Propulsion engine

Abstract

A propulsion engine for an aircraft, the propulsion engine comprising: one or more fans ( 1, 2 ) rotatably linked to one or more respective shafts ( 11 ); a driving means arranged to drive the one or more fans; and a first hydraulic pump-motor ( 10 ) connected to one of the fan shafts, the first hydraulic pump-motor comprising a cam ( 12 ) disposed about the shaft and one or more radially extending pistons ( 13 ) arranged to engage a surface of the cam, the cam and pistons being arranged such that the pistons reciprocate due to the rotation of the cam, wherein the first hydraulic pump-motor is arranged to selectively transfer a variable amount of power to or from the one or more fans so as to control the rotational speed of the one or more fans.

1 . A propulsion engine for an aircraft, the propulsion engine comprising:
 one or more fans rotatably linked to one or more respective shafts;   a driving means arranged to drive the one or more fans; and   a first hydraulic pump-motor connected to one of the fan shafts, the first hydraulic pump-motor comprising a cam disposed about the shaft and one or more radially extending pistons arranged to engage a surface of the cam, the cam and pistons being arranged such that the pistons reciprocate due to the rotation of the cam,   wherein the first hydraulic pump-motor is arranged to selectively transfer a variable amount of power to or from the one or more fans so as to control the rotational speed of the one or more fans.   
     
     
         2 . The propulsion engine of  claim 1 , wherein the first hydraulic pump-motor is configurable to operate in a pump mode in which power is extracted from the fan shaft. 
     
     
         3 . The propulsion engine of  claim 1 , wherein the first hydraulic pump-motor is configurable to operate in a neutral mode in which substantially no power is extracted from or delivered to the fan shaft. 
     
     
         4 . The propulsion engine of  claim 1 , wherein the first hydraulic pump-motor is configurable to operate in a motor mode in which power is delivered to the fan shaft. 
     
     
         5 . The propulsion engine of  claim 1 , wherein the or each piston is provided in a piston chamber, the or each piston being arranged to selectively compress and expand a working fluid in the piston chamber. 
     
     
         6 . The propulsion engine of  claim 5 , wherein the first hydraulic pump-motor further comprises one or more valves arranged to selectively connect the working fluid in the piston chamber to a high pressure manifold and/or a low pressure manifold. 
     
     
         7 . The propulsion engine of  claim 6 , wherein the valves are configured to permit the first hydraulic pump-motor to selectively operate in a pump, neutral or motor mode. 
     
     
         8 . The propulsion engine of  claim 6 , wherein the hydraulic pump-motor is configured to vary the valve position during rotation of the shaft. 
     
     
         9 . The propulsion engine of  claim 7 , wherein when the hydraulic pump-motor is operating in the pump mode the valves selectively connect the piston chambers to the low pressure manifold when the piston is expanding the working fluid and the valves selectively connect the piston chambers to the high pressure manifold when the piston is compressing the working fluid. 
     
     
         10 . The propulsion engine of  claim 7 , wherein when the hydraulic pump-motor is operating in the motor mode the valves selectively connect the piston chambers to the high pressure manifold when the piston is expanding the working fluid and the valves selectively connect the piston chambers to the low pressure manifold when the piston is compressing the working fluid. 
     
     
         11 . The propulsion engine of  claim 1 , wherein the propulsion engine further comprises:
 a second hydraulic pump-motor connected to a further fan shaft, the second hydraulic pump-motor comprising a cam disposed about the further fan shaft and one or more radially extending pistons arranged to engage a surface of the cam, the cam and pistons being arranged such that the pistons reciprocate due to the rotation of the cam,   wherein the second hydraulic pump-motor is arranged to selectively transfer a variable amount of power to or from a further fan so as to control the rotational speed of the further fan.   
     
     
         12 . The propulsion engine according to  claim 1 , wherein the propulsion engine comprises first and second fans and the first hydraulic pump-motor is connected to the first fan so as to control the rotational speed of the first fan with respect to the rotational speed of the second fan. 
     
     
         13 . The propulsion engine according to  claim 1 , wherein the first hydraulic pump-motor is arranged to transfer power from the one or more fans to one or more propulsion engine or aircraft accessories. 
     
     
         14 . The propulsion engine according to  claim 1 , wherein the propulsion engine comprises first and second fans and the driving means comprises a differential assembly arranged to provide power to the first and second fans. 
     
     
         15 . The propulsion engine according to  claim 1 , wherein the one or more fans are unducted fans. 
     
     
         16 . A speed controlling assembly for a propulsion engine, the propulsion engine comprising one or more fans rotatably linked to one or more respective shafts,
 wherein the speed controlling assembly comprises a first hydraulic pump-motor connectable to one of the fan shafts, the hydraulic pump-motor comprising a cam disposed about the shaft and one or more radially extending pistons arranged to engage a surface of the cam, the cam and pistons being arranged such that the pistons reciprocate due to the rotation of the cam; and   wherein the hydraulic pump-motor is arrangeable to selectively transfer a variable amount of power to or from the one or more fans so as to control the rotational speed of the one or more fans.   
     
     
         17 . A method of controlling a propulsion engine for an aircraft, the propulsion engine comprising one or more fans rotatably linked to one or more respective shafts, wherein the method comprises:
 providing a first hydraulic pump-motor connected to one of the fan shafts, the hydraulic pump-motor comprising a cam disposed about the shaft and one or more radially extending pistons arranged to engage a surface of the cam, the cam and pistons being arranged such that the pistons reciprocate due to the rotation of the cam;   driving the one or more fans by virtue of a driving means;   selectively transferring a variable amount of power to or from the one or more fans by virtue of the hydraulic pump-motor; and   controlling the rotational speed of the one or more fans.   
     
     
         18 . The method of  claim 17 , wherein the method further comprises operating the first hydraulic pump-motor in a pump mode in which power is extracted from the fan shaft. 
     
     
         19 . The method of  claim 17 , wherein the method further comprises operating the first hydraulic pump-motor in a neutral mode in which substantially no power is extracted from the fan shaft. 
     
     
         20 . The method of  claim 17 , wherein the method further comprises operating the first hydraulic pump-motor in a motor mode in which power is delivered to the fan shaft.