Patent Publication Number: US-9840915-B2

Title: Turbine

Description:
TECHNICAL FIELD 
     The present invention generally relates to a turbine for expanding a pressurized vapour, in particular to a turbine with vapour induction in at least one intermediary turbine stage. 
     BACKGROUND ART 
     Due to the general necessity to reduce CO2 emissions and to the loss of trust in nuclear power plants, devices for producing electricity with low temperature sources are gaining of importance. Low temperature sources include e.g. industrial waste heat, low temperature geothermal heat sources, low temperature biomass energy and low temperature solar energy, but also novel low temperature heat generators based on chemical or nuclear reactions. 
     Such devices generally work according to a so-called Organic Rankine Cycle (ORC), i.e. a Rankine cycle in which the working fluid is an organic fluid with a lower evaporation temperature than water. The working principle underlying the ORC is basically the same as that of the classical Rankine cycle in which the working fluid is water. However, due to the lower evaporation temperature of the working fluid, the external heat source in an ORC may be in a lower temperature range than the external heat source in a Rankine cycle working with water. 
     Today, devices for power generation according to an ORC are commercially available mainly in a range starting with 0.3 MW electric power output, but there is an increasing need for such devices with a smaller electric power output too. In particular for the range of 25 kW to 250 kW electric (corresponding to a thermal recuperation range of about 150 kW to 1.5 MW), there seem to be interesting applications for producing electricity with low temperature sources using an ORC. However, with a decreasing nominal power of the device used for power generation, the investment costs per kW installed strongly increase and the efficiency of power generation decreases. 
     If the external heat source is connected into the ORC by means of a heat carrier medium, which has to be cooled down in an evaporator working as counter-current heat exchanger, it is known to operate an ORC with more than one evaporator. Each evaporator then works at a different evaporation pressure, i.e. with a different evaporation temperature, in combination either with a separate expansion machine for each evaporator or with a single multi-stage expansion machine, in which the vapour produced in each additional evaporator, is injected into an intermediate stage of the multi-stage expansion machine. Due to the fact that the heat transfer is split between evaporators working at different evaporation temperatures, one can work with a more important temperature differential on the side of the heat carrier medium, i.e. transform more heat into power. 
     ORC systems with more than one evaporator are e.g. described in DE 10 2007 044 625 A1 . According to a first embodiment, the system comprises several separate ORCs, each of these ORCs comprising an evaporator, a turbine, a condenser and a condensate pump. With regard to the heat carrier fluid, the evaporators are basically connected in series. With each evaporator is associated a turbine comprising its own housing with a nozzle system and blade wheels. These turbines are regrouped in pairs, wherein the blade wheels of a turbine pair have a common shaft. The parallel shafts of two turbine pairs are interconnected by a gear system to drive an electrical generator. Such a multi-turbine solution is of course expensive and cumbersome. 
     According to a second embodiment described in DE 10 2007 044 625 A1, the system comprises two evaporators associated with a two-stage turbine. This two-stage turbine comprises a rotor carrying two axially spaced blade rings, wherein the first blade ring has a smaller diameter than the second blade ring. A first steam flow (i.e. high pressure steam produced by a high pressure evaporator) radially enters into the turbine housing through a high pressure inlet and flows through a first annular channel radially into a first annular nozzle ring, which deflects the flow in an axial direction into the first rotor blade ring, i.e. the blade ring with the smaller diameter. A second steam flow (low pressure steam produced by a low pressure evaporator) radially enters into the turbine housing through a low pressure inlet and flows through a second annular steam channel into a second nozzle ring, which deflects the flow in an axial direction into the second rotor blade ring, i.e. the blade ring with the bigger diameter. The two stages are designed so as to achieve the same end pressure at the outlet of the first and second blade ring, wherein the exhaust streams are only merged in an outlet diffuser of the turbine. It is obvious that such a turbine has a rather low efficiency, when compared e.g. to a typical induction type turbine, i.e. a multi-stage axial turbine in which low pressure steam is induced into the main vapour stream at an intermediate turbine stage and both streams are thereafter commonly expanded. However, for power generation with an ORC in the kW-range, known induction type turbines are by far too expensive. 
     GB 403,335 and U.S. Pat. No. 1,870,212 show a radial-outward-flow type multi-stage turbine, with an axial main vapour inlet port and an annular secondary vapour inlet port, which is arranged in the turbine so as to annularly induce, in an intermediary stage of the turbine, a secondary vapour stream into an already partially expanded radial main vapour stream. The main vapour inlet port and the annular secondary vapour inlet port have to be separated by complicated labyrinth packaging, which makes the turbine rather expensive. 
     DE 537,917 shows a rather complicated design of a radial-flow type turbine, in which the rotor comprises axially spaced sets of stator/rotor assemblies, which are separated by separation walls and connected either in parallel or in series. 
     An object of the present invention is consequently to provide an induction type turbine, which can be produced at relatively low costs, and which has nevertheless good efficiency, so as to be e.g. an interesting solution for power generation with an ORC below 1 MW electric. 
     SUMMARY OF INVENTION 
     The present invention provides a turbine that is a radial-outward-flow type multi-stage turbine, with an axial main vapour inlet port and an annular secondary vapour inlet port, which is arranged in the turbine so as to annularly induce, in an intermediary stage of the turbine, a secondary vapour stream into an already partially expanded radial main vapour stream. The annular secondary vapour inlet port comprises a ring-zone with through holes, which radially surrounds said axial main vapour inlet port in a first turbine housing part. The axial vapour inlet port comprises a first tubular vapour inlet connection, and the annular vapour inlet port comprises a second tubular vapour inlet connection surrounding the first tubular vapour inlet connection, so as to define with the latter an annular space, wherein the ring-zone with through holes is arranged in this annular space. 
     It will be appreciated that—due to the design of the turbine as a radial-outward-flow type multi-stage turbine—the annular secondary vapour inlet port can be accommodated into the turbine very easily and, basically, without major additional costs. The manufacturing costs for the induction type turbine are not much higher than for a turbine with a single vapour inlet. Indeed, in such a turbine comprising several concentric rings of stator blades, an annular secondary vapour inlet port can be easily accommodated radially between two successive rings of stator blades. The annular configuration of the secondary vapour inlet port warrants low pressure losses at the secondary vapour induction and relatively small perturbations of the radial flow of the main vapour stream. The fact that each turbine stage of such a radial turbine may be easily accommodated to an increased vapour throughput—by simply increasing the height of the stator and rotor blades—makes this type of turbine particularly suitable for vapour induction in an intermediary turbine stage. The fact that the vapour is expanded in successive turbine stages with increasing diameters makes the turbine even more suitable for vapour induction in an intermediary stage. It will further be appreciated that a turbine in accordance with the present invention can be connected with a minimum of pressure losses to a high pressure and a low pressure vapour source. 
     In a preferred embodiment, the turbine comprises a substantially plate-shaped first housing part supporting the rings of stator blades. In this embodiment, the annular secondary vapour inlet port is advantageously formed in the first housing part as a ring-zone with through holes arranged between two successive rings of stator blades. 
     The turbine further comprises a rotor, which includes for each turbine stage, a ring of rotor blades radially surrounding a ring of stator blades. In a preferred embodiment, the annular secondary vapour inlet port opens onto an outer annular rim of a rotor ring, in which the rotor blades of a turbine stage are incorporated. This outer annular rim advantageously has a radial width decreasing towards its periphery, so as to form an annular (preferably concave) surface, for annularly deviating the secondary vapour stream, which flows through the annular secondary vapour inlet port, into a ring of stator blades of the next turbine stage, wherein it is merged with the already partially expanded main vapour stream. This embodiment warrants—at very reasonable costs—particularly low pressure losses at the secondary vapour induction and small perturbations of the radial flow of the main vapour stream. 
     In this preferred embodiment, the annular (preferably concave) surface, which is formed on the outer annular rim of the rotor ring, advantageously cooperates with an annular (preferably convex) surface, which is formed on a stator ring, in which the stator blades of the next turbine stage are incorporated, so as to define a ring-shaped converging nozzle for injecting the secondary vapour stream, which flows through the annular secondary vapour inlet port, into the ring of stator blades of the next turbine stage. This embodiment even further reduces—at very reasonable costs—pressure losses at the secondary vapour induction and results in still smaller perturbations of the radial flow of the main vapour stream. 
     This preferred embodiment of the turbine may further comprise a set of stator rings, with different diameters, with the stator blades incorporated therein, wherein the stator rings are removably fixed (e.g. with screws) on the first turbine housing part. Similarly, the turbine may further comprise a set of rotor rings, with different diameters, with the rotor blades incorporated therein, wherein these rotor rings are removably fixed (e.g. with screws) on a rotor disk. This embodiment allows accommodating the turbine or one or more turbine stages to a different vapour throughput by simply exchanging the stator and rotor rings. The turbine may be easily up-sized or down-sized, and it may be easily fine-tuned to specific working parameters. Hence, an optimal turbine efficiency may nearly always be warranted. 
     This preferred embodiment of the turbine may further comprise a stator exhaust ring radially surrounding the stator ring with the biggest diameter and being removably fixed on the first turbine housing part, wherein the stator exhaust ring defines vapour exhaust openings for discharging the expanded vapour stream. It may also comprise a substantially plate-shaped second turbine housing part including a shaft outlet neck and being removably fixed on the stator exhaust ring. In this preferred embodiment, a turbine shaft is rotatably supported within the shaft outlet neck; and the aforementioned rotor disk is supported in a cantilever manner by the turbine shaft, between the first turbine housing part and the second turbine housing part. 
     In this preferred embodiment, the first turbine housing part advantageously supports an end-cap, which forms a vapour inlet deflection surface opposite the axial main vapour inlet port the vapour inlet deflection surface, which is designed as a revolution surface centred on the central axis of the turbine. The stator blades of the first turbine stage are advantageously incorporated into this end-cap. 
     In this preferred embodiment, the second turbine housing part is advantageously equipped with mounting means for mounting it in a sealed manner in an opening of a container, so that a shaft outlet neck of the second turbine housing part is arranged outside the container, and the vapour exhaust openings for discharging the expanded vapour stream are arranged inside the container. 
     This preferred embodiment of the turbine may further include rolling contact bearings in the shaft outlet neck for supporting and locating the turbine shaft therein, and a shaft sealing device arranged adjacent to the rolling contact bearings, so that the rolling contact bearings are sealed from the vapour in the turbine. Hence, the shaft bearings may be rather standard rolling contact bearings, which are easily accessible outside the container for monitoring and maintenance purposes. 
     A preferred embodiment of the turbine may further comprise a first vapour drum that is located in axial extension of the axial main vapour inlet port and directly connected to the latter without any intermediate piping, and a second vapour drum that is located in axial extension of the annular secondary vapour inlet port and directly connected to the latter without any intermediate piping, wherein the second vapour drum is preferably a compartment inside the first vapour drum, or the first vapour drum is, more preferably, a compartment inside the second vapour drum. The axial vapour inlet port advantageously comprises a first tubular vapour inlet connection, which is engaged in a sliding and sealed manner by the first vapour drum, and the annular vapour inlet port advantageously comprises a second tubular vapour inlet connection surrounding the first tubular vapour inlet connection, wherein this second tubular vapour inlet connection is engaged in a sliding and sealed manner by the second vapour drum. Such combined low and high pressure vapour drums, which are connected without any intermediate piping and, preferably, with sliding connections to the turbine vapour inlets, reduce pressure losses at the vapour inlet(s) of the turbine, allow to easily achieve a superheating of the low pressure vapour by the high pressure vapour, thereby increasing efficiency of the Rankine cycle, make the device more compact, facilitate its assembling and reduce its costs. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The afore-described and other features, aspects and advantages of the invention will be better understood with regard to the following description of an embodiment of the invention and upon reference to the attached drawings, wherein: 
         FIG. 1 : is a schematic vertical sectional view of a container containing a turbine in accordance with the present invention and an arrangement of several heat exchangers; 
         FIG. 2 : is a schematic sectional view of a multi-stage turbine, in which low pressure vapour is induced at a low pressure turbine stage, wherein the section plane contains the central axis of the turbine; 
         FIG. 3 : is an enlarged detail of  FIG. 2 ; 
         FIG. 4 : is a schematic sectional view of a turbine as shown in  FIG. 2 , the section plane being this time perpendicular to the central axis of the turbine; 
         FIG. 5 : is a schematic sectional view of the turbine as in  FIG. 2 , further schematically showing a first arrangement of a high pressure vapour drum and a low pressure vapour drum directly connected to the turbine; 
         FIG. 6 : is a schematic sectional view as in  FIG. 5 , showing a slightly modified embodiment; 
         FIG. 7 : is a schematic sectional view as in  FIG. 5 , showing a further possibility how to connect the high pressure vapour drum and the low pressure vapour drum to the turbine; and 
         FIG. 8 : is a schematic sectional view as in  FIG. 5 , showing an additional possibility how to connect the high pressure vapour drum and the low pressure vapour drum to the turbine. 
     
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION 
     It will be understood that the following description and the drawings to which it refers describe by way of example preferred embodiments of the claimed subject matter for illustration purposes. The description and drawings shall not further limit the scope, nature or spirit of the claimed subject matter. 
       FIG. 2  is a schematic cross-section through a turbine  16  in accordance with the present invention. It will first be noted that the turbine  16  is a multi-stage (here a three-stage) outward-flow radial type turbine, i.e. the vapour axially enters into the turbine  16  and then flows in a radial direction outward through the different stages of the turbine  16 , which are substantially concentric. The turbine is furthermore of the induction type, i.e. a secondary flow of low pressure vapour is induced at a low pressure stage into the turbine  16 . Finally, the turbine is of the impulse type, i.e. the vapour is mainly expanded as it passes through the stator of the turbine  16 . 
     As best seen in the cross-section of  FIG. 4 , each of the three turbine stages comprises a stator ring  56   1 ,  56   2 ,  56   3 , with increasing diameter and curved stator blades  58   1 ,  58   2 ,  58   3 , and a rotor ring  60   1 ,  60   2 ,  60   3 , with increasing diameter and curved rotor blades  62   1 ,  62   2 ,  62   3 . The inlet stator ring  56   1  and the first rotor ring  60   1  form the first stage of the turbine  16 . The second stator ring  56   2  and the second rotor ring  60   2  form the second stage of the turbine  16 . The third stator ring  56   3  and the third rotor ring  60   3  form the third stage of the turbine  16 . A fourth ring  56   4  surrounds the third or last stage of the turbine  16 , to form a stator exhaust ring  56   4 , with stator exhaust blades  58   4 . It will of course be understood that the turbine  16  may also be designed with 4 stages or more, by adding one or more pairs of stator and rotor rings. 
     Referring now to  FIG. 2  again, it will be noted that the rotor rings  60   1 ,  60   2 ,  60   3  are supported by a rotor disk  64 , which is fixed to a free end of a turbine shaft  66 . The turbine shaft  66  with the rotor disk  64  is rotatably supported in a cantilever fashion in a shaft outlet neck  72  by means of a bearing arrangement, preferably built up with rolling contact bearings. Reference number  68  points to a schematic representation of such a rolling contact bearing. Reference number  70  identifies a schematic representation of a sealing device, which seals the shaft  66  in the shaft outlet neck  72 , between the rotor disk  64  and the bearing arrangement. 
     Reference number  74  identifies the central axis of the turbine shaft  66 , which is also the central axis of all rotor rings  60   1 ,  60   2 ,  60   3  (and of all stator rings  56   1 ,  56   2 ,  56   3 ,  56   4 ), since all these rings are coaxial with the turbine shaft  66 . It will be noted that the rotor disk  64  is axially secured to the turbine shaft  66 , e.g. by means of a nut  75  or a screw (not shown), and that the torque is transmitted from the rotor disk  64  to the turbine shaft  66  by means of a form-fit or keyed assembly (not shown). The rotor rings  60   1 ,  60   2 ,  60   3  are fixed with screws  76  to the rotor disk  64 , so that they are easily exchangeable. 
     Still referring to  FIG. 2 , the stator rings  56   1 ,  56   2 ,  56   3  are fixed with screws  78  to a plate-shaped first turbine housing part  80 . This first turbine housing part  80  comprises a first and a second tubular vapour inlet connection  82 ,  84 , a first and a second ring-shaped flange  88 ,  90  and a perforated ring zone  92 . The first tubular vapour inlet connection  82  is centred on the central axis  74  of the turbine  16 . The second tubular vapour inlet connection  84  surrounds the first tubular vapour inlet connection  82 , so as to define with the latter an annular space  86 , wherein the perforated ring zone  92  is contained in this annular space  86 . The first ring-shaped flange  88  forms a shoulder around the first tubular vapour inlet connection  82 . The second ring-shaped flange  90  forms a shoulder around the second tubular vapour inlet connection  84 . The perforated ring zone  92  joins the first flange  88  and the second ring-shaped flange  90  and is provided with through-holes  94 . 
     It will be noted that instead of being integral with the first turbine housing part  80 , the first and/or second tubular vapour inlet connection  82 ,  84  could also be flanged to the first turbine housing part  80 . In this case, the first turbine housing part  80  mainly consists of the first ring-shaped flange  88 , the second ring-shaped flange  90  and the perforated ring zone  92 , which joins the first and the second ring-shaped flange  88 ,  90 . In this embodiment, the first ring-shaped flange  88  advantageously comprises a first connection means for flanging a removable first vapour inlet connection thereto, and the second ring-shaped flange  90  advantageously comprises a second connection means for flanging a removable second vapour inlet connection thereto (not shown in the drawings). 
     The first ring-shaped flange  88  supports the first and the second stator ring  56   1 ,  56   2 . The first stator ring  56   1  is advantageously part of an end-cap  96 , which forms a vapour inlet deflection surface  98  at the end of the first tubular vapour inlet connection  82 . This vapour inlet deflection surface  98  is a revolution surface centred on the central axis  74  of the turbine  16 , so as to annularly deflect the axial vapour stream in the first tubular vapour inlet connection  82  by 90° into the first stator ring  56   1 . 
     The second ring-shaped flange  90  supports the third stator ring  56   3 , as well as the exhaust stator ring  56   4 . By means of the exhaust stator ring  56   4 , the first turbine housing part  80  is fixed to a plate-shaped second turbine housing part  100 . The rotor disk  64  with the rotor rings  60   1 ,  60   2 ,  60   3  is hereby located axially between the first housing part  80  and the second housing part  100 . In the radial direction, the first rotor ring  60   1  is located between the first and the second stator ring  56   1 and  56   2 ; the second rotor ring  60   2  is located between the second and the third stator ring  56   2  and  56   3 ; and the third rotor ring  60   3  is located between the third stator ring  56   3  and the exhaust stator ring  56   4 . It will be appreciated that—with this sandwich design—the height of the stator blades  58   1 ,  58   2 ,  58   3  and rotor blades  62   1 ,  62   2 ,  62   3  can be modified, by simply exchanging the removable stator rings  56  and rotor rings  60 . Consequently, with one size for the first and second turbine housing part  80  and  100 , the rotor disk  64  and the turbine shaft  66 , one may already cover a large range of pressures and flow rates. Thus, it will be e.g. be possible to cover the electric power range of 25 kW to 100 kW with one unique size for the first and second turbine housing part  80  and  100 , the rotor disk  64  and the turbine shaft  66 . In most cases it will even not be necessary to change the form of the rotor and stator blades  58 ,  62 . A broad electric power range may be covered by simply changing the height of the rotor and stator blades  58 ,  62 , all other geometric characteristics of the rotor and stator rings  56 ,  60  and blades  58 ,  62  remaining unchanged. Furthermore, if the available heat energy increases or decreases during lifetime of the turbine, the latter may be easily reconfigured for the new operating conditions by simply exchanging its rotor and stator rings  56 ,  60 . 
     As is best seen in  FIG. 3 , each of the three stator rings  56   1 ,  56   2 ,  56   3  includes at its base an annular shoulder  102   1 ,  102   2 ,  102   3 , which forms a labyrinth joint  106  with an opposite grooved surface located on an annular outer annular rim  104   1 ,  104   2 ,  104   3  of the corresponding rotor ring  60   1 ,  60   2 ,  60   3 . Similarly, each of the first two rotor rings  60   1 ,  60   2  includes at its base an annular shoulder  108   1 ,  108   2 , which forms a labyrinth joint  112  with an opposite grooved surface located on an annular outer annular rim  110   2 ,  110   3  of the corresponding stator ring  56   2 ,  56   3 . Thus, vapour tightness in the radial direction between the rotating and stationary parts is solely achieved by easily machinable surfaces on the removal stator rings  56   1 ,  56   2 ,  56   3  and rotor rings  60   1 ,  60   2 , and necessitates neither complicated machining on the turbine housing parts  80 ,  100  or the rotor disk  64 , nor separate sealing elements. Furthermore, if the removable rotor and stator rings  56 ,  60  are replaced, all sealing surfaces in the turbine are replaced too. Alternatively, the removable stator rings  56   1 ,  56   2 ,  56   3  and rotor rings  60   1 ,  60   2 , may be designed without the aforementioned annular shoulder, wherein the outer annular rims  104   1 ,  104   2 ,  104   3  of the rotor rings  60   1 ,  60   2 ,  60   3  and the outer annular rims  110   2 ,  110   3  of the stator rings  56   2 ,  56   3  cooperate directly with corresponding annular surfaces on the housing part  80  and the rotor disk  64  to form labyrinth joints. 
     It will further be noted that the annular shoulder  102   2  of the second stator ring  56   2  is smaller than the other two annular shoulders  102   1 ,  102   3 , thereby leaving uncovered the through-holes  94  in the perforated ring zone  92  of the first turbine housing part  80 . The width of the annular outer annular rim  104   2  of the second rotor ring  60   2 , which is located just behind the perforated ring zone  92 , decreases towards its periphery, so as to define with the opposite surface of the third stator ring  56   3  a ring-shaped converging nozzle  114 , which is delimited, on one side, by an annular concave surface  116  defined by the second rotor ring  60   2  and, on the other side, by an annular convex surface  118  defined by the third stator ring  56   3 . This ring-shaped nozzle  114  deflects the low pressure vapour stream, which flows from the annular space  86  in an axial direction through the through-holes  94 , by an angle of 90° into the third stator ring  56   3 . In this third stator ring  56   3 , this low pressure vapour stream is induced into the main vapour stream that has already been expanded in the first and second stage of the turbine  16 , so that both vapour streams have substantially the same pressure when they merge in the third stator ring  56   3 . 
     Referring simultaneously to  FIG. 2  and  FIG. 3 , it will be noted that the expansion of the vapour in the second stator ring  56   2  and the third stator ring  56   3  is mainly achieved by increasing the height of the stator blades  58  in the radial direction (i.e. the height of these blades at the outlet is considerably higher than their height at the inlet of the stator ring). Thus, the expansion of the vapour in these stator rings  56   2  and  56   3  is mainly determined by the increasing height of their blades. Consequently, for adapting the turbine to a different vapour throughput or a different inlet pressure in the turbine  16 , it will not be necessary to entirely change the geometry of the rotor or stator blades  58 ,  62 . It will most often simply be sufficient to change the height of the rotor and stator blades  58 ,  62 , all other geometric characteristics of the rotor and stator rings  56 ,  60  and blades  58 ,  62  remaining basically unchanged. 
     It will be appreciated that the turbine as described hereinbefore may achieve an isentropic efficiency as high as 90%. Its rotation speed will preferably be limited to 18,000 rpm, so as to be capable of working with rolling contact bearings and common shaft sealing devices. 
       FIG. 5  schematically shows a first arrangement of a high pressure vapour drum  46  and a low pressure vapour drum  48 , both directly located under the turbine  16  and directly connected to latter without any intermediate piping. In the embodiment of  FIG. 5 , the high pressure vapour drum  46  is a cylindrical vessel directly flanged to the first turbine housing part  80 . The low pressure vapour drum  48  forms an annular compartment within the high pressure vapour drum  46 . This annular compartment is outwardly delimited by a cylindrical external wall  120  of the high pressure vapour drum  46  and inwardly delimited by a cylindrical internal wall  122 . This cylindrical internal wall  122  engages the first tubular vapour inlet connection  82  of the turbine  16  in a sealed fit, wherein this sealed fit shall however be designed (e.g. with O-rings) to allow relative axial movement of the cylindrical internal wall  122  and the first tubular vapour inlet connection  82 . The high pressure vapour flows through the axial passage delimited by the cylindrical internal wall  122  into the first tubular vapour inlet connection  82  of the turbine. The low pressure vapour flows directly from the annular low pressure vapour drum  48  into the annular space  86  delimited between the first tubular vapour inlet connection  82  and the second tubular vapour inlet connection  84  of the turbine. Reference number  124  points to a high pressure vapour inlet pipe connected laterally to the high pressure vapour drum  46 , whereas reference number  126  points to a low pressure vapour inlet pipe connected laterally to the low pressure vapour drum  48 . 
     The arrangement of  FIG. 6  distinguishes over the arrangement of  FIG. 5  mainly in that the low pressure vapour inlet pipe  126 ′ traverses the high pressure vapour drum  46  to leave the latter through its bottom wall. This design necessitates that the low pressure vapour inlet pipe  126  and the high pressure vapour drum  46  may freely expand relative to one another. This can e.g. be achieved by connecting the low pressure vapour inlet pipe  126  by means of a bellow expansion joint (not shown) to the closed end of the high pressure vapour drum  46 . 
       FIG. 7  shows a further arrangement of the high pressure vapour drum  46  and the low pressure vapour drum  48  connected to the turbine  16 . The low pressure vapour drum  48  is a cylindrical vessel flanged to the first turbine housing part  80 . The high pressure vapour drum  46  forms a cylindrical compartment within the low pressure vapour drum  48 , separated from the outer wall of the latter by an annular space  130 . It is vertically supported by a support flange  132 , which is welded into the low pressure vapour drum  48 . Through-openings  134  in the support flange  132  allow the intermediate pressure vapour to pass from an inlet compartment  136  of the low pressure vapour drum  48  into the annular space  130 . The high pressure vapour drum  46  engages the first tubular vapour inlet connection  82  of the turbine  16  in a sealed way, wherein this sealed fit shall however be designed (e.g. with O-rings) to allow relative axial movement of the high pressure vapour drum  46  and the first tubular vapour inlet connection  82 . Similarly as for the pipe  126 ′ in the embodiment of  FIG. 7 , the passage of the pipe  124  through the bottom wall of the low pressure vapour drum  48  is designed for allowing a relative axial expansion of both components. 
     It will be noted that in  FIGS. 5, 6 and 7 , the outer vessel is flanged to the first turbine housing part  80  of the turbine  16 , and must consequently be able to axially expand away from the turbine  16 . In  FIG. 8 , the outer vessel  140  is no longer flanged to the first turbine housing part  80  of the turbine  16 . It simply engages the second tubular vapour inlet connection  84  of the turbine  16  in a sealed way, wherein this sealed fit is designed (e.g. with O-rings) to allow a relative axial movement of the outer vessel  140  and the second tubular vapour inlet connection  84 . In this embodiment, the outer vessel  140  (which may be the high pressure vapour drum  46  as in  FIG. 5 or 6 , or the low pressure vapour drum  48  as in  FIG. 7 ) can be vertically supported by a separate vertical support means  142 . Thus, the outer vessel  140  may e.g. be directly supported on the first or second evaporator  12 ,  14 , when the latter are axially arranged under the outer vessel  140 . It will consequently be appreciated that in the embodiment of  FIG. 7 , the turbine  16  must not support the whole weight of the two vapour drums  46 ,  48 . 
     It will be appreciated that in all three arrangements, the low pressure vapour is slightly superheated by contact with one or more walls of the high pressure vapour drum  46 , which may be advantageous for the efficiency of the low pressure cycle. This superheating-effect is more important for the embodiment of  FIG. 7  and may be further amplified by providing the outer wall of the inner cylinder  46  in  FIG. 7  with fins. 
       FIG. 1  shows a compact device for electric power generation according to an improved ORC, more particularly, to an ORC working with two evaporators  12 ,  14 , two regenerators  20 ,  22  and an induction turbine  16  according to the present invention. The container  10  is a vertical vapour tight cylinder supported on support feet  150 . The turbine  16  is located inside the vertical cylinder  10 , near the top end of the latter. The central axis  74  of the turbine is aligned with the central axis of the container  10 . Referring back to  FIG. 2 , it will be noted that the second turbine housing part  100  is fixed with in a sealed manner to a head-plate  152 , which is a part of the upper container wall. The shaft outlet neck axially protrudes out of an opening  153  of the head-plate  152 . Alternatively, the second turbine housing part  100  may include an annular flange (not shown) with which it is fixed in a sealed manner onto a flange surrounding an axial opening (not shown) in the head of the container  10 . In this case the entire second turbine housing part  100  is located outside the container  10 . A generator  154  is arranged on the top of the vertical cylinder  10  and is coupled to the vertical shaft of the turbine  16 . It will be appreciated that with this arrangement, the bearing arrangement  68  of the turbine shaft  66  is located completely outside the container  10 , which greatly facilitates the design of its lubrication system, but also its maintenance. 
     The high pressure vapour drum  46  and the low pressure vapour drum  48  are arranged axially directly under the turbine  16 . Both vapour drums  46 ,  48  are advantageously connected to the first and second tubular vapour inlet connection  82 ,  84  of the turbine  16  as described e.g. with reference to  FIG. 5 or 6  and  FIG. 8 . The first evaporator  12  and the second evaporator  14  are arranged axially directly under the two vapour drums  46 ,  48 , which can be vertically supported by the two evaporators  12 ,  14 , as described with reference to  FIG. 1 . These two evaporators  12 ,  14  are preferably enclosed in a separate cylindrical compartment  156 . The first and second regenerator  20 ,  22  are arranged annularly around the two vapour drums  46 ,  48 , wherein the second regenerator  22  is arranged directly under the first regenerator  20 . The condenser  18  is arranged annularly around the two evaporators  12 ,  14 . The bottom part of the vertical cylinder  10  forms a condensate collector  158 . 
     The turbine  16  radially discharges the expanded vapour through the stator exhaust ring  564  directly into the upper part of the vertical cylinder  10 . An annular deflector (not shown) may be used to deflect the radially discharged vapour axially downwards. This annular deflector may be incorporated into the turbine  16  or be installed as a separate element into the container  10 . The expanded vapour then passes downwards through the first and second regenerator  20 ,  22 , to be finally condensed in the condenser  18 . The condensate is collected in the condensate collector  158  at the bottom of the vertical cylinder  10 . 
     
       
         
           
               
             
               
                   
               
               
                 Reference signs list 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 10 
                 container 
                  82 
                 first tubular vapour inlet 
               
               
                 12 
                 first evaporator 
                   
                 connection 
               
               
                 14 
                 second evaporator 
                  84 
                 second tubular vapour inlet 
               
               
                 16 
                 turbine 
                   
                 connection 
               
               
                 18 
                 condenser 
                  86 
                 annular space (between  
               
               
                 20 
                 first regenerator 
                   
                 82 and 84) 
               
               
                 22 
                 second regenerator 
                  88 
                 first ring-shaped flange  
               
               
                 26 
                 electrical generator 
                   
                 (on 82) 
               
               
                     56 1 , 
                 first stator ring, 
                  90 
                 second ring-shaped flange  
               
               
                     56 2 , 
                 second stator ring, 
                   
                 (on 84) 
               
               
                     56 3   
                 third stator ring 
                  92 
                 perforated ring zone 
               
               
                     56 4   
                 stator exhaust ring (58) 
                  94 
                 through-holes in 92 
               
               
                     58 1 , 
                 curved stator blades (58)  
                  96 
                 end-cap 
               
               
                   
                 of 56 1   
                  98 
                 vapour inlet deflection  
               
               
                     58 2 , 
                 curved stator blades (58)  
                   
                 surface 
               
               
                   
                 of 56 2   
                 100 
                 second turbine housing  
               
               
                     58 3   
                 curved stator blades (58)  
                   
                 part (100) 
               
               
                   
                 of 56 3   
                     102 1 , 
                 annular shoulder on 56 1 ,  
               
               
                     58 4   
                 stator exhaust blades 
                   
                 56 2 , 
               
               
                     60 1 , 
                 first rotor ring, 
                     102 2 , 
                 56 3   
               
               
                     60 2 , 
                 second rotor ring, 
                     102 3   
                   
               
               
                     60 3   
                 third rotor ring 
                     104 1 , 
                 annular outer annular rim  
               
               
                     62 1 , 
                 curved rotor blades of 60 1   
                   
                 on 60 1 , 
               
               
                     62 2 , 
                 curved rotor blades of 60 2   
                     104 2 ,  
                 60 2 , 60 3   
               
               
                     62 3   
                 curved rotor blades of 60 3   
                     104 3   
                   
               
               
                 64 
                 rotor disk 
                 106 
                 labyrinth joint 
               
               
                 66 
                 turbine shaft 
                     108 1 , 
                 annular shoulder on 60 1 ,  
               
               
                 68 
                 bearing 
                   
                 60 2   
               
               
                 70 
                 sealing device 
                     108 2   
                   
               
               
                 72 
                 shaft outlet neck 
                     110 2 , 
                 annular outer annular rim  
               
               
                 74 
                 central axis of 16 
                   
                 on 56 2 , 
               
               
                 75 
                 nut 
                     110 3   
                 56 3   
               
               
                 76 
                 screws for rotor rings 
                 112 
                 labyrinth joint 
               
               
                 78 
                 screws for stator rings (56) 
                 114 
                 ring-shaped nozzle 
               
               
                 80 
                 first turbine housing part  
                 116 
                 annular concave surface  
               
               
                   
                 (80) 
                   
                 defined by 60 2   
               
               
                 120  
                 cylindrical external wall 
                 118 
                 annular convex surface  
               
               
                 122  
                 cylindrical internal wall 
                   
                 defined by 56 3   
               
               
                 124  
                 high pressure vapour inlet  
                 140 
                 outer vessel 
               
               
                   
                 pipe 
                 142 
                 vertical support means 
               
               
                 126  
                 low pressure vapour inlet  
                 150 
                 support feet 
               
               
                   
                 pipe 
                 154 
                 generator 
               
               
                 130  
                 annular space 
                 156 
                 separate cylindrical 
               
               
                 132  
                 support flange 
                   
                 compartment 
               
               
                 134  
                 through openings in 132 
                 158 
                 condensate collector 
               
               
                 136  
                 inlet compartment