Patent Publication Number: US-2021175778-A1

Title: Compact halbach electrical generator for integration in a solid body

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention is the US national stage under 35 U.S.C. § 371 of International Application No. PCT/EP2018/084601, which was filed on Dec. 12, 2018, and which claims the priority of application LU 100556 filed on Dec. 13 2017, the content of which (text, drawings and claims) are incorporated here by reference in its entirety. 
    
    
     FIELD 
     The invention is directed to the field of electrical generators and also the field of valves and conduits for controlling a flow of gas on a gas cylinder or a flow of liquid in a hydraulic turbine. 
     BACKGROUND 
     Prior art patent document published DE 199 54 964 A1 discloses a hydraulic turbine generator. The generator is of a compact construction suitable to be mounted on a conduit for converting a flow of fluid in the conduit into electrical power. The generator comprises a turbine wheel and a rotor mounted on a shaft. The rotor is surrounded by a cylindrical wall delimiting a cavity for the rotor and the fluid. The rotor comprises permanent magnets and a stator is arranged around the wall. The stator comprises a first element made of ferromagnetic material with a base portion and a series of arms extending axially from the base portion along the outer surface of the wall, a second similar element with also a base portion and series of arms offset relative to those of the first element, and a coil arranged between the base portions of the first and second elements. That construction is interesting in that a proper fluid tightness is achieved because the fluid driving the turbine wheel is not in contact with the stator, meaning that no rotary sealing is necessary around the shaft, between the turbine wheel and the rotor. The wall is cap-shaped and held in a fluid tight contact with the body of the generator by means of a ticker sleeve surrounding the arms of the stator. For applications with high pressure this can be critical and lead to leakages. 
     Prior art patent document published JPH 02197243 A discloses also a compact generator of a similar construction to the preceding document. The rotor shows permanent magnets which are however oriented S-N-S- . . . along the rotor periphery. Also, there is no wall separating the rotor and the stator because there is no working fluid, except air, circulating and in contact with the rotor. 
     Prior art patent document published EP 0 425 260 A1 discloses also a compact generator of a similar construction to the two preceding documents. It concerns a built-in generator arranged within a hub of a cycle wheel, including a hub member rotatably fitted on an axle which is to be fixed to a frame of the cycle, a stationary hollow cylinder (the stator composed of two four strip-shaped poles armatures) fixed to the axle in the hub member, a generating coil unit (held between the two four strip-shaped poles armatures of the stator) provided in the stationary hollow cylinder and fixed thereto, and a rotor formed integrally with a magnet rotatably provided on the axle. 
     Prior art patent document published DE 195 05 698 A1 discloses a hydraulic turbine generator similar to the one of the above cited document DE 199 54 964 A1. In that generator, the fluid flows axially relative to the rotation axis of the rotor. The fluid, for instance water, fills the cavity where the rotor is located, similarly to the above cited document. 
     Prior art patent document published DE 20 2005 019 163 U1 discloses a hydraulic turbine generator similar to those of the above cited documents. The turbine wheel is however mounted directly on the magnetic rotor. Also the rotor is particularly built in that it comprises an inner ring with permanent magnets and an outer ring surrounding the inner ring and being non-magnetic so as to promote the magnetic field towards the interior of the rotor. Also, the stator and the coil(s) are located inside the rotor. A wall separates a cavity housing the turbine wheel, the rotor and the fluid from the stator inside the rotor. 
     The above discussed turbine generators are intended to be compact. Each of them forms however a specific unit that can be mounted on a conduit (DE 199 54 964 A1), or connected to conduits (DE 195 05 698 A1 and DE 20 2005 019 163 U1). In other words, these generator are not suitable for being integrated in a device, e.g. a device forming a conduit or passage for the fluid. In addition, these generators, also supposed to be compact, remain bulky for such an integration. The specific electrical output power, i.e. power per unit volume of the generator remains low and subject to improvement. Also, the above generators are not conceived for fluids under high pressure. 
     SUMMARY 
     The invention has for technical problem to provide an electric generator that overcomes at least one of the drawbacks of the above cited prior art. More specifically, the invention has for technical problem to provide an electric generator that can be particularly compact while providing a satisfactory output power, in particular for being integrated into an existing device. 
     The invention is directed to an electric generator comprising: a rotor with permanent magnets, configured for rotating about a rotation axis; a magnetic yoke with at least two arms extending axially inside or outside of the rotor so as to be adjacent to the radial inner or outer side, respectively, of the rotor; wherein the permanent magnets are arranged according to an Halbach array so as to maximize the magnetic field on the radial side of the rotor adjacent to the arms of the yoke. 
     According to an exemplary embodiment, the permanent magnets are arranged so as to successively rotate by 90° along the circumference of the rotor. 
     According to an exemplary embodiment, the generator comprises at least one coil arranged at a distal portion of the at least one yoke where the arms of the yoke join each other, so as to be in a variable magnetic field produced by a rotation of the rotor relative to the at least one yoke. 
     According to an exemplary embodiment, each of the at least one yoke further comprises at least one bridge interconnecting diametrically opposed arms of the yoke. 
     According to an exemplary embodiment, the at least one yoke comprises a first yoke and a second yoke, wherein the arms of the first yoke are angularly offset relative to the arms of the second yoke. 
     According to an exemplary embodiment, the at least one coil is sandwiched between the bridges of the first and second yokes. 
     According to an exemplary embodiment, the generator comprises a wall forming a cavity housing the rotor, the arms of the at least one yoke being out of the cavity. 
     According to an exemplary embodiment, the wall forming the cavity is made of solid material, the arms of the at least one yoke extending inside the material. 
     According to an exemplary embodiment, the material of the wall is non-ferromagnetic, such as aluminium, austenitic stainless steel, ceramic or brass with permeability equal or very close to 1. 
     According to an exemplary embodiment, the generator further comprises a turbine wheel mechanically coupled to the rotor. 
     According to an exemplary embodiment, the generator further comprises a shaft supporting the rotor and the turbine wheel, and bearings at each end of the shaft. 
     According to an exemplary embodiment, the turbine wheel is located axially on the rotor and surrounds the rotor. 
     According to an exemplary embodiment, the turbine wheel is an axial turbine wheel comprising blades extending radially and configured for being converting an annular axial flow through the blades into a rotational movement of the turbine wheel and the rotor. 
     According to an exemplary embodiment, the cavity houses the turbine wheel. 
     According to an exemplary embodiment, at least one, in various instances each, of the arms of the at least one magnetic yoke comprises at least one, in various instances several slits extending lengthwise. 
     Advantageously, the arms of the at least one magnetic yoke have the same width. 
     The invention is also directed to a valve for gas cylinder, comprising: a body with an inlet, an outlet and a passage interconnecting the inlet and outlet; a flow control device mounted on the body and controlling the flow of gas in the passage; wherein the valve further comprises: an electric generator with a turbine wheel located in the passage, configured for outputting electric power when the gas flow in the passage rotates the turbine wheel. 
     According to an exemplary embodiment, the electric generator is according to the invention. 
     According to an exemplary embodiment, the generator comprises a wall forming a cavity housing the rotor and in various instances the turbine wheel, the arms of the yoke being out of the cavity, the wall being formed by the material of the body. 
     The invention is also directed to a conduit with a wall delimiting a passage for a fluid and with an electric generator with a turbine wheel located in the passage so as to be driven when the fluid flows, wherein the generator is according to the invention. 
     The invention is also directed to a use of an electric generator with a turbine wheel in a conduit for producing electricity while the fluid flows in the conduit, wherein the generator is according to the invention. 
     The invention is particularly interesting in that it provides a compact electric generator with an optimised specific output power. The use of a Halbach array in combination with axial arms of statoric magnetic yokes is particularly interesting in that the Halbach array produces a higher magnetic field that can then magnetise in a satisfactory manner the yoke(s) despite the presence of a possible wall there between. In particular, the wall can be made of solid material of the body of the generator, potentially forming a barrier for the development of a magnetic field beyond that wall. In addition, the use of a Halbach array maximises the magnetic field on one radial side of the rotor, the magnetic field on the opposite radial side being very low and thereby cause little electromagnetic disturbances. The magnetic field on the “strong” side of the rotor is absorbed by the yoke and the coil, so that it also cause little electromagnetic disturbances. 
     The electric generator of the invention is also particularly interesting for integration in a valve or any other kind of device that controls the flow of gas under high pressure, e.g. higher than 20 MPa or even 50 MPa. For such applications, the wall delimiting the cavity of the fluid needs to be massive and is usually made of non-ferromagnetic material such as brass, aluminium or austenitic stainless steel. The construction of the generator according to the invention is particularly adapted for such configuration for the arms of the yokes can be inserted into holes formed, e.g. by drilling or any kind of machining, in the solid material of the body, adjacent to the wall delimiting the cavity. 
    
    
     
       DRAWINGS 
         FIG. 1  is a schematic sectional view of an electric generator according to an exemplary first embodiment of the invention. 
         FIG. 2  is a schematic sectional view of an electric generator according to an exemplary second embodiment of the invention. 
         FIG. 3  illustrates in a schematic way the stator and rotors of both exemplary embodiments of the invention. 
         FIG. 4  illustrates an alternative stator for both exemplary embodiments of the invention. 
         FIG. 5  exemplarily illustrates the magnetic field of a linear array of permanent magnets with a single magnetisation orientation, in accordance with various embodiments of the present invention. 
         FIG. 6  exemplarily illustrates the magnetic field of a linear array of permanent magnets with an alternating array of magnetisation orientations, in accordance with various embodiments of the present invention. 
         FIG. 7  exemplarily illustrates the magnetic field of a linear array of permanent magnets with a Halbach array of magnetisation orientations, in accordance with various embodiments of the present invention. 
         FIG. 8  exemplarily illustrates the magnetic field distribution in a ring-shaped rotor with a classic array of 16 permanent magnets, in accordance with various embodiments of the present invention. 
         FIG. 9  exemplarily illustrates the magnetic field distribution in a ring-shaped rotor with a Halbach array of 16 permanent magnets where the magnetic field maximized on the outer side, in accordance with various embodiments of the present invention. 
         FIG. 10  exemplarily illustrates the magnetic field distribution in a ring-shaped rotor with a Halbach array of 16 permanent magnets where the magnetic field maximized on the inner side, in accordance with various embodiments of the present invention. 
         FIG. 11  exemplarily illustrates the modulus of the magnetic induction along diametrical cross-sections in the rotor of  FIGS. 8 and 9 , in accordance with various embodiments of the present invention. 
         FIG. 12  exemplarily illustrates the modulus of the magnetic field along diametrical cross-sections in the rotor of  FIGS. 8 and 10 , in accordance with various embodiments of the present invention. 
         FIG. 13  exemplarily illustrates the normal component of the magnetic field along a circular contour around the rotors of  FIGS. 8 and 9 , in accordance with various embodiments of the present invention. 
         FIG. 14  exemplarily illustrates the normal component of the magnetic field along a circular contour around the rotors of  FIGS. 8 and 10 , in accordance with various embodiments of the present invention. 
         FIG. 15  illustrates an exemplary first embodiment of a valve for gas cylinder, comprising an electric generator according the first exemplary embodiment of the invention. 
         FIG. 16  illustrates an exemplary second embodiment of a valve for gas cylinder, comprising an electric generator according the first exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic cross-section of an electric generator according to an exemplary first embodiment of the invention. 
     The electric generator  2  illustrated in  FIG. 1  is for instance a turbine electric generator, being understood that another power source than a flow of a fluid could drive the generator. The generator  2  comprises a body  4  that forms a passage  6  for a fluid, with an inlet  8  and an outlet  10 . The generator  2  comprises also a rotor  12  supported by a shaft  14 , and a turbine wheel  16  located in the passage  10  and mechanically coupled with the rotor  12 . For instance, the turbine wheel  16  supported by the shaft  14  and is therefore directly coupled to the rotor  12 . The shaft  14  supported by bearings  18  at both ends of the shaft, the bearings being attached to the body  4  of the generator  2 . Flow guiding surfaces  20  can be provided in the passage  10  for optimizing the cooperation of the flow with the turbine wheel  16 . 
     The rotor  12  comprises an array of permanent magnets (not represented) that produce a permanent magnetic field at the periphery of the rotor, for instance in the cavity  22  housing the rotor and also outside the wall  24  delimiting the cavity, i.e. in the material of the body  4 . The permanent magnets are advantageously arranged according to a Halbach array that maximizes the magnetic field on one radial side of the rotor, for instance on the outer side. The Halbach array will be detailed below in connection with  FIGS. 5 to 7 . 
     The generator  2  further comprises a stator  26  that is for instance composed essentially of two yokes  28  and  30  made of ferromagnetic material and comprising, each, at least a pair of, advantageously four, arms  28 . 1  and  30 . 1  extending axially along the wall  24  delimiting the cavity  22  and a bridge  28 . 2  and  30 . 2  interconnecting the arms, respectively. In  FIG. 1 , the yokes are represented as if their respective arms  28 . 1  and  30 . 1  were angularly aligned whereas in reality the yokes are angularly offset as is apparent in  FIG. 3 . The stator  26  comprises also a coil  32 , or at least one coil, that is located between the bridges  28 . 2  and  30 . 2  of the yokes  28  and  30 . More specifically, the stator  26  can also comprise a magnetic coupler  29  that magnetically couples the yokes  28  and  30  by interconnecting the bridges  28 . 2  and  30 . 2 . The coupler  29  advantageously traverses the coil  32 . 
     The functioning of the generator is the following. When the fluid flows through the passage  6 , from the inlet  8  towards the outlet  10 , the flow drives the turbine wheel  16  in rotation and thereby rotates the rotor  12 . The later produces a magnetic field with orientations that alternate along the periphery of the rotor. This magnetic field is fixed relative to the rotor  12 . The rotation of the rotor  12  causes a variation of the magnetic field produced in the arms  28 . 1  and  30 . 1  of the yokes  28  and  30 . This variably magnetic field propagates along the arms to the bridges  28 . 2  and  30 . 2  and to the coupler  29 , and induces in the coil  32  an electromotive force that produces an electrical power output. 
       FIG. 2  is a schematic cross-section of an electric generator according to a second exemplary embodiment of the invention. The reference numbers of the first exemplary embodiment are used here for designating the same or corresponding elements, these numbers are however incremented by 100. Reference is made to the description of these elements in relation with the first exemplary embodiment. 
     The electric generator  102  of  FIG. 2  is similar to the one of  FIG. 1 . It differs however essentially with regard to the following two aspects. 
     The first one is that the stator  126  is located inside the rotor  112 . The rotor  112  is hollow and forms an open cavity that surrounds a cylindrical portion  104 . 1  of the body  104 . That portion  104 . 1  forms a wall  124  delimiting a cavity  122  for the rotor  112  and the fluid. The stator  126  comprises arms  128 . 1  and  130 . 1  of yokes  128  and  130  that extend inside the volume delimited by the wall  124 , for instance inside the material of the portion  104 . 1  of the body  104 . The rotor  112  comprises an array of permanent magnets that is arranged so that the magnetic field produced by the magnets is present on the inner side of the rotor  112 . The permanent magnets are advantageously arranged according to a Halbach array that maximizes the magnetic field on one radial side of the rotor, for instance on the inner side. The Halbach array will be detailed below in connection with s  FIGS. 5 to 7 . 
     The other aspect that differentiates the second exemplary embodiment is that the turbine wheel  116  is mounted directly on the rotor  112 . For instance, the turbine wheel  116  is located around the rotor  112 . A shaft as such might not necessary anymore. For instance, the combined rotor  112  and turbine wheel  116  comprise a radial wall or bridge that interconnects both rotor and turbine to the bearings  118  attached to the body  104 . 
     The functioning of the generator is similar to the functioning of the generator of the first exemplary embodiment. When the fluid flows through the passage  106  from the inlet  108  to the outlet  110 , the fluid drive in rotation the turbine wheel  116  and therefore also the rotor  112 . The later produces a magnetic field on its inner side and therefore in the arms  128 . 1  and  130 . 1  of the yokes  128  and  130 . The rotation of the rotor  112  causes the magnetic field produced in the arms to vary and thereby to produce an electromotive force in the coil  132 . 
     The construction of the generator according to the second exemplary embodiment is advantageous in that that generator is particularly compact in height. 
     In both embodiments, the rotor advantageously is in contact with the fluid driving the turbine wheel, meaning that no rotary sealing is necessary around the shaft. The material of the body is advantageously non ferromagnetic, i.e. shows a relative magnetic permeability that is lower than 10, in various instances lower than 5, for example lower than 2, like for example stainless steel, more particularly austenitic stainless steel, aluminium, brass or copper, ceramic or thermosetting plastic or thermoplastic. The material of the yoke shows a high relative permeability, e.g. greater than 100, in various instances greater than 1000, like mu-metal, permalloy, invar, iron, ferritic stainless steel or ferrite. The fact that the material of the body around the arms of the yoke, more particularly between the arms of the yokes and the rotor, is non-ferromagnetic promotes the concentration in the arms of the magnetic field produced by the rotor. 
     In addition, still for both embodiments, the use of the solid material of the body for forming the wall delimiting the cavity housing the rotor is interesting for applications with gas under high pressure, e.g. greater than 20 MPa, in various instances greater than 50 MPa. Indeed, in the presence of such pressures the gas, the wall delimiting the cavity housing the fluid need to be particularly rigid and stable to avoid deformation and leakage. The arms of the yokes can be inserted in holes drilled in the body, at the proximity of the wall. 
       FIG. 3  illustrates in a schematic way the stator and rotors of both first and second exemplary embodiments of the invention. We can observe that the stator  26 / 126  comprises for instance two yokes  28 / 128  and  30 / 130 , each yoke comprising four arms that are angularly offset relative to the arms of the other yoke. The coil  32 / 132  is located between the bridges of the yokes  28 / 128  and  30 / 130 . According to the first exemplary embodiment ( FIG. 1 ), the rotor  12  is located inside the volume delimited by the arms of the yoke. According to the second exemplary embodiment ( FIG. 2 ), the rotor  112  is located around the arms of the yokes. In the first exemplary embodiment, the rotor  12  exhibits a magnetic field predominantly on its outer side so as to magnetize the stator disposed around the rotor, whereas in the second exemplary embodiment, the rotor  112  exhibits a magnetic field predominantly on its inner side so as to magnetize the stator disposed inside the rotor. 
       FIG. 4  illustrates an alternative arrangement of the stator  26 / 126  where the arms of the yokes  28 / 128  and  30 / 130  of the stator  26 / 126  shows each a parallel slit  28 . 3 / 128 . 3  and  30 . 3 / 130 . 3  extending lengthwise and in various instances also along the radial portion of the arms. Such slits extend radially through the whole thickness of the arms. They are useful for reducing the generation of eddy currents and the corresponding back electromotive forces in the arms. The slits advantageously extend at least in vis-à-vis of the rotor  12 / 112 . This configuration allows to provide arms that extend along a larger sector, thereby increasing the magnetic inductance in the arms and the power output of the generator. 
       FIGS. 5 to 13  illustrate the effects of a Halbach array for the permanent magnets on the rotor of the electric generator of the present invention. 
       FIGS. 5 to 7  illustrate in a comparative manner the production of magnetic field with a single pole linear array of permanent magnets, a multipole linear array of permanent magnets with alternating polarity and a multipole linear array of permanent magnets with a Halbach array. 
       FIG. 5  illustrates the lines of the magnetic field produced by a permanent magnet with a single pole orientation, for instance a linear juxtaposition of permanent magnets where the magnetization directions of the magnets are parallel and show the same orientation perpendicular to the linear arrangement. As is apparent, the magnetic field is symmetric relative to a plane extending centrally through the magnet along the linear direction (horizontal in  FIG. 5 ), essentially because the magnetic field lines form loops around the two opposites ends of the magnet. 
       FIG. 6  illustrates the lines of the magnetic field produced by a multipole permanent magnet where the poles are alternating. More specifically, the permanent magnet is formed by a linear juxtaposition of a series of permanent magnets where the magnetisation orientations alternate. We can observe that the intensity of the magnetic field is identical on both main sides of the magnet and that the field is periodically alternated compared with the permanent magnet of  FIG. 5  with a single pole orientation. 
       FIG. 7  illustrates a permanent magnet of the same size and shape as those of  FIGS. 5 and 6 , showing however a Halbach array. A Halbach array is a special arrangement of permanent magnets that augments the magnetic field close to a factor of two on one side of the array (compared to the multipole permanent magnet of  FIG. 6 ) while cancelling the field to near zero on the other side. This is achieved by having a spatially rotating pattern of magnetisation. The rotating pattern of permanent magnets (on the front face; on the left, up, right, down) can be continued indefinitely and have the same effect. Such an arrangement is as such known to the skilled person and therefore does not need to be developed further. In  FIG. 7 , we can observe that the magnetisation directions of the permanent magnets that are juxtaposed along the main direction successively change by a rotation of 90°. We can also observe that the magnetic field is more developed on one side, for instance the upper side, than on the other side, for instance the lower side. 
       FIGS. 8 to 10  illustrate the magnetic field lines on a ring-shaped rotor with a classic array of 16 permanent magnets where the magnetisation directions alternate, a corresponding ring-shaped rotor with a Halbach array of 16 permanent magnets where the magnetic field is maximized on the outer side, and a corresponding ring-shaped rotor with a Halbach array of 16 permanent magnets where the magnetic field is maximized on the inner side, respectively. In these figures, the dimensions of the rotor are the same, the permanent magnets are the same and the magnetisation of the poles is the same. We can observe that the magnetic field on the outer side of the rotor in  FIG. 9  is more developed than on the rotor in  FIG. 8 . Similarly, we can observe that the magnetic field on the inner side of the rotor in  FIG. 10  is more developed than on the rotor in  FIG. 8 . 
       FIGS. 11 and 12  illustrate the distribution of the magnetic field modulus B mod of the rotor along the diametrical cross-sections A-A′, B-B′ and C-C′ in  FIGS. 8 to 10 . The magnetic field modulus is expressed in Tesla on the ordinate axis and the position along the cross-section is expressed in mm on the abscissa axis. On  FIG. 11 , the positions of the arms  28 . 1  or  30 . 1  of the yokes of the first exemplary embodiment in  FIG. 1  are illustrated. On  FIG. 12 , the positions of the arms  128 . 1  or  130 . 1  of the yokes of the second exemplary embodiment in  FIG. 2  are illustrated. For both, the two arrows correspond to the magnetization directions of two permanent magnets of the outer surface of the rotor. 
     In  FIG. 11 , the crosses on both magnetic field modulus curves A-A′ and C-C′ correspond to the inner face of the arms of the yokes located outside of the rotor, i.e. to the magnetic field that is “seen” by the yokes of the stator. We can observe that the magnetic field produced in the yoke by the rotor of  FIG. 9 , i.e. with a Halbach array of poles maximizing the magnetic field on the outer side, is substantially higher than the one produced by the rotor of  FIG. 8 , i.e. with a standard alternating array of poles. 
     In  FIG. 12 , the crosses on both magnetic field modulus curves A-A′ and B-B′ correspond to the outer face of the arms of the yokes located inside the rotor, i.e. to the magnetic field that is “seen” by the yokes of the stator. Similarly to  FIG. 11 , we can observe that the magnetic field produced in the yoke by the rotor of  FIG. 10 , i.e. with a Halbach array of poles maximizing the magnetic field on the inner side, is substantially higher than the one produced by the rotor of  FIG. 8 , i.e. with a standard alternating array of poles. 
       FIGS. 13 and 14  illustrate the normal component of the magnetic field along a circular contour Γ around or inside the rotors of  FIGS. 8 to 10 . The normal component of the magnetic field B_n is expressed in Tesla on the ordinate axis relative to an angular position expressed in degrees on the abscissa axis. 
     In  FIG. 13 , the curve Γ A  corresponds to the normal component of the magnetic field along a circular contour around the rotor of  FIG. 9  (Halbach array with outer magnetic field) whereas the curve Γ B  corresponds to the normal component of the magnetic field along a contour of the same diameter around the rotor of  FIG. 8  (standard alternating array). We can observe a substantial increase of the value of the magnetic field with the Halbach array. 
     In  FIG. 14 , the curve Γ D  corresponds to the normal component of the magnetic field along a circular contour inside the rotor of  FIG. 10  (Halbach array with inner magnetic field) whereas the curve Γ c  corresponds to the normal component of the magnetic field along a contour of the same diameter inside the rotor of  FIG. 8  (standard alternating array). We can also observe a substantial increase of the value of the magnetic field with the Halbach array. 
       FIGS. 15 and 16  illustrate two embodiments of a valve to which an electric generator according to the present invention has been integrated. More specifically,  FIG. 15  is a schematic sectional view of a valve for a gas cylinder, according to a first exemplary embodiment, incorporating an electric generator according to the first exemplary embodiment illustrated in  FIG. 1 .  FIG. 16  is a partial schematic sectional view of a valve similar to the valve of  FIG. 15 , according to a second exemplary embodiment, incorporating an electric generator also according to the first exemplary embodiment illustrated in  FIG. 1 . 
     In  FIG. 15 , the valve  34  comprises a body  36  with a gas passage  38  interconnecting a gas inlet  40  with a gas outlet  42  on the body. The valve comprises a pressure reducer  44  that comprises a shutter  44 . 1  cooperating with a seat  44 . 2  where both are arranged in the gas passage  38  for shutting-off the passage. The pressure reducer  44  comprises also a piston  44 . 3  mechanically linked to the shutter  44 . 1  and slidable in a bore formed in the body  36 . The piston  44 . 3  delimits with the bore in the body  36  a regulating chamber  44 . 4  that is downstream of the shutter  44 . 1  and its seat  44 . 2 , and in a chamber  44 . 6  housing a spring  44 . 5  that elastically biases the piston  44 . 3  in a direction that acts on the shutter  44 . 1  so as to open the gas passage  38  in the seat  44 . 2 . A device  44 . 7  for adjusting the pre-constraint of the spring  44 . 5  can be provided. The construction of the regulating valve described here above is as such well known to the skilled person. 
     As is apparent in  FIG. 15 , the electric generator  2  that is integrated in the valve  34  is located in the high pressure part of the gas passage  38 , i.e. upstream of the shutter  44 . 1  and the seat  44 . 2 . As is apparent, a cavity, such as a bore, has been formed in the body for receiving the rotor assembly of the generator, i.e. essentially the shaft  14  carrying the turbine wheel  16  and the rotor  12 . A first bearing  18  is formed in the body for supporting the inner end of the shaft  14 . The cavity in the body  36  is closed in a gas tight fashion by the plug  46  that forms a second bearing  18  for the outer end of the shaft  14 . The yokes  28  and  30  of the stator  26  are inserted into holes or longitudinal cavities formed in the body  36  at the periphery of the cavity housing the rotor  12 . The coil  32  of the stator  26  is then outside of the gas passage  38  of the valve and can be easily connected to any kind of electric or electronic device associated with the valve  34 . 
     Still with reference to  FIG. 15 , the turbine wheel  16  is located in the gas passage  38  such as to be driven by the flow of gas in the passage when the regulator  44  is open. More specifically, flow guiding means  20  can be provided in the passage directly upstream of the turbine wheel  16  in order to accelerate the fluid properly with regard to the design of the turbine wheel  16  so as to maximize the transfer of energy to the wheel. 
     The integration of an electric generator according to the second exemplary embodiment in  FIG. 2  is also possible, similarly to  FIG. 15 . In such a case, the gas passage in the body of the valve can show an annular cavity as illustrated in  FIG. 2 . Similarly to figure, the cavity formed in the body and the gas passage can be closed by a plug or any element that is securely fastened to the body. 
     In  FIG. 16 , only a portion of a valve similar to the valve of  FIG. 15  is illustrated. The reference signs are the same as those of  FIG. 15 . The electric generator  2  is here in the low pressure part of the valve, i.e. downstream of the shutter and the seat of the pressure regulator. For instance, the generator is formed as a cartridge that is mounted on the gas outlet  40  of the valve  34 . The body  4  is for instance formed essentially of a caving  4 . 1  and a plug  4 . 2 . The latter is mounted in a gas tight fashion on the casing  4 . 1  and forms a cavity housing the rotor  12 . It also forms an annular recess around the cavity, receiving the arms of the yokes  28  and  30  of the stator  26 . 
     As is visible in  FIG. 16 , the turbine wheel  16  works axially, i.e. the flow the gas is generally parallel to the axis of the shaft  14 , contrary to the embodiment of  FIGS. 1 and 15 . Also, the outlet  10  of the turbine is located at the periphery of the casing  4 . 1  being however understood that other configurations are possible.