Burner Turndown & Flame Stability Calculator
Thermal engineering & burner aerodynamics: Determine operational turndown ratio ($TDR$), burner port velocity, and boundary velocity gradients for flashback and blowoff stability limits.
Burner Thermal Capacity
High-fire design rating
Low-fire minimum turndown
Nozzle Port Geometry & Flow
Sum of nozzle exit holes / slots
Individual nozzle hole diameter
Lewis and von Elbe Flame Stability
A stable burner flame requires boundary velocity gradient $g$ to remain between the critical flashback limit ($g_f$) and blowoff limit ($g_b$):
$$g = \left( \frac{du}{dr} \right)_{\text{wall}} = \frac{8 \bar{v}}{d} \quad \text{(laminar pipe flow)}$$
$$g_f < g < g_b$$
Turndown & Port Velocities
Turndown Ratio (TDR)
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High-Fire Port Velocity (v_max)
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Low-Fire Stability & Flashback
Low-Fire Port Velocity (v_min)
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Must exceed laminar burning velocity
Low-Fire Boundary Gradient (g_min)
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Flashback if g < g_f
Operational Evaluation
High-Fire Blowoff Margin:
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Low-Fire Flashback Margin:
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Overall Burner Turndown Suitability:
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