Scroll air compressor, a positive displacement rotary machine, uses the meshing of scroll rotor and scroll stator to form multiple compression chambers. With the translation and rotation of the scroll rotor, the volume in each compression chamber is constantly changing, and gas suction and compression are realized.
Working principle of scroll air compressor
The main components in the compressor are two involute scroll wraps, which have the same shape, but their angular positions are relatively staggered180. One is a fixed scroll, and the other is an orbiting scroll driven by an eccentric shaft whose axis rotates around the axis of the fixed scroll. In operation, the two coils are tangent at several places to form a sealing line, and several crescent-shaped air cavities are formed by proper sealing at the end faces of the two coils. The sealing line at the common tangent point between the two volumes continuously moves along the vortex curve with the rotation around the volumes, so that the shapes and sizes of these crescent-shaped air chambers are constantly changing. The suction port of the compressor is opened at the upper part of the fixed volute. When the eccentric shaft rotates clockwise, gas enters the suction cavity from the suction port and is successively sucked into the crescent-shaped gas cavity communicated with the suction cavity. With the closure of these peripheral crescent-shaped air chambers instead of communicating with the suction chamber, the closed volume gradually shifts to the center of the fixed volume and decreases continuously, and the gas is continuously compressed and the pressure increases.
What are the characteristics of scroll compressor?
Advantages:
1, without reciprocating mechanism, so it has simple structure, small volume, light weight, few parts (especially wearing parts) and high reliability;
2, small torque change, high balance, small vibration, stable operation, simple operation and easy automation;
3. It has high efficiency within its adaptive refrigeration capacity range; 4. Low noise
Disadvantages: 1, the surfaces of its moving parts are mostly curved surfaces, and the processing and inspection of these curved surfaces are complicated, and some of them need special equipment, so the manufacturing cost is high.
2. Between moving parts or between moving parts and fixed parts, sealing is often achieved by maintaining a certain movement gap, and gas passing through the gap will inevitably lead to leakage, which limits the rotary compressor from achieving a large compression ratio. So it is often used under air conditioning conditions.
Screw air compressor-also a rotary positive displacement machine, air compression is realized by the change of cogging volume of male and female rotors installed in the casing and engaged in parallel with each other.
Principle of screw air compressor
The cylinder of the screw air compressor is equipped with a pair of mutually meshing spiral male and female rotors, both of which have several concave teeth and rotate in opposite directions. Clearance between rotors and between casing and rotors
Only for line 5 ~ 10, the main rotor (also called the revolute or the revolute) is driven by an engine or a motor (mostly driven by a motor), and the other rotor (also called the mother rotor or the mother rotor) is driven by the oil film formed by the oil injection of the main rotor, or driven by the synchronous gear at the main rotor end and the mother rotor end. So there is no metal contact in the drive (theoretically). The length and diameter of the rotor determine the displacement (flow) and pressure of the compressor. The longer the rotor, the higher the pressure. The larger the rotor diameter, the greater the flow.
The groove of the spiral rotor is filled with gas when passing through the air inlet. When the rotor rotates, the rotor slot is closed by the shell wall to form a compression chamber. When the rotor slot is closed, lubricating oil is injected into the compression chamber to seal it. Cooling and lubrication. When the rotor rotates to compress lubricating oil+gas (oil-gas mixture for short), the volume of the compression chamber decreases and the oil-gas mixture is compressed to the exhaust port. When the compression chamber passes through the exhaust port, the oil-gas mixture is discharged from the compressor, completing a process of suction-compression-discharge. Each rotor of the screw machine is supported by an antifriction bearing, and the bearing is fixed by an end cover near the end of the rotating shaft. The inlet end is supported by roller bearings, and the outlet end is supported by opposite Hertz rollers. Usually, the bearing at the exhaust end locates the rotor, that is, the thrust bearing, which resists the axial thrust and bears the radial load, providing the necessary minimum clearance for the axial operation.
The working cycle can be divided into three processes: inhalation, compression and exhaust. As the rotor rotates, each pair of intermeshing teeth successively completes the same working cycle.
Advantages of screw air compressor:
1) Screw compressors, like piston compressors, are all positive displacement compressors. As far as the use effect is concerned, the screw air compressor has the following advantages.
2) High reliability. Screw compressor has few spare parts, no wearing parts, reliable operation and long service life, and the overhaul interval can reach 40,000-80,000 hours.
3) Convenient operation and maintenance. Screw compressor has a high degree of automation, and operators can run unattended without long-term professional training.
4) Good power balance. Screw compressor has no unbalanced inertia force, and the machine can work stably at high speed without foundation operation. Especially suitable for mobile compressors, with small volume, light weight and small floor space.
5) Strong adaptability. Screw compressor has the characteristics of forced gas transmission, and the volume flow is almost unaffected by the exhaust pressure, which can maintain high efficiency in a wide range. It is suitable for various working conditions without changing the structure of the compressor.
Disadvantages of screw compressor
1) The rotor tooth surface is a spatial curved surface, which needs special tools and expensive equipment for machining, and the machining accuracy of the machine body parts also has high requirements, so high-precision equipment must be adopted:
2) Because the inter-tooth volume is periodically communicated with the air inlet and the air outlet, the noise of the compressor is large;
3) Due to the limitation of rotor stiffness and bearing life, the compressor can only rely on clearance sealing, so the screw compressor can only be used in the middle and low pressure range, not in high pressure occasions;
4) Due to the large amount of fuel injection, the oil treatment system is complex and there are many auxiliary equipment for the unit;
5) Screw compressor relies on the gap to seal the air gap, so it does not have superior performance in a small volume range.
In a word, screw compressor is more and more recognized by the market because of its obvious advantages. With the development of national economy and the improvement of design and manufacturing level of screw compressor, the performance and reliability of screw compressor will be greatly improved, and the market of screw compressor will be wider and wider.