scholarly journals Cooling Characteristic of a Wall Jet for Suppressing Crossflow Effect under Conjugate Heat Transfer Condition

Aerospace ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 29
Author(s):  
Qinghua Deng ◽  
Huihui Wang ◽  
Wei He ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Flow Direction ◽  
Leading Edge ◽  
Target Surface ◽  
Suction Side ◽  
Wall Jet ◽  
Internal Cooling ◽  
Transfer Condition ◽  
Jet Cooling

The leading edge is the critical portion for a gas turbine blade and is often insufficiently cooled due to the adverse effect of Crossflow in the cooling chamber. A novel internal cooling structure, wall jet cooling, can suppress Crossflow effect by changing the coolant flow direction. In this paper, the conjugate heat transfer and aerodynamic characteristics of blades with three different internal cooling structures, including impingement with a single row of jets, swirl cooling, and wall jet cooling, are investigated through RANS simulations. The results show that wall jet cooling combines the advantages of impingement cooling and swirl cooling, and has a 19–54% higher laterally-averaged overall cooling effectiveness than the conventional methods at different positions on the suction side. In the blade with wall jet cooling, the spent coolant at the leading edge is extracted away through the downstream channels so that the jet could accurately impinge the target surface without unnecessary mixing, and the high turbulence generated by the separation vortex enhances the heat transfer intensity. The Coriolis force induces the coolant air to adhere to the pressure side’s inner wall surface, preventing the jet from leaving the target surface. The parallel cooling channels eliminate the common Crossflow effect and make the flow distribution of the orifices more uniform. The trailing edge outlet reduces the entire cooling structure’s pressure to a low level, which means less penalty on power output and engine efficiency.

Film Cooling Performances at Different Turbulence Intensities Using Conjugate Heat Transfer Analysis

2017 ◽  
Vol 872 ◽  
pp. 271-278
Author(s):  
Prasert Prapamonthon ◽  
Hua Zhao Xu ◽  
Jian Hua Wang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Large Area ◽  
Cooling Effectiveness ◽  
Flowing Fluid

This study presents a numerical investigation of cooling performances of a modified vane of the film-cooled vane reported by Timko (NASA CR-168289) at different mainstream turbulence intensities (Tus). A 3D conjugate heat transfer (CHT) analysis with SST k-ω turbulence model in FLUENT V.15 is used. Three different mechanisms in CHT analysis, i.e. fluid flow, heat convection between solid surfaces and flowing fluid in an external mainstream and internal cooling passages, and heat conduction within the vane structure, are simultaneously considered. Numerical results are conducted in terms of overall cooling effectiveness at Tu=3.3, 10, and 20%. Comparison between overall cooling effectiveness and film effectiveness under adiabatic assumption is discussed at the three Tus, also. The findings of this research indicate the following phenomena: 1) overall cooling effectiveness decreases with Tu, and this effect on the pressure side (PS) is stronger than that on the suction side (SS) in general. 2) By comparison with adiabatic film effectiveness, the level of overall cooling effectiveness in most regions is higher and more uniform than that of adiabatic film effectiveness for all three Tus. 3) In the leading edge (LE), when Tu increases, near the exits of film holes overall cooling effectiveness deteriorates, but adiabatic film effectiveness improves. Furthermore, a large area with relatively low overall cooling effectiveness is able to move with Tu in the LE region.

Heat Transfer Measurements for Array Jet Impingement with Castellated Wall

2021 ◽  
pp. 1-27
Author(s):  
Taehyun Kim ◽  
Eui Yeop Jung ◽  
Minho Bang ◽  
Changyong Lee ◽  
Hee-Koo Moon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Suction Side ◽  
Wall Jet ◽  
Impingement Cooling ◽  
Baseline Case ◽  
Sublimation Method ◽  
Reduction Effect

Abstract Impingement cooling is one of the powerful cooling methods in high-temperature devices. For gas turbine applications, impingement cooling is commonly applied in the transition piece of a combustor and in the leading edge, suction, and pressure sides of a turbine blade/vane. In the suction side and pressure side, impingement cooling is applied as a form of an array jet. However, due to the small gap between the jet hole and target surface, the wall jet faces a crossflow inside of the gap. This crossflow has an adverse effect on jets and deteriorates the heat transfer performance. Therefore, several studies have been conducted to minimize the crossflow effect. The present study also investigated the effect of crossflow reduction in the gap by having a castellated hole plate. The heat transfer was measured using the naphthalene sublimation method. Heat transfer data are compared among three different cases. One is the baseline case which is simple array jets. Others are the castellated cases with and without rib structures on the target wall. Jet-to-jet spacing(s/d) and jet-to-target spacing(z/d) are selected as geometrical variables. Also, the experiments were conducted for the Reynolds numbers (based on jet hole diameter) of 5,000, 15,000 and 30,000. The baseline case was named as B case, the castellated case without rib as C case and with rib as CR case. Both castellated cases showed the crossflow reduction effect and resulted high and similar Nusselt number values.

Clocking Effects of Inlet Non-Uniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis

2015 ◽  
Author(s):  
Duccio Griffini ◽  
Massimiliano Insinna ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling System ◽  
Hot Spot ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis

A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and high-pressure vanes are then investigated considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first one where hot spot and swirl core are aligned with passage and the second one where they are aligned with the leading edge. Comparisons between metal temperature distributions obtained from conjugate heat transfer simulations are performed evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The leading edge aligned configuration is resulted to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage aligned case. A strong sensitivity of both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

Effects of Jetting Orifice Geometry Parameters and Channel Reynolds Number on Bended Channel Cooling for a Novel Internal Cooling Structure

2019 ◽  
Author(s):  
Wei He ◽  
Qinghua Deng ◽  
Juan He ◽  
Tieyu Gao ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Leading Edge ◽  
Jet Impingement ◽  
Suction Side ◽  
Outer Wall ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Blade Leading Edge

Abstract A novel internal cooling structure has been raised recently to enhance internal cooling effectiveness and reduce coolant requirement without using film cooling. This study mainly focuses on verifying the actual cooling performance of the structure and investigating the heat transfer mechanism of the leading edge part of the structure, named bended channel cooling. The cooling performances of the first stage of GE-E3 turbine with three different blade leading edge cooling structures (impingement cooling, swirl cooling and bended channel cooling) were simulated using the conjugate heat transfer method. Furthermore, the effects of jetting orifice geometry and channel Reynolds number were studied with simplified models to illustrate the flow and heat transfer characteristics of the bended channel cooling. The results show that the novel internal cooling structure has obvious advantages on the blade leading edge and suction side under operating condition. The vortex core structure in the bended channel depends on orifice width, but not channel Reynolds number. With the ratio of orifice width to outer wall thickness smaller than a critical value of 0.5, the coolant flows along the external surface of the channel in the pattern of “inner film cooling”, which is pushed by centrifugal force and minimizes the mixing with spent cooling air. Namely, the greatly organized coolant flow generates higher cooling effectiveness and lower coolant demand. Both the Nusselt number on the channel surfaces and total pressure loss increase significantly when the orifice width falls or channel Reynolds increases, but the wall jet impingement distance appears to be less influential.

Clocking Effects of Inlet Nonuniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Duccio Griffini ◽  
Massimiliano Insinna ◽  
Simone Salvadori ◽  
Francesco Martelli
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Cooling System ◽  
Hot Spot ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Heat Transfer Analysis

A high-pressure vane (HPV) equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side, while the leading edge (LE) is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-averaged Navier–Stokes simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and HPVs are then investigated, considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first in which hot spot and swirl core are aligned with passage; and the second in which they are aligned with the LE. Comparisons between metal temperature distributions obtained from conjugate heat transfer (CHT) simulations are performed, evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The LE aligned configuration is determined to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage-aligned case. A strong sensitivity to both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

Characteristics of Cooling of the Leading Edge With a Row of Dual Impinging Jets

2008 ◽  
Author(s):  
X. C. Li ◽  
P. Corder
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Impinging Jets ◽  
Internal Cooling ◽  
Stagnation Region ◽  
High Heat Transfer ◽  
Two Jets

The leading edge of turbine blades is one of the critical areas that need to be cooled effectively because of the high local heat transfer rate of the main flow. Film cooling with different shaped holes as well as internal cooling by impinging jets has successfully been applied in modern gas turbine applications. This paper numerically studies the cooling of the leading edge with a row of dual impinging jets — two jets close to each other. Heat transfer of the dual jets is compared to that of a single jet (in a row) based on the same flow rate or jet velocity. The effect of the distance between the dual jets and the jet inclination angle is examined to seek the best geometric parameters. In addition, the curvature of the leading edge surface is considered to examine the heat transfer difference between curved and flat walls. Various jet-to-target spacing and Reynolds numbers are also studied. Results show that the dual impinging jets generally produce two high heat transfer regions in the stagnation point, and the peak value is slightly higher than the single row of jets with the same Reynolds number. When the distance between two jets is 3d, the jet flow after bouncing back from the symmetry line affects the heat transfer as a crossflow. The target surface curvature has little effect on the overall heat transfer, but the peak heat transfer coefficient is lower on the curved surface than that on the flat surface. The dual impinging jets present a higher average heat transfer around the stagnation region.

Conjugate Heat Transfer Analysis of a Blade Leading Edge Cooling Configuration Using Double Swirl Chambers

2016 ◽  
Author(s):  
Karsten Kusterer ◽  
Peter Bühler ◽  
Gang Lin ◽  
Takao Sugimoto ◽  
Dieter Bohn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Life Span ◽  
Wall Temperature ◽  
Conjugate Heat Transfer ◽  
Leading Edge ◽  
Internal Cooling ◽  
Impingement Cooling ◽  
Turbine Inlet ◽  
Cooling Technology ◽  
Cooling Air

The efforts to improve the process efficiency of modern gas turbines usually lead to competing objectives for the design of the cooling system as turbine inlet temperatures are continuously increased. Typically, the designer of modern cooling systems is confronted with the requirement to achieve a wall temperature below the maximum allowable wall temperature which is fixed by the material and life span requirements. Simultaneously, a homogenous temperature distribution is desired in order to reduce thermal stresses due to temperature gradients. To maximize cycle efficiency, all this should be achieved by minimizing the necessary cooling air consumption. The Double Swirl Chamber (DSC) cooling technology is a promising configuration to satisfy these design requirements combined. The DSC cooling technology is an advanced kind of internal cooling passage which is created by the merging of two standard single swirl chambers. In the DSC cooling configuration, two anti-rotating large scale swirls are generated which enhance the mixing of the cooling air. This leads subsequently to an increased internal heat exchange. Additionally, the recurring reattachment of the swirl flows at the center of the chamber leads to a linear impingement effect due to local velocity elevations which makes the DSC configuration very suitable for an effective and uniform cooling of thermally high loaded blade leading edges as turbine inlet temperatures are further increased. Thus, the DSC cooling technology has great potential to lengthen the life span of gas turbine blading. In the present work, two DSC configurations are compared numerically to the state-of-the-art leading edge impingement cooling technology with a conjugate heat transfer approach of a simplified blade leading edge geometry. The two investigated DSC are similar, but with the second one being slightly modified in its geometry in order to ease the manufacturing process. With the same numerical setup in terms of applied boundary conditions and under consideration of Reynolds similarity, the DSC configurations show a local temperature reduction of 1.0–1.3% of the turbine inlet temperature in comparison to the impingement cooling case. The total pressure drop in the DSC configurations is in the same range as in the impingement cooling configuration and even slightly decreased by 0.15–0.20%. The heat transfer is 12–16.2% higher in the DSC configurations, which shows the potential for improving the internal cooling performance of a system by the application of the DSC cooling technology in real engine conditions.

Heat Transfer and Pressure Drop Measurements in a Rib Roughened Leading Edge Cooling Channel

2009 ◽  
Author(s):  
Norbert Domaschke ◽  
Jens von Wolfersdorf ◽  
Klaus Semmler
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Cooling System ◽  
Leading Edge ◽  
Suction Side ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Number Range ◽  
Ribbed Channel

In order to enhance convective heat transfer in internal cooling channels, ribs are often used to manipulate the flow field and to benefit from their effect on thermal performance. This paper presents results from an experimental investigation into pressure loss and heat transfer in a smooth and a ribbed leading edge channel of a gas turbine blade internal cooling system. To model the cross section of a realistic leading edge cooling channel both the suction side and the leading edge of the blade profile are designed as curved walls with constant radii. The pressure side as well as the web is approximated by planar walls. For the ribbed channel, 45°-ribs related to the flow direction are placed on the pressure and the suction side with the normalized rib height e/dh = 0.10. Experiments have been carried out for the smooth and the ribbed channel. The flow rate was varied to cover a Reynolds number range from 20,000 to 50,000. The heat transfer has been determined using the transient liquid crystal method. Additional numerical simulations using the SST turbulence model were carried out to analyze the flow field in the channel. The computations were used for further interpretation of the experimental investigations, especially to determine the temperature field and velocity field and therefore the bulk temperature within the test section.

Thermal Analysis of a Turbine Blade: Effect of Film Cooling and Internal Convective Cooling

2015 ◽  
Author(s):  
S. Sarkar ◽  
P. Gupta
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Leading Edge ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Suction Surface ◽  
Transfer Condition ◽  
Convective Cooling ◽  
Cooling Passage

Advanced gas turbines are designed to operate at increasingly higher inlet temperature that poses a greater challenge to the designer for more effective blade cooling strategies. In this paper, a generic high-pressure turbine (HPT) blade of a gas turbine, which is cooled by film cooling in conjunction with internal convective cooling, has been analysed by solving Navier-Stokes and energy equations. The intricate internal cooling passages and a series of holes on the suction surface are considered for the simulations. Large numbers of cell in different zones are used to truly replace the blade with cooling holes and the internal cooling passage. The CFD analysis with conjugate heat transfer condition is accomplished by Fluent, version 6.3. A detailed discussion has been made regarding the aerodynamics and heat transfer. In brief, the suction surface is well protected by film cooling, whereas, the pressure surface demands some additional protection for a longer life. The leading edge is under the metallurgical limit because of internal cooling for the present configuration.

Experimental and Numerical Study of Array Jet Impingement Cooling on a Leading-Edge Curved Surface

2020 ◽  
Author(s):  
Jorge Torres ◽  
Husam Zawati ◽  
Erik Fernandez ◽  
Jayanta Kapat ◽  
Jose Rodriguez
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Numerical Study ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Suction Side ◽  
Navier Stokes ◽  
Mean Flow ◽  
Side Pressure

Abstract Aerothermal performance of an asymmetrical-profile, leading-edge jet impingement array is studied using numerical and experimental techniques. This array consists of a single row of 9 jets impinging on a leading edge of diameter ratio D/d = 2, and a distinct suction side/pressure side akin to that of an actual turbine blade. Two different jet-to-target heights are tested, while the jet spacing of 4 jet diameters is kept constant. A range of jet-averaged Reynolds numbers between 20k – 80k are tested. The mean flow field of the mid-jet plane is quantified experimentally, through a non-intrusive experimental method of Particle Image Velocimetry (PIV), while area-averaged heat transfer is measured by the constant temperature copper block technique. The target surface is divided into several copper blocks to investigate the area-averaged heat transfer at each jet. The numerical portion of the presented work serves to investigate the fidelity of the Reynolds Averaged Navier-Stokes (RANS) k-ω turbulence model and how well it can predict the flow field within the geometrical domain of the leading edge.

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