Abstract:
The invention relates to a double-flow screw spindle machine for drive generation by multiphase mixtures or for the delivery of multiphase mixtures, comprising at least two separate inlet chambers ( 11, 12 ) and an outlet chamber ( 20 ), and a separator ( 30 ), situated upstream of the inlet chambers ( 11, 12 ), for separating liquid phase and gas phase. The object of the present invention is to provide a dual-flow screw spindle machine which is easily adaptable to changed process conditions. This object is achieved by virtue of the fact that both inlet chambers ( 11, 12 ) are connected to the separator ( 30 ) by separate lines ( 31, 32; 33 ) for the gas phase and the liquid phase.

Description:
FIELD OF THE INVENTION 
     The invention relates to a double-flow screw spindle machine for drive generation by multiphase mixtures or for the delivery of multiphase mixtures, comprising at least two separate inlet chambers and an outlet chamber, as well as a separator, situated upstream of the inlet chambers, for separating liquid phase and gas phase. 
     BACKGROUND 
     WO 94/27049 A1 describes a double-flow multiphase screw spindle machine for the delivery of a multiphase mixture. As the feed elements, two contactlessly intermeshing, contrarotating feed screw pairs are provided, respectively comprising a right-hand feed screw and a left-hand feed screw. The interlocking feed screws form, together with the housing enclosing them, individually closed-off feed chambers. Upon rotation via a drive shaft, these chambers move continuously and parallel to the shafts from the suction side to the pressure side. The suction side is here arranged centrically, with the pressure chamber surrounding the feed spindles. In the pressure chamber, devices for separating the respective liquid phase from the gas phase of the medium flow leaving the feed screw are provided. A part-quantity of the separated liquid phase is led back to the suction chamber via a short-circuit line. 
     EP 183 380 A1 describes a double-flow screw spindle pump having an inlet chamber disposed on the front of the feed screw pairs. The medium to be pumped is moved into convergence by the two feed screw pairs and is discharged from a centrally disposed outlet. A similarly constructed screw spindle pump is known from GB 2,227,057 A1. Condensers for vaporized fluid are provided within the housing in order to provide an adequate liquid supply. 
     U.S. Pat. No. 4,995,797 describes a single-flow screw spindle pump having a pressure-controlled return flow of a separated liquid component. The separator is disposed on the pressure side of the pump. 
     SUMMARY 
     In a double-flow multiphase screw spindle motor, the multiphase fluid is conducted through the screw spindles. The fluid flows in the inlet chambers must have a minimum liquid component in order to seal the gaps between the screw spindles and the housing. The inlet pressure in the inlet chambers is higher than the outlet pressure. The hydraulic energy is converted into mechanical energy, for example in order to drive a generator. 
     The object of the present invention is to provide a dual-flow screw spindle machine which is easily adaptable to changed process conditions. 
     According to the invention, this object is achieved by a dual-flow screw spindle machine having the features of the main claim. Advantageous embodiments and refinements of the invention are described in the subclaims. 
     The inventive dual-flow screw spindle machine for drive generation by multiphase mixtures or for the delivery of multiphase mixtures, comprising two separate inlet chambers and an outlet chamber, and a separator, situated upstream of the inlet chambers, for separating liquid phase and gas phase provides that both inlet chambers are connected to the separator by separate lines for the gas phase and the liquid phase. As a result of the separate feed of the separated gas phase and separated liquid phase to the two inlet chambers, it is possible to enable a precise control of the liquid supply to the screw spindles. The liquid phase serves to seal the gaps between the screw spindles and between the screw spindles and the housing. The supply of liquid to the screw spindles can thus be realized directly and requires no admixture to the gas phase. 
     A switching device for interrupting the liquid supply to an inlet chamber can be provided, so that, given high gas phases and a low fill level in the separator, only one feed screw pair is supplied with liquid, so that, during operation as a hydraulic motor, this runs on at reduced power and, during operation as a feed pump, a reduced pumping capacity is provided. 
     Outlets for connecting lines from the separator to the inlet chambers for the liquid phase can be arranged at different levels in the separator, so that automatically, should a liquid component in the feed flow or in the separator fall below a certain level, namely beneath the level of the upper outlets, only the liquid phase is fed through the outlet at the lower level, so that the liquid phase is automatically conducted into one of the inlet chambers only via this connecting line. 
     A switching valve can be disposed in or on a connecting line or in or on the separator, so that the supply of liquid phase to the screw spindle can be controlled via the switching valve. 
     A storage chamber and a surge chamber, which are fluidically connected to each other, can be formed in the separator. The multiphase mixtures makes its way into the surge chamber directly from a pipeline, for example from a feed pipe of a hydrocarbon source. In the surge chamber, a first separation of liquid phase and gas phase takes place. From the surge chamber, the liquid phase and the gas phase make their way into a storage chamber, which serves to ensure that an adequate supply of liquid is present on the inlet side of the screw spindle machine. In the storage chamber, the liquid phase, due to the different densities, is deposited on the base, while the gas phase of the multiphase mixture is located above the liquid phase in the separator, in particular in the storage chamber. From the storage chamber, separate lines for the gas phase and the liquid phase then run to the inlet chambers of the screw spindle machine. 
     A splash wall having a low-situated passage opening can be disposed in the separator, so that the liquid phase already deposited in the surge chamber can flow through the passage opening into the storage chamber. In addition to the low-situated passage opening, further openings can also be present in the splash wall in order to conduct the gas phase from the surge chamber to the storage chamber, for example. 
     A blocking device can be disposed in or on a connecting line for the gas phase from the separator to an inlet chamber, so that separately or in addition to a blocking of the liquid phase, the gas phase, at least to one inlet chamber, can also be blocked. One complete side of the screw spindle machine can thereby be decoupled from the feed flow, so that the machine can be operated only at half power. 
     The machine is configured either as a motor or as a pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the invention are explained in greater detail below with reference to the appended figures. The same reference symbols denote the same structural elements. 
       FIG.  1 —shows a schematic representation of a screw spindle machine as a motor; 
       FIG.  2 —shows a schematic representation of the screw spindle machine given a first liquid level; 
       FIG.  3 —shows a representation according to  FIG. 2  with a lowered liquid level; 
       FIG.  4 —shows a variant of the embodiment according to  FIG. 3  with a switching device; and 
       FIG.  5 —shows a variant of  FIG. 3  with a switching device and a blocking device in a gas line. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a screw spindle machine  1  in the form of a dual-flow multiphase screw spindle motor is shown in a schematic representation. The screw spindle machine has two separate inlet chambers  11 ,  12 , via which screw spindle pairs, of which only two screw spindles  2 ,  4  are shown in  FIG. 1 , are supplied with a multiphase mixture. In the embodiment as a motor, the inlet pressure p 1  is greater than the outlet pressure p 2  abutting on an outlet chamber  20 , so that, as a result of the differential pressure, no liquid can be fed back onto the inlet side. The spindles  2 ,  4  drive a generator  6 ; should the machine be run in pump operation, the spindles  2 ,  4  are coupled to a motor. 
     For the sealing of the gaps between the feed screws  2 ,  4  and between the feed screws  2 ,  4  and a housing wall enclosing the feed screw pairs, a minimal liquid component of the feed medium is necessary. In motor operation, the component can, for example, be greater than 30% of the total feed volume. Owing to the occurring variations in the phase composition in multiphase mixtures, i.e. given a fluctuating liquid phase and gas phase percentage between 100% liquid component and 100% gas component, a liquid supply must be provided on the inlet side in the pipeline in front of the screw spindle machine. A liquid supply is provided in the form of an upstream separator having a storage chamber. The pipeline leads directly into the separator, without the fluid having previously passed through the screw spindle machine. 
     A schematic representation of such a construction is represented in  FIG. 2 . The screw spindle pairs  2 ,  3  and  4 ,  5  are represented schematically, as are the two separate inlet chambers  11 ,  12 , which on the inlet side cooperate with the screw spindle pairs  2 ,  3 ,  4 ,  5 . Mounted upstream of the inlet chambers  11 ,  12  and the screw spindle pairs  2 ,  3 ,  4 ,  5  is a separator  30 , which is coupled to the inlet chambers  11 ,  12  via connecting lines  31 ,  32 ,  33 . The separator  30  has a surge chamber and a storage chamber  35 . The multiphase mixture makes its way into the surge chamber  36  from a pipeline, for example a feed line, as is indicated by the right-hand arrow. The surge chamber  36  is separated from the storage chamber  35  by a splash wall  37 . In the splash wall  37  is disposed a low-situated passage opening  38  in the form of a bore or a cutout. Through the low-situated passage opening  38 , the liquid phase deposited on the base of the separator  30  makes its way into the storage chamber  35 . An upper through opening is likewise provided in the splash wall  37 . The upper through opening  39  has a larger flow area than the low-situated passage opening  38  and serves primarily for the passage of the gas phase. In the event of a high liquid component in the supplied multiphase flow, the liquid phase also makes its way through the upper through opening  39 . 
     An upper connecting line  33  serves for the supply of the gas phase from the separator  30  to the respective inlet chambers  11 ,  12 . The connecting line  33  has a branching, so that both inlet chambers  11 ,  12  are subjected to the same gas pressure. The two inlet chambers  11 ,  12  of the screw spindle machine are thus connected on the gas side via the separator  30 , so that the inlet pressure is equal on both sides and a hydraulic pressure equalization of the screw spindle pairs  2 ,  3 ,  4 ,  5 , i.e. of the rotors, remains assured. 
     On the bottom side, the connecting lines  31 ,  32  for the liquid phase are disposed on the separator  30 . In the represented illustrative embodiment, two separate connecting lines  31 ,  32 , which effect a separate feed of the liquid phase to the inlet chambers  11 ,  12 , are provided. The connecting lines  31 ,  32  project into the separator  30 , and there into the storage chamber  35 , wherein the outlets  311 ,  321 , i.e. the openings of the connecting lines  31 ,  32  into the storage chamber  35 , are located at different levels, i.e. in different height positions. In the represented illustrative embodiment, the connecting line  31  having the outlet  311  is disposed at a higher level than the connecting line  32  having the outlet  321 . This arrangement at different levels serves as a switching device, which interrupts the liquid supply to one inlet chamber  11  as soon as the liquid level in the storage chamber  35  falls beneath the level of the outlet  311  of one connecting line  31 . 
     The fill level  34  of the liquid phase in the storage chamber  35  of the separator  30  communicates with the fill level of the inlet chambers  11 ,  12  at the screw spindle inlets of the screw spindle machine, in particular if the separator  30  is located at the same level as the inlet chambers  11 ,  12 . The feed screw pairs  2 ,  3 ,  4 ,  5  receive the necessary liquid quantity directly from a liquid sump in the storage chamber  35 . If need be, a metering device can be provided within the liquid sump or in one of the connecting lines  31 ,  32 . Insofar as no metering device is present, the feed screw chambers are filled with a greater or lesser amount of liquid according to the fill level of the storage chamber  35 . 
     On the bottom side, at different levels, the liquid is thus drawn from the separator  30 , so that no mixing device for the gas phase and the liquid phase is present. In the upper region of the separator  30 , the gas phase is fed via the connecting line  33  to the inlet chambers  11 ,  12  of the screw spindle machines, preferably from above, separately from the liquid phase. By influencing the flow resistances in the connecting lines  31 ,  32 ,  33 , for example by control fittings, it is possible to influence the storage characteristics of the separator  30 . In the event of very high liquid components in the feed flow, the liquid phase can also be supplied via the upper connecting line  33 , so that liquid quantities which can no longer be supplied through the lower connecting lines  31 ,  32  can be fed to the screw spindle machine, for example the hydraulic motor or the pump, via the upper connecting line  33 . 
     If the liquid component in the feed flow falls below the liquid quantity necessary for both feed screw pairs  2 ,  3 ,  4 ,  5 , i.e. beneath the outlet opening  311  of one connecting line  31 , the liquid which is still available is fed to just one feed screw pair  2 ,  3 . Hence it is also possible for just one feed screw pair to perform hydraulic work, while the other feed screw pair  4 ,  5  acts as a gas throttle and thus automatically draws off the surplus gas component. In the operating mode as a motor, the power output drops, yet a controlled operation with approximately equal rotation speed is maintained. 
     If the liquid component in the total feed flow and in the storage chamber  35  of the separator  30  falls beneath the level of the lowest outlet  321 , which is preferably disposed at the lowest point of the storage chamber  35 , then a liquid phase is no longer available to seal the gaps between the feed screw pairs  2 ,  3 ,  4 , and between the feed screws  2 ,  3 ,  4 ,  5  and the housing  10 , so that in motor operation, the screw spindle machine stands idle. 
     In  FIG. 3 , the situation in which the liquid phase is at a level which lies beneath the upper outlet  311  is shown. Liquid phase is now conducted just through the lower outlet  321  through the connecting line  32  to an inlet chamber  12  and there seals the gaps between the feed screw pairs  2 ,  3  and between these and the housing  10 . The second inlet chamber  11  is not supplied with liquid phase, but only with gas phase from the upper connecting line  33  and the separate connecting line  31  which is actually provided for the liquid phase, so that a sealing of the gap between the feed screw pairs  4 ,  5  does not take place, with the inlet side serving merely as a gas throttle. 
     A variant of the invention is shown in  FIG. 4 . The outlets  311 ,  321  are located at an approximately same level, for example in the base of the separator  30 . In a connecting line  31 , a switching valve  40  is disposed, which closes once a predetermined fill level, detected, for example, by a sensor, is reached, so that only one inlet side is supplied with liquid phase. Switching valves  40  can also be provided in both connecting lines  31 ,  32  for the liquid phase, which switching valves can be alternately switched over, so that, in the event of a low liquid component and a correspondingly low level within the storage chamber  35 , one feed screw pair is operated on an alternating basis without sealing and liquid supply, while the other feed screw pair acts as a gas throttle. 
     A further variant is represented in  FIG. 5 , in which a blocking device  331  in the form of a switching valve or shut-off valve is disposed within the connecting line  33  for the gas phase. Particularly in conjunction with a switching valve  40  within a connecting line for a liquid phase, such an arrangement can be used to switch from a dual-flow operation to a single-flow operation, so that at least sufficient liquid is present to seal off a screw spindle pair by means of the liquid phase. In principle, it is also possible to furnish both inlet chambers  11 ,  12  with appropriate blocking devices  331 , so that, separately, an inlet chamber  11  can respectively be completely switched off via the blocking device  331  and the switching valve  40 . This presumes four shut-off devices in the form of two switching valves  40  and two blocking devices  331 . In an arrangement comprising outlets  311 ,  321  of different height, blocking devices  331  and/or switching valves  40  can likewise be provided. 
     Apart from use as a motor, the screw spindle machine  1  can also be operated as a pump. 
     The advantage of an above-described embodiment consists in the separation of the gas phase and liquid phase separation functions and in the generation of the hydraulic power. As a result of an almost freely selectable separation chamber  36  and a storage chamber  35 , an adaptation to the respective feed or work process is possible, while there is also the possibility of varying the respective volume of the storage chamber  35  and the surge chamber  36  through an adjustable or displaceable arrangement of the splash wall  37  within the separator  30 . 
     The separator  30  can be of tubular configuration, for example, so that it can be very cheaply produced with a relatively small diameter and a thin wall. No separate devices for injecting liquid phase into the respective inlet chamber  11 ,  12  are necessary, while the equipment costs for a correct percentage mixture of liquid phase and gas phase are likewise eliminated. The separator can directly adjoin the housing for the feed screw pairs and is preferably of cylindrical construction, for example with a diameter corresponding to the tip diameter of the feed screw pairs. The volume of the separator is then defined by an alteration of the structural length.