COMPRESSOR

Abstract

A dry-compressing compressor comprises two screw rotors in a housing defining a suction chamber. At a compressor inlet of the compressor preferably atmospheric pressure prevails and at a compressor outlet of the compressor preferably a pressure of more than 2 bars (absolute) prevails. For each screw rotor at least one displacement element including a helical recess defining a plurality of windings is provided. The at least one displacement element per screw rotor has a single-pass asymmetrical profile.

Claims

1. A dry-compressing compressor comprising a housing defining a suction chamber and having a compressor inlet where preferably atmospheric pressure prevails and a compressor outlet where preferably a pressure of at least 2 bars (absolute), preferably at least 5 bars (absolute) prevails, two screw rotors arranged in the suction chamber and each having at least one displacement element including a helical recess for defining a plurality of windings, wherein at least one displacement element per screw rotor has a single-pass asymmetrical profile, the screw rotors have no internal cooling of the rotors, and the housing has a mean heat flow density of less than 80000 W/m.sup.2 in the area of the displacement elements.

2. The dry-compressing compressor according to claim 1, wherein the profiles are configured such that not blowhole is formed.

3. The dry-compressing compressor according to claim 1, wherein the profiles of the at least one displacement element of each screw rotor are configured a Quimby profile.

4. The dry-compressing compressor according to claim 1, wherein a displacement element arranged near the outlet of the vacuum pump has symmetrical profile.

5. The dry-compressing compressor according to claim 1, wherein at least one displacement element per screw rotor and/or in the case of a plurality of displacement elements per screw rotor said displacement elements jointly comprise a number (n) of windings which is larger than the ratio of outlet pressure (p.sub.out) to inlet pressure (p.sub.in) such that $n>\frac{\mathrm{Pout}}{\mathrm{Pin}}$ $\mathrm{preferably}$ $n>\frac{\mathrm{Pout}}{\mathrm{Pin}}+4.$ $\mathrm{applies}.$

6. The dry-compressing compressor according to claim 1, wherein the installed volume ratio between the delivery volume of the inlet stage (V.sub.in) and the outlet stage (V.sub.out) is adapted to the pressure ratio between inlet pressure (p.sub.in) and outlet pressure (p.sub.out) such that the following applies: $V_i=\frac{\mathrm{Vin}}{\mathrm{Vout}}={\left(\frac{\mathrm{Pout}}{\mathrm{Pin}}\right)}^{1.Math.\text{/}.Math.k}$ wherein n has a value of k0.3 to k+0.3 and k is the isotropic exponent of the gas mixture to be delivered.

7. The dry-compressing compressor according to claim 1, wherein the displacement elements include at least one area where the volume of the inlet stage (V.sub.in) decreases to a precompression volume (V.sub.VK) in a small rotation angle range, wherein the ratio between inlet volume (V.sub.in) and the volume of the precompression (V.sub.VK) is related to the internal volume ratio (v.sub.i) of the compressor $v_{\mathrm{VK}}=\frac{\mathrm{Vin}}{\mathrm{Vout}}={\left(v_i\right)}^{1.Math.\text{/}.Math.j}$ wherein j=2 to 5.

8. The dry-compressing compressor according to claim 7, wherein the compression from the inlet volume (V.sub.in) to the precompression volume (V.sub.VK) takes place during one and a half to three rotor revolutions (windings).

9. The dry-compressing compressor according to claim 1, wherein at least one displacement element per screw rotor and/or in the case of a plurality of displacement elements per screw rotor said displacement elements jointly have a ratio of length (L) to diameter (D) for which the following applies $\frac{L}{D}>\frac{\mathrm{Pout}}{2.Math.\mathrm{Pin}}-2$ $\mathrm{and}.Math..Math.\mathrm{in}.Math..Math.\mathrm{particular}$ $\frac{L}{D}>\frac{\mathrm{Pout}}{2.Math.\mathrm{Pin}}-1$

10. The dry-compressing compressor according to claim 1, wherein the pitch of the windings of the displacement elements varies, preferably changes and particularly preferably decreases from the compressor inlet to the compressor outlet.

11. The dry-compressing compressor according to claim 1, wherein the head and the foot diameter of the rotor preferably continuously changes, wherein the rotor is in particular of a conical configuration.

12. The dry-compressing compressor according to claim 1, wherein the pressure ratio $\frac{\mathrm{Pout}}{\mathrm{Pin}}$ between outlet and inlet pressure is at least 5.

13. The dry-compressing compressor according to claim 1, wherein two screw rotors with parallel axes are provided.

14. The dry-compressing compressor according to claim 1, wherein at the compressor inlet in particular inside the housing a gas collection chamber is provided.

15. The dry-compressing compressor according to claim 1, wherein at the compressor outlet a gas collection chamber is provided in particular inside the housing.

16. The dry-compressing compressor according to claim 1, wherein in the housing roller bearings and preferably seals are arranged on both sides of the two screw rotors.

17. The dry-compressing compressor according to claim 1, wherein for synchronizing the two screw rotors a synchronization gear is provided.

18. The dry-compressing compressor according to claim 1, wherein the speed of the screw rotors is higher than $3.Math.\text{,}.Math.000.Math..Math.\frac{1}{\min },$ $\frac{1}{\min },$ $\frac{1}{\min }.$

19. The dry-compressing compressor according to claim 1, wherein the one displacement element is configured as a discharge-side displacement element and for each screw rotor at least one further displacement element is provided.

20. The dry-compressing compressor according to claim 1, wherein between an upper surface of the displacement element and an inner surface of the suction chamber a gap with a height of 0.03 mm to 0.2 mm is formed.

21. The dry-compressing compressor according to claim 1, wherein the suction-side displacement elements have a constant pitch along their overall length.

22. The dry-compressing compressor according to claim 1, wherein each screw rotor comprises a rotor shaft supporting the at least one displacement element.

23. The dry-compressing compressor according to claim 1, wherein the displacement elements of a screw rotor are of an integral configuration.

24. The dry-compressing compressor according to claim 1, wherein the screw rotors and in particular the at least one displacement element per screw rotor have a smaller expansion coefficient that the housing, wherein the expansion coefficient of the housing is in particular at least larger than that of the screw rotors and/or the at least one displacement element.

25. The dry-compressing compressor according to claim 1, wherein the screw rotors do not comprise any ducts through which in particular a liquid coolant flows.

26. The dry-compressing compressor according to claim 1, wherein the screw rotors are of a solid configuration.

27. The dry-compressing compressor according to claim 1, wherein a temperature difference in the area of the discharge-side displacement elements between the latter and the housing during normal operation is smaller than 50 K.

28. The dry-compressing compressor according to claim 1, wherein the distance between the area where 5 A) to 20% of the outlet pressure prevails and the last winding of the discharge-side displacement element is at least 20% to 30% of the rotor length.

29. The dry-compressing compressor according to claim 1, wherein a gap between the edges of at least one of the displacement elements preferably has a gap height of 0.1 to 0.3 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Hereunder the disclosure will be explained in detail on the basis of a preferred embodiment with reference to the accompanying drawings in which:

[0062] FIG. 1 shows a schematic top view of a preferred embodiment of a screw rotor of the screw compressor according to the disclosure,

[0063] FIG. 2 shows a schematic sectional view of displacement elements having an asymmetrical profile,

[0064] FIG. 3 shows a schematic sectional view of displacement elements having a symmetrical profile, and

[0065] FIG. 4 shows a schematic sectional view of a screw compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0066] The screw rotors illustrated in FIGS. 1 to 3 can be used in a screw compressor according to the disclosure as shown in FIG. 4.

[0067] According to a preferred embodiment of the screw compressor, the rotor has a pitch changing and/or variable in the direction of compression, i.e. from left to right in FIG. 1. In a first suction-side area 10 defining a first displacement element a large pitch of approximately 50-150 mm/revolution is provided. Here, the pitch changes in the area 10, i.e. in the precompression area, to 55-65% of the inlet pitch, i.e. approximately 30-100 mm/revolution. In a second discharge-side area 12 corresponding to a second displacement element 12 the pitch is considerably smaller. In this area the pitch is in the range of 10-30 mm/revolution. In the illustrated embodiment, the at least one displacement element per screw rotor is thus defined by a screw rotor having a variable, preferably continuously changing pitch. This corresponds to a plurality of displacement elements arranged one behind the other as seen in the direction of delivery.

[0068] In the illustrated preferred embodiment, both in the inlet area and the outlet area a gas collection chamber 14 each is provided.

[0069] Further, the integral screw rotor comprises two bearing seats 16 and a shaft end 18. The shaft end 18 has connected thereto a gearwheel for driving purposes, for example.

[0070] Likewise, it is possible that the individual displacement elements 10, 12 are manufactured separately from each other and are separately affixed to the rotor shaft by pressing, for example. Here, the bearing seats 16 and the shaft ends 18 can be integral components of the shaft 20. Here, the continuous shaft 20 can be made from a material differing from that of the displacement elements 10, 12.

[0071] In addition, conical rotors can be provided. According to the disclosure, they comprise a plurality of displacement elements. Here, too, it is particularly preferred that the plurality of displacement elements are realized by a variable pitch. Conical rotors, too, are of a single-pass configuration.

[0072] FIG. 2 shows a schematic sectional view of an asymmetrical profile (e.g. a Qumiby profile). The illustrated asymmetrical profile is a so-called Quimby profile. The sectional view shows two screw rotors which mesh with each other and whose longitudinal direction is perpendicular to the drawing plane. The counter-rotation of the rotors is indicated by two arrows 15. Relating to a plane 17 extending perpendicularly to the longitudinal axis of the displacement elements, the profiles of the edges 19 and 21 are of different configuration for each rotor. The opposing edges 19, 21 must thus be manufactured separately from each other. However, this somewhat more complex and difficult manufacture offers the advantage that no continuous blowhole exists but a short-circuit occurs merely between two adjacent chambers.

[0073] Preferably, such an asymmetrical profile is provided for the suction-side displacement element 10.

[0074] The schematic sectional view in FIG. 3 shows a cross-section of two displacement elements and/or two screw rotors which are again counter-rotating (arrows 15). Relating to the symmetry axis 17, the edges 23 of each displacement element are of a symmetrical configuration. The preferred exemplary embodiment of a symmetrical contour illustrated in FIG. 4 is a cycloid profile.

[0075] A symmetrical profile, as illustrated in FIG. 3, is preferably provided for the discharge-side displacement elements 12.

[0076] Further, it is possible that more than two displacement elements are provided. They can possibly have different head diameters and corresponding foot diameters. Here, it is preferred that a displacement element having a larger head diameter is arranged at the inlet, i.e. on the suction side, for realizing a larger suction capacity in this area and/or increasing the installed volume ratio. Further, combinations of the embodiments described above are possible. For example, one or a plurality of displacement elements can be integrally formed with the shaft, or an additional displacement element can be separately manufactured and then mounted to the shaft.

[0077] In the schematic view of a preferred embodiment of a screw compressor according to the disclosure illustrated in FIG. 4, two screw rotors, as illustrated in FIG. 1, are arranged in a housing 26. The compressor housing 26 comprises an inlet 28 through which gas is taken in in the direction indicated by an arrow 30. Further, the compressor housing 26 comprises a discharge-side outlet 32 through which the gas is discharged in the direction indicated by an arrow 38. Preferably, the screw compressor according to the disclosure compresses air in a compressed air chamber.

[0078] Between upper surfaces 42 of the two displacement elements 12 and an inner surface 44 of a suction chamber 46 defined by the compressor housing 26, a gap is formed whose height preferably lies in the range of 0.03 mm-0.2 mm and in particular in the range from 0.05 mm-0.1 mm.

[0079] The gap between the edges of the displacement elements preferably has a gap height of 0.1-0.3 mm.

[0080] In the illustrated exemplary embodiment, the compressor housing 26 is closed by two housing covers 47. The left housing cover 47 in FIG. 4 comprises two bearing supports where a ball bearing 48 each for supporting the two rotor shafts is arranged. On the right side in FIG. 4, journals 50 of the two screw rotor shafts protrude through the covers 47. On the outside a respective gearwheel 52 is arranged on the two shaft journals 50. In the illustrated exemplary embodiment, the two gearwheels 52 mesh with each other for synchronizing the two screw rotors with each other. Further, in the right cover 47 in FIG. 4, two bearings 48 for supporting the screw rotors are arranged. In the housing walls 47 a seal not illustrated is provided in addition to the bearings 48.

[0081] The lower shaft in FIG. 4 is a drive shaft connected to a drive motor not illustrated.