INFLUENCE OF ENERGY EXCHANGE BETWEEN AIR AND LIQUID STREAMS ON SPRAY CHARACTERISTICS AND ATOMIZATION EFFICIENCY OF WATER-AIR IMPINGING JETS

The paper evaluates the interaction between atomization quality and atomization efficiency, which has not been understood, although it is commonly observed that the atomization quality of different atomizers does not improve linearly with addition of energy. The results quantify the energy exchange between the air and liquid streams of a twin water impinging jets atomizer and its consequences on atomization characteristics and explain the behavior of quality and efficiency. The liquid jet breakup length, liquid jets separation distance at the breakup region and spray angles were measured with high speed photography and the droplet characteristics, such as spatial distributions of mean droplet velocities and diameters and normalized liquid volume flux with Phase Doppler Anemometry (PDA). The results show that the breakup length decreased and the separation distance of the interacting liquid jets at the geometrical ‘impingement’ region increased rapidly as Air-to-Liquid Momentum Ratio (ALMR) increased and then remained constant for ALMR>9. Spray angles were different on different planes through the spray and generally decreased with increasing ALMR and were insensitive to the liquid jets impingement angle. The spatial distributions of average droplet size, velocity and normalized liquid volume flux in the sprays became elongated normal to the plane of the two liquid jets for larger liquid flow rates, in agreement with the spray angle in the near nozzle region. The spatially-averaged Sauter Mean Diameter (SMD) of the sprays quantified uniquely the atomization quality and showed, for the first time, that it did not depend on liquid jets impingement angle. The average SMD