Patent Publication Number: US-11384758-B2

Title: Cylindrical symmetric volumetric machine with an inlet ventilator

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/IB2018/056923 filed Sep. 11, 2018, claiming priority based on Belgium Patent Application No. 2017/5673, filed Sep. 21, 2017. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a cylindrical symmetric volumetric machine. 
     Background 
     A volumetric machine is also known under the name “positive displacement machine”. 
     In particular, the invention is intended for machines such as expanders, compressors and pumps with a cylindrical symmetry with two rotors, namely an inner rotor mounted rotatably in an outer rotor. 
     Such machines are already known and are described in U.S. Pat. No. 1,892,217 among others. It is also known that the rotors can have a cylindrical or conical shape. 
     It is known that such machines can be driven with an electric motor. 
     From Belgian patent application no. BE 2017/5459 it is already known that the electric motor can be mounted around the outer rotor, whereby the motor stator directly drives the outer rotor. 
     Such machine has many advantages in relation to the known machines whereby the motor shaft is connected by means of a transmission with the rotor shaft of the outer or inner rotor. 
     Thus, the machine will not only be a lot more compact, such that the footprint is smaller, it also means less shaft seals and bearings are required. 
     The efficiency of the machine is largely determined by the fill ratio of the so-called compression chamber, this is a space between the lobes of the rotors which will move by rotation of the rotors from the inlet side to the outlet side and thereby decreases in volume such that the gas enclosed in the space will be compressed. 
     The purpose of the present invention is to improve the fill ratio of such machine. 
     SUMMARY OF THE INVENTION 
     To this end, the invention relates to a cylindrical symmetric volumetric machine, whereby the machine comprises a housing with two co-operating rotors therein, namely an outer rotor mounted rotatably in the housing and an inner rotor mounted rotatably in the outer rotor, whereby a compression chamber is located between the rotors, which moves by rotation of the rotors from the inlet side to the outlet side, characterised in that the inlet side of the outer rotor is provided with a ventilator, to supply air to the compression chamber. 
     This provides the advantage that the ventilator will ensure a centripetal flow of air at the inlet, such that a better filling of the compression chamber is obtained. 
     Therefore, the performance of the machine will increase. 
     This will also offset any premature compression chamber volume reduction occurring before it closes. 
     Another advantage is that the actively sucked in air is also suitable to cool, for example, a motor which drives the machine, the outlet or the oil that is used for the lubrication and/or cooling of components of the machine. 
     That can be realised by sending the sucked in air along or via said components before it ends up in the compression chamber. 
     In a practical embodiment the outer rotor is provided with an attachment on its inlet side wherein the ventilator is built in, which is attached to the outer rotor. 
     This attachment can consist of a hollow cylindrical element, which is placed with its axis in the extension of the axis of the outer rotor. 
     According to a preferred characteristic of the invention the outer rotor is mounted rotatably in the housing by means of a bearing on or to said attachment. 
     The advantage is that a smaller bearing can be used. Indeed, the attachment can itself be provided with a radially inward oriented collar, for example, such that the bearing can be attached to or on this collar. 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
       With the intention of better showing the characteristics of the invention, a few preferred embodiments of a cylindrical symmetric volumetric machine according to the invention are described hereinafter by way of an example, without any limiting nature, with reference to the accompanying drawings, wherein: 
         FIG. 1  schematically shows a cylindrical symmetric volumetric machine according to the invention; 
         FIG. 2  shows a cross-section according to line II-II of  FIG. 1 ; 
         FIG. 3  schematically shows an alternative embodiment of the section indicated in  FIG. 1  with F 3 ; 
         FIG. 4  schematically shows a variant of  FIG. 3 ; 
         FIG. 5  schematically shows another variant of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The machine  1  schematically shown in  FIG. 1  is a compressor device in this case. 
     According to the invention it is also possible that the machine  1  relates to an expander device. The invention can also relate to a pump device. 
     The machine  1  is a cylindrical symmetric volumetric machine  1 . This means that the machine  1  has a cylindrical symmetry, i.e. the same symmetrical properties as a cone. 
     The machine  1  comprises a housing  2  that is provided with an inlet opening  3  to suck in gas to be compressed and with an outlet opening  4  for compressed gas. The housing defines a chamber  5 . 
     Two co-operating rotors  6   a ,  6   b , namely an outer rotor  6   a  mounted rotatably in the housing  2  and an inner rotor  6   b  mounted rotatably in the outer rotor  6   a  are located in the chamber  5  in the housing  2  of the machine  1 . 
     Both rotors  6   a ,  6   b  are provided with lobes  7  and can turn into each other co-operatively, whereby between the lobes  7  a compression chamber  8  is created, the volume of which can be reduced by the rotation of the rotors  6   a ,  6   b , such that the gas that is caught in this compression chamber  8  is compressed. The principle is very similar to the known adjacent co-operating screw rotors. 
     During the rotation of the rotors  6   a ,  6   b , said compression chamber  8  moves from one end  9   a  of the rotors  6   a ,  6   b  to the other end  9   b  of the rotors  6   a ,  6   b.    
     The end  9   a  will also be referred to as the inlet side  9   a  of the inner and outer rotor  6   a ,  6   b  and the end  9   b  of the inner and outer rotor  6   a ,  6   b  will be referred to as the outlet side  9   b  in what follows. 
     In the example shown, the rotors  6   a ,  6   b  have a conical shape, whereby the diameter D, D′ of the rotors  6   a ,  6   b  decreases in the axial direction X-X′. However, this is not necessary for the invention; the diameter D, D′ of the rotors  6   a ,  6   b  can also be constant or vary in another way in the axial direction X-X′. 
     Such design of rotors  6   a ,  6   b  is suitable both for a compressor and expander device. Alternatively, the rotors  6   a ,  6   b  can also have a cylindrical form with a constant diameter D, D′. They can then either have a variable pitch, such that there is a built-in volume ratio, in the case of a compressor or expander device, or a constant pitch, in the case the machine  1  relates to a pump device. 
     The axis  10  of the outer rotor  6   a  and the axis  11  of the inner rotor  6   b  are fixed axes  10 ,  11 , this means that the axes  10 ,  11  will not move in relation to the housing  2  of the machine  1 , however they do not run parallel, but are located at an angle α in relation to each other, whereby the axes intersect in point P. 
     However, this is not necessary for the invention. For example, if the rotors  6   a ,  6   b  have a constant diameter D, D′, the axes  10 ,  11  can nevertheless run parallel. 
     According to the invention the inlet side  9   a  of the outer rotor  6   a  is provided with a ventilator  12 , to supply air to the compression chamber  8 . 
     This means that the ventilator  12  will turn with the outer rotor  6   a , such that when the rotors  6   a ,  6   b  turn, the ventilator  12  will also start running. 
     In this case the ventilator  12  is a radial ventilator  12 . 
     In the example shown in  FIGS. 1 and 2 , the outer rotor  6   a  is provided with an attachment  13  on the inlet side  9   a  in which the ventilator  12  is built in, which is attached to the outer rotor  6   a.    
     In this case, the attachment  13  comprises a hollow cylindrical form, which is placed with its axis in the extension of the axis  10  of the outer rotor  6   a.    
     The attachment  13  has a wall  14  with a certain thickness A, whereby ventilator blades  15  have been mounted in this wall  14 . 
     It is not excluded that the height of one or more of the blades  15  decreases axially from the inside to the outside in the radial direction. 
     In this way the reduced contour can be accommodated. 
     The rotors  6   a ,  6   b  are mounted on bearings in the machine  1 , whereby the inner rotor  6   b  on one end  9   a  is mounted in the machine  1  on a bearing  16  and the other end  9   b  of the inner rotor  6   b  is supported or borne by the outer rotor  6   a  as it were. 
     In the example shown, the outer rotor  6   a  is mounted at both ends  9   a ,  9   b  in the machine  1  with bearings  17 ,  18 . 
     As shown in  FIG. 1 , the outer rotor at the inlet side  9   a  is mounted rotatably in the housing  2  by means of a bearing  17  on or to said attachment  13 . 
     The attachment  13  is provided with a radially inward oriented collar  19 , on which said bearing  17  is mounted. 
     Consequently this bearing  17  can be made much smaller, i.e. with a smaller diameter, compared to the case whereby the bearing  17  is mounted directly on the outer rotor  6   a  itself. 
     Further, the machine  1  is also provided with an electric motor  20  which will drive the rotors  6   a ,  6   b . This motor  20  is provided with a motor rotor  21  and a motor stator  22 . 
     In this case, but not necessarily, the electric motor  20  is mounted around the outer rotor  6   a  whereby the motor stator  22  directly drives the outer rotor  6   a.    
     In the example shown, this is realised because the outer rotor  6   a  also serves as motor rotor  21 . 
     The electric motor  20  is provided with permanent magnets  23  which are embedded in the outer rotor  6   a.    
     It is also possible of course that these magnets  23  are not embedded in the outer rotor  6   a , but are mounted on the outside thereof for example. 
     Instead of an electric motor  20  with permanent magnets  23  (i.e. a synchronous permanent magnet motor), an asynchronous induction motor can also be applied, whereby the magnets are replaced with a squirrel-cage rotor. 
     Induction from the motor stator generates a current in the squirrel-cage rotor. 
     On the other hand, the motor  20  can also be a reluctance type or induction type or a combination of types. 
     The motor stator  22  is mounted around the outer rotor  6   a  in a covering way, whereby in this case it is located in the housing  2  of the machine  1 . 
     In this way the lubrication of the motor  20  and the rotors  6   a ,  6   b  can be controlled together, as they are located in the same housing  2  and consequently are not closed off from each other. 
     The operation of the device  1  is very simple and as follows. 
     During the operation of the machine  1 , the motor stator  22  will drive the motor rotor  21  and therefore drive the outer rotor  6   a  in the known way. 
     The outer rotor  6   a  will help drive the inner rotor  6   b , and by the rotation of the outer rotor  6   a , the ventilator  12  will also turn. 
     Due to the operation of the ventilator  12  gas will be sucked in via the inlet opening  3 . This gas will end up in the compression chamber  8  between the rotors  6   a ,  6   b.    
     Because the ventilator  12  will ensure an active supply or flow of gas, the fill ratio of the compression chamber  8  will be increased. 
     Furthermore, the gas, when the gas is sucked in via the inlet opening  3 , will flow past the motor rotor  21  and the motor stator  22 . In this way the gas will be able to ensure an active cooling of the motor  20 . 
     Due to the rotation this compression chamber  8  moves to the outlet  4  and at the same time will reduce in terms of volume to thus realise a compression of the gas. 
     The compressed gas can then exit the machine  1  via the outlet opening  4 . 
     It is not excluded that during the compression, liquid is injected in the machine  1 . 
     Said liquid can both be water and a synthetic or non-synthetic oil. 
       FIG. 3  shows an alternative embodiment of the ventilator  12 , whereby it is now an axial ventilator  12 . 
     In this case the attachment  13  is not cylindrical, but more conical. This, however, is not necessary. The axial ventilator  12  is built into the radially inward oriented collar  19 . 
     In  FIG. 4  the radial ventilator  12  of  FIG. 1  is shown in combination with an additional axial ventilator  12   a  which are placed in series with each other. 
     In this case the additional axial ventilator  12   a  is placed in front of the radial ventilator  12 , seen in the flow direction of the sucked in air. It is also possible of course that the radial ventilator  12  is placed in front of the additional axial ventilator  12   a.    
     The additional axial ventilator  12   a  is mounted around the attachment  13 . 
       FIG. 5  shows an additional variant whereby in this case the ventilator  12  is a mixed axial-radial ventilator  12 , whereby the blades  15  have both an axial and a radial section. 
     The operation of the ventilator  12  in the embodiments of  FIGS. 3 to 5  is analogue to the operation of the embodiment in  FIGS. 1 and 2 . 
     The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but a cylindrical symmetric volumetric machine according to the invention can be realised in all kinds of forms and dimensions, without departing from the scope of the invention.