CFD-Analysis of the Combustion in the Primary Stage of a Two-Stage Combustion Chamber

2002 ◽  
Author(s):  
Klaus Hoerzer ◽  
Hermann Haselbacher ◽  
Anthony J. Griffiths ◽  
Nick Syred ◽  
Thomas A. Fraser
Keyword(s):  
Combustion Chamber ◽  
Mixture Fraction ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Reynolds Stress Model ◽  
Swirl Flow ◽  
Wood Powder ◽  
Two Stage ◽  
Primary Stage ◽  
Combustion Flow

Combustion of wood powder may be applied in a two-stage multi-inlet combustion chamber. The primary stage of the combustion chamber has tangential air inlets to provide high swirl flow. The wood powder and its conveying air enter the gasification chamber axially through a center inlet in the bottom. The aim of the investigation was the analysis of the combustion flow of the primary stage of the combustion chamber. The calculation grid was three-dimensional and unstructured. Turbulence was modelled with the Reynolds-Stress-Model, species with mixture fraction/pdf-approach, radiation with the P1-model. Postprocessing has been done for particle tracks, the temperature distribution and tangential velocity distribution and for the species distributions of solid carbon, carbon monoxide, carbon dioxide and oxygen as well.

Effect of Pitch Chord Ratio and Side Wall Expansion Angle on Flow Through Vane Swirlers

2006 ◽  
Author(s):  
R. Thundil Karuppa Raj ◽  
V. Ganesan
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Side Wall ◽  
Reynolds Stress Model ◽  
Swirl Flow ◽  
Expansion Angle ◽  
Turbulence Effects ◽  
Flow Field Characteristics ◽  
Flow Through

This paper is concerned with the computational study of steady flow through the vane swirlers. Swirl flow field characteristics for various pitch chord ratio (s/c) at swirler mean radius are studied for a 45° vane swirler under both sudden and gradual expansions with side-wall expansion angles of 90° and 45° respectively. In the computational study the geometry and meshing is done using pre-processor GAMBIT. Three-dimensional flow within the geometry and through the swirler has been simulated by solving the appropriate governing equations viz. conservation of mass and momentum using FLUENT code. Turbulence effects are taken care of by the Reynolds stress model and shear stress transport k-ω model for high swirls and standard k-ε model for low and medium swirls. The effect of pitch to chord ratio (s/c) on flow characteristics have been studied. The predicted results are validated with the experimental data available in the literature for s/c ratio of 1. The numerical results of axial velocity profiles downstream of the swirler at various axial planes are found to be in close agreement with the experimental results. It is found that the s/c ratio of 1 provides good turning efficiency.

Numerical Study of Nonreacting Gas Turbine Combustor Swirl Flow Using Reynolds Stress Model

2003 ◽  
Vol 125 (3) ◽  
pp. 804-811 ◽  
Author(s):  
S. L. Yang ◽  
Y. K. Siow ◽  
B. D. Peschke ◽  
R. R. Tacina
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Reynolds Stress Model ◽  
Swirl Flow ◽  
High Degree

This paper presents recent research on the use of a Reynolds stress turbulence model (RSTM) for three-dimensional flowfield simulation inside gas turbine combustors. It intends to show the motivations for using the RSTM in engine flow simulation, to present a further validation of the RSTM implementation in the KIVA code using the available experimental data, and to provide comparisons between RSTM and k-ε turbulence model results for chemically nonreacting swirling flows. The results show that, for high-degree swirl flow, the RSTM can provide predictions in favorable agreement with the experimental data, and that the RSTM predicts recirculations and high velocity gradients better than does the k-ε turbulence model. The results also indicate that the choice of swirler has a significant influence on the structure of the combustor flowfield.

scholarly journals The Numerical Analysis of the Flow on the Smooth and Nonsmooth Boundaries by IBEM/DBIEM

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Gang Xu ◽  
Guangwei Zhao ◽  
Jing Chen ◽  
Shuqi Wang ◽  
Weichao Shi
Keyword(s):  
Boundary Value ◽  
Three Dimensional ◽  
Boundary Surface ◽  
Tangential Velocity ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Surface Shape ◽  
Normal Vector ◽  
Computational Domain ◽  
Nonsmooth Boundary

The value of the tangential velocity on the Boundary Value Problem (BVP) is inaccurate when comparing the results with analytical solutions by Indirect Boundary Element Method (IBEM), especially at the intersection region where the normal vector is changing rapidly (named nonsmooth boundary). In this study, the singularity of the BVP, which is directly arranged in the center of the surface of the fluid computing domain, is moved outside the computational domain by using the Desingularized Boundary Integral Equation Method (DBIEM). In order to analyze the accuracy of the IBEM/DBIEM and validate the above-mentioned problem, three-dimensional uniform flow over a sphere has been presented. The convergent study of the presented model has been investigated, including desingularized distance in the DBIEM. Then, the numerical results were compared with the analytical solution. It was found that the accuracy of velocity distribution in the flow field has been greatly improved at the intersection region, which has suddenly changed the boundary surface shape of the fluid domain. The conclusions can guide the study on the flow over nonsmooth boundaries by using boundary value method.

Effect of the Separating Distance of Twin Buildings on the Generated Flow Structure

2010 ◽  
Vol 297-301 ◽  
pp. 924-929
Author(s):  
Inès Bhouri Baouab ◽  
Nejla Mahjoub Said ◽  
Hatem Mhiri ◽  
Georges Le Palec ◽  
Philippe Bournot
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Wind Flow ◽  
Turbulent Model ◽  
Navier Stokes Equations ◽  
Twin Buildings ◽  
Volume Method ◽  
Numerical Examination

The present work consists in a numerical examination of the dispersion of pollutants discharged from a bent chimney and crossing twin similar cubic obstacles placed in the lee side of the source. The resulting flow is assumed to be steady, three-dimensional and turbulent. Its modelling is based upon the resolution of the Navier Stokes equations by means of the finite volume method together with the RSM (Reynolds Stress Model) turbulent model. This examination aims essentially at detailing the wind flow perturbations, the recirculation and turbulence generated by the presence of the twin cubic obstacles placed tandem at different spacing distances (gaps): W = 4 h, W = 2 h and W = 1 h where W is the distance separating both buildings.

Swirl Flow Investigations on the Enhancement of Heat Transfer Processes in Cyclone Cooling Ducts

2012 ◽  
Author(s):  
Florian Wassermann ◽  
Sven Grundmann ◽  
Michael Kloss ◽  
Heinz-Peter Schiffer
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Complex Structure ◽  
Three Dimensional ◽  
Swirl Flow ◽  
Flow Structures ◽  
Stable Complex ◽  
Reynolds Analogy ◽  
Transfer Processes ◽  
Cooling Ducts

Cyclone cooling is a promising method to enhance heat-transfer processes in future internal turbine-blade leading-edge cooling-ducts. The basic component of such cooling channels is the swirl generator, which induces a swirling movement of the coolant. The angular momentum generates stable, complex and three-dimensional flow structures of helical shape with alternating axial flow directions. Full three-dimensional and three-component velocity measurements using magnetic resonance velocimetry (3D3C-MRV) were conducted, with the aim to understand the complex structure of pipe flows with strong swirl. In order to mimic the effect of different installation concepts of the cyclone-cooling ducts an idealized bend-duct swirl-tube configuration with variable exit orifices has been investigated. Pronounced helical flow structures and distinct velocity zones could be found in this swirl flow. One substantial result is the identification of stationary helix-shaped streaks of high axial velocity in the direct vicinity of the wall. These findings are in good agreement with mass-transfer measurements that also show helix-shaped structures with increased mass transfer at the inner surface of the tube. According to the Reynolds analogy between heat and mass transfer, augmented heat-transfer processes in these areas are to be expected.

Design Analysis of a Micro Gas Turbine Combustion Chamber Burning Natural Gas

2012 ◽  
Author(s):  
André Perpignan V. de Campos ◽  
Fernando L. Sacomano Filho ◽  
Guenther C. Krieger Filho
Keyword(s):  
Experimental Data ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Gas Turbines ◽  
Low Cost ◽  
Mixture Fraction ◽  
Combustion Model ◽  
Inlet Temperature ◽  
Gas Combustion ◽  
Micro Turbine

Gas turbines are reliable energy conversion systems since they are able to operate with variable fuels and independently from seasonal natural changes. Within that reality, micro gas turbines have been increasing the importance of its usage on the onsite generation. Comparatively, less research has been done, leaving more room for improvements in this class of gas turbines. Focusing on the study of a flexible micro turbine set, this work is part of the development of a low cost electric generation micro turbine, which is capable of burning natural gas, LPG and ethanol. It is composed of an originally automotive turbocompressor, a combustion chamber specifically designed for this application, as well as a single stage axial power turbine. The combustion chamber is a reversed flow type and has a swirl stabilized combustor. This paper is dedicated to the diagnosis of the natural gas combustion in this chamber using computational fluid dynamics techniques compared to measured experimental data of temperature inside the combustion chamber. The study emphasizes the near inner wall temperature, turbine inlet temperature and dilution holes effectiveness. The calculation was conducted with the Reynolds Stress turbulence model coupled with the conventional β-PDF equilibrium along with mixture fraction transport combustion model. Thermal radiation was also considered. Reasonable agreement between experimental data and computational simulations was achieved, providing confidence on the phenomena observed on the simulations, which enabled the design improvement suggestions and analysis included in this work.

Vortex formation on surging aerofoils with application to reverse flow modelling

2018 ◽  
Vol 859 ◽  
pp. 59-88 ◽  
Author(s):  
Philip B. Kirk ◽  
Anya R. Jones
Keyword(s):  
Surface Pressure ◽  
Reverse Flow ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Leading Edge ◽  
Field Measurements ◽  
Reduced Frequency ◽  
Advance Ratio ◽  
Convection Speed

The leading-edge vortex (LEV) is a powerful unsteady flow structure that can result in significant unsteady loads on lifting blades and wings. Using force, surface pressure and flow field measurements, this work represents an experimental campaign to characterize LEV behaviour in sinusoidally surging flows with widely varying amplitudes and frequencies. Additional tests were conducted in reverse flow surge, with kinematics similar to the tangential velocity profile seen by a blade element in recent high-advance-ratio rotor experiments. General results demonstrate the variability of LEV convection properties with reduced frequency, which greatly affected the average lift-to-drag ratio in a cycle. Analysis of surface pressure measurements suggests that LEV convection speed is a function only of the local instantaneous flow velocity. In the rotor-comparison tests, LEVs formed in reverse flow surge were found to convect more quickly than the corresponding reverse flow LEVs that form on a high-advance-ratio rotor, demonstrating that rotary motion has a stabilizing effect on LEVs. The reverse flow surging LEVs were also found to be of comparable strength to those observed on the high-advance-ratio rotor, leading to the conclusion that a surging-wing simplification might provide a suitable basis for low-order models of much more complex three-dimensional flows.

Investigation on a two-stage platform of large stroke for broadband vertical vibration isolation

2018 ◽  
Vol 25 (6) ◽  
pp. 1233-1245 ◽  
Author(s):  
Xiling Xie ◽  
Mingke Ren ◽  
Hongbo Zheng ◽  
Zhiyi Zhang
Keyword(s):  
Vibration Isolation ◽  
Vertical Vibration ◽  
Optical Switches ◽  
Static Properties ◽  
Two Stage ◽  
Maximum Displacement ◽  
Primary Stage ◽  
Low Frequencies ◽  
Attenuation Rate ◽  
Secondary Stage

For the purpose of preventing vibration-sensitive optical switches from malfunction caused by broadband vertical vibration, a novel two-stage vibration isolation platform is proposed. The primary stage is a bellows-type isolator of large stroke and low isolation frequency, and the secondary stage is a small-stroke hybrid isolator composed of bellows and voice-coil actuators. In the primary stage, two pre-compressed horizontal bellows and one vertical bellows are used to counter the weight of the switch and to reduce the total height of the isolator. The static properties of the primary stage are analyzed, and the vibration isolation of the platform is investigated. Numerical results indicate that the two-stage platform is effective in isolating vertical vibration. Experiments are also conducted to verify the performance of the platform. It is exhibited that the transmissibility is less than 0 dB over 2 Hz, and the attenuation rate reaches −35 dB/dec at high frequencies. The frequency range of test is 2–200 Hz, and the maximum displacement is 10 mm at 2 Hz. In the secondary stage, the actuators can substantially suppress the resonance peak, and promote isolation performance at low frequencies.

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