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Scroll compressors in refrigeration systems. Scroll compressor. Copeland ZF EVI High Efficiency Scroll Compressors

Scroll compressors are single-shaft positive displacement machines. As is known, machines of this operating principle are reversible; can work practically without changing the design, both as compressors and as motors (expanders or expanders.

The idea of ​​such a machine has been known for more than a hundred years, but it was only in the 80s of the twentieth century that it was possible to realize it and bring it to industrial production and widespread use. The reason is the same as in the development of screw compressors, there was not enough precision equipment to manufacture such a part shape as spirals.

Currently in refrigeration scroll compressors are used in domestic and transport air conditioners, heat pumps, refrigerating machines low and medium power up to 50 kW. But calculations show that the refrigeration capacity of scroll compressors can be increased to 100 kW or more as their design and manufacturing technology improve.

28 Classification of scroll compressors

Scroll compressors are classified as follows: oil-filled; with the injection of a drip liquid (for example, a refrigerant); dry compression.

And, of course, one- and two-stage with a different arrangement of steps in relation to the engine.

Depending on the type of gas, power and other conditions: tight, glandless, stuffing box.

According to the type of spirals used: with involute spirals, with Archimedes spirals, with piecewise circular, etc.

The division of scroll compressors into vertical and horizontal is essential. In the latter, shaft 1 is located horizontally (see Figure 65). In horizontal scroll compressors, such as a transport air conditioner with a parallel arrangement of the shaft and the longitudinal axis of the vehicle, it is more difficult to ensure the reliable operation of the compressor lubrication system.

29 Advantages and disadvantages of scroll compressors

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 bearings;

3.Good balance; slight change in torque on the compressor shaft; low gas speeds in the machine - all this ensures the machine runs with a low noise level.

4. Speed ​​- the number of revolutions of the compressor shaft 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 a high frequency of the shaft, the gas velocities are small.

7. Absence of valves on suction, and often on discharge;

8. A scroll compressor, like a screw compressor, can operate in a “recharging” cycle;

9. The scroll compressor, like all positive displacement compressors, can operate on any refrigerant, on any gas, and even with drip liquid injection.

Compared with reciprocating compressors of the same capacity, the scroll compressor has the following advantages:

The disadvantages of scroll compressors include the following:

1. Spiral machines require new parts for mechanical engineering - spirals, for the manufacture of which they need milling machines with CNC.

2. A complex system of forces acts on the movable 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 the scroll compressor will look the same as that of the screw compressor, with possible gas undercompression and overcompression, i.e. with additional losses.

The main element of any is the compressor. It serves to ensure the movement of the refrigerant in the system and create a pressure difference.

Relatively recently, scroll compressors have been used in refrigeration. 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 scroll. The principle of operation of a refrigeration scroll compressor is based on the coordinated rotation of one scroll relative to another.

The principle of operation of the spiral refrigeration compressor.

In a scroll compressor, the refrigerant vapor is compressed between two scrolls.

One spiral is motionless, the second one rotates around it. Moreover, this movement has a difficult trajectory. The electric motor, located in one hermetic casing of the compressor, does the work - it rotates the shaft, at the end of which there is an eccentrically mounted spiral. Rotating, the movable scroll rolls over the walls of the fixed scroll, sliding over the oil 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 suction vapors of the refrigerant in the zone of a larger volume of compressible gas, the spirals gradually compress them as the working zone approaches the center, as its volume decreases. Accordingly, the maximum gas pressure is reached in the center of the spirals, which then enters the condenser through the compressor discharge line. In a scroll compressor, during operation, vapor compression occurs continuously, since the contact point of the spirals is not one and several working compression zones are formed. Hermetic scroll compressor motors are cooled by suction refrigerant vapor.

Consider the device of a scroll refrigeration compressor on the example of products . The device of compressors of other manufacturers is similar. The main components of the scroll compressor are shown in Figure 2.


Figure 2. The structure of the scroll refrigeration compressor.

Due to its design, the number of mutually rubbing parts in a scroll compressor is much 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 the efficiency of work.

Due to the fact that in the process of gas compression several working zones are formed simultaneously, refrigerant vapors are injected more evenly than in reciprocating compressors and with smaller working volumes, which reduces the load on the electric motor.

To increase the efficiency of work, much attention in scroll compressors is paid to sealing the side and end surfaces of the contacts of the scrolls, to reduce gas leakage 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.

The performance of scroll compressors can be controlled by means of frequency converters by changing the speed of rotation of the shaft. 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 run idle, without forming any working compression zones at all.

To date, scroll refrigeration compressors are manufactured and supplied to Russia and, accordingly, to Chelyabinsk by such world-famous companies as, Danfoss Performer , .

Rice. 2. 26. Scroll compressor Performer (Danfoss). 1 - movable spiral; 2 - fixed spiral; 3 - terminal box; 4 - motor protection; 5 - sight glass; 6 - suction; 7 - oil pump; 8 - electric motor; 9 - injection; 10 - protection against reverse rotation; 11 - check valve.

The electric motor is located in the lower part of the compressor, the shaft with the help of an eccentric provides the elliptical movement of the movable scroll inserted into the fixed scroll installed in the upper part of the compressor. The suction gas enters the compressor through the suction pipe, flows around the motor casing and enters it through the holes in the bottom of the casing (Fig. 2.26). The oil in the refrigerant vapor, as a result of the rotation of the oil-refrigerant mixture under the action of centrifugal forces, is separated from it and flows down to the bottom of the compressor crankcase. The steam passes through the electric motor, ensuring complete cooling of the compressor in all modes of operation. After passing through the electric motor, the steam enters the scroll elements of the compressor, which are located at the top of the compressor above the electric motor. The working cycle is completed in three revolutions of the shaft: the first revolution is suction, the second revolution is compression, the third revolution is injection. Immediately above the outlet channel of the fixed scroll is a non-return valve. It prevents the compressor from backflow of gas after it is switched off. After passing the check valve, the gas leaves the compressor through the discharge pipe.

The efficiency of scroll compressors is largely determined by the amount of internal radial and axial gas leakage during the compression process. Radial leaks occur between the contacting side surfaces of the spirals, axial - between the upper end of one spiral and the base plate of the other (Fig. 2. 24). Leaks lead to an increase in the power consumption of the compressor, a decrease in its cooling capacity and efficiency.

The main difference between this compressor and other scroll compressors is the principle of sealing the scroll elements. A common way to provide a radial seal is to create a tight contact by pressing the movable scroll on the stationary one under the action of centrifugal force. However, freshly manufactured compressors create an effective homogeneous seal only after a "burning-in" period, during which the necessary contact is established between the surfaces. Touching the side surfaces of the scrolls is a prerequisite for such compressors.

Danfoss uses the so-called “controlled orbiting” in its Performer compressors, which means that the scrolls move along a fixed path without contact between the movable and fixed scrolls under any compressor operating conditions.

Rotation controlled Performer compressors must have ultra-precise scroll profiles to achieve guaranteed sealing. The side surfaces of such spirals never come into contact with each other, and a thin film of oil sealing the gap provides lubrication of the spirals without friction and wear of their surface.

When creating an axial seal, some compressor manufacturers press the movable scroll against the stationary one using the pressure of the compressible gas to seal.

In Performer compressors, dynamic contact between the upper end of the moving scroll and the base plate of the fixed scroll is maintained by a floating seal (fig. 2.27).

Rice. 2.27. Rotation Controlled Performer Scroll Floating Seal:

1 - base plate; 2 - gap between the end face and the base plate; 3 - floating seal; 4 - spiral; 5 - oil film preventing seal gas leakage; 6 - gas high pressure

This sealing element is located in a groove cut in the upper end of the movable spiral (Fig. 2.27). The pressurized gas presses on the floating seal from below and forces it against the scroll base plate, creating dynamic contact when the compressor is running. The pressing forces are very low, which, combined with a small contact area, reduces friction and increases compressor efficiency.

characteristic feature of these compressors is that they run dry, even if the pressure in the system is unbalanced. This is done by setting check valve on the discharge line, which closes when it stops. Under these conditions, only the gas compressed in the compressor to the valve installation point returns to the crankcase, while passing through the spirals. This equalizes the internal pressure. When the compressor stops, the two scrolls open both vertically and horizontally. When starting up again, the compressor is not under load, since the pressure increase occurs gradually. The scroll compressor has a safety valve that opens when the pressure exceeds 28 bar and bypasses the refrigerant from the discharge cavity to the suction one.

Oil in scroll compressors serves only to lubricate the bearings and the floating sealing ring. Lubrication of the spirals is not required due to the low speed of rotation and the friction force at each point of contact. The oil content of the oil-refrigerant mixture is sufficient to provide the necessary lubrication, so that the oil is not affected by high temperatures which can lead to deterioration of the oil characteristics over time. Another positive feature is the high ability to resist oil carryover during start-up.

Questions for self-control in chapter 2.

What is the difference between direct and indirect compressors? 2. What is the structural difference between a single-acting compressor and a double-acting compressor? 3. What kind of water hammer protection device does the compressor have? 4. What is the difference between a piston sealing ring and an oil scraper? 5. How is the compressor oil seal lubricated? 6. What is the purpose safety valve in the compressor? 7. How is the oil carried away by refrigerant vapor returned to the compressor crankcase? 8. Why does a compressor running on ammonia have a greater cooling capacity than one running on R22? 9. How can I change the cooling capacity of a refrigeration compressor? 10. How does compression work in a screw compressor? 11. Why does a screw compressor experience energy losses when the pressure at the end of compression does not match the discharge pressure? 12. Why does the refrigeration capacity of a screw compressor change when the spool is moved? 13. What are the advantages and disadvantages of a screw compressor compared to a piston compressor? 14. What are the advantages of scroll compressors? 15. Seals for scroll compressors. 16. The principle of operation of scroll compressors. 17. What is the "pinched" volume in screw compressors?

Literature for chapter 2.

1. Baranenko A.V., Bukharin N.N., Pekarev V.I., Timofeevsky L.S. Refrigeration machines - St. Petersburg: Polytechnic, 2006.-944 p.

2. Quick selection of automatic controllers, compressors and condensing units. Catalog. Danfoss. 2009.-234s

3. Ladin N.V., Abdulmanov Kh.A., Lalaev G.G. Ship refrigeration units. Textbook. Moscow, Transport, 1993.-246 p.

4. Shvetsov G. M., Ladin N. V. Ship refrigeration units: Textbook for
universities. - M.: Transport, 1986. - 232 p.

Scroll compressors are positive displacement compressors, i.e. compression of the refrigerant occurs by reducing the volume in which the refrigerant is located. This is a completely new type of compressor, which is now increasingly used in air conditioning systems and refrigeration machines with a cooling capacity of 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 an eccentric movement. All processes inherent in volumetric compressors (for example, a reciprocating compressor) - suction, compression, discharge - are realized in cavities, formed between the surfaces of the spirals. The principle of operation of the scroll compressor is shown in fig. 5.21. Distinctive feature scroll compressor is the lack of suction and discharge valves and virtually no

dead volume. In the process of suction (Fig. 5.21, a), the refrigerant from the evaporator fills the expanding cavity between the fixed (black line) and mobile (gray line) scroll compressors. The direction of movement of the refrigerant 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). In the process of moving the movable spiral, the cut-off volume moves to the central part of the spirals (Fig. 5.21, c, d), while there is a decrease in volume and, accordingly, an increase in pressure. Having reached the central part, the compressed refrigerant is supplied to the discharge pipe (position d) and then to the chiller condenser.

The number of turns of the spirals, their shape and the radius of movement of the movable spiral are chosen 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 may have a vertically located electric motor housed in a sealed casing. In the upper part, fixed and movable spirals are installed. The compressor is equipped with nozzles for connection to the suction lines (to the evaporator) and discharge lines (to the condenser).

The absence of reciprocating parts significantly reduces compressor vibration and noise levels. High efficiency and ease of maintenance during operation contribute to an increase in the number of compressors of this type for refrigeration and air conditioning.

Advantages:

1. Lack of suction and discharge valves.

2. Virtually 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. Small weight and dimensions.

Disadvantages:

1. Complex technological production.

Oil-free scroll compressors– equipment of the "latest generation", capable of ensuring the complete absence of compressed air oil impurities.

The scroll air compressor is a single-shaft positive displacement compressor. The working bodies of this device are two spirals - movable and fixed, inserted into each other. During the operation of the unit, the moving spiral moves in a circular orbit around the fixed one. It should be noted that the movable spiral does not rotate around its own axis. This movement is provided to this element 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 a constant uniform compression of the air. To reduce the duration of the starting torque, the device is equipped with a floating seal.

Thanks to design feature, this type of oil-free air compressor is distinguished by its reliability and the ability to evenly distribute the load on the scroll elements of the equipment.

Prona LLC offers you to buy oil-free scroll compressors, as well as accessories, spare parts and expendable materials to them. We carry out not only sales, but also service.

Our site presents oil-free scroll compressors known in the world. Russian market manufacturers. The catalog contains air collectors trademarks Chicago Pneumatic and Remeza.

Scope of equipment

Are intended for use at those enterprises where use of the polluted compressed air is inadmissible.

Thanks to a 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 have been actively used in the food industry, in the manufacture of household and industrial systems air conditioning, as well as in the manufacture of refrigeration units.

Benefits of oil-free scroll compressors

The high demand for this type of compressors is easily explained by their characteristics and excellent performance:

  • high coefficient of performance;
  • low noise level;
  • reliability in work;
  • low vibration level;
  • high level productivity;
  • excellent performance characteristics.

Where to buy scroll compressors?

OOO "Prona" offers you to purchase scroll compressors in Moscow. It is the official representative in our country of many world leaders in the production of compressor equipment, we are pleased to offer you our services of supply and after-sales service. 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 manufacturer of the equipment. We carry out delivery across all Russia.