TURBINE ENGINE PULSED FUEL INJECTION UTILIZING STAGGER INJECTOR OPERATION
A method to control the output of a turbine engine pulses individual fuel injectors completely on and then completely off in selectable groups rather than in unison. The operation of the groups are staggered in time to minimize the periods of no fuel flow to the engine. Simplicity in the control of individual injectors is achieved by electrically controlling individual injectors rather than mechanically controlling the fuel supplied to all injectors, and, in addition, offers the advantage of minimizing the periods of no fuel flow to maintain combustion stability at low loads. Electrically controlling injectors positioned at the point of fuel usage improves upon fuel atomization and eliminates the problem of unequal distribution of fuel from multiple injection points connected to a common fuel metering system.
Turbine engines currently utilize either a variable continuous stream or a pulsed stream to provide fuel to the engine. The primary objectives of both of these methods are to control the amount of fuel delivered to the engine and to attempt to deliver said fuel in the smallest droplet size, equally dispersed throughout the combustion area to promote rapid and complete combustion of the fuel. The continuous stream method relies upon control of the quantity of fuel delivered to the engine at some arbitrary point upstream of fuel utilization and by mechanical fractionation of the fuel stream while the pulsating injection method as taught by Nearhoof, et. al. in U.S. Pat. No. 6,742,430 (“Fuel Injection Control System for a Turbine Engine”) rapidly turns the fuel on and off at the point of usage to achieve fractionation and control of the combustion process.
The continuous stream method suffers the problems of complexity of the metering equipment, limitations on the final fuel particle size due to utilizing mechanical breakup/dispersion techniques, and slow system response to changing loads due to the mechanical equipment comprising the fuel system. A further limitation of the continuous stream method is in the inherent weight and precision manufacturing tolerances of the necessary metering pump(s) and/or valve(s) to control fuel flow.
The pulsating injection method overcomes the limitations of the continuous stream method by eliminating the precision mechanical controls and the need for mechanical fractionation of the fuel stream but the engine is subject to loss of flame stability at low pulse on-times due to the proportionally long time when no fuel is being supplied during each pulse cycle.
This invention is designed to overcome these limitations by elimination of the mechanical metering equipment such as pumps and valves and by controlling groups of injectors independently rather than pulsing all injectors at the same time. Controlling groups of injectors overcomes the flame stability associated with pulsing all injectors at the same time along with maintaining the response and simplicity of the fuel delivery system lacking in the continuous stream method. The problem of flame stability has previously been overcome by introducing a small quantity of fuel through a continuously fed injector during periods when the main injectors are operating at a low duty cycle or by cycling the main injectors at a relatively high frequency to keep the off-time of each pulse short enough to maintain the combustion process over the more stable continuous stream delivery system. By sequentially operating groups of injectors, the time that the engine's fuel supply is shut off is reduced which allows the frequency of injector pulsing to be reduced to improve upon the overall life of the injectors and elimination of the supplemental continuous injector relied upon to maintain the combustion process.
SUMMARY OF INVENTIONThis invention is an apparatus and method for controlling the injection of fuel in a turbine engine having a combustion chamber. The apparatus comprises at least four fuel injectors arranged and controlled in groups having means for delivering fuel in pulses to said groups of injectors within said combustion chamber of said turbine engine; at least one operating sensor, said sensor having means for receiving sensor signals from a selected operating function of said turbine engine; a programmable electronic control unit for receiving and comparing the value of said sensor signals from said turbine engine to the value of a desired signal, and for generating fuel injector control signals in response thereto; and a means for directing said fuel injector control signals to said fuel injector groups to modify the pulse duration and/or frequency of fuel injection in response to a deviation from a selected operating function, such as the desired engine speed, caused by variable operating loads encountered by the turbine engine. The method for controlling the injection of fuel in a turbine engine having a combustion chamber and having at least four fuel injectors arranged and controlled in groups and at least one sensor for sensing operating signals from said engine comprises the steps of delivering fuel in pulses to said combustion chamber using said injector groups; sensing at least one operating sensor signal from said programmable electronic control unit; at said programmable electronic control unit, comparing the value of said sensor signal to the value of a desired signal and generating fuel injector control signals to each group of said injectors in response to said sensor signal; and directing said fuel injector signals to said fuel injector groups to modify the pulse duration and/or frequency of fuel injection in response to a deviation from desired engine operation caused by variable operating loads encountered by the turbine engine.
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Claims
1. An apparatus for controlling the injection of fuel in a turbine engine having a engine shaft and a combustion chamber, said apparatus comprising:
- a) at least four fuel injectors selectably arranged in independent groups for delivering fuel in pulses to said combustion chamber of said turbine engine;
- b) at least one operating sensor, said sensor having means for receiving sensor signals from a selected operating function of said turbine engine;
- c) a programmable electronic control unit for receiving and comparing the value of said sensor signals from said turbine engine to the value of a desired signal, and for generating fuel injector control signals to said selectable groups of injectors, independently from each other and staggered in time, in response thereto; and
- d) a means for directing said fuel injector control signals to said selected fuel injector groups to modify the pulse duration and/or frequency of said fuel injector groups in response to a deviation from desired engine speeds caused by variable operating loads encountered by said turbine engine.
2. The apparatus of claim 1 wherein said selected fuel injector groups each atomizes the fuel supplied to individual injectors within said group and delivers said fuel in pulses from each injector within said group as a fine mist directly into said combustion chamber at the point of utilization.
3. The apparatus of claim 1 wherein the fuel injectors are selectively divided into groups by the programmable electronic control unit with an equal number of fuel injectors in each group.
4. The apparatus of claim 1 wherein at least one said operating sensor receiving input from a selected operating function of said turbine engine is utilized to control the pulse width and/or frequency of said selected groups of fuel injectors.
5. The apparatus of claim 1 in which the programmable electronic control unit consists of a group comprising a microprocessor and a microcomputer to control said selected injector groups.
6. The apparatus of claim 1 in which the orientation of said selected injectors penetrating said combustion chamber of said turbine is parallel to the axis of said turbine engine's shaft or displaced at some angle from the axis of said turbine shaft.
7. A method for controlling the injection of fuel in pulses by selectable groups of injectors in a turbine engine having a engine shaft and a combustion chamber and having at least four fuel injectors arranged in groups and at least one sensor for sensing operating signals from said engine, said method comprising the steps of:
- a) sensing at least one operating sensor signal from said turbine engine using said sensor;
- b) receiving and comparing with a programmable electronic control unit the value for said sensor signals from said turbine engine to the value of a desired signal and generating with said electronic control unit fuel injector control signals to said selected groups of injectors in response thereto;
- c) directing said fuel injector signals to said selected groups of fuel injectors to modify the pulse duration and/or frequency of fuel injection of said groups independently from each other in response to a deviation from desired engine operating parameters caused by variable operating loads encountered by said turbine engine; and
- c) delivering fuel in pulses to said combustion chamber using said selected groups of fuel injectors;
8. The method of claim 7 wherein said operating sensor signal is generated from a selected parameter of said turbine engine.
9. The method of claim 7 wherein said step of generating control signals to selected groups of injectors by said programmable electronic control unit is accomplished using a pulse width modulation system comprising at least one of a microprocessor and a microcomputer.
10. The method of claim 7 wherein said turbine engine comprises at least two selected groups of fuel injectors utilizing at least two injectors in each group.
11. The method of claim 7 wherein the injectors in each selected group are equally distributed radially around the combustion chamber.
12. The method of claim 7 wherein said selected injectors are arranged to penetrate the combustion chamber of said turbine engine either parallel to the axis of the shaft of said turbine engine or displaced at some angle from the axis of said turbine shaft.
13. The method of claim 7 in which the fuel injector signals to each group are staggered in time.
14. The apparatus of claim 1 in which the injectors in each selected group are equally distributed radially around the combustion chamber.
15. The method of claim 7 in which two groups of fuel injectors are used, when the load is less than 50%, the fuel injectors deliver no fuel to the combustion chamber for short intervals of time.
16. The method of claim 7 in which no fuel is delivered to the combustion chamber for short intervals of time when the load is less than 100%/N where N is the number of injector groups being used.
Type: Application
Filed: Jun 2, 2004
Publication Date: May 15, 2008
Inventor: Kevin P. Pearce (Johnstown, PA)
Application Number: 10/709,877
International Classification: F02C 7/22 (20060101); F02C 7/26 (20060101);