EP2142806B1 - Compressor system for underwater use in the offshore area - Google Patents

Description

The invention relates to a compressor system, in particular for the promotion of gases or gas / oil mixtures in the offshore sector. The compressor system has a seawater-resistant housing with at least one access opening for gases or gas / oil mixtures to be compressed and with at least one outlet opening for the compressed gases or gas / oil mixtures. It has a compressor arranged in the housing, which is connected on the input side to the access opening and on the output side to the output opening. In the housing, an electric motor is arranged with a stator core which can be cooled via an inner side of the housing and with a rotor core for driving the compressor.

From the German patent DE 37 29 486 C1 is a compressor unit for the production of natural gas in the offshore area with drive by a high-frequency motor for the compression of gases is known, which is suitable for large water depths. The high-frequency motor of the compressor unit is magnetically mounted and drives the compressor stages in a common gas-tight housing. The cooling of the engine, the bearings and the compressor stages takes place through the liquid surrounding the common housing.

From the German patent application DE 196 23 553 A1 is a liquid-cooled electric machine is known which is designed as a submersible motor in spaltrohrloser construction and is completely filled with motor filling liquid of low viscosity. To optimize the heat distribution within the stator cooling tubes are provided which extend parallel to the air gap between the stator and rotor. The entire engine fill fluid used for cooling flows in parallel through the cooling tubes and the air gap.

From the German patent application DE 42 09 118 A1 is an electric motor with a motor pressure housing, filled with gas. under high pressure, known. In order to reduce the heat loss incurred in the electric motor, a capsule is provided which surrounds the rotor rods on the drive side and / or side.

From the French patent FR 1 181 680 A For example, a compressor is known which has a compressor unit and an electric motor driving the same via a common shaft. The shaft is mounted on a liquid cooled axle.

Offshore production, ie the extraction of oil and gas in offshore waters, places high demands on compressor systems. They have to cope with harsh climates, corrosive environmental conditions and unpredictable gas compositions. The compressor systems can be driven by an electric motor or by a gas turbine. The electric motor is preferably a brushless asynchronous motor. Usually, a high-speed turbine is used for compression, in which case the turbine and the electric motor are preferably arranged on a common shaft. The brush and gearless drive allows virtually maintenance-free operation of such compressor systems. Alternatively, screw or reciprocating compressors can be used for compression.

The considered compressor systems may be installed in coastal petrochemical facilities, on drilling platforms or under water. In the latter case, the drive of the compressor is typically carried out with an electric motor.

The supply of the gas or the gas / oil mixture is usually via a pipe which is flanged to the outside of the housing of the compressor system. In a corresponding manner, the further transport of the compressed gas or gas / oil mixture takes place on the output side via another Pipeline. Alternatively, a pressure hose can be used instead of a pipe.

The high electrical connection capacity of the electric motors used in the range of several 100 kW requires cooling of the electric motors. Typically, an oil recooling system is used, which is connected as a separate unit via oil supply lines and oil return lines to the compressor system. Such compressor systems are disadvantageously expansive because of the externally arranged oil recooling.

Another disadvantage is that the external oil recooling systems may leak over time. On the one hand, the oil feed pipes and the oil return pipes themselves may become leaky, in particular due to corrosion caused by sea water or due to mechanical effects, such as corrosion. by waves. On the other hand, pressure-tight connection connections of the pipelines to the housing of the compressor system can become leaky over time. Escaping oil and oil / gas mixtures in this context represents a potential ecological hazard to the surrounding waters.

It is an object of the invention to provide a compressor system in which the disadvantages described above are avoided.

The object of the invention is achieved by a compressor system having the features of claim 1. Further advantageous embodiments are specified in the dependent claims 2 to 6.

According to the invention, the stator core is spaced from the inside of the housing. The stator in this case forms with at least one opposite part of the inside of the housing an annular cooling chamber. In the cooling chamber, a coolant is present.

This has the advantage that the heat transfer resistance from the stator to the housing is drastically reduced because of the complete embedding of the stator in the coolant and because of the wetting of the inside of the housing with the coolant. The reason for this is that the stator pack with its particularly hot spots, such as with its axially projecting winding heads, completely immersed in the coolant. The cooling of these hot and critical points is therefore particularly effective. With "axial" directions are designated parallel to the axis of rotation of the electric motor.

Preferably, the coolant is a liquid, especially an oil, e.g. a silicone or mineral oil. In addition to the high specific heat capacity, this has an advantageous electrically insulating effect with regard to the live winding ends. Alternatively, other cooling liquids may be used, such as e.g. Water based coolants. The coolant may alternatively be a refrigerant, such as e.g. Freon® R134a. In this case, the coolant is a sol, that is, a liquid / gas mixture.

According to one embodiment, cooling passages extending essentially axially to the axis of rotation of the electric motor are provided in the stator core. As a result, cooling in the interior of the stator is possible in an advantageous manner.

According to another embodiment, the compressor system comprises a circulation pump for the coolant. By the circulation a more even and also higher cooling achievement is achieved.

According to a preferred embodiment, the compressor system for the intended use is installed such that the axis of rotation of the electric motor is substantially in the vertical direction. The same applies to the cooling channels. The present arrangement causes automatically adjusts a cooling circuit within the cooling chamber. Because the heating of the coolant in the respective cooling channels causes it to rise and flow out of the upper axial face of the stator core. Subsequent coolant forcibly conveys the heated coolant to the inside of the housing that is cold compared to the coolant temperature. The subsequent cooling causes an increase in specific gravity and a decrease in the coolant. At the lower end of the cooling chamber, the cooled coolant is sucked in the direction of the axially lower end face of the stator core. The cooling circuit is closed. At the same time, the cold outside of the outside of the housing, which has typical temperatures in the single-digit Celsius range, acts as a heat sink. The large temperature gradient between heated coolant and cold seawater causes a large heat flow from the coolant through the housing wall to the seawater.

For the purpose of directing the circulating liquid flow forming in the cooling chamber, baffles, e.g. be arranged at the axial ends of the stator.

According to a further advantageous embodiment, the housing has an outer housing side, on which a plurality of cooling fins is arranged. The cooling fins cause a significant increase in the cooling surface to the sea water. The enlarged cooling surface may, depending on the shape and number of existing cooling fins, be a multiple of the otherwise existing outer surface of the housing of the compressor system. Preferably, the cooling fins are away from the outside of the housing.

Preferably, the housing has a cylindrical shape. In this case, the heat sinks are radially away from the outside of the housing. With "radial" directions are referred to the axis of symmetry of the cylindrical housing to and away from her. Typically, the axis of symmetry coincides with the axis of rotation of the electric motor.

FIG 1

eine Schnittdarstellung eines nicht erfindungsgemäßen Verdichtersystems entlang der Drehachse eines Elektromotors und eines Verdichters,

FIG 2

eine Schnittdarstellung eines erfindungsgemäßen Verdichtersystems,

FIG 3

eine Schnittdarstellung eines Verdichtersystems gemäß einer Ausführungsform der Erfindung und

FIG 4

eine Seitenansicht des Verdichtersystems gemäß FIG 3 entsprechend der in FIG 3 eingezeichneten Blickrichtung IV.

Further advantageous features of the invention will become apparent from the exemplification thereof with reference to the figures. Show it

FIG. 1

a sectional view of a non-inventive compressor system along the axis of rotation of an electric motor and a compressor,

FIG. 2

a sectional view of a compressor system according to the invention,

FIG. 3

a sectional view of a compressor system according to an embodiment of the invention and

FIG. 4

a side view of the compressor system according to FIG. 3 according to the in FIG. 3 marked line of vision IV.

FIG. 1 shows a sectional view of a non-inventive compressor system 1 along the axis of rotation DA of an electric motor 7 and a compressor eighth

The in the figures 1 to FIG. 3 shown compressor systems are designed in particular for the promotion of gases and / or gas / oil mixtures in the offshore sector. In particular, a housing 2 is seawater resistant. The housing 2 is preferably made of steel and may have a protective coating to prevent corrosion. The steel used may alternatively or additionally be a stainless steel. Alternatively, the housing 2 may be made of a seawater resistant aluminum. Preferably, the housing is pressure-tight, in accordance with the intended for operation of the compressor system 1 depth of use under the sea water level or on the seabed. The pressure-tight requirements relate not only to the housing 2 itself, but also implementations in the housing, such as for power and control cables for power supply and for controlling and / or monitoring of the compressor system. 1

The housing 2 has, for example, an access opening 3 for the gases or gas / oil mixtures to be compressed and an outlet opening 4 for the compressed gases or gas / oil mixtures. Alternatively, a plurality of openings 3, 4 may be present. At the two openings 3, 4 are usually connecting elements, such as couplings or flanges, mounted in order to connect to these pipes or pressure hoses. The connection elements and the pipes are to be designed in a technically robust manner with regard to the respectively required pressure tightness.

In the housing 2, the compressor 8 is arranged, which is the input side connected to the access opening 3 and the output side to the output port 4. The arrows shown in the region of the openings 3, 4 indicate the flow directions. In the example of FIG. 1 For example, the compressor 8 has a turbine 81 with turbine blades not further specified. Their diameter decreases in the axial direction, that is, in the flow direction, whereby the pressure increases due to the compression at the same time. The reference numeral 83 denotes a high-pressure discharge. From there, via a pipe connection, not further described, inside the housing 2, the transport of the compressed gas to the exit opening 3 takes place.

In the housing 2, the electric motor 7 is further arranged for driving the compressor 8. The electric motor 7 has a stator 71 and a rotor package 72. Furthermore, in the example of the FIG. 1 both the compressor 8 and the electric motor 7 on a common, guided in bearings 6 shaft 5.

The stator 71 of the electric motor 7 is cooled via a housing inner side GI of the housing 2 of the compressor system 1. In the example of FIG. 1 cooling takes place via a stator outer side SA, which rests flush against the inside of the housing GI. The arrows entered in the contact area between the outside of the stator SA and the inside of the housing GI symbolize the heat flow. To increase the cooling capacity, can between the stator outside SA and the inside of the housing GI be introduced a good thermal conductivity mass, such as a good thermal conductivity paste, a grease or the like.

The compressor system 1 shown is installed such that the axis of rotation DA of the electric motor 7 extends substantially in the vertical direction. It can alternatively be aligned in a horizontal position.

Furthermore, the housing 2 has a housing outside GA, on which a plurality of projecting cooling fins 21 is arranged. In the present case of a cylindrical design of the housing 2, the cooling fins 21 are radially away from the housing outside GA. Also, the compressor system 1 according to the invention and an embodiment according to FIG. 2 and FIG. 3 have such a cylindrical design.

FIG. 2 shows a sectional view of a compressor system according to the invention 1. The compressor system 1 shown is in turn mounted vertically with respect to the axis of rotation DA of the electric motor 7.

In contrast to the compressor system according to FIG. 1 is the stator 71 according to the invention from the inside GI of the housing 2 spaced. The mean radial distance is preferably in a range of 5 cm to 15 cm. Depending on the electrical connection performance of the electric motor 7, the distance values can also be above, for example, at 20 cm, or below, such as at 3 cm. The stator 71 forms with at least one opposite part of the housing inner side GI an annular cooling chamber 9, in which a coolant 9 is present. In the cooling chamber 9 are also the winding heads 73 of the stator 71, which protrude axially from the stator 71. The cooling chamber 9 has in the example of FIG. 2 only one chamber up. It may alternatively have a plurality of chambers, in which case adjacent chambers are separated from each other by a radially axially extending bulkhead.

The cooling chamber 9 is formed by two ripeness 91, 92 and a circular disk 94. The two ripen 91, 92 have an inner diameter which corresponds to the inner diameter of the stator 71. The first hoop 91 is sealed to a lower axial end face of the stator pack 71, such as e.g. welded. The axis of symmetry of this hoop 91 is aligned with the axis of rotation DA of the electric motor 7. The axial height of the first hoop 91 corresponds to almost the axial distance of the stator 71 to a bottom plate 22 of the housing 2. The lower edge of the first hoop 91 can via a sealing ring 93 for Bottom plate 22 to be sealed towards sealed or welded to the bottom plate 22.

The second hoop 92 is similarly attached to the upper axial end of the stator core 71. The circular disk 94 has an inner diameter which corresponds approximately to the inner diameter of the maturity 91, 92. The outer diameter corresponds approximately to the inner diameter of the housing 2. The second hoop 92 and the circular disk 94 are preferably welded together tightly and together form a flange 92, 94. The outer edge of the circular disk 94 and the flange 92, 94 can via another Gasket 95 may be sealed to the inside of the housing GI or tightly welded to the inside of the housing GI. The maturity 91, 92, the circular disk 94, a radial inner side of the stator core 71 and the inside of the housing GI thus form a hollow cylinder.

In the cooling chamber 9, a coolant, preferably an oil, is present as the cooling fluid. In particular, a so-called transformer oil based on mineral oil or silicone oil comes into consideration. Preferably, the entire cooling chamber 9 is filled with the cooling liquid. In the housing 2 and outside the cooling chamber 9, a compensating vessel for the cooling liquid may be present to compensate for a temperature-induced change in volume of the coolant.

The coolant may alternatively be a refrigerant, such as a Freon®. It is particularly advantageous in terms environmental compatibility a CFC-free Freon®, such as Freon® R134a. In this case, the cooling chamber 9 is filled with a sol, that is, with a liquid / gas mixture.

Furthermore, cooling passages 75 extending essentially axially to the axis of rotation DA of the electric motor 7 are present in the stator pack 71. Because of the embedding of the stator 71 in the coolant, these are also filled with the coolant. During operation of the compressor system 1, a circulation of the coolant in the cooling chamber 9 is established. This is represented by flow arrows. In this case, the coolant heated in the cooling channels 75 rises upward and cools in the reverse direction from top to bottom along the cold inside of the housing GI again. In this case, the thermally particularly critical winding heads 73 are surrounded by the circulating coolant and thus effectively cooled.

The horizontal arrows symbolize the heat transfer from the coolant, continue on the wall of the housing 2 in the sea water, which surrounds the outside of the housing GA 2. The adjusting in the cooling chamber 9 cooling circuit can also be referred to as a primary cooling circuit, while adjusts to the outside of the housing, but only in the case of a stationary water, a counterflow, which sweeps from bottom to top along the outside of the housing GA. The cooling by the seawater can also be called secondary cooling.

To further increase the cooling capacity, the compressor system 1 may comprise a circulation pump for the coolant. The circulating pump is e.g. a centrifugal pump which is mounted in or on the cooling chamber 9.

In comparison to FIG. 1 the cooling fins 21 are formed on the outside of the housing 2 GA shorter in length. They extend only in the axial "hot" region of the housing 2, which is opposite to the cooling chamber 9. The cooling of the compressor 8 takes place in this context on the gases to be compressed or gas / oil mixtures themselves.

FIG. 3 shows a sectional view of a compressor system 1 according to a third embodiment of the invention.

In comparison to FIG. 2 the cooling chamber 9 is substantially torus-shaped, wherein the cooling chamber 9 curved cooling chamber walls 96, 97 which favor the circulating flow through their shape. The cooling capacity of this embodiment is therefore larger in comparison to the second embodiment with the same construction volume. The cooling chamber walls 96, 97 fulfill in addition to the formation of the cooling chamber 9 and a Strömungsleitfunktion. Reference numerals 98, 99 denote further sealing rings for sealing the cooling chamber walls 96, 97 with the inside of the housing GI. Alternatively, the cooling chamber walls 96, 97 may be tightly welded to the inside of the housing GI.

FIG. 4 shows a side view of the compressor system 1 according to FIG. 3 according to the in FIG. 3 marked line of vision IV.

FIG. 4 shows the view into the access opening 3, that is in the direction of the compressor. As FIG. 4 shows further, the stator 71 has a plurality of circumferentially uniformly distributed cooling channels 75 on. The cooling channels 75 are arranged with respect to their radial position to the winding heads 73 on both sides of the winding heads 73 (see also FIG. 2 and FIG. 3 ). The arrangement of the cooling channels 75 is preferably carried out in the magnetically less active region of the stator 71. The plurality of cooling channels 75 allows effective cooling of the stator 71 from the inside out.

On the outer side of the housing GA there is a large number of cooling fins 21 arranged radially away from the outside of the housing to see. The cooling fins 21 cause a drastic increase in the cooling surface available for cooling by seawater. Preferably, the cooling fins 21 are an integral part of the housing 2 of the compressor system 1. In particular, the housing 2 is made of a casting.

The compressor system according to the invention is also suitable for high-speed compressor systems at speeds of up to 15,000 rpm and powers of a few 100 kW up to 10 MW and more.

Claims (6)

1. Compressor system, especially for transporting gases or gas/oil mixtures in the offshore area, with a seawater-proof housing (2) with at least one entry opening (3) for the gases or gas/oil mixtures which are to be compressed, and with at least one discharge opening (4) for the compressed gases or gas/oil mixtures, with a compressor (8) which is arranged in the housing (2) and which on the inlet side is connected to the entry opening (3) and on the outlet side is connected to the discharge opening (4), and with an electric motor (7), which is arranged in the housing (2), with a stator packet (71) which can be cooled via an inner side (GI) of the housing (2), and with a rotor packet (72) for driving Compressor (8),
   characterized in that

   - the stator packet (71) is at a distance from the inner side (GI) of the housing (2),

   - the stator packet (71) with at least one oppositely disposed part of the housing inner side (GI) forms an annular cooling chamber (9), and

   - a cooling medium is provided in the cooling chamber (9).
2. Compressor system according to Claim 1, characterized in that the cooling medium is an oil.
3. Compressor system according to Claim 1 or 2, characterized in that cooling passages (75) which extend essentially axially to the rotational axis (DA) of the electric motor (7) are provided in the stator packet (71).
4. Compressor system according to one of the preceding claims, characterized in that Compressor system has a circulating pump for the cooling medium.
5. Compressor system according to one of the preceding claims, characterized in that Compressor system in the asintended application is installed in such a way that the rotational axis (DA) of the electric motor (7) extends essentially in the vertical direction.
6. Compressor system according to one of the preceding claims, characterized in that the housing (2) has a housing outer side (GA) and a multiplicity of cooling fins (21) are arranged on the housing outer side (GA).

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