FIELD

[0001 ] The disclosure relates to fluid motors and methods of operating fluid motors. In particular examples, a fluid motor is provided in the form of a positive displacement turbine, capable of operating in a positive displacement mode and in a turbine mode.

BACKGROUND [0002] US Patent No. 8,695,564 (Murphy et al.) discloses a toroidal engine that can be powered by a fuel/air mixture or by a compressed gas source. The toroidal engine uses one-way bearings to transfer torque generated in a toroidal chamber directly to a drive shaft. Pairs of pistons are mounted on two crank assemblies, which are concentric with the drive shaft. One-way bearings allow the crank assemblies to turn, one at a time, in one direction only. The crank assemblies are directly coupled to the drive shaft, which eliminates the need for complex gear and linkage arrangements. In some applications, a system can be used with the toroidal engine to alternately stop the crank assemblies at a pre-determined position and to time the ignition of the engine.

[0003] US Patent No 3,924,980 (Gordon) purports to disclose a rotary engine for use as a fluid motor or pump which employs a rotor carrying pistons that are adapted to rotate within a circular chamber. A working fluid is introduced into and exhausted from the chamber through inlet and outlet ports provided on opposite sides of a rotary blocking valve. The blocking valve is formed with a concaval recess and is driven to turn conjointly with the pistons so that the latter are successively enveloped within and move across the blocking valve. The inlet port and blocking valve are arranged to provide an effective pressure stroke of greater than 120 for a three piston engine to prevent stalling and deadspots in the engine's operation. The engine is dynamically balanced for high speed operation in the manner of a turbine. Close-spaced, frictionless clearance between the piston and chamber walls is provided. Fluid leaks at a controlled rate around the pistons to form a backpressure in the trapped volume ahead of the pressurized volume. Fluid leakage around the rotor is controlled due to back pressure developed in the pressure sealed housing enclosing the elements.

SUMMARY

[0004] The following summary is intended to introduce the reader to various aspects of the applicants teaching, but not to define any invention. In general, disclosed herein are one or more methods relating to operating a motor. For example, the one or more methods can include a method for urging rotation of an output shaft. The method may comprise delivering fluid to a motor coupled to the output shaft. The motor can include a housing and at least one first chamber in the housing. The method may further comprise operating the motor in a positive displacement mode for at least a first period of time and in a turbine mode for at least a second period of time to transfer energy from the fluid to rotation of the output shaft about its longitudinal axis.

[0005] According to some aspects of the teaching disclosed herein, a method of urging rotation of an output shaft includes (a) delivering fluid to a motor, the motor having a housing and at least one first chamber in the housing, and the motor coupled to the output shaft; and (b) operating the motor in a positive displacement mode for at least a first period of time and in a turbine mode for at least a second period of time to transfer energy from the fluid to rotation of the output shaft about its longitudinal axis.

[0006] In some examples, the method includes varying a rate at which the fluid is delivered to the motor to induce transitioning between the positive displacement mode and the turbine mode. In some examples, a torque load applied to the motor is varied to induce transitioning between the positive displacement mode and the turbine mode. Some examples may include momentarily reducing the torque load applied to the motor to induce transitioning from the positive displacement mode to the turbine mode. The second period of time can be separate from, and subsequent to, the first period of time.

[0007] In some examples, operating the motor in the positive displacement mode can include: (a) filling the at least one first chamber of the motor with a first amount of the fluid through at least one first inlet fixed to the housing and in fluid communication with the first chamber, the first chamber having a chamber volume that is variable between a first volume and a second volume greater than the first volume; (b) evacuating the first amount of the fluid from the first chamber through at least one first outlet fixed to the housing; (c) before the evacuating step, forcefully expanding the chamber volume from the first volume to the second volume, the forceful expanding of the chamber volume performing work that is transferred to rotation of the output shaft; and (d) after the evacuating step, repeating the filling step.

[0008] In some examples, during filling the first chamber, the first chamber can be in fluid communication with the first housing inlet and in fluid isolation of the first outlet. The first chamber can be at least partially bounded by circumferentially spaced apart leading and trailing pistons, each piston circumferentially translatable within the housing about the shaft axis in a forward rotational direction and inhibited from circumferentially translating in an opposite, reverse rotational direction, and wherein the step of forcefully expanding the chamber volume of the first chamber can include urging the leading piston to move away from the trailing piston in the forward rotational direction. Each piston can be coupled to the shaft by a respective leading and trailing indexing clutch, the leading indexing clutch transferring motion of the leading piston to rotation of the shaft, and the trailing indexing clutch accommodating forward rotation of the shaft while the trailing piston remains stationary. Each piston can be coupled to the housing by a respective leading and trailing backstopping clutch, the trailing backstopping clutch inhibiting the trailing piston from rotating in the reverse direction, and the leading backstopping clutch accommodating forward rotation of the leading piston relative to the housing.

[0009] In some examples, during the evacuation step, the leading piston may remain generally stationary and the trailing piston can be advanced toward the leading piston. In some examples, during successive alternating filling steps, the leading piston can alternately include a first piston fixed to a first rotor and a second piston fixed to a second rotor. Expanding the volume of the first chamber to the second volume can includes exerting a stopping force on the first rotor so that further rotation of the first rotor relative to the second rotor is inhibited. The step of exerting a stopping force can include mechanically engaging a first abutment member affixed to the first rotor with a second abutment member affixed to the second rotor. Alternately or additionally, the step of exerting a stopping force can include contracting a volume of a chamber disposed rotationally ahead of the leading piston, the contracting chamber pressing fluid against the leading face of the leading piston. The exertion of a stopping force on the leading piston can also act to force the trailing piston in the forward direction to cause the trailing piston to move into the next position as described in the following paragraph.

[0010] In some examples, after the chamber volume of the first chamber has been expanded to the second volume, the first and second rotors may rotate simultaneously in the forward direction, moving the trailing piston across the at least one first inlet, bringing a second chamber in fluid communication with the first inlet and the first chamber in fluid communication with the first outlet. Evacuating the fluid from the first chamber can include reducing the chamber volume of the first chamber to the first volume. At least a portion of the first amount of the fluid can bypass at least one of the leading and trailing pistons to enter a second chamber adjacent the first chamber.

[001 1 ] In some examples, operating the motor in the turbine mode can include: (a) delivering a first mass of the fluid to the at least one first chamber through a first inlet fixed relative to the housing, the first chamber at least partially bounded by circumferentially spaced apart leading and trailing pistons, each piston circumferentially translatable within the housing about the shaft axis in a forward rotational direction and inhibited from circumferentially translating in an opposite, reverse rotational direction, the circumferential spacing between the leading and trailing pistons remaining generally constant and the first chamber having a chamber volume that remains generally constant during operation of the motor in turbine mode; (b) forcefully directing at least a portion of the fluid delivered to the first chamber to impinge against the leading piston, performing work that is transferred to rotation of the output shaft; and (c) evacuating fluid from the first chamber while the first mass of fluid is delivered to the first chamber.

[0012] In some examples, a portion of the fluid evacuated from the first chamber can be evacuated through at least a first outlet. A portion of the fluid evacuated from the first chamber can bypass at least one of the leading and trailing pistons into another chamber adjacent the first chamber. The step of directing fluid to impinge against the leading piston can urge the leading piston to move about the axis of the shaft in the forward rotational direction. The trailing piston can be urged to move in unison with the leading piston. Each piston can be coupled to the shaft by a respective leading and trailing indexing clutch, the leading indexing clutch and the trailing indexing clutch transferring motion of the leading and trailing pistons to rotation of the shaft. Each piston can be coupled to the housing by a respective leading and trailing backstopping clutch, the leading and trailing backstopping clutch accommodating forward rotation of each piston relative to the housing and inhibiting reverse rotation of each piston relative to the housing.

[0013] In some examples, the fluid can be a compressible fluid. In some examples, operating the motor in the positive displacement mode can produce a pulsating sound with discrete amplitude variances and peaks. Operating the motor in the turbine mode can produce a turbine-like whine sound with substantially continuous amplitude variances and minimal peaks. Operating the motor in the positive displacement mode can produce a substantially different sound than operating the motor in the turbine mode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings included herewith are for illustrating various examples of apparatuses and methods of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings: [0015] Figures 1 a and 1 b are front and side schematic views, respectively, of a fluid motor;

[0016] Figures 2a to 2d are front schematic views of various stages of the motor of Figures 1 a and 1 b operating in a positive displacement mode;

[0017] Figure 3 is an enlarged view of a portion of the motor of Figure 1 a; [0018] Figure 4 is a front schematic view of the motor of Figure 1 a operating in a turbine mode;

[0019] Figure 5 is a schematic view of the motor operating in another turbine mode; [0020] Figure 6a and 6b are schematic views of various stages of the motor operating in a combined turbine-displacement mode;

[0021 ] Figure 7a to 7c illustrate example graphs showing operational characteristics of the motor during operation; [0022] Figure 8 illustrates an example sound wave generated by the motor when operating in the positive displacement mode; and

[0023] Figure 9 illustrates an example sound wave generated by the motor when operating in the turbine mode.

DETAILED DESCRIPTION [0024] Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or process described below is not an embodiment of any exclusive right granted by issuance of this patent application. Any invention disclosed in an apparatus or process described below and for which an exclusive right is not granted by issuance of this patent application may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors, or owners do not intend to abandon, disclaim, or dedicate to the public any such invention by its disclosure in this document.

[0025] Referring to Figures 1 a and 1 b, an example of a motor 100 for rotating an output shaft 101 in a forward rotational direction 103 is illustrated. Motor 100 is, in the example illustrated, a positive displacement turbine configured to operate in at least two distinct modes, including a positive displacement mode and a turbine mode. The motor 100 is, in the example illustrated, optionally configured as a toroidal motor having a stationary housing 102. Housing 102 can house a portion of shaft 101 and rotors 1 10a, 1 10b (as best shown in Figure 1 b). The rotors are disposed concentrically with, and rotate about, the shaft axis. The rotor 110a may be referred to as a first rotor, and a plurality of pistons (first pistons 112a) may be affixed to the first rotor and spaced equally apart about a periphery of the first rotor 110a. Similarly, the rotor 110b may be referred to as a second rotor and a plurality of pistons (second pistons 112b) may be affixed to the first rotor and spaced equally apart about a periphery of the second rotor 110b.

[0026] In the example illustrated, the first rotor 110a has a first rotor hub 111a and a pair of diametrically opposed first pistons 112a affixed thereto and extending radially outwardly of the hub 111a, and rotor 110b has a second rotor hub 111b and a pair of diametrically opposed second pistons 112b affixed thereto and extending radially outwardly of the hub 111b. The term piston can encompass, for example, blades, vanes, or other similar elements against which fluid can bear to move the piston, which in turn is coupled to a shaft to urge rotation of the shaft. Further, although each of the rotors 110a, 110b are shown to include a pair of diametrically opposed pistons, the rotors 110a, 110b may each include any suitable number of pistons. For example, the rotors 110a, 110b may each include three pistons equally spaced apart and circumferentially disposed about respective rotors 110a, 110b.

[0027] As best shown in Figure 1b, each of the rotors 110a, 110b is supported in housing 102 and coupled to shaft 101. Rotors 110a, 110b can be coupled to shaft 101 by fixedly securing each hub 111a, 111b of respective rotors 110a, 110b to the outer surfaces of respective sleeves 116a, 116b. Sleeves 116a, 116b can be concentrically disposed over and fixedly secured to the outer surfaces of respective first and second indexing clutches 114a, 114b. Each indexing clutch 114a, 114b can be concentrically disposed over shaft 101. [0028] The first indexing clutch 114a can transfer rotational motion of the rotor 110a in the forward direction 103 to rotation of shaft 101 in the forward direction 103, and can accommodate rotation of shaft 101 (relative to the rotor 110a) in the forward direction 103 while rotor 110a is stationary. Similarly, the second indexing clutch 114b can transfer rotational motion of rotor 110b in the forward direction 103 to rotation of shaft 101 in the forward direction 103, and can accommodate rotation of shaft 101 in the forward direction 103 while rotor 1 10b is stationary.

[0029] Rotor 1 10a can be coupled to the housing 102 by a first backstopping clutch 1 18a, and rotor 1 10b can be coupled to the housing 102 by a second backstopping clutch 1 18b. Backstopping clutches 1 18a, 1 18b are disposed over respective sleeves 1 16a, 1 16b, and have their outside perimeter fixedly secured to the interior of respective blocks 1 19a, 1 19b of housing 102.

[0030] The first backstopping clutch 1 18a can accommodate rotation of rotor 1 10a in the forward direction 103 relative to the housing, and can inhibit rotation of rotor 1 10a relative to the housing in a reverse rotational direction opposite the forward direction 103. Similarly, the second backstopping clutch 1 18b can accommodate rotation of rotor 1 10b in the forward direction 103, and can inhibit rotation of rotor 1 10b relative to the housing in the reverse direction.

[0031 ] In some examples, the indexing clutches 1 14a, 1 14b may include bearings that support rotation of the shaft 101 relative to the respective rotors 1 10a, 1 10b, and may be referred to as indexing one-way bearings or driving one-way bearings. Similarly, the backstopping clutches 1 18a, 1 18b may include bearings to rotatably support the respective rotors 1 10a, 1 10b in the housing 102, and may be referred to as backstopping one-way bearings. [0032] The housing 102 and rotors 1 10a, 1 10b can define an interior fluid passage 104 extending circumferentially about shaft 101 . In the example illustrated, the interior fluid passage 104 is bounded by inner surface 105 of housing 102 and outer surfaces 1 15a, 1 15b of the respective hubs 1 1 1 a, 1 1 1 b (as best shown in Figure 1 b).

[0033] Pistons 1 12a, 1 12b are, in the example illustrated, disposed inside the fluid passage 104 and can translate circumferentially in the fluid passage 104 about the shaft 101 (thereby orbiting or rotating about the shaft). Each of pistons 1 12a (affixed to first rotor 1 10a) and pistons 1 12b (affixed to second rotor 1 10b) can rotate about shaft 101 in the forward direction 103, but are inhibited from rotating in the reverse direction. Rotation of pistons 1 12a in the forward direction 103 results in rotation of rotor 1 10a in the forward direction 103, and rotation of pistons 1 12b in the forward direction 103 results in rotation of rotor 1 10b in the forward direction. In the example illustrated, the indexing clutches 1 14a, 1 14b are fixed to rotate with the respective rotors 1 10a, 1 10b, and the shaft 101 can rotate no slower than the indexing clutches 1 14a, 1 14b. As a result, rotation of either of pistons 1 12a, 1 12b in the forward direction 103 rotates the shaft 101 in the forward direction 103.

[0034] Each of pistons 1 12a is interposed between pistons 1 12b. Each of pistons

1 12a, 1 12b has a leading face facing toward the forward direction 103 and a trailing face facing toward the reverse direction. Similarly, any pair of adjacent pistons around the circumference of the shaft 101 can be defined to include a leading piston and a trailing piston, the trailing piston disposed circumferentially behind the leading piston relative to the direction of rotation of the shaft 101 .

[0035] In the illustrated example, pistons 1 12a, 1 12b separate the interior fluid passage 104 into four chambers disposed circumferentially about shaft 101 . The four chambers include, in the example illustrated, a pair of diametrically opposed first chambers 131 and a pair of diametrically opposed second chambers 132. The first chambers 131 are bounded by inner surface 105 of housing 102, outer surfaces 1 15a, 1 15b of the hubs 1 1 1 a, 1 1 1 b, respectively, leading faces of pistons 1 12b, and trailing faces of pistons 1 12a. The second chambers 132 are bounded by inner surface 105 of housing 102, outer surfaces 1 15a, 1 15b of the hubs 1 1 1 a, 1 1 1 b, respectively, leading faces of pistons 1 12a, and trailing faces of pistons 1 12b.

[0036] In the illustrated example, housing 102 can have affixed thereto at least one inlet 106 for delivering a fluid 140 to the chambers of interior fluid passage 104, and at least one outlet 108 for evacuating fluid 140 from the chambers of the interior fluid passage 104. In some examples, fluid 140 can be a compressible fluid. In other examples fluid 140 may be an incompressible fluid.

[0037] During operation of motor 100, fluid 140 can be delivered through inlets 106 at an inlet energy state to chambers of interior fluid passage 104 that are in fluid communication with inlets 106. The delivered fluid 140 performs work on pistons 1 12a, 1 12b. The performed work is transferred to rotation of shaft 101 . The delivered fluid 140 can be evacuated through outlets 108 from chambers of the interior fluid passage 104 that are in fluid communication with outlets 108. The delivered fluid 140 can be evacuated at an outlet energy state that is lower than the inlet energy state, the reduction in energy proportional to the work performed by fluid 140.

[0038] During operation, motor 100 can operate in a positive displacement mode during a first period of time and in a turbine mode during a second period of time, to transfer energy from fluid 140 to rotation of shaft 101 .

Positive Displacement Mode

[0039] Referring to Figures 2a to 2d, an example method of operating motor 100 in a positive displacement mode will now be described. In the positive displacement mode, chambers 131 , 132 have a volume that varies during operation of motor 100 as a result of pistons 1 12a, 1 12b rotating relative to one another in the forward direction 103.

[0040] Referring to Figure 2a, chambers 131 are in fluid communication with inlets 106 and in fluid isolation from outlets 108, while chambers 132 are in fluid communication with outlets 108 and in fluid isolation from inlets 106. Fluid 140 is delivered at a pressure through inlets 106 to chambers 131 , resulting in an amount 142 of delivered fluid 140 filling chambers 131 . The terms "filf' or "filling" as used herein can mean putting a desired amount (e.g., a desired mass) of fluid 140 into chambers of inlet passage 104, and do not necessarily mean filling the chamber to the point that the chamber cannot receive any additional fluid 140. [0041 ] Referring to Figure 3, in some examples, a portion 146 of the delivered fluid 140 may bypass pistons 1 12a, 1 12b, thereby exiting chambers 131 and entering an adjacent chamber (e.g., chamber 132). In the example illustrated, radial gaps 1 16 may be provided between the outer circumference of pistons 1 12a, 1 12b and the inner surface 105 of housing 102, and bypass fluid may flow through the radial gaps 1 16. [0042] Referring back to Figure 2a, filling chambers 131 with fluid 140 causes a pressure differential between chambers 131 and chambers 132. The pressure differential may urge rotation of pistons 1 12a (leading pistons) relative to pistons 1 12b (trailing pistons) in the forward direction 103. As fluid 140 entering through inlets 106 fills chambers 131 , the delivered fluid 140 may also impinge the trailing faces of the leading pistons 1 12a. The resulting change in momentum of the impinging fluid 140 can transfer energy to pistons 1 12a, further urging rotation of pistons 1 12a in the forward direction.

[0043] Referring to Figure 2b, the pressure differential between chambers 131 and chambers 132 and/or the energy transfer from the impinging fluid 140 can force leading pistons 1 12a to rotate in the first direction while trailing pistons 1 12b remain stationary.

[0044] Forcing pistons 1 12a to rotate relative to pistons 1 12b can forcefully expand the volume of chambers 131 from a first volume as shown in Figure 2a to a greater second volume as shown in Figure 2b. The forceful expansion of the volume of chambers 131 performs work that is transferred to rotation of output shaft 101 through rotation of pistons 1 12a, and in turn, rotation of rotors 1 10a. As chambers 131 are forcefully expanded from the first volume to the second volume, chambers 132 contract from a volume generally corresponding to the second volume, as shown in Figure 2a, to a lesser first volume as shown in Figure 2b. As chambers 132 contract, fluid 140 is evacuated from chambers 132 through outlets 108.

[0045] Referring to Figure 2c, pistons 1 12a may continue rotating until further rotation is inhibited by a stopping force. The stopping force may be exerted by mechanical interference of a first abutment member affixed to rotor 1 10a and a second abutment member affixed to rotor 1 10b. Alternatively, or in addition, a stopping force may be exerted by a back pressure exerted by the contracting chamber 132 disposed rotationally ahead of the leading piston 1 12a.

[0046] Before the leading pistons 1 12a come to a stop, both rotors may move simultaneously for a relatively short rotational distance. For example, during application of the stopping force, a portion of the momentum of rotor 1 10a can be transferred to rotor 1 10b. The transfer of momentum can force rotors 1 10a and 1 10b to rotate simultaneously, at the same or different speeds, in the forward direction 103. Rotors 1 10a, 1 10b can continue rotating simultaneously until inlets 106 are brought into fluid communication with and begin filling chambers 132, and outlets 108 are brought into fluid communication with and begin evacuating chambers 131 . The cycle then repeats, with pistons 1 12a, 1 12b alternatingly acting as the leading and trailing pistons.

Turbine Mode

[0047] Referring to Figure 4, an example method of operating motor 100 in a turbine mode will now be described. In the turbine mode, pistons 1 12a and 1 12b rotate simultaneously at substantially the same speed in the forward direction 103. The volumes of the chambers 131 and 132 do vary but remain generally constant during operation of motor 100 in turbine mode.

[0048] In the illustrated example, chambers 131 are in fluid communication with inlets 106 and outlets 108, while chambers 132 are in fluid isolation from inlets 106 and outlets 108. Fluid 140 is delivered under pressure through inlets 106 to chambers 131 . Inlets 106 can be oriented to forcefully direct an amount 442 of the delivered fluid 140 to impinge the trailing faces of pistons 1 12a.

[0049] A change in momentum of the impinging fluid results in energy being transferred from the delivered fluid 140 to forceful rotation of pistons 1 12a in the forward direction 103. The forceful rotation of pistons 1 12a performs work that is transferred through rotor 1 10a to rotation of shaft 101 .

[0050] While the amount 442 of the delivered fluid 140 is delivered to the chambers 131 via inlets 106, fluid 140 is simultaneously evacuated from the chambers 131 . In the example illustrated, one portion 444 of evacuated fluid (that was previously delivered fluid 140) can be evacuated from chambers 131 through outlets 108, which are in fluid communication with the chambers 131 at the same time that the inlets 106 are in fluid communication with the chambers 131 . Alternately or additionally, another portion 446 of the evacuated fluid 140 can be evacuated from chambers 131 by bypassing pistons 1 12b and entering an adjacent chamber 132. In the illustrated example, gaps 1 16 exist between the outer circumference of pistons 1 12a, 1 12b and the inner surface 105 of housing 102, and the portion 446 of evacuated fluid 140 can bypass the pistons 1 12a and/or 1 12b via the gap 1 16. [0051 ] In the example illustrated, the pistons 1 12 and 1 12b may remain spaced apart from each other by an approximately uniform circumferential spacing during turbine mode operation of the motor 101 . Chambers 132 may be in fluid isolation from the outlets 108 during a portion of each rotation of the shaft 101 . As a result, fluid 140 in the chambers 132 can push against piston 1 12b when piston 1 12a is advanced in the forward direction 103. Forcing rotation of pistons 1 12a can therefore urge pistons 1 12b to rotate simultaneously with pistons 1 12a.

[0052] The rotors 1 10a, 1 10b rotate in the forward direction 103 until the trailing pistons pass across the inlets 106 and the leading pistons pass across the outlets 108, bringing inlets 106 and outlets 108 into fluid communication with the second chambers 132. The cycle then repeats, with pistons 1 12a, 1 12b alternatingly acting as the leading and trailing pistons.

[0053] Referring to Figure 5, another example method of operating motor 100 in a turbine mode will now be described. As shown in the illustrated example, rotors 1 10a and 1 10b are rotationally collapsed such that trailing pistons 1 12b are rotationally advanced as far as possible in the forward direction relative to leading pistons 1 12a. The pistons 1 12a, 1 12b or rotors 1 10a, 1 10b may mechanically abut each other in this collapsed configuration. The chambers 131 have a constant volume that is substantially less than that of chambers 132, and the volume of chambers 131 can be negligible compared to that of chambers 132. In other words, the abutting pistons 1 12a, 1 12b can be considered to function as a single composite piston (leaving two composite pistons, in the illustrated example) and the housing 102 can be considered to have an equal number of chambers (two chambers in the example).

[0054] In the illustrated example, the two chambers 132 are in fluid communication with inlets 106 and outlets 108 (chambers 131 are generally in fluid isolation from inlets 106 and outlets 108, particularly when considering higher rotational speeds of the motor 100). Fluid 140 is delivered under pressure through inlets 106 to chambers 132. Inlets 106 can be oriented to forcefully direct an amount 542 of the delivered fluid 140 to impinge the trailing faces of pistons 1 12b. [0055] A change in momentum of the impinging fluid results in energy being transferred from the delivered fluid 140 to forceful rotation of pistons 1 12b in the forward direction 103. The forceful rotation of pistons 1 12b performs work that is transferred through rotor 1 10b to rotation of shaft 101 . [0056] After the amount 542 of the delivered fluid 140 impinges pistons 1 12b to force rotation thereof, a portion 544 of the delivered fluid 140 can be evacuated from chambers 132 through outlets 108. In the illustrated example, gaps 1 16 exist between the outer circumference of pistons 1 12a, 1 12b and the inner surface 105 of housing 102. Another portion 546 of the delivered fluid 140 can be evacuated from chambers 132 by bypassing pistons 1 12a, 1 12b through gaps 1 16.

[0057] As a result of rotors 1 12a, 1 12b being collapsed, rotation of pistons 1 12b in the forward direction urges pistons 1 12a to rotate in unison with pistons 1 12b. The momentum gained from forceful rotation of pistons 1 12b results in rotors 1 10a, 1 10b rotating in unison until inlets 106 and outlets 108 are in fluid communication with an opposite one of chambers 132. The cycle then repeats, with pistons 1 12b continuously acting as the leading pistons and pistons 1 12a continuously acting as the trailing pistons.

Combined Turbine-Displacement Mode

[0058] Referring to Figures 6a and 6b, an example method of operating motor 100 in a combination turbine-displacement mode will now be described. In the turbine- displacement mode, chambers 131 , 132 vary during operation of motor 100 as a result of pistons 1 12a, 1 12b rotating relative to one another in the forward direction. Unlike in some examples of the positive displacement mode, however, pistons 1 12a, 1 12b do not reach a full stroke and rotors 1 10a, 1 10b do not abut or mechanically engage with one another.

[0059] Referring to Figure 6a, chambers 131 are in fluid communication with inlets 106 and outlets 108, while chambers 132 are in fluid isolation from inlets 106 and outlets 108. Fluid 140 is delivered under pressure through inlets 106 to chambers 131 . Inlets 106 can be oriented to forcefully direct an amount 642 of the delivered fluid 140 to impinge the trailing faces of pistons 1 12a. [0060] A change in momentum of the impinging fluid results in energy being transferred from the delivered fluid 140 to forceful rotation of pistons 1 12a in the forward direction. The forceful rotation of pistons 1 12a performs work that is transferred through rotor 1 10a to rotation of shaft 101 . [0061 ] After the amount 642 of the delivered fluid 140 impinges pistons 1 12a to force rotation thereof, a portion 644 of the delivered fluid 140 can be evacuated from chambers 131 through outlets 108. In the illustrated example, gaps 1 16 exist between the outer circumference of pistons 1 12a, 1 12b and the inner surface 105 of housing 102. Another portion 646 of the delivered fluid 140 can be evacuated from chambers 131 by bypassing pistons 1 12b through gaps 1 16. In the turbine-displacement mode, fluid 140 flows through chambers 131 at a higher rate than the rate at which chambers 131 are increasing, resulting in chambers 131 , 132 varying during operation of motor 100 in this mode.

[0062] As a result of chambers 132 being in fluid isolation from outlets 108, rotation of pistons 1 12a in the forward direction can urge displacement of fluid 140 in chambers 132. Urging displacement of fluid 140 in chambers 132 results in fluid 140 in chambers 132 bearing against the trailing faces of pistons 1 12b. Forcing rotation of pistons 1 12a can therefore urge pistons 1 12b to rotate in the forward direction 103.

[0063] Referring to Figure 6b, the momentum gained from the forceful rotation of pistons 1 12a and the displacement of fluid 140 in chambers 132 results in rotors 1 10a, 1 10b rotating until inlets 106 and outlets 108 are brought into fluid communication with chambers 132. The cycle then repeats, with pistons 1 12a, 1 12b alternatingly acting as the leading and trailing pistons.

Operational Characteristics and Transitioning Between Operational Modes [0064] Referring to Figures 7a to 7c, graphs illustrating example torque, flow, and power curves for motor 100 operating in the positive displacement mode (referred to as 'PDM' in Figures 7a to 7c) and the turbine mode is shown.

[0065] Referring to Figure 7a, the torque and power curves are shown as a function of rotations per minute of motor 100. As illustrated, during operation, motor 100 transitions between operating in the positive displacement mode at lower rotational speeds and higher torque to operating in the turbine mode at higher rotational speeds and lower torque. The turbine-displacement mode can have similar torque and speed characteristics as the turbine mode. [0066] Motor 100 may automatically transition between the positive displacement mode and the turbine mode in response to a change in operational characteristics. In the illustrated example, motor 100 automatically transitions between the positive displacement mode and the turbine mode when the rotational speed of motor 100 is approximately 750 to 1200 rotations per minute. [0067] Referring to Figure 7b, a transition between the positive displacement mode and the turbine mode may be induced by varying the rate at which fluid 140 is delivered to motor 100. For example, increasing the rate at which fluid 140 is delivered to motor 100 may induce a transition from the positive displacement mode to the turbine mode. [0068] Referring to Figure 7c, a transition between the positive displacement mode and the turbine mode may be induced by varying the torque load applied to motor 100. For example, momentarily reducing the torque load applied to motor 100 may induce a transition from the positive displacement mode to the turbine mode.

Sound Characteristics of Operational Modes [0069] Referring to Figure 8, an example sound wave generated by motor 100 when operating in the positive displacement mode is shown. The positive displacement mode can generate a distinctive sound comprised of a pulsing, throttling, engine-like sound. This sound pattern can be generated from a combination of rotors 1 10a, 1 10b colliding and the highly pulsatile flow of fluid 140 through outlets 108. When plotted on a sound amplitude vs. time graph 800, the generated sound can produce a frequency determined by the inverse of time 802 between amplitude peaks 804, and the throttling sound can be generated by the relatively large difference between the maximum sound amplitude 806 and the minimum sound amplitude 808. [0070] Referring to Figure 9, an example sound wave generated by motor 100 when operating in the turbine mode is shown. The turbine mode can generate a distinctive sound comprised of a smoother, harmonic, turbine-like sound. This sound can be generated from a substantially constant flow of fluid 140 though outlets 108 with lower pressure pulses, and a lack of sounds from rotors 1 10a, 1 10b colliding as can occur in the positive displacement mode. When plotted on a sound amplitude vs. time graph 900, the generated sound can produce a frequency determined by the inverse of time 902 between amplitude peaks 904, and a smoother 'Whining" sound can be generated by the relatively lower difference between the maximum sound amplitude 906 and the minimum sound amplitude 908.

[0071 ] As can be seen from a comparison of Figures 8 and 9, operating motor 100 in the positive displacement mode generates a substantially different sound than operating motor 100 in the turbine mode. When operating in the combined turbine- displacement mode, motor 100 generates a sound similar to that generated when motor 100 is operating in the turbine mode.

[0072] While the above description provides examples of one or more processes or apparatuses, it will be appreciated that other processes or apparatuses may be within the scope of the accompanying claims.