ULTRA LOW COST FUEL CONTROL SYSTEM FOR EXPENDABLE TURBOJET ENGINE

THE KEY TO COST REDUCTION OF THE FUEL CONTROL SYSTEM FOR AN EXPENDABLE TURBOJET ENGINE LIES IN UTILIZING THE PHYSICAL CHARACTERISTICS OF THE GAS TURBINE ENGINE ITSELF, TAKING ADVANTAGE OF EXISTING FEATURES ON BOARD THE MISSILE, AND COMBINING FUNCTIONS AND COMPONENTS AS MUCH AS POSSIBLE. THIS PROPOSAL FOLLOWS SUCH AN APPROACH AND OFFERS SIGNIFICANT REDUCTION IN COMPLEXITY OF THE CONTROL SYSTEM, RESULTING IN SUBSTANTIAL COST AND WEIGHT SAVINGS. IT IS PROPOSED TO DO AWAY WITH THE TRADITIONAL USE OF THE SPEED SENSORS, THERMOCOUPLES, PRESSURE TRANSDUCERS, AND COMPLICATED ELECTRONIC CONTROL UNITS. INSTEAD, MAKE USE OF AN ELECTROHYDRAULIC METERING VALVE, WHICH BY MEANS OF PNEUMATIC FEEDBACK FROM THE ENGINE COMPRESSOR DISCHARGE PRESSURE (PCD) CAN CONTROL THE ACCELERATION AND DECELERATION OF THE ENGINE DURING STARTING AS WELL AS DURING THRUST ADJUSTMENTS. PCD BIAS WILL ALSO PROVIDE AN EFFECTIVE ALTITUDE COMPENSATION. THE FUEL PRESSURE WILL BE PROVIDED BY AN ELASTIC, BLADDER TYPE, ACCUMULATOR; ALSO PRESSURIZED BY PCD. A SIMPLE ANALOG OR DIGITAL MICROCONTROLLER CAN BE USED TO SEQUENCE THE PYROTECHNIC DEVICES DURING START, AND CONVERT THE REQUIRED THRUST SETTINGS INTO SIGNALS FOR THE FUEL METERING VALVE. HOWEVER, BY COMBINING THE ELECTRONIC CONTROL FUNCTIONS WITH THAT OF THE VEHICLE, SUBSTANTIAL COST SAVINGS AND SIMPLIFICATION WILL RESULT. IN ADDITION TO REDUCING COST, THE PROPOSED DESIGN WILL REDUCE THE WEIGHT OF THE FUEL CONTROL SYSTEM RESULTING IN HIGHER THRUST TO WEIGHT RATIO. ALSO, DUE TO THE SIMPLICITY OF THE APPROACH A HIGH RELIABILITY WILL BE ASSURED. ALTHOUGH MOST APPLICATIONS SHALL BE AIMED TOWARD TACTICAL MISSILE USE, PRIVATE AVIATION ENTHUSIASTS HAVE INDICATED INTEREST IN A LOW COST RELIABLE TURBOJET ENGINE FOR SMALL GLIDER PLANE LAUNCHING.