Whether the atomization level is good or not, the performance of the nozzle is very important

In the spray apparatus, whether it is a spray machine with complex structure or a spray machine with intuitive structure, its basic structural units include liquid medicine tank, pressure pump, liquid medicine pipe, spray bar and nozzle. The nozzle is the most critical component, which indirectly restricts the atomization level of spray. No matter its shape, material or internal structure, it needs careful design and optical manufacturing. According to the type and performance of the sprinkler, there are exact techniques to control when spray in the field.

The role of the nozzle in the spray apparatus includes: the spraying amount, the uniformity of spraying, the coverage of the target, and the control of droplet drift.

1、 Types and working principles of common nozzles

1. Vortex type nozzle: There is a vortex chamber outside the nozzle. The liquid medicine driven by the hydraulic pressure from the highway rotates around the vortex root in the vortex chamber. The centrifugal force generated pushes it to spin out from the orifice and collides with the air molecules to form a hollow or hollow conical fog. The central fog drop of the hollow cone is difficult, while the edge fog drop remains. The opposite is true for solid cone fog. The droplet size is indirectly related to the liquid pressure and the orifice diameter. The pressure is low, the nozzle is large, and there are many fine fog droplets; The newly ejected droplets are small, and gradually become larger as they collide with air molecules along the way.

At present, the Gongnong-16 knapsack spray with the smallest amount in China basically adopts hollow cone nozzles.

Although these backpack spray have been changed from manual to electric in recent years, which has solved the problem of high and unstable pressure, because the liquid medicine sprayed from this hollow conical nozzle falls on the target in a hollow circle shape, the lower liquid medicine is difficult, and the edge liquid medicine is surplus, and the distribution is very uneven. This requires that the nozzle should be swung left and right during the spray operation so that the droplets can be evenly covered on the target. There is an indirect relationship between the speed of walking in the field and the coverage of fog droplets on the target. Yuan Huizhu, a researcher from the Institute of Plant Protection of the Chinese Academy of Agricultural Sciences, found through experiments that the faster the walking speed is, the smaller the difference in fog droplet coverage is, and the more uneven the coverage is. Therefore, many farmers use this method to inject medicine quickly. They add more medicine and add less water. They walk quickly. It seems that the practice of pumping only one bucket of water per mu of land can never ensure that the target can be covered with enough liquid medicine, which is one of the reasons why good medicine has no bad effect.

2. Impinging nozzle (high-pressure spray gun): it is composed of nozzle, spray cap, spray bar, diffuser and other parts. The principle is that the pressure of more than 1500~2500 kPa is used to rush out from the nozzle in a column shape and collide with the air to form a drug mist. The flow rate per minute reaches 30 liters, and the minimum range is about 15 meters. By adjusting the extension and retraction of the spray bar, the spray range and distance can also be controlled, and the spray bar can be compressed to compress the space in the spray gun, so that more and more small droplets are sprayed, and the spray range increases, and the distance decreases. During production, many fruit growers often do not pay attention to the balance between poor pressure, spraying amplitude and atomization quality after spraying operation, so that the effect of spray is not perfect.

3. Sector nozzle: there are two types: slit type and impact type. There are two mutually perpendicular half moon shaped grooves outside the slit nozzle. The liquid medicine is now divided into two streams in the inner half moon shaped groove. The two streams of liquid medicine meet near the orifice and break into fog drops. Under the restriction of the outer half moon shaped groove, the two streams of liquid medicine are fan-shaped, and the working pressure is relatively small, usually 150~200 kPa; The outer end of the nozzle of the impact nozzle is equipped with a liquid medicine deflector structure, which makes the spray droplets fan-shaped at a large angle (130 degrees). The spray angle is significantly smaller than that of the normal nozzle (60~90 degrees), but the working pressure is relatively high (40~100 kPa), and the spray droplets are also small. They are often used for spraying herbicides. No matter which type of fan sprinkler is used, the sprinkler shall not swing from left to right like the hollow cone sprinkler during field operation, and shall be pushed horizontally before moving.

4. Mist sprayer: different from the later sprayers driven by hydraulic pressure, this type of sprayer guides the liquid medicine into a strong airflow field, where the liquid medicine is hit by the high-speed airflow into fog drops and pushed to the target by the airflow. Mist spray nozzles are divided into rotary vane type, remote type and air flow type. The droplets formed are small, and with the aid of air flow, the droplets sprayed onto the target can be more and more badly distributed on the front and back of the leaf and in the crop canopy.

2、 Operation walking and control of spray equipment

1. Select the appropriate nozzle:

Fan shaped spray nozzle: the spray droplets are evenly distributed, which is important for spraying herbicides for soil treatment and stem and leaf treatment, and also for spraying pesticides or fungicides for the prevention and control of plant diseases and pests at seedling stage.

Conical spray nozzle: it can be used for the prevention and control of crop diseases and pests in the field. Nozzle pieces with different apertures can be selected according to the prevention and control objects.

Adjustable spray nozzle: it can be used in orchard or spray bar spray to adjust the spray width and droplet size of the nozzle according to the target and wind speed

The single sprinkler is used in the later stage of crop growth.

Double sprinklers are used for directional spraying at the top of plants in the later stage.

When multi nozzle spray, it is necessary to adjust the distance and spraying range between bad nozzles in advance to avoid re spraying and missed spraying.

2. Control the walking speed according to the type of nozzle:

According to the type and operating pressure of the nozzle, it is necessary to know something about its flow. Before spray, it should first use a container with a measuring scale to test the liquid spraying flow of the spray device per minute, and then calculate the appropriate pace or machine walking speed, spraying amount per unit area, etc.

When using spray guns in the orchard, connect the spray guns with rubber hoses and the interfaces on the pipeline controller. Adjust the working pressure. In addition, check and adjust whether the spray shape of the spray gun reaches the perfect working state. After adjustment, start spraying.

3. Determine the direction according to the wind direction:

Spray is the most appropriate in light wind conditions. People's walking direction should be perpendicular to the wind direction. The angle between the wind direction and the direction should not be less than 45 degrees. The operation sequence should start from the downwind side of the whole plot. Never work against the wind.

The traveling route of spraying operation shall be used as the alternate side spraying. If you finish spraying the first line and spray the second line, you shall walk between the second line and the third line, so as to avoid poisoning accidents caused by liquid medicine adhering to the body. With the help of government affairs, swing the spray bar from side to side in front of the body, so that people can walk through the drug application area, which is difficult to cause poisoning. In addition, when spraying with several machines and tools, the ladder shall be used to move forward, and the person at the downwind side shall spray first.

4. Adjust the distance between the bad nozzle and the target according to the device type and wind force:

The speed of spray droplets from the nozzle is usually about 20 m/s, which varies according to the size of the spray droplets. The speed decreases to zero when it runs about 20-60 cm. However, for the spray equipment in production, there will be some devices that will give impetus beyond the amount of fog drops. According to the principle of force and reaction force, the closer the nozzle is to the target, the larger the proportion of droplet rebounding and splashing will be; In addition, the diameter of the fog droplets just sprayed from the nozzle is also small, so they cannot adhere to the target. When the wind is small, the thick fog droplets are easy to drift to the non target. Therefore, when spraying in the field, there should be a suitable distance between the nozzle and the target according to the type of spray equipment and the wind force.

Generally, the distance between the nozzle and the target of a manual spray device is 30~50cm,

The distance between the nozzle and the target of a motorized spray device is 40~80cm. The smaller the pressure is, the farther the distance is, and the smaller the wind is, the closer the distance is;

In general, the sprayer is the core component of the spray equipment to ensure the quality of spray. During production, it is not only necessary to select appropriate spray equipment, but also more and more important to select and maintain the sprayer, and properly use the spray according to the type and working principle of the sprayer.