Large eddy simulation of the influence of synthetic inlet turbulence on a practical aeroengine combustor with counter-rotating swirler

2017 ◽  
Vol 233 (3) ◽  
pp. 978-990 ◽  
Author(s):  
Yu Zhou ◽  
Yuan Huang ◽  
Zhongqiang Mu
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Reverse Flow ◽  
Boundary Layer Transition ◽  
Wall Region ◽  
Inlet Condition ◽  
Eddy Simulation ◽  
Large Eddy

To study the influence of inlet turbulence on the prediction of flow structure in practical aeroengine combustor, large eddy simulation with dynamic Smagorinsky subgrid model is used to explore the complex unsteady flow field in a single burner of a typical aeroengine combustor with two-stage counter-rotating swirler. The complex geometric configuration including all film cooling holes is fully simulated without any conventional simplification in order to reduce the modeling errors. First, unsteady process that flow developing from static to statistically stationary state is fully simulated under laminar inlet condition to obtain a fundamental understanding of flow characteristics in the combustor. Afterwards, synthetic eddy method is utilized to generate a turbulent inlet condition so that a perturbation with about 5% turbulence intensity is superimposed to the inlet plane. Simulation result shows that for the laminar inflow case, flow separation occurs in the near-wall region of the diffusion section, inducing a boundary layer transition and consequently introducing turbulence with nonuniformity in space before the swirler. In contrast, synthesized inflow generated under turbulent inlet condition by synthetic eddy method is more spatially homogeneous. Time-averaged flow field inside the swirler cup reveals that turbulent inflow ultimately causes the swirling flow with higher rotating speed in central region and more uniform distribution along the circumferential direction. It also enhances the transverse jet flow from primary holes and reverse flow in the central recirculation zone, and makes streamlines corresponding to the recirculation vortices more symmetrical on central profile. Maximum recirculating velocity predicted in central recirculation zone is −27.65 m/s and −17.86 m/s in turbulent and laminar case respectively, and corresponding total pressure recovery coefficient is 96.03% and 96.81%.

Spectral Analysis of an Aeronautical Lean Direct Injection Burner Through Large Eddy Simulation

2020 ◽  
Author(s):  
M. Carreres ◽  
L. M. García-Cuevas ◽  
J. García-Tíscar ◽  
M. Belmar-Gil
Keyword(s):  
Experimental Data ◽  
Spectral Analysis ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Swirling Flow ◽  
Direct Injection ◽  
Flow Structures ◽  
Lean Direct Injection ◽  
Eddy Simulation ◽  
Large Eddy

Abstract During the last decades, many efforts have been invested by the scientific community in minimising exhaust emissions from aeronautical gas turbine engines. In this context, many advanced ultra-low NOx combustion concepts, such as the Lean Direct Injection treated in the present study, are being developed to abide by future regulations. Numerical simulations of these devices are usually computationally expensive since they imply a multi-scale problem. In this work, a non-reactive Large Eddy Simulation of a gaseous-fuelled, radial-swirled Lean-Direct Injection (LDI) combustor has been carried out through the OpenFOAM Computational Fluid Dynamics (CFD) code by solving the complete inlet flow path through the swirl vanes and the combustor. The geometry considered is the gaseous configuration of the CORIA LDI combustor, for which detailed measurements are available. Macroscopical analysis of the main turbulent features related to the swirling flow and the generated Central Recirculation Zone (CRZ) are well established in the literature. Nevertheless, a more in-depth characterization is still required in this area of active research since theory and experimental data are not yet able to predict which unstable mode dominates the flow. This work aims at using Large Eddy Simulation for a complete characterisation of the unsteady flow structures generated within the combustion chamber of a gaseous methane injection immersed in a strong non-reactive swirling flow field. To do so, a spectral analysis of the flow field is performed to identify the frequency, intensity and instabilities associated to the phenomena occurring at the swirler outlet region. A coherent structure known as Precessing Vortex Core (PVC) is identified both at the inner and the outer shear layers, resulting in a periodic disturbance of the pressure and velocity fields. The pressure and velocity fluctuations predicted by the CFD code are used to compute the spectral signatures through the Sound Pressure Level (SPL) amplitude at multiple locations. This allows investigating both the complex behaviour of the PVC and its associated acoustic phenomena. The acoustic characteristics computed by the numerical model are first validated qualitatively by comparing the spectrum with available experimental data. In this way, the use of dimensionless numbers to characterise the most energetic structures is coherent with the experimental observations and the characteristics of the PVC. Then, the numerical identification of the main acoustic modes in the chamber through Dynamic Mode Decomposition (DMD) allows overcoming the Fast Fourier Transform (FFT) shortcomings and better understanding the propagation of the hydrodynamic instability perturbations. This investigation on the main non-reacting swirling flow structures inside the combustor provides a suitable background for further studies on combustion instability mechanisms.

Impact of Swirl Flow on Combustor Liner Heat Transfer and Cooling: A Numerical Investigation With Hybrid Reynolds-Averaged Navier–Stokes Large Eddy Simulation Models

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Lorenzo Mazzei ◽  
Antonio Andreini ◽  
Bruno Facchini ◽  
Fabio Turrini
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Numerical Investigation ◽  
Swirling Flow ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes ◽  
Combustor Liner

This paper reports the main findings of a numerical investigation aimed at characterizing the flow field and the wall heat transfer resulting from the interaction of a swirling flow provided by lean-burn injectors and a slot cooling system, which generates film cooling in the first part of the combustor liner. In order to overcome some well-known limitations of Reynolds-averaged Navier–Stokes (RANS) approach, e.g., the underestimation of mixing, the simulations were performed with hybrid RANS–large eddy simulation (LES) models, namely, scale-adaptive simulation (SAS)–shear stress transport (SST) and detached eddy simulation (DES)–SST, which are proving to be a viable approach to resolve the main structures of the flow field. The numerical results were compared to experimental data obtained on a nonreactive three-sector planar rig developed in the context of the EU project LEMCOTEC. The analysis of the flow field has highlighted a generally good agreement against particle image velocimetry (PIV) measurements, especially for the SAS–SST model, whereas DES–SST returns some discrepancies in the opening angle of the swirling flow, altering the location of the corner vortex. Also the assessment in terms of Nu/Nu0 distribution confirms the overall accuracy of SAS–SST, where a constant overprediction in the magnitude of the heat transfer is shown by DES–SST, even though potential improvements with mesh refinement are pointed out.

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

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.

Large Eddy Simulation of Flow and Heat Transfer Mechanism in Matrix Cooling Channel

2017 ◽  
Author(s):  
Yigang Luan ◽  
Lianfeng Yang ◽  
Bo Wan ◽  
Tao Sun
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Gas Turbine ◽  
Transfer Mechanism ◽  
Heat Transfer Mechanism ◽  
Longitudinal Vortices ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Gas turbine engines have been widely used in modern industry especially in the aviation, marine and energy fields. The efficiency of gas turbines directly affects the economy and emissions. It’s acknowledged that the higher turbine inlet temperatures contribute to the overall gas turbine engine efficiency. Since the components are subject to the heat load, the internal cooling technology of turbine blades is of vital importance to ensure the safe and normal operation. This paper is focused on exploring the flow and heat transfer mechanism in matrix cooling channels. In order to analyze the internal flow field characteristics of this cooling configuration at a Reynolds number of 30000 accurately, large eddy simulation method is carried out. Methods of vortex identification and field synergy are employed to study its flow field. Cross-sectional views of velocity in three subchannels at different positions have been presented. The results show that the airflow is strongly disturbed by the bending part. It’s concluded that due to the bending structure, the airflow becomes complex and disordered. When the airflow goes from the inlet to the turning, some small-sized and discontinuous vortices are formed. Behind the bending structure, the size of the vortices becomes big and the vortices fill the subchannels. Because of the structure of latticework, the airflow is affected by each other. Airflow in one subchannel can exert a shear force on another airflow in the opposite subchannel. It’s the force whose direction is the same as the vortex that enhances the longitudinal vortices. And the longitudinal vortices contribute to the energy exchange of the internal airflow and the heat transfer between airflow and walls. Besides, a comparison of the CFD results and the experimental data is made to prove that the numerical simulation methods are reasonable and acceptable.

Large Eddy Simulation of the Vortex End in Reverse-Flow Centrifugal Separators

2009 ◽  
Author(s):  
Gleb I. Pisarev ◽  
Alex C. Hoffmann ◽  
Weiming Peng ◽  
Henk A. Dijkstra ◽  
Theodore E. Simos ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Reverse Flow ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Investigation of the velocity field downstream of a benchmark vent using numerical simulation and hot-wire anemometry

2019 ◽  
Vol 213 ◽  
pp. 02076
Author(s):  
Jan Sip ◽  
Frantisek Lizal ◽  
Jakub Elcner ◽  
Jan Pokorny ◽  
Miroslav Jicha
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Velocity Field ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulence Models ◽  
Hot Wire ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Precise Prediction

The velocity field in the area behind the automotive vent was measured by hot-wire anenemometry in detail and intensity of turbulence was calculated. Numerical simulation of the same flow field was performed using Computational fluid dynamics in commecial software STAR-CCM+. Several turbulence models were tested and compared with Large Eddy Simulation. The influence of turbulence model on the results of air flow from the vent was investigated. The comparison of simulations and experimental results showed that most precise prediction of flow field was provided by Spalart-Allmaras model. Large eddy simulation did not provide results in quality that would compensate for the increased computing cost.

scholarly journals Large eddy simulation of turbulent channel flow using differential equation wall model

2018 ◽  
Vol 15 (2) ◽  
pp. 75-89
Author(s):  
Muhammad Saiful Islam Mallik ◽  
Md. Ashraf Uddin
Keyword(s):  
Differential Equation ◽  
Flow Field ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Wall Region ◽  
Computational Domain ◽  
Wall Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Near Wall

A large eddy simulation (LES) of a plane turbulent channel flow is performed at a Reynolds number Re? = 590 based on the channel half width, ? and wall shear velocity, u? by approximating the near wall region using differential equation wall model (DEWM). The simulation is performed in a computational domain of 2?? x 2? x ??. The computational domain is discretized by staggered grid system with 32 x 30 x 32 grid points. In this domain the governing equations of LES are discretized spatially by second order finite difference formulation, and for temporal discretization the third order low-storage Runge-Kutta method is used. Essential turbulence statistics of the computed flow field based on this LES approach are calculated and compared with the available Direct Numerical Simulation (DNS) and LES data where no wall model was used. Comparing the results throughout the calculation domain we have found that the LES results based on DEWM show closer agreement with the DNS data, especially at the near wall region. That is, the LES approach based on DEWM can capture the effects of near wall structures more accurately. Flow structures in the computed flow field in the 3D turbulent channel have also been discussed and compared with LES data using no wall model.

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