Abstract
The average film cooling effectiveness is numerically investigated under different conditions of Reynolds numbers and rotation speeds at the suction side of the turbine blade. Three locations of the injection holes row were checked from the blade leading edge at 10%, 31%, and 69% of the blade axial chord length. Coolant is injected from eleven cylindrical holes at rotational speeds ranged from 0 to 4600 rpm and blowing ratios ranged from 0.91 to 2. For the mainstream hot gases, the investigation is performed at five Reynolds numbers of 50,000, 87,300, 300,000, 500,000, and 700,000. The inlet temperature of the coolant is 650 K, while the hot gases inlet temperature is 1500 K for all the studied cases. Location 1 shows the optimum average film cooling effectiveness. Near the film holes, the enhancement in the average film cooling effectiveness of location 1 is by 22% than location 2 and 35% than location 3. For location 1, the effectiveness is enhanced by 57% as the blowing ratio increases from M=0.91 to M=2. For location 2, the effectiveness improves as the rotational speed increases from 0 rpm until it reaches the optimum value at 900 rpm. Also, it is perceived that as the Reynolds number increases, the effectiveness worsens because of the increase in the hot mainstream momentum.
Highlights
GAS turbine manufacturers aim to maximize power output, enhance the thermal efficiency, decrease the specific fuel consumption, and reduce the engineReceived: (17 January, 2021) - Revised: (16 March, 2021) - Accepted: (20 March, 2021)weight [1]
The present study aims to numerically investigate the film cooling effectiveness under different conditions from blowing ratios, Reynolds numbers, and especially rotation speeds in the range of 0 - 4600 rpm to clarify the difference in [17,18,19]
Theory and calculation The Reynolds number (Re) of the hot mainstream is evaluated based on the length of the blade chord (C), hot mainstream density (ρ∞), mainstream inlet velocity (U∞), and mainstream dynamic viscosity (μ∞) as follows: The blowing ratio (M) is an important parameter which affecting the blade surface's film cooling protection and is defined as [1]: where ρc is the density of the coolant and Uc is the coolant inlet velocity the film hole
Summary
GAS turbine manufacturers aim to maximize power output, enhance the thermal efficiency, decrease the specific fuel consumption, and reduce the engineReceived: (17 January, 2021) - Revised: (16 March, 2021) - Accepted: (20 March, 2021)weight [1]. GAS turbine manufacturers aim to maximize power output, enhance the thermal efficiency, decrease the specific fuel consumption, and reduce the engine. The rise in the turbine inlet temperature may be achieved either by enhancing blade material which is still limited or by using cooling techniques [1]. The temperature of turbine blade can be decreased by 200°C to 300°C when 1.5% to 2% of the air mass flow rate taken from the compressor is used for cooling [1]. Film cooling is intensively investigated [3]. The main investigated parameters are the blade design configuration, shape and spacing of the film holes, and characteristics of mainstream and coolant flow
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