GB987909A - Improvements in acceleration control for fluid turbines - Google Patents

Abstract

987,909. Turbines. GENERAL ELECTRIC CO. Oct. 26, 1962 [Oct. 30, 1961(2)], No. 40584/62. Heading FIT. The invention relates to an acceleration control for a turbine, the turbine comprising a bladed rotor against which motive fluid is directed, the rotor being mounted for rotation on a movable member which permits movement of the turbine rotor so as to vary the degree of immersion in the motive fluid stream thereby to vary the magnitude of the force exerted on the rotor by the motive fluid. The turbine rotor is connected to a load, the load reaction being opposed to the force imparted on the rotor by the motive fluid, and a reference force is imparted to the movable mounting member in a direction opposing the net force on the rotor i.e. the difference between the load reaction force and the force imparted by the motive fluid, so as to move the movable member to a position of equilibrium in which the net force on the rotor balances the reference force whereby the value of the net force on the rotor is caused to correspond with a level which is specified by the value of the reference force. In the embodiment shown in Fig. 1 the turbine comprises a rotor 10 having blades 11, motive fluid being directed on to the blades through a nozzle 12. The rotor shaft 13 is mounted in bearings 14, 15 in a member 23 which is itself mounted in bearings 25, 26 in the stator structure. The member 23 is thus allowed a small angular movement about the axis 27 whereby the position of the turbine rotor may be varied with respect to the stationary nozzle 12 so that the amount of fluid impinging on the blades may be varied. The movable member is acted on by a spring 28 which urges the tang 29 on the member against a fixed stop 30. A pinion 16 on the rotor shaft 13 engages with an idler gear 17 which is rotatably mounted in the movable member 23 by means of bearings 18, 19. The idler gear 17 in turn is in engagement with a gear 20 on the output drive shaft, the gear 20 being supported in bearings 21, 22 so that it rotates about the pivoted axis 27 of the movable member 23. The forces acting on the movable member 23 are indicated in Fig. 6 where Fg is the force of the gas stream on the turbine rotor, F 1 , F 2 , F 3 and F 4 are the loads acting on the gears 16, 17, 20, F s is the force of the spring 28, A is the angle indicated in Fig. 1, B and C are the radii of the lines of action of the forces F 1 , Fg sin A, F 2 and F 3 about the axis of rotation 27. It is proved in the Specification that the angular acceleration of the turbine is proportional to the spring force F s . In a second embodiment a movable member 36 and a spring 28 are provided as before, but the movable member incorporates also a fluid pump, the pump being indicated at 37 and comprising a rotor 39 which is driven from the idler gear 17. The pump comprises an inlet 40, a bore 41 in which is disposed a piston 44 which is urged against a stop 47 by a spring. The energy absorbed by the pump increases with increasing speed and so the reaction force exerted on the idler gear 17 by the pump gear 38 increases with increasing speed. In the force diagram of Fig. 11 the idler gear 17 is shown with the reaction force Fp of the pump imposed on it. It is proved in the Specification that the turbine acceleration is independent of the load, and that the acceleration is a function of the pump reaction force Fp as well as being a function of the spring force F s and the turbine wheel torque T L attributable to rotor losses. In Fig. 12 is shown a starter turbine 11 the driving fluid being combustion gases from a cartridge contained in the breech. A movable member-36 is again provided also a fluid pump device 37 as in the second embodiment but the spring is dispensed with. In place of the spring a piston and cylinder device 55, 56 is provided, the piston being pivotally connected to the movable member 36 and being acted on at its right hand face by the pressure of the gases generated in the chamber 52 by the firing of the cartridge, the gas pressure being communicated by way of a line 60. It is stated that this embodiment provides an arrangement in which the acceleration rate of a turbine starter is automatically increased as a function of the propellant chamber pressure which is in turn proportional to the rate of propellant burning.