NL2016675B1

NL2016675B1 - Displacement machine.

Info

Publication number: NL2016675B1
Application number: NL2016675A
Authority: NL
Inventors: Ernest Gardner Fred; Berend De Jong Jarno
Original assignee: Teamwork Tech B V
Priority date: 2016-04-25
Filing date: 2016-04-25
Publication date: 2017-11-07

Abstract

The invention relates to a displacement machine comprising a housing, a first rotor in the housing on a first shaft, a second rotor in the housing on a second shaft, synchronising means to synchronise both shafts, the first rotor comprising a cylindrical centre body and at least two blades extending in radial direction from the centre body, the second rotor comprising a cylindrical centre body and at least one protrusion extending from the centre body in radial direction, the protrusion meshing with the blades, two channels connected to the housing at either side of the plane connecting both shafts, the housing comprising side walls enclosing the path of the blades and of the path of the protrusions, wherein the protrusions extend together over more than half of the circumference of the second rotor, and the blades fit into cavities between the protrusions on the second rotor.

Description

Displacement machine

The present invention concerns a displacement machine, such as a pump. Pumps are driven to cause displacement of a fluid, but displacement machines also comprises machines which are driven by a fluid to cause rotation of a shaft such as turbines. Displacement machines also comprise machines which are adapted to perform both functions, that is conversion of mechanical energy of a rotating shaft into kinetic energy of a fluid and conversion of kinetic energy of a fluid into mechanical energy of a rotating shaft.

Prior art provides displacement pumps of the types known as rotary vane pumps, lobe pumps or external circumferential piston pumps. These pumps may be used to pump a fluid, but they may also be used to be driven by the fluid, so that they are displacement machines.

Prior art provides displacement machines, comprising a housing, a first rotor located in the housing and mounted to a first shaft, being adapted to transfer mechanical energy, a second rotor located in the housing and mounted on a second shaft extending parallel to the first shaft, synchronising means connected to the first shaft and to the second shaft, and adapted to synchronise the rotation movement of both shafts, the first rotor comprising a substantially cylindrical centre body and at least two blades extending in radial direction form the centre body, the second rotor comprising a substantial cylindrical centre body and at least two protrusions extending from the centre body in radial direction, the protrusions meshing with the blades of the first rotor, a first channel and a second channel ending in the housing at either side of the plane connecting the first and the second shafts, wherein the housing comprising side walls adjacent to the end faces of the first and second rotors and enclosing a part of the path of the blades of the first rotor and of a part of the path of the protrusions of the second rotor. Preferably the first shaft is connected to an energy converter.

Often the blades on the first rotor are identical to the protrusions on the second rotor, as is the case in the types of pumps mentioned above. Then both the blades and the protrusions extend over a small circumferential section of the rotor concerned. In these pumps, the path of fluid coming from one of the channels is separated into two substantially identical paths, both extending between the housing and the cylindrical centre bodies of the first and the second rotors respectively. There is only a small fluid path between the two rotors in the opposite direction. The separation of the paths and the subsequent unification of the paths leads to turbulence of the fluids and hence to losses. Please note that this is the case both when the displacement machine acts as a pump and when it acts as a turbine.

The aim of the invention is to provide a displacement machine wherein the losses caused by this turbulence are minimized.

This aim is reached in that the total extensions of the protrusions on the second rotor is more than half of the circumference of the second rotor and that the blades of the first rotor fit into the cavities between the protrusions of the second rotor. The blades of the first rotor fit into the cavities between the protrusions of the second rotor, thus blocking the path between the rotors just as in prior art devices. The protrusions limit the flow over the path between the second rotor and the housing to a minimal extend, as the cavities between the protrusions of the second are small and they are filled with the blades of the second rotor over the sections of the paths where they mesh. Thus only the path between the first rotor and the housing remains, avoiding the separation and unification of the fluid flows, avoiding turbulences and minimizing losses. Further the fact that only a small number of blades is present, allows a large volume of fluid to be transported, via het path concerned as only a limited volume is taken by the blades. The first shaft, adapted to transfer mechanical energy may be connected to a power converter, such as an electrical machine.

Preferably the ratio between the rotational speed of the first rotor and the second rotor is equal to the ratio between the diameter of the cylindrical body of the second rotor and the diameter of the first rotor. This feature ensures that the circumferential speed of the blades is equal to that of the protrusions, allowing to use an even rotational speed for both rotors.

Preferably the ratio between the number of blades on the first rotor and the number of protrusions on the second rotor is equal to the ratio between the diameter of the cylindrical body of the first rotor and the diameter of the cylindrical body of the second rotor. Also this features adds to the regularity of the movement of the blades and the protrusions, again minimizing turbulence.

Although other means are not excluded, a simple mechanical solution provides the feature that the synchronising means comprise a gear box connected to the first shaft and the second shaft.

To further closes off the path between the second rotor and the housing, it is preferred that the housing comprises wall parts enclosing the second rotor except for the section in which the blades of the first rotor extend into the cavities of the second rotor.

When the walls of the blades contacting the protrusions and the walls of the protrusions contacting the blades are formed according to the involutes of the circumferences of the cylindrical bodies of the first and second rotors respectively, the movement of both rotors is smoothed, minimizing turbulence and associated losses. A preferred embodiment provides the feature that the blades are bifurcated at their distal ends and that the outer walls of the bifurcated sections have a cylindrical surface.

The bifurcated blades cooperate with cavities having curved sidewalls, and this shape minimizes the transport of the fluid in the cavities and hence over the path between the second rotor and the housing.

To minimise friction losses, it is preferred that the housing extends on a small distance from the rotors, the blades and the protrusions.

Preferably the cross sectional areas of the first and the second channels gradually increase with increasing distance from the housing. These features lead to a gradual increase of the fluid speed in the displacement machine, leading to a smaller volume of the machine, without causing turbulences in the fluid.

According to a further preferred embodiment, the first channel and the second channel extend from the housing in substantial tangential direction of the first rotor.

This layout allows the fluid to enter and leave the displacement machine without substantial changes of direction and associated power losses.

To adapt the displacement machine to fit into a substantial cylindrical space, it is preferred that the first channel extends to a spiral shape and that the second channel extends with an axial directional component.

The present invention also relates to an energy conversion device comprising a displacement machine of the kind referred to above and an electrical machine connected to the first shaft and that the energy conversion device comprises a control device adapted to control the torque to be generated by the electrical machine. Although other energy conversion devices, such as fuel cells and pumps are not excluded, the electrical machine has the advantages of high controllability, high efficiency and the ability to operate both as a generator and as a motor. Further it is not excluded that the displacement machine is connected to processing device such as a saw or an external pump.

An application especially suited for the displacement machine of the kind referred to above resides in an energy conversion device comprising a first fluid vessel connected to the first channel and a second fluid vessel connected to the second channel and that the volume of at least one of the vessels is periodically variable under the influence of an external force. Although the inclusion of an electrical machine is now regarded to be the most feasible, in view of its ability to convert energy in both directions, other types of energy converters are not excluded. It is for instance possible to connect the displacement device to two different energy converters of which one is suitable for conversion of energy into mechanical energy of the shaft and the other is suitable for conversion of mechanical energy of the shaft into another form of energy.

Preferably the control device is adapted to measure the frequency of the periodically variable external force and to control the torque to be generated by the electrical machine to cause resonance of the movement of the fluid with the external force. The resonance allows to extract more power from the external forces.

Due to its wide availability, it is attractive to use wave energy as a source of energy. An embodiment suited for this application provides an energy conversion unit of the kind referred above wherein the energy conversion unit is a floating device comprising two external sections mutually moveable, both being subject to wave motions, wherein one of the fluid vessels is connected to at least one of the external sections.

Preferably the floating device is adapted to float under the water surface and that both external sections are subject to wave motions, leading to a device as disclosed in EP-A-2 873 852.

Subsequently the present invention will be elucidated with the help of the accompanying drawings, wherein show:

Figure 1: a cross-sectional view of a displacement machine according to the invention;

Figure 2: a cross-sectional view corresponding to the line II-II in figure 1;

Figure 3: a cross-sectional detailed view of an alternative configuration of the meshing parts of the displacement machine depicted in figures 1 and 2;

Figure 4: a cross-sectional view of an alternative embodiment of a displacement machine according to the invention;

Figure 5: a broken away view of the machine depicted in figures 1 and 2, with added channels; and

Figure 6: a diagrammatic perspective view of the machine depicted in figure 5.

Figure 1 discloses a displacement machine designated with 1 as a whole. The displacement machine 1 can act as a pump or as a turbine. The machine comprises a substantially cylindrical housing 2 having the substantial shape of the number 8. A first shaft 3 and a second shaft 4 extend mutually parallel and parallel to the axis of the housing 2. On the first shaft 3 a cylindrical first centre body 5 is provided and on the second shaft 4 a cylindrical second body 6 has been provided, thus forming a first rotor and a second rotor respectively.

In the embodiment depicted the cylindrical first and second central bodies 5, 6 have the same diameter. On the tangential surface of the first central body 5 three blades 7a, 7b, 7c have been provided, all having identical substantially triangular shapes, thus forming a first rotor 3, 5, 7. On the tangential surface of the second central body 6 three protrusions 8a, 8b, 8c have been provided cavities 9a, 9b and 9c are left between the protrusions 8a, 8b and 8c, thus forming a second rotor 4, 6, 8. The tangential surfaces of the blades 7 and the protrusions 8 are cylindrical. The tangential surfaces are located on a small distance from the inner face of the housing 2, leaving a minor slit 10 between these mutually moving parts. The blades 7 mesh with the protrusions 8, so that the blades extend into the cavities 9. In the situation depicted in figure 1, the blade 7a extends into the cavity 9a between the protrusions 8c and 8a. A first channel 11 connects to the space in the housing at the right hand side of the plane extending between the axes of the shafts 3, 4 and a second channel 12 connects to the space in the housing at the left hand side of the plane extending between the axes of the shafts 3, 4. These channels 11 and 12 function as supply channel and drain channel respectively, depending on the rotational direction of the rotors 3, 5, 7; 4, 6, 8.

In a situation wherein a fluid, such as a liquid is provided through the channel 11, and the displacement machine 1 functions as a turbine, the liquid enters the space at the right hand side of the rotors 3, 5, 7; 4, 6, 8. As the paths between the two rotors and between the second rotor 4, 6, 8 and the housing 2 are closed, the fluid is urged to pass through the path between the first rotor 3, 5, 7 and the housing 2, urging the blades 7 in the direction of flow thus making the first rotor rotate. After having reached the space at the left hand side of the rotors 3, 5, 7; 4, 6, 8, the liquid leaves the housing via the channels 12. In this process the first rotor 3, 5, 7 rotates clockwise. In the present embodiment the displacement machine is symmetric, which is advantageous when the direction of flow varies. In other situations, wherein for instance the direction of flow is always the same, it may be attractive to use an asymmetric configuration, which can be optimized for that direction of flow.

Another variation resides in the function the device, as it operates preferably intermittently as a pump or as a turbine. This function is independent from the flow direction. In some situations, the displacement machine 1 acts as a pump in one direction of flow and acts as a turbine in the opposite direction, in which an asymmetric configuration may be advantageous as well. It is however also possible that the device acts both as a pump and as turbine in the same direction of flow.

It is of course also possible to have the direction of flow reversed, which results in a different rotational direction of the rotors 3, 5 ,7; 4, 6, 8. Further it is possible that the displacement device 1 works as a pump rather than as a turbine. In such a situation the fluid is propelled by the blades 7. Depending on the direction of rotation, the direction of flow may vary as well. Also in the situations wherein the displacement machine 1 acts as a pump, there is only one path for the fluid, thus minimizing turbulence.

As appears clearly from figure 2, the shafts 3, 4 are journaled in bearings 13a, 13b and 14a, 14b respectively which have been provided in the housing 2. To synchronise rotation of the second rotor 4, 6, 8 with the rotation of the first rotor 3, 5, 7, the apparatus 1 comprises a gear set 15, 16 depicted in figure 2. The gear set comprising a first gear 15 fixed on the first shaft 3 and a second gear 16 fixed on the second shaft 4. The first gear 15 meshes the second gear 16, synchronising the rotation of both rotors 3, 5, 7; 4, 6, 8. In the presented embodiment the rotors have the same diameter, so that the rotational speed of the and rotors must be equal, and both gears 15,16 have the same diameter and the same number or teeth.

It is however also possible to use rotors with different diameters. To obtain an equal circumferential speed at the location where the rotors mesh, the ratio between rotational speeds of the two rotors 3, 5, 7; 4, 6, 8 must be equal to the ratio between the diameters of the two rotors. In such a situation the sizes of the gears 15, 16 must be adapted accordingly.

The above relates to the actual displacement machine 1, which is preferably part of an energy conversion device. Such an energy conversion device preferably comprises an electric machine as an energy converter. As depicted in figure 2, the shaft 3 of the lower rotor is connected to an electric machine 20. The electric machine 20 operates as an electric motor when the displacement machine 1 acts as pump, allowing to convert electrical energy into flow energy of the fluid and it operates as an electric generator when the displacement machine acts as a turbine, allowing to convert flow energy of the fluid into electrical energy.

In figure 1 only one shape of the blades 7 and the protrusions 8 are shown. It is possible to use other shapes as is depicted in figure 3. Figure 3 shows a detailed view of an embodiment comprising blades and protrusions having different shapes. On the first central body 5 blades 27 having the shapes of normal teeth of gears are provided, while on the second central body 6 protrusions 28 having sides equivalent to the sides of the blades 27 are provided.

In figure 4 a displacement machine with rotors having unequal diameters and with unequal numbers of blades and protrusions are shown. More in particular the first rotor comprises three blades 7a, 7b, 7c and the second rotor comprises two protrusions 8a, 8b and hence two cavities 9a, 9b. The diameter of the second central body 6 is two thirds of the diameter of the first central body 5, to reflect the equal distances between the blades 7 and the cavities 9 respectively. To reflect the different diameters, the rotational speeds of the rotors differ also a factor 2/3, to obtain an equal circumferential speed.

As stated before, the displacement machine according to the invention is particularly suitable to be incorporated into an energy converter, often an energy converter, wherein the displacement machine is connected between two vessels of which at least one has e varying volume. Then the displacement machine often has to be located under restricted spatial requirements, nevertheless allowing connections to the two vessels with channels. In figure 5 a possible embodiment for such a situation is depicted. In this embodiment the first channel 11 is subjected to a curve of roughly 180°, departing from the housing 2 and the second channel 12 is curved over about 270°, wherein the second channel 12 encompasses the first channel 11. This leads to a configuration similar to that of a spiral casing.

Apart therefrom the first channel 11 further extends also in a radial direction relative to the axes of the displacement machine, as needed by the spatial requirements. The configuration is better apparent from figure 6, showing the same device from another point of view. This drawing also shows a tank 30 functioning as a vessel for liquid which is pumped into an from said vessel from and into a second vessel which is not depicted in the drawings. The embodiment depicted in figures 5 and 6 is adapted to be located in an apparatus as discloses in the European patent application EP-A-2 873 852. This document discloses a device for converting energy from wave motions at sea to another form of energy, provided with a fixed element and an element movable relative to the fixed element, which elements are configured to be subjected to the wave motions and wherein the elements enclose a vessel, the volume of which varies with the relative movements of the elements and an energy conversion device for converting the mechanical energy from the relative movement between the fixed element and the movable element to another form of energy. Herein the present invention relates to the energy conversion device and more in particular to the displacement machine for converting the flow of the fluid into mechanical energy.

It will be clear that the present invention is not restricted to such applications and that the it may be applied in other situations. Further the scope of the invention is not restricted to the depicted and described embodiments, as features disclosed in different embodiments may be combined, but the scope of the invention is determined by the wording of the claims.

Claims

A displacement machine, comprising: - a housing; - a first rotor placed in the housing and placed on a first shaft which is adapted to transfer mechanical energy; a second rotor placed in the housing and placed on a second axis extending parallel to the first axis; - synchronization means connected to the first axis and to the second axis and adapted to synchronize the rotational movement of both axes; - wherein the first rotor comprises a substantially cylindrical central body and at least two blades extending radially from the central body; - wherein the second rotor comprises a substantially cylindrical central body and at least one protrusions extending radially from the central body, wherein the at least one protrusion engages between the blades of the first rotor and has the same radial extension as the blades; - a first channel and a second channel which are each connected to the housing on one side of the plane connecting the axis of both rotors; - wherein the housing comprises side walls connecting to the end wall of the first and the second rotor, as well as parts which enclose the path of the blades of the first rotor and of the protrusions of the second rotor, characterized in that the protrusions on the the second rotor extends over more than half the circumference of the second rotor and that the blades of the first rotor fit into cavities between the protrusions on the second rotor.

Displacement machine according to claim 1, characterized in that the ratio between the rotational speed of the first rotor and that of the second rotor is equal to the ratio between the diameter of the central body of the second rotor plus half the radial dimension of the protrusions and the diameter of the central body of the first rotor plus half the radial dimension of the blades.

Displacement machine according to claim 1 or 2, characterized in that the ratio between the number of blades of the first rotor and the number of protrusions of the second rotor is equal to the ratio between the diameter of the central body of the second rotor plus the half the radial dimension of the protrusions and the diameter of the central body of the first rotor plus half the radial dimension of the blades.

Displacement machine according to claim 1, 2 or 3, characterized in that the synchronizing means comprise a gearbox connected to the first and the second shaft.

5. Displacement machine according to one of the preceding claims, characterized in that the housing comprises wall parts which extend around the second rotor with the exception of the section where the blades of the first rotor extend into the cavities between protrusions of the second rotor.

A displacement machine according to any one of the preceding claims, characterized in that the walls of the blades which touch the protrusions and the walls of the protrusions which touch the blades are formed according to the involute of the circumference of the cylindrical bodies of the first, the second rotor, respectively.

Displacement machine according to claim 6, characterized in that the blades are forked at their distal end and that the outer wall of the forked parts has a cylindrical surface.

Displacement machine according to one of the preceding claims, characterized in that the housing extends a small distance from the rotors, the blades and the projections.

Displacement machine according to one of the preceding claims, characterized in that the cross-sectional area of the first and the second channel increases with increasing distance from the housing.

Displacement machine according to one of the preceding claims, characterized in that the first and the second channel extend from the housing in substantially tangential direction with respect to the first rotor.

11. Displacement machine according to claim 10, characterized in that the first channel extends in a spiral form and that the second channel extends with an axial component.

Device for converting energy, comprising a displacement machine according to one of the preceding claims, characterized in that the first axis of the displacement machine is connected to an electrical machine and that the device for converting energy comprises a control device for controlling of the torque generated by the electric machine.

An energy conversion device according to claim 13, characterized in that the energy conversion device comprises a first fluid vessel connected to the first channel and a second fluid vessel connected to the second channel and the content of at least one of the fluid vessels is periodically variable under the influence of a periodic external force.

An energy conversion device according to claim 13, characterized in that the control device is adapted to measure the frequency of the periodically variable external force and to control the torque to be generated by the electric machine for obtaining of resonance of the movement of the fluid with the periodic external force.

An energy conversion device according to claim 14, characterized in that this device is formed by a floating device, which is provided with two mutually movable external parts, both of which are subject to wave movements and which is then one of the fluid vessels connected to at least one of the external parts.

An energy conversion device according to claim 15, characterized in that the floating device is arranged to float below the water surface and that both parts are subject to wave movements.