scholarly journals Research on the Hole Length Ratio of Fan-Shaped Holes in Flat Plate Film Cooling

2021 ◽  
Vol 9 ◽  
Author(s):  
Xun Zhou ◽  
Runxuan Qin ◽  
Le Cai
Keyword(s):  
Flow Structure ◽  
Film Cooling ◽  
Calculation Model ◽  
Cylindrical Part ◽  
Length Ratio ◽  
Cooling Efficiency ◽  
Average Efficiency ◽  
Blowing Ratio ◽  
Total Length ◽  
Narrow Region

To study the influence of different hole length ratios on the flow structure and film cooling efficiency, a calculation model of fan-shaped hole was constructed and numerically studied. The effect of different hole length ratios on the cooling efficiency under different blowing ratios was compared and analyzed. The results showed that as the blowing ratio increases, the overall average efficiency of most of the hole length ratio cases first increases and then decreases. Only in the case with a cylindrical part length/total length ratio of 0.5 did the efficiency continue to increase. When the blowing ratio is small, the spanwise average efficiency of each hole length ratio case is closer, but the flow structure and efficiency distribution are quite different. For the medium blowing ratio, the overall average efficiency of the small hole length ratio case is higher, and the efficiency decreases as the hole length ratio increases. When the cylindrical part length/total length ratio is further increased to 1, the cooling efficiency region basically converges into a spanwise narrow region. For larger blowing ratio conditions, after 10D after the hole outlet, the case with a cylindrical part length/total length of 0.5 is more efficient.

Experimental and Numerical Investigation on Film Cooling Performance and Flow Structure of Film Holes

2019 ◽  
Author(s):  
Nan Cao ◽  
Xue Li ◽  
Ze-yu Wu ◽  
Xiang Luo
Keyword(s):  
Flow Visualization ◽  
Numerical Investigation ◽  
Flow Structure ◽  
Film Cooling ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Visualization Experiment ◽  
Shaped Hole

Abstract Discrete hole film cooling has been commonly used as an effective cooling technique to protect gas turbine blades from hot gas. There have been numerous investigations on the cylindrical hole and shaped hole, but few experimental investigations on the cooling mechanism of the novel film holes with side holes (anti-vortex hole and sister hole) are available. This paper presents an experimental and numerical investigation to study the film cooling performance and flow structure of four kinds of film holes (cylindrical hole, fan-shaped hole, anti-vortex hole and sister hole) on the flat plate. The film holes have the same main hole diameter of 4mm and the same inclination angle of 45°. The adiabatic film cooling effectiveness is obtained by the steady-state Thermochromic Liquid Crystal (TLC). The flow visualization experiment and numerical investigation are performed to investigate the flow structure and counter-rotating vortex pair (CRVP) intensity. The smoke is selected as the tracer particle in the flow visualization experiment. The mainstream Reynolds number is 2900, the blowing ratio ranges from 0.3 to 2.0, and the density ratio of coolant to mainstream is 1.065. Experimental results show that compared with the cylindrical hole, the film cooling performance of the anti-vortex hole and sister hole shows significant improvement at all blowing ratios. The sister hole can achieve the best cooling performance at blowing ratios of 0.3 to 1.5. The fan-shaped hole only performs well at high blowing ratios and it performs best at the blowing ratio of 2.0. Flow visualization experiment and numerical investigation reveal that the anti-vortex hole and sister hole can decrease the CRVP intensity of the main hole and suppress the coolant lift-off because of side holes, which increases the film coverage and cooling effectiveness. For the sister hole, the side holes are parallel to the main hole, but for the anti-vortex hole, there are lateral angles between them. The coolant interaction between the side holes and main hole of the sister hole is stronger than that of the anti-vortex hole. Therefore, the sister hole provides better film cooling performance than the anti-vortex hole.

Computational Study on Pressure Side Film Cooling and Flow Structure

2013 ◽  
Author(s):  
Radheesh Dhanasegaran ◽  
Girish Venkatachalapathy ◽  
Nagarajan Gnanasekaran
Keyword(s):  
Flow Structure ◽  
Film Cooling ◽  
Computational Study ◽  
Pressure Side ◽  
Cooling Performance ◽  
Pressure Surface ◽  
Blowing Ratio ◽  
Commercial Code ◽  
Cylindrical Holes ◽  
Specific Geometry

A computational investigation is carried out to understand the film cooling performance and flow phenomenon on a pressure side of gas turbine airfoil. A specific geometry with multiple rows of cylindrical holes is considered on the pressure surface and opposite to which a flat surface is kept so as to avoid effect of imposed flow conditions. Meshing of the present model is done by using GAMBIT. Computations are carried out with K-epsilon Realizable model available in the commercial code FLUENT. The film cooling performance is discussed with flow structure followed by the effectiveness distribution on the pressure surface. The blowing ratio is varied from 0.4–2.4 and it is found that, at very low blowing ratio cases in the initial part of the pressure surface higher effectiveness values are observed but at higher blowing ratio these values become very low whereas close to the trailing edge side the effectiveness distribution is just the reverse. It was found that the optimum blowing ratio was close to unity where better flow and temperature distribution were observed.

Experimental Flow Structure Investigation of Compound Angled Film Cooling

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Vipluv Aga ◽  
Martin Rose ◽  
Reza S. Abhari
Keyword(s):  
Flat Plate ◽  
Flow Structure ◽  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Cooling Flow ◽  
Blowing Ratio ◽  
Single Compound

The experimental investigation of film-cooling flow structure provides reliable data for calibrating and validating a 3D feature based computational fluid dynamics (CFD) model being developed synchronously at the ETH Zurich. This paper reports on the flow structure of a film-cooling jet emanating from one hole in a row of holes angled 20 deg to the surface of a flat plate having a 45 deg lateral angle to the freestream flow in a steady flow, flat plate wind tunnel. This facility simulates a film-cooling row typically found on a turbine blade, giving engine representative nondimensionals in terms of geometry and operating conditions. The main flow is heated and the injected coolant is cooled strongly to obtain the requisite density ratio. All three velocity components were measured using a nonintrusive stereoscopic particle image velocimetry (PIV) system. The blowing ratio and density ratio are varied for a single compound angled geometry, and the complex three dimensional flow is investigated with special regard to vortical structure.

Large-Eddy Simulation of Film Cooling Performance Enhancement Using Vortex Generator and Semi-Sphere

2020 ◽  
Author(s):  
Wen Wang ◽  
Jiahuan Cui ◽  
Shaoxing Qu
Keyword(s):  
Film Cooling ◽  
Pressure Loss ◽  
Total Pressure ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Total Pressure Loss ◽  
Cooling Efficiency ◽  
Blowing Ratio ◽  
Large Eddy ◽  
Film Cooling Efficiency

Abstract Film cooling is an essential cooling method to prevent high-pressure turbine blade from melting down due to the high inlet temperature. In order to improve the film cooling efficiency, several flow control methods have been proposed. In this paper, large-eddy simulations are performed to study the effectiveness of a vortex generator (VG) and a semi-sphere installed downstream of the cooling jet. Before the detailed analyses, the numerical framework is validated against the available experimental data. Both the laminar and turbulent approaching boundary layers are considered. The turbulent boundary layer is generated by a numerical plasma actuator. After validation, the influence of VG and semi-sphere on the film cooling efficiency at various blowing ratios are analyzed. It is found that a counter-rotating vortex pair (CVP) is formed downstream and its strength increases with the blowing ratio in the configuration without VG/semi-sphere. When the VG is installed, it produces another vortex pair that rotates in the reverse direction of the CVP, which reduces the CVP strength and increases the lateral diffusion of the coolant. As a result, the film cooling efficiency is greatly improved, especially at a higher blowing ratio. For the case with a semi-sphere, the film cooling efficiency is also improved, especially at low–medium blowing ratios. However, it is not as effective as the VG in terms of enhancing cooling efficiency. In addition, the total pressure loss is calculated to examine the aerodynamic penalty associated with the VG and semi-sphere. It is found that the total pressure loss increased by only 1% due to the VG or semi-sphere, within the range of blowing ratio investigated in the current study. Considering the overall performance and the feasibility of being applied in practice, a semi-sphere installed downstream of the cooling hole is a promising method to improve the cooling efficiency.

Influence of the Groove-Patterned Cooling Tube on the Film Cooling Performance of Gas Turbine

2018 ◽  
Author(s):  
Hyun-Oh Kim ◽  
Hak-Sun Kim ◽  
Youn-Jea Kim
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Turbine Blades ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Cooling Efficiency ◽  
Blowing Ratio ◽  
Aspect Ratios ◽  
Cooling Tube ◽  
Diffuser Angle

The gas turbine performance significantly depends on the temperature of working fluid. In order to improve the efficiency of gas turbine, it is required to increase turbine inlet temperature. However, the working fluid in high temperature conditions causes thermal stress which could damage turbine blades. One of the methods to require turbine blades by controlling the temperature of working fluid is a film-cooling method. In this study, cooling tubes with various aspect ratios of groove length (L/Lt) with groove diameter of d = 1.2 mm were considered to enhance the film cooling efficiency. In addition, effects of blowing ratios (M) and diffuser angles (δ) of the cooling tube were considered. Numerical investigations were conducted using ANSYS ver. 17.1, and film cooling efficiencies of each case were obtained. Especially, the case with groove length aspect ratio of L/Lt = 0.4 at blowing ratio M = 1.4 and diffuser angle δ = 3.5° showed the highest cooling efficiency of 18% among all model cases.

The Effect of Using Ramps with Trench Cylindrical Holes on Film Cooling Effectiveness

2015 ◽  
Vol 3 (2) ◽  
pp. 15-27
Author(s):  
Ahmed A. Imram ◽  
Humam K. Jalghef ◽  
Falah F. Hatem
Keyword(s):  
Numerical Simulation ◽  
Film Cooling ◽  
Air Injection ◽  
Baseline Model ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Hot Air ◽  
Test Study ◽  
Cylindrical Holes

     The effect of introducing ramp with a cylindrical slot hole on the film cooling effectiveness has been investigated experimentally and numerically. The film cooling effectiveness measurements are obtained experimentally. A test study was performed at a single mainstream with Reynolds number 76600 at three different coolant to mainstream blowing ratios 1.5, 2, and 3. Numerical simulation is introduced to primarily estimate the best ramp configurations and to predict the behavior of the transport phenomena in the region linked closely to the interaction between the coolant air injection and the hot air mainstram flow. The results showed that using ramps with trench cylindrical holes would enhanced the overall film cooling effectiveness by 83.33% compared with baseline model at blowing ratio of 1.5, also  the best overall flim cooling effectevness was obtained at blowing ratio of 2 while it is reduced at blowing ratio of 3.

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