Effect of Temperature Ratio on Jet Impingement Heat Transfer in Active Clearance Control Systems

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Jacopo D’Errico ◽  
Lorenzo Tarchi
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Effect Of Temperature ◽  
Internal Cooling ◽  
Temperature Ratio ◽  
Present Contribution ◽  
Wide Range ◽  
Depth Analysis ◽  
The Impact ◽  
Clearance Control

Impinging jet arrays are typically used to cool several gas turbine parts. Some examples of such applications can be found in the internal cooling of high-pressure turbine airfoils or in the turbine blade tip clearances control of aero-engines. The effect of the wall-to-jets temperature ratio (TR) on heat transfer is generally neglected by the correlations available in the open literature. In the present contribution, the impact of the temperature ratio on the heat transfer for a real engine active clearance control system is analyzed by means of validated computational fluid dynamics (CFD) computations. At different jets Reynolds number and considering several impingement array arrangements, a wide range of target wall-to-jets temperature ratio is accounted for. Computational results prove that both local and averaged Nusselt numbers reduce with increasing. An in-depth analysis of the numerical data shows that the last mentioned evidence is motivated by both the heat transfer incurring between the spent coolant flow and the fresh jets and the variation of gas properties with temperature through the boundary layer. A scaling procedure, based on the TR power law, was proposed to estimate the Nusselt number at different wall temperature levels necessary to correct available open-literature correlations, typically developed with small temperature differences, for real engine applications.

Effect of Temperature Ratio on Jet Impingement Heat Transfer in Active Clearance Control Systems

2018 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Jacopo D’Errico ◽  
Lorenzo Tarchi
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Effect Of Temperature ◽  
Internal Cooling ◽  
Temperature Ratio ◽  
Present Contribution ◽  
Wide Range ◽  
Depth Analysis ◽  
The Impact ◽  
Clearance Control

Impinging jet arrays are typically used to cool several gas turbine parts. Some examples of such applications can be found in the internal cooling of high pressure turbine airfoils or in the turbine blade tip clearances control of aero-engines. The effect of wall-to-jets temperature ratio on heat transfer is generally neglected by the correlations available in the open literature. In present contribution, the impact of the temperature ratio on the heat transfer for a real engine Active Clearance Control system, is analyzed by means of validated CFD computations. At different jets Reynolds number and considering several impingement array arrangements, a wide range of target wall-to-jets temperature ratio (TR) is accounted for. Computational results prove that both local and averaged Nusselt numbers reduce with increasing temperature ratios. An in-depth analysis of the numerical data show that the last mentioned evidence is motivated by both the heat transfer incurring between the spent coolant flow and the fresh jets and the variation of gas properties with temperature through the boundary layer. A scaling procedure, based on TR power law, was proposed to estimate the Nusselt number at different wall temperature levels necessary to correct available open-literature correlations, typically developed with small temperature differences, for real engine applications.

Heat Transfer Augmentation Due to Coolant Extraction on the Cold Side of Active Clearance Control Manifolds

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Antonio Andreini ◽  
Bruno Facchini ◽  
Lorenzo Mazzei
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Wide Range ◽  
Depth Analysis ◽  
Clearance Control ◽  
The Heat Transfer Coefficient

Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In the open literature, several contributions focus on the impingement jets formation and deal with the heat transfer phenomena that take place on the impingement target surface. However, deficiencies of general studies emerge when the internal convective cooling of the impinging system feeding channels is concerned. In this work, an aerothermal analysis of jet arrays for active clearance control (ACC) was performed; the aim was the definition of a correlation for the internal (i.e., within the feeding channel) convective heat transfer coefficient augmentation due to the coolant extraction operated by the bleeding holes. The data were taken from a set of computational fluid-dynamics (CFD) Reynolds-averaged Navier–Stokes (RANS) simulations, in which the behavior of the cooling system was investigated over a wide range of fluid-dynamics conditions. More in detail, several different holes arrangements were investigated with the aim of evaluating the influence of the hole spacing on the heat transfer coefficient distribution. Tests were conducted by varying the feeding channel Reynolds number in a wide range of real engine operative conditions. An in depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the local suction ratio (SR) of hole and feeding pipe, local Reynolds number, and manifold porosity: the dependence of the heat transfer coefficient enhancement factor (EF) from these parameter is roughly exponential.

Heat Transfer Augmentation due to Coolant Extraction on the Cold Side of Active Clearance Control Manifolds

2015 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Antonio Andreini ◽  
Bruno Facchini ◽  
Lorenzo Mazzei
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Data Set ◽  
Wide Range ◽  
Depth Analysis ◽  
Clearance Control ◽  
The Heat Transfer Coefficient

Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In the open literature, several contributions focus on the impingement jets formation and deals with the heat transfer phenomena that take place on the impingement target surface. However, deficiencies of general studies emerges when the internal convective cooling of the impinging system feeding channels is concerned. In this work an aero-thermal analysis of jet arrays for active clearance control was performed; the aim was the definition of a correlation for the internal (i.e. within the feeding channel) convective heat transfer coefficient augmentation due to the coolant extraction operated by the bleeding holes. The data were taken from a set of CFD RANS simulations, in which the behaviour of the cooling system was investigated over a wide range of fluid-dynamics conditions. More in detail, several different holes arrangements were investigated with the aim of evaluating the influence of the hole spacing on the heat transfer coefficient distribution. Tests were conducted by varying the feeding channel Reynolds number in a wide range of real engine operative conditions. An in depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the local suction ratio of hole and feeding pipe, local Reynolds number and manifold porosity: the dependence of the heat transfer coefficient enhancement factor from these parameter is roughly exponential.

Heat Transfer Implications of Acoustic Resonances in HP Turbine Blade Internal Cooling Channels

2015 ◽  
Author(s):  
C. Selcan ◽  
B. Cukurel ◽  
J. Shashank
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Cooling System ◽  
Resonance Condition ◽  
Order Approximation ◽  
Acoustic Resonance ◽  
Mode Shapes ◽  
Internal Cooling ◽  
The Impact ◽  
Standing Sound

In an attempt to investigate the acoustic resonance effect of serpentine passages on internal convection heat transfer, the present work examines a typical high pressure turbine blade internal cooling system, based on the geometry of the NASA E3 engine. In order to identify the associated dominant acoustic characteristics, a numerical FEM simulation (two-step frequency domain analysis) is conducted to solve the Helmholtz equation with and without source terms. Mode shapes of the relevant identified eigenfrequencies (in the 0–20kHz range) are studied with respect to induced standing sound wave patterns and the local node/antinode distributions. It is observed that despite the complexity of engine geometries, as a first order approximation, the predominant resonance behavior can be modeled by a same-ended straight duct. Therefore, capturing the physics observed in a generic geometry, the heat transfer ramifications are experimentally investigated in a scaled wind tunnel facility at a representative resonance condition. Focusing on the straight cooling channel’s longitudinal eigenmode in the presence of an isolated rib element, the impact of standing sound waves on convective heat transfer and aerodynamic losses are demonstrated by liquid crystal thermometry, local static pressure and sound level measurements. The findings indicate a pronounced heat transfer influence in the rib wake separation region, without a higher pressure drop penalty. This highlights the potential of modulating the aero-thermal performance of the system via acoustic resonance mode excitations.

Heat Transfer Analysis of Jet Impingement Cooling on a Simulated Ceramic Matrix Composite Surface

2017 ◽  
Author(s):  
Karthik Krishna ◽  
Mark Ricklick
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Matrix Composite ◽  
Ceramic Matrix Composite ◽  
Jet Impingement ◽  
Ceramic Matrix ◽  
Heat Transfer Analysis ◽  
Test Surface ◽  
Composite Surface ◽  
The Impact

Ceramic Matrix Composite is a woven material characterized by a significant level of surface waviness of 35–60μm and surface roughness of 5–6μm. To be implemented in a future gas turbine engine they will be cooled traditionally to increase power and efficiency. To analyze the CMC surface effects on heat transfer rate, an impinging circular jet on a simulated CMC surface is studied experimentally and the CMC surface is represented by a high resolution CNC machined surface. The test parameters are jet to plate distance of 7 jet diameters, oblique impingement angles of 45° and 90° and Reynolds numbers of 11,000 to 35,000. The test surface is broken down into constant temperature segments, and individual segment Nusselt number is determined and plotted for the various impingement cases studied. Area-Averaged results show negligible changes in average Nusselt number as compared to the hydrodynamically smooth surface. The impact of the CMC surface feature is negligible compared to the uncertainty in heat transfer coefficient, and therefore traditional design tools can be utilized.

Rotating Heat Transfer Measurements on a Multi-Pass Internal Cooling Channel: II — Experimental Tests

2016 ◽  
Author(s):  
Fabio Pagnacco ◽  
Luca Furlani ◽  
Alessandro Armellini ◽  
Luca Casarsa ◽  
Anthony Davis
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Rotation Axis ◽  
Internal Cooling ◽  
Test Model ◽  
Transfer Coefficients ◽  
Present Contribution ◽  
The Real ◽  
The Third ◽  
Ribbed Channel

The present contribution is focused on heat transfer measurements on internal cooling channels of a high pressure gas turbine blade in static and rotating conditions. A novel rig designed for the specific purpose was used to assess the heat transfer coefficients on a full internal cooling scheme of an idealized blade. The channel has a multi-pass design. Coolant enters at the blade hub in the leading edge region and move radially outwards inside a two-sided ribbed channel. The second passage is again a two-sided ribbed channel with a trapezoidal cross section of high aspect ratio, while inside the third leg low aspect-ratio cylindrical pin fins are arranged in a staggered configuration to promote flow turbulence. Inside the third passage, the coolant is progressively discharged at the blade trailing edge and finally at the blade tip. The test model differs with respect to the real design only because there is no curvature due to the blade camber. Conversely, the correct stagger angle of the real blade with respect to the rotation axis is preserved. Experiments were performed for static and rotating conditions with engine similar conditions of Re=21000 and Ro=0.074, both defined at the channel inlet. Transient liquid crystal technique was used for the measurement of the heat transfer coefficient (HTC) on both pressure and suction sides internal surfaces of the channel. From the spatially resolved HTC maps available, it is possible to characterize the thermal performances of the whole passage and to highlight the effect of rotation.

Effect of Temperature Ratio on Jet Array Impingement Heat Transfer

2007 ◽  
Author(s):  
Matt Goodro ◽  
Jongmyung Park ◽  
Phil Ligrani ◽  
Mike Fox ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Turbulent Transport ◽  
Velocity Ratio ◽  
Impinging Jets ◽  
Effect Of Temperature ◽  
Temperature Ratio ◽  
Target Plate ◽  
Plate Temperature ◽  
Fluid Properties ◽  
Effects Of Temperature

Considered are the effects of temperature ratio on the heat transfer from an array of jets impinging on a flat plate. At constant Reynolds number of 18000, and constant Mach number of 0.2, different ratios of target plate temperature to jet temperature are employed. The spacing between holes in the streamwise direction X is 8D, and the spanwise spacing between holes in a given streamwise row Y is also 8D. The target plate is located 3D away from the impingement hole exits. Experimental results show that local, line-averaged, and spatially-averaged Nusselt numbers decrease as the Tw/Tj temperature ratio increases. This is believed to be due to the effects of temperature-dependent fluid properties, as they affect local and global turbulent transport in the flow field created by the array of impinging jets. The effect of temperature ratio on crossflow-to-jet mass velocity ratio and discharge coefficients are also examined.

Overall Effectiveness of a Blade Endwall With Jet Impingement and Film Cooling

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Amy Mensch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Jet Impingement ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Convective Cooling ◽  
Impingement Cooling ◽  
Internal Impingement ◽  
The Impact ◽  
Overall Effectiveness

Ever-increasing thermal loads on gas turbine components require improved cooling schemes to extend component life. Engine designers often rely on multiple thermal protection techniques, including internal cooling and external film cooling. A conjugate heat transfer model for the endwall of a seven-blade cascade was developed to examine the impact of both convective cooling and solid conduction through the endwall. Appropriate parameters were scaled to ensure engine-relevant temperatures were reported. External film cooling and internal jet impingement cooling were tested separately and together for their combined effects. Experiments with only film cooling showed high effectiveness around film-cooling holes due to convective cooling within the holes. Internal impingement cooling provided more uniform effectiveness than film cooling, and impingement effectiveness improved markedly with increasing blowing ratio. Combining internal impingement and external film cooling produced overall effectiveness values as high as 0.4. A simplified, one-dimensional heat transfer analysis was used to develop a prediction of the combined overall effectiveness using results from impingement only and film cooling only cases. The analysis resulted in relatively good predictions, which served to reinforce the consistency of the experimental data.

Impact of Sweeping Jet on Area-Averaged Impingement Heat Transfer

2019 ◽  
Author(s):  
Andrea Osorio ◽  
Justin Hodges ◽  
Husam Zawati ◽  
Erik J. Fernandez ◽  
Jayanta S. Kapat ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heated Surface ◽  
Thermal Inertia ◽  
Jet Impingement ◽  
Target Surface ◽  
Bottom Surface ◽  
Fluidic Oscillator ◽  
Surface Temperatures ◽  
Sweeping Motion ◽  
The Impact

Abstract A series of sweeping jet-impingement experiments are conducted over a circular heated surface, with a main objective of understanding the impact of the unique flow field on the resulting heat transfer. The sweeping motion of the fluidic oscillator is influenced by the sweeping frequency and sweeping angle where each is directly dependent on the geometric design (i.e. internal feedback loops, mixing chamber, etc.). The target surface consists of a heated copper disk, where heater power is supplied to the bottom surface of the disk and adjusted until a differential of 30°C is obtained between the jet and target surface temperatures. An energy balance over the target surface temperatures provides a means for calculating area-averaged heat transfer rate, hence Nusselt number. An increase in the sweeping jet’s thermal inertia initiates an augmentation in heat transfer due to sweeping motion of the jet across the target surface. PIV data was acquired for two jet configurations, confined and unconfined, so that the recirculation behavior can be determined. The fluidic oscillator is found to improve only at a low z/d. At large z/d (greater than 4 in this study), the fluidic oscillator adversely affects the heat transfer.

Heat Transfer in Internal Cooling Channels of Gas Turbine Blades: Buoyancy and Density Ratio Effects

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Mandana S. Saravani ◽  
Nicholas J. DiPasquale ◽  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Rotational Speed ◽  
Turbine Blades ◽  
Density Ratio ◽  
Internal Cooling ◽  
Buoyancy Effect ◽  
First Case ◽  
Buoyancy Forces ◽  
The Impact

The present work investigates the effects of buoyancy and wall heating condition on the thermal performance of a rotating two-pass square channel with smooth walls. The U-bend channel has a square cross section with a hydraulic diameter of 5.08 cm (2 in.). The lengths of the first and second passes are 514 mm and 460 mm, respectively. The turbulent flow entered the channel with Reynolds numbers of up to 34,000. The rotational speed varied from 0 to 600 rpm with rotational numbers up to 0.75. For this study, two approaches were considered for tracking the buoyancy effect on heat transfer. In the first case, the density ratio was set constant, and the rotational speed was varied. In the second case, the density ratio was changed in the stationary case, and the effect of density ratio was discussed. The range of buoyancy number along the channel is 0–6. The objective was to investigate the impact of buoyancy forces on a broader range of rotation number (0–0.75) and buoyancy number scales (0–6), and their combined effects on heat transfer coefficient for a channel with an aspect ratio of 1 : 1. Results showed that increasing the density ratio increased the heat transfer ratio in both stationary and rotational cases. Furthermore, in rotational cases, buoyancy force effects were very significant. Increasing the rotation number induced more buoyancy forces, which led to an enhancement in heat transfer. The buoyancy effect was more visible in the turning region than any other region.

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