GB944868A - Apparatus for adjusting control members of axial flow machines - Google Patents

Abstract

944,868. Fluid-pressure servomotor control systems. DE HAVILLAND ENGINE CO. Ltd., and DOWTY FUEL SYSTEMS Ltd. April 4,1960, No. 11854/60. Heading G3P. [Also in Division F1] An apparatus for adjusting the inlet guide vanes of an axial flow compressor, for example the compressor of a gas turbine engine, comprises a member 23 pivoted at 24 and carrying a control valve 22. Centrifugal weights 40, driven from the rotor apply a force proportional to speed in one direction to the member 23 while a temperature responsive means 50, subject to the temperature at a selected point of the machine, such as the inlet, applies a force in the opposite direction. The member 23 is also subjected to a balancing force through a spring 52 which is initially adjustable manually by a screw 61. The vanes 9, or other control member of the machine, are adjusted by pistons 1 through bell crank levers 7. The right hand side of the pistons 1 are subjected to a constant pressure supplied through a line 12 while the left hand side of the pistons are subjected to a variable pressure in the line 16. A line 17 receives the supply pressure through an orifice 18 and a branch line 21 containing an orifice 20 leads to a nozzle controlled by the valve 22. The pressure in the line 16 is maintained proportional to the variable pressure in the line 21 by a valve 25 comprising a diaphragm 26 subjected on one side to the pressure in line 21 and a spring loading 28 and on the other side to the pressure in the line 17 such that a valve 29 controls leakage from the line 17 to maintain the proportional pressure in the line and hence in the line 16. Such an arrangement provides rapid movements of the piston 1 in response to movements of the valve 22. In operation a variation in speed or temperature acts on the member 23 to operate the valve 22 which varies the leak from and hence the pressure in the line 21. The pressure in line 17 varies accordingly and the vanes are adjusted. Movement of the vanes acts through levers 58, 57 to rotate a wheel 56, meshing with a sleeve 54, causing adjustment in the balance spring loading 52 in a sense to restore the balance between the forces acting on the member 23.