Gas Turbine Combustor: Swirl Flame Stabilization (2D)

Swirler & Mixture

Vane angle θ 45°

Equivalence ratio φ 1.00

Inlet velocity U₀ 25 m/s

Flame State

UNLIT

Swirl number S

0.00

Damköhler Da

0.00

Laminar S_L

0.00 m/s

CTRZ length

0.0 D

How it works

This is the 2D-native counterpart to the 3D swirl-combustor simulator. Instead of orbiting a rendered particle cloud around the duct axis, it draws the meridional (x–r) cross-section directly — the plane in which the governing swirl-flow equations actually live, since the flow is axisymmetric — plus a live operating map and the flame-speed curve that decide the outcome:

Swirl number:      S = (2/3)·tan(θ)      (radial-vane swirler, hub/tip ≈ 0.5)
Breakdown onset:   CTRZ forms once S > S_c ≈ 0.6
Stabilization:     Da = τ_res / τ_chem  (Damköhler number)
                   τ_res  = L_CTRZ / U_recirc
                   τ_chem = α / S_L²      (α = thermal diffusivity)
                   Flame stays lit while Da > Da_crit ≈ 1

The laminar flame speed S_L and adiabatic flame temperature both peak near stoichiometric (φ = 1) and fall toward zero at the lean and rich flammability limits (φ ≈ 0.5 and φ ≈ 1.6 for methane–air). Two failure modes bound the operating window:

Lean blowout (LBO) — too lean, or U₀ too high for the CTRZ that forms: τ_res drops below τ_chem, Da falls under 1, and the recirculating gas cools faster than it can re-ignite fresh mixture. Shown in the cross-section as particles never turning hot, and in the operating map as the grey region.
Flashback — at low U₀ with a strong, near-stoichiometric mixture, the swirl-enhanced turbulent flame speed can exceed the local flow velocity near the swirler throat and the flame propagates upstream into the premixing passage. Shown as the red region of the operating map.

Numerical fix during porting: the 3D source computes the turbulent flame speed for the flashback test as a flat S_L × 3.0, compared against 0.28·U₀. Sweeping the entire slider range (θ 20–70°, φ 0.5–1.6, U₀ 8–55 m/s) shows that threshold is never crossed — flashback is unreachable in the 3D original regardless of settings. This 2D version instead scales the turbulence-driven enhancement with the swirl number itself (S_L × (3.0 + 4.0·S), since a stronger swirl genuinely produces more shear-driven turbulence), which restores a reachable, physically sensible flashback region at low U₀ with strong swirl and a near-stoichiometric mixture.

Drag the sliders to sweep the vane angle, equivalence ratio and inlet velocity and watch the CTRZ (translucent ellipse) grow or shrink in the cross-section, the operating-map dot move between regions, and the flame-speed marker slide along its curve.

Unburned mixture Burning / hot products Recirculation zone