| With the development of science and technology, substrate culture and hydroponic culture make the production efficiency greatly improved, which have been widely used in agricultural production of fruits and vegetables in developed countries. Whatever cultivation technology has its shortcomings, for instance, the problem of reasonable irrigation exists in substrate culture, that how to increase dissolved oxygen in the water to prevent roots rot also exists in hydroponic culture. With the generation of aeroponics, it is not completely affected by above factors, making the plant roots grow in aerosol environment without substrate and water, which has become most potential way of cultivation for the advantages of extreme water and fertilizer saving, rapid plant growth and convenient management.Atomization cultivation techniques are not mature with respect to soil cultureã€substrate culture and hydroponic culture. Whether root systems can efficiently absorb droplets of nutrient solution is a key to the success of atomization cultivation due to the fact that plant roots hang in the air and water as well as fertilizer are provided by the way of atomization, thus it is of great significance to study the effect of different size droplets on plant growth.The paper consists of the following contents:An ultrasonic atomization nozzle of 54 KHz mainly composed of longitudinal composite transducer and conical horn was designed and size parameters were calculated theoretically. Modal analysis was conducted with ANSYS software. Manufacturing the physical prototype of 54 KHz low-frequency ultrasonic atomization nozzle and conducting the impedance test with PV70 A impedance analyzer. The test results show that the method of theoretical design and modal analysis is correct.An ultrasonic atomization nozzle of 114 KHz was designed, which is mainly composed of piezoelectric disc and metal circular disc. First of all, through mechanical method, the theoretical resonant frequency of medium frequency ultrasonic atomization nozzle was calculated, then the piezoelectric coupling analysis simulation was used to calculate the resonant frequency of medium frequency ultrasonic atomization nozzle. The calculation result accords with the theory of resonance frequency, which indicates that the piezoelectric coupling analysis model is correct. Laser micro displacement sensor was used on medium frequency ultrasonic atomization nozzle midpoint displacement test, the test results are consistent with the simulation results. The clamping device of medium frequency ultrasonic atomization nozzle was designed, which ensures that fluid is stably supplied and the nozzle works steadily.54 KHz low frequency ultrasonic atomization nozzle and 114 KHz medium frequency ultrasonic atomization nozzle designed, combined with the existing 1.7MHz high frequency ultrasonic atomization nozzle cultivated the pea crops and the influence of different droplets diameter on the growth of pea crops was studied. The results show that larger particle size droplets produced by 54 KHz frequency ultrasonic atomizing nozzles help pea crops absorb better, which makes the plants grow faster. |
