Adaptive air distribution in an ejector burner for the utilisation of methanol-mixed fuels

Numerous studies have focused on the utilisation of alcohol fuels because of the energy crisis. However, the combustion efficiency and stability of alcohol fuels are unacceptable. This study proposed an ejecting combustion method for utilising methanol-mixed fuels and numerically investigated the characteristics of adaptive air distribution in an ejector burner. The geometrical parameters of the ejector burner were optimised and validated by an experiment. Results show that the suction effect of negative pressure in the mixing chamber and the entrainment effect of fuel jet flow both play important roles for an ejector burner to draw air. The positions of ejector nozzle exit locating at the suction chamber axis and low operating pressure are beneficial for obtaining a stable air distribution. Molar entrainment ratio (MER) rapidly increases with an increase in parameter α, which is defined as the ratio of throat diameter to nozzle exit diameter, but declines with increasing ejector back pressure. In the experiment, the changing rate of MER is less than 6.4%, and combustion efficiency is higher than 99.2% in the load range of 20-120%, which is highly consistent with that of the simulation. The optimised burner could automatically distribute air supply and facilitate stable combustion.