WO2006043024A1

WO2006043024A1 - Rotary device

Info

Publication number: WO2006043024A1
Application number: PCT/GB2005/003857
Authority: WO
Inventors: Richard See
Original assignee: Turnstile Technology Limited
Priority date: 2004-10-21
Filing date: 2005-10-07
Publication date: 2006-04-27
Also published as: GB2419382A; GB2419382B; GB0423421D0

Abstract

Rotary devices for processing compressible fluids are disclosed, including compressors, vacuum pumps, expanders and internal combustion engines. The devices comprise first and second elements rotatable relative to each other about an axis of rotation. An elongate cavity of varying cross sectional area is defined around the axis of rotation between surfaces of the first and second elements, the first element having at least one slot formed therein at different angular positions. A cavity separating arrangement projects into the cavity in various places to separate the cavity into adjacent working portions, the volumes of which vary as the first and second elements rotate relative to each other. In various different cross sections of the cavity, dimensions of the cavity in perpendicular directions of the cavity both vary. In some devices, an aspect ratio of various different cross sections of the cavity remains within given limits. In some embodiments, cross sections of the cavity corresponding to maximum compression are circular, part-circular, tapered or square in shape.

Description

Rotary Device

This invention relates to rotary devices. In particular, this invention relates to devices for processing compressible fluids, such as rotary compressors, rotary vacuum pumps, rotary expanders and rotary internal combustion engines.

There are various known rotary compressors, expanders and engines in which an elongate cavity is formed between a shaped element and a slotted housing, and in which at least two separating elements project from at least one slot of the housing into the cavity, thereby separating the cavity into adjacent working portions in which gasses are compressed or expanded. In such known devices, the surface area of the part of each separating element that projects into the cavity varies as the compression or expansion occurs.

Examples of the known devices described above include radially sliding rotary vane compressors and engines such as those disclosed in US 5415141, axially sliding rotary vane compressors such as those disclosed in WO 9404794, the Goodyear compressors disclosed in GB 653185, and the compressors described in co-pending International patent application number PCT/GB2004/002483.

It will be noted that in some known devices, such as the Goodyear compressor, the slotted housing acts as a stator, and the shaped element is then a rotor. For example, in the Goodyear compressor, the shaped element typically takes the form of a screw. In other known devices, such as radially sliding vane compressors, the slotted housing acts as a rotor and the shaped element is then a stator. For example, in the sliding vane compressor, the shaped element is a cylindrical casing having end walls.

In the most common of the known devices, the axis of rotation of the rotor is also an axis of rotational symmetry for the slotted housing.

It will be apparent to the skilled person that the separating elements that separate the cavity into working portions may have a variety of shapes. These shapes include sliding vanes, rotating vanes and rotating toothed gear wheels. Furthermore, the motion of the separating elements relative to the slotted housing through which they project may take many forms, including reciprocating motion and rotating motion.

Typically in the known devices described above, it is important to minimise leakage of gasses that can occur between the separating element and the other components of the device, especially between the separating elements and the shaped surface. In a rotary combustion engine, it is also important to minimise the leakage of heat out of the working portions of the cavity during and after combustion. Minimising heat leakage in this way helps to ensure that fuel is burnt rapidly, thereby minimising an amount of unburned fuel remaining in exhaust gasses, and also allows an acceptable thermodynamic efficiency to be achieved.

According to the invention, there is provided a rotary device for processing compressible fluids, the device comprising: first and second elements rotatable relative to each other about an axis of rotation, an elongate cavity of varying cross sectional area being defined around the axis of rotation between surfaces of the first and second elements, the first element having at least two slots formed therein at different angular positions; and at least two separating elements projecting from respective slots of the first element into the cavity and forming respective seals with the second element, thereby separating the cavity into adjacent working portions, the volumes of the working portions varying as the first and second elements rotate relative to each other, the separating elements being movable with substantially linear sliding motion relative to the first rotation element, wherein cross sections of the cavity through the axis of rotation have a dimension perpendicular to the direction of movement of the separating elements that varies with angular position about the axis of rotation.

The invention thus concerns the dimensions and shape of the cavity formed between the first and second elements, and more particularly the dimensions and shape of cross sections of the cavity through the axis of rotation. This first aspect of the invention is intended to cover devices such as sliding vane compressors. In preferred embodiments of such devices, the second element is a fixed casing in which the first element is rotatably mounted. In known devices, the cross sectional dimensions of the cavity vary only in the direction of movement of the separating elements, as the separating elements slide in and out of the cavity. Such an arrangement leads to high gas leakage across the separating elements, particularly at positions of maximum pressure differential across the separating elements and positions where the cross section of the cavity is elongate in shape. In a compressor, these two conditions usually occur at substantially the same position, namely the position of maximum compression. Similarly, in engines, heat leakage is particularly high at positions of maximum heat differential across the elements that define the working portions.

The invention provides a device in which the cross sectional dimensions of the cavity may also vary in a direction perpendicular to the direction of movement of the separating elements, thereby allowing the cavity to be designed so that gas and/or heat leakage are minimised, i.e. by choosing appropriate cross sectional dimensions for the cavity. The invention may thus provide a device having improved efficiency compared to known devices.

The invention thus recognises that the size of the gas and/or heat leakage paths is closely related to the surface area of the cavity, and provides an arrangement by which the gas and/or heat leakage paths may be minimised.

Preferably, cross sections of the surface of at least one of the first and second elements through the axis of rotation include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements. Such an arrangement ensures that variation of the cross-sectional area of the cavity around the axis of rotation is achieved by varying the dimensions of the cavity measured parallel and perpendicular to the direction of movement of the separating elements.

The skilled person will appreciate that, because the separating elements form a seal with the second element, the shape of the first and second elements and the separating elements in various embodiments are co-dependent. For example, in some embodiments, cross sections of the surface of the second element through the axis of rotation include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements. In this case, sealing surfaces of the separating elements have cross sections that include correspondingly tapered portions.

Cross sections of the surface of the first element through the axis of rotation may also include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements. Alternatively, cross sections of the surface of the first element through the axis of rotation include linear portions, the linear portion running substantially perpendicular to the direction of movement of the separating elements.

In other embodiments, cross sections of the surface of the first element through the axis of rotation include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements, and substantially linear seals are provided between the second element and the separating elements. Such an arrangement provides simplified sealing between the second element and the separating elements.

In a particularly preferred embodiment, cross sections of the cavity through the axis of rotation that substantially correspond to maximum compression have a substantially circular shape. The cross sections thus have a maximum possible area to circumference ratio, or compactness, where it is most beneficial. Another advantageous arrangement is one in which cross sections of the cavity through the axis of rotation that substantially correspond to maximum compression have a substantially part-circular shape.

In other embodiments, cross sections of the cavity through the axis of rotation that substantially correspond to maximum compression may have a substantially square shape. Such an arrangement may assist in reducing or eliminating undesirable pulsation exhibited by the device.

Edges of the tapered portions may define an angle in the range 20° to 70°, preferably 30° to 60°, and most preferably 40° to 50° with the direction of movement of the separating elements. The edges of the tapered portions (i.e. excluding any part-circular or square portions) may define a fixed angle with the direction of movement of the separating elements. The edges of the tapered portions may alternatively define two or more fixed angles with the direction of movement of the separating elements.

The separating elements may be movable in a direction substantially perpendicular to the axis of rotation, such as in a radially sliding vane compressor. The separating elements may alternatively be movable in a substantially axial direction, such as in an axially sliding vane compressor. Other movement directions at an angle to the radial or axial direction are also possible.

Cross sections of the cavity through the axis of rotation at all angular positions may have aspect ratios in the range 0.5 to 2.0, preferably 0.67 to 1.5, and most preferably 0.83 to 1.20, although other aspect ratios are possible.

The above described principle may also be applied to devices such as the Goodyear compressors disclosed in GB 653185, and such devices are herein described as an aid to understanding the above invention. In devices such as the Goodyear compressors, the first element is preferably a casing in which the second element is rotatably mounted.

For example, a rotary device for processing compressible fluids may comprise: first and second elements rotatable relative to each other about a first axis of rotation, an elongate cavity of varying cross-sectional area being defined around the first axis of rotation between surfaces of the first and second elements, the first element having an axial slot formed therein; and a separating element rotatable about a second axis of rotation and projecting from the slot of the first element, the separating element having at least two projecting portions disposed around the second axis of rotation and projecting into the cavity, at least two projecting portions of the separating element simultaneously forming respective seals with the second element, thereby separating the cavity into adjacent working portions, the volumes of the working portions varying as the first and second elements rotate relative to each other, wherein cross sections of the cavity perpendicular to the second axis of rotation have a dimension perpendicular to a radial projecting direction of the respective projecting portion that varies with angular position about the second axis of rotation.

The cross sectional dimensions of the cavity may vary in a direction perpendicular to the radial projecting direction of a respective separating element, as well as varying in the radial projecting direction, thereby allowing the cavity to be designed so that gas and/or heat leakage are minimised, i.e. by choosing appropriate cross sectional dimensions for the cavity.

Preferably, cross sections of the surface of the second element perpendicular to the second axis of rotation include tapered portions, the tapered portions tapering in the radial projecting direction of the respective projecting portions, and a cross section of the separating element has corresponding tapered portions.

Cross sections of the cavity perpendicular to the second axis of rotation that substantially correspond to maximum compression preferably have a substantially part- circular shape or a substantially square shape.

Edges of the tapered portions may define an angle in the range 20° to 70°, preferably 30° to 60°, and most preferably 40° to 50° with the radial projecting direction of the respective projecting portions. The edges of the tapered portions preferably define one or more fixed angles with the radial projecting direction of the respective projecting portions.

All cross sections of the cavity through the first axis of rotation may have aspect ratios in the range 0.5 to 2.0, preferably 0.67 to 1.5, and most preferably 0.83 to 1.20, although other aspect ratios are possible.

The first element may have at least two axial slots formed therein, and the device may comprise at least two separating elements rotatable about respective second axes of rotation and projecting from respective slots of the first element.

There are other devices to which the above described principle may be applied. For example, a rotary device for processing compressible fluids comprises: a first element rotatable about a first axis and a casing enclosing at least a part of the first rotation element, an elongate cavity of varying cross sectional area being defined around the first axis of rotation between surfaces of the first rotation element and the casing, the casing having at least two slots formed therein at different angular positions; and at least two separating elements rotatable about respective second axes and projecting from respective slots of the casing, the separating elements projecting into the cavity and forming respective seals with the first element, thereby separating the cavity into adjacent working portions, the volumes of the working portions varying as the first element rotates, wherein cross sections of the surface of the casing through the first axis of rotation include a substantially part-circular portion.

Cross sections of the cavity through the first axis of rotation that substantially correspond to maximum compression preferably have a substantially circular or part- circular shape. By providing cross sections of the cavity that substantially correspond to maximum compression with a substantially circular or part-circular shape, a high area to circumference ratio, or compactness, is provided where it is most beneficial.

Each separating element may comprise at least two projecting portions of different radius about the respective second axis such that each projecting portion projects through the casing into the cavity by a varying amount to seal with the first element.

Alternatively, each separating element may comprise a projecting portion that projects through the casing into the cavity by a varying amount to seal with the first element, the projecting portion moving in a tangential direction with respect to the respective second axis of rotation.

The device of the invention may be a rotary compressor, rotary vacuum pump, rotary expander or rotary internal combustion engine.

It will be noted that typically, in a rotary engine of the type described herein, the cross sectional area of the channel is initially zero at the beginning of the cavity, increasing to a first local maximum, then decreasing to a local minimum, then increasing to a second local maximum, then decreasing to zero at the end of the channel. These variations correspond to the increase in the volume of the cavity during the intake cycle, the decrease during compression, the increase during expansion and the decrease during exhaust. Hereinafter, when mention is made to the position in the cavity of a combustion engine where the cross sectional area is at a minimum, this will refer to the local minimum that occurs between the two local maxima, not to the minima at either end of the cavity where the cross-sectional area is effectively zero.

Those skilled in the art will recognise that heat-leakage and gas-leakage are not the only variables to be optimised in the design of a rotary device for processing compressible fluids. Consideration must also be given to other factors such as friction, stresses on materials, noisy pulsation in the gas flow, the creation of quench zones in an engine, and the overall size of the device. The shape of the cavity can of course be modified to take these factors into account.

Embodiments of the invention will now be described, by way of example only, with reference to the following drawings, in which:

Figures 1 and 2 show different cross sections of a first known radially sliding vane compressor; Figure 3 shows a cross section of a first known radially sliding vane internal combustion engine;

Figure 4 shows a sliding vane, or separating element, of a first device according to the invention;

Figures 5 and 6 show different cross sections of the first device according to the invention;

Figure 7 shows a different, partial cross section of the first device according to the invention;

Figure 8 shows a partial cross section of a second device according to the invention; Figure 9 shows a partial cross section of a third device according to the invention;

Figure 10 shows a partial cross section of a fourth device according to the invention; Figure 11 shows a partial cross section of a fifth device according to the invention;

Figure 12 shows a partial cross section of a sixth device according to the invention; Figure 13 shows a partial cross section of a seventh device according to the invention;

Figure 14 shows a cross section of a second known radially sliding vane compressor;

Figure 15 shows a cross section of a second known radially sliding vane internal combustion engine;

Figure 16 shows a sliding vane, or separating element, of a ninth device according to the invention;

Figure 17 shows a sliding vane, or separating element, of a tenth device according to the invention; Figure 18 shows a partial cross section of a third known rotary internal combustion engine; and

Figures 19 to 22 are views of other device used to explain the invention.

It should be noted that all of the Figures are schematic and therefore are not to scale. For example, certain dimensions may have been exaggerated in the interests of clarity. Specific mechanisms such as drive systems, lubrication systems and the positioning of intakes and exhausts will be known to the skilled person, and are thus omitted from the Figures for the sake of simplicity and claπty.

Manufacture and assembly of the devices is not shown or described, since conventional techniques known to the skilled person may be used. It will be apparent to the skilled person that some elements that are shown in the Figures as a single component are best manufactured in two or more parts, and then assembled.

Figures 1 and 2 show cross sections of a known radially sliding vane compressor 1 in planes perpendicular to and through an axis of rotation respectively. The compressor 1 comprises a first element 3 that is rotatably mounted in a second stationary element 5. The first element 3 takes the form of a cylinder having radial slots 7 formed therein. The second element 5 takes the form of a casing having a shaped surface that houses at least a part of the first element 3. The axes of the first and second elements are parallel but displaced from each other. A cavity 9 of varying cross sectional area is defined between the surface of the cylinder and the shaped surface of the casing.

The slots 7 of the first element 3 each accommodate a separating element 11. The separating elements 11 take the form of rectangular vanes that are slidable in a radial direction. The rectangular vanes project into the cavity 9 and form a seal with the first element 3, thereby separating the cavity 9 into working portions. During operation, the first element 3 rotates about its axis, and the rectangular vanes follow a reciprocating sliding motion relative to the first element 3, which motion maintains the seal with the first element 3. The volumes of the working portions vary with rotation of the first element 3, allowing gasses trapped within the working portions to be compressed.

It will be noted from Figure 2 that, although the cross-sectional area of the cavity 9 varies significantly about the axis of rotation, the circumferential length of the cross sections of the cavity 9 exhibits considerably less variation.

Figure 3 shows a cross section of a known radially sliding vane internal combustion engine 13. The construction of the engine 13 is substantially the same as that of the compressor shown in Figures 1 and 2, except that there is an expansion phase in addition to the compression phase. The engine 13 has equal compression and expansion ratios, although there are well-known engines of a similar construction in which these ratios are different.

It will be noted from Figures 1 and 3 that the same first element and separating elements may be used in compressors and engines. It is the design of the second element that determines whether the device operates as a compressor or an engine.

Figure 4 shows one of the sliding vanes used as separating elements 111 in a first device 101 according to the invention, and Figures 5 to 7 show different cross sections of the first device 101. The first device 101 is a rotary internal combustion engine. The construction of the first device 101 is similar to that of the known devices shown in Figures 1 to 3, and comprises a first element 103 that is rotatably mounted in a second stationary element 105.

The first element 103 takes the form of a block of material having radial slots formed therein. The second element 105 takes the form of a casing having a shaped surface that houses at least a part of the first element 103. A cavity 109 of varying cross sectional area is defined between the surface of the block of material and the shaped surface of the casing.

The slots 107 of the first element 103 each accommodate a separating element 111. The separating elements 111 take the form of shaped vanes that are slidable in a radial direction. The separating elements project into the cavity 109 and form a seal with the first element 103, thereby separating the cavity 109 into working portions. In use, the first element 103 rotates about its axis, and the separating elements follow a reciprocating sliding motion relative to the first element 103, which motion maintains a seal with the first element 103. The volumes of the working portions vary with rotation of the first element 103, allowing gasses trapped within the working portions to be compressed and expanded.

The first device 101 differs from the known devices shown in Figures 1 to 3 in that the separating elements 111 used in the first device 101 are not rectangular, as shown in Figure 4. Instead, the vanes each include a tapered portion 113, the tapered portion 1 13 tapering in a direction of movement of the separating elements 111, i.e. radially. The direction of movement of the vane shown in Figure 4 is indicated by arrows 117. The sealing surfaces of each vane define angles of 60° with the direction of movement of the respective separating element 111. In addition to the tapered portion 113, a tip 115 of each separating element 111 is substantially semicircular. This part of the separating element 111 is the only part that is in contact with the second element 105 where the cross sectional area of the cavity is at a minimum, i.e. at maximum compression. The diameter of the semicircle is significantly less than the maximum width of the separating elements 111. This allows the sealing length of each separating element 111 in contact with the second element 105 when there is a large pressure difference across the separating element 111, i.e. at maximum compression, to be significantly less than the sealing length of the separating element 111 in contact with the second element 105 when there is a small pressure difference across the separating element 111.

Figures 5 to 7 show different cross sections of the first device through the axis of rotation 119. The surface of the first element 103 is essentially a body of rotation having slots formed therein. The first element 103 is mounted to rotate about the axis of rotation 119.

The surface of the second element 105 is derived from the shape of the separating elements 111. In particular, the surface of the second element 105 is shaped to provide a cavity 109 having a varying cross sectional area. This varying cross sectional area can be seen in the different cross sections of Figures 5 to 7. However, the surface of the second element 105 is also shaped so that it forms a seal between adjacent working portions of the cavity 109.

Thus, the cross section of the second element 105 through the axis of rotation 119 comprises a semicircular portion 121 that corresponds to, and forms a seal with the semicircular tip of the separating elements 111. Cross sections of the surface of the second element 105, apart from in those positions where the cross sectional area of the cavity 109 is smallest, also include a tapered portion 123 that corresponds to, and forms a seal with, the tapered portion 113 of the separating elements 111.

It can be seen from Figures 5 to 7 that, as the cross sectional area of the cavity 109 varies, the length of the seal between the second element 105 and the separating elements 111 varies substantially.

In the first device 101 , the cross section of the surface of the first element 103 is shaped to be a mirror image of the shape of the separating elements 111. In use, as the first element 103 rotates about the axis of rotation 119, the dimensions of the cavity 109 vary in both a direction of movement of the separating elements 111, i.e. radially, and a direction perpendicular to the direction of movement of the separating elements 111, i.e. axially with respect to the rotation axis. In Figure 5, the dimensions of the cavity 109 in the direction of movement of the separating element 111 and the direction perpendicular to the direction of movement of the separating elements 111 are indicated by dimensioning arrow 125 and dimensioning arrow 127 respectively.

The semi-circular shape of the surfaces ensures that the cross section of the cavity 109 is circular in shape at the position where a pressure differential in the device is greatest, i.e. maximum compression, or minimum cross sectional area. This is shown in the upper half of Figure 6. A circular cross section minimises the opportunity for gas leakage past the separating elements 111, since a sealing length is minimised, and also for heat leakage through the elements that enclose the gas, since a surface area is minimised.

The separating elements 11 1 are fully withdrawn into the first element 103 at the position when the entire length of the surfaces of the first and second elements 103, 105 are in contact, as shown in the lower half of Figure 6.

Figure 7 illustrates how, at a position of the cavity 109 where the cavity 109 has an intermediate cross sectional area, the cavity has intermediate dimensions in both the direction of movement of the separating elements 111 and the direction perpendicular to the direction of movement of the separating elements 111.

It will be apparent to the skilled person that the known rotary internal combustion engines have quench zones in the cavity 9 where the cross sectional area of the cavity 9 is slightly larger than its minimum cross sectional area. Quench zones are regions of the cavity 9 that are defined, or enclosed, by a large surfaces area, the large surface area causing localised cooling.

Quench zones are present in the first device 101, but in alternative embodiments, the shape of the first and second elements may be designed so that quench zones only exist after substantial expansion has occurred. Such an arrangement is shown in Figure 8, which shows a second device 129 according to the invention.

In the second device 129 shown in Figure 8, the edges of the tapered portions define two fixed angles with the direction of movement of the separating elements 111. A first smaller angle in a first region 131 provides for a relatively constant aspect ratio of the cavity cross section during initial expansion. A second larger angle in a second region 133 provides for a more dynamic aspect ratio after initial expansion, and thus provides quench zones 135.

In the first device 101 according to the invention, the first element 103 has a complex shape, i.e. non-cylindrical, which leads to increased manufacturing costs. In a third device 137 according to the invention, as shown in Figure 9, the first element 139 is cylindrical, as in the known devices shown in Figures 1 to 3. However, the third device 137 has a second element 141 and separating elements that are similar to those of the first device 101 according to the invention.

It is apparent from Figure 9 that when the cross sectional area of the channel 143 is at a minimum, the cross section of the channel 143 will be substantially semicircular in shape. The third device 137 thus still benefits from a reduced leakage path as pressure increases, but with reduced manufacturing complexity.

Figure 10 illustrates a fourth device 145 according to the invention. The fourth device 145 is similar to the third device 137 shown in Figure 9. However, the cross section of the cavity at the position of the channel with minimum cross sectional area is no longer semicircular, but is a larger part of a circle 147. Such an arrangement provides reduced gas and heat leakage compared to the third device 137. The design of the surface of the second element 149 and the separating elements is altered to provide the new part- circular shape.

A fifth device 151 according to the invention is shown in Figure 11. The fifth engine 151 has separating elements that are rectangular in shape, as in the known devices shown in Figures 1 to 3. The fifth device 151 has a first element 153 having a similar design to that of the first device 101. Specifically, the surface of the first element 153 is a body of rotation and thus has a fixed cross sectional shape. The second element 155 of the fifth device 151 has a varying cross sectional shape, but the part of the surface of the second element 155 that defines the cavity 157 has a linear cross section, so as to seal with the rectangular separating elements.

The fifth device 151 provides a similar gas and heat leakage characteristics to the third device 137. However, the fifth device 151 advantageously provides a linear seal between the separating elements and the second element 155. This device is thus particularly suitable for use when it is desired to have a seal exhibiting rolling motion between the separating elements and the second element, as is described, for example, in WO 9404794 and GB 344118.

It will be understood by the skilled person, and with reference to Figures 1 and 3, that the separating elements and first elements of the first to fifth devices may also be used to provide compressors simply by designing a motion for the separating elements similar to that of the compressor illustrated in Figure 1, and then designing the second element to provide the motion of the separating elements. Such compressors would exhibit the same benefits of a reduced leakage path as the engines that are described above with reference to Figures 4 to 11.

For compressors, it is often desirable to reduce the pulsation of the air flow as it exits the compressor, in order to reduce the noise generated by the compressor. Figure 12 shows a sixth device 159 according to the invention, which device is a compressor having reduced pulsation. The compressor has a similar design to that described above. However, the circular or semicircular portion of the cross section of the channel 161 at a position of maximum compression may be substituted by a rectangular, or square portion 163. It will be understood that this substitution affects the shape of the channel 161 along its entire length, since the rectangular portion 163 defines a part of the cavity 161 along its entire length.

The devices 151, 159 shown in Figures 11 and 12 have a further benefit compared to known devices in that there no seal is necessary between the separating elements and the end walls 152, 165 of the second element 155, 167. Instead, the seal is formed between the separating elements and the first element 153, 169. A still further benefit is that the separating elements of the fifth and sixth devices 151, 159 are well supported on either side by the first element 153, 169, thereby enabling a larger separating element to be used than in the prior art, in which the majority of the separating element must remain within the first element. This allows a device to have a larger swept volume for a given set of external dimensions. These benefits are present in a seventh device 171 according to the invention, which is shown in Figure 13. In this device, leakage path reduction is less than that in the sixth device 159 shown in Figure 12, but the device 171 has a larger swept volume.

All of the above devices according to the invention are engines or compressors, and it has been stated that they are all adaptable as either engines or compressors. The devices are also adaptable as expanders. The skilled person will understand that the above described compressors may operate as expanders simply by running them in reverse.

It is known that planes defined by the separating elements of rotary devices do not have to pass through the axis of rotation of the first element. Figures 14 and 15 show a known compressor 179 and a known engine 181 having such an arrangement. It will be apparent to the skilled person that the present invention is applicable to, and includes, such arrangements.

Figure 16 shows a separating element 183 used in a ninth device according to the invention. The separating elements 183 of the ninth device are aligned in planes parallel to the axis of rotation, as shown in Figures 14 and 15. It will be noted that the tip 185 of the separating element 183 in Figure 16 is substantially elliptical. This configuration allows the cavity to have a substantially circular cross section at the position of minimum cross-sectional area.

Other arrangements within the scope of the invention are devices having sliding separating elements that each have an arcuate cross section perpendicular to the axis of rotation, and in which each separating element move with arcuate sliding motion. Such devices will be known to the' skilled person.

Although the devices described above have all been radially sliding vane compressors, engines and expanders, it will be apparent to the skilled person that the invention is applicable to other types of devices. For example, the invention includes devices having axially sliding vanes, which require simple modification of the devices described above.

Figure 17 shows a separating element 187 for use in a tenth device according to the invention. The device is an axially sliding vane engine of the type disclosed in WO 9404794. Such a device has one first element rotatably mounted about an axis of rotation. Two second elements are provided on either side of the first element in the axial direction. Elongate cavities are defined between an end walls of the first element and one second element, and the other end wall of the first element and the other second element, respectively. The cavities are thus axially offset from each other. The separating elements 187 are disposed in slots in the first element, and opposite ends of the separating elements 187 project into respective ones of the two cavities.

The edges of the separating element 187 define angles of 45° with its direction of movement, which direction is indicated by arrows 189, thereby avoiding the creation of quench zones. The design of the first and second elements will be apparent to the skilled person.

Figures 18 to 22 will now be described in order to provide a fuller understanding of the principle of the invention.

Figure 18 shows a known Goodyear engine 191. The engine comprises a first element 193, a second element 195 and a separating element 197. The first element 193, only a part of which is shown, is a casing. The second element 195 is a block of material rotatable within the casing 193 about a first axis of rotation 199 and having a groove formed therein. The groove extends around the block of material 195 in a similar manner to a screw thread. The depth of the groove varies along its length. An elongate cavity is defined by the groove between the first and second elements 193, 195.

The separating element 197 is a gear wheel rotatable about a second axis 201 and having a plurality of substantially rectangular projecting portions 203. The projecting portions 203 of the separating element 197 project through an axial slot formed in the first element 193 and mesh with the groove formed in the second element 195. The meshing projecting portions 203 form seals with the second element 195, thereby separating the cavity into adjacent working portions, the volumes of which vary as the second element 195 and the separating element 197 rotate about their respective axes.

Figure 19 shows another Goodyear device 205 that operates according to the same principle as that of the devices according to the invention that have been described above. The construction of the device 205 is similar to that of the device 191 shown in Figure 18. However, the projecting portions 209 of the separating element 207 have a similar shape to the separating elements 111 of the first device 101 according to the invention shown in Figures 4 to 7. In particular, the projecting portions 209 are tapered in their respective radial projecting directions. In this way, the cross sectional area of the cavity may be varied while maintaining a relatively constant aspect ratio of the cavity.

The projecting portions 209 also have a semicircular tip 210. This ensures that cross sections of the cavity are substantially semicircular at positions where it has minimum cross sectional area. Thus, at positions of minimum cross sectional area, where there is likely to be a large pressure differential across the projecting portions 209, the gas/heat leakage path is minimised.

The skilled person will appreciate that, in a Goodyear engine, the design of the cross section of the cavity is dependent on the design of the projecting portions of the separating element and the design of the second element. The design of the first element determines the compression and expansion ratios. Figures 20 and 21 show another device 211, which device is a rotary oscillating vane engine of the type disclosed in US 4653446. The device comprises a first element 213, a second element 215 and a plurality of separating elements 217. The first element 213 is a casing. The second element 215 is a block of material rotatable within the casing 213 about a first axis of rotation 219. An elongate cavity is defined around the first axis of rotation between surfaces of the first and second elements 213, 215.

Separating elements 217 are located at different angular positions around the first axis of rotation 219. The separating elements 217 are pivotally mounted about respective second axes of rotation 221. Each separating element 217 has a projecting portions 223 extending in a tangential direction with respect to a respective second axis of rotation 221. The projecting portion 223 of each separating element 217 projects through a respective axial slot formed in the first element 213 and forms a seal with the second element 215, thereby separating the cavity into adjacent working portions. The volumes of the working portions of the cavity vary as the second element 215 rotates and the separating elements 217 pivot about their respective axes.

It can be seen in Figure 21 that the projecting portions 223 of the separating element 217 have a similar shape to the separating elements 111 of the first device 101 according to the invention shown in Figures 4 to 7. In particular, the projecting portions 223 are tapered in their tangential projecting directions. In this way, the cross sectional area of the cavity may be varied while maintaining a relatively constant aspect ratio of the cavity. The projecting portions 223 have a semicircular tip, and cross sections of the surface of the first element 213 and second element 215 have shapes that include semicircular portions. This ensures that cross sections of the cavity are substantially circular at positions where the cavity has minimum cross sectional area. Thus, at positions of minimum cross sectional area, where there is likely to be a large pressure differential across the projecting portions 223, the gas/heat leakage path is minimised.

The skilled person will understand that, although US 4653446 describes how a gap may be left between the separating elements and the shaped surface, to allow combustion to propagate past the separating elements, a similar engine might nevertheless be constructed without the gap. Furthermore, in engines where a gap is present, this invention allows minimal heat leakage and still reduces the pressure leakage that occurs.

Figure 22 shows another device 225 according to the invention, which device is a rotary vane engine of the type disclosed in International patent application number PCT/GB2004/002483. The device 225 is similar to the previous device 211 and comprises a first element 227, a second element 229 and a plurality of separating elements 231. The first element 227 is a casing. The second element 229 is a block of material rotatable within the casing 227 about a first axis of rotation 233. An elongate cavity is defined around the first axis of rotation 233 between surfaces of the first and second elements 227, 229.

Separating elements 231 are located at different angular positions around the first axis of rotation 233. The separating elements 231 are rotatably mounted about respective second axes of rotation 237. Each separating element 231 has a number of projecting portions 235 extending in a radial direction with respect to a respective second axis of rotation 237. Each projecting portion 235 has a different radius. The projecting portions 235 of each separating element 231 project through a respective axial slot formed in the first element 227 by varying amounts to form seals with the second element 229, thereby separating the cavity into adjacent working portions. The volumes of the working portions of the cavity vary as the second element 229 and the separating elements 231 rotate about their respective axes.

It can be seen in Figure 22 that the cross section of the surface of the first element 227 has a shape that includes semicircular portion. This ensures that cross sections of the cavity are substantially semicircular at positions where it has minimum cross sectional area. Thus, at positions of minimum cross sectional area, where there is likely to be a large pressure differential across the projecting portions 235, the gas/heat leakage path is minimised.

The above embodiments of the invention described with reference the drawings are purely preferred embodiments, and are described by way of example only. It will be apparent to the skilled person that many other embodiments fall within the scope of the invention, as defined by the claims.

Claims

CLAIMS:

1. A rotary device for processing compressible fluids, the device comprising: first and second elements rotatable relative to each other about an axis of rotation, an elongate cavity of varying cross sectional area being defined around the axis of rotation between surfaces of the first and second elements, the first element having at least two slots formed therein at different angular positions; and at least two separating elements projecting from respective slots of the first element into the cavity and forming respective seals with the second element, thereby separating the cavity into adjacent working portions, the volumes of the working portions varying as the first and second elements rotate relative to each other, the separating elements being movable with substantially linear sliding motion relative to the first rotation element, wherein cross sections of the cavity through the axis of rotation have a dimension perpendicular to the direction of movement of the separating elements that varies with angular position about the axis of rotation.

2. The device of claim 1, wherein the second element is a casing in which the first element is rotatably mounted.

3. The device of claim 1 or 2, wherein cross sections of the surface of at least one of the first and second elements through the axis of rotation include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements.

4. The device of claim 3, wherein cross sections of the surface of the second element through the axis of rotation include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements, and wherein sealing surfaces of the separating elements have cross sections that include correspondingly tapered portions.

5. The device of claim 4, wherein cross sections of the surface of the first element through the axis of rotation also include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements.

6. The device of claim 4, wherein cross sections of the surface of the first element through the axis of rotation include linear portions, the linear portion running substantially perpendicular to the direction of movement of the separating elements.

7. The device of claim 3, wherein cross sections of the surface of the first element through the axis of rotation include a tapered portion, the tapered portion tapering in the direction of movement of the separating elements, and wherein substantially linear seals are provided between the second element and the separating elements. ,

8. The device of any one of claims 1 to 5, wherein cross sections of the cavity through the axis of rotation that substantially correspond to maximum compression have a substantially circular shape.

9. The device of any one of claims 1 to 7, wherein cross sections of the cavity through the axis of rotation that substantially correspond to maximum compression have a substantially part-circular shape.

10. The device of any one of claims 1 to 7, wherein cross sections of the cavity through the axis of rotation that substantially correspond to maximum compression have a substantially square shape.

11. The device of any one of claims 3 to 10 when dependent on claim 3, wherein edges of the tapered portions define an angle in the range 20° to 70° with the direction of movement of the separating elements.

12. The device of claim 11, wherein the edges of the tapered portions define a fixed angle with the direction of movement of the separating elements.

13. The device of claim 11, wherein the edges of the tapered portions define two or more fixed angles with the direction of movement of the separating elements.

14. The device of any preceding claim, wherein the separating elements are movable in a direction substantially perpendicular to the axis of rotation.

15. The device of claim 14, wherein the separating elements are movable in a substantially radial direction.

16. The device of any one of claims 1 to 13, wherein the separating elements are movable in a substantially axial direction.

17. The device of any preceding claim, wherein cross sections of the cavity through the axis of rotation at all angular positions have aspect ratios in the range 0.5 to 2.0.

18. The device of any preceding claim, wherein the device is a rotary compressor.

19. The device of any one of claims 1 to 17, wherein the device is a rotary vacuum pump.

20. The device of any one of claims 1 to 17, wherein the device is a rotary expander. -

21. The device of any one of claims 1 to 17, wherein the device is a rotary internal combustion engine.