Patent GB-1451070-A (GB)
Title: Bladed rotors suitable for gas turbine ducted-fan engines
IPC: F01D7/00
Filed: 1973-02-17
Abstract: 1451070 Gas turbine ducted fan engines; fans DOWTY ROTOL Ltd 14 Feb 1974 [17 Feb 1973 (2)] 7888/73 and 7889/73 Headings F1C and F1J The invention relates to a bladed rotor and is described with reference to the fan rotor of a gas turbine ducted fan engine, the fan rotor comprising a liquid pressure operable actuator 20 for varying the pitch of the fan blades (not shown). The rotor comprises also a positional control valve assembly 44 and a condition control valve assembly 90, the former acting to control the pitch of the fan blades and the latter acting to move the fan blades to the feathered position should this be necessary as a result of engine shut-down in flight. The control valve assemblies operate one in conjunction with the other, there being separate linkages for controlling the valve assemblies so as to control the actuator which is adapted to receive by way of the valve assemblies liquid delivered by a pump or pumps associated with the rotor, the condition control valve assembly including two co-operable elements, one of which the sleeve 92 is continuously rotatable with respect to the other upon rotation of the rotor. The fan rotor assembly comprises a low flow gear-pump 27, a high flow gear-pump 28 and a feathering pump 148, an annular reservoir 25, and an annular feathering reservoir 26. The pumps normally are driven by gearing G upon rotation of the rotor, but the feathering pump 148 is driven by a motor 149 in the event of engine shut-down. The pump 27 normally supplies fluid to a line 41, the pump 28 supplies fluid through the pump control valve 79 which is in the position shown, through inlet 87 into the feathering reservoir 26. The feathering pump 148 supplies fluid to the line 150 to the condition control valve assembly 90 from which in the position of the assembly shown, it returns through line 163, and non-return valve 164 back to the feathering reservoir 26. The reservoir 26 is connected to the reservoir 25 by line 175. The position control valve assembly 44 comprises an outer sleeve 43, an inner sleeve 45 which is rotated continuously in operation by gear 47, and an axially slidable spool member 46 the axial position of which is controlled by an axially movable tubular member 70 which controls an axially movable cam member 72 which controls the spool by means of a pivoted link 75. The condition control valve assembly 90 also comprises an outer sleeve 91, an inner continuously rotatable sleeve 92 and an axially slidable spool member 93 the axial position of which is controlled by an axially movable tubular member 104 which controls an axially movable cam member 106 which controls the spool by means of a pivoted link 108. The cam 106 also controls a stop withdrawal valve 144 which is utilized when the fan blades are to be rotated to the reverse thrust, negative pitch position. The actuator is indicated at 20 and comprises two bladed relatively rotatable members 155, 156 which define fine pitch chambers having an inlet 160 and coarse pitch chambers having an inlet 158. In the normal running position the valve assemblies 44 and 90 are in the positions shown and fluid delivered by the low flow pump 27 passes through line 41 to the annulus 42 of the control valve 44, also through line 167 to the annulus 116 of the control valve 90; fluid from the line 41 also passes through a restriction 77a to a line 77, thence to annulus 49 of control valve 44; the line 77 also communicates through line 78 with the pump control valve 79, the fluid-pressure and the spring 83 acting to position the valve spool in the position shown in which output from the high flow pump 28 passes through inlet 87 to the feathering reservoir. Upon selecting fine pitch the cam member 72 is moved to the right whereby the spool 46 is moved upwardly. Thus fluid in line 41 may now pass from annulus 42 to annulus 48, thence through line 152 to annulus 113 of control valve 90, thence to annulus 114 and line 159 (the spool 93 being in the position shown) to the inlet 160 of the fine chambers of the actuator 20 whereby the fan blades are moved to fine pitch. The cam member 72 acts to follow up such movement and restores the spool 46 to the initial position. As the spool 46 moved upwardly, the annulus 49 was connected to drain pressure within line 165 (through the hollow interior of the spool) so that pressure downstream of the orifice 77a becomes reduced and this reduced pressure was effective in line 78 whereupon the spool 80 of the pump control-valve 79 moved to the left under action of the spring 83; thus the line 85 was shut off and the output of the high flow pump 28 passed to line 41 to combine with the flow from the low flow pump 27. A similar action occurs in the event of coarse pitch selection, the spool 46 now being moved downwardly, and fluid from line 41 and annulus 42 passing to annulus 50, line 153, annulus 112, annulus 111, line 157 to the inlet 158 to the coarse pitch chambers of the actuator 20. Upon selection of feathering, the cam 106 is moved to the right, the spool 93 of the control valve 90 moving downwardly; thus fluid flowing in line 150 instead of returning to reservoir 26 through lines 166, 163 now passes through line 161 to line 157 and so to the coarse pitch chambers of the actuator. A line 151 extends from the line 150 and in the normal position of the spool 93 connects with the annulus 102. When pitch fining was selected and fluid was passing through line 159 and inlet 160 to the fine pitch chambers of the actuator 20, simultaneously fluid was discharging from the coarse pitch chambers through outlet 158 and line 157 to the annulus 111 of the control valve 90, thence to annulus 112 and line 153 to annulus 50 of control valve 44, thence to annulus 51 and line 165 to return through line 163 and non-return valve 164 to the reservoir 26. When the blades are to be moved to the negative pitch position for aircraft braking, the control tube 104 is moved beyond the "unfeather" position to the "stop withdrawal" position. Thus the cam 106 is moved fully to the left and the valve assembly 143 is lifted to close the outlet 147 and to open the inlet 146. Thus pressure fluid in lines 167, 168 now passes through the inlet 146 to the line 169 and to the stop withdrawal device 171 whereby the blades move to fine negative pitch.