FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1946
1946 - 0068.PDF
FLIGHT JANUARY IOTH, 1940 THE JET-ENGINE FUEL SYSTEM BURNER BURNER Simplified diagramof equip me nt showing connec-tions. balanced, and there is no resulting movement. Should,however, the fluid pressure exceed a value determined by the spring loading of the rocker, the plate valvewill be lilted from its seating and the flow through causes a pressure drop to occur across the restrictingorifice and creates a state of unbalance between the pressures acting on opposite faces of the piston.Under this influence the piston moves to a new posi- tion, reducing the stroke of the plungers and conse-quently the output of the pump. The system is thus safeguarded against the possibly harmful effects ofexcessive pressure. Incorporated in the pump is a hydraulic mechan-ism to limit the pump output, and consequently the engine speed, to a predetermined maximum. In the rotor areseven radial drillings extending from the maximum peri- pheral diameter to an axial bore which is in free communi-cation with the suction chamber of the pump. In operation, centrifugal force produces in the drillings a pressure differ-ence which results in the fuel in the pump casing surround- ing the rotor and also in the space above the diaphragmbeing maintained at a pressure higher than obtains in the suction chamber. This pressure difference isutilised to move the diaphragm, against the constraint of a helical spring in tension,- so that it depresses therocker and unloads the plate -valve. The pump out- fcvolution. On reaching the pump inlet, fuel under pressurefrom the supply pump in the tank passes through a gauze strainer and, by way of the suction port in the valve insert,charges the bore as the plunger moves outwardly. Con- tinued rotation reverses the motion of the plunger, causingthe fuel to be discharged at high pressure through the delivery port of the valve insert. Pressure Control System Parallel with the rotor axis is a bore in which thepressure-control piston operates. The piston rod is con- nected by a link to a lug on the control ring, and concentrichelical springs bias the piston to move the control ring to the position for maximum stroke of the pump and conse-quently maximum output. From the delivery side of the pump, fuel under pressure is applied below the piston inopposition to the springs and also, by way of an adjustable restricting orifice, above the piston. From this space abovethe piston fuel can escape by way of a plate valve which is normally held to its seating by a spring-loaded rocker.By this means the fluid forces acting on the piston are 14 17 11 $ 13 10 Barometric Pressure Control Unit. I, Capsule chamber ; 2, Valve chamber ; 3, Pivot plate ; 4, Rocker ; 5, Half- ball ; 6, Orifice ; 7, Filter ; 8, Diaphragm ; 9, Piston ; 10, Operating rod ; II, Eccentric adjusting sleeve ; 12, Barometric capsule ; 13, Vent to atmosphere. put is then reduced in the manner already described. Thespring loading of the diaphragm is readily adjustable so that the engine speed at which the governing action beginsmay be set with accuracy. The loading of the springs on the control piston opposingthe movement of the cam plate to the zero position is so arranged that the minimum pressure at the burners whenthe governor is in operation is more than adequate to maintain atomisation of the fuel. The possibleextinction of the flame due to x governor action is- thereby prevented. Should the rotational speed of the engine be lowered by "throttling back"and reducing the fuel supply to the burners, the pressure acting on the diaphragm is reduced until Fuel Pump. 1, Plunger ; 2, Rotor ; 3, Carbon bush ; 4, Quill shaft ; 5, Cam plate ; 6, Control ring ; 7, Trunnion pin ; 8, Inlet strainer ; 9, Ported valve insert ; 10, Delivery connection ; II, Pressure control piston ; 12, Restricting orifice ; 13, Plate valve ; 14, Rocker ; 15, Radial holes in rotor ; 16, Dia- ybragm ; 17, Bleed valTft,
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
