Effects of small backward inclination on characteristics of a stack-issued combusting transverse jet in crossflow

Effects of small backward inclination on the flame behaviors and thermochemical structures of a stack-issued transverse combusting gaseous fuel jet in crossflow were examined in a wind tunnel. The wind tunnel was used to supply the crossflow. A combusting jet was released vertically into the crossflow through a burner tube to serve as the benchmark. The case that the jet released at a small backward inclination angle of 20o was studied for comparison with the benchmark. The jet-to-crossflow momentum flux ratio ranged from 0.005 to 12. The flame behaviors were studied with photography techniques while the temperature fields were probed using a fine-wire R-type thermocouple. The combustion product concentrations were detected with a gas analyzer. It was found that the flames of the jet issued vertically into the crossflow never detached from the burner tube tip, whereas those of the jet issued from a burner tube at a small backward inclination angle may detach and stabilize above the burner tube exit at high fuel jet velocity before blow-off. The slightly backward inclined combusting jet in crossflow presented slower development to turbulent flames as the jet velocity increased and longer flame length than the flames of the vertically issued jet in crossflow. However, injecting the fuel jet at a small backward inclination angle into a crossflow may lead to a reduction in the emission levels of carbon monoxide and nitric oxide when compared with fuel jets released vertically.