Positive displacement turbine

Abstract

A method of urging rotation of an output shaft comprises delivering fluid to a motor coupled to the output shaft. The motor has a housing and at least one first chamber in the housing. The method further comprises 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.

1 . A method of urging rotation of an output shaft, the method comprising:
 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.   
     
     
         2 . The method of  claim 1 , further comprising varying a rate at which the fluid is delivered to the motor to induce transitioning between the positive displacement mode and the turbine mode. 
     
     
         3 . The method of  claim 1  further comprising varying a torque load applied to the motor to induce transitioning between the positive displacement mode and the turbine mode. 
     
     
         4 . The method of  claim 3  further comprising momentarily reducing the torque load applied to the motor to induce transitioning from the positive displacement mode to the turbine mode. 
     
     
         5 . The method of  claim 1 , wherein the second period of time is separate from, and subsequent to, the first period of time. 
     
     
         6 . The method of  claim 1 , wherein operating the motor in the positive displacement mode comprises:
 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, and   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.   
     
     
         7 . The method of  claim 6 , wherein during filling the first chamber, the first chamber is in fluid communication with the first housing inlet and in fluid isolation of the first outlet. 
     
     
         8 . The method of  claim 7 , wherein the first chamber is 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 includes urging the leading piston to move away from the trailing piston in the forward rotational direction. 
     
     
         9 . The method of  claim 8 , wherein each piston is 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. 
     
     
         10 . The method of  claim 8 , wherein during the evacuation step, the leading piston remains generally stationary and the trailing piston is advanced toward the leading piston. 
     
     
         11 . The method of  claim 8 , wherein during successive alternating filling steps, the leading piston alternately comprises a first piston fixed to a first rotor and a second piston fixed to a second rotor. 
     
     
         12 . The method of  claim 11 , wherein expanding the volume of the first chamber to the second volume includes exerting a stopping force on the first rotor so that further rotation of the first rotor relative to the second rotor is inhibited. 
     
     
         13 . The method of  claim 12 , wherein the step of exerting a stopping force includes mechanically engaging a first abutment member affixed to the first rotor with a second abutment member affixed to the second rotor. 
     
     
         14 . The method of  claim 1 , wherein operating the motor in the turbine mode comprises:
 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.   
     
     
         15 . The method of  claim 14 , wherein a portion of the fluid evacuated from the first chamber is evacuated through at least a first outlet. 
     
     
         16 . The method of  claim 15 , wherein the trailing piston is urged to move in unison with the leading piston. 
     
     
         17 . The method of  claim 14 , wherein a portion of the fluid evacuated from the first chamber bypasses at least one of the leading and trailing pistons into another chamber adjacent the first chamber. 
     
     
         18 . The method of  claim 17 , wherein each piston is 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. 
     
     
         19 . The method of  claim 14 , wherein the step of directing fluid to impinge against the leading piston urges the leading piston to move about the axis of the shaft in the forward rotational direction. 
     
     
         20 . The method of  claim 1 , wherein the fluid is a compressible fluid.