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This invention relates to a fuel injection system for a staged combustion chamber (1) of a gas turbine aero-engine, in which a certain quantity of fuel is permanently supplied to the pilot burner(s) (3) and in which fuel is apportioned to the main burner(s) (4) only at higher engine performance, whe

This invention relates to a fuel injection system for a staged combustion chamber (1) of a gas turbine aero-engine, in which a certain quantity of fuel is permanently supplied to the pilot burner(s) (3) and in which fuel is apportioned to the main burner(s) (4) only at higher engine performance, whereby a staging valve unit (7) which variably splits the total fuel mass flow (WF) to the pilot burners (3) and to the main burners (4) is provided downstream of a control valve unit (6) which controls the entire fuel mass flow, with both valve units being actuated by an engine control unit (8) and with the actuation of the staging valve unit (7) being accomplished on the basis of the desired engine performance, characterized in that the engine performance is described by way of a staging parameter (SP) reflecting the load of the gas turbine combustion chamber (1) and actuating the staging control unit ( 7) according to a switching line, in that the staging parameter (SP) is derived from a functional relationship, in that a downstream summation point is provided for the computation of the difference between an actual value of the staging point and a value of the nominal staging point, and in that a time element (TIMER) is provided subsequent to the summation point, said time element being designed such that switch-over is delayed upon overshooting or undershooting of the adjusted staging point, respectively, if the period since the execution of the previous staging event is smaller than a pre-defined time constant held in a family of characteristics.

대표청구항 ▼

What is claimed is: 1. A fuel injection system for a staged combustion chamber of a gas turbine engine, comprising: a control valve unit for variably adjusting a total fuel mass flow (WF) to pilot burners and main burners of the engine; a staging valve unit provided downstream of the control valve

What is claimed is: 1. A fuel injection system for a staged combustion chamber of a gas turbine engine, comprising: a control valve unit for variably adjusting a total fuel mass flow (WF) to pilot burners and main burners of the engine; a staging valve unit provided downstream of the control valve unit for variably splitting the total mass fuel flow (WF) in a staged mode between the pilot burners and the main burners; an engine control unit for controlling the control valve unit and the staging valve unit, the engine control unit controlling the staging valve unit to supply a certain quantity of fuel to the pilot burners under all operating conditions and to supply fuel to the main burners in the staged mode only at higher engine performance; the engine control unit constructed and arranged to calculate a staging parameter (SP) reflecting a load of the combustion chamber based on at least one engine operating parameter and control the staging valve unit to variably split the total mass fuel flow (WF) in the staged mode between the pilot burners and the main burners based on the staging parameter (SP); the engine control unit constructed and arranged to compute a difference between a nominal staging point and an actual staging point at a summation step to determine in which of the staged mode and a non-staged mode the engine should operate; and the engine control unit including a timer operating in response to a result from the summation step to delay change between the staged and non-staged mode if a period of time since a previous staging event is smaller than a predetermined time constant. 2. A fuel injection system as in claim 1, wherein the timer is constructed and arranged to actuate when the actual value of the staging point is 1. 3. A fuel injection system as in claim 1, wherein the engine control unit includes an operating characteristics-based control to control the timer. 4. A fuel injection system as in claim 3, wherein the operating characteristics-based control is constructed and arranged to output a control parameter tMIN,staging to the timer. 5. A fuel injection system as in claim 4, wherein the engine control unit is constructed and arranged to set the control parameter small for rapid load changes and large for slow load changes. 6. A fuel injection system as in claim 5, wherein the engine control unit is constructed and arranged to input a time derivation of a rotational speed of a high-pressure turbine shaft (dNH/dt) to the operating characteristics-based control. 7. A fuel injection system as in claim 6, wherein the engine control unit includes a mode selector element and is constructed and arranged to input an output value SPK* of the timer to the mode selector element. 8. A fuel injection system as in claim 7, wherein the mode selector element is constructed and arranged to select the actual value of the staging point computation when SPK*=0 and the value of a previous time step (Z-1) when SPK*=1. 9. A fuel injection system as in claim 8, wherein the engine control unit is constructed and arranged to derive the staging parameter (SP) from at least one of the following functional relationships: (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (gas temperature at combustion chamber entry T30), [WF/P30쨌T30]; (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (square root of the gas temperature at the combustion chamber entry T30), [WF/P 30쨌(T30)1/2]; (Total fuel mass WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (square root of the quotient of the gas temperature at the combustion chamber entry T30 and the gas temperature at the engine inlet T20), [WF/P30쨌(T 30/T20)1/2]; (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (total temperature T 44 downstream of the high-pressure turbine), [WF/P30쨌T44 ]; and (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (square root of total temperature T44 downstream of the high-pressure turbine), [WF/P 30쨌(T44)1/2]. 10. A fuel injection system as in claim 9, wherein the engine control unit is constructed and arranged to control the main burners to switch on when an adjusted staging point reflecting engine performance rises above the actual staging point and to control the main burners to switch off when the adjusted staging point falls below the actual staging point, the engine control unit being constructed and arranged to derive the adjusted staging point by adding at least one correction element (ΔSP) to the nominal staging point, said correction element reflecting at least one of the following influencing parameters: absolute value of the gas pressure at the combustion chamber entry (P30); absolute value of the gas temperature at the combustion chamber entry (T30); corrected speed of the high-pressure compressor (N2 RT20) and gas pressure at the engine inlet (P20); flight altitude; selected ambient conditions; rate of load change; and compressor surge. 11. A fuel injection system as in claim 10, whereby the engine control unit is constructed and arranged to determine a split value (S) from the staging parameter (SP), the split value describing the fuel apportionment between the pilot burners and the main burners and being used to control the staging valve unit, wherein the engine control unit is constructed and arranged to adjust the split value (S) for transient states of the engine with a correction factor established in dependence on the time derivation of the rotational speed of the high-pressure shaft of the engine. 12. A fuel injection system as in claim 11, wherein the engine control unit is constructed and arranged to substitute a limiting value for the split value if a time-differentiated value of the split value exceeds a limiting differential value. 13. A fuel injection system as in claim 12, wherein the engine control unit is constructed and arranged to preclude a change of an air blood rate of the engine during a staging event in which the main burners are switched between activation and de-activation. 14. A fuel injection system as in claim 13, wherein the engine control unit includes a staging anticipation logic to control the staging valve unit to short-term fill the main burners if their activation is imminent. 15. A fuel injection system as in claim 14, wherein the engine control unit is constructed and arranged to control the staging valve unit to fill fuel lines to the main burners and fuel lines to the pilot burners during start-up of the engine without measuring a filling state in the main burner filet lines. 16. A fuel injection system as in claim 1, wherein the engine control unit is constructed and arranged to derive the staging parameter (SP) from at least one of the following functional relationships; (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (gas temperature at combustion chamber entry T30), [WF/P30쨌T30]; (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (square root of the gas temperature at the combustion chamber entry T30), [WF/P 30쨌(T30)1/2]; (Total fuel mass WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (square root of the quotient of the gas temperature at the combustion chamber entry T30 and the gas temperature at the engine inlet T20), [WF/P30쨌(T 30/T20)1/2]; (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (total temperature T 44 downstream of the high-pressure turbine), [WF/P30쨌T44 ]; and (Total fuel mass flow WF) divided by (gas pressure at combustion chamber entry P30) multiplied by (square root of total temperature T44 downstream of the high-pressure turbine), [WF/P 30쨌(T44)1/2]. 17. A fuel injection system as in claim 1, wherein the engine control unit is constructed and arranged to control the main burners to switch on when an adjusted staging point reflecting engine performance rises above the actual staging point and to control the main burners to switch off when tie adjusted staging point falls below the actual staging point, the engine control unit being constructed and arranged to derive the adjusted staging point by adding at least one correction element (ΔSP) to the nominal staging point, said correction element reflecting at least one of the following influencing parameters: absolute value of the gas pressure at the combustion chamber entry (P30); absolute value of the gas temperature at the combustion chamber entry (T30); corrected speed of the high-pressure compressor (N2 RT20) and gas pressure at the engine inlet (P20); flight altitude; selected ambient conditions; rate of load change; and compressor surge. 18. A fuel injection system as in claim 1, whereby the engine control unit is constructed and arranged to determine a split value (S) from the staging parameter (SP), the split value describing the fuel apportionment between the pilot burners and the main burners and being used to control the staging valve unit, wherein the engine control unit is constructed and arranged to adjust the split value (S) for transient states of the engine with a correction factor established in dependence on the time derivation of the rotational speed of the high-pressure shaft of the engine. 19. A fuel injection system as in claim 1, wherein the engine control unit is constructed and arranged to preclude a change of an air bleed rate of the engine during a staging event in which the main burners are switched between activation and de-activation. 20. A fuel injection system as in claim 1, wherein the engine control unit includes a staging anticipation logic to control the staging valve unit to short-term fill the main burners if their activation is imminent. 21. A fuel injection system as in claim 1, wherein the engine control unit is constructed and arranged to control the staging valve unit to fill fuel lines to the main burners and fuel lines to the pilot burners during start-up of the engine without measuring a filling state in the main burner fuel lines.