Detailed Heat Transfer in a Two Pass Internal Cooling Duct With Rib Turbulators Using Wall Modeled Large Eddy Simulations (WMLES)

2012 ◽  
Author(s):  
Sukhjinder Singh ◽  
Danesh Tafti
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulations ◽  
Internal Cooling ◽  
Large Eddy ◽  
Rib Turbulators

Large-Eddy Simulation With Zonal Near Wall Treatment of Flow and Heat Transfer in a Ribbed Duct for the Internal Cooling of Turbine Blades

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Sunil Patil ◽  
Danesh Tafti
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Large Eddy Simulations ◽  
Internal Cooling ◽  
Mean Flow ◽  
Flow And Heat Transfer ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Near Wall

Large eddy simulations of flow and heat transfer in a square ribbed duct with rib height to hydraulic diameter of 0.1 and 0.05 and rib pitch to rib height ratio of 10 and 20 are carried out with the near wall region being modeled with a zonal two layer model. A novel formulation is used for solving the turbulent boundary layer equation for the effective tangential velocity in a generalized co-ordinate system in the near wall zonal treatment. A methodology to model the heat transfer in the zonal near wall layer in the large eddy simulations (LES) framework is presented. This general approach is explained for both Dirichlet and Neumann wall boundary conditions. Reynolds numbers of 20,000 and 60,000 are investigated. Predictions with wall modeled LES are compared with the hydrodynamic and heat transfer experimental data of (Rau et al. 1998, “The Effect of Periodic Ribs on the Local Aerodynamic and Heat Transfer Performance of a Straight Cooling Channel,”ASME J. Turbomach., 120, pp. 368–375). and (Han et al. 1986, “Measurement of Heat Transfer and Pressure Drop in Rectangular Channels With Turbulence Promoters,” NASA Report No. 4015), and wall resolved LES data of Tafti (Tafti, 2004, “Evaluating the Role of Subgrid Stress Modeling in a Ribbed Duct for the Internal Cooling of Turbine Blades,” Int. J. Heat Fluid Flow 26, pp. 92–104). Friction factor, heat transfer coefficient, mean flow as well as turbulent statistics match available data closely with very good accuracy. Wall modeled LES at high Reynolds numbers as presented in this paper reduces the overall computational complexity by factors of 60–140 compared to resolved LES, without any significant loss in accuracy.

LES Simulation and Experimental Measurement of Fully Developed Ribbed Channel Flow and Heat Transfer

2002 ◽  
Author(s):  
Kazunori Watanabe ◽  
Toshihiko Takahashi
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Rotor Blade ◽  
Large Eddy Simulations ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Ribbed Channel ◽  
Flow And Heat Transfer ◽  
Large Eddy

Ribbed channel flow is adopted for internal cooling of a 1300 °C class gas turbine first stage rotor blade. Heat transfer characteristics of transverse ribbed channel flow were examined using LES (Large Eddy Simulations) and by experiments. The flow was examined over the range of Reynolds number around 105 that are closer to the actual engine conditions. Computational results agreed reasonably well with experimental results. Heat transfer enhancement mechanism in a ribbed channel flow was shown to be caused by advecting eddy structure and interference of a rib.

Large-Eddy Simulations of Heat Transfer in a Ribbed Channel for Internal Cooling of Turbine Blades

2003 ◽  
Author(s):  
D. K. Tafti
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Large Eddy Simulations ◽  
Internal Cooling ◽  
Mean Flow ◽  
Square Channel ◽  
Nusselt Numbers ◽  
Separated Shear Layer ◽  
Friction Factors ◽  
Large Eddy

Large-Eddy Simulations (LES) are performed in a ribbed square channel with rib height to hydraulic diameter ratio of 0.1, and rib pitch to rib height ratio of 10. The calculations are performed for a nominal bulk Reynolds number of 20,000. Hydrodynamic and thermal fully-developed conditions are assumed. Results from two mesh resolutions, 963 and 1283 are presented and compared to available data in the literature. Time evolution, mean, and turbulent quantities are presented, together with the heat transfer. Both calculations capture the mean flow structures with precision and compare well with experimental data. Turbulent rms quantities also agree extremely well with available measurements. The finer mesh resolves the separated shear layer with greater precision and differences of 10–15% are observed between the two calculations. Similar differences are observed in the predictions of friction factors and Nusselt numbers between the two meshes. The friction factor and Nusselt number are underpredicted when compared to measurements in the literature.

LES Simulations of Rotating Two-Pass Ribbed Duct With Coriolis and Centrifugal Buoyancy Forces at Re=100,000

2016 ◽  
Author(s):  
Cody Dowd ◽  
Danesh Tafti
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Large Eddy Simulations ◽  
The Other ◽  
Coriolis Forces ◽  
Flow And Heat Transfer ◽  
Large Eddy ◽  
Buoyancy Forces ◽  
First Pass ◽  
Duct Geometry

The focus of this research is to predict the flow and heat transfer in a rotating two-pass duct geometry with staggered ribs using Large-Eddy Simulations (LES). The geometry consists of a U-Bend with 17 ribs in each pass. The ribs are staggered with an e/Dh = 0.1 and P/e = 10. LES is performed at a Reynolds number of 100,000, a rotation number of 0.2 and buoyancy parameters (Bo) of 0.5 and 1.0. The effects of Coriolis forces and centrifugal buoyancy are isolated and studied individually. In all cases it is found that increasing Bo from 0.5 to 1.0 at Ro = 0.2 has little impact on heat transfer. It is found that in the first pass, the heat transfer is quite receptive to Coriolis forces which augment and attenuate heat transfer at the trailing and leading walls, respectively. Centrifugal buoyancy, on the other hand has a bigger effect in augmenting heat transfer at the trailing wall than in attenuating heat transfer at the leading wall. On contrary, it aids heat transfer in the second half of the first pass at the leading wall by energizing the flow near the wall. The heat transfer in the second pass is dominated by the highly turbulent flow exiting the bend. Coriolis forces have no impact on the augmentation of heat transfer on the leading wall till the second half of the passage whereas it attenuates heat transfer at the trailing wall as soon as the flow exits the bend. Contrary to phenomenological arguments, inclusion of centrifugal buoyancy augments heat transfer over Coriolis forces alone on both the leading and trailing walls of the second pass.

Heat Transfer in a Rotating Cooling Channel (AR = 2:1) With Rib Turbulators and a Tip Turning Vane

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Andrew F. Chen ◽  
Hao-Wei Wu ◽  
Nian Wang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement ◽  
Rib Turbulators ◽  
Effects Of Rotation ◽  
Cooling Passage ◽  
Turbine Airfoils

Experimental investigation on rotation and turning vane effects on heat transfer was performed in a two-pass rectangular internal cooling channel. The channel has an aspect ratio of AR = 2:1 and a 180 deg tip-turn, which is a scaled up model of a typical internal cooling passage of gas turbine airfoils. The leading surface (LS) and trailing surface (TS) are roughened with 45 deg angled parallel ribs (staggered P/e = 8, e/Dh = 0.1). Tests were performed in a pressurized vessel (570 kPa) where higher rotation numbers (Ro) can be achieved with a maximum Ro = 0.42. Five Reynolds numbers (Re) were examined (Re = 10,000–40,000). At each Reynolds number, five rotational speeds (Ω = 0–400 rpm) were considered. Results showed that rotation effects are stronger in the tip regions as compared to other surfaces. Heat transfer enhancement up to four times was observed on the tip wall at the highest rotation number. However, heat transfer enhancement is reduced to about 1.5 times with the presence of a tip turning vane at the highest rotation number. Generally, the tip turning vane reduces the effects of rotation, especially in the turn portion.

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