Interactions between heat transfer, flow field and flame stabilization in a micro-combustor with a bluff body

2013 ◽  
Vol 66 ◽  
pp. 72-79 ◽  
Author(s):  
Aiwu Fan ◽  
Jianlong Wan ◽  
Kaoru Maruta ◽  
Hong Yao ◽  
Wei Liu
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Micro Combustor ◽  
Transfer Flow

Simulation of Two-Dimensional Turbulent Recirculating Flow Field Behind a V-Shaped Bluff Body

1994 ◽  
Author(s):  
Z. Gu ◽  
M. A. R. Sharif
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Combustion Chambers ◽  
Recirculating Flow ◽  
Conservative Form ◽  
Curvilinear Grid ◽  
Predictor Corrector

Abstract The two-dimensional turbulent recirculating flow fields behind a V-shaped bluff body have been investigated numerically. Similar bluff bodies are used in combustion chambers for flame stabilization. The governing transport equations in conservative form are solved by a pressure based predictor-corrector method. The standard k-ϵ turbulence closure model and a boundary fitted multi-block curvilinear grid system are used in the computation. The code is validated against turbulent flow over a backward facing step problem. The predicted flow field behind the bluff body is also compared with experiment. It is found that while the qualitative features of the flow are well predicted, there is quantitative disagreement between the measurement and prediction. This disagreement can be partially attributed to the k-ϵ turbulence model which is known to be inadequate for recirculating flows. Parametric investigation of the flow field by varying the shape and size of the bluff body is also performed and the results are reported.

scholarly journals Flow Field Predictions of Bluff Body Introduced Micro Combustor

2016 ◽  
Vol 24 ◽  
pp. 420-427 ◽  
Author(s):  
C.G. Sarath ◽  
M. Sreejith ◽  
R.V. Reji
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Micro Combustor

Partially Premixed Flame Stabilization in the Presence of a Combined Swirl and Bluff Body Influenced Flowfield: An Experimental Investigation

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Rajesh Sadanandan ◽  
Aritra Chakraborty ◽  
Vinoth Kumar Arumugam ◽  
Satyanarayanan R. Chakravarthy
Keyword(s):  
Flow Field ◽  
Bluff Body ◽  
Reverse Flow ◽  
Fluid Dynamic ◽  
Thermal Power ◽  
Swirl Flow ◽  
Flame Stabilization ◽  
Dynamic Strain ◽  
Low Velocity ◽  
Divergent Flow

Abstract Optical and laser diagnostic measurements in a nonpremixed model gas turbine (GT) burner have been performed to investigate the effect of an increase in thermal power on the flame stabilization. The model GT burner has a large bluff body base with an annular swirl region, leading to a convergent-divergent flow field at the burner exit. Under the investigated conditions, the flame stabilizes predominantly in the diverging section characterized by the swirl flow with a central recirculation zone. With increasing thermal power, the reverse flow of hot burned gases is strengthened, with the hydroxyl radical (OH) planar laser induced fluorescence (PLIF) images indicating an increase in the temperature of the burned gases. The preferred flame stabilization location coincides with the inner shear layer between the reactant inflow and the reverse flow of hot burned gases. At high thermal power, the flame seems to stabilize in regions of high fluid dynamic strain rate, highlighting the influence of the reverse flowing burned gases in the evolution of the flammable mixture upstream. However, simultaneous and time-resolved measurements of the flow-field and scalar field are needed for direct quantification of this. The results are in agreement with the flame stabilization theories based on partial fuel-air mixing and streamline divergence. The flow is seen to decelerate upstream of the flame front and the flame stabilizes in a region of low velocity, created as a result of heat release diverging the streamlines ahead of it.

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.

Effect of Slot Injection and Effusion Array on the Liner Heat Transfer Coefficient of a Scaled Lean Burn Combustor With Representative Swirling Flow

2015 ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Becchi ◽  
Bruno Facchini ◽  
Alessio Picchi ◽  
Fabio Turrini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Flame Stabilization ◽  
Recirculation Region ◽  
Flow Conditions ◽  
Lean Burn ◽  
Cooling Flows ◽  
The Impact

International standards regarding polluting emissions from civil aircraft engines are becoming gradually even more stringent. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern aero-engine combustors is represented by lean burn technology. Swirl injectors are usually employed to provide the dominant flame stabilization mechanism coupled to high efficiency fuel atomization solutions. These systems generate very complex flow structures such as recirculations, vortex breakdown and processing vortex core, that affect the distribution and therefore the estimation of heat loads on the gas side of the liner as well as the interaction with the cooling system flows. The main purpose of the present work is to provide detailed measurements of Heat Transfer Coefficient (HTC) on the gas side of a scaled combustor liner highlighting the impact of the cooling flows injected through a slot system and an effusion array. Furthermore, for a deeper understanding of the interaction phenomena between gas and cooling flows, a standard 2D PIV (Particle Image Velocimetry) technique has been employed to characterize the combustor flow field. The experimental arrangement has been developed within EU project LEMCOTEC and consists of a non-reactive three sectors planar rig installed in an open loop wind tunnel. Three swirlers, replicating the real geometry of a GE Avio PERM (Partially Evaporated and Rapid Mixing) injector technology, are used to achieve representative swirled flow conditions in the test section. The effusion geometry is composed by a staggered array of 1236 circular holes with an inclination of 30deg, while the slot exit has a constant height of 5mm. The experimental campaign has been carried out using a TLC (Thermochromic Liquid Crystals) steady state technique with a thin Inconel heating foil and imposing several cooling flow conditions in terms of slot coolant consumption and effusion pressure drop. A data reduction procedure has been developed to take into account the non-uniform heat generation and the heat loss across the liner plate. Results, in terms of 2D maps and averaged distributions of HTC have been supported by flow field measurements with 2D PIV technique focussed on the corner recirculation region.

Variations of Anchoring Pattern of a Bluff-Body Stabilized Laminar Premixed Flame as a Function of the Wall Temperature

2016 ◽  
Author(s):  
Sandrine Berger ◽  
Stéphane Richard ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Combustion Chamber ◽  
Wall Temperature ◽  
Bluff Body ◽  
Flame Stabilization ◽  
Premixed Flame ◽  
Strong Impact ◽  
Flame Holder ◽  
Thermal Boundary Conditions

Aircraft engine components are subject to hostile thermal environments. The solid parts in the hot stages encounter very high temperature levels and gradients that are critical for the engine lifespan. Combustion chamber walls in particular exhibit very heterogeneous thermal fields. The prediction of this specific thermal field is a very complex task as it results from complex interactions between fresh gas injections, cooling flow distributions, combustion, flame stabilization and thermal transfers to the solids. All these phenomena are tightly coupled and do not evolve linearly. Today, the design phase of a combustion chamber is strongly enhanced by the use of high fidelity computations such as Large Eddy Simulations (LES). However, thermal boundary conditions are rarely well known and are thus treated either as adiabatic or as approximated isothermal conditions. Such approximations on thermal boundary conditions can lead to several errors and inaccurate predictions of the combustion chamber flow field. With this in mind and to foresee the potential difficulties of LES based Conjugate Heat Transfer (CHT) predictions, the effect of the wall temperature on a laminar premixed flame stabilization is numerically investigated in this paper for an academic configuration. The considered case consists of a squared cylinder flame holder at a low Reynolds number for which several wall-resolved Direct Numerical Simulations (DNS) are performed varying the bluff-body wall thermal condition. In such a set-up, the reactive flow and the flame holder interact in a complex way with an underlying strong impact of the wall temperature. For a baseline configuration where the flame holder wall temperature is fixed at 700K, the flow field is steady with a flame stabilized thanks to the recirculation zone of the flame holder. As the wall temperature is decreased, the position of the stabilized flame moves further downstream. The flame remains steady until a threshold cold temperature is reached below which an instability appears. For solid temperatures above 700 K, the flame is seen to move further and further upstream. For very hot conditions, the flame even stabilizes ahead of the bluff-body. The various flow solution bifurcations as the flame stabilization evolves are detailed in this paper. Heat flux distribution along the bluff-body walls are observed to be dictated by the flame stabilization process illustrating different mechanisms while integration of these fluxes on the whole flame holder surface confirms that various theoretical equilibrium states may exist for this configuration. This suggests that computation of more realistic cases including thermal conduction in the bluff-body solid part could lead to different converged results depending on the initial thermal state.

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.

Effect of Slot Injection and Effusion Array on the Liner Heat Transfer Coefficient of a Scaled Lean-Burn Combustor With Representative Swirling Flow

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Antonio Andreini ◽  
Bruno Facchini ◽  
Riccardo Becchi ◽  
Alessio Picchi ◽  
Fabio Turrini
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Flame Stabilization ◽  
Recirculation Region ◽  
Flow Conditions ◽  
Lean Burn ◽  
Cooling Flows ◽  
Piv Technique

International standards regarding polluting emissions from civil aircraft engines are becoming gradually even more stringent. Nowadays, the most prominent way to meet the target of reducing NOx emissions in modern aero-engine combustors is represented by lean-burn technology. Swirl injectors are usually employed to provide the dominant flame stabilization mechanism coupled to high-efficiency fuel atomization solutions. These systems generate very complex flow structures, such as recirculations, vortex breakdown, and processing vortex core, which affect the distribution and therefore the estimation of heat loads on the gas side of the liner as well as the interaction with the cooling system flows. The main purpose of the present work is to provide detailed measurements of heat transfer coefficient (HTC) on the gas side of a scaled combustor liner highlighting the impact of the cooling flows injected through a slot system and an effusion array. Furthermore, for a deeper understanding of the interaction phenomena between gas and cooling flows, a standard two-dimensional (2D) particle image velocimetry (PIV) technique has been employed to characterize the combustor flow field. The experimental arrangement has been developed within EU project LEMCOTEC and consists of a nonreactive three sectors planar rig installed in an open-loop wind tunnel. Three swirlers, replicating the real geometry of a GE Avio partially evaporated and rapid mixing (PERM) injector technology, are used to achieve representative swirled flow conditions in the test section. The effusion geometry is composed by a staggered array of 1236 circular holes with an inclination of 30 deg, while the slot exit has a constant height of 5 mm. The experimental campaign has been carried out using a thermochromic liquid crystals (TLCs) steady-state technique with a thin Inconel heating foil and imposing several cooling flow conditions in terms of slot coolant consumption and effusion pressure drop. A data reduction procedure has been developed to take into account the nonuniform heat generation and the heat loss across the liner plate. Results in terms of 2D maps and averaged distributions of HTC have been supported by flow field measurements with 2D PIV technique focussed on the corner recirculation region.

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