The Effect of the Pocket on the Heat Transfer of Endwall With Bluff Body in the Rear Part of Gas Turbine

2017 ◽  
Author(s):  
Jian Liu ◽  
Safeer Hussain ◽  
Lei Wang ◽  
Gongnan Xie ◽  
Bengt Sundén ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Bluff Body ◽  
Guide Vane ◽  
Rectangular Channel ◽  
High Heat ◽  
Bluff Bodies ◽  
Recirculating Flow ◽  
High Heat Transfer ◽  
Rear Part

A pocket cavity is generated at the connection of two parts, such as the transition part between the low pressure turbine (LPT) and outlet guide vane (OGV) in a gas turbine engine. A bluff body, working as a heat transfer enhancement part or supporting strength part, has tremendous engineering applications in turbomachinery. In the present work, the effect of the pocket on the heat transfer of endwall with a bluff body in the rear part of gas turbine is investigated. A simplified triangular pocket cavity is built in a rectangular channel and two bluff bodies, a cylinder or a cuboid is attached downstream on the endwall. The heat transfer and fluid flow on the endwall are investigated experimentally and numerically. Liquid Crystal Thermography (LCT) is employed to measure the heat transfer over the pocket surface with Reynolds number ranging from 87,597, to 218,994. The turbulent flow details are provided by numerically calculations based on the commercial software Fluent 17.0. Based on the results, high heat transfer areas are usually found at the boundary of the pocket cavity and vortex street shedding regions around the bluff body. When a pocket cavity is placed in the upstream of a bluff body, the endwall heat transfer around the bluff body is obviously decreased due to the disturbance by the pocket. There are no recirculating flows in front of the tested cylinder while this is not applicable for the cuboid case. The recirculating flow behind the bluff bodies forms a three-dimensional flow structure rotating in two directions.

Investigation of Heat Transfer and Fluid Flow Over Pocket Cavity in the Rear Part of Gas Turbine

2016 ◽  
Author(s):  
Jian Liu ◽  
Chenglong Wang ◽  
Lei Wang ◽  
Gongnan Xie ◽  
Martin Andersson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Gas Turbine ◽  
Guide Vane ◽  
Gas Turbine Engine ◽  
Turbine Engine ◽  
Recirculating Flow ◽  
Fillet Radius ◽  
Rear Part ◽  
Peak Value

The pocket cavity is generated at the transition part between the low pressure turbine (LPT) and outlet guide vane (OGV) in a gas turbine engine. Because the important connection with OGV, the heat transfer and fluid flow need to be investigated and analyzed. In the present work, a simplified triangular pocket cavity is built and heat transfer and fluid flow are investigated experimentally and numerically. Liquid Crystal Thermography (LCT) is employed to measure the heat transfer over the pocket surface with Reynolds number ranging from 54,054 to 135,135. In addition, two fillets with different radii are designed to investigate the flow structures over the pocket surface. The turbulent flow details are provided by numerically calculations based on the commercial software Fluent 15.0 with a validated turbulence model. Based on the results, the highest heat transfer value is located in the downstream boundary of the pocket cavity where the strongest flow impingement happens. The smaller fillet radius presents a higher heat transfer peak value and also induces stronger recirculating flow inside the pocket cavity. Considering the design requirement in the rear part of a gas turbine, i.e., to decrease the heat transfer peak value, a larger fillet radius is recommended for practical design. The heat transfer and flow details also provide a reliable reference for gas turbine engine design.

Review of the Development of Compact, High Performance Heat Exchangers for Gas Turbine Applications

2006 ◽  
Author(s):  
Neal R. Herring ◽  
Stephen D. Heister
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
High Performance ◽  
High Heat ◽  
Swirl Flow ◽  
Acoustic Oscillations ◽  
Transfer Coefficients ◽  
High Heat Transfer

This study provides a review of the current state-of-the-art in compact heat exchangers and their application to gas turbine thermal management. Specifically, the challenges and potential solutions for a cooled cooling air system using the aircraft fuel as a heat sink were analyzed. As the sensible heat absorbed by the fuel in future engines is increased, the fuel will be exposed to increasingly hotter temperatures. This poses a number of design challenges for fuel-air heat exchangers. The most well known challenge is fuel deposition or coking. Another problem encountered at high fuel temperatures is thermo-acoustic oscillations. Thermo-acoustic oscillations have been shown to occur in many fluids when heated near the critical point, yet the mechanism of these oscillations is poorly understood. In some cases these instabilities have been strong enough cause failure in the thin walled tubes used in heat exchangers. For the specific application of a fuel-air heat exchanger, the advantages of a laminar flow device are discussed. These devices make use of the thermal entry region to achieve high heat transfer coefficients. To increase performance further, heat transfer enhancement techniques were reviewed and the feasibility for aerospace heat exchangers was analyzed. Two of the most basic techniques for laminar flow enhancement include tube inserts and swirl flow devices. Additionally, the effects of these devices on both coking and instabilities have been assessed.

The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer—Part II: Time-Mean Results

2005 ◽  
Vol 128 (4) ◽  
pp. 755-762 ◽  
Author(s):  
T. J. Praisner ◽  
C. R. Smith
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Field Data ◽  
Bluff Body ◽  
Symmetry Plane ◽  
Horseshoe Vortex ◽  
High Heat ◽  
Thermochromic Liquid Crystal ◽  
Mean Flow ◽  
High Heat Transfer

Time-mean endwall heat transfer and flow-field data in the endwall region are presented for a turbulent juncture flow formed with a symmetric bluff body. The experimental technique employed allowed the simultaneous recording of instantaneous particle image velocimetry flow field data, and thermochromic liquid-crystal-based endwall heat transfer data. The time-mean flow field on the symmetry plane is characterized by the presence of primary (horseshoe), secondary, tertiary, and corner vortices. On the symmetry plane the time-mean horseshoe vortex displays a bimodal vorticity distribution and a stable-focus streamline topology indicative of vortex stretching. Off the symmetry plane, the horseshoe vortex grows in scale, and ultimately experiences a bursting, or breakdown, upon experiencing an adverse pressure gradient. The time-mean endwall heat transfer is dominated by two bands of high heat transfer, which circumscribe the leading edge of the bluff body. The band of highest heat transfer occurs in the corner region of the juncture, reflecting a 350% increase over the impinging turbulent boundary layer. A secondary high heat-transfer band develops upstream of the primary band, reflecting a 250% heat transfer increase, and is characterized by high levels of fluctuating heat load. The mean upstream position of the horseshoe vortex is coincident with a region of relatively low heat transfer that separates the two bands of high heat transfer.

Conjugate Heat Transfer Modelling in Film Cooled Blades

2004 ◽  
Author(s):  
F. Montomoli ◽  
P. Adami ◽  
S. Della Gatta ◽  
F. Martelli
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Gas Turbines ◽  
Conjugate Heat Transfer ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
High Heat ◽  
Test Case ◽  
Turbine Cooling ◽  
High Heat Transfer

A reliable and accurate prediction of temperature field in hot components plays a key role in design process of modern gas turbines. The first stages of turbine and the combustor basket are usually subjected to high heat transfer rates and hot gas temperatures exceed the melting point of the employed alloys. The accurate knowledge of temperature distribution could extend the life of critical components through an accurate design of coolant systems. The present work concerns the upgrade of the finite volume CFD (Computational Fluid Dynamic) solver HybFlow, (see Adami et al.[1]) to simulate heat transfer in gas turbine cooling devices. In particular, the conjugate simulation of flow field heat transfer and metal heat conduction has been considered. To this aim, the original solver has been coupled to a routine solving the Fourier equation in solid domain. This modification allows the “conjugate heat transfer” investigation of heat transfer in fluid flow and solid domain simultaneously. The code has been validated through two different test-case applications. The first is a laminar flow over a flat plate, while the second is a film-cooled plate. Finally, a complete 3D film cooled NGV (Nozzle Guide Vane) has been investigated as an example for a more complex application. The simulation couples the thermal field inside the metal and the flow field in the vane, in the two plenum channels and in the six rows of cooling channels as well.

Experimental and Numerical Analysis of High Heat Transfer Phenomenon in Minichannel Gaseous Cooling

2006 ◽  
Author(s):  
Kazuo Hara ◽  
Masato Furukawa ◽  
Naoki Akihiro
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Flow System ◽  
High Heat ◽  
Transfer Performance ◽  
Channel Inlet ◽  
Two Stage ◽  
Impingement Jet ◽  
Recirculating Flow ◽  
High Heat Transfer

The authors have reported that minichannel flow system had high heat transfer coefficient, the reason of which was investigated experimentally and numerically for single and array minichannels combined with impingement flow system. The diameter D of the channel was 1.27 mm and length to diameter ratio L/D was 5. The minichannel array was so called shower head which was constructed by 19 minichannels located at the apex of equilateral triangle, the side length S of which was 4 mm. Single stage block was used to investigate the heat transfer without impinging flow system. Two stage blocks were used to compose an impingement heat exchanger system with an impingement distance of H. H/D ranged from 1.97 to 7.87. A comparison of heat transfer performance was made between minichannel flow system and impingement jet using the single and two stage heat transfer experimental data. It was found that heat transfer performance of the minichannel was equivalent to that of impingement jet. The mechanism of high heat transfer was studied numerically by the Reynolds averaged Navier-Stokes equation and k-ω turbulence model. The limiting streamline pattern was correlated well to the surface heat flux distribution. The high heat transfer in the single minichannel was achieved by suppressing the development of boundary layer under strong pressure gradient near the channel inlet and by the formation of large recirculating flow system in the downstream plenum of the minichannel exit. These heat transfer mechanisms became dominant when the channel size fallen into the regime of minichannel. For the array of 19 minichannels, the high heat transfer around the channel inlet was also observed clearly in the target plate of the impingement jet where minichannels of second stage were bored to exhaust the fluid of impingement jet.

Effects of the Location of the Pocket Cavity on Heat Transfer and Flow Characteristics of the Endwall With a Symmetrical Vane

2018 ◽  
Author(s):  
Jian Liu ◽  
Safeer Hussain ◽  
Lei Wang ◽  
Gongnan Xie ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Guide Vane ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Boundary Edge ◽  
Head Region ◽  
High Heat Transfer ◽  
Smooth Channel

A pocket cavity is generated at the junction position of the Low Pressure Turbine (LPT) and the Outlet Guide Vane (OGV) in the rear part of a gas turbine engine. The OGV mainly controls the exhaust flow exiting and provides structural strength of the main engine frame. In the present work, the effect the location of the pocket on the heat transfer of the endwall with a symmetrical vane is investigated. A triangular pocket cavity is built in a rectangular channel and a symmetric vane is put on the endwall downstream of the pocket cavity. Heat transfer and turbulent flow characteristics over the endwall are investigated experimentally and numerically. The distance between the pocket cavity and the symmetrical vane is varied from 10 cm, 15 cm, and 20 cm. Liquid Crystal Thermography (LCT) is employed to measure the heat transfer over the endwall at Reynolds number ranging from 87,600 to 219,000. The turbulent flow details are presented by numerical calculations with the turbulence models, i.e., the k-ω SST model. From this study, high heat transfer regions are usually found at where flow impingement appears, i.e., the pocket boundary edge region and the vane head region. Compared with the case of the smooth channel, the heat transfer is decreased when a pocket cavity is placed upstream of the vane. With the distance between the pocket cavity and the vane becoming larger, the effect of the pocket cavity is weakened and the heat transfer is approaching the smooth channel case, i.e., case 0. The pocket cavity strengthens the flow shedding and separates the flow away from the endwall. The pushed upward flow weakens the flow impingement on the vane and then leads to the decreased heat transfer around the vane.

Fibre Optic Interferometric Heat Transfer Sensors for Transient Flow Wind Tunnels

1993 ◽  
Author(s):  
S. R. Kidd ◽  
J. S. Barton ◽  
J. D. C. Jones ◽  
K. S. Chana ◽  
I. W. Matthews
Keyword(s):  
Heat Transfer ◽  
Optical Fibre ◽  
Optical Sensors ◽  
Transient Flow ◽  
Guide Vane ◽  
Single Mode ◽  
High Heat ◽  
Sensing Element ◽  
High Heat Transfer ◽  
Nozzle Guide

A new type of heat transfer sensor has been developed in which the sensing element is a short length (∼3mm) of single mode optical fibre acting as a Fabry-Perot interferometer. The reflected light intensity follows a periodic transfer function, and the phase change is proportional to the sensor’s spatially averaged temperature. We present results from three optical fibre sensors embedded as calorimeter gauges in a ceramic nozzle guide vane end wall model exposed to a transient heat flux of ∼100 kWm−2 in the Isentropic Light Piston Facility at DRA Pyestock Famborough, and validated by comparison with previous data from platinum thin film resistance gauges. The optical sensors exhibit high spatial resolution (∼5μm), high heat transfer resolution (∼1kWm−2), and wide temperature measurement bandwidth (100kHz) with intrinsic calibration. No electrical connections to the measurement volume are required and multiplexing is possible.

The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer: Part 2 — Time-Mean Results

2005 ◽  
Author(s):  
T. J. Praisner ◽  
C. R. Smith
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Field Data ◽  
Bluff Body ◽  
Symmetry Plane ◽  
Horseshoe Vortex ◽  
High Heat ◽  
Thermochromic Liquid Crystal ◽  
Mean Flow ◽  
High Heat Transfer

Time-mean endwall heat transfer and flow-field data in the endwall region are presented for a turbulent juncture flow formed with a symmetric bluff body. The experimental technique employed allowed the simultaneous recording of instantaneous particle image velocimetry flow field data, and thermochromic liquid-crystal-based endwall heat transfer data. The time-mean flow field on the symmetry plane is characterized by the presence of primary (horseshoe), secondary, tertiary, and corner vortices. On the symmetry plane the time-mean horseshoe vortex displays a bimodal vorticity distribution and a stable-focus streamline topology indicative of vortex stretching. Off the symmetry plane, the horseshoe vortex grows in scale, and ultimately experiences a bursting, or breakdown, upon experiencing an adverse pressure gradient. The time-mean endwall heat transfer is dominated by two bands of high heat transfer, which circumscribe the leading edge of the bluff body. The band of highest heat transfer occurs in the corner region of the juncture, reflecting a 350% increase over the impinging turbulent boundary layer. A secondary high heat-transfer band develops upstream of the primary band, reflecting a 250% heat transfer increase, and is characterized by high levels of fluctuating heat load. The mean upstream position of the horseshoe vortex is coincident with a region of relatively low heat transfer that separates the two bands of high heat transfer.

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

2020 ◽  
pp. 095441002096469
Author(s):  
Weijie Wang ◽  
Shaopeng Lu ◽  
Hongmei Jiang ◽  
Qiusheng Deng ◽  
Jinfang Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
High Heat ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Cavity Depth ◽  
High Heat Transfer ◽  
Blade Tip ◽  
High Heat Transfer Coefficient

Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

Possible Mechanisms for Thermal Conductivity Enhancement in Nanofluids

2006 ◽  
Author(s):  
Amit Gupta ◽  
Xuan Wu ◽  
Ranganathan Kumar
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Brownian Dynamics ◽  
Lattice Vibration ◽  
Experimental Studies ◽  
High Heat ◽  
Conductivity Enhancement ◽  
High Heat Transfer ◽  
Dynamics Simulations

This study discusses the merits of various physical mechanisms that are responsible for enhancing the heat transfer in nanofluids. Experimental studies have cemented the claim that ‘seeding’ liquids with nanoparticles can increase the thermal conductivity of the nanofluid by up to 40% for metallic and oxide nanoparticles dispersed in a base liquid. Experiments have also shown that the rise in conductivity of the nanofluid is highly dependent on the size and concentration of the nanoparticles. On the theoretical side, traditional models like Maxwell or Hamilton-Crosser models cannot explain this unusually high heat transfer. Several mechanisms have been postulated in the literature such as Brownian motion, thermal diffusion in nanoparticles and thermal interaction of nanoparticles with the surrounding fluid, the formation of an ordered liquid layer on the surface of the nanoparticle and microconvection. This study concentrates on 3 possible mechanisms: Brownian dynamics, microconvection and lattice vibration of nanoparticles in the fluid. By considering two nanofluids, copper particles dispersed in ethylene glycol, and silica in water, it is determined that translational Brownian motion of the nanoparticles, presence of an interparticle potential and the microconvection heat transfer are mechanisms that play only a smaller role in the enhancement of thermal conductivity. On the other hand, the lattice vibrations, determined by molecular dynamics simulations show a great deal of promise in increasing the thermal conductivity by as much as 23%. In a simplistic sense, the lattice vibration can be regarded as a means to simulate the phononic transport from solid to liquid at the interface.

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