Machine for Expanding or Compressing Compressible Media

This application is a continuation of international application number PCT/EP2022/087620 filed on 22 Dec. 2022.

The present disclosure relates to the subject matter disclosed in international application number PCT/EP2022/087620 of 22 Dec. 2022, which is incorporated herein by reference in its entirety and for all purposes.

The invention relates to a machine for expanding or compressing compressible media, said machine comprising a machine casing, at least one screw rotor which is arranged in a screw rotor bore in the machine casing and which extends between a low-pressure side and a high-pressure side of the screw rotor bore and which cooperates with the compressible medium, wherein by rotating about a screw rotor axis the at least one screw rotor conveys the substantially gaseous medium either from the low-pressure side to the high pressure side by compressing it, or from the high-pressure side to the low pressure side by expanding it, wherein said at least one screw rotor is mounted on both sides in the machine casing by means of a respective bearing set, wherein each bearing set has at least one radial acting bearing and at least one of the bearing sets has at least one axially acting bearing that supports the at least one screw rotor to counter an axial displacing movement of said screw rotor from its operating position in the direction of the low-pressure side, wherein a motor generator unit is coupled or couplable to the at least one screw rotor.

Such compressible media are for example substantially gaseous media.

Machines of this kind are known from the prior art. These machines have the problem that the axially acting bearings only support the screw rotors axially against displacement in the direction of the low-pressure side but not in the direction of the high-pressure side so that during a switch on or a switch off procedure or in the event of an interruption to operation or an incorrect direction of rotation the problem arises that the screw rotors can come into abutment with the machine casing on the high-pressure side and as a result can become damaged.

In accordance with an embodiment of the invention, a machine of the type mentioned before is improved such that these problems do not longer arise.

In accordance with an embodiment of the invention, provision is made that the at least one screw rotor is axially supported by a lubricant support film provided between an end wall surface limiting said screw rotor bore and the high-pressure end face of said at least one screw rotor in order to prevent the high-pressure end face from making contact to the end wall surface and wherein the lubricant support film is maintained between said high-pressure end face and said wall surface by a lubricant supply unit.

Due to the maintenance of said lubricant support film between said end wall surface and the high-pressure end face contact of these faces due to the maintained axial support by the lubricant support film can be avoided.

In particular the invention makes it possible to act on the at least one screw rotor such that the axially acting bearing is constantly biased in the direction of the low-pressure side by the lubricant support film and thus as a whole a precise axial guiding of the at least one screw rotor is maintained.

In a simplified embodiment the lubricant support film is maintained permanently.

However, in a more sophisticated version it is also possible to maintain the lubricant support film at least in those phases of operation when there is a risk of contact of the faces.

In particular the lubricant support film is maintained by supplying lubricant to a support area which is arranged between said high-pressure end face of said respective screw rotor and said end wall surface and between an innermost diameter of the high-pressure end face and a radially outwardly arranged circular boarder line.

The advantage of this solution has to be seen in the fact that the outwardly arranged circular boarder line is a line having a continuous radius with respect to the screw rotor axes which helps maintaining the lubricant support film in the support area so that rotation of the screw rotors will not interrupt the lubricant support film as it would be the case if the radially outwardly arranged border line would deviate from a circular contour.

In particular it is of advantage if said circular border line is arranged radially outward from said innermost diameter of said high-pressure end face at maximum at a radially innermost root of the screw contour of said at least one screw rotor.

Further it is of advantage if said innermost diameter of said high-pressure end face is defined by an outer diameter of a pin section of said at least one screw rotor extending beyond said high-pressure end face.

It is in particular of advantage if said support area extends until said pin section of said at least one screw rotor on order to improve a sealing between said pin section and a bore in said end walls of said bearing casing by supplying lubricant thereto.

In connection with the explanation of the inventive concept concerning the lubricant support film it has not been defined in detail how said lubricant support film is to be maintained.

One advantageous solution provides that said lubricant support film within said support area is maintained by a supply of lubricant to said support area by at least one supply opening of said lubricant supply unit.

Such a supply opening can be arranged at different locations.

One advantageous solution provides that said at least one supply opening of said lubricant supply unit is arranged in the high-pressure end face of said at least one screw rotor.

Alternatively, or additionally one advantageous solution provides that said at least one supply opening of said lubricant supply unit is arranged in the end wall surface of the machine casing.

This arrangement has the advantage that the at least one supply opening can be arranged stationary in a region with advantageous pressure relationship in the environment of said supply opening.

In particular in order to maintain a quite stable lubricant support film it is of advantage if said at least one supply opening is facing the support area so that the lubricant is directly supplied to the support area for distribution therein to the lubricant support film.

Another advantageous solution according to the present invention provides that said at least one supply opening extends to an area close to said circular border line.

This means that said supply opening will be arranged radially inside said circular border line.

However, it would be also possible that said at least one supply opening is arranged partially outside said support area adjacent to or overlapping with said circular border line so that the lubricant will enter the support area.

In the preceding embodiments the shape of the at least one supply opening has not been specified.

In general, the at least one supply opening can have any shape.

An advantageous embodiment provides that said at least one supply opening has a longitudinal shape in order to allow an equal distribution of lubricant within said support area.

In particular the longitudinal shape extends transverse to said circular border line.

Another advantageous embodiment provides that the at least one supply opening extends between the circular border line and the innermost diameter, in particular starting and ending at a distance from the circular border line and the innermost diameter or even starting and/or ending adjacent the circular border line and/or the innermost diameter.

The lubricant for the lubricant supply film in principle could be supplied at a pressure which could be lower than the high-pressure at the high-pressure opening.

However, in order to provide a strong enough lubricant support film it is provided said lubricant is supplied to said lubricant support film in the support area at least at a pressure corresponding to the high-pressure at the high-pressure opening.

In order to enhance the supply of lubricant to the lubricant support film it is provided that the at least one supply opening is arranged in a region of said support area which is opposite to a high-pressure opening in said machine casing at said high-pressure side because the pressure of the gaseous medium surrounding the supply opening on this side is lower than the high-pressure close to said high-pressure opening so that a significant pressure gradient is available for the supply of lubricant to said support area.

In particular it is of advantage if said at least one supply opening is arranged in a region of said support area which is situated on a side of a screw rotor bore of said at least one screw rotor opposite to said high-pressure opening.

In particular it is of advantage if said at least one supply opening is arranged in a region of said support area on a side of the bearing pin section of said screw rotor or the screw rotor axis which region is opposite to said high-pressure opening because in this region of the support area the pressure in the surrounding of the supply opening is significantly lower than the high-pressure at said high-pressure opening, so that the pressure gradient for the supply of lubricant is close to the maximum available gradient in the support area.

In connection with the embodiments disclosed herein it has not been defined how said lubricant supply unit guides the lubricant to said at least supply opening.

One advantageous solution provides that said lubricant supply unit comprises a channel extending to said at least one supply opening.

In particular said channel can extend through said machine casing to the at least one supply opening arranged in said respective end wall surface.

Alternatively, it is provided that said channel extends through said at least one screw rotor to the supply opening arranged in said high-pressure end face of said at least one screw rotor.

In order to supply lubricant to said lubricant supply opening which is in a more or less condensed stage said lubricant supply unit comprises a lubricant reservoir comprising an accumulation of lubricant therein and wherein said lubricant accumulation being connected to said channel extending to said lubricant supply opening.

In order to impose pressure on said lubricant accumulation, one solution provides that said lubricant accumulation is exposed to the high-pressure of the gaseous medium at the high-pressure opening.

Another advantageous solution provides that the lubricant accumulation is arranged in a lubricant separator which can be arranged for example subsequent to said machine in a pipe for guiding the compressed gaseous medium.

Another advantageous solution provides that said lubricant separator is arranged in said machine casing in particular integrated therein.

In order to provide a defined pressure for the supply of lubricant a version of the lubricant supply unit comprises a lubricant pump for feeding lubricant to the lubricant supply opening.

The inventive concept can be implemented alone or in combination with support units acting on the respective pin sections in directions away from the high-pressure side towards low-pressure side.

Further features and advantages of the invention form the subject matter of the description below and the representation in the drawings of some exemplary embodiments.

In particular, advantageous embodiments of the invention comprise the combination of features s defined by the following consecutively numbered embodiments.

1. A machine for expanding or compressing compressible media, comprising a machine casing (), at least one screw rotor (,), which is arranged in a screw rotor bore (,) in the machine casing () and which extends between a low pressure side () and a high pressure side () of the screw rotor bore (,) and which cooperates with the compressible medium, wherein by rotating about a screw rotor axis (,), the at least one screw rotor (,) conveys the substantially gaseous medium either from the low pressure side () to the high pressure side () by compressing it, or from the high pressure side () to the low pressure side () by expanding it, wherein said at least one screw rotor (,) is mounted on both sides in the machine casing () by means of a respective bearing set (,,,), wherein each bearing set (,,,) has at least one radial acting bearing () and at least one of the bearing sets (,) has at least one axially acting bearing () that supports the at least one screw rotor (,) to counter an axial displacing movement of said screw rotor (,) from its operating position in the direction (,) of the low pressure side (), wherein a motor/generator unit () is coupled or couplable to the at least one screw rotor (,), characterized in that the at least one screw rotor (,) is axially supported by a lubricant support film () provided between an end wall surface (,) limiting said screw rotor bore (,) and the high pressure end face (,) of said at least one screw rotor (,) in order to prevent the high pressure end face (,) from making contact to the end wall surface (,), and wherein the lubricant support film () is maintained between said high pressure end face (,) and said end wall surface (,) by a lubricant supply unit (,).

2. Machine according to embodiment 1, wherein the lubricant support film () is maintained by supplying lubricant to a support area (,) which is arranged between said high pressure end face (,) of said respective screw rotor (,) and said end wall surface (,) and between an innermost diameter (,) of the high pressure end face (,) and a radially outwardly arranged circular border line (,).