Design And Test Of Low Frequency Ultrasonic Atomization Nozzle With L-type Double-stage Resonance Tube

Compared with ordinary two-phase flow nozzles,the droplet that the mechanical hydrodynamic ultrasonic atomizing nozzles atomize is smaller,and the atomization amount it atomizes is larger than that of the conventional piezoelectric low-frequency ultrasonic atomizing nozzles,with relatively extensive spatial distribution of the droplets.The existing nozzles with smaller atomization volumes are gradually unable to meet the increasing demand for agricultural production.In order to ensure high quality of the atomized droplets' quality,the amount of atomization the nozzles atomize should also be large and the spray range should be wide to meet the production needs of large-scale atomized cultivation.Based on the basic theory of Hartmann resonance tube and the working mechanism of supersonic gas atomizing nozzles,a kind of mechanical hydrodynamic low frequency ultrasonic atomization nozzle with L-type double-stage resonance tube is designed and manufactured,which consists of a Laval tube and a L-type double-stage resonance tube that can not only atomize high-quality droplets,but also has a large amount of atomization and a wide range.With the method of numerical simulation of computational fluid dynamics,the relationship between the length of the resonance tube and the angle between the central axis of these two stage resonance tubes and the resonance performance of the resonance tube is studied in a parametric way.The conclusions are used to determine the key parameters,so as to guide the design of the nozzle.With control variables,when the other conditions are the same and the length of these two stage resonance tubes is twice the diameter of the resonance tube,the gas fluctuation in the resonance tube is stable,the resonance frequency is high,and the resonance performance is fine.The amplitude of pressure fluctuations under these conditions is also larger by best utilization of the input energy,and the energy conversion efficiency is higher.The numerical simulation results also show that when the angle between the central axis of these two stage resonance tubes is 80 degrees,the resonant conditions of these two resonance tubes are relatively uniform,the resonant frequency is relatively high,the amplitude of the pressure fluctuation is large,and the resonant performance is fine.According to the results obtained by numerical simulation,the length of the L-type double-stage resonance tube designed and manufactured is selected to be twice the diameter;in order to reduce the flow loss and improve the energy conversion efficiency.the diameter of the resonance tube is designed equal to the diameter of the Laval tube outlet.Accordingly,in order to get the the optimal value of the angle between the central axis of these two stage resonance tubes,the nozzle and the L-type double-stage resonance tube sample are manufactured.The test results show that:(1)the structure and key dimensions of the nozzle will cause the gas supply system to have a greater impact on the liquid supply system.The specific manifestation is that the increase of the system air supply pressure will lead to the increase of the system liquid supply pressure and the supply flow rate.(2)Under a certain supply pressure,the droplet size atomized by a nozzle with a resonance tube with a different angle between the central axis of these two stage resonance tubes firstly decreases sharply with the increase of the angle.It gradually maintains a steady trend,when the droplet size decreases slowly.The droplet size reaches to 12.7?m(When the temperature of liquid supply is 10°C)and 11.4?m(When the temperature of liquid supply is 40°C)when the angle between the central axis of these two stage resonance tubes is 80 degrees.The amount of atomization at this time is about 1.7L/h.When the angle increases to 90°,the droplet size will increase as a whole;(3)When the supply pressure is 0.3MPa or 0.4MPa or 0.5MPa,the atomization angle of the low frequency ultrasonic atomization nozzle with L-type double-stage resonance tube is larger than that of the Hartmann low-frequency ultrasonic atomization nozzle with stepped resonator,and the of the atomization angle is 10.21° at 0.5 MPa;(4)Under each supply air pressure,the overall spray distance of the low frequency ultrasonic atomization nozzle with L-type double-stage resonance tube is much greater than that of the stepped resonator nozzles with vortex impeller,with the spray distance from a ratio of about 5 to 6.