Non-Premixed Burner-Attached Jet Flames in Crossflow Pulsed at Resonance Frequency

Abstract

The flame behavior, flow patterns, and thermochemical structures of a combusting propane gas jet in crossflow excited acoustically at resonance frequency were studied in a wind tunnel. The jet and crossflow Reynolds numbers were 1530 and 1399, respectively. The jet-to-crossflow momentum flux ratio was 0.192. The flame behavior was found to be closely related to the shear-layer vortical flow structures in the near-tube region. Six characteristic flame modes were observed in the domain of jet pulsation intensity . In flame modes 1 and 2 (), the shear-layer vortices were dominant. In flame modes 3–6 (), the flames were dominated by a puffing bent jet. Vortical structures increased in size with increasing . Temperature and combustion product measurements showed significant improvements in mixing and combustion, as well as a reduction of combustion-induced pollutants at the near-tube region of the flame. However, pulsing the jet flame in crossflow at pulsation intensities greater than 0.9 led to a significant increase in the maximum values of carbon monoxide and nitric oxide concentrations at the middle- to far-tube flame regions. Therefore, strongly pulsing a jet flame in crossflow may not necessarily lead to an improved combustion.