Investigation of unsteady combustion of methane-air flame in a model combustion chamber with swirling flow

Abstract The present paper reports on the investigation of unsteady combustion of a methane-air mixture, including combustion at increased pressure in the combustion chamber and increased temperature of mixture heating for a model gas-turbine swirl burner based on a design by Turbomeca. To measure the velocity and OH fluorescence fields in the flows a combination of stereoscopic PIV and acetone PLIF systems is used. In all cases, the flow dynamics is associated with the movement of large-scale vortex structures in the inner and outer mixing layers and the flow structure corresponds to a swirling jet with a central recirculation zone containing combustion products. An increase in the heating temperature of the mixture and pressure in the combustion chamber leads to a periodic partial separation of the flame from the model swirl nozzle. However, the flow of fuel through the central channel will stabilize the flame.

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Experimental and computational investigations of flow dynamics in LPP combustor

The Aeronautical Journal ◽

10.1017/aer.2017.31 ◽

2017 ◽

Vol 121 (1240) ◽

pp. 790-802 ◽

Cited By ~ 1

Author(s):

Y. W. YAN ◽

Y. P. Liu ◽

Y. C. Liu ◽

J. H. Li

Keyword(s):

Recirculation Zone ◽

Swirling Flow ◽

Mixing Layer ◽

Experimental Tests ◽

Flow Dynamics ◽

Reynolds Stresses ◽

Lean Combustion ◽

Low Emission ◽

Image Velocimetry ◽

Combustion Technology

ABSTRACTA Lean Premixed Prevaporised (LPP) low-emission combustor with a staged lean combustion technology was developed. In order to study cold-flow dynamics in the LPP combustor, both experimental tests using the particle image velocimetry (PIV) to quantify the flow dynamics and numerical simulation using the commercial software (FLUENT) were conducted, respectively. Numerical results were in good agreement with the experimental data. It is shown from the observation of the results that: there is a Primary Recirculation Zone (PRZ), a Corner Recirculation Zone (CRZ) and a Lip Recirculation Zone (LRZ) in the LPP combustor, and the exchanges of mass, momentum and energy between pilot swirling flow and primary swirling flow are contributed by the velocity gradients, and the shear flow is transformed into a mixing layer exhibiting the higher Reynolds stresses, which suggests the mixing process is strictly affected by the Reynolds stresses.

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Significant of Isothermal Flow Studies for High Swirling Flow in Unconfined Burner

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.789-790.477 ◽

2015 ◽

Vol 789-790 ◽

pp. 477-483

Author(s):

A.R. Norwazan ◽

M.N. Mohd Jaafar

Keyword(s):

Flow Field ◽

Combustion Chamber ◽

Turbulent Flows ◽

Recirculation Zone ◽

Swirling Flow ◽

Numerical Study ◽

Tangential Velocity ◽

Radial Distance ◽

Navier Stokes ◽

Reacting Flow

This paper is presents numerical simulation of isothermal swirling turbulent flows in a combustion chamber of an unconfined burner. Isothermal flows of with three different swirl numbers, SN of axial swirler are considered to demonstrate the effect of flow axial velocity and tangential velocity to define the center recirculation zone. The swirler is used in the burner that significantly influences the flow pattern inside the combustion chamber. The inlet velocity, U0 is 30 m/s entering into the burner through the axial swirler that represents a high Reynolds number, Re to evaluate the differences of SN. The significance of center recirculation zone investigation affected by differences Re also has been carried out in order to define a good mixing of air and fuel. A numerical study of non-reacting flow into the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) realizable k-ε turbulence approach method was applied with the eddy dissipation model. An attention is focused in the flow field behind the axial swirler downstream that determined by transverse flow field at different radial distance. The results of axial and tangential velocity were normalized with the U0. The velocity profiles’ behaviour are obviously changes after existing the swirler up to x/D = 0.3 plane. However, their flow patterns are similar for all SN after x/D = 0.3 plane towards the outlet of a burner.

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Influence of Large-Scale Vortex Movement in Lower Recirculation Zone on Instable Flow Field in the Mold

ISIJ International ◽

10.2355/isijinternational.isijint-2018-160 ◽

2018 ◽

Vol 58 (9) ◽

pp. 1687-1694

Author(s):

Xiaowei Zhu ◽

Dewei Li ◽

Chunlei Wu ◽

Tretiak Oleksandr ◽

Qiang Wang

Keyword(s):

Flow Field ◽

Large Scale ◽

Recirculation Zone ◽

Large Scale Vortex ◽

Vortex Movement

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Experimental and Numerical Study of Swirling Flows and Flame Dynamics

Latvian Journal of Physics and Technical Sciences ◽

10.2478/lpts-2014-0021 ◽

2014 ◽

Vol 51 (4) ◽

pp. 25-40 ◽

Cited By ~ 1

Author(s):

M. Abricka ◽

I. Barmina ◽

R. Valdmanis ◽

M. Zake

Keyword(s):

Recirculation Zone ◽

Swirling Flow ◽

Numerical Study ◽

Chemical Conversion ◽

Reacting Flows ◽

Flow Dynamics ◽

Combustion Stability ◽

Complex Flow ◽

Air Jet ◽

Air Supply

Abstract The effect of swirling air on the flow dynamics was investigated for the cold non-reacting flows and the flame arising at thermo-chemical conversion of biomass pellets downstream of a cylindrical channel. Under experimental and numerical investigation was the swirling flow dynamics with the primary axial air supply below a biomass layer and swirling air supply above it. The results indicate that for cold flows the swirling air jet outflow from tangential nozzles leads to the formation of a complex flow dynamics which is influenced both by upstream and downstream air swirl propagation near the channel walls, with correlating swirl-enhanced formation of the upstream and downstream axial flows close to the flow centreline depending on the swirling air supply rate. These axial flows can be completely balanced at their stagnation within the axial recirculation zone. It is shown that at equal boundary conditions for the swirling flame and the cold flows the swirling flow dynamics is influenced by the upstream air swirl-enhanced mixing of the reactants below the air swirl nozzles. This determines the formation of a downstream reaction zone with correlating development of the flow velocity, temperature and composition profiles in the downstream flame regions with improved combustion stability. The low swirl intensity in these regions prevents the formation of a recirculation zone

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Optimized Design of a Swirler for a Combustion Chamber of Non-Premixed Flame Using Genetic Algorithms

Energies ◽

10.3390/en13092240 ◽

2020 ◽

Vol 13 (9) ◽

pp. 2240

Author(s):

Daniel Alejandro Zavaleta-Luna ◽

Marco Osvaldo Vigueras-Zúñiga ◽

Agustín L. Herrera-May ◽

Sergio Aurelio Zamora-Castro ◽

María Elena Tejeda-del-Cueto

Keyword(s):

Genetic Algorithms ◽

Combustion Chamber ◽

High Intensity ◽

Recirculation Zone ◽

Swirling Flow ◽

Mixture Fraction ◽

Premixed Flame ◽

Optimized Design ◽

Combustion Chambers ◽

Cfd Models

Recirculation in a combustion chamber is required for stabilizing the flame and reducing pollutants. The swirlers can generate recirculation in a combustion chamber, inducing a swirling flow that breaks vorticity and improves the mixing of air and fuel. The swirl number (Sn) is related to the formation of recirculation in conditions of high-intensity flows with Sn > 0.6. Thus, the optimized design of a swirler is necessary to generate enough turbulence that keeps the flame stable. We present the optimized design of a swirler considering the main parameters for a non-premixed combustion chamber. This optimization is made with genetic algorithms to ensure the generation of a recirculation zone in the combustion chamber. This recirculation phenomenon is simulated using computational fluid dynamics (CFD) models and applying the renormalization group (RNG) k-ε turbulence method. The chemistry is parameterized as a function of the mixture fraction and dissipation rate. A CFD comparison of a baseline swirler model and the proposed optimized swirler model shows that a recirculation zone with high intensity and longer length is generated in the primary zone of the combustion chamber when the optimized model is used. Furthermore, the CFD models depict swirling effects in the turbulent non-premixed flame, in which the stabilization is sensitive to the recirculation zone. The temperature results obtained with the CFD models agree well with the experimental results. The proposed design can help designers enhance the performance of combustion chambers and decrease the generation of CO and NOx.

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Large eddy simulation study of flow field characteristics of a combustor with two coaxial swirlers

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650919870420 ◽

2019 ◽

Vol 234 (5) ◽

pp. 625-642

Author(s):

Qun Zhang ◽

Peng Zhang ◽

Shun-li Sun ◽

Ya-heng Song ◽

Yi-fei Li ◽

...

Keyword(s):

Flow Field ◽

Proper Orthogonal Decomposition ◽

Vortex Core ◽

Large Scale ◽

Recirculation Zone ◽

Swirling Flow ◽

Orthogonal Decomposition ◽

Eddy Simulation ◽

Large Eddy ◽

Proper Orthogonal

The cold and reaction flow fields of a combustor with two coaxial swirlers are investigated by means of large eddy simulation. Effective data processing methods such as proper orthogonal decomposition and fast Fourier transform are employed for analysis. The complex flow phenomena such as swirling jet, shear layer, recirculation zone, and precession vortex core are observed and their characteristics are analyzed. The dynamics of the flame and its interactions with the complex swirling flows and large-scale eddies are characterized. The precession vortex core structures and its influences on the combustion process are emphatically explored. It is found that the outer shear layer produces spiral precession vortex core cantilever structures and the change of structural characteristics of the PVC determines the pressure pulsation frequency of the combustor. The results also indicate precession vortex core accelerates the mixing of unburned and burned mixture, leading to the ignition. The principal structures are studied by determining the highest energy modes via proper orthogonal decomposition. The modes are classified according to energy size. By means of proper orthogonal decomposition four-decomposition method, the vortexes of different energy and scales in swirling flow field are classified and analyzed in detail, the flow field is reconstructed, and the large-scale coherent structures and small energy flow structures are obtained. A spectral map of the turbulent kinetic energy density exhibits the −5/3 slope given by the Kolmogorov–Obukhov law. Based on the analysis of the vortex structures and their evolution, and the analysis of the transports and distributions of flow field characteristic parameters, a novel unsteady swirling flow combustion organization mechanism is proposed. It is found that combustion mainly occurs in low-energy small-scale vortexes, releasing a large amount of heat. High-temperature gas enters the recirculation zone and continues to provide energy for the precession vortex cores.

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ON IMPACT OF LARGE-SCALE VORTEX STRUCTURES ON FLAME SHAPE IN A SWIRLING JET FLOW

Gorenie i vzryv (Moskva) — Combustion and Explosion ◽

10.30826/ce18110205 ◽

2018 ◽

Vol 11 (2) ◽

pp. 31-39

Author(s):

L. М. Chikishev ◽

◽

V. М. Dulin ◽

A. S. Lobasov ◽

D. М. Markovich ◽

...

Keyword(s):

Large Scale ◽

Jet Flow ◽

Vortex Structures ◽

Swirling Jet ◽

Large Scale Vortex ◽

Flame Shape

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Experimental Study on Backflow Patterns Induced by a Bilateral Groin Pair with Different Spacing

Applied Sciences ◽

10.3390/app11041486 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1486

Author(s):

Cuiping Kuang ◽

Yuhua Zheng ◽

Jie Gu ◽

Qingping Zou ◽

Xuejian Han

Keyword(s):

Cross Sections ◽

Large Scale ◽

Recirculation Zone ◽

Flow Direction ◽

Wake Flow ◽

Zone Length ◽

Array Configuration ◽

Contraction Ratio ◽

River Training ◽

Spanwise Velocity

Groins are one of the popular manmade structures to modify the hydraulic flow and sediment response in river training. The spacing between groins is a critical consideration to balance the channel-depth and the cost of construction, which is generally determined by the backflow formed downstream from groins. A series of experiments were conducted using Particle Image Velocimetry (PIV) to observe the influence of groin spacing on the backflow pattern of two bilateral groins. The spacing between groins has significant effect on the behavior of the large-scale recirculation cell behind groins. The magnitude of the wake flow induced by a groin was similar to that induced by another groin on the other side, but the flow direction is opposite. The spanwise velocity near the groin tip dictates the recirculation zone width behind the groins due to the strong links between the spanwise velocity and the contraction ratio of channel cross-sections between groins. Based on previous studies and present experimental results, quantitative empirical relationships are proposed to calculate the recirculation zone length behind groins alternately placed at different spacing along riverbanks. This study provides better understanding and a robust formula to assess the backflow extent of alternate groins and identify the optimum groins array configuration.

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Unsteady Three-Dimensional Analysis of Inlet Distortion in a Transonic Fan

Fluids Engineering ◽

10.1115/imece2006-13145 ◽

2006 ◽

Author(s):

Peng Sun ◽

Guotal Feng

Keyword(s):

Shock Wave ◽

Total Pressure ◽

Large Scale ◽

Three Dimensional ◽

Navier Stokes ◽

Inlet Distortion ◽

Flow Loss ◽

Large Scale Vortex ◽

Total Temperature ◽

Transonic Fan

A time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan was carried out using "Fluent-parallel" in a parallel supercomputer. The numerical simulation focused on a transonic fan with inlet square wave total pressure distortion and the analysis of result consisted of three aspects. The first was about inlet parameters redistribution and outlet total temperature distortion induced by inlet total pressure distortion. The pattern and causation of flow loss caused by pressure distortion in rotor were analyzed secondly. It was found that the influence of distortion was different at different radial positions. In hub area, transportation-loss and mixing-loss were the main loss patterns. Distortion not only complicated them but enhanced them. Especially in stator, inlet total pressure distortion induced large-scale vortex, which produced backflow and increased the loss. While in casing area, distortion changed the format of shock wave and increased the shock loss. Finally, the format of shock wave and the hysteresis of rotor to distortion were analyzed in detail.

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