Influence of Channel Geometry and Flow Variables on Cyclone Cooling of Turbine Blades

2015 ◽  
Author(s):  
Martin Bruschewski ◽  
Christian Scherhag ◽  
Heinz-Peter Schiffer ◽  
Sven Grundmann
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Swirling Flow ◽  
Turbine Blades ◽  
Transfer Characteristic ◽  
Internal Cooling ◽  
Number Range ◽  
Flow Type ◽  
Magnetic Resonance Velocimetry ◽  
Swirl Generator

The presented study deals with the internal cooling of turbine blades by swirling flow. The sensitivity of this flow type is investigated towards Reynolds number, swirl intensity and the common geometric features of cooling ducts. The flow system consists of a straight and round channel that is attached to a tangential-type swirl generator. The channel outlet features various orifices and 180-degree-bends. The investigated Reynolds number range is Re = 2000…32000 and the geometric swirl numbers are S* = 1,3,5. The experiments were carried out with Magnetic Resonance Velocimetry for which water was used as flow medium. As the main outcome, it was found that the investigated flows are highly sensitive to the conditions at the outlet of the channel. But it was also discovered that for some channel outlets the flow field remains the same. The associated flow type features a favorable topology for heat transfer: The majority of mass is transported in the annular region close to the channel walls. Together with its high robustness, it is regarded as an applicable type for the internal cooling of turbine blades. A Large Eddy Simulation was conducted to analyze the heat transfer characteristic of this flow. For S*=3 and Re=20000, the simulation showed an averaged Nusselt number increase of factor 4.7 compared to fully-developed flow. However, a pressure loss increase of factor 43 must be considered as well. The presented measurements and simulations have led to a further understanding of swirling flows and proved these flows advantageous for the internal cooling of turbine blades.

Influence of Channel Geometry and Flow Variables on Cyclone Cooling of Turbine Blades

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Martin Bruschewski ◽  
Christian Scherhag ◽  
Heinz-Peter Schiffer ◽  
Sven Grundmann
Keyword(s):  
Heat Transfer ◽  
Swirling Flow ◽  
Turbine Blades ◽  
Transfer Characteristic ◽  
Internal Cooling ◽  
Eddy Simulation ◽  
Magnetic Resonance Velocimetry ◽  
Swirl Generator ◽  
Flow Features ◽  
Flow Variables

A study examining the internal cooling of turbine blades by swirling flow is presented. The sensitivity of swirling flow is investigated with regard to Reynolds number, swirl intensity, and the common geometric features of blade-cooling ducts. The flow system consists of a straight and round channel that is attached to a swirl generator with tangential inlets. Different orifices and 180-deg bends are employed as channel outlets. The experiments were carried out with magnetic resonance velocimetry (MRV) for which water was used as flow medium. As the main outcome, it was found that the investigated flows are highly sensitive to the conditions at the channel outlet. However, it was also discovered that for some outlet geometries the flow field remains the same. The associated flow features a favorable topology for heat transfer; the majority of mass is transported in the annular region close to the channel walls. Together with its high robustness, it is regarded as an applicable flow type for the internal cooling of turbine blades. A large eddy simulation (LES) was conducted to analyze the heat transfer characteristic of the associated flow for S0=3 and Re=20,000. The simulation showed an averaged Nusselt number increase of factor 4.7 compared to fully developed flow. However, a pressure loss increase of factor 43 must be considered as well.

The Effect of Axial Flow on Heat Transfer in Decaying, Swirling Flow in a Pipe

2003 ◽  
Author(s):  
Heather L. McClusky ◽  
Donald E. Beasley
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Swirling Flow ◽  
Axial Flow ◽  
Number Range ◽  
Tangential Flow ◽  
Nusselt Numbers ◽  
Swirl Generator ◽  
Inlet Conditions

Local Nusselt numbers were experimentally measured in decaying, swirling flow in a pipe. Using a tangential injection mechanism, the two inlet conditions examined in this study were tangential flow and superimposed tangential and axial flow. Local Nusselt numbers at the pipe inlet were greater for tangential flow than for superimposed tangential and axial flow at the same Reynolds number. Local Nusselt numbers increased as the amount of fluid injected tangentially was increased for the superimposed case. For both inlet conditions employed with the present swirl generator, the local Nusselt number approached the fully-developed value in the far field. At the exit of the pipe, L/D = 62.8, local Nusselt numbers were greater than the fully-developed Nusselt number; therefore, heat transfer enhancement was still present at the exit of the pipe. The effect of axial flow on the local Nusselt numbers is explored in this investigation for air and over a Reynolds number range of 12,000 to 29,000.

Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces

2013 ◽  
Author(s):  
Matthew A. Smith ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios ◽  
Parallel Configuration

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter. While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently. The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.

Study of Flow and Convective Heat Transfer in a Simulated Scaled Up Low Emission Annular Combustor

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Sunil Patil ◽  
Teddy Sedalor ◽  
Danesh Tafti ◽  
Srinath Ekkad ◽  
Yong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat ◽  
Swirling Flow ◽  
Numerical Study ◽  
Swirl Number ◽  
Maximum Heat ◽  
Number Range ◽  
Maximum Heat Transfer ◽  
Annular Combustor

Modern dry low emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the gas side difficult to predict and estimate. A coupled experimental–numerical study of swirling flow inside a DLE annular combustor model is used to determine the distribution of heat transfer on the liner walls. Three different Reynolds numbers are investigated in the range of 210,000–840,000 with a characteristic swirl number of 0.98. The maximum heat transfer coefficient enhancement ratio decreased from 6 to 3.6 as the flow Reynolds number increased from 210,000 to 840,000. This is attributed to a reduction in the normalized turbulent kinetic energy in the impinging shear layer, which is strongly dependent on the swirl number that remains constant at 0.98 for the Reynolds number range investigated. The location of peak heat transfer did not change with the increase in Reynolds number since the flow structures in the combustors did not change with Reynolds number. Results also showed that the heat transfer distributions in the annulus have slightly different characteristics for the concave and convex walls. A modified swirl number accounting for the step expansion ratio is defined to facilitate comparison between the heat transfer characteristics in the annular combustor with previous work in a can combustor. A higher modified swirl number in the annular combustor resulted in higher heat transfer augmentation and a slower decay with Reynolds number.

Numerical Investigation of Impingement Heat Transfer on a Flat and Square Pin-Fin Roughened Plates

2013 ◽  
Author(s):  
Chaoyi Wan ◽  
Yu Rao ◽  
Xiang Zhang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Investigation ◽  
Pressure Loss ◽  
Transfer Characteristic ◽  
Number Range ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Impingement Heat Transfer

A numerical investigation of the heat transfer characteristics within an array of impingement jets on a flat and square pin-fin roughened plate with spent air in one direction has been conducted. Four types of optimized pin-fin configurations and the flat plate have been investigated in the Reynolds number range of 15000–35000. All the computation results have been validated well with the data of published literature. The effects of variation of jet Reynolds number and different configurations on the distribution of the average and local Nusselt number and the related pressure loss have been obtained. The highest total heat transfer rate increased up to 162% with barely any extra pressure loss compared with that of the flat plate. Pressure distributions and streamlines have also been captured to explain the heat transfer characteristic.

Heat Transfer Predictions for U-Shaped Coolant Channels With Skewed Ribs and With Smooth Walls

1996 ◽  
Author(s):  
Bernhard Bonhoff ◽  
Uwe Tomm ◽  
Bruce V. Johnson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Computational Study ◽  
Flow Direction ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Internal Cooling ◽  
Smooth Wall ◽  
Wall Model

A computational study was performed for the flow and heat transfer in coolant passages with two legs connected with a U-bend and with dimensionless flow conditions typical of those in the internal cooling passages of turbine blades. The first model had smooth surfaces on all walls. The second model had opposing ribs staggered and angled at 45° to the main flow direction on two walls of the legs, corresponding to the coolant passage surfaces adjacent to the pressure and suction surfaces of a turbine airfoil. For the ribbed model, the ratio of rib height to duct hydraulic diameter equaled 0.1, and the ratio of rib spacing to rib height equaled 10. Comparisons of calculations with previous measurements are made for a Reynolds number of 25,000. With these conditions, the predicted heat transfer is known to be strongly influenced by the turbulence and wall models. The k-e model, the low Reynolds number RNG k-e and the differential Reynolds-stress model (RSM) were used for the smooth wall model calculation. Based on the results with the smooth walls, the calculations for the ribbed walls were performed using the RSM and k-e turbulence models. The high secondary flow induced by the ribs leads to an increased heat transfer in both legs. However, the heat transfer was nearly unchanged between the smooth wall model and the ribbed model within the bend region. The agreement between the predicted segment-averaged and previously-measured Nusselt numbers was good for both cases.

An Experimental Investigation of Heat Transfer in an Orthogonally Rotating Channel Roughened With 45 deg Criss-Cross Ribs on Two Opposite Walls

1991 ◽  
Vol 113 (3) ◽  
pp. 346-353 ◽  
Author(s):  
M. E. Taslim ◽  
L. A. Bondi ◽  
D. M. Kercher
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Rotation Number ◽  
Turbine Blades ◽  
Steady Increase ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios

Turbine blade cooling is imperative in advanced aircraft engines. The extremely hot gases that operate within the turbine section require turbine blades to be cooled by a complex cooling circuit. This cooling arrangement increases engine efficiency and ensures blade materials a longer creep life. One principle aspect of the circuit involves serpentine internal cooling passes throughout the core of the blade. Roughening the inside surfaces of these cooling passages with turbulence promoters provides enhanced heat transfer rates from the surface. The purpose of this investigation was to study the effect of rotation, aspect ratio, and turbulator roughness on heat transfer in these rib-roughened passages. The investigation was performed in an orthogonally rotating setup to simulate the actual rotation of the cooling passages. Single-pass channels, roughened on two opposite walls, with turbulators positioned at 45 deg angle to the flow, in a criss-cross arrangement, were studied throughout this experiment. The ribs were arranged such that their pitch-to-height ratio remained at a constant value of 10. An aspect ratio of unity was investigated under three different rib blockage ratios (turbulator height/channel hydraulic diameter) of 0.1333, 0.25, and 0.3333. A channel with an aspect ratio of 2 was also investigated for a blockage ratio of 0.25. Air was flown radially outward over a Reynolds number range of 15,000 to 50,000. The rotation number was varied from 0 to 0.3. Stationary and rotating cases of identical geometries were compared. Results indicated that rotational effects are more pronounced in turbulated passages of high aspect and low blockage ratios for which a steady increase in heat transfer coefficient is observed on the trailing side as rotation number increases while the heat transfer coefficient on the leading side shows a steady decrease with rotation number. However, the all-smooth-wall classical pattern of heat transfer coefficient variation on the leading and trailing sides is not followed for smaller aspect ratios and high blockage ratios when the relative artificial roughness is high.

scholarly journals Flow Regimes and Heat Transfer Characteristics in Combustion Chambers

2015 ◽  
Vol 12 (2) ◽  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Swirling Flow ◽  
Local Heat Transfer ◽  
Reacting Flow ◽  
Heat Transfer Characteristics ◽  
Swirl Number ◽  
Number Range ◽  
Transfer Characteristics ◽  
Combustor Liner

This paper presents a numerical computations are performed to investigate the convective heat transfer characteristics of a gas turbine can combustor under non reacting flow conditions in a Reynolds number range 50,000 to 600,000 with a characteristic swirl number of 0.7. A sample of computational predictions of flow behaviors under reacting conditions are also shown for swirling furnace flow of 0.52. The RNG (K-ɛ Model) predictions are compared with the experimental data of local heat transfer distribution on the combustor liner wall. It was observed that the flow field in the combustor is characterized by an expanding swirling flow, which impinges on the liner wall close to the inlet of the combustor. The peak heat transfer augmentation ratio (compared with fully developed pipe flow) reduces from 10.5 to 2.7. Additionally, the peak location does not change with Reynolds number since the flow structure in the combustor is also a function of the swirl number. The size of the corner recirculation zone near the combustor liner remains the same for all Reynolds numbers and hence the location of shear layer impingement and peak augmentation does not change. The heat transfer coefficient distribution on the liner wall predicted from the RNG (K-ɛ Model) is in good agreement with experimental values. The location and the magnitude of the peak heat transfer are predicted in very close agreement with the experiments.

scholarly journals Statistics of fully turbulent impinging jets

2017 ◽  
Vol 825 ◽  
pp. 795-824 ◽  
Author(s):  
Robert Wilke ◽  
Jörn Sesterhenn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbine Blades ◽  
Temperature Fluctuations ◽  
Impinging Jets ◽  
Positive Influence ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Reynolds Analogy ◽  
Number Range

Direct numerical simulations (DNS) of subsonic and supersonic impinging jets with Reynolds numbers of 3300 and 8000 are carried out to analyse their statistical properties with respect to heat transfer. The Reynolds number range is at low or moderate values in terms of practical applications, but very high regarding the technical possibilities of DNS. A Reynolds number of 8000 is technically relevant for the cooling of turbine blades. In this case, the flow is dominated by primary and secondary vortex rings. Statistics of turbulent heat fluxes and Reynolds stresses as well as the Nusselt number are provided and brought into accordance with these vortices. Velocity and temperature fluctuations were found to have a positive influence on cooling of the impinging plate. Beside the description of the flow, a second aim of this article is the provision of data for improvement of turbulence models. Modern large eddy simulations are still not able to precisely predict impingement heat transfer (Dairay et al., Intl J. Heat Fluid Flow, vol. 50 (0), 2014, pp. 177–187). Common relations between heat and mass transfer respectively temperature and velocity fields are applied to the impinging jet. These relations include the Reynolds and Chilton Colburn analogy, the Crocco–Busemann relation and the generalised Reynolds analogy (GRA). It was found that the first two deliver useful values if the distance to the jet axis is larger than one diameter, away from the strong pressure gradient around the stagnation point. The GRA, in contrast, precisely predicts the mean temperature field if no axial velocity gradient is present. The estimation of temperature fluctuations according to the GRA fails. As third main topic of this article, the influence of the Mach number on heat transfer and the flow field, is studied. Against the common practise of neglecting compressibility effects in experimental Nusselt correlations, we observed that higher Mach numbers (up to 1.1) have a positive influence on heat transfer in the deflection zone due to higher flow fluctuations.

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