Spindle compressors for compression refrigeration machines

Abstract

Spindle compressor as a 2-shaft rotary positive displacement machine operating in a working chamber without operating fluid for conveying and compressing gaseous conveying media, primarily for compression refrigeration machines, with two spindle rotors (2, 3) in a surrounding compressor housing (8) with an inlet (10) and an outlet collection chamber (13), wherein a multi-stage spindle compressor (1) is used as the refrigerant compressor, the compressor housing (8) and the spindle rotors (2 and 3) of which are cooled via a partial flow branch (25) of liquid refrigerant (39) from the main refrigerant flow circuit (24), characterized in that the heat of compression is dissipated from the compressor housing (8) via refrigerant evaporation (9),wherein liquid refrigerant is directed via a partial flow branch (25) through a regulating element (18) to the housing refrigerant evaporator (9) and the refrigerant vapor exiting the housing refrigerant evaporator (9) through the openings (19) enters the collection chamber (20), and that this refrigerant vapor flows via passage (21) with regulating element into the inlet chamber (10) of the spindle compressor (1).

Description

[0001] Dry-running compressors are gaining increasing importance in industrial compressor technology. This is because stricter environmental regulations, rising operating and disposal costs, and increased demands on the purity of the pumped medium are leading to the growing replacement of traditional wet-running compressors, such as liquid ring compressors, rotary vane pumps, and oil- or water-injected screw compressors, by dry-running machines. These machines include dry screw compressors, claw pumps, diaphragm pumps, piston pumps, scroll compressors, and rotary lobe pumps. However, these machines still do not meet today's requirements for reliability, robustness, size, and weight while maintaining a low price and satisfactory efficiency.

[0002] To improve this situation, the well-known dry-running spindle compressors are a suitable option because, as typical two-shaft positive displacement machines, they achieve high compression capacity simply by creating the necessary multi-stage design as a so-called "feed screw" by connecting several sealed working chambers in series. This is achieved through the number of turns per displacement rotor, without requiring any operating fluid in the working chamber. Furthermore, the non-contact rotation of the two counter-rotating spindle rotors allows for a higher rotor speed, thus increasing both the nominal pumping speed and the volumetric efficiency relative to the compressor's size.Dry-compressing spindle machines can be used for both vacuum and overpressure applications, although the power requirement is naturally significantly higher in overpressure applications because, in the overpressure range with final pressures well above 2 bar (absolute) up to 15 bar and even higher, significantly larger pressure differences have to be overcome.

[0003] DE 198 39 501 A1 discloses a dry-compressing screw spindle pump as a two-shaft positive displacement machine for conveying and compressing gases with a parallel arranged pair of rotor spindles in a closed pumping chamber with inlet and outlet as well as lateral boundaries for supporting the rotors by means of rolling or similar bearings.

[0004] DE 10 2012 011 820 A1 discloses a dry-compressing 2-shaft rotary positive displacement machine for conveying and compressing gases for applications in vacuum and overpressure.

[0005] WO 2011 / 023 513 A2 discloses dry-compressing 2-shaft rotary positive displacement machines as screw spindle pumps for conveying and compressing gases, wherein the spindle rotors have internal rotor cooling.

[0006] German patent DE 10 2013 009 040 A1 describes how a dry-running screw compressor achieves both a high internal compression ratio and a high number of stages while simultaneously minimizing internal leakage between the multiple series-connected working chambers between the conveying gas inlet and outlet, by using non-parallel axes of rotation for the two screw rotors. In compression refrigeration systems, compressor technology for this performance range is still dominated by screw compressors, which require an operating fluid in the working chamber, with the desired capacity adjustment usually achieved via complex control valves. Furthermore, higher network operating pressures often require two series-connected compressors, and the efficiency is only moderately satisfactory. This situation needs improvement.

[0007] The object of the present invention is to operate the refrigerant compressor of a compression refrigeration machine without operating fluid in the working space with improved efficiency and increased reliability even for high network operating pressures using only one compressor machine, while simultaneously offering highly flexible and simple power adjustment, at least partially hermetically sealed construction, and at the same time the lowest possible noise level.

[0008] According to the invention, this problem is solved by a spindle compressor according to claim 1. The refrigerant compressor can be designed as a multi-stage spindle compressor machine (1) which, preferably with non-parallel axes of rotation, transports and compresses the gaseous refrigerant without operating fluid in the working chamber from the inlet (10) to the outlet collection chamber (13), wherein the spindle rotors (2) and (3), as well as the surrounding compressor housing (8), are selectively cooled by means of their own refrigerant evaporators (6) and (7) and (9) via respective regulating elements (16), (17), (18.1 or 18.2), (21), (22) and (23) with respect to pressure level and flow rate via a partial flow branch (25) of liquid refrigerant, such that the clearances between the spindle rotors (2 and 3) and to the compressor housing (8) remain unchanged within desired limits for all operating conditions.wherein the level of the network operating pressures is realized via the number of stages implemented as a series connection of working chambers between the 2-toothed rotor (2) and the 3-toothed rotor (3) in the compressor working chamber between inlet (10) and outlet (13), and the required highly flexible adjustment of the compressor output is achieved by the fact that, in addition to the inlet supply (11) to the inlet (10) in the rotor longitudinal axis direction, there are also post-inlet supplies (12) into the working chamber as well as, in addition to the outlet discharge (14) from the outlet collection chamber (13), there are also pre-outlet discharges (15), wherein both the inlet supplies (11 and 12) and the outlet discharges (14 and 15) are each equipped with their own regulating device,so that the refrigerant actually conveyed, both in terms of volume flow and pressure rise, can be specifically adjusted for the respective operating state for the purpose of performance adjustment by any combination including sequential partial flow rates of the individual inlet feeds (11 and 12) and outlet discharges (14 and 15), wherein, optionally, the injection (40) of liquid refrigerant with its own regulating element (41) for performance adjustment is also proposed, as is the possibility of operating the drive motor of the spindle compressor with a frequency converter (38) for speed variation for the purpose of targeted performance adjustment; furthermore, for applications in which the properties of the refrigerant (39) and / or the heat transfer quantities (32) or (33) for the respective rotor internal cooling are insufficient to cause the refrigerant to evaporate, the invention proposesthat the respective rotor internal cooling (6) or (7) is then designed as a heat exchanger according to DE 10 2013 009 040 A1 for the liquid refrigerant, wherein this liquid refrigerant is then discharged from each spindle rotor, for example, via a pitot tube pump according to DE 10 2013 009 040 A1, and is then, according to the invention, novelly directed to the evaporator cooling (9) for the compressor housing, wherein, depending on the application, hybrid forms of heat exchanger and evaporator are also possible for the rotor coolings (6) and (7); Furthermore, according to the invention, it is also proposed that the inner rotor bore surface for internal rotor cooling be designed in such a way that parking pockets (34) and overflow ramps (35) are provided for improved heat transfer, which are designed to be of different sizes in the longitudinal direction of the rotor according to the respective heat transfer conditions, and that the surfaces of the inner rotor bores wetted by the refrigerant are roughened in the sense of being “non-smooth”, corrugated and grooved.Also available in a threaded version.

[0009] Compared to the prior art in compressors for compression refrigeration machines, the aforementioned features of the invention represent a significant advance through the following advantages: 1) This improves the compressor efficiency through efficient heat dissipation during multi-stage compression. 2) Efficient heat dissipation during compression is achieved by using the refrigerant that is already present, so that no separate cooling equipment is required for the compressor machine. 3) Furthermore, the spindle compressor operates without its own operating fluid in the working chamber, which is a significant improvement compared to the state of the art, because comparable screw compressors require oil as an operating fluid in the working chamber. 4) At the same time, the spindle compressor, due to its multi-stage design, achieves the desired compression values ​​in just one machine, so that, compared to the state of the art, two compressor machines are no longer required at higher pressure values. 5) At the same time, the reliability and service life of the compressor is improved because, due to the lower radial and axial forces in the spindle compressor, the bearing load is lower, with direct positive effects on the bearing in terms of reliability and service life, and thus on the compressor and consequently on the entire compression refrigeration machine. 6) For the desired performance adjustment, the previously complex and critical control slides can be dispensed with, by using the post-inlet and pre-outlet, practically any volume flow and any pressure stage can be implemented with the spindle compressor according to the invention in accordance with the design. 7) Due to its proposed design, the spindle compressor can be directly implemented as a hermetically sealed machine and is always on the safe side thermodynamically. 8) Due to the high number of stages, the pressure pulsations at the outlet are much lower than with today's screw compressors, so the spindle compressor is significantly quieter.

[0010] The present invention is further explained in the following illustrations: Fig. Figure 1 shows, as an example of the present invention, a schematic diagram of the refrigerant circuit of a compression refrigeration machine with a spindle compressor as the working machine. The flow direction of the refrigerant, including the different states of compression, is shown. The branching of liquid refrigerant according to the invention for efficient cooling of the compressor components, namely the spindle rotor pair and the compressor housing, is also clearly visible. Furthermore, various post-inlet inlets (12) and pre-outlet outlets (15) are shown for the desired capacity adjustment. These can be combined in any way with the inlet inlet (11) and the outlet outlet (14) via the respective regulating elements to enable virtually any desired volume flow rate and pressure value in accordance with the design specifications. The spindle compressor machine (1) is shown only schematically; its structural design is shown in the following illustration. Fig. 2 is shown as an example. Fig. Figure 2 shows, by way of example, a cross-sectional view through the spindle compressor machine as a core element in the circuit of the compression refrigeration machine, as described in the Fig. The preceding explanations are already so self-explanatory that a repetition here is certainly unnecessary. Fig.Figure 3 shows, as an example of the present invention, an enlarged view of a detailed embodiment for rotor internal cooling via the refrigerant with regard to a possible design of the aforementioned parking pockets (34) and the overflow ramps (35), which are to be designed such that, on the one hand, the heat transfer to the refrigerant is optimized and, on the other hand, an efficient distribution of the refrigerant in the longitudinal direction of the rotor within the cooling bore surface is also achieved. Furthermore, the heat transfer to the refrigerant is significantly influenced by the design of this cooling bore surface, which is shown here by way of example as a jagged line to indicate that the surfaces of the rotor internal bores wetted by the refrigerant are roughened in the sense of being "not smooth", ribbed, and grooved, for example, also in the form of an internal thread. Reference numeral list: 1 multi-stage spindle compressor machine with preferably non-parallel spindle rotor rotary axes 2 2-tooth spindle rotor 3 3-tooth spindle rotor 4 Carrier shaft for the 2-tooth spindle rotor (2) with spindle rotor bearing on both sides, working chamber shaft seal, cooling fluid supply and synchronization gear 5 Carrier shaft for the 3-tooth spindle rotor (3) with spindle rotor bearing on both sides, working chamber shaft seal, cooling fluid supply and synchronization gear 6 Internal rotor cooling for the 2-tooth spindle rotor (2), preferably as a refrigerant evaporator, if under the spindle rotor conditions (such as diameter and rotational speed) the properties of the selected refrigerant as well as the heat transfer quantities (32) are sufficient for evaporation of the refrigerant in the cooling bore of the 2-tooth spindle rotor (2), otherwise the internal rotor cooling (6) for the 2-tooth spindle rotor (2) is implemented as a heat exchanger according to DE 10 2013 009 040.7, or application-specifically also as a hybrid form of evaporator and heat exchanger simultaneously 7 Internal rotor cooling for the 3-tooth spindle rotor (3), preferably as a refrigerant evaporator, if under the spindle rotor conditions (such as diameter and rotational speed) the properties of the selected refrigerant as well as the heat transfer quantities (33) are sufficient for evaporation of the refrigerant in the cooling bore of the 3-tooth spindle rotor (3), otherwise the internal rotor cooling (7) for the 3-tooth spindle rotor (3) is implemented as a heat exchanger according to DE 10 2013 009 040.7, or application-specifically also as a hybrid form of evaporator and heat exchanger simultaneously 8 compressor housings with an enclosing sheet metal casing 9 Refrigerant evaporator cooling for the preferably finned surface of the compressor housing 10 Inlet collection chamber of the spindle compressor for the gaseous refrigerant 11 Inlet feed with regulating device for the gaseous refrigerant 12 downstream inlets with respective regulating devices for the gaseous refrigerant 13 Outlet collection chamber of the spindle compressor for the gaseous refrigerant 14 Outlet discharge with regulating device for the gaseous refrigerant 15 pre- and exhaust ports with respective regulating devices for the gaseous refrigerant 16 Liquid refrigerant supply for 2z rotor inner evaporator cooling with regulating device 17 Liquid refrigerant supply for 3z rotor inner evaporator cooling with regulating device 18 liquid refrigerant feeds for compressor housing evaporator cooling with 18.1 a central regulating unit for smaller refrigerant spindle compressors 18.2 each with its own individual regulating unit for large refrigerant spindle compressors 19 evaporator openings in the sheet metal casing surrounding the compressor housing for compressor housing-evaporator cooling (9) 20 externally hermetically sealed collection space for the evaporated housing refrigerant 21 Passage with regulating device for the forwarding of the casing refrigerant vapor 22 Passage with regulating body for the forwarding of the 2z rotor inner refrigerant vapor 23 Passage with regulating body for the forwarding of the 3z rotor inner refrigerant vapor 24 Main flow circuit for the refrigerant, showing the flow direction 25 diverted partial flow of liquid refrigerant for cooling the spindle compressor 26 Condenser for the refrigerant in the main flow circuit 27 evaporators for the refrigerant in the main flow circuit 28 Drive power for the spindle compressor 29 Heat transfer for case cooling (9) 30 Heat dissipation in the refrigerant condenser (26) 31 Heat absorption in the refrigerant evaporator (27) 32 Heat transfer for 2z rotor internal cooling (6) 33 Heat transfer for 3z rotor internal cooling (7) 34 parking spaces for the liquid refrigerant for internal rotor cooling 35 Overflow ramps between the parking bays (34) for internal rotor cooling 36 Expansion valve as a throttle for the liquid refrigerant in the main flow circuit 37 Branch for the liquid refrigerant for cooling the spindle compressor components 38 frequency converters for the drive motor 39 Refrigerant that constantly passes through 2 states of matter in the refrigerant cycle: • as liquid refrigerant (represented in hexa-hatching, as closed hexa-rings) • as gaseous refrigerant (represented in dotted hatching) 40 Injection of liquid refrigerant into the compressor working chamber 41 Regulator for refrigerant injection into the compressor working chamber

Claims

[1] Spindle compressor as a 2-shaft rotary positive displacement machine operating in a working space without operating fluid for conveying and compressing gaseous conveying media, primarily for compression refrigeration machines, with two spindle rotors (2, 3) in a surrounding compressor housing (8) with an inlet (10) and an outlet collection chamber (13), wherein a multi-stage spindle compressor (1) is used as the refrigerant compressor, the compressor housing (8) and the spindle rotors (2 and 3) of which are cooled via a partial flow branch (25) of liquid refrigerant (39) from the main refrigerant flow circuit (24), characterized by, that the compression heat is dissipated from the compressor housing (8) via refrigerant evaporation (9), whereby liquid refrigerant is directed via a partial flow branch (25) through a regulating element (18) to the housing refrigerant evaporation (9) and the refrigerant vapor exiting the housing refrigerant evaporation (9) through the openings (19) enters the collection chamber (20), and that this refrigerant vapor flows via passage (21) with regulating element into the inlet chamber (10) of the spindle compressor machine (1). [2] Spindle compressor according to claim 1, characterized by, that the heat of compression from the spindle rotors (2 and 3) is dissipated in their respective large cooling bores via refrigerant evaporation (6 and 7), if under the spindle rotor conditions (such as diameter and rotational speed) the properties of the selected refrigerant as well as the heat transfer quantities (32 and 33) are sufficient for evaporation of the respective supplied refrigerant, wherein liquid refrigerant is directed by means of a partial flow branch (25) to each spindle rotor cooling bore via a regulating element (16 and 17) and the refrigerant vapor exiting the respective spindle rotor refrigerant evaporation (6 and 7) via the respective openings (22 and 23) with regulating element is directed into the inlet chamber (10). [3] Spindle compressor according to claim 1, characterized by, that the compression heat from the spindle rotors (2 and 3) is dissipated in their large cooling bore via liquid refrigerant as a heat exchanger if, under the spindle rotor conditions (such as diameter and speed), the properties of the selected refrigerant as well as the heat transfer quantities (32 and 33) are insufficient for evaporation, wherein this liquid refrigerant is discharged from each spindle rotor, for example via a pitot tube pump, and directed to the evaporator cooling (9) for the compressor housing, where it then also enters the inlet chamber (10) of the spindle compressor machine (1). [4] Spindle compressor according to one of claims 1 and 3, characterized by , that, depending on the application, for rotor cooling (6) and (7), hybrid forms can also be combined and act together as heat exchangers and as evaporators. [5] Spindle compressor according to any of the preceding claims, characterized by, that the aforementioned cooling systems (6 and 7 as well as 9) for the spindle compressor components (2 and 3 as well as 8) are used via the respective regulating bodies (16), (17), (18.1 or 18.2), (21), (22) and (23) with regard to pressure level and flow rate in such a targeted manner that the clearance distances between the spindle rotors (2 and 3) as well as to the compressor housing (8) remain unchanged within desired limits for all operating conditions. [6] Spindle compressor according to one of the preceding claims, characterized by, that in addition to the inlet supply (11) to the inlet chamber (10) in the rotor longitudinal axis direction there are also post-inlet supplies (12) into the working chamber as well as, in addition to the outlet discharge (14) from the outlet collection chamber (13), there are also pre-outlet discharges (15), whereby both the inlet supplies (11 and 12) and the outlet discharges (14 and 15) are each equipped with their own regulating device, so that the refrigerant actually conveyed, both in terms of volume flow and in terms of pressure increase, can be specifically adjusted to the respective operating condition by any combination including sequential partial flow quantities of the individual inlet supplies (11 and 12) and outlet discharges (14 and 15). [7] Spindle compressor according to one of the preceding claims, characterized by, that for targeted performance adjustment to different operating conditions via a regulating body (41) the injection (40) of liquid refrigerant into the working space is provided and / or the possibility of operating the drive motor of the spindle compressor with a frequency converter (38) for speed variation for the purpose of targeted performance adjustment. [8] Spindle compressor according to any of the preceding claims, characterized by , that the inner spindle rotor bore surface for rotor internal cooling is designed such that parking pockets (34) and overflow ramps (35) are provided for improved heat transfer, which are designed to be of different sizes in the longitudinal direction of the rotor according to the respective heat transfer conditions in order to ensure both the appropriate residence time of the refrigerant for heat absorption and the comprehensive distribution of the refrigerant over the entire cooling bore surface. [9] Spindle compressor according to any of the preceding claims, characterized by , that the surfaces of the rotor inner bores wetted by the refrigerant are roughened in the sense of being “non-smooth”, corrugated and grooved, and are also designed with a thread shape to increase the heat transfer surface wetted by the refrigerant and to specifically manipulate the flow movement of the refrigerant.

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