Experimental Study Of Atomization Characteristics Effected By Injector Geometry And Spray Condition On An Internal Mixing Air Atomizing Nozzle

Air atomizing nozzles can improve spray quality by employing a relatively high speed air or steam flow to accelerate jet breakup and atomizition, it have been widely used in internal combustion engine and indurstrial burner in recent years. Especially internal mixing air atomizing nozzle is used more often, because it required lower gas flow rate, have undemanding manufacturing process and uneasy plugging, so studying its spray characteristic is meaningful. In this thesis, experiment was performed to investigate the effect of injector geometry and spray condition on the spray characteristic of an internal mixing air atomizing nozzle. In the experiment, micro-characer was measured using Malven laser particle size analyzer, and macro-character was measured using high resolution digital SLR camera.Water and air were used in the laboratory tests as atomized and atomizing fluids for the fundamental research. In this research, injector geometry including diameter of nozzle, radius of curvature of the inlet corner and the surface roughness of the orifice, and spray condition including liquid flow and air presure were studied for the effects on the spray characteristics, such as Sauter mean diameter(SMD) change along with the nozzle outlet axial distance, droplet size distribution, spray angle cone, spray stability and air consumption. The main conclusion are as follows:(1) On injector geometry influence aspect, diameter of nozzle have obvious impact on SMD when surface roughness is 0.8, but have unobvious impact when surface roughness is 3.2. While SMD decreases with the inreases of surface roughness or radius of curvature of the inlet corner. Besides injector geometry have an influence on droplet size distribution, but affected by large particles, that SMD value is smaller do not represent the number ratio of small particles is higher in the droplet size distribution.(2)On spray condition influence aspect, when decreasing the liquid flow or increasing the air pressure, the SMD was getting decreased. In most case, when SMD have a small value, the number ratio of small particles is small in the droplet size distribution, but in rare cases it is not.(3)When injector geometry or spray condition changed, the change of spray cone angle is small and have no obvious regularity.(4)The stability among mean diameter and characteristic diameter are compared under the same spray condition, finding D32 is the best, D0.5 comes second and D0.9 is the worst.(5)When keep injector geometry unchanged, liquid flow have a very small impact on air consumption, but with air presure increasing, air consumption become higher. When keep spray condition unchanged, air consumption get lower with nozzle diameter reducing or the the orifice surface smooth, and there is a optimal radius of curvature of the inlet corner to minimize air consumption.