The suitability of different swirl number definitions for describing swirl flows: Accurate, common and (over-) simplified formulations

2022 ◽  
Vol 89 ◽  
pp. 100969
Author(s):  
Guillaume Vignat ◽  
Daniel Durox ◽  
Sébastien Candel
Keyword(s):  
Swirl Number ◽  
Swirl Flows

Numerical Study of Vortex Evolution and Correlation between Twin Swirling Flows

2012 ◽  
Vol 516-517 ◽  
pp. 976-979 ◽  
Author(s):  
Nan Gui
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Numerical Study ◽  
Swirling Flows ◽  
Cyclone Separator ◽  
Velocity Correlation ◽  
Swirl Number ◽  
Swirling Jets ◽  
Swirl Flows ◽  
Energy Engineering

Swirling flows are widely used in energy engineering, such as swirling combustor, cyclone separator in pulverized coal burners. The vortex evolution and correlation between twin swirling flows are investigated via direct numerical simulation. Three typical swirl flows with different swirl number are simulated. The structure of vortex evolution, velocity correlation between the twin flows are illustrated and analyzed in detail. The results show the phase-locked correlation of flow velocity between the twin swirling jets which would be useful and helpful for improving the understanding of aerodynamics of multi-swirling systems.

scholarly journals Influential parameters of nitrogen oxides emissions for microturbine swirl burner with pilot burner

2010 ◽  
Vol 64 (4) ◽  
pp. 357-363 ◽  
Author(s):  
Miroljub Adzic ◽  
Marija Zivkovic ◽  
Vasko Fotev ◽  
Aleksandar Milivojevic ◽  
Vuk Adzic
Keyword(s):  
Thermal Power ◽  
High Energy ◽  
Nox Emission ◽  
Swirl Number ◽  
Main Burner ◽  
Swirl Flows ◽  
Wide Range ◽  
Micro Turbine ◽  
Influential Parameters ◽  
Pilot Burner

Swirl burners are the most common type of device in wide range of applications, including gas turbine combustors. Due to their characteristics, swirl flows are extensively used in combustion systems because they enable high energy conversion in small volume with good stabilization behavior over the wide operating range. The flow and mixing process generated by the swirl afford excellent flame stability and reduced NOx emissions. Experimental investigation of NOx emission of a purposely designed micro turbine gas burner with pilot burner is presented. Both burners are equipped with swirlers. Mixtures of air and fuel are introduced separately: through the inner swirler - primary mixture for pilot burner, and through the outer swirler - secondary mixture for main burner. The effects of swirl number variations for the both burners were investigated, including parametric variations of the thermal power and air coefficient. It was found that the outer swirler affects the emission of NOx only for the air coefficient less than 1.4. The increase of swirl number resulted in decrease of NOx emission. The inner swirler and thermal power were found to have negligible effect on emission.

Computed Effects of Rotor-Induced Swirl on Brush Seal Performance—Part 2: Bristle Force Analysis

1996 ◽  
Vol 118 (4) ◽  
pp. 920-926 ◽  
Author(s):  
M. C. Sharatchandra ◽  
D. L. Rhode
Keyword(s):  
Inclination Angle ◽  
Flow Direction ◽  
Flow Simulation ◽  
Companion Paper ◽  
Navier Stokes ◽  
Brush Seal ◽  
Swirl Flows ◽  
Lift Off ◽  
Square Configuration ◽  
Periodic Module

This paper analytically investigates the aerodynamic bristle force distributions in brush seals used in aircraft gas turbine engines. These forces are responsible for the onset of bristle tip lift-off from the rotor surface which significantly affects brush seal performance. In order to provide an enhanced understanding of the mechanisms governing the bristle force distributions, a full Navier-Stokes flow simulation is performed in a streamwise periodic module of bristles corresponding to the staggered square configuration. As is the case with a companion paper (Sharatchandra and Rhode, 1996), this study has the novel feature of considering the combined effects of axial (leakage) and tangential (swirl) flows. Specifically, the effects of intra-bristle spacing and bristle inclination angle are explored. The results indicate that the lifting bristle force increases with reduced intra-bristle spacing and increased inclination angle. It was also observed that increases in the axial or tangential flow rates increased the force component in the normal as well as the flow direction.

Investigations into the Precessing Vortex Core Phenomenon in Cyclone Dust Separators

1994 ◽  
Vol 208 (2) ◽  
pp. 147-154 ◽  
Author(s):  
P Yazdabadi ◽  
A J Griffiths ◽  
N Syred
Keyword(s):  
Vortex Core ◽  
Reynolds Numbers ◽  
Frequency Parameter ◽  
Experimental Investigations ◽  
Swirl Number ◽  
Significant Drop ◽  
Precessing Vortex Core ◽  
Dust Separator ◽  
The Relationship

Experimental investigations have been carried out to examine the effect of downstream pipework configurations on the precessing vortex core (PVC) generated within the exhaust region of a cyclone dust separator. Characterization of the PVC using a non-dimensionalized frequency parameter (NDFP) was used to determine the relationship between Reynolds number and geometrical swirl number of the cyclone. The results show that the NDFP tends towards an asymptotic value for Reynolds numbers of about 50 000 and high swirl numbers (> 3.043). This value is reached earlier with lower swirl numbers. It was concluded that any exhaust pipework configuration produced a significant drop in the PVC frequency, and certain configurations either delayed or promoted the development of the PVC.

Topological Flow Structures of Annular Swirling Jets

2001 ◽  
Vol 17 (3) ◽  
pp. 131-138
Author(s):  
Feng Chin Tsai ◽  
Rong Fung Huang
Keyword(s):  
Vortex Breakdown ◽  
Swirling Flow ◽  
Single Bubble ◽  
Flow Structures ◽  
Complex Flow ◽  
Swirl Number ◽  
Recirculation Bubble ◽  
Annular Jet ◽  
Ring Mode ◽  
Dual Ring

AbstractThe effects of blockage and swirl on the macro flow structures of the annular jet past a circular disc are experimentally studied through the time-averaged streamline patterns. In the blockage-effect regime, the flows present multiple modes, single bubble, dual rings, vortex breakdown, and triple rings, in different regimes of blockage ratio and swirl number. The topological models of the flow structures are proposed and discussed according to the measured flow fields to manifest the complex flow structures. The single bubble is a closed recirculation bubble with a stagnation point on the central axis. The dual-ring flow is an open-top recirculsation zone, in which a pair of counter-rotating vortex rings exists in the near wake. The fluids in the dual rings are expelled downstream through a central jet-like swirling flow. A vortex breakdown may occur in the central jet-like swirling flow if the exit swirl number exceeds critical values. When the vortex breakdown interacts with the dual rings, a complex triple-ring flow structure forms. Axial distributions of the local swirl number are presented and discussed. The local swirl number increases with the increase of the exit swirl number and attains the maximum in the dual-ring mode. At large exit swirl numbers where the vortex breakdown occurs, the local swirl number decreases drastically to a low value.

A Perspective on Combustion-Driven Flows With Circulation

2001 ◽  
Author(s):  
Francine Battaglia ◽  
Ronald G. Rehm ◽  
Howard R. Baum ◽  
Mohamed I. Hassan ◽  
Kozo Saito
Keyword(s):  
Reynolds Number ◽  
Froude Number ◽  
Theoretical Studies ◽  
Swirl Number ◽  
Dimensionless Parameters ◽  
Parametric Investigation ◽  
Fire Whirl ◽  
Slender Column ◽  
Combustion Processes

Abstract Perhaps the most dramatic example of surprising behavior when circulation is imposed on a combustion-driven flow is the fire whirl, where the burning gases form a tall slender column. Relatively few studies have addressed the influence of circulation on the development of combustion-driven flows. Three dimensionless parameters characterize this interplay: the Froude number, the swirl number and the Reynolds number. It is surprising that for most studies, even with plausible assumptions concerning the experiments, not enough information is given to determine the values of these parameters. We will experimentally reconstruct these studies in an effort to characterize parametrically these interactions. Both buoyancy-driven and momentum-driven combustion processes will be investigated to determine the influence of circulation. Theoretical studies will occur in conjunction to provide the most complete parametric investigation.

Effects of Rotating Blade Wakes on Separation and Pressure Recovery in Turbine Exhaust Diffusers

2008 ◽  
Author(s):  
Olaf Sieker ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
High Energy ◽  
Flow Coefficient ◽  
Pressure Recovery ◽  
High Mass ◽  
Scale Model ◽  
Swirl Number ◽  
Annular Diffuser ◽  
Bladed Rotor ◽  
Turbine Exhaust

Highly efficient turbine exhaust diffusers can only be designed by taking into account the unsteady interactions with the last rotating row of the turbine. Therefore, a scale model of a typical gas turbine exhaust diffuser consisting of an annular and a conical diffuser is investigated experimentally. To investigate the influence of rotating wakes, a variable-speed rotating spoke wheel with cylindrical spokes as well as with NACA bladed spokes generates high-energy turbulent wakes simulating turbine rotor wakes. For the rotor with the NACA blades, the drive of the wheel is run in motor as well as in generator mode. Additional measurements in a reference configuration without a spoke wheel allow the detailed analysis of changes in the flow pattern. 3-hole pneumatic probes, static pressure taps, as well as a 2D-Laser-Doppler-Velocimeter (LDV) are used to investigate velocity profiles and turbulent characteristics. Without the wakes generated by a spoke wheel, the annular diffuser (with a 20° half cone opening angle) separates at the shroud for all swirl configurations. Increasing the swirl results in increasing pressure recovery at the shroud whereas the hub boundary is destabilized. For a non-rotating spoke rotor and low swirl numbers, the 20° annular diffuser separates at the shroud. Increasing the swirl number, a strong deceleration of the axial velocity at the shroud is generated without separation and a higher pressure recovery is achieved. The boundary layer at the shroud of the 20° annular diffuser separates for all operating points with the bladed rotor. A partly stabilized 20° annular diffuser can only be achieved for much higher values of the flow coefficient than that for the design point. At this high mass flow, the NACA-bladed rotor operates as a turbine, resulting in the generator mode of the electric drive. Contrary to the numerical design calculations, the flow at the shroud of a 15° annular diffuser does not separate for all swirl configurations in the experiment. Pressure recovery of the 15° annular diffuser can be increased by increasing the inlet swirl whereas the hub boundary layer is destabilized. For the NACA bladed rotor, the flow in the 15° annular diffuser as well as the pressure recovery strongly depend on the flow coefficient. For flow coefficients lower than the design value, the flow partly separates at the shroud whereas large flow coefficients result in increased pressure recovery. The pressure recovery also depends on the direction of swirl and thus the swirl number.

Modeling of combustor swirl flows

1974 ◽  
Vol 1 (9-10) ◽  
pp. 1129-1147 ◽  
Author(s):  
David G. Lilley
Keyword(s):  
Swirl Flows
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