Rotary compressor for refrigerating gas and related procedure

Abstract

 A rotary compressor for compressing a refrigerating gas, comprising: a stator (14) defining a cylindrical compression chamber (15) in which an eccentrically arranged rotor (16) provided with radial vanes (17) is located; the refrigerating gas is fed into and discharged from the compression chamber (15) through a same end wall (20) of the compression chamber (15) so that the latter is kept in direct heat-exchange contact with the outside; a quantity of refrigerated gas is admitted to the compression chamber (15) to improve the efficiency of the compressor.

Description

[0001] This invention relates to rotary compressors for refrigerating units as well as to a method for compressing refrigerating gas using a compressor of the above-stated kind.

[0002] As is known, traditional refrigerating units employ piston type compressors which draw in the refrigerating gas and compress it at a pre-set pressure value before returning it to the refrigerating unit circuit.

[0003] In general a piston type compressor is an extremely complex machine because of its numerous moving parts and, consequently, it is liable to failures and breakage during operation. Accordingly, attempts have been made to substitute the traditional piston type compressor with rotary compressors since these offer enormous advantages in design, operational, and cost terms. However, the use of rotary compressors imposes limits from the standpoint of their efficiency, design, and use. The reason is that owing to their particular structures, traditional rotary compressors must be designed specifically for the planned working conditions and they cannot be adapted to working conditions differing from those planned for the refrigerating unit with which the compressor is to be used.

[0004] This is partly due to the fact that in traditional rotary compressors the stator is entirelly surrounded by the compression chamber for the fluid (air or oil) which negatively affects the internal heat exchange of the machine leading to a loss or reduction in efficiency caused by the resulting increase in the specific volume of the gas drawn in. Moreover, any repair or maintenance work on traditional rotary compressors is extremely complicated and cannot always be carried out in situ so that often it is necessary to remove or substitute the entire compressor.

[0005] An object of this invention is to provide a rotary compressor for refrigerating units that is simple in design, which can easily be adapted to different working conditions and which allows greater compression efficiency because overheating of the fluid in the compression chamber is substantially avoided as a result of an appropriate heat exchange.

[0006] A further object of this invention is to provide a rotary compressor for refrigerating units, as defined above, by means of which it is possible to implement a compression method which provides for mixing with refrigerated gas fed in at a pre-set point in the compression cycle, in order to increase the compressor efficiency.

[0007] Another object of the invention is to provide a rotary vane compressor for the above-stated use that is simple in design and which is easy to maintain.

[0008] These and other objects are obtained through a rotary compressor and a compression method in accordance with the main claims 1 and 9.

[0009] The invention will be described in greater detail below with reference to the attached drawings, provided by way of example, in which:

Fig. 1

is a longitudinal cross-sectional view of a rotary compressor, along the line 1-1 in figure 3, forming part of a refrigerating unit which is represented diagrammatically;

Fig. 2

is a longitudinal cross-secional view of the compressor along the line 2-2 in figure 3;

Fig. 3

is a cross-sectional view along the line 3-3 in figure 1.

[0010] Figure 1 shows a rotary compressor according to the invention, indicated overall with reference number 10, forming part of a refrigerating plant which is represented diagrammatically. This plant comprises a refrigerator unit GF connected to the delivery or outlet 11 of the compressor 10 through an oil separator SO and to the intake inlet 12 as shown. The reference RO in figure 1 indicates a reserve tank for lubricating-oil connected to the inlet of a self-priming pump 13 which, through a heat exchanger SC, feeds the lubricating oil to an oil inlet 10 in the compressor 10. It is intended that the simplified diagram provided here of the refrigeration plant serve merely to exemplify and illustrate the mode of operation and characteristics of the compressor according to the invention.

[0011] The rotary compressor 10, unlike traditional ones, comprises a simple external casing 14 defining a cylindrical gas-compression chamber 15 that is in direct heat-exchange contact with the outside. Inside the chamber 15, an eccentrically positioned rotor 16 comprising radially moving vanes 17 rotates, just as in a traditional air compressor. The rotor 16 is mounted on a shaft 18 rotatingly supported, in a leaktight arrangement, by a pair of end walls 19 and 20.

[0012] Below the casing 14 and positioned longitudinally to it there is an intake manifold 21 which on one side communicates directly with the intake inlet 12 in the end wall 20, and on the other communicates with the compression chamber 15 through a passage 22 in the other end wall 19. The inlet 12 in the end wall 20 in its turn also communicates directly with the compression chamber 15 so that the incoming gas flow is split in two and fed axially to the two ends of the compression chamber.

[0013] On the opposite side to that of the intake manifold 21, the compression chamber 15 communicates through a plurality of passages or openings 23 with a delivery manifold 24 which runs longitudinally to the compressor casing 14. This manifold communicates in turn with the compressor outlet or delivery opening 11, which formed in the same end wall 20 as is the above-mentioned intake opening 12.

[0014] In addition to the intake opening 12 for the fluid to be compressed and the outlet opening 11 for the compressed fluid, the end wall 20 of the compression chamber also comprises the lubricating-oil circulation pump 13. In this way, the end wall itself incorporates three basic functions of the compressor and is, for that matter, easy to remove and replace without there being any need to remove or work on the entire compressor.

[0015] The outlet of the pump 13 is connected via the heat exchanger SC to the inlet 10 of a manifold 25 provided with injection holes 26 that feed the lubrication oil directly to the compression spaces 17a defined between the contiguous vanes 17 of the rotor. The oil manifold 25 is located in a position that is angularly spaced between the manifolds 21 and 24 and is additionally connected, as shown, to oil channels as required in the end walls 19 and 20 to enable their lubrication.

[0016] Finally, in figure 3 reference number 27 indicates a feed hole for pre-refrigerated gas FS drawn off as required from the refrigerator unit circuit shown in diagrammatic form.

[0017] The admission into the compression chamber of pre-refrigerated gas, that is gas at a temperature below that of the gas being compressed, considerably improves the efficiency of the compressor. Even though the gas requires a greater driving force for its compression, overall it improves the cycle efficiency at low temperatures by an efficiency which in certain cases is as much as 10-15% above that of a traditional compressor.

[0018] It is preferable that the refrigerated fluid is admitted to the compressor chamber at a position in which the existing pressure at that moment in the space between the vanes corresponds or is close to the geometric mean between the intake pressure in the manifold 21 and the delivery pressure in the manifold 24.

[0019] From what has been stated and shown it is therefore evident that a rotary vane compressor for refrigerator units is provided, characterised by a compression chamber in direct heat-exchange contact with the outside, in which the intake and the delivery of the fluid take place axially and on the same side of the compressor through a same end wall of the chamber 15. In this way, along with a more simplified design, the compressor operating efficiency is improved due to the total elimination of any possible causes of internal heat exchange so that compression conditions are closer to being adiabatic than polytropic. Furthermore, as a result of using a self-priming pump for the lubricating-oil circulation, mechanically connected to the rotor and lodged in the end wall that incorporates the openings for both intake and delivery, the design and operation of the compressor is notably simplified since work for repairs and inspections need be carried out only on one side.

[0020] It is intended that what has been stated and shown in the attached drawings is to serve purely as an example without any restrictive implications for the compressor for refrigerating units and the procedure claimed.

Claims

1. A rotary compressor for refrigerating units comprising a cylindrical casing (14) having a compression chamber (15) in which a radial-vane rotor (16) eccentrically rotates, the compressor (10) comprising pumping means (13) for the circulation and injection of lubricating oil inside the compression chamber (15), an intake manifold (21) connected to an inlet (12) for the fluid and a delivery manifold (24) connected to an outlet opening (11) for the fluid, characterised by the fact that said compression chamber (15) is in direct heat-exchange contact with the outside, and by the fact that said intake opening (12), said delivery opening (11) and said lubricating-oil circulation pumping means (13) are located in one end wall (20) of the compression chamber (15).

2. A rotary compressor as claimed in claim 1, characterised by the fact that said lubricating-oil pumping means comprise a self-priming pump (13) connected to the shaft (18) of the rotor (16).

3. A rotary compressor as claimed in claim 1, characterised by the fact that said intake manifold (21) and said delivery manifold 24 are positioned longitudinally and externally to the compressor casing (14).

4. A rotary compressor as claimed in claim 3, characterised by the fact that said inlet opening (12) communicates with both ends of the compression chamber (15) directly and by way of the said intake manifold (21) respectively.

5. A rotary compressor as claimed in claim 1, characterised by the fact that it comprises a third manifold (25) for feeding lubricating oil, said third manifold (25) being provided with apertures (27) for injecting oil into the spaces (17a) defined by contiguous vanes (17), and being positioned in an intermediate angular position between the aforesaid intake and delivery manifolds (21, 24).

6. A rotary compressor as claimed in claim 1, further characterised by means (27) for feeding refrigerated fluid into the compression chamber (15) at a space (17a) defined between contiguous vanes (17) of the rotor (16).

7. A rotary compressor as claimed in claim 6, characterised by the fact that said feeding means (FS, 27) for the refrigerated fluid comprise a feed opening (27) provided in an angular position close to the delivery manifold (24).

8. A rotary compressor as claimed in claim 7, characterised by the fact that said opening (27) for feeding the refrigerated gas into the compressor chamber (15) is provided in a position in which the pressure of the gas being compressed is defined by the geometric mean between the intake pressure and delivery pressure of the compressor.

9. A method for compressing refrigerating gas using a rotary compressor (10) of the kind comprising a cylindrical compression chamber (15) in which a radial-vane rotor (16) eccentrically rotates, and in which the refrigerating gas to be compressed is fed into said chamber (15) to be compressed in the spaces defined by contiguous vanes (17), characterised by axially feeding and then delivering said refrigerating gas with respect to the compression chamber (15) at a same end wall (20) of the compression chamber (15) and by mixing the refrigerating gas while it is being compressed with a quantity of refrigerated gas at a temperature lower than that of the gas in the compression space (17a) of said compression chamber (15).

10. A method as claimed in claim 9, characterised by the fact that said refrigerated gas is fed into the compression chamber (15) in an angular position in which the pressure is equal or close to the geometric mean between the intake pressure and the delivery pressure of the compressor.

11. A method as claimed in claim 9, in which said compressor (10) is connected to a refrigerating unit (GF) characterised by the fact that said refrigerated gas is pre-refrigerated gas drawn off from said refrigerating unit (GF).

Drawing