Swirl Effects on Flow Dynamics and Fuel Spray Structure in Practical Combustors

2002 ◽  
Author(s):  
B. Habibzadeh ◽  
A. K. Gupta
Keyword(s):  
Axial Direction ◽  
Diagnostic Tools ◽  
High Shear ◽  
Shape Stability ◽  
Spray Structure ◽  
Spray Flame ◽  
Spray Flames ◽  
Image Velocimetry ◽  
Study Results ◽  
Laser Diagnostic

The effect of high shear in the flow on the spray flame characteristic has been examined. The shear was provided using different swirl combination in the inner and outer swirlers in the double concentric swirl burner. The burner allowed independent control of swirl and combustion airflow in the inner and outer annulus of the burner. Particle Image Velocimetry (PIV) and Phase Doppler Particle Analyzer (PDPA) laser diagnostic tools have been used to obtain comprehensive data related to droplet size, velocity, number density, vorticity in the flow for dispersed phase, and flow and strain rate in the axial direction in the carrier phase. A commercially available twin fluid nozzle has been used in this study. Results have been obtained for a swirl combination of 65° in inner swirler and 30° in outer swirler (referred to as 65°/30°). The results are compared with a swirl combination of 50°/30°. The results show secondary break-up of the droplets with high shear that was not present with low shear in the flow. They also show new way to obtain smaller size of droplets from a spray. Smaller size of droplets allows one to easily control the size, shape, stability and structure of the spray flames.

Control of Spray Flame Characteristics Using High Shear in a Double Concentric Swirl Burner

2002 ◽  
Author(s):  
P. Mehresh ◽  
B. Habibzadeh ◽  
A. K. Gupta
Keyword(s):  
Droplet Size ◽  
Particle Image ◽  
Axial Direction ◽  
Diagnostic Tools ◽  
High Shear ◽  
Number Density ◽  
Swirl Burner ◽  
Spray Flame ◽  
Image Velocimetry ◽  
Laser Diagnostic

The effect of high shear on the spray flame characteristic has been examined. The shear has been provided with the help of swirl angles in inner and outer swirlers (65° in inner swirler and 30° in outer swirler). Laser diagnostic tools like Particle Image Velocimetry (PIV) and Phase Doppler Particle Analyzer (PDPA) are used to obtain an exhaustive set of data related to droplet size, velocity, number density, vorticity in the flow and strain rate in the axial direction. A double concentric swirl burner and a commercially available air-assist nozzle have been used in this study. The burner allowed independent control of swirl and combustion airflow in the inner and outer annulus of the burner. Results have been obtained for a swirl combination of 65° in inner swirler and 30° in outer swirler (mentioned as 65°/30° in the rest of paper) and are compared with the swirl combination 50°/30°, data taken earlier by the authors (1). The distribution of air is also varied as it was done previously. The results provide a thorough understanding of the effect of giving high shear to the combustion air on the droplet size and distribution, which in turn controls the flame characteristic and stability (1).

scholarly journals Vortex Phase-Jitter in Acoustically Excited Bluff Body Flames

2009 ◽  
Vol 1 (3) ◽  
pp. 365-387 ◽  
Author(s):  
Santosh J. Shanbhogue ◽  
Michael Seelhorst ◽  
Tim Lieuwen
Keyword(s):  
Heat Release ◽  
Bluff Body ◽  
Axial Direction ◽  
Harmonic Excitation ◽  
Acoustic Excitation ◽  
Phase Jitter ◽  
Image Velocimetry ◽  
Flow Field Characteristics ◽  
Spatially Periodic ◽  
Phase Phase

This paper describes an experimental study of the effect of acoustic excitation on bluff body stabilized flames, specifically on the flow field characteristics. The Kelvin-Helmholtz (KH) instability of the shear layer is excited due to the incident acoustics. In turn, the KH instability imposes a convecting, harmonic excitation on the flame, which leads to spatially periodic flame wrinkling and heat-release oscillations. Understanding the factors influencing these heat release oscillations requires an understanding of the generation, convection, and dissipation of these vortical disturbances. Phase locked particle image velocimetry was carried out over a range of conditions to characterize the vortical dynamics. It was found that the vortex core location exhibits “phase jitter”, manifested as cycle-to-cycle variation in flame and vorticity field at the same excitation phase. Phase jitter is shown to be a function of separation point dynamics, downstream convection time, and amplitude of acoustic excitation. It leads to fairly significant differences between instantaneous and ensemble averaged flow fields and, in particular, the decay rate of the vorticity in the axial direction.

Analysis of Coherent Structures in the Far-Field Region of an Axisymmetric Free Jet Identified Using Particle Image Velocimetry and Proper Orthogonal Decomposition

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
A.-M. Shinneeb ◽  
R. Balachandar ◽  
J. D. Bugg
Keyword(s):  
Particle Image Velocimetry ◽  
Proper Orthogonal Decomposition ◽  
Coherent Structures ◽  
Particle Image ◽  
Axial Direction ◽  
Orthogonal Decomposition ◽  
Far Field ◽  
Field Region ◽  
Image Velocimetry ◽  
Proper Orthogonal

This paper investigates an isothermal free water jet discharging horizontally from a circular nozzle (9mm) into a stationary body of water. The jet exit velocity was 2.5m∕s and the exit Reynolds number was 22,500. The large-scale structures in the far field were investigated by performing a proper orthogonal decomposition (POD) analysis of the velocity field obtained using a particle image velocimetry system. The number of modes used for the POD reconstruction of the velocity fields was selected to recover 40% of the turbulent kinetic energy. A vortex identification algorithm was then employed to quantify the size, circulation, and direction of rotation of the exposed vortices. A statistical analysis of the distribution of number, size, and strength of the identified vortices was carried out to explore the characteristics of the coherent structures. The results clearly reveal that a substantial number of vortical structures of both rotational directions exist in the far-field region of the jet. The number of vortices decreases in the axial direction, while their size increases. The mean circulation magnitude is preserved in the axial direction. The results also indicate that the circulation magnitude is directly proportional to the square of the vortex radius and the constant of proportionality is a function of the axial location.

Transient Fuel Spray Structure for Simulated Injection Strategies in Direct Injection, Spark Ignition Engines

2001 ◽  
Author(s):  
P. A. Hutchison ◽  
R. B. Wicker
Keyword(s):  
Flow Visualization ◽  
Cross Section ◽  
Direct Injection ◽  
Fuel Spray ◽  
Spark Ignition Engines ◽  
Rail Pressure ◽  
Fuel Injectors ◽  
Spray Structure ◽  
Image Velocimetry ◽  
Direct Injection Spark Ignition

Abstract For two production DISI fuel injectors, flow visualization and particle image velocimetry (PIV) were utilized to illustrate the effect of fuel rail pressure and in-cylinder density (using in-cylinder pressure) on instantaneous fuel spray structure. Studies were performed within a non-motored research cylinder for two fuel rail pressures (3 MPa and 5 MPa) and two in-cylinder pressures (2 atm and 6 atm). Instantaneous flow visualization demonstrated the effects of changes in fuel rail pressure and in-cylinder density on transient spray structure. Increased fuel rail pressure resulted in increased narrowing of the spray cross-section and increased spray penetration distance. Increased in-cylinder density produced sprays with increased narrowing of the spray cross-section and shorter penetration distances. Spray velocities were shown to increase with increased fuel rail pressure and decrease with increased in-cylinder density.

Spray Flames Simulation Using a Two Phase Combustion Model With Single Droplet Combustion Mode

2012 ◽  
Author(s):  
F. Wang ◽  
Y. Huang
Keyword(s):  
Droplet Diameter ◽  
Navier Stokes ◽  
Combustion Model ◽  
Droplet Combustion ◽  
Single Droplet ◽  
Two Phase ◽  
Spray Flame ◽  
Spray Flames ◽  
The Individual ◽  
Individual Droplet

There are three combustion regimes of individual droplet combustion behavior: the fully enveloped flame, the partially enveloped flame, and the wake flame. From PLIF measurement results, single droplet combustion phenomenon happens in spray flame, as well as lean type gas turbine combustion chamber sometimes. The drag coefficient, evaporation rate, and combustion rate are different according to the burning modes. At present, in Reynolds Averaged Navier Stokes (RANS) method and Large Eddy Simulation (LES) method, the droplets are treated as point source because the grid scale is bigger than the droplet diameter. A two phase combustion model with the consideration of the individual droplet burning mode is proposed before. In this paper, this model is tested by spray flames here again. Furthermore, this model was used in a concept lean premixed pre-vaporized (LPP) combustion case too. In spray flame, the predicted results are close to the experimental data.

Spray Flame Study Using a Model Gas Turbine Swirl Burner

2013 ◽  
Vol 316-317 ◽  
pp. 17-22 ◽  
Author(s):  
Cheng Tung Chong ◽  
Simone Hochgreb
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Flame Structure ◽  
Fuel Droplets ◽  
Spray Flame ◽  
Spray Flames ◽  
Reaction Zones ◽  
Fixed Power ◽  
Particle Imaging ◽  
Gas Turbine Burner

A model gas turbine burner was employed to investigate spray flames established under globally lean, continuous, swirling conditions. Two types of fuel were used to generate liquid spray flames: palm biodiesel and Jet-A1. The main swirling air flow was preheated to 350 °C prior to mixing with airblast-atomized fuel droplets at atmospheric pressure. The global flame structure of flame and flow field were investigated at the fixed power output of 6 kW. Flame chemiluminescence imaging technique was employed to investigate the flame reaction zones, while particle imaging velocimetry (PIV) was utilized to measure the flow field within the combustor. The flow fields of both flames are almost identical despite some differences in the flame reaction zones.

Study of Ultrasonically-Induced Fluid Flows Using Micro-Particle Image Velocimetry

2007 ◽  
Author(s):  
Heiko van der Linden ◽  
Ralph Lindken ◽  
Jerry Westerweel
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Pressure Fluctuations ◽  
Fluid Flows ◽  
High Shear ◽  
Shear Forces ◽  
Micro Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Flow Phenomena ◽  
Very High

This paper describes our recently started research into the flow phenomena that occur in microchannels and microcavities during ultrasonic agitation. With micro-particle image velocimetry we have seen rapidly changing flows together with the occurrence of cavitation events. Both these processes suggest that very high shear forces are present in the solution in combination with rapidly changing pressure fluctuations. The research presented here is of importance for the design of ultrasonic mixers and ultrasonic cell lysis devices.

Experimental Investigation of Blood Cells Flowing Through Microscale Geometries Using MicroPIV

2012 ◽  
Author(s):  
Vishwanath Somashekar ◽  
Michael G. Olsen ◽  
K. B. Chandran ◽  
H. S. Udaykumar
Keyword(s):  
Particle Image Velocimetry ◽  
Platelet Activation ◽  
Blood Cells ◽  
Particle Image ◽  
Mechanical Heart Valve ◽  
Reynolds Numbers ◽  
High Shear ◽  
Endothelial Layer ◽  
Micro Particle Image Velocimetry ◽  
Image Velocimetry

The advances made in the field of cardiovascular prostheses have proved invaluable in saving human lives. However, implanting such a device may cause unwanted results like thrombosis, the formation of blood clots inside blood vessels. This formation of thrombi can affect the flow of blood, which if left untreated may result in strokes. As the blood moves through various arteries and veins, the platelets move toward the periphery and the red blood cells (RBC) are more concentrated near the center. This process is called margination and has been shown by Aarts et al.[1]. The platelets in essence are policing the endothelial layer, and with any change in the endothelial layer, say as a result of injury, the platelets get activated, which in turn starts a domino effect eventually resulting in the formation of a clot to stop the bleeding. These platelets can also get activated due to their presence in regions of high shear as is the case when the blood is flowing through narrow constrictions (for example, when a mechanical heart valve is about to close). This phenomenon is referred to as Shear Induced Platelet Activation (SIPA)[2]. The goal of this research is to study the effect of constricted geometries, high shear rates and erythrocyte-platelet interactions on platelet activation and aggregate formation, events that are critical in the initiation of thrombosis. In order to understand SIPA, one must first obtain a detailed flow in these constricted geometries. Numerous studies have been performed to obtain the flow fields of blood flowing through microchannels [3, 4]. However, the Reynolds numbers based on the characteristic length of the microchannel were in the O (1). It is worth noting that for such laminar flows confocal particle image velocimetry can be successfully applied. In this present study, the Reynolds numbers were in the O (100), rendering confocal mPIV impractical and making Micro Particle Image Velocimetry (mPIV) a clear choice.

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