Power adjustment on a spindle compressor

Abstract

Spindle compressor as a 2-shaft rotary positive displacement machine operating in the working space without operating fluid for conveying and compressing gaseous conveying media for vacuum and overpressure applications, with a 2-toothed spindle rotor (2), with a 3-toothed spindle rotor (3) and with a compressor housing (1) surrounding the spindle rotors (2, 3), which has an inlet chamber (6) and an outlet collection chamber (3), characterized in that a first division regulating element ε R (21) is provided, into which a cooling fluid line opens and from which a cooling fluid line for a cooling fluid flow (22) for internal rotor cooling (6) of the 2-toothed spindle rotor (2) and a cooling fluid line for a cooling fluid flow (23) for internal rotor cooling (7) of the 3-toothed spindle rotor (3) extend, wherein the first distribution regulating device ε R(21) adjusts the cooling fluid flow (22) for internal rotor cooling (6) of the 2-tooth spindle rotor (2) and the cooling fluid flow (23) for internal rotor cooling (7) of the 3-tooth spindle rotor (3) to each other.

Description

[0001] Dry-compressing compressors are becoming increasingly important in industrial compressor technology. Due to increasing environmental regulations, rising operating and disposal costs, and increased demands for fluid purity, traditional wet-running compressors such as liquid ring compressors, rotary vane pumps, and oil- or water-injected screw compressors are increasingly being replaced by dry-compressing machines. These machines include dry screw compressors, claw pumps, diaphragm pumps, piston pumps, scroll machines, and Roots pumps. However, these machines have in common that they still do not meet today's requirements in terms of reliability and robustness, as well as size and weight, while maintaining a low price and satisfactory efficiency.

[0002] To improve this situation, the well-known dry-compressing spindle compressors are ideal. As typical twin-shaft positive displacement machines, they achieve high compression capacity simply by achieving the necessary multi-stage capability in a so-called "discharge screw" by connecting several closed working chambers in series, which can be adjusted by the number of turns per displacement rotor, without requiring an operating fluid in the working chamber. Furthermore, the contactless rolling action of the two counter-rotating spindle rotors enables an increased rotor speed, thus simultaneously increasing the nominal suction capacity and volumetric efficiency relative to the size.Dry-compressing spindle machines can be used for both vacuum and overpressure applications, although the power requirement is naturally significantly higher in overpressure because significantly larger pressure differences have to be overcome in the overpressure range with final pressures well over 2 bar (absolute) up to 15 bar and even higher.

[0003] For example, US 2006 / 0 269 424 A1 discloses a method for controlling the temperature of a rotor of a vacuum pump, in which a dry pump with a 2-shaft rotary displacement machine is used.

[0004] DE 10 2011 003 177 A1 discloses another two-shaft rotary displacement machine that can be supplied with a coolant via a heat exchanger and a distributor. The distributor distributes the coolant to the spindle rotors of the two-shaft rotary displacement machine.

[0005] DE 101 56 179 A1 further discloses a screw vacuum pump with internal rotor cooling, wherein a coolant is passed from a heat exchanger via a common valve into two rotors of the screw vacuum pump.

[0006] DE 10 2013 210 817 A1 describes another exemplary 2-shaft rotary displacement machine.

[0007] Furthermore, US 3 180 559 A discloses a mechanical vacuum pump.

[0008] Finally, DE 10 2013 009 040 A1 describes how a dry-compressing spindle compressor can achieve 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 means of non-parallel rotation axes of the two spindle rotors. However, the optimal design and advantageous construction for the purpose of flawless adaptation to different operating and working conditions, taking into account the specific thermodynamic situation of the spindle compressor in question, have still not been satisfactorily resolved. The special features of this multi-stage compressor technology must be specifically incorporated in order to significantly improve efficiency and reliability compared to the state of the art.

[0009] The object of the present invention is to improve both the clearance situation between the rotor pair and the surrounding compressor housing and the corresponding performance adaptation to different working conditions and application requirements for a spindle compressor as a dry-compressing 2-shaft rotary displacement machine with a 2-tooth spindle rotor and a counter-rotating 3-tooth spindle rotor with mutually inclined rotational axes of both spindle rotors for all operating conditions and operating condition changes.

[0010] According to the invention, this object is achieved by the features of claim 1. According to the embodiment in Fig. 1 is (a) an allocation regulator ε R(21) adjusts or divides the cooling fluid flow (22) for the internal rotor cooling (6) of the 2-tooth spindle rotor (2) and the cooling fluid flow (23) for the internal rotor cooling (7) of the 3-tooth spindle rotor (3) in such a way that for all operating conditions and changes in operating conditions, the clearance situation between the two spindle rotors (2 and 3) is maintained within selected limits, namely preferably a gap between the two spindle rotors (2 and 3) deviates by less than plus or minus 30% from the gap value during assembly, preferably only plus or minus 30% and in particular plus or minus 20%, and also b) an allocation regulator ε P (12) and a distribution regulator ε K(20) with interdependent and mutually monitored adjustment for the coolant quantity to the casing cooling fluid supply (15) and for the coolant quantities to the spindle rotor supplies (22 and 23) ensure that for all operating conditions and operating condition changes the clearance situation between the spindle rotor pair and the surrounding compressor casing is maintained within selected limits, This applies in particular to those spindle compressor designs in which the spindle rotor delivery thread part, which is fixed to rotation on a steel support shaft, is made of a material with higher thermal conductivity, preferably an aluminium alloy, and the surrounding compressor housing is made of a pressure-resistant cast material, for example at least GG 25 to GG 35, with lower thermal expansion coefficients, and only with this regulation of the coolant quantities for these components can the clearance situation be reliably controlled for all operating conditions and operating condition changes, whereby the specifications for the coolant quantity regulation originate from a simulation program that has been repeatedly verified by practical measurements and is continuously developed, in which the heat balances for each compressor component are created for all operating conditions and operating condition changes, in order to then implement the required coolant quantities and the resulting heat dissipation quantities to maintain the clearance situation within selected limits via their thermal expansion, and also c) the desired oil-free state in the compressor working chamber between inlet (1) and outlet (4) is also ensured on the compressor outlet side by a permanent loss gas flow (32) in that the pressure in the synchro-gear chamber (8) is always slightly (from about 20 mbar) lower than the pressure in the outlet collecting chamber (4), by directing this loss gas flow into the collecting chamber (18) in a controlled manner via a regulating element (17), and also d) for the desired freedom from oil in the compressor working chamber between inlet (1) and outlet (4), a permanent loss gas flow (25) via each inlet-side working chamber shaft seal ensures on the compressor inlet side in that the pressure in the collection chamber (26) for these inlet seals-feed loss gas flows (25) is always slightly (from about 20 mbar) lower than the pressure in the inlet collection chamber (1), whereby the intake negative pressure of the cooling fluid feed pump (10) is used via the intake pipe and feed (19) to reduce the pressure in the collection chamber (26), and also e) for each working chamber shaft seal there is at least one neutral gap (33) to check the absence of oil in the working chamber of the screw compressor between the inlet (1) and the outlet chamber (4) and also f) the application-specific desired power adjustment of the spindle compressor is carried out on the inlet side according to the invention via post-inlet feeds (28) with respective regulating element in connection with the regulating element for the inlet conveying gas flow (27), in that the conveying gas is specifically supplied to working chamber volumes of the multi-stage spindle rotor pair with different sizes in the rotor longitudinal axis direction for the desired volume flow setting with simultaneously different compression path lengths for the desired pressure increase setting, and also g) the application-specific desired power adjustment of the spindle compressor is carried out on the outlet side according to the invention via pre-outlet discharges (29) with respective regulating element in connection with the regulating element for the outlet conveying gas flow (30), in that the conveying gas is selectively discharged from different working chambers of the multi-stage spindle rotor pair in the rotor longitudinal axis direction after different compression path lengths for the application-specific desired setting of the compression height, whereby the performance adjustment measures referred to in f) and g) are combined, and also h) to improve the compressor efficiency, the parameter design for the spindle rotor pair is carried out using the simulation software mentioned in such a way that at least 30%, better still more than 40% and for larger drive powers even more than 50% of the compressor drive power is dissipated as heat via the working chamber components (2 and 3) and (5), and also i) as a result of the above-mentioned thermodynamic simulation of the compression process, the direction of flow of the cooling fluid during cooling of the compressor housing (5) is determined by connecting the cooling fluid supply (15) either to the cooling fluid transition point G2 (14) or to the cooling fluid transition point G1 (13).

[0011] The following illustration illustrates the present invention by way of example: Fig. Figure 1 shows, as an example of the present invention, a sectional view of the spindle compressor with the cooling fluid flows, including the simplified oil cooler (16), and the aforementioned control elements. This allows for optimal operation of the spindle compressor in accordance with the thermodynamic simulation, for all operating conditions and changes in operating conditions, in accordance with the application-specific requirements. The downstream inlet feeds (28) and the upstream outlet discharges (29) for the conveying medium provide the desired performance adjustment with regard to volume flow and working pressure.

[0012] Fig. 1 shows a longitudinal section through a non-parallel spindle rotor pair. This is a simplified representation; the spindle axes do not have to lie in the same plane as shown.

[0013] A spindle compressor without operating fluid in the working chamber, comprising a 2-tooth spindle rotor (2) and a 3-tooth spindle rotor (3) in a surrounding compressor housing (8) with preferably non-parallel axes of rotation of both spindle rotors. In order to improve the overall clearance situation and the power adjustment for all operating conditions and operating condition changes, the invention proposes that a distribution control element ε R (21) adjusts the cooling fluid flows (22 and 23) to both rotor internal cooling systems (6 and 7) in such a way that the clearance between the two spindle rotors (2 and 3) is maintained within selected limits. This also applies to the compressor housing via a distribution control device ε P (12) and a distribution regulator ε K(20) are interdependent and mutually monitored, as are the coolant quantities for the housing cooling fluid supply (15) and the spindle rotor supply (22 and 23). In addition, there are additional downstream inlet supply (12) into the working chamber, as well as additional upstream outlet discharges (15), each with its own control device for targeted performance adjustment. List of reference symbols 1 inlet collecting chamber for the pumped medium 2 2-tooth spindle rotor with carrier shaft, rotor bearings on both sides as well as working chamber shaft seal and synchronization gear and also optionally including drive gear 3 3-tooth spindle rotor with carrier shaft, rotor bearings on both sides, working chamber shaft seal and synchronization gear 4 Outlet collection chamber for the pumped medium 5 Compressor housing with enveloping sheet metal jacket according to DE 10 2012 011 823.6 6 Rotor internal fluid cooling for the 2-tooth spindle rotor 7 Rotor internal fluid cooling for the 3-tooth spindle rotor 8 Gearbox of the synchronization gears 9 Lubricating oil accumulation in the gear chamber of the synchro-gearing with oil level monitoring 10 Cooling fluid feed pump, preferably driven directly by the drive shaft 11 Lubricating oil supply from the cooling fluid feed pump with regulating element ε G 12 Allocation Regulatory Body ε P in the cooling fluid flow, preferably behind the cooling fluid pump (10) 13 Cooling fluid transition point G1 of the compressor housing 14 Cooling fluid transition point G2 of the compressor housing 15 Cooling fluid supply behind ε P (12) for compressor housing cooling 16 heat exchangers for the cooling fluid to dissipate the heat absorbed by the cooling fluid, especially from the compressor components such as the rotor pair and compressor housing, keyword: “oil cooler” 17 Regulator for the pressure in the synchronization gears gear chamber (8) with splash-proof discharge into the collecting chamber (18) 18 Cooling fluid collection chamber 19 Cooling fluid reservoir with intake pipe and supply to the cooling fluid feed pump (10) 20 Allocation Regulatory Body ε K in the cooling fluid flow, preferably behind the oil cooler (16) 21 Allocation Regulatory Body ε R in the cooling fluid flow to both spindle rotors 22 Cooling fluid supply for the rotor internal fluid cooling (6) for the 2-tooth spindle rotor (2) 23 Cooling fluid supply for the rotor internal fluid cooling (7) for the 3-tooth spindle rotor (3) 24 Cooling fluid discharge, for example into the cooling fluid reservoir (19) 25 Loss of gas flow through each inlet-side working chamber shaft seal 26 Collection chamber for all inlet seals and waste gas flows (25) 27 Inlet conveying gas flow with regulator into the compressor inlet plenum (1) 28 post-inlet feeds with regulating device for the pumped medium 29 pre-discharge outlets with regulating device for the pumped medium 30 Outlet conveying gas flow with regulator from the compressor outlet plenum (4) 31 Collective outlet line for the outlet conveying gas flow 32 Loss of gas flow through each outlet-side working chamber shaft seal 33 neutral intermediate control room of each working space shaft seal

Claims

[1] Spindle compressor as a 2-shaft rotary displacement machine operating in the working chamber without operating fluid for conveying and compressing gaseous conveying media for applications in vacuum and for applications in overpressure with a 2-tooth spindle rotor (2), with a 3-tooth spindle rotor (3) and with a compressor housing (1) surrounding the spindle rotors (2, 3), which has an inlet chamber (6) and an outlet collecting chamber (3), characterized by that a first allocation regulator ε R (21) is provided, into which a cooling fluid line opens and from which a cooling fluid line for a cooling fluid flow (22) for the internal cooling of the rotor (6) of the 2-tooth spindle rotor (2) and a cooling fluid line for a cooling fluid flow (23) for the internal cooling of the rotor (7) of the 3-tooth spindle rotor (3) originate, wherein the first distribution regulating element ε R(21) adjusts the cooling fluid flow (22) for the internal rotor cooling (6) of the 2-tooth spindle rotor (2) and the cooling fluid flow (23) for the internal rotor cooling (7) of the 3-tooth spindle rotor (3) to each other. [2] Screw compressor according to claim 1, characterized by that a second allocation regulator ε P (12) is provided, from which a cooling fluid line for coolant to the housing cooling fluid supply (15) and a cooling fluid line to a heat exchanger (16) branch off. [3] Spindle compressor according to one of the preceding claims, characterized by that a third allocation regulator ε K (20) is provided, from which a cooling fluid discharge (24) and the first distribution regulating member ε R (21) opening cooling fluid line. [4] Spindle compressor according to one of the preceding claims, characterized bythat the conveyor thread part of each spindle rotor (2 or 3), which is non-rotatable on a steel support shaft, is made of a material with higher thermal conductivity, namely at least 100 W / m K, preferably an aluminum alloy, and the surrounding compressor housing (5) is made of a pressure-resistant cast material, for example at least GG 25 to GG 35. [5] Spindle compressor according to one of the preceding claims, characterized by that the desired freedom from oil in the compressor working chamber between inlet (1) and outlet (4) on the compressor outlet side is created by a permanent loss gas flow (32), in that the pressure in the synchro-gear chamber (8) is always slightly (from about 20 mbar) lower than the pressure in the outlet collecting chamber (4), this loss gas flow being guided into the cooling fluid collecting chamber (18) in a controlled manner via a regulating element (17). [6] Spindle compressor according to one of the preceding claims, characterized bythat the desired freedom from oil in the compressor working chamber between inlet (1) and outlet (4) on the compressor inlet side is created by a permanent loss gas flow (25) via each inlet-side working chamber shaft seal, in that the pressure in the collecting chamber (26) for these inlet seal delivery loss gas flows (25) is always slightly (from about 20 mbar) lower than the pressure in the inlet collection chamber (1), wherein the suction negative pressure of the cooling fluid delivery pump (10) is used via the suction pipe and feed (19) to reduce the pressure in the collecting chamber (26). [7] Spindle compressor according to one of the preceding claims, characterized by that there is at least one neutral gap (33) for each working chamber shaft seal to check the absence of oil in the working chamber of the spindle compressor between the inlet (1) and the outlet chamber (4). [8] Spindle compressor according to one of the preceding claims, characterized bythat on the inlet side, the application-specific desired power adjustment of the spindle compressor is carried out via post-inlet feeds (28) with respective regulating element in conjunction with the regulating element for the inlet conveying gas flow (27), in that the conveying gas is specifically fed to working chamber volumes of the multi-stage spindle rotor pair that are of different sizes in the rotor longitudinal axis direction for the desired volume flow setting with simultaneously different compression path lengths for the desired pressure increase setting. [9] Spindle compressor according to one of the preceding claims, characterized in that the axes of rotation of the two spindle rotors (2 and 3) do not run parallel to each other. [10] Spindle compressor according to one of the preceding claims, characterized bythat on the outlet side, the application-specific desired power adjustment of the spindle compressor is carried out via pre-outlet discharges (29) with respective regulating element in conjunction with the regulating element for the outlet conveying gas flow (30), in that the conveying gas is specifically discharged from different working chambers of the multi-stage spindle rotor pair in the rotor longitudinal axis direction after different compression path lengths for the application-specific desired setting of the level of the compression pressure. [11] Spindle compressor according to one of the preceding claims, characterized by that in order to improve the compressor efficiency, the parameter design for the spindle rotor pair (2 and 3) is such that at least 30%, better still over 40% and for larger compressor drive powers even over 50% of the compressor drive power is dissipated as heat via the working chamber components (2 and 3) and (5). [12] Spindle compressor according to one of the preceding claims, characterized by that, as a result of a thermodynamic simulation of the compression process, the cooling fluid flow direction for cooling the compressor housing (5) is determined by connecting the cooling fluid supply (15) either to the cooling fluid transition point G2 (14) or to the cooling fluid transition point G1 (13). [13] Spindle compressor according to one of the preceding claims, characterized by that the axes of rotation of the two spindle rotors (2 and 3) are not parallel to each other. [14] Screw compressor according to claim 1, characterized by that during operation a gap between both spindle rotors (2 and 3) deviates by less than plus or minus 30% from the gap value during assembly, preferably less than plus or minus 30% and in particular less than plus or minus 20%.

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