Low-frequency ultrasonic atomizing cultivator
Technical field:
The invention belongs to the cultivating device in agricultural engineering field, refer in particular to a kind of low-frequency ultrasonic atomizing cultivator.
Background technology:
Atomising cultivation is that the aerosol training is a kind of novel pattern in the cultivation technique without soil.The aerosol training is that the root system of plant is placed a kind of cultivation mode of growing, growing under the aerosol environment that is formed by nutrient solution fully.It satisfies the demand of root system of plant to liquid manure by the aqueous vapor of atomizing, and obtains the most sufficient oxygen.Root system is grown under this environment, without any the influence of mechanical resistance, thereby root system is free to stretch.It has faster than other any methods of cultivation growth, management is more convenient, throw the littler characteristics of worker, it will become a kind of important planting type of the future of agriculture in producing.
The atomising cultivation device is as the core apparatus of aerial fog cultivation, and its performance directly influences the effect of aerial fog cultivation.But so far, seldom there is document to relate to its Research on Working both at home and abroad.Sichuan Xichang College developed a kind of high frequency ultrasound atomising cultivation device in 2005, and its operating frequency is 1.65MHz.
[1]The high frequency atomizing is directly to utilize the ultrasonic of high-frequency generator generation with the atomization of liquid.Hyperacoustic transmission is according to the sine curve longitudinal propagation, and promptly one deck is strong, a little less than one deck, transmits successively.When weak acoustic signals acts on liquid, then can produce certain negative pressure, thereby a large amount of spaces can appear in liquid internal to liquid, intermolecular force is destroyed simultaneously, and liquid dispersion is come, and realizes the atomizing of liquid.The mist droplet particle size that this kind atomizing type produces is about about 10 μ m, if wanting to produce more tiny droplet then need increase operating frequency, but the increase of operating frequency need reduce the thickness of piezoelectric ceramic piece, causes processing difficulties.
Existing ultrasonic atomizing cultivator has following deficiency:
1. atomization quantity is little.Because the transducer architecture of this type atomizer is a thin slice, be difficult to realize high-power, thereby limited its atomization quantity.Strengthen atomization quantity, must increase atomizer quantity, cost significantly increases.
2. the poor reliability of ultrasonic transducer.Because transducer architecture is a sheet metal, and long-term work very easily produces fatigue fracture at the dither state.
3. the droplet size is non-adjustable, is unfavorable for studying the relation of root growth and nutrition droplet size.The droplet size computing formula of this type atomizer is suc as formula (1).As can be seen, operating frequency determines that its droplet size has also been determined.
D=0.34(8πT/(ρf
2))
1/3 (1)
In the formula (1), T is a surface tension coefficient; ρ is a fluid density; F is a frequency of sound wave.
4. be difficult to produce ultra-fine droplet.According to theoretical result of calculation, produce the droplet of 1 micron of particle diameter, the thickness of transducer is 0.3mm, obviously no matter this thickness still from strength reliability is considered from making angle, all has very big problem.
Summary of the invention:
The present invention is intended to invent that a kind of atomization quantity is big, high reliability, droplet adjustable size, can produce ultra-fine droplet and cheap serial low-frequency ultrasonic atomizing cultivation.
For achieving the above object, designed a kind of serial low-frequency ultrasonic atomizing cultivator of brand new, its driving frequency utilizes ultrasonic nozzle with the atomization of liquid between the 20K-100K hertz.
Operation principle of the present invention is: when liquid is ejected into the surface of solids of a fast vibration, will form the wavy fluid film of one deck at the surface of solids.Along with the increase of solid Oscillation Amplitude, liquid film surface wave amplitude also increases.When liquid film surface wave amplitude increased to certain value, the top of ripple will become unstable and break, and ejected a large amount of tiny vaporific drops from the surface of solids.
The present invention is that atomizer, kinetic pump, nutrient solution case, feeding pipeline, reflux line, glass guide channel, field planting plate etc. are formed by ultrasonic atomizer.Described atomizer is actually a resonance device, it is made up of two pairs of piezoelectric discs that are clipped in the titanium shell, atomizing face is positioned at nozzle exit, the Metal Ball of regulating levitation gap is positioned on the atomizing face, the version of atomizing face is hyperboloid, runner extends to atomizing face always, and the Metal Ball diameter is 4~79 millimeters.Four utmost points that the piezoelectric disc that compresses is imported as high frequency electric source, metal shell is as another utmost point.When the polarity at the two poles of the earth back and forth changed with high-frequency input signal, piezoelectric disc will vibrate with the frequency identical with input signal, and the pressure waves that vibration produces to propagation, causes that nozzle-end takes place and the vibration of input signal same frequency along nozzle shaft.The nozzle length of design just in time equals the wavelength of a pressure wave, and pressure wave forms the standard wave pattern in the stack and the resonance that come back reflective build-up of pressure ripple of two end faces of nozzle.Because free-ended boundary condition restriction, crest is positioned at two ends of nozzle.The size of resonance amplitude is relevant with the diameter of shell, because the diameter of jet expansion end housing diminishes, thereby the amplitude of resonance is exaggerated, and port of export amplitude is far longer than the arrival end amplitude, and the amplitude of increase equates with the variation of nozzle diameter.According to the needs of atomizing, the pressure wave amplitude is minimum should to amplify 6~8 times, and the diameter of jet expansion end housing is 5~80 millimeters, and the amplitude of nozzle exit end vibration has the 0-10 micron, and the version of atomizing face is hyperboloid.
Under the radiated sound field effect of focusing ultrasonic transducer, Metal Ball is suspended, thereby forms a gap in the radiating surface and the Metal Ball of focusing ultrasonic transducer.The nutrient solution droplet after the broken atomizing, is extruded through the gap between ball and the focusing ultrasonic transducer radiating surface by the ultrasonic vibration of curved surface at the radiating surface place of focusing ultrasonic transducer, realizes secondary-atomizing.Have only the droplet of 0-6 μ m size could pass through this gap, form ultra-fine droplet.By changing the density of driving voltage or ball, can change the gap between ball and the focusing ultrasonic transducer radiating surface, make nutrient solution droplet adjustable size.Simultaneously, because this atomizer adopts Langevin sandwich structure, it is simple in structure, reliability is high, the processing and manufacturing cost is low, it is high-power to realize, thereby realizes big atomization quantity.
In sum, the present invention is that a kind of atomization quantity is big, high reliability, droplet adjustable size, can produces ultra-fine droplet and cheap serial low-frequency ultrasonic atomizing cultivator.
Description of drawings:
The novel low-frequency ultrasonic atomizatio shower nozzle that Fig. 1 proposes for the present invention.
Fig. 2 atomising cultivation device of the present invention basic structure schematic diagram.
1, Metal Ball 2, atomizing face 3, runner 4, amplification conversion 5, piezoelectric disc 6, high frequency input 7, kinetic pump 8, nutrient solution case 9, reflux line 10, glass guide channel 11, field planting hole 12, field planting plate 13, feeding pipeline 14, atomizer 15, supersonic signal generator 16, bracing frame
Embodiment:
The present invention is a kind of atomising cultivation device that utilizes the exploitation of low-frequency ultrasonic atomizing principle, and as shown in Figure 2, it comprises kinetic pump 7, nutrient solution case 8, reflux line 9, glass guide channel 10, field planting hole 11, field planting plate 12, feeding pipeline 13, atomizer 14 etc.Kinetic pump 7 one ends link to each other with nutrient solution case 9, the other end links to each other with atomizer 14 through feeding pipeline 13, glass guide channel 10 bottoms link to each other with nutrient solution case 8 through reflux line 9, lay the atomizing pipeline and the atomizer 14 that sprays up be installed at 10 ends of glass guide channel, the top is provided with the field planting plate, for ease of observing, adopts the cultivating groove of glass guide channel as the aerosol training, the bottom surface of glass guide channel is done and is formed difference in height in echelon, is beneficial to the backflow of nutrient solution and recycling.Keep somewhere of backflow and the collection of nutrient solution return port at the end that glass guide channel is low-lying slightly to be used for nutrient solution, and a screen pack is installed near the aperture to prevent hole plug, lay the atomizing pipeline and the atomizer that sprays up is installed in bottom land, buckle the field planting plate then, beat field planting hole by the cultivation requirement on the field planting plate.Again the nutrient solution case is embedded in the soil after building up cultivation system, is beneficial to equilibrium temperature.Behind the good and sound nutrition case, join a kinetic pump again as the nutrient liquid atomizing circulating pump, nutrient solution circulation is just by the startup of pump and close and carry out during work.Wherein the structure of atomizer 14 as shown in Figure 1, it is made up of two pairs of piezoelectric discs that are clipped in the titanium shell, four piezoelectric discs that compress are as utmost points of high frequency electric source input, metal shell is as another utmost point; Atomizing face is positioned at nozzle exit, and the version of atomizing face is hyperboloid, and runner extends to atomizing face always, and the Metal Ball of regulating levitation gap is positioned on the atomizing face, and the Metal Ball diameter is 4~79 millimeters.The nozzle length of atomizer 14 is the wavelength of a pressure wave, and the diameter of jet expansion end housing is 5~80 millimeters, and the version of atomizing face is hyperboloid.