EP1957799A1

EP1957799A1 - Helical screw compressor

Info

Publication number: EP1957799A1
Application number: EP06754262A
Authority: EP
Inventors: Carsten Achtelik; Dieter HÜTTERMANN; Michael Besseling; Norbert Henning
Original assignee: GHH Rand Schraubenkompressoren GmbH
Current assignee: GHH Rand Schraubenkompressoren GmbH
Priority date: 2005-12-08
Filing date: 2006-06-09
Publication date: 2008-08-20
Also published as: ES2359015T3; WO2007065485A1; WO2007065487A1; US20080286138A1; US7690901B2; WO2007065486A1; DE502006008894D1; ATE498071T1; US20080286129A1; EP1957798B1; HK1127111A1; EP1979618A1; US20130011285A1; EP1957798A1; EP1957797B1; CN101321955A; US7713039B2; WO2007065484A1; US20090004036A1; EP1957797A1

Abstract

The invention relates to a helical screw compressor comprising two rotors which are mounted in the rotor housing. Said helical screw compressor comprises sealing arrangements (11, 11') for sealing the pressure-sided shaft journals of the rotors. Each sealing arrangement comprises a plurality of annular seals (11a, 11b) which are arranged in a row adjacent to each other, and an annular-shaped discharge chamber (51) is associated with said system on an intermediate position and is connected, by means of a discharge channel (53), to the chamber in the rotor housing, wherein pressure which is higher than the atmospheric pressure. Preferably, the discharge channel is connected to the suction chamber (10) of the rotor housing (1), and is impinged upon by precompressed gas from an upstream compressor step.

Description

Screw compressor

The invention relates to a screw compressor with the features specified in the preamble of claim 1.

Screw compressors of this type are known for example from EP 0 993 553 Bl and EP 1 163 452 Bl. They have a vent duct open to the atmosphere connected to the relief chamber of the sealing arrangement.

The present invention is particularly advantageously applicable to a screw compressor that uses a gaseous medium, such as. B. air, to very high pressures, e.g. B. in the range of 30 to 50 bar, and which can be, in particular, the high pressure stage of a two-stage or multi-stage compressor unit. The invention also relates to such a multi-stage, in particular three-stage screw compressor unit.

Due to the high compression pressure of the compressor, the sealing arrangements which seal the pressure-side shaft journals of the rotors in the rotor housing are exposed to a very high pressure load. Even if the sealing arrangement consists of a larger number of ring seals arranged in a row, there is no uniform pressure drop across the entire sealing arrangement, but the pressure drop occurs mainly at the outer, i.e. H. ring seals further away from the rotor, with the result that they are exposed to increased mechanical stress.

The object of the invention is to design the sealing arrangement for the pressure-side shaft journals in a screw compressor of the type specified in such a way that the pressure drop across the sealing arrangement is controlled and equalized can be, so that the reliability of the seal can be improved especially at very high final pressures of the screw compressor.

The achievement of the object is specified in claim 1. The dependent claims relate to further advantageous features of the invention.

It was found according to the invention that by specifying a defined intermediate pressure at a defined intermediate position of the sealing arrangements of the pressure-side shaft journals of the rotors, the pressure curve in the sealing arrangement can be checked and evened out, with the result that a particularly effective and reliable seal and a minimization of pressure losses through Leakage gas leakage can be achieved.

An embodiment of the invention is explained in more detail with reference to the drawings. It shows

Figure 1 is a perspective, partially sectioned view of the screw compressor according to an embodiment of the invention;

FIG. 2 shows a cross section of the screw compressor from FIG. 1 approximately along the section line II-II from FIG. 1,

FIG. 3 shows a section substantially along the line III-III of FIG. 2.

4 shows a perspective view of a three-stage screw compressor unit, the third stage of which is a screw compressor according to FIG. 1.

The screw compressor shown in FIG. 1 has a rotor housing 1, shown in section, in which two rotors 3 and 5 are rotatably mounted in parallel axes. The axes of rotation of the rotors 3, 5 lie in a common vertical plane, which is also the sectional plane for the representation of the rotor housing 1. Every rotor has a pro- fil section 7 or 9, which has a profile with helically extending ribs or grooves, the ribs and grooves of the two profile sections 7, 9 meshing and sealingly without contact. Shaft journals 7a, 7b, 9a, 9b adjoin the profile sections 7, 9 on both sides, with their peripheral surface cooperating with sealing arrangements 11, 12 in order to seal the rotor in the rotor housing 1. The shaft journals 7a, 7b, 9a, 9b are also rotatably supported in the rotor housing 1 by bearings 13, 15.

The upper rotor 3 in FIG. 1 is the main rotor and has at its left end in FIG. 1 an extension 7c of its shaft journal which is intended to receive a drive gear (not shown) which meshes with a corresponding gear of a drive gear (not shown) to drive the rotor 3 to rotate. At the right end in FIG. 1, the two rotors 3, 5 have two meshing gears 17, 19 which form a synchronizing gear which rotates from the upper rotor 3 to the lower rotor 5, which is the secondary rotor, in the desired speed ratio transmits.

When the screw compressor shown in FIG. 1 is operating, its suction chamber 10, which is formed in the rotor housing 1 at the left end of the profile sections 7 and 9 in FIG. 1 and is connected to a suction nozzle (not shown), the gas to be compressed, in particular air , fed. The gas supplied is preferably already pre-compressed by one or more upstream compressor stages (not shown) to an intermediate pressure, for example to a pressure in the range from 10 to 15 bar, preferably 12 bar. This precompressed gas is conveyed to the right by the profile sections 7, 9 of the two rotors 3, 5 in FIG. 1 and is compressed to a final pressure which is preferably in the range from 30 to 50 bar, in particular around 40 bar. The compressed gas leaves the rotor housing 1 at the right end of the profile sections 7, 9 in FIG. 1 through an outlet (not shown).

The rotor housing 1 is surrounded by a cooling jacket or cooling housing 21, which is predominantly formed in one piece with the rotor housing 1 and this at a distance surrounds. The cooling housing 21 has large openings at the top and bottom, which are closed by means of a cover plate 23 and a base plate 25 which are fastened by screws. Between the rotor housing 1 and the cooling housing 21, 23, 25 there is a cooling space 27 which surrounds the rotor housing 1 in a ring ^.

Figure 2 shows schematically and simplified a cross section approximately along the line II - II of Figure 1. The rotor housing 1 for receiving the screw rotors (not shown) is surrounded by the cooling jacket or cooling housing 21, the side walls 21a, 21b of which are preferably in one piece with the rotor housing 1 are formed and which is closed at the top and bottom by the cover wall 23 or base plate 25. The cooling housing 21 forms with the rotor housing 1 a cooling space 27 which surrounds the rotor housing 1 essentially completely in a ring and which is interrupted only at one point by a partition wall 29 connecting the rotor housing 1 to the side wall 21b of the cooling housing 21. The partition 29 runs horizontally approximately halfway between the axis centers Ml, M2 of the screw rotors arranged vertically one above the other.

The cooling housing 21 has an inlet opening 31 and an outlet opening 33 for cooling liquid, for. B. cooling water or oil. The inlet opening 31 opens into an inlet channel 35 which runs vertically upwards, the upper outlet opening 35 'of which is at a distance from the underside of the partition wall 29. In front of the outlet opening 33 there is a vertical outflow channel 37, the lower inlet opening 37 'of which faces the upper side of the partition wall 29 at a short distance.

The black arrows in FIG. 2 indicate the flow path of the coolant supplied to the inlet opening 31. This is perpendicular through the inflow channel 35

directed upwards against the underside of the partition wall 29, deflected sharply thereon and then flows downwards and in FIG and is withdrawn through the outflow channel 37 and the outlet opening 33. In the wall 39 separating the outflow channel 37 from the cooling space 1, a vent opening 41 with a small cross-section is formed at a height which corresponds approximately to the upper limit of the outlet opening 33. Air can escape through this ventilation opening 41 when the cooling space 27 is filled with coolant, as indicated by the dotted arrows in FIG Liquid level, can be filled and the volume of the residual air trapped above the liquid level 43 is very small.

In the wall 45 separating the inflow channel 35 from the cooling space 27, a seepage opening 47 of very small cross-section is formed at the level of the lower limit of the inlet opening 31. When the cooling liquid is emptied from the cooling space 27, water can drain through the seepage opening 47 and the inlet opening 31 (as indicated by the lower dotted arrows in FIG. 2) until the liquid level in the cooling space 27 has reached the height of the seepage opening 47, i. H. has dropped to the level indicated by line 49. The residual amount of cooling liquid remaining below line 49 when the cooling chamber 27 is emptied is therefore very small.

FIG. 3 shows further details of the invention which relate to the sealing arrangements 11 shown in FIG. 1 for sealing the pressure-side shaft journals 7b, 9b of the rotors 3, 5 in the rotor housing 1. As shown, the sealing arrangement 11 consists of a number of ring seals I Ia, I Ib arranged in a row. In the embodiment shown, eight ring seals 11a, 11b are arranged one behind the other. The ring seals I Ia, 1 Ib can preferably be lip seals, as such. B. is known from EP 0 993 553. At a suitable point, which lies between a first number of ring seals 11a and a second number of ring seals 11b, the seal arrangement 11 is surrounded by a first annular relief chamber 51 for collecting leakage gas passing through the seals 11a. In the embodiment of FIG. 3 with eight ring seals, the relief space 51 can advantageously be seen between that from the rotor profile 7 first number of five sealing rings 11 a and the last three, ie outer ring seals 1 Ib.

The relief chamber 51 is connected to the suction chamber 10 of the screw compressor by a connecting channel 53 formed in the rotor housing 1 parallel to the rotor axis>. The annular relief chamber 51 is therefore subjected to the suction pressure of the screw compressor prevailing in the suction chamber 10. In the preferred use of the screw compressor as a high-pressure stage of a multi-stage compressor unit, the air supplied to the suction chamber 10 can already be brought up to a pressure of, for example, upstream by the compressor stages. B. between 10 and 15 bar, in particular about 12 bar, and this is then the pressure prevailing in the relief chamber 51. In operation of the compressor, the high final pressure generated by the rotors, e.g. B. 40 bar, drop to zero via the sealing arrangement I Ia, I Ib. It has been shown that this pressure drop is not linear, but mainly concentrates on the outer ring seals 11b, which are more distant from the profile section 7, 9, and is therefore subject to very high mechanical loads. The first relief chamber 51, which is charged with the inlet pressure of the compressor, predefines a defined intermediate pressure at a defined point in the seal arrangement, thereby equalizing the pressure drop across the entire seal arrangement I Ia, I Ib, whereby the seals 1 Ib are mechanically relieved.

At the end of the sealing arrangement 11 which is remote from the rotor, a second annular relief space 55 is provided, which is connected to the atmosphere in a manner known per se. The task of this second relief chamber 55 is to keep the oil system used to lubricate the bearing 15 and the synchronous gear 17, 19 free of pressure and to keep the leakage gas through the seal arrangement 11 to the oil-lubricated areas as small as possible.

As can be seen from FIG. 1, the sealing arrangement 11 'for the shaft journal 9b of the lower rotor 5 is designed in the same way as the sealing arrangement 11 of the shaft journal 7b and also has an annular relief chamber 51' which connects to the suction chamber 10 of the screw compressor through a ventilation duct ver is bound. The venting duct 53 shown in FIGS. 2 and 3 is preferably a common connecting duct which is connected to both relief chambers 51, 51 'of the sealing arrangements 11, 11' and connects them to the suction chamber 10.

As shown in FIG. 2, the ventilation duct 53 connecting the relief chamber 51 with the suction chamber 10 in the rotor housing 1 preferably runs in the immediate vicinity of the partition wall 29 connecting the rotor housing 1 with the cooling housing 21. Thanks to the intensive cooling of the partition wall 29, which acts like a cooling fin the coolant deflected at it, the connecting channel 53, and thus the leakage gas flowing in it to the suction space 10, is subjected to particularly intensive cooling.

FIG. 4 shows in perspective a three-stage screw compressor unit with three screw compressors 60, 70, 80, which are flange-mounted freely cantilevered parallel to one another on a gearbox housing 90, which essentially has the shape of a vertical disk. They are driven together by a drive gear mounted in the gear housing 90 and driven by a motor, as is known per se from DE 299 22 878.9 U1 and from DE-A-16 28 201 for two-stage compressor units. In the compressor unit shown, the screw compressor 60 is the input stage (low-pressure stage) with intake opening 61 and outlet opening 63, the screw compressor 70 is the second stage or intermediate stage with inlet opening 71 and outlet opening 73, and the screw compressor 80 is the final stage or high-pressure stage with inlet opening 81 and one In Figure 4 not visible outlet opening on the side facing away from the inlet opening 81. FIG. 4 also shows an oil sump housing 95 flanged to the foot of the gear housing 90, which is connected by oil lines to the synchronous gears of the screw compressors 60, 70, 80 and to the drive gear arranged in the gear housing 90.

Not shown in FIG. 4 are the connecting lines for the gas to be compressed, in particular air, connecting the inlets and outlets 61, 63, 71, 73, 81 of the three screw compressors 60, 70, 80. These can be carried out in the usual way. forms and z. B. be equipped with filters, intercoolers and / or silencers.

The screw compressor 80 of the third stage is a screw compressor designed according to FIGS. 1 to 3 according to the invention. The three-stage compressor unit according to FIG. 4 is preferably designed such that the outlet pressure of the first stage 60 is approximately 3 to 6 bar, in particular approximately 3.5 bar, the second stage (intermediate stage) 70 an outlet pressure of approximately 10 to 15 bar, in particular approximately 12 bar, and the third stage (high pressure stage) generates an outlet pressure in the range from 30 to 50 bar, in particular approximately 40 bar. The outlet pressure of approx. 12 bar generated by the second stage 70 is thus the pressure that prevails in the suction chamber 10 of the third stage 80 and thus also the relief chambers 51, 51 'of the sealing arrangements 11, 11' for the pressure-side shaft journals according to FIG 1 and 3 are acted upon.

Claims

Expectations

1. Screw compressor with two rotors (3, 5) mounted axially parallel in a rotor housing (1), which mesh with one another with helical ribs and grooves and, in operation, a gaseous medium, in particular air, from a suction end towards a pressure end of the rotors Promote and compress, the rotors at their suction and pressure ends each have shaft journals (7a, 7b, 9a, 9b), which are mounted in the rotor housing (1) by means of bearings (13, 15) and sealed by means of a sealing arrangement, whereby the sealing arrangement (11, 11 ') of each pressure-side shaft journal has an annular relief space (51) to which a ventilation channel (53) is connected,

characterized in that the ventilation duct (53) connects the relief space (51) to a space (10) formed in the screw compressor, in which a pressure prevails when the screw compressor is in operation, which pressure is higher than atmospheric pressure but lower than the outlet pressure of the screw compressor.

2. Screw compressor according to claim 1, characterized in that the ventilation duct (53) connects the relief chamber (51) with the suction chamber (10) of the rotor housing (1) and that the suction chamber (10) is connected to an upstream compressor stage, which is the suction chamber (10) supplies a pre-compressed gas at a pressure higher than atmospheric pressure.

3. Screw compressor according to claim 2, characterized in that its suction chamber (10) is acted upon by the upstream compressor stage with a pressure in the range from 10 to 15 bar, in particular approximately 12 bar, and the outlet pressure of the screw compressor in the range from 30 to 50 bar, especially around 40 bar.

4. Screw compressor according to one of claims 1 to 3, characterized in that the screw compressor is the third stage (80) of a three-stage compressor unit, the first and second stages (60, 70) are also screw compressors.

5. Screw compressor according to one of claims 1 to 4, characterized in that the sealing arrangement (11, 11 ') of each pressure-side shaft journal has a plurality of sealing rings (I Ia, I Ib) arranged one behind the other, and that the relief space (51) on one Such location of the sealing arrangement is provided that the number of sealing rings (I Ia) between the relief chamber (51) and the rotor profile (7, 9) is greater than the number of sealing rings (1 Ib) between the relief chamber (51) and the end of the Shaft journal (7a, 9a).

6. Screw compressor according to claim 5, characterized in that the number of sealing rings (I Ia, 1 Ib) is eight and the relief space is provided between the fifth and sixth sealing ring seen from the rotor.

7. Screw compressor according to one of claims 1 to 6, characterized in that the ventilation channel (53) is formed in a coolant-cooled wall of the rotor housing (1).