초록 ▼

A gas turbine engine fuel system of the type using the rotational speed of the high pressure spool as the main control parameter has a trimmer device which reduces the effect of variation of engine geometry in cold starts etc. The trimmer uses the throttle lever angle and engine inlet pressure to co

A gas turbine engine fuel system of the type using the rotational speed of the high pressure spool as the main control parameter has a trimmer device which reduces the effect of variation of engine geometry in cold starts etc. The trimmer uses the throttle lever angle and engine inlet pressure to compute the desired value of a thrust-related parameter such as weighted mean exhaust pressure, this desired value being compared with the actual value to produce a trim input to the main fuel control unit.

대표청구항 ▼

1. A fuel system for a gas turbine engine of the type having a high pressure spool, means for producing signals proportional to the rotational speed of the high pressure spool, engine inlet pressure and at least one other parameter uniquely related to the thrust produced by the engine, a thottle lev

1. A fuel system for a gas turbine engine of the type having a high pressure spool, means for producing signals proportional to the rotational speed of the high pressure spool, engine inlet pressure and at least one other parameter uniquely related to the thrust produced by the engine, a thottle lever for selecting a desired value of engine thrust and a main fuel control unit for adjusting the fuel flow to the engine in accordance with the throttle lever angle and the measured rotational speed of the high pressure spool so as approximately to produce the desired thrust, and a trimmer for determining from the throttle lever angle and said engine inlet pressure the desired value of said other parameter, comparing the computed value with the measured value, and applying a trimming input to the main fuel control unit to trim this unit in accordance with the input to provide a fuel flow to the engine which causes the engine to produce the desired engine thrust. 2. A fuel system as claimed in claim 1 and in which said other parameter comprises the jet pipe pressure. 3. A fuel system as claimed in claim 1 and in which said other parameter comprises a weighted mean of the fan outlet pressure and the core exhaust pressure. 4. A fuel system as claimed in claim 1 and in which said other parameter comprises the delivery pressure of the high pressure compressor of the engine. 5. A fuel system as claimed in claim 1 and in which said trimmer comprises a three-dimensional cam by which the signals from said means for producing signals responsive to engine inlet pressure and the value of the throttle lever setting are integrated to calculate a desired value of said other parameter. 6. A fuel system as claimed in claim 5 and in which the inputs to said three-dimensional cam separately effect axial translation and rotation of the cam. 7. A fuel system as claimed in claim 5 comprising a lever system for comprising the desired value of the other parameter with the actual value and for providing a mechanical trim for the main fuel control unit. 8. A fuel system as claimed in claim 7 and in which said lever system comprises a lever having two extremities and an intermediate pivot point, and linkages which transmit the output from said three-dimensional cam to one said extremity, a motion responsive to said other parameter to said pivot, and the motion of said other extremity to said main fuel control unit as a mechanical trim. 9. A fuel system as claimed in claim 1 and comprising means for providing zero trim to the main control unit below a predetermined desired value of engine thrust. 10. A fuel system as claimed in claim 9 and in which said means comprises a three-dimensional cam by which the setting of said throttle lever angle and said signal responsive to engine inlet pressure are combined to produce a calculated value of said other parameter, said cam being shaped to provide zero trim below a predetermined desired value of engine thrust.