unsteady wake spectrum analysis numerical simulation field heat transfer
CLC: TK124
Type: Master's thesis
Year: 2011
Downloads: 35
Quote: 0
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Abstract


One of the main factors of unstable flow in turbine comes from the spread of upstream vane wake. Vane wake causes unstable velocity and temperature of periodic changes by free flow, and furthermore influences cooling field and heat transfer of downstream blade. Consequently, the research of unsteady wake has important significance to the design of optimizing blade of cooling.This paper adopts SST k-ωturbulence model based on SIMPLE algorithm and discretizes the control equation using finite volume method. Firstly, vane wake unsteady characteristic of cascade on the condition of no film cooling hole was simulated. Through the spectrum analysis of unsteady wake, the frequency of wake vortex shedding was confirmed. The influence on field around downstream blade and heat transfer of blade from wake on the condition of different axial distance and different speed was analyzed based on the view of energy loss. It also analyzed influence of field and heat transfer of blade of different height blade and different time. Results show that the frequency of wake vortex shedding change a little with the increase of axial distance, but the power spectrum energy decreases gradually. This means that energy loss of blade field reduce with increasing of axial distance, axial inhomogeneity of field around blade weakens gradually, and heat transfer of leading edge decreases. It also shows that the frequency of wake vortex shedding increase with increase of rotational speed, and the power spectrum energy is large. At the same time, the value of entropy of blade surface field increases gradually. This shows that the role of centrifugal force causes the disturbance of wake vortex in the field more intense and the energy loss is also bigger.Then vane wake unsteady characteristic of cascade with three row film cooling hole were simulated. The unsteady characteristic of wake was studied and shedding frequency of wake vortex was analyzed by spectrum analysis. At the same time, the influence of field around downstream blade and heat transfer of blade from wake on the condition of different blowing ratio and different speed was analysis based on the view of energy loss. The results indicate that the frequency of wake vortex shedding change a little with the increase of blowing ratio, and flow momentum increases. At the same time, fluid has enough rigidity. So the effect of heat transfer is better. It also shows that the frequency of wake vortex shedding increase with increase of rotational speed, and energy loss is large. The flow direction of jet holes start to shift by the increase of rotational speed, and heat transfer coefficient increases gradually along the direction of jet flow direction. Due to the affection of wake, the flow direction of the first row hole shift toward blade tip. At the same time, the role of wake strengthens turbulence intensity, improving heat transfer coefficient.

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Thermal Engineering Theory > Heat Transfer
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