Working principle of single screw air compressor

Single screw compressor structure diagram]

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the single screw air compressor is a positive displacement compressor. By compressing the gas in a variable volume, the volume of the part is reduced and the pressure is increased. The core structure of the compressor is finished by a special machine tool. It consists of a screw with six spiral grooves, and a pair of flat star wheels on both sides form a working cavity. The rotation of the screw drives the star wheels to make a cycle in the closed casing. The suction, compression, and exhaust rotary motion, each rotation of the screw generates 12 compression cycles. The screw of the single screw compressor meshes with two star wheels at the same time, so that the force of the screw is completely balanced, and the displacement is doubled, and the volume of the compressor is small.

(1) Host working process:

suction: The gas enters the rotor tooth slot through the suction port. With the rotation of the rotor, the star wheel enters the state of meshing with the rotor cogging, and the gas is then sucked into the enclosed space formed by the rotor cogging surface, the casing and the star gear tooth surface, that is, the compression cavity.

compression: As the rotor rotates, the volume of this compression chamber is continuously reduced, I .e. the gas is compressed until the leading edge of the compression chamber passes to the exhaust port.

exhaust: After the front of the compression chamber is transferred to the exhaust port, exhaust will begin until the compression chamber completely passes through the exhaust port to complete a working cycle.

(2) System gas flow process

after the outside air is filtered by the air filter to remove dust, it enters the compressor host through the unloading valve for compression, and is mixed with lubricating oil in the compression cavity. The compressed mixed oil and gas enters the oil and gas tank through the exhaust check valve and is in the oil and gas tank. Rotate to separate most of the lubricating oil, and then filter out the remaining lubricating oil through the oil and gas fine separator. Then through the minimum pressure valve, cooler and water separator, the compressed air is sent to the use system for customers at a lower temperature and drier.

System lubricating oil flow process

the lubricating oil in the oil and gas tank is pressed into the oil cooler under the pressure of compressed air, and then sent to the oil filter to filter out dirt and impurities after being cooled in the oil cooler. The filtered lubricating oil is divided into two ways after passing through the oil cut-off solenoid valve. One way is injected into the compression chamber from the lower end of the main engine to cool the compressed air. The other way leads to both ends of the main engine to lubricate the bearing group, and then gathers at the bottom of the compression chamber and discharges with the compressed air. After passing through the exhaust check valve, these oil and gas mixtures are separated in the oil and gas tank and the oil and gas fine separator respectively before starting another cycle.

The lubricating oil of the screw compressor has three main functions: lubricating the contact surface of the bearing and the rotor; sealing the meshing pair clearance; cooling the compression process. The cooling compression process is the most important.

control system

basic functions of microcomputer controller

the microcomputer controller displays the temperature, pressure, running time and various working conditions of the unit through a large screen liquid crystal (LCD). The operator can query and set the controller series data through the man-machine communication interface on the monitor panel.

The main working process of the system: the fault detection is carried out first after the system is powered on. The faults are divided into heavy faults that affect normal operation and faults that do not affect normal operation. Heavy fault alarm shutdown, light fault alarm but no shutdown, and record relevant information. Start-up is allowed after fault monitoring. After starting, the main motor enters the planetary/triangular conversion, and the air compressor starts to supply air to the peripherals. When the pressure is less than the parameter set value, the air compressor is loaded; when the pressure is greater than the set value, the air compressor is unloaded. After the unloading status exceeds the preset value, the air compressor will be shut down for too long. Loading, unloading, empty car too long shutdown for the main working state of the air compressor.

advantages

in addition to the simple structure, small size and few wearing parts of the rotary compressor, the single screw compressor also has many unique advantages. These advantages are mainly due to the symmetrical configuration of the two star wheels on both sides of the screw.

Reasonable structure with ideal force balance

due to the axial bleed air channel in the screw body, the high-pressure gas leaking to the high-pressure side (exhaust side) of the screw will flow back to the low-pressure side (suction side) through the bleed air channel to balance the gas forces acting on the two ends of the screw. Due to the symmetrical configuration of the star wheel, the radial gas forces acting on the screw are also balanced and offset each other. The screw is therefore not subject to any radial or axial gas forces. The force on the star gear teeth is very small, only about 1/30 of the piston and twin screw compressors. Therefore, the bearings on the screw shaft and the star shaft have a long life. The radial load of the twin-screw compressor gas can not be balanced, and the axial load can only be balanced by the additional balance piston, so the structure is complex.

⑵ Large single machine capacity, no clearance volume

when a single screw compressor works, each groove on the screw is used twice in one revolution, so that the groove space can be fully utilized, so that the structure size is smaller than that of other rotary compressors. In addition, the groove depth of the screw becomes shallower with the increase of the compression chamber pressure, and the depth is zero at the end of the exhaust, so there is no clearance volume in theory.

Low noise, small vibration

the single screw compressor has good force balance, so the vibration is small, and there is no special requirement for the foundation. In particular, the star wheel is made of special engineering plastics with good self-lubricating performance. The working cavity is sprayed with lubricating oil and there is no additional gear, so the operation noise is low. The screw drives the star wheel to rotate only to overcome the small shaft pump friction. Screw speed is usually in the 3000 r/min, as long as the meshing pair line design is reasonable, it is easy to establish fluid dynamic lubrication, fundamentally solve the problem of star gear tooth wear.