Effect of blowing ratio on Film-Cooling effectiveness of Ginkgo Shaped Holes: A numerical approach

Modern gas turbine engines operate at significantly high temperatures to improve thermal efficiency and power output to a greater extent. The enhancement in rotor inlet temperature (RIT) increases the heat transfer rate to the turbine blades which requires sophisticated cooling schemes to maintain the blade temperature in acceptable levels. Therefore, the present work refers to the numerical investigation of film cooling technique applied in gas turbines. The cooling performance of two different shaped holes namely Ginkgo Forward (GF) and Ginkgo Reverse (GR)) were investigated in terms of centerline and local lateral effectiveness and comprehensive comparison was made with the cooling performance of cylindrical (CY) hole. The investigations were performed at two density ratios (DR=1.6, 2.0) and three different blowing ratios (BR=1.0, 1.5 and 2.0). At all the operating conditions, the results demonstrated significant augmentation in centerline and lateral effectiveness when GR shaped hole was employed followed by the GF and CY cooling holes. For shaped holes, the low velocity gradient through the film alleviated jet lift off and turbulence intensity resulting in decreased entrainment of hot gas to bottom surface. To conclude, the lateral coverage due to the shaped cooling holes significantly enhanced the thermal protection and overall cooling performance.

Volume 2: Heat Transfer Enhancement for Practical Applications; Fire and Combustion; Multi-Phase Systems; Heat Transfer in Electronic Equipment; Low Temperature Heat Transfer; Computational Heat Transfer ◽

Numerical Simulation on Gas Turbine Film Cooling of Curved Surface With Backward Injection

10.1115/ht2012-58469 ◽

2012 ◽

Author(s):

Shashank Shetty ◽

Xianchang Li ◽

Ganesh Subbuswamy

Keyword(s):

Numerical Simulation ◽

Gas Turbine ◽

Film Cooling ◽

Gas Turbines ◽

Turbine Blades ◽

Operating Conditions ◽

Strong Mixing ◽

Inlet Temperature ◽

Aerodynamic Loss

Due to the unique role of gas turbine engines in power generation and aircraft propulsion, significant effort has been made to improve the gas turbine performance. As a result, the turbine inlet temperature is usually elevated to be higher than the metal melting point. Therefore, effective cooling of gas turbines is a critical task for engines’ efficiency as well as safety and lifetime. Film cooling has been used to cool the turbine blades for many years. The main issues related to film cooling are its poor coverage, aerodynamic loss, and increase of heat transfer coefficient due to strong mixing. To overcome these problems, film cooling with backward injection has been found to produce a more uniform cooling coverage under low pressure and temperature conditions and with simple cylindrical holes. Therefore, the focus of this paper is on the performance of film cooling with backward injection at gas turbine operating conditions. By applying numerical simulation, it is observed that along the centerline on both concave and convex surfaces, the film cooling effectiveness decreases with backward injection. However, cooling along the span is improved, resulting in more uniform cooling.

Parametric Study on Anti-Vortex Film Cooling Hole Arrangements

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.660.664 ◽

2014 ◽

Vol 660 ◽

pp. 664-668

Author(s):

Kamil Abdullah ◽

Hazim Fadli Aminnuddin ◽

Akmal Nizam Mohammed

Keyword(s):

Film Cooling ◽

Thermal Protection ◽

Turbine Blades ◽

Vortex Pair ◽

Navier Stokes ◽

Cooling Effectiveness ◽

Cooling Hole ◽

Lateral Film ◽

Film cooling has been extensively used to provide thermal protection for the external surface of the gas turbine blades. Numerous number of film cooling holes designs and arrangements have been introduced. The main motivation of these designs and arrangements are to reduce the lift-off effect cause by the counter rotating vortices (CRVP) produce by cylindrical cooling hole. One of the efforts is the introduction of newly found anti-vortex film cooling design. The present study focuses on anti-vortex holes arrangement consists of a main hole and pair of smaller holes. All three holes share a common inlet with the outlet of the smaller holes varies base on it relative position towards the main hole. Three anti-vortex holes arrangements have been considered; downstream anti-vortex hole arrangement (DAV), lateral anti-vortex hole arrangement (LAV), and upstream anti-vortex hole arrangement (UAV). In addition, a single hole (SH) film cooling has also been considered as the baseline. The investigation make used of ANSYS CFX software ver. 14. The investigations are made through Reynolds Average Navier Stokes analyses with the application of shear k-ε turbulence model. The results show that the anti-vortex designs produce significant improvement in term of film cooling effectiveness and distribution. The LAV arrangement shows the best film cooling effectiveness distribution among all considered cases and is consistent for all blowing ratios (BR). The results also unveil the formation of new vortex pair on both side of the primary hole CRVP. Interaction between the new vortices and the main CRVP structure reduce the lift off explaining the increased lateral film effectiveness.

A Three-Regime Based Method for Correlating Film Cooling Effectiveness for Cylindrical and Shaped Holes

Volume 5B: Heat Transfer ◽

10.1115/gt2015-42180 ◽

2015 ◽

Author(s):

Lieke Wang ◽

Mats Kinell ◽

Hossein N. Najafabadi ◽

Matts Karlsson

Keyword(s):

Experimental Data ◽

Film Cooling ◽

Gas Turbines ◽

Density Ratio ◽

Transition Regime ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Blowing Ratio ◽

To cope with high temperature of the gas from combustor, cooling is often used in the hot gas components in gas turbines. Film cooling is one of the effective methods used in this application. Both cylindrical and fan-shaped holes are used in film cooling. There have been a number of correlations published for both cylindrical and fan-shaped holes regarding film cooling effectiveness. Unfortunately there are no definitive correlations for either cylindrical or fan-shaped holes. This is due to the nature of the complexity of film cooling where many factors influence its performance, e.g., blowing ratio, density ratio, surface angle, downstream distance, expansion angle, hole length, turbulence level, etc. A test rig using infrared camera was built to test the film cooling performance for a scaled geometry from a real nozzle guide vane. Both cylindrical and fan-shaped holes were tested. To correlate the experimental data, a three-regime based method was developed for predicting the film cooling effectiveness. Based on the blowing ratio, the proposed method divides the film cooling performance in three regimes: fully attached (or no jet lift-off), fully jet lift-off, and the transition regime in between. Two separate correlations are developed for fully attached and full jet lift-off regimes, respectively. The method of interpolation from these two regimes is used to predict the film cooling effectiveness for the transition regime, based on the blowing ratio. It has been found this method can give a good correlation to match the experimental data, for both cylindrical and fan-shaped holes. A comparison with literature was also carried out, and it showed a good agreement.

Effect of spherical blockage configurations on film cooling

Thermal Science ◽

10.2298/tsci171229257w ◽

2018 ◽

Vol 22 (5) ◽

pp. 1933-1942 ◽

Cited By ~ 1

Author(s):

Jin Wang ◽

Ke Tian ◽

Kai Zhang ◽

Jakov Baleta ◽

Bengt Sunden

Keyword(s):

Film Cooling ◽

Gas Turbines ◽

Rectangular Channel ◽

Turbine Blades ◽

Dust Particles ◽

Inlet Temperature ◽

Blowing Ratio ◽

Lateral Film ◽

Comparison Of The Results

With increasing inlet temperature of gas turbines, turbine blades need to be effectively protected by using cooling technologies. However, the deposition from the fuel impurities and dust particles in the air is often found inside film holes, which results in partial hole blockage. In this paper, the deposition geometry is simplified as a rectangular channel, and the effect of three blockage ratios is investigated by using the computational fluid dynamics. In addition, water droplets are also released from the coolant inlet to provide a comparison of the results with and without mist injection. It is found that the lateral film cooling effectiveness is reduced with increasing blockage ratio. For all the cases with the blowing ratio 0.6, 1% mist injection provides an improvement of the cooling performance by approximately 10%.

New Designs of Novel Holes Based on Cylindrical Configurations for Improving Film Cooling Effectiveness

Volume 5A: Heat Transfer ◽

10.1115/gt2018-76380 ◽

2018 ◽

Author(s):

Rui Zhu ◽

Gongnan Xie ◽

Terrence W. Simon

Keyword(s):

Film Cooling ◽

Gas Turbines ◽

Thermal Protection ◽

Cylindrical Hole ◽

Two Stage ◽

Cooling Effectiveness ◽

Vortex Pairs ◽

Shaped Hole ◽

In modern gas turbines, film cooling technology is the most common and efficient way to provide thermal protection for hot parts. To improve film cooling effectiveness, different kinds of shaped holes have been designed, but most of them are complicated and difficult to machine. In this study, four cases of novel film cooling hole design, all based on cylindrical holes, are numerically studied. One is a single, two-stage cylindrical hole, whose downstreamhalf-length has a diameter D while the upstreamhalf-length has a diameter D/2. A second has a cylindrical primary hole with two smaller secondary holes located symmetrically about the centerline of the primary hole and downstream of the primary hole. The three holes of this second design are then combined to make a single shaped hole, constituting a third case, called the tri-circular shaped hole. The entry part of the third case is replaced by a cylindrical hole with a diameter of half the primary hole diameter, making a fourth case called the two-stage tri-circular shaped hole. Film cooling effectiveness and surrounding thermal and flow fields are numerically investigated for all four cases using various blowing ratios. It is shown from the simulation that the two-stage cylindrical hole cannot improve film cooling effectiveness. The primary hole with two secondary holes can enhance film cooling performance by creating anti-kidney vortex pairs, which will weaken jet lift-off, caused by the kidney vortex pairs, from the primary hole. The tri-circular shaped hole will provide better film cooling effectiveness near the hole area, and is not sensitive to blowing ratio. The two-stage structure for tri-circular shaped hole provides better film coverage because it changes the flow structure inside the channel and decreases jet penetration.

Simulation of Backward Film Cooling at Gas Turbine Operating Conditions With and Without Mist Injection

Volume 10: Heat and Mass Transport Processes, Parts A and B ◽

10.1115/imece2011-65246 ◽

2011 ◽

Author(s):

Ganesh Subbuswamy ◽

Xianchang Li

Keyword(s):

Gas Turbine ◽

Film Cooling ◽

Gas Turbines ◽

Turbine Blades ◽

Operating Conditions ◽

Aerodynamic Loss ◽

Blowing Ratio ◽

Flow Mixing ◽

Cylindrical Holes

The cooling of gas turbines is critical for engines’ efficiency as well as safety and lifetime. Film cooling has been used to cool the turbine blades for many years. The main issues related to film cooling are its poor coverage, aerodynamic loss, and increase of heat transfer coefficient due to strong flow mixing. To overcome these problems, film cooling with backward injection has been found to produce a more uniform cooling coverage under low pressure and temperature conditions and with simple cylindrical holes. The performance of film cooling with backward injection at gas turbine operating conditions is studied with numerical simulation in this paper. Effects of the blowing ratios and angles are examined. It is seen that the cooling coverage is generally much more uniform by using backward injection at gas turbine operating conditions, and in some cases the film cooling effectiveness can be almost doubled when compared to forward injection. The backward injection also shows its advantage when the blowing angle and blowing ratio change. However, mist (droplets) injection does not affect the cooling performance of the backward jet at the conditions under study. The best case of film cooling in this study is the fan-shaped hole with backward injection.

Film Cooling From Novel Sister Shaped Single-Holes

Volume 5B: Heat Transfer ◽

10.1115/gt2014-25971 ◽

2014 ◽

Cited By ~ 5

Author(s):

Siavash Khajehhasani ◽

Bassam Jubran

Keyword(s):

Film Cooling ◽

Three Dimensional ◽

Lateral Spreading ◽

Navier Stokes ◽

The Novel ◽

Cooling Performance ◽

Blowing Ratio ◽

Shaped Hole ◽

A numerical investigation of the film cooling performance from novel sister shaped single-holes (SSSH) is presented in this paper and the obtained results are compared with a single cylindrical hole, a forward diffused shaped hole, as well as discrete sister holes. Three types of the novel sister shaped single-hole schemes namely downstream, upstream and up/downstream SSSH, are designed based on merging the discrete sister holes to the primary hole in order to reduce the jet lift-off effect and increase the lateral spreading of the coolant on the blade surface as well as a reduction in the amount of coolant in comparison with discrete sister holes. The simulations are performed using three-dimensional Reynolds-Averaged Navier Stokes analysis with the realizable k–ε model combined with the standard wall function. The upstream SSSH demonstrates similar film cooling performance to that of the forward diffused shaped hole for the low blowing ratio of 0.5. While it performs more efficiently at M = 1, where the centerline and laterally averaged effectiveness results improved by 70% and 17%, respectively. On the other hand, the downstream and up/downstream SSSH schemes show a considerable improvement in film cooling performance in terms of obtaining higher film cooling effectiveness and less jet lift-off effect as compared with the single cylindrical and forward diffused shaped holes for both blowing ratios of M = 0.5 and 1. For example, the laterally averaged effectiveness for the downstream SSSH configuration shows an improvement of approximately 57% and 110% on average as compared to the forward diffused shaped hole for blowing ratios of 0.5 and 1, respectively.

Numerical Investigation of the Cooling Performance on the Endwall With and Without Fillet

Volume 5A: Heat Transfer ◽

10.1115/gt2018-76316 ◽

2018 ◽

Author(s):

Qingzong Xu ◽

Qiang Du ◽

Pei Wang ◽

Jun Liu ◽

Guang Liu

Keyword(s):

Secondary Flow ◽

Turbulence Model ◽

Film Cooling ◽

Computational Method ◽

Inlet Temperature ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Numerical Predictions ◽

Turbine Vane

High inlet temperature of turbine vane increases the demand of high film cooling effectiveness. Vane endwall region was extensively cooled due to the high and flat exit temperature distribution of combustor. Leakage flow from the combustor-turbine gap was used to cool the endwall region except for preventing hot gas ingestion. Numerical predictions were conducted to investigate the flow structure and adiabatic film cooling effectiveness of endwall region in a linear cascade with vane-endwall junction fillet. The simulations were completed by solving the three-dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with shear stress transport(SST) k-ω turbulence model, meanwhile, the computational method and turbulence model were validated by comparing computational result with the experiment. Three types of linear fillet with the length-to-height ratio of 0.5, 1 and 2, named fillet A, fillet B and fillet C respectively, were studied. In addition, circular fillet with radius of 2mm was compared with linear fillet B. The interrupted slot, produced by changing the way of junction of combustor and turbine vane endwall, is introduced at X/Cax = −0.2 upstream of the vane leading edge. Results showed that fillet can significantly affect the cooling performance on the endwall due to suppressing the strength of the secondary flow. Fillet C presented the best cooling performance comparing to fillet A and fillet B because a portion of the coolant which climbs to the fillet was barely affected by secondary flow. Results also showed the effect of fillet on the total pressure loss. The result indicated that only fillet A slightly decreases endwall loss.

Numerical Approach at Flat Plate for Predicting the Film Cooling Effectiveness Part A: Effect Blowing Ratio

Diffusion Foundations ◽

10.4028/www.scientific.net/df.16.30 ◽

2018 ◽

Vol 16 ◽

pp. 30-44 ◽

Cited By ~ 1

Author(s):

Farouk Kebir ◽

Azzeddine Khorsi

Keyword(s):

Heat Transfer ◽

Flat Plate ◽

Film Cooling ◽

Thermal Stresses ◽

Free Stream ◽

Turbine Blades ◽

Cooling Performance ◽

Free Stream Turbulence ◽

Blowing Ratio

Film cooling is vital for gas turbine blades to protect them from thermal stresses and high temperatures due to the hot gas flow in the blade surface. Film cooling is applied to almost all external surfaces associated with aerodynamic profiles that are exposed to hot combustion gases such as main bodies, end-walls, blade tips and leading edges. In a review of the literature, it was found that there are strong effects of free-stream turbulence, surface curvature and hole shape on film cooling performance also blowing ratio. The performance of the film cooling is difficult to predict due to the inherent complex flow fields along the surfaces of the airfoil components in the turbine engines. From all what we introducing the film cooling is reviewed through a discussion of the analyses methodologies, a physical description, and the various influences on film-cooling performance. Initially Computational analysis was done on a flat plate with hole inclined at 55° to the surface plate. This study focuses on the efficient computation of film cooling flows with three blowing ratio. The numerical results show the effectiveness cooling and heat transfer behavior with increasing injection blowing ratio M (0.5, 1, and 1.5). The influence of increased blade film cooling can be assessed via the values of Nusselt number in terms of reduced heat transfer to the blade. Predictions of film effectiveness are compared with experimental results for a circular jet at blowing ratios ranging from 0.5, 1.0 and 1.5. The present results are obtained at a free stream turbulence of 10%, which are the typical conditions upstream of the effectiveness is generally lower for a large stream-wise angle of 55°.

Effect of Internal Coolant Crossflow on the Effectiveness of Shaped Film-Cooling Holes

Journal of Turbomachinery ◽

10.1115/1.1580523 ◽

2003 ◽

Vol 125 (3) ◽

pp. 547-554 ◽

Cited By ~ 38

Author(s):

Michael Gritsch ◽

Achmed Schulz ◽

Sigmar Wittig

Keyword(s):

Film Cooling ◽

Gas Flow ◽

Flow Direction ◽

Turbine Blades ◽

Density Ratio ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Hot Gas ◽

Wide Range

Film-cooling was the subject of numerous studies during the past decades. However, the effect of flow conditions on the entry side of the film-cooling hole on film-cooling performance has surprisingly not received much attention. A stagnant plenum which is widely used in experimental and numerical studies to feed the holes is not necessarily a right means to re-present real engine conditions. For this reason, the present paper reports on an experimental study investigating the effect of a coolant crossflow feeding the holes that is oriented perpendicular to the hot gas flow direction to model a flow situation that is, for instance, of common use in modern turbine blades’ cooling schemes. A comprehensive set of experiments was performed to evaluate the effect of perpendicular coolant supply direction on film-cooling effectiveness over a wide range of blowing ratios (M=0.5…2.0) and coolant crossflow Mach numbers Mac=0…0.6. The coolant-to-hot gas density ratio, however, was kept constant at 1.85 which can be assumed to be representative for typical gas turbine applications. Three different hole geometries, including a cylindrical hole as well as two holes with expanded exits, were considered. Particularly, two-dimensional distributions of local film-cooling effectiveness acquired by means of an infrared camera system were used to give detailed insight into the governing flow phenomena. The results of the present investigation show that there is a profound effect of how the coolant is supplied to the hole on the film-cooling performance in the near hole region. Therefore, crossflow at the hole entry side has be taken into account when modeling film-cooling schemes of turbine bladings.