• Introduction

• Contents of this web-page
  
1. Overviews of flame configurations
2. Attributes of each configuration
3. Types of measurements and diagnostics
4. Links to CMCS database.

• Browse and Access Experimental Data

• Comments and feedback
• E-mail site-master

• Stationary Flames with Isotropic Turbulence
  
• Stationary Flames with Shear Turbulence
  
• Non-stationary Flames

Common features:
Flow uniformity - relatively flat mean and rms velocity distributions across burner opening
Isotropic turbulence - intensity and scales controlled by grid or plate turbulence generators
Homogeneous mixture - thoroughly mixed upstream with emphasis on lean conditions

 
Oblique Flames

Overview - Oblique flames are generated by placing a flame holder at the center of the burner. The turbulent flame brushes Interact with incident turbulence and grow thicker away from the stabilizer. In most laboratory experiments, the sizes of the flame holder were kept to a minimum so to reduce shear and its influences on the developing turbulent flames. Oblique Flames are either plane-symmetric or axi-symmetric.

Plane-Symmetric Oblique Flame
A V-flame stabilized by a small rod is the most common rendition of a plane-symmetric laboratory oblique flame. There are over 40 experimental publications using this configuation.
Click here to access publication list and database for v-flames. 

Axi-symmetric Oblique Flame
A small bluff body or pilot flame placed at the center of the burner generates an axi-symmetric oblique flame that shapes like an inverted cone.
Click here to access publication list and database inverted cone-flames.

• mean flame brush angle (definition)
• brush thickness and growth rate (definition)

• size and shape of the stabilizer
• heated bluff body or pilot flame adding energy to the system
• use of co-flow

• After burners in jet engines
• Commercial make-up air furnaces

 
Envelope Flames

Overview - Envelope flames are generated by anchoring the flames at the rim of the burner. The turbulent flame brushes burn towards the center and merge to form an envelope over the premixture. Under moderate flow and turbulence levels where open flame tip and local extinction (or quenching) are not likely to occur, the premixture cannot escape without burning. Because the burner rim is not a very effective flame stabilizer, most studies use pilot flames to extend the test matrix.  Envelope flames can be plane-symmetric or axi-symmetric depending on the geometry of the burner.

Plane-Symmetric Envelope Flame
These flames are generated by the use of a rectangular shaped burner (or slot burner) with flame brushes originating at two opposite edges. To preserve the "envelope" features, the two remaining sides of the burner need to be confined.
Click here to access publication list and database for 2D envelope-flames.

Axi-symmetric Envelope Flame
These flames are also known as Bunsen flames. Whereas conventional laboratory Bunsen flames are rich premixed flames, laboratory Bunsen flames of interest to premixed turbulent flame studies are almost all less than stoichiometry. 
Click here to access publication list and database for Bunsen-flames

• mean flame height (definition)
• mean turbulent burning velocity (definition)

• pilot flames adding energy to the system
• non-uniform velocity and turbulence distributions under high Re conditions
• decaying turbulence intensities towards the flame tip

• Domestic and commercial air heating furnaces

 
Unattached Flames

Overview - Unattached flames do not require a flame anchor. They are sustained in divergent flows by vitrue of the propagating nature of premixed combustion. These flame brushes are locally normal to the approach flow and free to repond to incident turbulence without being constrained or "pinned down" at the flame attachment point.

Unattached flames in impinging flows
The divergent flow generated by impingment on a stagnation plate or against each other allows the flame to position itself at a short distrance upstream of the stagnation plane. 
Click here to access publication lists and database for stagnation-flame.

Unattached flames in swirl-generated diverging Flow
Swirling flow with low swirl number (typically less than 0.6) produces a divergent flow with the swirling motion confined to the flow periphery. In the center region, the turbulent flame brush experiences no swirling motion. 
Click here to access publication list and data base for low-swirl burner.

• Displacement flame speed (definition)
• Flame brush thickness (definition)

• downstream heat loss to the stagnation plate
• shape and curvatures of stagnation plate
• flame to wall and flame brush to flame brush interactions
• swirl number
• co-flow

• Diamond deposition
• Commercial and industrial furnaces and boiler

Common features:
Non-uniform flow  distributions - Large velocity gradients and rms velocity peaks
Non-isotropic turbulence - controlled by shear stresses

 
Jet Flames

Overview - The initial velocity profile of a jet flame resembles that of a fully developed pipe flow. The flame brush is mostly confined within the mixing layer of the jet. The flames are very oblique to the incident flow and look slender and tall.

Piloted jet flame
A pilot flame is usually required to stabilize a jet flame due to its high exit velocity.  In the example shown here, a relative large pilot flame (blue disk at the flame base) is used so to produce a very lean jet flame.

Publication lists and database for piloted jet flames under development

• Flame brush growth rate and tip height
  

• Local extinction and re-ignition
• Heat release of the pilot flame adding energy to the system
  

• Blow torch
  

 
Large Bluff-Body Flames

Overview - When a large bluff-body blocks a relative large area of the burner opening, the flame is ahcnored by the hot products trapped inside the wake. The properties of the wake (i.e. size and recirculation strength) have a significant influence on flame properties.

Flame Stabilized by a large bluff body
The wake region of the bluff body is outlined by the tapering shape of the flame. The influence of the wake diminishes downstream and the flame brush flares outward

Publication lists and database for large bluff-body flames under development

• Recirculation zone size and strength
  

• Size and aerodynamic shape of the bluff body
  
• Heat loss to the bluff-body
  

• Commercial and industrial furnaces
  

 
High-Swirl Flames

Overview - High swirl promotes the formation of a recirculation zone and is the essential mechanism for flame stabilization. Swirling flows can be produced either by tangential jet injections or by vane swirlers. The flame is ahcnored by the hot products trapped inside the recirculation zone. The swirl rate (usually expressed in terms of a swirl number) dictates the sizes and stength of the recirculation zone and also most of flame properties.

High-swirl flame generated by a vane swirler
This swirler has a ceter bluff body surrounded by 16 curved swirl vanes. For this particular design, the flame brush is mostly outside of the wake region.

Publication lists and database for large bluff-body flames under development

• Recirculation zone size and strength
  

• Swirl number
  
• Heat loss to the bluff body
  

• Commercial and industrial boilers
• Gas turbines
• Aircraft engines