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Analysis of flame acceleration in open or vented obstructed pipes
Vitaly Bychkov1, Jad Sadek2, V'yacheslav Akkerman2
1Department of Physics, Umeå University, Umeå 90187, Sweden.
Physical Review. E
|February 18, 2017
Summary
A shockless flame acceleration mechanism, driven by jet flow from delayed combustion, is demonstrated in obstructed pipes. Viscous forces cause initial delays but do not drive acceleration, moderating it instead.
Area of Science:
- Fluid dynamics
- Combustion science
- Acoustics
Background:
- Flame acceleration in obstructed pipes is often linked to turbulence or shocks.
- A prior study identified a shockless, laminar flame acceleration mechanism in semi-open pipes driven by jet flow.
Purpose of the Study:
- Extend the shockless flame acceleration theory to open obstructed pipes.
- Analyze the role of hydraulic resistance and viscous forces in flame acceleration.
- Compare theoretical predictions with experimental and simulation data.
Main Methods:
- Theoretical analysis using inviscid approximation.
- Incorporation of hydraulic resistance (viscous forces) into the model.
- Comparison with experimental and simulation results.
Main Results:
- Flames strongly accelerate in open or vented obstructed pipes via a shockless, laminar mechanism.
- Acceleration is weaker in open pipes compared to semi-open pipes.
- Hydraulic resistance moderates acceleration; viscous forces cause initial delays but do not drive it.
Conclusions:
- The shockless, jet-flow-driven mechanism explains flame acceleration in open obstructed pipes.
- Viscous forces are crucial for explaining initial flame delay, improving model-experiment agreement.
- The theory provides a unified understanding of flame acceleration in various obstructed pipe configurations.
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