Patent GB-952575-A (GB)
Title: Power plant, e.g. for ground effect vehicles
Inventor: COLLEY ROWAN HERBERT
IPC: B60V1/14
Filed: 1962-10-15
Abstract: 952,575. Gas turbine plant; power plant. ROLLSROYCE Ltd. Oct. 15, 1962, No.39013/62. Headings F1G and F1Q. [Also in Division B7] A power plant comprises one or more engines which is or are arranged to supply power for the operation of two separate devices, there being power control means which tend in operation to maintain the speed of the engine or engines at a predetermined value, and power reduction means for reducing the amount of power supplied by the engine or engines to one only of the said two devices whenever the speed of the engine or engines falls to a predetermined extent below the said predetermined value, whereby the power supply to the other said device may be maintained substantially constant. The invention is described with reference to a power plant for a ground effect vehicle which comprises two gas turbine engines 12, 12<SP>1</SP> which are arranged to drive two lift fans 11 and two variable pitch propellers 16, 161 which are adapted to effect forward propulsion of the vehicle. The engines drive through free-wheel devices 13, 13<SP>1</SP> to a gear-box 14 from which the lift fans are driven through a clutch 15, and the propellers through shafting 17, 17<SP>1</SP>, the pitch control units being indicated at 20, 201. The engines have fuel supply control units 34, 341 which have control levers 40, 40<SP>1</SP> which are connected by levers 41, 41<SP>1</SP> to pivoted levers 42, 421, the levers 42, 421 in turn being connected to a common link 46. The points of connection of the levers 41, 41<SP>1</SP> to the pivoted levers 42, 421 are adjustable by means of trim levers 45, 451. The levers 35, 35<SP>1</SP> control shut-off cocks and are connected to manually operable shut-off cock levers 37, 37<SP>1</SP>. The common link 46 is connected to the mid-point of a link 47 one end of which is connected by a link 50 to a power control lever 51 which is movable in a clockwise direction from a maximum power position, through a cruise position shown in full lines to an idling position. The link 50 controls the positions of abutment members 72, 72a by means of rack and pinion devices 73, 73a, the positions of the abutment members determining the loadings of the governor control springs 71, 71a disposed in the fuel governing unit 55 and the underspeed unit 56, respectively. The fuel governing unit 55 comprises a gearwheel 60 mounted on a shaft 54 driven from the gear-box 14, the gear-wheel 60 meshing with another gear-wheel 61 which is secured to a rotatable sleeve 62 which carries the governor weights 63. The gear-wheels 60, 61 form an oil pump which is supplied with oil through the duct 74 and which delivers to ports in the sleeve 62, the ports being controlled by a piston valve 65 having spaced lands 66, 67 and disposed within the sleeve. The piston valve is urged to the left as the governor weights move outwardly with increasing speed against the loading of the spring 71. As the piston valve moves to the left with increasing speed, oil under pressure passes through the duct 77 to the left-hand side of piston 52 which is urged to the right against the loading of its control spring, the piston acting through the link 47 to cause the link 46 to move to the right so acting to reduce the-fuel supply to the engines. Conversely with fall in engine speed. The underspeed unit 56 is similar to the fuel governing unit 55, but in this case the duct 77a is connected to the space in the ram unit 82 to the right of the piston 81, and the duct 80a is connected to the space to the left of the piston 81. As the governor weights 63a move inwardly with fall in speed, the piston 65a moves to the right, oil under pressure flows through duct 80a to the left-hand side of the piston 81 which thereby moves to the right. The piston rod 84 is connected at its left-hand end to a pivoted lever 85 which carries an abutment 90, and at its right-hand end to a pivoted lever 86 which carries an abutment 92. The levers 21, 21<SP>1</SP> of the pitch control units 20, 201 are connected by links 22, 221 to the ends of a lever 23, the mid point of which is connected by a link 25 and spring device 26 to a pitch control lever 27 which is movable in a clockwise direction from a maximum forward pitch position through a neutral pitch position to a maximum reverse pitch position. The lever 23 is formed integrally with a lever 30 which is connected by means of linkage 31 and spring device 32 to a yaw control lever 33, movement of which causes the lever 24 to pivot about its mid-point so producing increased pitch of one propeller and reduced pitch of the other. The link 25 carries a stop 89 which co-operates with the abutment 90 and the links 22, 221 carry stops 91, 911 which co-operate with the abutment 92. As the piston 81 and piston rod 84 move to the right with fall in speed, assuming the pitch control lever 27 to be in the maximum forward pitch position at the left-hand limit of its travel, the abutment 90 will engage the stop 89 and the links 25 and 22 and 221 will be moved to the right to decrease the forward pitch of the propeller blades 16, 161 whereupon the engine speed will increase. If the pitch control lever were in the maximum reverse pitch position at the right-hand limit of its travel, movement of the piston rod 84 to the right will cause the abutment 92 to engage the stops 91, 911 whereby the links 22, 221 will be moved to the left so reducing the reverse pitch of the propeller blades. In the embodiment shown in Fig. 3, the underspeed unit 56 and the ram 53 are dispensed with, the duct 77b in this case communicating with the space at the right-hand side of the piston 81b, and the duct 80b communicating with the space at the left-hand side of the piston 816. The piston rod 84b is connected to levers 85b, 86b as before but the lever 85b is pivotally mounted at its mid-point 94 and the lower end of the lever abuts an abutment 96 mounted on a link 101 which is pivotally connected to the lever 47b. Variations in rotational speed of the engines will produce movement of the lever 85b and so of the link 46b to adjust the fuel control units to restore the engine speed to the predetermined value. If upon fall of the engine speed, the resulting increase in fuel supply is not sufficient to restore the engine speed to the predetermined. value, the continuing clockwise movement of the lever 85b will cause the abutments 90b or 92b to act on the links 22b, 22b<SP>1</SP> to reduce the pitch of the propeller blades. In Fig. 4, the ducts 77c, 80c communicate with the spaces to the left-hand sides of the pistons 52c, 81c, the spaces to the right-hand sides of the pistons communicating with each other by way of a conduit 103. Increase in engine speed will cause the pistons 52c, 81c to move to the right and left respectively, this movement of the piston 52c acting to reduce the fuel supply. Fall in engine speed will act conversely, but if the resulting increase in fuel supply is not sufficient to restore the engine speed to the predetermined value, the continuing movement of the piston 81c to the right will act to reduce the pitch of the propeller blades.