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The principle of operation of the sprayer

Principle of operation

At present, it is divided into four types according to the principle of sprayer spraying.

1. Bernoulli principle
Bernoulli's principle says that in the same fluid, the flow rate is large, but the pressure is small; the flow rate is small, and the pressure is strong. The fluid will automatically flow from high pressure to low pressure. When passing through the three-legged pipe, the low-speed flowing water flows to the high-speed flowing air. The water is torn into droplets by high-speed air (Imagine that the water flowing out of the faucet has a slow speed at first, which is a column of water; but then the speed gradually increases and then becomes drop by drop). These small water droplets become fog after spraying out.

2. The principle of the high-speed water flow breaking into small water droplets after hitting an obstacle
It uses the principle of pressing water into a thin tube to cause a high-speed water flow, and the high-speed water flow breaks into small water droplets when it hits an obstacle.
The situation is like turning on the faucet and blocking it with your fingers. Household sprayers often use this structure, and the cost is low.

3. The principle of the centrifugal force to throw the liquid out
It is a high-speed rotating atomization disk that uses centrifugal force to throw the liquid out and shred it into small droplets.
Similar to the situation when an umbrella is spinning

4. The principle of ultrasonic atomization
Vibration can cause "sprays" on the water surface. The vibration frequency of ultrasonic waves is very high, so the wavelength of its "waves" is very small, so its "sprays"—small water droplets are also very small, and these small water droplets become fog.

At present, the motorized sprayers used in finalized production include knapsack type, stretcher type and tractor traction type. The most common application is the knapsack type. Among them, the Dongfanghong-18 knapsack mist sprayer is the most widely used. The 1E40F gasoline engine (1.6 horsepower) is powered by a high-pressure centrifugal fan. The engine crankshaft directly drives the fan shaft to rotate at a speed of 5,000 rpm. The medicine storage tank is both a liquid storage tank and a powder storage tank, and different parts only need to be replaced in the medicine storage tank. The nozzle is mainly composed of plastic parts, and the same main pipe is used for both misting and powder spraying, and different parts can be replaced on it. Both the engine and the fan are fixed on the frame through a shock-absorbing device to reduce the vibration generated by them at high speed from being transmitted to the frame. The working principle of mist mitigation: When the engine crankshaft drives the fan impeller to rotate at high speed, most of the high-pressure air flow generated by the fan flows through the fan outlet to the nozzle, and a small part flows through the air inlet valve, hose, and filter to the storage tank. The space on the surface of the liquid medicine exerts a certain pressure on the liquid surface, and the liquid medicine reaches the nozzle through the powder door, the water outlet plug connector, the infusion tube, and the switch under the action of wind pressure (the so-called pneumatic infusion). The nozzle is located at the throat of the mist spray nozzle. When the airflow sent from the air outlet of the fan passes through here, the cross section is suddenly reduced, and the flow rate suddenly increases, generating negative pressure at the nozzle. Under the combined action of the positive pressure and the negative pressure of the liquid medicine in the storage tank, the source is ejected from the nozzle, and it just meets the high-speed airflow from the nozzle. Because the two flow rates are very different, and the direction is perpendicular, the high-speed airflow shears the thin or coarse droplets from the nozzle into fine droplets with a diameter of 100~150μm, and they are carried to a distance by the airflow. During the transportation, The air flow further diffuses the tiny droplets and finally settles down. Most of the high-speed air flow generated from the fan flows to the elbow and nozzle through the fan outlet, and a small part enters the powder blowing pipe through the air inlet valve. Due to the high wind speed and high wind pressure, the airflow blows out from the small holes of the powder blowing pipe, which loosens the powder at the bottom of the medicine storage box and blows it to the powder door (the so-called airflow powder delivery). At the same time, since most of the high-speed airflow passes through the elbow of the fan outlet, a certain degree of vacuum is created at the mouth of the powder conveying pipe. Therefore, when the powder door switch is opened, the powder can pass through the powder door, and the powder conveying pipe is sucked into the elbow. A large amount of high-speed airflow is mixed and blown toward the crop through the nozzle.