Patent Application
20150159648
The present disclosure relates generally to the field of planetary rotor machines.
Multi-rotor planetary rotor machines may be utilized as positive displacement devices in a variety of applications. A planetary rotor machine typically employs 3 or 4 rotors equally disposed around a central machine axis. All of the rotors have the same shape and rotate in the same direction. Together, the multiple rotors cooperative to form an internal working volume, or cavity, bounded by the rotors themselves.
Planetary rotor machines utilize rotors having lobes with an axial helical twist to create an internal “progressive cavity” that conducts fluid along the machine center axis in a manner similar to a screw auger. Fluid (gas, liquid, or multiphase) is introduced at one end of the rotor assembly from a first pressure regime, and is transported by the rotor-formed cavity to the opposite end for discharge into a different pressure regime. In this manner the planetary rotor machine operates as an expander or compressor to either produce or extract shaft power.
Axial walls of the cavity are provided by flat, stationary head plates, or manifolds, that abut opposite ends of the rotor assembly. In this manner, and unlike conventional twin screw machines, planetary rotor machines do not require a precision encasement surrounding the rotor assembly. Rather, the cavities are formed by the meshing rotors in cooperation with the flat manifolds abutting the rotor ends.
The mutually engaging planetary rotors constitute the radial walls of the progressive cavity, without requiring an external housing. The adjacent surfaces of meshing rotors are non-contacting and separated by a small gap. The volumetric efficiency of a planetary rotor machine, as a function of cavity leakage via inter-rotor gaps, is an important parameter affecting overall machine efficiency. Leakage arising from the finite inter-rotor gap may constitute the primary loss mechanism affecting machine efficiency.
Unidirectional rotor rotation produces high relative velocities between adjacent rotor surfaces at their meshing points. Frictional issues that may arise from physical contact of adjacent meshing rotors may be largely mitigated by holding tight non-contact running clearances between rotors, which in turn calls for precision dimensional tolerances of rotor contours and exacting angular synchronization during rotation of all rotors relative to one another. Accordingly, maximizing efficiency in a planetary rotor machine depends significantly upon minimizing cavity leakage, which in turn relies on precise angular synchronization of all rotors relative to one another during rotation.
In some prior planetary rotor machines, rotor synchronization has been accomplished via planetary rotor gears meshing with a central sun gear or internal ring gear to transfer torque from multiple rotors into a single main output/input shaft. However, meshed gears require a degree of intentional backlash or play to accommodate lubrication, machining non-symmetry, and rotational eccentricities. Such backlash limits the precise inter-rotor clearances that are desirable in planetary rotor machines. Accordingly, utilizing gear trains for rotor synchronization results in larger inter-rotor gaps and reduced machine efficiency. Further, in such planetary gear trains, inter-rotor synchronization utilizes two meshing points, thereby doubling the backlash of a single geared pair and further compromising rotor synchronization.
Some prior planetary rotor machines have attempted to achieve rotor synchronization via belts and pulleys. However, belt and pulley teeth are prone to deformation and alignment shift under varying torque loads. Additionally, variations in belt manufacturing results in non-uniform spacing between teeth and different size/shape teeth on a given belt. Accordingly, such belt and pulley systems have proven to be more problematic than gear train synchronization mechanisms.
Other prior attempts to synchronize rotors via roller chains and sprockets have proven to be problematic. Backlash in chain driven mechanisms causes problems similar to geared systems. Irregularities in chain manufacturing causes spacing discrepancies in chain linkages. Extended use of chain systems results in wear of chain and sprocket surfaces compounding backlash issues. Torque transfer via a chain and sprocket causes chains to stretch increasing backlash.
Embodiments that relate to a planetary rotor machine are provided. In one embodiment, a planetary rotor machine comprises a plurality of helical rotors for compressing or expanding a fluid. Each of the helical rotors is configured to rotate about a rotor rotational axis, and each of the rotor rotational axes is equally spaced from a central axis of the planetary rotor machine. A rotor shaft is fixedly coupled to each of the helical rotors and extends axially along the rotor rotational axis.
A rotor crank is coupled to each of the rotor shafts and comprises a rotor crank arm that extends away from the rotor rotational axis. Each rotor crank arm comprises a rotor crankpin at a distal end that is laterally spaced from the rotor rotational axis. A synchronizing plate is rotatably coupled to each of the rotor crankpins for non-rotative epicyclic oscillation with respect to the plurality of rotor shafts and the helical rotors. A driver crank is rotatably coupled to a central bearing in a geometric center of the synchronizing plate. A driveshaft is fixedly coupled to the driver crank and located coaxial with the central axis of the planetary rotor machine.
Another embodiment relates to a 4-rotor synchronizing mechanism for a 4-rotor planetary rotor machine. The 4-rotor planetary rotor machine comprises 4 helical rotors for compressing or expanding a fluid and 4 rotor shafts. Each of the helical rotors is fixedly coupled to one of the rotor shafts and configured to rotate about a rotor rotational axis. Each of the rotor rotational axes is equally spaced from a central axis of the 4-rotor planetary rotor machine.
The 4-rotor synchronizing mechanism comprises 4 rotor cranks that are each coupled to one of the 4 rotor shafts, each of the rotor cranks comprising a rotor crank arm that extends away from the rotor rotational axis. Each of the rotor crank arms comprises a rotor crankpin at a distal end that is laterally spaced from the rotor rotational axis. A synchronizing plate comprises 4 bearings symmetrically oriented around a geometric center of the synchronizing plate at 90 degree intervals, with each of the bearings rotatably coupled to one of the 4 crankpins for non-rotative epicyclic oscillation of the synchronizing plate with respect to the 4 rotor shafts and the 4 helical rotors. A driver crank is rotatably coupled to a central bearing in the geometric center of the synchronizing plate. A driveshaft is fixedly coupled to the driver crank and located coaxial with the central axis of the planetary rotor machine.
Another embodiment relates to a 3-rotor synchronizing mechanism for a 3-rotor planetary rotor machine. The 3-rotor planetary rotor machine comprises 3 helical rotors for compressing or expanding a fluid and 3 rotor shafts. Each of the helical rotors is fixedly coupled to one of the rotor shafts and configured to rotate about a rotor rotational axis. Each of the rotor rotational axes is equally spaced from a central axis of the 3-rotor planetary rotor machine,
The 3-rotor synchronizing mechanism comprises 3 rotor cranks that are each coupled to one of the 3 rotor shafts. Each of the rotor cranks comprises a rotor crank arm that extends away from the rotor rotational axis. Each of the rotor crank arms comprises a rotor crankpin at a distal end that is laterally spaced from the rotor rotational axis. A synchronizing plate comprises 3 bearings symmetrically oriented around a geometric center of the synchronizing plate at 120 degree intervals, with each of the bearings rotatably coupled to one of the 3 crankpins for non-rotative epicyclic oscillation of the synchronizing plate with respect to the 3 rotor shafts and the 3 helical rotors. A driver crank is rotatably coupled to a central bearing in the geometric center of the synchronizing plate. A driveshaft is fixedly coupled to the driver crank and located coaxial with the central axis of the planetary rotor machine.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
The present disclosure will be better understood from reading the following description of non-limiting embodiments with reference to the attached drawings, wherein:
It will be appreciated that planetary rotor machines and corresponding synchronizing mechanisms of the present disclosure may be utilized in other power generation applications including, but not limited to, geopressure power production, waste heat applications, solar thermal and solar ponds, biomass, and other applications using thermal resources with sufficient heat capacity. Planetary rotor machines and corresponding synchronizing mechanisms of the present disclosure also may be utilized with any pressurized fluid, regardless of viscosity or temperature, to produce electric power instead of dissipation through pressure let-down valves. Examples include, but are not limited to, natural gas wellhead pressure letdown, grid sub-station pressure let-down, producing oil & gas wells, off-shore oil platforms, industrial processes, biomass refinement let-down, slurry (suspended particulate) pumping such as coal slurry, wood chip slurry, and biomass pumping, and high pressure pumping such as hydrofracking It will also be appreciated that that planetary rotor machines and corresponding synchronizing mechanisms of the present disclosure also may be utilized in a variety of compressor applications.
Examples of manifolds for planetary rotor machines are discussed in U.S. Patent Application Publication No. 2014/0255232 entitled PLANETARY ROTOR MACHINE MANIFOLD, the disclosure of which is hereby incorporated by reference for all purposes.
As the rotors 114 of the machine 100 rotate, the space enclosed between the meshing rotors 114 forms a cavity that progresses axially during rotor rotation due to the helical axial twist of the rotor lobes. As the cavity progresses it forms a varying volume that is bounded by the rotors 114 themselves. This progressive cavity transports fluid (gas, liquid, or multiphase) along the machine center axis like a screw auger. A minimum helical twist of 180° may be utilized for a 4-rotor machine and a minimum helical twist of 120° may be utilized for a 3-rotor machine, as described in more detail below. A 4-rotor machine produces two complete volume cycles per revolution. A 3-rotor machine produces 3 complete volume cycles per revolution.
Fluid inducted via the intake pipe 118 travels inside the rotor-formed cavity along the machine center axis to the opposite, exit end where it discharges into a higher pressure region for a compressor, or into a lower pressure region for an expander. Accordingly, the process produces shaft power in an expander or extracts shaft power in a compressor.
When operating as an expander, the pressurized fluid drives rotation of the helical rotors 114 (partially shown) and produces shaft power. As described in more detail below, the rotors 114 are coupled to synchronizing mechanism 110 which in turn drives rotation of output driveshaft 154 that is connected to a generator (not shown). After passing through the cavities created by rotors 114, the pressurized fluid may be discharged through an exit manifold (not shown) at the rear of the machine 100.
In the example of
With reference also to
It will also be appreciated that the cross-sectional area of the solid core 150 formed by the converging rotor tips does not directly participate in machine function. The core 150 may comprise a solid, symmetric, 4-sided rod having opposing sides that are mirror images of one another. At least two partial cavities may be formed along the rotor length at any given instant. Thus it will be appreciated that a function of core 150 is to prevent axial leakage between successive cavities.
With reference again to
As shown in
More particularly, each rotor crankpin 174 is centered on a rotor crankpin axis 178. As illustrated in
In the example of
In this manner, the synchronizing plate 184 traces a circular orbit with respect to the rotors 114 and without rotating about its geometric center 200 or otherwise. Alternatively expressed, the synchronizing plate 184 engages in non-rotative epicyclic oscillation with respect to the 4 rotor shafts 130 and 4 helical rotors 114. Accordingly, the rotors 14 are constrained to rotate in rigid synchronization, thereby enabling inter-rotor gaps that are significantly smaller than previously possible. In some examples, planetary rotor machines according to the present disclosure may utilize inter-rotor gaps on the order of 0.001 inches or less. Further, and in contrast to the gear train and belt/pulley systems of other mechanisms, the synchronizing mechanism 110 of the present disclosure enables such precise synchronization and minute gaps to be maintained over significant duty cycles at high speeds, such as 3600 RPM or higher which can produce centrifugal g-force loads in the range of 600 g.
With reference to
Further and with reference to
With reference now to
As shown in the example of
Advantageously, the offset geometry of the spacer necks 820 of the angled rotor crank arms 810 enables increased crank throw length by allowing the distal end 844 of each arm to clear adjacent rotor rotational axes 840 and adjacent rotor cranks. Further, greater crank throw length decreases the forces experienced by the 4 rotor crank bearings 196 of the synchronizing plate 184. Such decrease in force may be described by the following equation:
t=r*F, [1]
Where t=rotor shaft torque, r=length of crank throw, and F=force experienced at the distal end of the rotor crank.
Accordingly and for a given rotor shaft torque t, as the crank throw length r increases, the resulting force F on the rotor crank decreases. Advantageously, reducing the forces experienced by the rotor crank bearings 196 extends the life of the bearings and/or allows the use of smaller bearings in a given application. It will be appreciated that any suitable type of bearing may be utilized for the rotor crank bearings 196 and the central bearing 230 of the synchronizing plates described in the present disclosure. Examples of such bearing types include, but are not limited to, ball bearings, air bearings, journal bearings, and magnetic bearings.
In other examples, a synchronizing mechanism according to the present disclosure may utilize rotor crank arms having 2 or more angled portions that are each angled with respect to the plane of rotation of the rotor crank arm. With reference now to
The 2 angled portions 924 and 928 of spacer neck 920 are each angled with respect to a plane of rotation 830 of the rotor crank arms 910. The spacer neck 920 connects a rotor crank base portion 936 at the rotor rotational axis 940 with the distal end 944 of the rotor crank arm 910. As with the synchronizing mechanisms 110 and 110′ described above, rotor crankpins 174 located at the distal end 944 of the 4 rotor crank arms 910 are rotatably coupled to 4 rotor crank rotor crank bearings 196 that are symmetrically oriented around the geometric center 200 of the synchronizing plate 184 at 90 degree intervals. A driver crank 220″ is rotatably coupled to a central bearing in the center of the synchronizing plate 184. A driveshaft 154 is fixedly coupled to the driver crank 220″ and located coaxial with the central axis of the planetary rotor machine 900. In some examples, driver crank 220″ may include a counterweight 950 for load balancing.
Advantageously, by utilizing rotor crank arms having 2 angled portions 924 and 928, crank throw length may be further increased while maintaining a greater structural integrity of the rotor crank arm as compared to an arm having a single angled portion that creates a similar crank throw. Advantageously and as noted above, further increasing crank throw length correspondingly decreases the forces experienced by the 4 rotor crank bearings 196 of the synchronizing plate 184.
With reference again to
As noted above, the principles of the present disclosure may also be utilized in connection with a planetary rotor machine having 3 rotors that each embodies a 3-lobed rotor design. With reference now to
Each rotor 1000 is fixedly coupled to a rotor shaft 1020 and configured to rotate about a rotor rotational axis 1028. Each of the rotor shafts 1020 and corresponding rotors 1000 rotates in the same direction, shown in this example by action arrow B. As best seen in
Each rotor shaft 1020 engages the synchronizing mechanism 1030 via a rotor crank 1040 that transmits rotor and shaft rotation to a driveshaft 1034. Advantageously, and as with the synchronizing mechanism 110 described above, the synchronizing mechanism 1030 couples all rotating elements in rigid angular alignment during rotation, irrespective of the differing locations of the rotational axis of individual rotors and the output driveshaft 1034.
As shown in
With reference to
As best seen in
In this manner and like the synchronizing plate 184 described above, the synchronizing plate 1060 traces a circular orbit with respect to the rotors 114, and without rotating about its geometric center 1082 or otherwise. Alternatively expressed, the synchronizing plate 1060 engages in non-rotative epicyclic oscillation with respect to the 3 rotor shafts 1020 and 3 helical rotors 1000. Accordingly, the rotors 1000 are constrained to rotate in rigid synchronization, thereby enabling inter-rotor gaps on the order of 0.001 inches or less. Further, and in contrast to the gear train and belt/pulley systems of other mechanisms, the synchronizing mechanism 1030 enables such precise synchronization and minute gaps to be maintained over significant duty cycles at high speeds, such as 3600 RPM or higher.
With reference now to
Further and with reference to
With reference now to
As described above, the offset geometry of the spacer necks 1520 of the angled rotor crank arms 1500 enables increased crank throw length by allowing the distal end of each arm to clear adjacent rotor rotational axes 1540 and adjacent rotor cranks. Advantageously, greater crank throw length decreases the forces experienced by the 3 rotor crank bearings 1078 of the synchronizing plate 1060.
As with the 4-rotor planetary rotor machine and synchronizing mechanism described above, in other examples of a 3-rotor planetary rotor machine a synchronizing mechanism according to the present disclosure may utilize rotor crank arms having 2 or more angled portions that are each angled with respect to the plane of rotation of the rotor crank arm.
It will be appreciated that the principles of the present disclosure may be utilized with planetary rotor machines including any suitable number of rotors greater than 4 rotors.
It also will be appreciated that references to “one embodiment” or “an embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects.
The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
This application claims priority to U.S. Provisional Patent Application Ser. No. 61/914,221, filed on Dec. 10, 2013 and entitled PLANETARY ROTOR MACHINE ROTOR CRANK LINKAGE, the entirety of which is hereby incorporated by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 61914221 | Dec 2013 | US |
