EP1741931B1 - Lobe type compressor - Google Patents

Abstract

The compressor has two rotors each with two blades or teeth, a housing (2) round the rotors, forming feed chambers with the blades, a bearing device for the rotors separated from the chambers by a sealing device, a transmission device to hold the rotors in operation, and an oil cavity containing at least part of the transmission device.

Description

• zwei Rotoren mit jeweils mindestens zwei Flügeln oder Zähnen,
• einem die Rotoren umgebenden Gehäuse, welches mit seinen Innenflächen und den Außenflächen der Flügel oder Zähne Förderkammern für das Fördermedium bildet,
• einer im Gehäuse angeordneten Lageranordnung für die Rotoren, die gegenüber den Förderkammern über eine Dichtanordnung abgetrennt ist,
• einer Getriebeanordnung zum Berührungsloshalten der Rotoren im Betrieb,
• sowie einem Ölraum zur Aufnahme zumindest eines Teils der Getriebeanordnung und einer zu deren Schmierung und der Schmierung der Lager vorgesehenen Ölmenge.

The present invention relates to a rotary compressor for conveying media containing condensing vapors or vapor-gas mixtures, with

• two rotors each having at least two wings or teeth,
• a housing surrounding the rotors, which forms conveying chambers for the conveying medium with its inner surfaces and the outer surfaces of the vanes or teeth,
• a bearing arrangement in the housing for the rotors, which is separated from the delivery chambers via a sealing arrangement,
• a gear arrangement for keeping the rotors in contact during operation,
• and an oil space for accommodating at least a portion of the gear assembly and an amount of oil provided for lubrication and lubrication of the bearings.

For conveying media containing condensing vapors or vapor-gas mixtures, are designed according to the Roots principle or as a screw compressor with so-called "internal compression" working rotary compressor used. Such compressors have long been known and, for example, in EP 1519 045 A2 or DE 34 14 064 C2 or DE 34 14 039 C2 disclosed.

The rotors are predominantly equipped with two or three wings or teeth. In special cases, especially in so-called screw compressors, the rotors may also have more than three wings or teeth.

The housing used in such rotary compressors is formed predominantly in several parts. It usually consists of a cylinder part surrounding the rotors and this laterally terminating side plates and a housing cover or a wheel housing for the gear arrangement.

In many cases, so-called intermediate plates are provided in the area of the sides of the cylinder part, which can be equipped with so-called steam collecting spaces.

The rotors run with each other and against the cylinder part of the housing in normal operation without contact. This is ensured by the lateral arrangement of the gearbox, the gears of which, together with the bearing arrangement for the rotors, are preferably lubricated by means of a so-called "oil sump lubrication" for reasons of simplicity and cost savings. The oil supply of the gears and the bearing is usually effected by a mounted on a shaft so-called "Ölschleuderscheibe", which is arranged in the oil chamber and immersed in the oil sump.

A very important element of such known rotary compressor is the sealing arrangement which is arranged between the oil chamber and the actual delivery chamber. The sealing arrangement consists of special shaft seals or soft packings (so-called stuffing box packings), which have the task of keeping the pumped medium and in particular steam or condensate away from the oil space. Get that Liquid or vapor into the oil space, so the oil is mixed with liquid or condensed steam, so that the lubricity is at least impaired, but often even largely reduced so that the gears of the gear assembly or bearings of the bearing assembly are not sufficiently lubricated, which is capital Damage to the compressor can result.

To avoid problems in this direction, the sealing arrangement is structurally very complex. For example, one to five shaft seals are used per shaft passage. Between the shaft sealing rings, a grease filling with or without relubricating can be. The grease filling serves to lubricate the contact surfaces between shaft and sealing ring.

Frequently, so-called vapor collecting spaces are arranged between the delivery chamber and the oil chamber in the region of the sealing arrangements. These have the task to collect in the direction of the oil space flowing condensates or vapors and to divert through channels and openings provided before reaching the bearing assembly.

The complex design of the sealing arrangements has the disadvantage that they are very expensive and often subject to high wear under the given operating conditions. Thus, in addition to high temperatures, the sealing arrangements are constantly exposed to condensates and dirt particles from the conveying medium. In versions without relubricating and use of shaft seals also occurs after a short period of operation by consumption and washout a lack of fat and consequent increased wear in the field of sealing arrangements. In versions with relubrication on the other hand longer life of the sealing arrangements are only possible if for a regular maintenance is provided by the operating staff.

The use of so-called soft packs also provides no advantages in most operating conditions, since they have relatively short lifetimes. In addition, the wear of the seals is frequently not noticed until condensate has already entered the oil space and damage has already occurred to the bearing or gear arrangement.

A further problem is that the replacement of sealing arrangements requires disassembly of the entire compressor even with intact storage and gear arrangements. This leads to a plant downtime over longer periods and is also associated with high costs.

The arrangement of structurally complex sealing arrangements also requires a considerable additional effort on the housing and on the rotors and causes additional problems. Thus, the distance between the end face of the delivery chamber and the bearing assembly is inevitably increased by constructive complex sealing arrangements. This in turn leads to an increase in the length of the waves and thus the axial length of the compressor. As a result, a greater piston deflection and an increased tendency to vibrational excitation must be accepted. In some cases this leads to a reduction in the permissible shaft speed and the maximum pressure load of the rotors.

Further, the DE 103 30 856 A1 a vacuum pump in which the rotary pistons are lubricated by a lubricating oil supplied from a heatable oil collector.

Presentation of the invention

Object of the present invention is to provide a rotary compressor and a method for its operation, in which a completely new approach is taken to solve the above problems.

This object is achieved by a rotary compressor according to claim 1. Advantageous developments of the invention are specified in the appended claims.

The invention is based on the idea to keep the oil temperature in any operating condition always above the evaporation or condensation temperature of the fluid at a corresponding pressure in a rotary compressor of the type mentioned. For this purpose, the amount of oil and / or the housing walls forming the oil space can be heated according to the invention directly or indirectly.

As a result, the medium in this area always remains in the gas phase, whereby the formation of condensate or a transition into the liquid phase is avoided and mixing phenomena between condensate or medium in its liquid phase and oil can no longer occur. The necessary lubricant quality is thus always maintained.

Since the inventive measure condensate or liquid medium in its liquid phase in the sensitive area of the rotary compressor can no longer arise, the expensive and wear-prone shaft seals or soft packs by simple, relatively short-built sealing arrangements, such as rectangular labyrinth seals (for example, according to DIN 34110) be replaced. These sealing arrangements are inexpensive to produce and, due to their short overall length, also enable a reduction in the length of the shafts of the rotors and a reduction in the spacing of the bearing arrangements. This in turn results in a lower piston deflection and a reduction in the tendency to vibrational excitation during operation.

Such simple, relatively short-built sealing arrangements are used, moreover, for decades in the promotion of air and neutral gases and therefore represent proven designs that have a long service life.

According to the invention, the heating of the oil quantity and / or the housing walls forming the oil space can be effected directly or indirectly.

Thus, for example, be provided within the oil chamber, an electric heater or heating by means of heat exchangers. Such heating can also be arranged outside the housing in the region of the oil space.

In a preferred embodiment of the heating, however, the compaction heat inevitably produced during operation by the compression of the pumped medium is utilized.

Practice shows that the compression end temperature (T2) normally present on the pressure side is significantly above the oil temperature required according to the invention. Experiments have also shown that the resulting heat of compression transfers already on the housing parts on the oil, so that additional provisions for heat transfer in the invention are not necessarily required.

According to an advantageous development of the invention, the compression heat necessary to achieve the desired oil temperature can be adjusted and regulated by injecting suitable quantities of conveying medium in its liquid phase on the suction side of the rotary compressor into the delivery volume flow. For example, in the promotion of water vapor or in the promotion of the gas-steam mixture "moist air" would therefore be injected with liquid water. As a result, the fluid is not contaminated by a foreign substance and at the same time a good cooling effect is achieved by the amount of heat absorbed by the evaporation of the injected liquid. In contrast to the prior art, in this case the suction-side injection is dimensioned without taking into account the desired pressure-side process temperature (T3). If, however, this temperature (T3) is above the temperature permissible for the downstream process, according to the invention a further controlled injection of the pumped medium in its liquid phase on the pressure side of the compressor can be carried out, whereby the temperature of the pumped medium returns to the desired process temperature (T3). can be lowered.

In this case, a temperature sensor installed on the pressure side serves as a signal transmitter for the valve of the pressure-side injection of pumped liquid in its liquid phase. By means of a suitable electronic control, the pressure-side injection can then be clocked such that the desired process temperature (T3) adjusts accordingly.

If, for example, during start-up or during stationary operation of the rotary compressor, the pending compression end temperature (T2) is insufficient, an additional heating of the oil by means of external energy can take place according to the invention. This heating can - as already mentioned above - for example, electrically or via heat exchangers within the oil space or from the outside. This additional heating can also be set or regulated via a suitable electronic control as a function of the oil temperature.

According to an advantageous development of the invention, the housing is completely isolated with an insulating material.

As insulating material, any suitable material can be used. It is advantageous, however, if a glass fiber fleece is used as insulating material.

Fig. 1

zeigt in einer stark vereinfachten schematischen Darstellung einen erfindungsgemäßen Drehkolbenverdichter mit den wichtigsten Elementen seines Umfeldes in einer Gesamtanordnung, und

Fig. 2

zeigt schematisch in einer Schnittdarstellung ein Ausführungsbeispiel eines erfindungsgemäßen Drehkolbenverdichters, wie er in der Gesamtanordnung gemäß Figur 1 eingesetzt sein kann.

In the following, an exemplary embodiment of a rotary compressor designed according to the invention is described and explained in greater detail with reference to the accompanying drawings for further explanation and for better understanding.

Fig. 1

shows in a highly simplified schematic representation of a rotary piston compressor according to the invention with the most important elements of its environment in an overall arrangement, and

Fig. 2

schematically shows in a sectional view an embodiment of a rotary piston compressor according to the invention, as in the overall arrangement according to FIG. 1 can be used.

As is apparent from the schematic representation of the overall arrangement, the rotary compressor 1 is designed as a Roots compressor having two rotors, each with three wings or teeth.

The two rotors are mounted in a housing 2 which is insulated with a high temperature resistant material 3, preferably a glass fiber fleece.

Within the oil chambers 42 and 43, the electric heaters 46 and 47 are provided, the power supply is indicated by a star.

The housing 2 is further equipped with resistance sensors 4 and 5, with which the temperature of the oil in the oil chambers 43 and 42 is monitored.

The rotors of the rotary compressor 1 are driven by a shaft 6, which is in communication with a belt drive 7, which is driven by an electric motor 8, whose power supply is also indicated by a star.

A conveying medium is the suction side - as indicated by an arrow 9 - fed via an inlet pipe 10 in a conventional manner a delivery chamber of the compressor 1 and ejected from this in a pressure side arranged outlet pipe 11. The outlet pipe 11 opens into a boiler 12, which may be formed in a conventional manner as a muffler and a so-called base support, on the upper side of the rotary compressor 1, optionally with the belt drive 7 and the electric motor 8 may be arranged.

To the boiler 12, an outlet pipe 13 connects, which opens via an axial compensator 14 in a supply pipe 15 which - as indicated by an arrow 16 - supplies the fluid to the respective processing process.

The boiler 12 is equipped in a known manner with a condensate outlet 17. The outlet pipe 13 in turn has a connection 18, which leads via a shut-off valve 19 to a pressure measuring device 20.

The intake pipe 10 arranged on the inlet side is equipped with a connection 22. The port 22 also has a branch line via a pressure measuring device 23 and a solenoid valve 24, via the medium in its liquid phase, for example in the promotion of water vapor so water can be injected into the inlet pipe 10. As already mentioned, this injection is only about the Controlled discharge temperature. The compression end temperature is detected by a resistance thermometer 21 and has a direct effect on the oil temperature as described.

The supply pipe 15 arranged on the outlet side is equipped with a connection 25 for the injection of conveying medium in its liquid phase. The port 25 further has a branch line, a pressure measuring device 26 and a solenoid valve 27, can be injected via the medium in its liquid phase in the feed tube 15. As already mentioned, this injection is controlled only by the process temperature.
As it turned out FIG. 2 results, the rotors of the rotary compressor 1 via stub shafts 30, 31, 32 and 33 are mounted in the housing 2. This storage consists of rolling bearings 34, which are designed differently in a conventional manner depending on the respective load assumptions.

The rolling bearings 34 are separated from the conveying chambers of the compressor, which are formed by the inner surfaces of the housing 2 and the outer surfaces of the wings or teeth, by sealing arrangements 35, which are configured in the present case as a simple rectangular labyrinth seals.

The stub shaft 33 is extended beyond the housing 2 of the rotary compressor and with an in FIG. 2 Provided pulley, not shown, which in turn constitutes a part of the belt drive 7, which is driven by the electric motor 8.

The stub shafts 30 and 32 are also extended beyond the respective associated rolling bearings 34 and carry gears of a gear assembly 36, which ensures a non-contact synchronous operation for the rotors in a conventional manner.

The rolling bearings 34 and the sealing arrangements 35 are arranged in so-called side plates 37 and 38 of the housing, which terminate a cylindrical central portion 39 of the housing 2 at both end faces. At the side plates 37 and 38 close at the in Fig. 2 illustrated embodiment of a compressor 1, a wheel housing 40 and a housing cover 41, which shield the sealing assemblies 35 and the bearings 34 to the outside and each form an oil chamber 42, 43, arranged in which a predetermined amount of oil for lubrication of the gear assembly 36 and the bearings 34 is.

The lubrication takes place in a known manner via so-called Ölschleuderscheiben 44 and 45, which are fixed in the region of the ends of the stub shaft 32 and 31 and immersed in the oil sump of the oil space 42 and 43 arranged amount of oil.

According to the invention, the amount of oil including the housing walls forming the oil space is heated. As already described, the necessary for the heating of the oil and the oil chamber housing walls necessary energy can be obtained at least in stationary operation from the inevitably resulting compression heat on the pressure side of the rotary compressor. For this purpose, the heat of compression must be conducted into the region of the oil space, which is accomplished predominantly via the housing 2 of the rotary compressor. The temperature control takes place here by means of the injection of suitable amounts of the liquid phase of the pumped medium via the connection 22 on the suction side of the compressor.

The injection is controlled by means of a suitable electronic control which detects the compression end temperature with the aid of the resistance thermometer 21 and actuates an electromagnetically actuated valve 24. If this adjusting, detected by means of the temperature sensor 28 Process temperature is above the desired values, then takes place on the pressure side of the compressor, a further injection of fluid in its liquid phase via the port 25 and the solenoid valve 27th

On the other hand, in certain operating conditions, if the resulting heat of compression does not suffice to achieve the required oil temperature, additional heating takes place.

This additional heating takes place in the case of the embodiment according to FIG. 2 by two electric heating rods 46 and 47. The heating element 46 is arranged in the region of the oil chamber 42 of the gear arrangement 36 and the heating element 47 in the region of the oil chamber 43 on the opposite side of the housing 2.

How out FIG. 2 also shows, the housing of the rotary compressor including the housing cover 40 and 41 is completely surrounded by high temperature resistant insulating material 3, which completely isolates the rotary compressor 1 from the environment and thus reduces heat loss to the ambient air.

As already mentioned, the heating makes it possible for the temperature of the oil quantity present in the oil chambers 42 and 43, including the temperature of the housing walls forming the oil chamber, to be kept above the evaporation or condensation temperature of the pumped medium, so that condensate formation is prevented. Conveying medium which passes through the sealing arrangements 35 in the region of the rolling bearings 34 and / or in the region of the gear arrangement 36 can thus not condense. The occurring in known rotary compressor designs in this area condensation is thus prevented and thus can not mix in the oil chambers 42 and 43 with the amount of oil.

Claims (9)

1. Rotary piston compressor (1) for conveying media which contain condensing vapours or vapour/gas mixtures, preferably water vapour, having

   - two rotors each with at least two vanes or teeth,

   - a housing (2) which surrounds the rotors and which with its inner surfaces and the outer surfaces of the vanes or teeth forms conveying chambers for the conveying medium,

   - a bearing assembly (34) for the rotors which is arranged in the housing (2) and which is separated from the conveying chambers by a sealing assembly (35),

   - a gear assembly (36) for keeping the rotors free from contact during operation,

   - and an oil chamber (42, 43) for receiving at least part of the gear assembly (36) and a quantity of oil provided for the lubrication thereof,

   characterised in that
   the quantity of oil and/or the housing walls forming the oil chamber (42, 43) can be heated directly or indirectly in such a way that their temperature is above the vaporisation or condensation temperature of the conveying medium.
2. Rotary piston compressor according to claim 1, characterised in that an electric heating system (4) is provided for heating.
3. Rotary piston compressor according to claim 1, characterised in that a heat exchanger is provided for heating.
4. Rotary piston compressor according to claim 1, characterised in that heating is effected by delivery to the oil chamber (42, 43) of the heat of compression arising due to compression of the conveying medium.
5. Rotary piston compressor according to claims 1 and 4, characterised in that the temperature of the quantity of oil and of the walls forming the oil chamber (42, 43) is controlled by injection of conveying medium in its liquid phase on the suction side of the compressor.
6. Rotary piston compressor according to claim 5, characterised in that, in addition to injection on the suction side, injection on the pressure side is provided.
7. Rotary piston compressor according to one or more of the preceding claims, characterised in that the temperature of the conveying medium on the pressure side and the oil temperatures in both oil chambers are measured by means of temperature sensors.
8. Rotary piston compressor according to claim 7, characterised in that the temperature sensors are connected to an electronic control unit.
9. Rotary piston compressor according to one or more of the preceding claims, characterised in that the housing (2) is insulated with a glass fibre fleece (3).

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