GB2075121A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

A pump, motor or engine of the sliding-vane type has radial, or diametral, vanes 1-6 mounted in a cylindrical rotor and engaging with an encircling cam surface on the casing, the profile of said surface being non-circular and defined mainly by mathematical expressions (see specification). The machine may be double-acting, Fig. 20 (not shown). <IMAGE>

Description

SPECIFICATION Volumetric bladed machine This invention relates to a volumetric bladed machine known as a "rotary pump".

A certain number of bladed machines satisfying this general description have been proposed over a considerable period for compressing, pumping or expanding various fluids. These machines are generally designed as a compromise between the different constraints classically imposed on them (piston displacement, volumetric ratio, chamber shape, arrangement, number and shape of the blades the forces on the blades, the sliding speed over the casing and the variation therein, simplicity of manufacture and morphological control etc.).

We prefer to make this compromise less stringent by utilising an original geometrical definition for the casing, possibly associated with a special arrangement of the blades, this approach leading to the construction of machines with novel possibilities.

According to the invention, a volumetric bladed machine, also known as a bladed rotary pump, constructed of any known material, using any type of fluid, and operating as a drive or driven machine, comprising: - a cylindrical piston with a circular directrix comprising p slots, - a casing surrounding said piston and comprising a shell, - a set of p blades of any geometry, sliding in the piston slots and in contact with the casing in such a manner as to separate the useful volume of the rotary pump into several working chambers, said blades able to comprise auxiliary sealing elements, rollers or segments, and mechanical or hydraulic devices for improving or controlling their contact with the casing, - an admission and discharge arrangement using ports and/or controlled or automatic valves.

The directrix of the casing shell is a curve at a uniform distance D from a continuous curve of order of symmetry s, constituted successively by the following curve arcs, repeated s times: - a circumferential arc (1) of radius (Rm - E - D), centred on a point 0 and of angular width a1, Rm and E being two positive constants, D representing a positive or negative number or possibly zero according to whether the shell directrix is external or internal to or is identified with said arc, - a connection arc (2) of angular width a2 -a1, - a connection arc (3) of angular width &alpha;3 - &alpha;2, - a circumferential arc (4) of radius (Rm + E - D), centred on the same point 0 and of angular width &alpha;4 - a connection arc (5) of angular width &alpha;;5 - - connection arc (6) of angular width 2X/s - a5.

In the plane of the complex variable z centred on O [z = x + jy = Re(z) + j Im(z) where j2 = - 1], the equation of the curve constituting the arcs (1) to (6) can be written generally as: z = [Rm + F, (8) - D] expj z#.

In this expression, Rm represents the mean radius of the shell directrix, O and expj respectively signify the polar angle and the imaginary exponential function respectively, Fj (O) are real functions of the polar angle which define the geometry of the arc i, and consequently exist only within the range (&alpha;i - 1,&alpha;1). These functions satisfy the following relationships: F1(#) = - E = F2(al) = F(2"'/s) F2(a2) = F3(a2), F5(a5) = Fs(as) F4(0) = + E = R3(&alpha;3) = F5(a4) (1).

For i = 2, 3, 5 and 6, within the range [a, - l'ql,, the functions Fj(8) are chosen freely, on the condition that they are defined algebraically, are continuous and can be differentiated at least n times, including at the extremities al a, of this range (n is any whole number greater than one), the derivatives with respect to 0, up to the order n, of F2(a,), F3(a3), F5(a4) and F6(27T/S) being zero, the derivatives with respect to 0, up to the order n, of F2(a2) and F3(a2) being equal to each other, as are the derivatives of F5(a5) and F6(a5).

With these definitions and notations, the equation of the shell directrix can be written: z = [Rm + F1(#) - D] expj 8 + D expj ii (II) where # lm(dz/d0) 7r dz IL = IL" + d", - - < K + arctg < ~if Re( ) # O 2 Re(dz/dS) 2 dO dz ju* = y/2 + ## if Re( ) = 0 dO dz s = O if Re ()3 0 dO dz e = O if lm(-) > 0 dO dz s = 1 if Re( -) < 0 dO dz = 1 if lm(-) < 0.

dO In these expressions, EL is the angle which the external normal makes to the axis of the ox abscissas.

As for the functions F1(0), the limits of their definition ranges are chosen freely, on condition that the following progression is satisfied: O < a, < a2Sa3 < a4 < a5S2v/s (III).

It should be noted that if a2 = a3, the connection arc (3) vanishes, the arc (2) being connected directly to the circumferential arc (4). On this basis, a5 can be made equal to 2m/s, in which case the connection arc (6) disappears.

Such characteristics still conform to the invention, with the conditions (1) imposed on the functions F,(O) for i = 2, 3, 5 and 6 then being written in the following form: F,(e) = - E - F2(a1) = F5(27T/S) F4(8) = + E = F2(a3) = F5(a4) (I).

From the definition for the directrix given here, it can be seen that the different arcs which constitute the curve from which it is uniformly distant, are connected together with a continuity of an order n which is at least equal to two and which can be as large as required.

With the casing thus defined, there is associated a cylindrical piston with a circular directrix of radius Rm - E - J centred on 0, J signifying the gap necessary in order to prevent contact between said two elements during operation, taking account of their deformation of any origin.

This piston, which rotates about its axis, is provided with p radial slots (p being any positive whole number), as a rule uniformly spaced apart, in which slide blades which can come into contact with the shell.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows in section a rotor inside a casing according to the present invention; Figures 2-10 show in more detail various arrangements of the blades of the rotor; Figure 11 shows in section an alternative rotor inside a casing, and Figs. 12-14 show schematically lengths of blades for such a rotor; Figure 15 shows in section the provision of seals at the end of the blades; Figure 16 shows in elevation a seal at one end of the blade; Figure 1 7 shows in greater detail a seal; Figure 18 shows in section an auxiliary track for use with a rotor; Figure 19 shows in elevation the auxiliary track shown in Fig. 18; and Figure 20 shows in section a rotor inside a casing having a cam within an annular piston.

The resultant mechanical arrangement is shown by way of example in Fig. 1, which is drawn for the particular values of: s = 1 p = 6 and a, - a, - 1 = 2/ps.

In the example considered, the fluid intake and discharge are provided for by 2s = 2 ports disposed in the shell, with an angular width of 4n/ps = 2it/3. It is apparent that the object of the invention is attained whether the ports are disposed partly or totally in the side plates, in the blades or in the rotor, in these latter two cases this implying one or more internal chamber or chambers collecting fluid.

The same is true if the angular widths are different, if the ports are split up into several elements disposed in series or parallel, or if they are partly or totally replaced by valves of any generally known type.

The six blades 1 to 6 of the machine shown in section in Fig. 1 define six independent chambers, the volume of which vary periodically between two extreme values. In the position shown in Fig. 1 and with the direction of rotation used, the chamber lying between the blades 1 and 2 defines the dead space of the machine, and performs a sealing function by constriction between the discharge and intake. The chambers lying between the blades 2 and 4 are in communication with the intake, and their volume increases with the rotation of the piston up to a maximum attained by the chamber bounded by the blades 4 and 5. In the position shown, this chamber simply transfers the fluid from the intake to the discharge without varying its volume.Finally, the chambers lying between the blades 5 and 1 are characterised by a reduction in their volume with the piston rotation, and they deliver the fluid to the discharge duct.

By virtue of its basic principle, this construction is ideally suitable for pumping or for being driven by incompressible fluids. With other intake and discharge arrangements, it can equally transfer fluid with partial or total volume compensation.

As a modified embodiment of the invention, the slots in the rotor could be inclined at an angle I to the radial direction as shown in Fig. 2. Such an arrangement is interesting, because if the value of I is chosen wisely, it allows the inertia reactions on the blades to be reduced, and consequently the stresses to which they are subject.

The blades used in the invention are of any generally known geometry and material. They could also be constructed as more than one element in order to improve the lateral or frontal seals. Any known mechanical or hydraulic device could also be added to the blades to ensure permanent blade-casing contact, or possibly to limit the stresses to which they are subject.

In many applications of the present invention, the blades will be used in which a nose 7 (as shown in Fig. 2) is a circumferential arc of radius D. The centre 0' of this nose describes the curve which defines the shell directrix (arc 1 to 6). Such a nose shape can be replaced by a curve 8 (as shown in Fig. 3), the polar radius of which varies as a function A(A) defined with respect to a system of axes O"(n conforming to this figure. In this case, it could be interesting to replace the definition (II) of the shell directrix by the equation z = [Rm + F,(O) - D] expj 8 + A(A) expj iu (lV) where A = IL - Z - 0.

Under these circumstances, which equally conform to the invention, the trajectory of the centre 0" of the blade nose is identical with the trajectory of the centre O' of a circular nose which would be in contact with a shell defined by equation (II).

The interest in using such a geometry for the active part of the blades rests in the possibility of controlling the conformation of the blade-casing contact to a certain extent, in conjunction with the choice of the functions F,i(B), and consequently in the improvement in the lubrication conditions of this contact.

The primary basis of the invention lies in the original geometry of the casing in accordance with the description given herein. This latter uses an algebraic definition of its directrix segmented into 2 s circumferential arcs and into 4 s connection arcs. Each of these segments performs a well defined function in the machine, and can consequently be optimised individually for satisfying this function to a maximum.

The circumferential arcs enable chambers of constant volume to be constructed, the only condition being that the distance between two successive blades is less than the angular width of these arcs. Furthermore, these latter minimise overall the accelerations which the blades undergo for a given piston displacement and rotational speed.

The arcs of maximum radius allow transfer of the fluid within the machine while preventing its compression or expansion. Those of minimum radius provide tightness between the chambers communicating with the outside.

Between two of the successive circumferential arcs there are disposed two connection arcs, the geometrical definition of which is entirely characterised by the functions Fj(fl).

The choice of these functions rests on an optimisation carried out by numerical methods with a view to satisfying precise objectives such as minimisation of blade stresses, obtaining a satisfactory conformity in their contact with the shell, defining a relationship for the variation of the chamber volumes, reducing flow pulsations etc. This type of reasoning relies not only on a knowledge of the local geometry of the curve arcs, but also on an overall knowledge thereof as provided by their algebraic formalism.

In machines known up to the present time, which use a segmented directrix definition, only a continuity of position, or possibly of the tangents, at the points connecting the various arcs making up said directrix is imposed. Such constraints are insufficient to give the machines high performance, as they do not ensure continuity of the inertia reactions. Furthermore, this continuity could be prolonged to any required extent, up to that of the curvature derivatives of any order at the connection points.

Within the scope of the first basis of the invention, the machine can be given novel possibilities by making an initial choice of the functions Fi(#), the angle of opening of the intake and discharge ports, and the number of blades. The second basis of the invention lies in determining these choices on the basis of the following proposition, namely that it is possible to ensure proportionality between the instantaneous flow rate of the fluid and the angular rotational speed of the piston by simultaneously setting the following conditions: a) the transfer of a constant volume of fluid between the intake and discharge implies that: a4 - a3a27r/ps (V) b) proportionality between the angular speed of the piston and the suction and discharge flow rates implies, in the case of infinetely thin blades, that the angular widths of the intake and discharge ports are defined respectively by: a3 - a1 and 2X/s - a4 where a3 - a1 = 2#/s - a4 = 4kar/ps (k being a positive whole number) (VI) c) compensation for the variations in flow rate due to the final width of the blades and to their radial movement implies, for all polar angles 0 where:: a1O < a1 + 2#/ps &alpha;4## < &alpha;1 + 2n/ps, that the following double relationship must be verified for m, n = 2 or 3 and 5 or 6, according to the values of the expression (S + 21 #/ps) and according to the values of a2 and a5: k-1 2k-1 # Fm(# + 21#/ps) + # Fn (# + 21#/ps) = any real constant (VII) 1=0 1=k Making another choice of the functions F,(8) and of the limits a1 of their definition intervals, by making p equal to an event number and s equal to an odd number it is possible to keep two diametrically opposing blades in the rotor at rest relative to each other, this constituting the third basis of the invention.

Relative rest between said blades implies that: &alpha;1 = &alpha;4 /X3 a2 - a1 = a5 - a4 a3 t2 = 27/5 - a5 F,(0) + F1+3 (0 + r/s) = O i = 1, 2, 3 (VIII), by using as the shell directrix the curve corresponding to equation II or IV according to the form of the blade nose.When constructing a machine according to this characteristic, the classical arrangement of the blades (as shown in Fig. 4) can be replaced by one of the arrangements shown by way of non-limiting example in Figs. 5 to 10, conforming to the first basis of the invention.

The arrangement of Fig. 5 provides for communication between two opposing slots. In this manner, a chamber is interposed between two opposing blades which has an invariable volume, thus nullifying variations in the hydraulic forces in the slots due to the sliding movement of the blades, and improving the blade-piston tightness.

Such an arrangement also enables slots to be put into communication with high pressure without exaggerated stressing, so as to facilitate machine starting, in particular when it is in the form of a drive machine.

Fig. 6 represents a modification of the preceding arrangement (a single slot for two opposing blades).

In order to reduce dynamic stresses on the blades, they could be extended such that their centre of gravity approaches the rotational axis of the piston. Such an arrangement is shown in Fig. 7. It has the additional advantage of forming an angle ( defined by the proportions of said blades.

Two opposing blades disposed in the same slot could equally be replaced by a single blade as shown in Fig. 8. Fig. 11 represents a machine constructed in accordance with this arrangement, in which the length of its blades (as shown in Figs. 12-14) is equal to 2(Rm = D), or, for a different nose geometry, to 2[R, + A(O).

In order to improve the tightness of the blades in contact with the shell, a roller could be incorporated into their tips, and which by virtue of properly chosen blade-roller contact tolerances enables the sliding of the blade nose on the casing to be replaced by a rolling action (as shown in Fig. 9). Such an operation derives from the difference between the dynamic stresses on the rollers and on the blade. Furthermore, by limiting the extent of the blade-roller contact, the roller wear is substantially reduced, and lubrication is simplified.

Alternatively, each contact could be divided into two by systematically using two blades placed side by side, one of them then providing sealing in the classical manner, and the other acting as a scraper segment (as shown in Fig. 10).

The rollers corresponding to the arrangement shown in Fig. 9 could be replaced by one or more sealing segments as shown in Figs. 1 5 and 16, in order to improve the lateral and frontal seals against the casing. These additional segments could be rigid or of limited deformation according to the possibly composite material of which they are composed (as shown in Fig. 17).

Finally, in order to reduce the blade-shell contact stress, or to prevent this contact and to provide a controlled gap in particular when using a roller or additional sealing segments, the blades can be made to slide on one or more auxiliary tracks compatible with the blade and shell geometry, as shown in Figs. 1 8 and 1 9. This sliding could be replaced by a rolling action by interposing rollers between the blades and said tracks.

When the need is felt, these different types of seals could be completed by mechanical or hydraulic arrangements for maintaining or controlling under all circumstances the contact between these elements and the casing containing them.

It is apparent that the conditions imposed on the casing geometry within this third basis of the invention are not incompatible with the second basis which gives access to proportionality between flow rate and rotational speed.

It is consequently particularly interesting to combine these two bases in order to obtain a definition for the essential elements of a machine which offers a collection of novel possibilities.

It is finally possible, within the scope of the three primary bases of the invention, to divide the machine into two portions by using an annular piston (as shown in Fig. 20), and housing inside said piston 9 a cam 10 having a geometrical definition which directly derives from that of the casing 11, and is written: z = [Rm + F1(0) - D - C expj expj O - A*(X) expj ju** In this relationship, C represents a positive quantity, and A* and ,u** are functions analogous to A and IL but the second is calculated from the function z**= [R, + Fj(O) - D - C expjA] expj B.

In this manner, two rotary pumps, one inside the other, are created between the casing 11 and piston 9 and between said piston and the cam 10, while using the same blades. These iatter have a nose form which is defined respectively by A and A*, and a common length C measured between the nose centres. The double rotary pump assembly obtained constitutes a double acting machine.

The essential interest of such a machine, which can be constructed with any order of symmetry, lies in an increase in piston displacement for unchanged outer dimensions. It should additionally be noted that the use of single blades for the two elementary rotary pumps facilitates machine starting, in particular when it produces mechanical energy.

By using a suitable intake and discharge arrangement, the two rotary pumps could be coupled in parallel (increase in flow rate) or in series (increase in the compression or expansion ratio).

It is apparent that all the special double contact blade arrangements described with respect to the third basis of the invention can in principle be used in these double acting machines, and, in particular, contact between the blades 1 to 6 and the cam 10 can be prevented.

It is equally important to note that proportionality between flow rate and rotational speed can be attained for this novel family of annular machines by choosing the functions Fj (0) and their validity ranges (a'j ~ 1alp) as previously indicated.

In certain applications, the same mechanical arrangement could be preserved while not actually adopting the internal rotary pump, in which case the cam 10 acts as a radial stop for the blades.

By providing intercommunication between the various chambers of the inner rotary pump and by adapting the intake and discharge arrangement, if is equally possible to make it act as a radial bearing, to guide the piston 9 relative to the cam 1 0.

These two special arrangements equally form part of the invention.

Any series and/or parallel association of machines wherein at least one satisfies the aforesaid descriptions also falls within the scope of the invention. Such associations can be used for operation in the form of a fluid drive or driven machine, an internal or external combustion heat engine, or for mechanical transmission.

Claims (11)

1. A volumetric bladed machine, also known as a bladed rotary pump, constructed of any known material, using any type of fluid, and operating as a drive or driven machine, comprising: - a cylindrical piston with a circular directrix comprising p slots, - a casing surrounding said piston and comprising a shell, - a set of p blades of any geometry, sliding in the piston slots and in contact with the casing in such a manner as to separate the useful volume of the rotary pump into several working chambers, said blades able to comprise auxiliary sealing elements, rollers or segments, and mechanical or hydraulic devices for improving or controlling their contact with the casing, - an admission and discharge arrangement using ports and/or controlled or automatic valves, wherein the casing comprises a shell of symmetry s, of which the cylindrical inner surface has a directrix defined by one of the two following equations: z = [Rm + Fi (8) - DJ expj a + D expj , z= [R,, + F,(8) - D] expj 8 + A(#)expj , in which the functions F,(8) are defined algebraically between the polar angles ai-1 and a1, in such a manner that said functions and said angles satisfy one of the following groups of conditions, namely: - firstly: O = a0 < a1 < a2= a3 < a4 < a5 < 2#/s F1(#) = - E - F2(a,) = F6 (2ir/s) F2(a2) = F3(a2) F5(a5) = F6(as) F4(a) = + E = F3(a3) = F5(a4), - secondly:: 0= &alpha;0 < &alpha;1 < &alpha;2=&alpha;3 < &alpha;4 < 5 = 2#/s F1(#) = - E = F2(a,) = F5(2ST/S) F4(8) = + E = F2(a3) = Fs(a4) F3(8) = F6(8) = 0, these being continuous and differentiable at least n times, - the derivatives with respect to 0, up to the order n, of F2(a1), F3(a3), F6(a4) and F6(2sr/s) being zero, whereas - the derivatives with respect to 0, up to the order n, of F2(a2) and F3(a2) are equal to each other, as are those of F5(a5) and F6(a5).

2. A machine as claimed in claim 1, wherein by also satisfying the following conditions: &alpha;4 - &alpha;3 # 2#/ps a3-a1 = 2#/s - a4 = 4k#/ps z F,, (S + 21#/ps) + z Fn (S + 217r/ps) = any real constant 1=0 1=k for &alpha;1## < &alpha;1 + 2#/ps and a4SH < a4 + 2/ps for m, n = 2 or 3 and 5 or 6 according to the values of H + 21 /ps and according to the values of a2 and a5.

3. A machine as claimed in claim 2, wherein intake and discharge are provided for by ports disposed in the casing and having angular widths of a3 - a, and 2/s - a4.

4. A machine as claimed in claims 1, 2 or 3, wherein by satisfying the following conditions: s is off, p is even a, = a4 - a3 a2 - a1 = a5 - a4 a3 - a2 = 2sT/S - a5 Fj(8) + F1 + 3(0 + n/s) = O i = 1,2, 3.

5. A machine as claimed in claim 4, wherein the piston comprises at least two opposing slots joined together to form a single slot in which two blades of any type slide.

6. A machine as claimed in claim 5, wherein at least two opposing blades are joined together to form a single blade in double contact by way of two auxiliary sealing assemblies at each of their ends.

7. A machine as claimed in any one of claims 1 to 6, wherein the piston is annular, and in cooperation with an internal cam defines a second rotary pump which uses the same blades as the first.

8. A machine as claimed in any one of claims 1 to 6, wherein the piston is annular, and houses a cam which forms a stop for the radial movment of the blades.

9. A machine as claimed in claim 8, wherein the piston and cam also form a radial bearing.

10. A machine as claimed in any one of claims 1 to 9, wherein the blades are at the most only in local contact with the casing so as to comprise at least locally a small gap between the blades and the casing, this gap being obtained by any means for guiding the blades over auxiliary tracks disposed on the side plates.

11. A volumetric bladed machine as claimed in claim 1 and substantially as herein described with reference to and as illustrated in the accompanying drawings.