A new cooling design for rib roughened two-pass channel having positive effects of rotation on heat transfer enhancement on both pressure and suction side internal walls of a gas turbine blade

Singh, Prashant; Li, Weihong; Ekkad, Srinath V.; Ren, Jing

doi:10.1016/j.ijheatmasstransfer.2017.07.128

“…As far as the flow development and convective heat transfer is concerned, this does not change the interpretation of results in the first pass for both stationary and rotating blades, but it does result in different flow and heat transfer on the ribbed walls in the second pass by the observation that the ribs are situated on the inner and outer walls of the bend whereas in conventional designs they are not. Recently, this type of duct design has been evaluated by Singh et al [100] to augment heat transfer on the suction as well as pressure surfaces during rotation. This would be accomplished in the design in Figure 2b by switching the flow direction where for positive rotation the wall adjoining the suction surface and the wall adjoin the pressure surface would both experience heat transfer augmentation.…”

Section: Geometry and Computational Domainmentioning

confidence: 99%

High Reynold Number LES of a Rotating Two-Pass Ribbed Duct

Tafti

¹

,

Dowd

²

,

Tan

³

2018

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Cooling of gas turbine blades is critical to long term durability. Accurate prediction of blade metal temperature is a key component in the design of the cooling system. In this design space, spatial distribution of heat transfer coefficients plays a significant role. Large-Eddy Simulation (LES) has been shown to be a robust method for predicting heat transfer. Because of the high computational cost of LES as Reynolds number (Re) increases, most investigations have been performed at low Re of O(104). In this paper, a two-pass duct with a 180° turn is simulated at Re = 100,000 for a stationary and a rotating duct at Ro = 0.2 and Bo = 0.5. The predicted mean and turbulent statistics compare well with experiments in the highly turbulent flow. Rotation-induced secondary flows have a large effect on heat transfer in the first pass. In the second pass, high turbulence intensities exiting the bend dominate heat transfer. Turbulent intensities are highest with the inclusion of centrifugal buoyancy and increase heat transfer. Centrifugal buoyancy increases the duct averaged heat transfer by 10% over a stationary duct while also reducing friction by 10% due to centrifugal pumping.

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“…Further, the authors showed that when the rotation number exceeds 0.25, thermal performance considerably improved due to rotation effects. Prashant et al [8,9] compared the effects due to ribs on single wall and two walls of a square channel. For Re 20000, Vribs fixed on two walls produced greater augmentation, and the trailing wall heat transfer in rotating condition was highest due to Coriolis effects.…”

Section: Introductionmentioning

confidence: 99%

Influence of Narrow Rectangular Channel ( $AR = 1 : 4$ ) on Heat Transfer and Friction for V- and W-Shaped Ribs in Turbine Blade Applications

Krishnaswamy

¹

,

Suresh

²

,

Ali

³

2021

International Journal of Photoenergy

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Effective cooling of blades with a nominal pressure drop is essential for performance augmentation and thermal management of gas turbines. Hence, present work is aimed at determining the heat transfer enhancement and friction for W- and V-shaped ribs inside a rectangular cooling channel having hydraulic diameter ( D h ) of 0.048 m and aspect ratio ( AR ) 1 : 4. Ribs are fixed facing downstream with angle of attack ( α ) 45° on opposite walls. Pitch ( P ) between two successive ribs is 25 mm for both cases. Continuous V- and W-shaped ribs with height to channel hydraulic diameter ratio ( e / D h ) 0.052 and 0.0416 and pitch to height ratio ( P / e ) 10 and 12.5, respectively, have been examined for Reynolds number ( Re ) range 20000-80000. Heat transfer augmentation achieved at Re 80000 is 1.94 and 1.8 times higher than Re 20000 for V- and W-shaped ribs, respectively. Streamwise and spanwise variations in local Nusselt number ratio are highest for V-shaped ribs, which are estimated to be 31% and 12%. For W-shaped ribs, variations are 17.5% and 3.5%. Nusselt number ( Nu ) is highest along span length 0.5 w for V-shaped ribs due to dominance of apex induced secondary flow. For W-shaped ribs, Nusselt number along the span lengths is found to be nearly same view uniformity in secondary flow. Maximum enhancement ( Nu / N u o ) estimated for both the rib shapes is 3.9 at Re 20000. Due to increased rib height, friction losses for V-shaped ribs are higher than W-shaped ribs. Maximum friction loss increment is estimated to be 85% for V-shaped ribs and 42% for W-shaped ribs between Re 20000 and 40000. For both rib shapes, impact of ribs is found to be greatest at Re 40000. Thermohydraulic performance ( THP ) for W-shaped ribs is superior to V-shaped ribs. Best THP achieved for W- and V-shaped ribs are 3.7 and 3.4 at Re 20000.

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“…Model B of their study showed that heat transfer augmentation on both leading and trailing sides of the twopass ribbed duct. Recently, Singh et al (13,14) studied heat transfer enhancement mechanism for cooling feature based on Model B of (12) by means of transient liquid crystal experiments. The authors exhibited the advantages of the model orientation where rotation actually favoured the heat transfer enhancement on both the walls.…”

Section: Introductionmentioning

confidence: 99%

Parallel rotation for negating Coriolis force effect on heat transfer

Sarja

¹

,

Singh

²

,

Ekkad

³

2020

Aeronaut. j.

2

0

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Gas turbine blades feature multi-pass internal cooling channels, through which relatively colder air bled from the compressor is routed to cool internal walls. Under rotation, due to the influence of Coriolis force and centrifugal buoyancy, heat transfer at the trailing side enhances and that at the leading side reduces, for a radially outward flow. This non-uniform temperature distribution results in increased thermal stress, which is detrimental to blade life. In this study, a rotation configuration is presented which can negate the Coriolis force effect on heat and fluid flow, thereby maintaining uniform heat transfer on leading and trailing walls. A straight, smooth duct of unit aspect ratio is considered to demonstrate the concept and understand the fluid flow within the channel and its interaction with the walls. The new design is compared against the conventional rotation design. Numerical simulations under steady-state condition were carried out at a Reynolds number of 25000, where the Rotation numbers were varied as 0, 0.1, 0.15, 0.2, 0.25. Realisable version of k-$\varepsilon$ model was used for turbulence modelling. It was observed that new rotation (parallel) configuration’s heat transfer on leading and trailing sides were near similar, and trailing side was marginally higher compared to leading side. An interesting phenomenon of secondary Coriolis effect is reported which accounts for the minor differences in heat transfer augmentation between leading and trailing walls. Due to centrifugal buoyancy, the fluid is pushed towards the radially outward wall, resulting in a counter-rotating vortex pair, which also enhances the heat transfer on leading and trailing walls when compared to stationary case.

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A new cooling design for rib roughened two-pass channel having positive effects of rotation on heat transfer enhancement on both pressure and suction side internal walls of a gas turbine blade

Cited by 43 publications

References 26 publications

High Reynold Number LES of a Rotating Two-Pass Ribbed Duct

High Reynold Number LES of a Rotating Two-Pass Ribbed Duct

Influence of Narrow Rectangular Channel ( $AR = 1 : 4$ ) on Heat Transfer and Friction for V- and W-Shaped Ribs in Turbine Blade Applications

Parallel rotation for negating Coriolis force effect on heat transfer

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A new cooling design for rib roughened two-pass channel having positive effects of rotation on heat transfer enhancement on both pressure and suction side internal walls of a gas turbine blade

Cited by 43 publications

References 26 publications

High Reynold Number LES of a Rotating Two-Pass Ribbed Duct

High Reynold Number LES of a Rotating Two-Pass Ribbed Duct

Influence of Narrow Rectangular Channel ( AR = 1 : 4 ) on Heat Transfer and Friction for V- and W-Shaped Ribs in Turbine Blade Applications

Parallel rotation for negating Coriolis force effect on heat transfer

Contact Info

Product

Resources

About

Influence of Narrow Rectangular Channel ( $AR = 1 : 4$ ) on Heat Transfer and Friction for V- and W-Shaped Ribs in Turbine Blade Applications