Rotary Motor with Integral Fluid Seal

The present disclosure is generally in the field of apparatuses that can compress a fluid or utilize a compressed fluid to generate power. Such apparatuses include compressors, pumps, expanders, or engines. More specifically, this disclosure concerns such apparatuses that employ a rotating displacement-mechanism, like positive displacement compressors, pumps, expanders, and positive-replacement engines.

References considered to be relevant as background to the presently disclosed subject matter are listed below:

Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

Rotating mechanism are well known in the art for compressing or expanding a fluid. These involve a main rotor with a plurality of projections that rotate in an annular space formed between opposite surfaces of the rotor and the stator (this rotor is referred to herein, also, as “male rotor”). In such rotatory mechanism these projections that closely engage the opposite stator surfaces of the annular space, define, with reciprocating or rotary elements that are fixed in the stator and fit into the annular space and closely engage it, dynamic chambers that change in volume as these projections approach to or recede from such fixed elements. Apparatuses that embody such a mechanism is disclosed in U.S. Pat. Nos. 4,890,990 and 9,638,035.

One of the challenges in such rotary-mechanisms is to adequately seal the annular space and avoid leakage of compressed fluid through the small clearance between the rotating elements (to be referred to herein, at times, as “fluid leakage path”) and the surroundings of the apparatus. This is particularly acute where, in addition to a main rotor, the elements that are fixed in the stator and fit into the annular space and closely engage it are rotating elements that rotate in tandem with the main rotor (often referred in the art as “female rotor(s)”).

A solution to this problem is taught by U.S. Pat. No. 4,890,990 through a paraboloid-like cross-sectional shape of the annular space. The difference in the radial and axial expansion of the different elements upon heating is balanced and compensated by the angle of the side walls, which have the same or similar ratio, thus maintaining mostly an even gap of the leakage path formed between the male rotor and the stator. This notwithstanding, the walls of the fluid leakage path between the male rotor and the stator will nonetheless expand differently and thus it is practically impossible to completely seal the fluid leakage path, especially at sharp corners, where the radial and axial expansions are different.

Additionally, as noted above, it is particularly difficult to seal fluid leakage path occurring at the intersection of the male and female rotors, where the fluid leakage path between the male rotor and the stator is interrupted giving rise to a fluid leakage path that is formed between the male rotor and the female rotor that bifurcates into two fluid paths, extending in different directions, one formed between the male rotor and the stator and the other between the female rotor and the stator. As the intersection of the rotors is between versions of a similar hyperboloid geometry, however with different axes and diameters, there are sharp edges between different leakage paths at the intersection which may increase leakage. This problem is compounded by the fact that such sharp edges at such intersection cannot practically be produced, which means that they will be rounded, increasing the gap of the leakage channels at such point and potentially increasing fluid leakage.

The present disclosure concerns an apparatus with a rotary mechanism where two main rotating parts are rotating relatively to each other around the same, main axis of the apparatus—one may be a rotor and the other may be a stator, and form together a radially and axially confined annular space between them, confined in both circumferential and axial directions (to be referred to herein as “confined annular space”). There is at least one a projecting element that extends from one of the parts into the confined annular space and closely engages the walls of said space, and at least one additional rotor (referred to herein as “auxiliary rotor”) rotating about a different axis (referred to herein as “auxiliary axis”), typically parallel to the main axis, that is disposed in one of the two parts and rotates in synchrony with the main rotating part. The auxiliary rotor, which is an axially symmetric element, has a portion that abuts into the confined annular space (that may be referred to herein as “abutting portion”), that closely engage the walls of said space. The term “closely engage” denotes an engages that substantially minimizes or even essentially avoid flow of fluid therethrough. The at least one projecting element and with the at least one abutting portion define between them at least one annular chamber that continuously changes in its length in consequence of the rotation—contracting when the projecting element advances in its rotation towards the abutting portion and expands when the projecting element recedes in its rotation away from the abutting portion.

In order to permit rotation, there needs to be minimal clearance between rotating parts and other rotating or static parts, taking into consideration also expansion and contraction that inevitably occurs upon respective increase or decrease in temperature during operation. This minimal clearance leads to gaps that create paths that enable leakage and losses of fluid within the annular chambers (such path(s) to be referred to herein as “leakage path(s)”), especially when such chambers contain highly pressurized fluid. The leakage path extends from within the confined annular space to the apparatus' periphery along the surfaces of the rotating elements in the apparatus in a general axial direction.

The present disclosure provides sealing solutions for such apparatuses.

The disclosure herein concerns such an apparatus with a unique sealing arrangement.

The apparatus of this disclosure may be configured to operate as one or more of a compressor, pump, or an expander.

The current disclosure provides an apparatus for rotary compression or expansion of a fluid with a unique sealing mechanism that functions to substantially seal a confined annular space in which the fluid is compressed or expanded.

Between any two elements that rotate one versus the other and operate in fluid compression or expansion, there are fluid leakage paths formed between a rotating element and congruent faces of another element of the apparatus, and consequently the working fluid (namely the fluid the undergoes compression or expansion) may leak therethrough, hampering the operation efficiency, as noted above. The present disclosure provides configurations of the fluid leakage paths to minimize or at times practically avoid leakage of fluid through the fluid leakage paths. Provided by the present disclosure is also an apparatus implementing such configurations of the fluid leakage paths, in which such fluid leakage is impeded or even substantially avoided, namely is avoided to a great or significant extent.

There are several embodiments that are described herein identified by their serial number according to the order as they are described, as “embodiment (1)”, “embodiment (2)”, etc. Each of these embodiments may be implemented in a variety of different ways which may be referred to also by the term “embodiment”; for example, “by one embodiment of embodiment (1) . . . ”; etc. It should be noted that these embodiments may be used individually or in any combination in an apparatus that is used in accordance with the teaching of this disclosure.

When referring to the leakage paths according to the different embodiment of the scaling arrangements, the term “proximal” and “distal” may be used to denote relative position of such sections with respect to the confined annular space and the flow path of the leaking fluid along the path. In other words, the leakage path extends from within the confined annular space in the general proximal-to-distal direction, with distal sections of the leakage path being further removed along the leakage path as compared to proximal sections; and the leaking fluid flows along the leakage path in the general proximal-to-distal direction. A flow in the proximal-to-distal direction may be referred to herein as “forward flow” and a flow in the opposite direction may be referred to as “counter flow”.

The Apparatus of this disclosure embodies a sealing solution that is based on the physical configuration of the leakage path and various of its features to substantially inhibit flow of fluid through the leakage path, with minimal leakage. The term “active sealing” denotes that the scaling is active once the apparatus is in operation and is a consequence of the flow of leaking fluid through the leakage path. The active sealing is embodied in one or more of: (i) a first, proximal section of the leakage path that extends over circumferential side walls of the confined annular space that are defined by the rotor (embodiment (1)); (ii) provision of interrupted leakage paths where a leakage path branches into differently directed paths (embodiment (2)) with optional rotary projections extending from the main and/or the auxiliary rotor that are applicable, in particular in the interrupted leakage paths configuration. The active sealing may also be supplemented by passive sealing elements known per se, such as a rotary sealing. This is particularly enabled by an embodiment of embodiment (2). The embodiments may be combined with each one providing an additional sealing effect to one or more others.

Some additional terms used herein and their meanings, include:

Other terms that are used herein will be understood from their context.

By embodiment (1) of this disclosure, the confined annular space has side walls that are defined by circumferential radially extending projections that have each an arcuated surface defining, jointly with congruent faces of the rotor a first section of a fluid leakage path that extends in a general axial direction over the arcuated surface into other sections of the fluid leakage path. The centrifugal forces that act on the leaking fluid, cause droplets, mist or other particles that are dispersed in the fluid to accumulate in the apex region of the arcuated surface and the formation of a film at that region. The film has a sealing effect hindering, once formed, leakage of fluid through this section and, hence, having an effect of at least partially sealing the confined annular space.

By embodiment (2) the main rotor and the auxiliary rotor are configured such that their intersection with one another creates a branching out of the fluid flow path in the forward flow direction. The branching is into two distal sections: one directed in the general axial direction along auxiliary rotor-associated leakage paths and the other in a general radial direction along a generally radially extending section of the second part-associated leakage path or the main rotor-associated leakage path defined below. This may induce: several active sealing effects, among these backing up of leakage losses through oscillations in consequence of the cyclical change of pressure in all angular sections of the confined annular space which means; and increase in the flow time of the fluid such that the time it takes for the fluid to flow through the distal sections of the leakage paths is less than the change of pressure within an angular section of the confined annular space, and, thus, forward flowing fluid will counterflow as a result of pressure reduction in the associated angular section before traversing the entire leakage path.

Such branching, also yields two distinct leakage path that permit to add additional leakage preventing features to each of the branched. For one, as will be described below, it permits also to form the rotors with one or more circumferential radial projections, each with an arcuated rim, defining a tortuous fluid leakage path with two generally radial sections extending about the rim of the projection. Similarly as in embodiment (1) the centrifugal forces that act on the leaking fluid, will cause droplets, mist or other particles that are dispersed in the fluid to accumulate at the rim region and the formation of a film at that region. The film at has a sealing effect hindering, once formed, leakage of fluid therethrough. Additionally, this clear segregation of the leakage paths, permit to fit rotary seals at the end of such paths.

It was also realized in accordance with another embodiment of this disclosure, to be referred to as embodiment (3), that in order to avoid significant changes in the width of the gap between the congruent surfaces of the generally radial sections, in view of the difference between radial and axial heat-induced expansion of the confined annular chamber and other parts of the apparatus, the generally radially extending sections should be angled such that the change of width will be within ±25% tolerance over the range of operating temperatures of the apparatus. Namely, the generally radial sections should be angled with respect to the axis such that given the difference in radial to axial expansion there will only minor changes in the gap between the congruent faces of such sections. To achieve that these generally radial sections may have an angle of about 80-81° vis-à-vis the axis, typically about 81°. Such sections include, for example, the generally radially extending section that extends from the intersection of embodiment (2) or the generally radial sections defined by the circumferential radial projections of embodiment (2).

Provided by this disclosure is, thus, an apparatus that comprises a first part and a second part, one or both rotatable against one another about a main axis, defining axial direction (a direction parallel to the axis) and a radial direction (a direction normal to the axis). There are one or more auxiliary rotors that are fitted in said first part and rotatable about auxiliary axes parallel to said main axis. The apparatus may comprise two or more (e.g. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or even more) auxiliary rotors. The auxiliary rotors are fitted in said first part and are rotatable about auxiliary axes parallel to said main axis. The rotations of the rotatable elements are synchronized and function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts. There are fluid leakage paths that are formed between congruent opposite faces formed between each two of the first part, the auxiliary rotor, and the second part. Each fluid leakage path is configured with an active sealing element obstructing flow of fluid through said path upon rotation, the active sealing element comprises one or both of the following (1) and (2):

Also provided by this disclosure is, an apparatus that comprises a first part and a second part, one or both rotatable against one another about a main axis, defining axial and radial direction. There are one or more auxiliary rotors that are fitted in said first part and rotatable about auxiliary axes parallel to said main axis. The rotations are synchronized and function jointly to compress, expand or pump a fluid within a confined annular space formed between the first and second parts. There are fluid leakage paths that are formed between congruent opposite faces between each two of the first part, the auxiliary rotor, and the second part. The fluid leakage path having a section that has a generally radial trajectory, angled at about 80-81°, typically 81, with respect to the axis.

Embodiments of this disclosure will now be described with reference to two set of embodiments: one set under the heading of “general aspect” and the other under the heading of “specific aspect”, both concerning apparatuses of this disclosure. The term “aspect” is used only from linguistic convenience and has no connotation beyond that. Embodiments described in connection with the general aspect applies also to the specific aspect, at time while making necessary alterations; and vice versa.

The apparatus, of the general aspect of this disclosure, comprises a first part and a second part, one or both rotating against one another about a main axis that defines axial directions (a direction parallel to the axis) and a radial direction (a direction normal to the axis). The first part may be a stator and the second part may be a rotor. The apparatus also comprises two or more (e.g. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or even more) additional rotors, defined herein as “auxiliary rotor(s)”. The auxiliary rotors are fitted in said first part and are rotating about auxiliary axes parallel to said main axis. The rotations of the elements function to jointly compress, expand or pump a fluid within a confined annular space defined between the first and second parts at a radial engagement sector about the second part. The two or more auxiliary rotors engage the second part.

There are fluid leakage paths that are defined between congruent opposite faces between each two of the first part, the auxiliary rotor and the second part. The fluid leakage paths each comprise one or more sections extending over an apex of a circumferential radially rotating projection.

According to embodiment (1) of this general aspect, said confined annular space has two circumferential side walls extending from said second part with an arcuated peripheral surface and said fluid leakage path has a proximal section of the leakage path that extends from within the confined annular space and is formed between the arcuated peripheral surface and congruent surface of the first part.

According to embodiment (2) of this general aspect, the fluid leakage path is configured with an interrupted leakage path in which a proximal section of the fluid leakage path extending from within the confined annular space is branching into two distal sections including (i) one or more auxiliary rotor-associated leakage paths, each extending in a general axial direction and formed between one of the auxiliary rotors and congruent surfaces of the first part, and (ii) a generally radially extending section of a second part-associated leakage path formed between a member of said second part and congruent surfaces of said first part.

According to embodiment (3) of this general aspect, the fluid leakage path comprises one or more sections that extend in the general radial direction and has a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between congruent surface of said section. Said trajectory may be angled at about 80-81° with respect to the axis, typically about 81°.

The generally arcuated surface may have a semi-circular cross-section, may have a cross section defining part of an ellipse, a polygonal cross-sectional shape or generally any kind of spline. The rotation causes centrifugal forces that cause droplets or mist particles to accumulate at the apex of the arcuated surface where these may coalesce and form a film that will inhibit flow of leakage fluid.

According to an embodiment of this disclosure the proximal section branches into two distal sections consisting of (i) an auxiliary rotor-associated leakage path (for each of the one or more auxiliary rotors), and (ii) a second part-associated leakage path. Each of the auxiliary rotor-associated leakage paths extends in a general axial direction and is formed between one of the auxiliary rotors and congruent surfaces of the first part. The second part-associated leakage path is generally radially directed and is extending from the branchpoint along faces of said second part.

By an embodiment of this disclosure said generally radially directed section is linked at its distal end to a distal section extending from said distal end in a general axial direction. Thus, the distal section of the second part-associated leakage path that extends from the branch point is has one leg that is generally radially oriented and another leg that has a general axial orientation.

By an embodiment of this disclosure, said annular members have an inner, generally radially oriented face defining side walls of the confined annular space, an outer face longer than the inner face extending in a generally radial direction and defines said radially directed section. Where said second part is the inner element encompassed within the confines of or a frame constituted or defined by said first part, said outer face extends radially in the general direction of the axis. Where the arrangement is reversed, namely said first part is encompassed within the confines of said second part, said outer face extends in the opposite direction, namely in a direction away from the axis.

The branching the proximal section into the two distal sections may yield a backup of leakage losses by oscillations of the fluid along the path of each branch and may also induce pressure drop and concomitant reduction speed and condensation of flow of the fluid the leakage path branchpoint and, hence, de facto sealing of these paths.

The rotating elements and the fluid leakage paths on the two sides of the apparatus typically display a mirror symmetry about a plane of symmetry passing through the midline of the confined annular space and normal to the main axis.

The apparatus by an embodiment of this disclosure comprises at least one circumferential radial projection, namely a projecting member that extends radially in all directions and having the general form of a disc, extending from a rotating element of (e.g. a main rotor and/or an auxiliary rotor) into and rotatable within a congruent receiving recess of another element, defining a tortuous fluid leakage path with sections thereof extending in a general radial direction and linked to one another by a section extending over a rim of the at least one circumferential radial projection. As the leakage paths are typically mirror symmetric on both sides of the confine annular space, the radial projections may be symmetrically formed on both sides of said space. There may be two or more such circumferential projections in each fluid leakage path and in such a case they may all be of the same radial span from the rotating element (namely the maximal diameter of the radial projection), although typically (albeit not exclusively) at least one of them has a radial span that is different than at least one other circumferential projection. In some cases there may be one such circumferential projection with a relatively large radial span flanked by two, three or more circumferential projections of a relatively small radial span; or there may a two or three with a first of these (namely the first encountered by the fluid flowing through the leakage path out of the confined space) being the largest and consecutive ones with descending radial extensions.

The at least one circumferential projection may be formed in the second part and rotatable within a congruent receiving recess of said first part to define a tortuous auxiliary fluid leakage path with sections thereof generally radially extending from both axial sides of the projection and linked to one another by a section that extends over the rim, typically arcuated, of the circumferential projections. Similarly, the at least one circumferential projection may be formed in the auxiliary rotor and rotatable within a congruent receiving recess of the first part, defining a tortuous auxiliary fluid leakage path with sections thereof generally radially extending from both axial sides of the projection and linked to one another by a section that extends over the rim, typically arcuated, of the circumferential projections. The circumferential projections may have a generally tapering cross-section extending from their base to a rounded tip.

The fluid flowing through the leakage path is induced into a swirl by the rotating element. The rotational component of the swirl increases when the fluid flows about the circumferential projections, as the absolute speed of rotation at the apex is greater than at the basis. This gives rise to centrifugal forces that grow toward the apex, and these centrifugal forces cause accumulation of fluid carried components (comprising one or more of droplets, mist or other particles carried by the fluid) to accumulate at an apex of such segments of the circumferential radial projections, typically generating a film that reduces or at times almost entirely prevent leakage.

According to an embodiment of this disclosure the auxiliary rotor-associated fluid leakage path has a segment immediately distal to the branchpoint that defines a general trajectory away from the auxiliary axis.

Said generally radially directed section has typically a trajectory such that the difference in heat-induced radial to axial expansion will cause a minimal change in the width of the gap between congruent surfaces of the generally radially directed section, e.g. a change in width that is less than about ±25% over the range of operating temperatures of the apparatus. By one example, the trajectory of said proximal section is about 81°.

It should be noted that similar considerations for the trajectory of said generally radially directed section may apply also to the generally radially directed sections of the fluid leakage paths that are defined about the circumferential radial projections.

The angle between the said segment of the auxiliary rotor-associated leakage paths and said outer face may be about 90°.

By an embodiment of this disclosure the leakage paths are configured such that the flow time of fluid from the annular confined space has a travel time through the leakage path (particularly, but not only, in a consequence of the branching at said leakage path branchpoint and the slowdown of the rate of flow of the fluid in consequence thereof) is longer than the time for pressure change in angular portions of the confined annular space in consequence of rotation of the projecting elements in said space between different pressure strokes: including a pressure-stroke with high pressure to a suction-stroke with low pressure, when the apparatus is configured or operative as a compressor; or from an expansion stroke with high pressure to a complete expansion or a condensation-stroke in the annular chamber(s), when the apparatus is configured or operative as an expander. There is some inherent delay between a rise in pressure until it translates into flow of fluid through the leakage path (or any fluid flow path for that matter) pressure. The pressure of fluid in any portion of the confined annular space cyclically changes between high and low pressure. If the flow time of pressurized fluid through the flow paths is longer than the time it takes for the fluid to travel through the fluid flow paths before a resulting flow of fluid through the leakage paths, this may serve as a barrier for fluid leakage. Namely, there will rather be a cyclical change in flow direction in the fluid leakage paths between a forward direction and a counter direction.

The peripheral portions of rotating elements that comprise the apex of said arcuated section or the rim of the circumferential radial projections define segments of a leakage path with congruent faces, that yield, as noted above, to the accumulation of particles, including droplets and mist, resulting in formation of a film in such segments that impedes, or at times, substantially blocks free flow of fluid through the leakage paths.

By an embodiment of this disclosure, the fluid leakage path has an enlarged cross-section at a portion thereof opposite the rim of a circumferential radially projecting member. This results in a local pressure drop, in consequence of the enlarged cross-section, reducing speed of the fluid flowing therethrough, thus facilitating deposition of droplets or mist and the formation of a film.

By embodiments of this disclosure, one or more of leakage paths are configured to have one or more section with a width different than other sections. Enlargement of the width may yield reduction in pressure of the fluid flowing in the leakage path and a resulting slow-down in travel speed of fluid in the fluid leakage path. The leakage path branchpoint may also be configured to cause reduction of pressure and a resulting slow-down in travel speed of fluid in said auxiliary rotor-associated leakage path and the radially directed section of the second part-associated leakage path. This may be achieved through a change in dimensions of said width, which causes a pressure drop and, hence, a slowdown of flow-speed of leaking fluids through the leakage paths. In some embodiments the fluid leakage paths may be configured to have number of width changes of dimensions. This may be through design of some imperfect congruencies at certain sections of the liquid flow paths.

The slowing down of the flow of the fluid through the fluid leakage paths may also be achieved through a three-dimensional surface structure that is configured to increase friction of the fluid flowing in such section. Such a surface structure may be achieved through the introduction of minute or even microscopic surface imperfections, such as abrasions, indentations, or protrusions. For example, a portion of one or both of (i) a section of said auxiliary rotor-associated leakage path that extends from said branching and (ii) said proximal section, has such a three-dimensional surface structure.

In some embodiments, particularly embodiments of embodiment (2), a fluid seal is fitted in one or more of the fluid leakage paths. These may comprise one or more rotary sealing elements fitted at an end of a fluid leakage path. Such rotary sealing elements may comprise encapsulated ball bearings.