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Subject: search.filters.subject.Cooling performance

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    INFLUENCE of COOLANT on COOLING PERFORMANCE SENSITIVITY of INTERNALLY CONVECTIVE TURBINE VANE
    (2021-01-01)
    Chotroongruang, Thanapat
    ;
    Prapamonthon, Prasert
    ;
    Thongdee, Rungsimun
    ;
    Thongmuenwaiyathon, Thanapat
    ;
    Sun, Zhenxu
    Based on the Brayton cycle for gas-turbine engines, the high thermal efficiency and power output of a gas-turbine engine can be obtainable when the gas-turbine engine operates at high turbine inlet temperatures. However, turbine components e.g., inlet guide vane, rotor blade, and stator vane request high cooling performance. Typically, internal cooling and film cooling are two effective techniques that are widely used to protect high thermal loads for the turbine components in a stateof- the-art gas turbine. Consequently, the high thermal efficiency and power output can be obtained, and the turbine lifespan can be prolonged, also. On top of that, a comprehensive understanding of flow and heat transfer phenomena in the turbine components is very important. As a result, both experiments and simulations have been used to improve the cooling performance of the turbine components. In fact, the cooling air used in the internal cooling and film cooling is partially extracted from the compressor. Therefore, variations in the cooling air affect the cooling performance of the turbine components directly. This paper presents a numerical study on the influence of the cooling air on cooling-performance sensitivity of an internally convective turbine vane, MARK II using the computational fluid dynamics (CFD)/conjugate heat transfer (CHT) with the SST k- turbulence model. Result comparisons are conducted in terms of pressure, temperature, and cooling effectiveness under the effects of the inlet temperature, mass flow rate, turbulence intensity, and flow direction of the cooling air. The cooling-performance sensitivity to the coolant parameters is shown through variations of local cooling effectiveness, and area and volume-weighted average cooling effectiveness.
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    Understanding of temperature and cooling effectiveness sensitivity of a film-cooled vane under coolant inlet temperature effect: A case study
    (2019-09-01)
    Prapamonthon, Prasert
    ;
    Yin, Bo
    ;
    Yang, Guowei
    ;
    Zhang, Mohan
    This work presents a case study of the relationship between temperature and cooling effectiveness of a film-cooled vane under effect of coolant inlet temperature in two aspects based on the actual and base coolant inlet temperatures. Results are conducted in terms of temperature, cooling effectiveness, and heat transfer coefficient based on surface and volume analyses using CFD/CHT approach. Sensitivity of the vane temperature and cooling effectiveness under this effect is discussed also. The results show that for the surface basis, although the cooling effectiveness obtained from the actual coolant inlet temperature is quite straightforward and follows the definition of the cooling effectiveness directly, the cooling effectiveness obtained from the base coolant inlet temperature is more understandable because it corresponds to the variation of the surface temperature. Based on the volume basis and the base coolant inlet temperature, the 8% increase in the coolant inlet temperature causes the reduction of the average and maximum cooling effectiveness, which corresponds to 18 K and 25 K increments in the average and minimum temperatures, respectively. However, when the actual coolant inlet temperature is used, the variation of the cooling effectiveness is rather insensitive due to the reduction of heat flux on the hot-side wall.
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    Numerical prediction of cooling performance sensitivity of 1st stage nozzle guide vane under aerothermal conditions
    (2019-01-01)
    Prapamonthon, Prasert
    ;
    Yin, Bo
    ;
    Yang, Guowei
    ;
    Zhang, Mohan
    To obtain high power and thermal efficiency, the 1<sup>st</sup> stage nozzle guide vanes of a high-pressure turbine need to operate under serious circumstances from burned gas coming out of combustors. This leads to vane suffering from effects of high thermal load, high pressure and turbulence, including flow-separated transition. Therefore, it is necessary to improve vane cooling performance under complex flow and heat transfer phenomena caused by the integration of these effects. In fact, these effects on a high-pressure turbine vane are controlled by several factors such as turbine inlet temperature, pressure ratio, turbulence intensity and length scale, vane curvature and surface roughness. Furthermore, if the vane is cooled by film cooling, hole configuration and blowing ratio are important factors too. These factors can change the aerothermal conditions of the vane operation. The present work aims to numerically predict sensitivity of cooling performances of the 1<sup>st</sup> stage nozzle guide vane under aerodynamic and thermal variations caused by three parameters i.e. pressure ratio, coolant inlet temperature and height of vane surface roughness using Computational Fluid Dynamics (CFD) with Conjugate Heat Transfer (CHT) approach. Numerical results show that the coolant inlet temperature and the vane surface roughness parameters have significant effects on the vane temperature, thereby affecting the vane cooling performances significantly and sensitively.