The principle, application, performance, advantages and disadvantages of the most complete scroll compressor!

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Scroll compressor

1. Working principle

The main components in the scroll compressor are two involute scrolls with the same shape but 180° staggered angular phase position, one is a fixed scroll, and the other is driven by an eccentric shaft, the axis of which is around An orbiting scroll that revolves around the axis of the fixed scroll.

During the work, the two scrolls are tangent in many places to form a sealing line, and proper sealing at the end faces of the two scrolls are added, thereby forming a several-month-shaped air cavity. The sealing line at the common tangent point between the two scrolls is continuously shifted along the scroll curve as the orbiting scroll revolves so that the shape and size of these crescent-shaped air cavities are constantly changing. The suction port of the compressor is opened in the upper part of the fixed scroll casing.

When the eccentric shaft rotates clockwise, the gas enters the suction chamber from the suction port and is successively absorbed into the peripheral crescent-shaped air chamber that communicates with the suction chamber. As these peripheral crescent-shaped air cavities are closed and no longer communicated with the suction cavity, their closed volume is gradually transferred to the center of the fixed scroll and shrinks continuously, and the gas is continuously compressed and the pressure rises.

2. Application of scroll compressor

Scroll refrigeration compressors are currently mainly based on fully enclosed structures and are mainly used in air conditioners (heat pumps), heat pump hot water, refrigeration, and other fields.

The supporting downstream products are household air conditioners, multi-line, modular machines, small water and ground source heat pumps, etc. At present, there are manufacturers of scroll refrigeration compressors that can achieve 20~30HP per unit.

3. Advantages of scroll compressors

(1) It belongs to the third-generation compressor. Multiple compression chambers work at the same time. The gas pressure difference between adjacent compression chambers is small, the gas leakage is small, and the volumetric efficiency is high, up to 98%, which is higher than that of the second-generation compressor rotor. The compressor efficiency is about 5% higher;

(2) The eccentric shaft that drives the movable scroll can rotate at high speed, so the scroll compressor is small in size and light in weight;

(3) The force change of moving parts such as the movable scroll and the main shaft is small, and the vibration of the whole machine is small;

(4) There are no suction and exhaust valves, the scroll compressor operates reliably, and is especially suitable for variable speed motion and variable frequency speed regulation technology;

(5) The compression cavity of the scroll compressor is composed of a scroll profile, which is a multi-chamber compression mechanism. When the center of the movable scroll makes a circular motion around the center of the stationary scroll, the volume of each compression cavity changes with the rotation angle of the main shaft. It will be correspondingly reduced or enlarged, thereby realizing the process of gas inhalation, compression, and exhaust. Since the process of inhalation and exhaust is almost continuous, the noise of the whole machine is very low;

(6) The axial and radial flexible structure improves the production efficiency of the scroll compressor and ensures that the sealing effect of the axial gap and the radial gap is not reduced due to friction and wear, that is, the scroll compressor is reliable and effective. Therefore, the cooling coefficient does not decrease with the increase of operating time, but increases slightly;

(7) The scroll compressor has good working characteristics. The performance is mainly affected by its own compression ratio and suction pressure. The exhaust pressure has a wide range and is suitable for various indoor and outdoor environments to ensure that the compressor has been running with high energy efficiency ratio. , so as to ensure the energy efficiency ratio of the air conditioning unit. In the heat pump air conditioning system, it is especially manifested in high heating performance, good stability, and high safety;

(8) The scroll compressor has no clearance volume and is structurally multi-chamber compression. The pressure difference between adjacent chambers is not very large (approximately continuous change). The axial back pressure is compressed so that the moving and stationary scrolls are in close contact, and with the help of refrigeration oil, a good sealing effect is achieved, so that there is almost no internal leakage; when the end plane of the sealing strip is worn, it can move along the shaft The direction is automatically compensated to ensure that the end face of the movable scroll and the bottom surface of the stationary scroll is always in close contact, and the longer the compressor works, the better the cooperation between these close relative moving surfaces and the better the sealing effect. These advantages make the scroll The rotary compressor does not have the problem of secondary compression of refrigerant gas, which is one of the important guarantee factors for maintaining high volumetric efficiency;

(9) Small torque change, high balance, small vibration, and stable operation, so that the operation is simple and it is easy to realize automation;

(10) Because of its few moving parts and no reciprocating mechanism, it has a simple structure, small volume, light weight, few parts (especially few wearing parts), high reliability and a life span of more than 20 years.

4. Disadvantages of scroll compressors

(1) The surfaces of the moving parts are mostly curved surfaces. The processing and inspection of these curved surfaces are complicated. The manufacturing requires high-precision processing equipment and precise self-aligning assembly technology, so the manufacturing cost is high.

(2) Between the moving parts or between the moving parts and the fixed parts, a certain movement gap is often maintained to achieve sealing, and the gas passing through the gap will inevitably cause leakage, which limits the difficulty of the rotary compressor to achieve larger Compression ratio, therefore, most rotary compressors are used in air conditioning conditions.

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