Swirl-stabilized flames: Fluid dynamics, mixing, and flame stability limits
Several unique features of swirl-stabilized flames have been quantified and explained in this study. Results can be categorized into the following four areas. (1) Recirculation strength was measured and various trends were determined. (2) The fuel-air mixing process was visualized in swirl flames, which has not been done in the past. The internal recirculation helps to enhance fuel-air mixing, as evidenced by an up to five-fold shortening of the flame length of a turbulent jet diffusion flame. A second vortex mechanism is due to the impingement of opposing jets at the forward stagnation point, and provides initial fuel-air mixing and acts like a pilot flame to stabilize the flame. (3) Flame length, which is a measure of overall fuel-air mixing, was measured and various trends were determined. A simple scaling analysis was developed which explained several of the measured trends in the flame length data and why swirl flame lengths do not scale in the same manner as jet flames. (4) Three distinct flame blowout limits were measured; they are due to excessive swirl, very weak swirl, and excessive fuel jet momentum, respectively. Laser Doppler Velocimetry (LDV) was used to obtain relevant velocity data. It was found that (1) the density change due to combustion promotes recirculation, (2) increasing swirl and Reynolds numbers affect the inlet boundary conditions in a favorable manner to cause recirculation, and (3) increasing fuel jet momentum weakens recirculation strength and destabilizes the flame. Comparisons were drawn with bluff-body flows and vortex breakdown phenomena observed in water flows. It was found that Reynolds number effects that had been reported for water flow studies are similar to effects observed in the present flame.
- Research Organization:
- Michigan Univ., Ann Arbor, MI (United States)
- OSTI ID:
- 6835897
- Country of Publication:
- United States
- Language:
- English
Similar Records
Combustion stability limits and planar imaging of swirl-stabilized flames
Hysteresis and transition in swirling nonpremixed flames
Related Subjects
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
BOUNDARY CONDITIONS
CHEMICAL REACTION KINETICS
COMBUSTION KINETICS
COMPARATIVE EVALUATIONS
DIFFUSION
DIMENSIONS
EVALUATION
FLAMES
FLOW RATE
FLOW VISUALIZATION
FLUID FLOW
FLUID MECHANICS
FUEL-AIR RATIO
HYDROGEN COMPOUNDS
INHIBITION
JETS
KINETICS
LENGTH
MEASURING INSTRUMENTS
MECHANICS
MIXING
OXYGEN COMPOUNDS
REACTION KINETICS
REYNOLDS NUMBER
STABILITY
TURBULENT FLOW
VELOCIMETERS
VORTEX FLOW
WATER