Impact of turbulence on combustion performance in non-assist waste gas flares

Waste gas flares frequently encounter turbulent crosswinds, which pose significant challenges to maintaining the EPA-mandated 96.5% combustion efficiency for non-assist flares. Strong crosswinds can distort flame shapes, disrupt mixing, challenge emissions measurements due to variable speeds and directions, and ultimately degrade flare efficiency. This study quantifies the impact of crosswind turbulence intensity on non-assist flare combustion efficiency using large-eddy simulations coupled with a flamelet progress variable approach. Results show that while jet-induced turbulence enhances mixing and improves combustion efficiency, turbulence from crossflows increases local strain rates and consistently reduces efficiency. Combustion efficiency drops by up to 10% at turbulence intensities approaching 20%. A new correlation for combustion efficiency, obtained using symbolic regression, captures both experimental and simulation data well across natural gas flare flow rates of 2-4 m/s and wind speeds of 0–10 m/s. Incorporating a power-law dependence on turbulence intensity significantly reduces data scatter.