Scroll compressors are classified as positive displacement compressors, i.e. Refrigerant compression occurs by reducing the volume in which the refrigerant is located. This is absolutely new type compressors, which is now increasingly used in air conditioning systems and refrigeration machines cooling capacity up to 40 kW.
Structurally, the working element of a scroll compressor consists of two spirals nested one inside the other (Fig. 5.20). One of the spirals is installed motionless, and the second makes eccentric movement. All processes inherent in volumetric compressors (for example, a piston compressor) - suction, compression, discharge - are realized in the cavities formed between the surfaces of the spirals. The operating principle of a scroll compressor is shown in Fig. 5.21. Distinctive feature scroll compressor is the absence of suction discharge valves and virtually no
dead volume. During the suction process (Fig. 5.21, a), the refrigerant from the evaporator fills the expanding cavity between the stationary (black line) and movable (gray line) scroll compressors. The direction of refrigerant movement is shown in the figure by an arrow. Further movement of the movable spiral cuts off the volume filled with refrigerant from the suction line (Fig. 5.21, b). During the movement of the movable spiral, the cut-off volume moves to the central part of the spirals (Fig. 5.21, c, d), while the volume decreases and, accordingly, the pressure increases. Having reached the central part, the compressed refrigerant is supplied to the discharge pipe (position d) and then to the condenser of the refrigeration machine.
The number of turns of the spirals, their shape and the radius of movement of the movable spiral are selected so that at the same time the working process of the compressor is realized in six cavities and the process of refrigerant injection is almost continuous (Fig. 5.21, e).
Structurally, a scroll compressor can have a vertically located electric motor housed in a sealed casing. Fixed and movable spirals are installed in the upper part. The compressor is equipped with pipes for connection to the suction (to the evaporator) and discharge (to the condenser) lines.
The absence of reciprocating moving parts significantly reduces the level of compressor vibration and noise. High efficiency and ease of maintenance during operation contribute to an increase in the number of compressors of this type for refrigeration machines and air conditioners.
Advantages:
1. Lack of suction and discharge valves.
2. There is practically no dead volume.
3. The injection process is almost continuous.
4. Low vibration and noise.
5. High efficiency and easy maintenance.
6. Stability of operation when mechanical impurities, wear products or liquid refrigerant enter the compression zone.
7. Low weight and dimensions.
Flaws:
1. Complex technological production.
Scroll compressor- a device for compressing gas (air or refrigerant), by reducing its volume in the chambers, formed by surfaces spirals.
Scroll compressors are used in air conditioning, refrigeration, heating, automobiles, cryogenic and refrigeration systems, and as vacuum pumps.
There are several standard designs scroll compressors.
The most common option is use of two spiral elements, installed with eccentricity. One of these elements is movable, the other is not.
A scroll compressor is shown in the figure.
The sealed housing houses an electric motor that rotates the shaft. A fixed spiral is installed in the upper part of the body. A movable spiral is installed on the shaft, which can move along guides making a complex movement relative to the fixed spiral.
As a result of movement between the spirals, chambers (pockets) are formed, the volume of which decreases with further movement, and as a result, the gas located in these pockets is compressed.
The operating principle of such a compressor is shown in the video:
Also found compressors with two moving scrolls, committing rotational movement relative to different axes. As a result of the rotation of the spiral elements, chambers are also formed, the volume of which decreases during rotation.
To a greater extent, the compressor differs from the options presented above, in which the rigid element is made in the form Archimedean spiral affects flexible elastic tube. The principle of operation of such a compressor is similar to a peristaltic pump. Such scroll compressors usually filled with liquid lubricant to reduce wear on the flexible tube and dissipate heat. Such compressors are often called hose.
In scroll compressors, a suction valve is not needed, because the movable spiral itself cuts off the working chamber from the suction channel. A dynamic valve may be installed in the discharge line of a scroll compressor, which prevents backflow and, as a result, rotation of the scroll under the action when the engine is turned off. It should be taken into account that the dynamic valve creates additional resistance in the discharge line.
Dynamic valves are installed in the discharge line of Copeland medium and low temperature refrigeration compressors.
Scroll compressor runs smoother, and more reliable than most other volumetric machines. Unlike pistons, the moving scroll can be perfectly balanced, minimizing vibration.
The absence of dead volume in scroll compressors results in increased volumetric efficiency.
Scroll compressors usually have less pulsation than single-piston machines, but more pulsation than multi-piston machines.
Scroll compressors have fewer moving parts, compared to piston engines, which, theoretically, ensures their greater reliability.
Scroll compressors are generally very compact and do not require spring suspension due to their smooth operation.
Scroll compressors are sensitive to contamination of the pumped gas, because... fine particles may settle on the surface of the spiral, which will not ensure sufficient tightness of the working chamber.
A scroll compressor must rotate in one direction only.
For a long time, scroll compressors were produced without the ability to adjust performance. If necessary, reduce the feed using frequency regulation drive electric motor, or bypassing part of the gas from the discharge line to the suction line.
Currently adjustable scroll compressors are manufactured by Emerson. In these compressors, the distance between the axes of rotation of the scrolls can be changed; if necessary, this distance can be chosen such that no chambers will form between the spiral elements, which means the compressor supply will be wound 0. By alternating two different operating states (idle and working stroke) using an electronic control, the required performance can be achieved.
The main advantages of scroll compressors are:
1.High energy efficiency; their effective efficiency reaches 80-86%;
2.High reliability and durability, determined by the durability of the bearings;
3.Good balance; slight change in torque on the compressor shaft; low gas speeds in the car - all this ensures the machine runs with a low noise level.
4. Speed - the number of revolutions of the compressor shaft is from 1000 to 13000, and this range is expanding.
5. No dead volume, low leakage rate, and, therefore, higher indicator efficiency; the gas sucked in by the compressor does not come into contact with the hot walls of the compressor parts;
6. The processes of suction, compression and discharge are “stretched” along the angle of rotation of the shaft and therefore, even at high shaft frequencies, gas velocities are low.
7. Lack of valves on the suction, and often on the discharge;
8. A scroll compressor, like a screw compressor, can operate in a cycle with “recharging”;
9. The scroll compressor, like all compressors of the positive displacement principle, can operate on any refrigerant, on any gas, and even with droplet liquid injection.
Compared to piston compressors of the same power, a scroll compressor has the following advantages:
1. More high efficiency- by 10-15%;
2. Higher feed rate - by 20-30%;
3. Smaller sizes - by 30-40%;
4. Less weight - by 15-18%;
5. The noise level is lower by 5-7 dBA;
6. There are no parts that often fail - piston rings, valves.
7. Can work with droplet liquid injection, for example, in an oil-filled version, like a screw one;
8. Fewer parts, lower production costs.
The disadvantages of scroll compressors include the following:
1. Spiral machines require new spiral parts for mechanical engineering, for the manufacture of which milling machines with CNC.
2. A complex system of forces acts on the moving spiral: axial, centrifugal, tangential, requiring competent calculation and balancing, and, consequently, balancing of the rotor.
3. If there is no discharge valve, then the theoretical indicator diagram of a scroll compressor will be the same in appearance as that of a screw compressor, with possible undercompression and overcompression of the gas, i.e. with additional losses.
The main element of any is the compressor. It serves to ensure the movement of refrigerant in the system and create a pressure difference.
Relatively recently, scroll-type compressors began to be used in refrigeration technology. They mainly work as part of air conditioning systems, heat pumps, medium and high temperature refrigeration units.
The working element of a scroll compressor is a spiral. The operating principle of a refrigeration scroll compressor is based on the coordinated rotation of one spiral relative to another.
Operating principle of a scroll refrigeration compressor.
In a scroll compressor, refrigerant vapor is compressed between two spirals.
One spiral is stationary, the second rotates around it. Moreover, this movement has a difficult trajectory. The electric motor, located in one sealed compressor housing, does the work - it rotates the shaft, at the end of which there is an eccentrically installed spiral. While rotating, the movable spiral rolls along the walls of the fixed spiral, sliding along the oily film. The contact points of the spirals gradually move from the edge to the center, and they are located on each turn of the working element. Capturing the sucked-in refrigerant vapors in the area of a larger volume of compressed gas, the spirals gradually compress them as they approach working area towards the center, as its volume decreases. Accordingly, in the center of the spirals the maximum gas pressure is achieved, which then enters the condenser through the compressor discharge line. In a scroll compressor, during operation, vapor compression occurs continuously, since there is more than one point of contact between the spirals and several working compression zones are formed. The electric motors of hermetic scroll compressors are cooled by suction refrigerant vapors.
Let's look at the design of a spiral refrigeration compressor using the example of a product . The design of compressors from other manufacturers is similar. The main components of a scroll compressor are shown in Figure 2.
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Figure 2. Design of a scroll refrigeration compressor.
Due to its design, the number of mutually rubbing parts in a scroll compressor is significantly less than what theoretically indicates its reliability.
Also, the advantages of the design include the absence of dead harmful space in the compression zone, which increases operating efficiency.
Due to the fact that several working zones are formed simultaneously during the gas compression process, refrigerant vapors are pumped more evenly than in piston compressors and with smaller working volumes, which reduces the load on the electric motor.
To increase operating efficiency, much attention in scroll compressors is paid to sealing the side and end surfaces of the contacts of the spirals to reduce gas flows between adjacent compression zones.
Scroll compressors were originally designed and found their greatest application in the field of high- and medium-temperature refrigeration systems - air conditioning, chillers, heat pumps. But they are also used in low-temperature refrigeration units, thanks to the technology of injecting a small amount of refrigerant into the center of the spirals during operation.
It is possible to regulate the performance of scroll compressors using frequency converters by changing the shaft rotation speed. In addition, the manufacturer of scroll compressors Copeland , has developed a technology for adjusting performance by changing the distance between the spirals during rotation. This technology allows the scroll compressor to operate idle, without forming any working compression zones at all.
Today, spiral refrigeration compressors are produced and supplied to Russia and, accordingly, to Chelyabinsk such worldwide well-known companies, How, Danfoss Performer , .
Oil-free scroll compressors– “latest generation” equipment capable of ensuring complete absence of compressed air oil impurities.
The air scroll compressor is a single-shaft positive displacement compressor. The working parts of this device are two spirals - movable and fixed, inserted into each other. During operation of the unit, the movable spiral moves in a circular orbit around the stationary one. It should be noted that the movable spiral does not rotate around its own axis. This movement of this element is provided by a special anti-rotation device, as well as a shaft with an eccentric rotating in a given direction. This design contributes to a continuous reduction in the volume of the cavities, which ensures constant uniform compression of air. To reduce the duration of the starting torque, the device is equipped with a floating seal.
Thanks to design feature, this type oil-free air compressors are distinguished by their reliability and ability to evenly distribute the load on the spiral elements of the equipment.
The Prona LLC company offers you to buy oil-free scroll compressors, as well as components, spare parts and Consumables to them. We provide not only sales, but also service.
Our website presents oil-free scroll compressors from well-known Russian market manufacturers. The catalog contains air collectors brands Chicago Pneumatic and Remeza.
Designed for use in those enterprises where the use of contaminated compressed air is unacceptable.
Thanks to the large number undeniable advantages, scroll compressors have found their wide application in the manufacture of various refrigeration units, as well as in air conditioning systems.
From the moment of their invention and introduction into production, these devices began to be actively used in Food Industry, in the manufacture of household and industrial systems air conditioning, as well as in the manufacture of refrigeration units.
The high demand for compressors of this type is easily explained by their characteristics and excellent performance:
Prona LLC invites you to purchase scroll compressors in Moscow. Is official representative In our country there are many world leaders in the production of compressor equipment, we are pleased to offer you our supply and maintenance services. All products presented by us have the necessary certificates and guarantees. The price of a scroll compressor depends on the characteristics you need and the equipment manufacturer. We deliver all over Russia.
