Abstract:
A method for assembling a gas turbine engine is described. The method includes coupling a first fuel system interface (FSI-1) to a second fuel system interface (FSI-2), and coupling one of the FSI-1 and the FSI-2 to the engine. The method includes coupling a first control system and a second control system to the FSI-1 and to the FSI-2. The first control system includes a first driver A and a second driver A, and the second control system includes a first driver B and a second driver B. The method includes configuring the first control system and the second control system to apply a first over-speed logic algorithm and a second over-speed logic algorithm to determine operation of the first driver A, the second driver A, the first driver B, and the second driver B.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH &amp; DEVELOPMENT 
       [0001]    The U.S. Government may have certain rights in this invention as provided for by the terms of Contract No. N00019-04-C-0093. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The field of the disclosure relates generally to gas turbine engine rotors and, more particularly, to fuel system interfaces used to prevent rotor over-speed conditions. 
         [0003]    Gas turbine engines typically include over-speed protection systems that provide rotor over-speed protection. In known systems, the over-speed protection systems either maintains the rotor speed below critical rotor speeds, or shuts off fuel flow to an engine combustor. One type of known protection system receives signals, indicative of rotor speed, from mechanical speed sensors. The mechanical speed sensors include rotating flyweight sensing systems that indicate an over-speed condition as a result of the rotor rotating above the normal operational maximum speeds. The flyweight sensing systems are hydro-mechanically coupled to a fuel bypass valve that reduces an amount of fuel that can be supplied to the engine if an over-speed condition is sensed. 
         [0004]    Other types of known over-speed protection systems receive over-speed signal information from electronic control sensors. Known electronic controls derive over-speed conditions from such electronic control sensors. Such systems provide for rapid fuel shutoff and engine shutdown if engine speed exceeds a normal maximum value. 
         [0005]    In some known aircraft, propulsion systems are used to control a flow of exhaust gases for a variety of aircraft functions. For example, such systems can be used to provide thrust for Vertical Take-Off and Landing (VTOL), Short Take-Off Vertical Landing (STOVL) and/or Extreme Short Take-Off and Landing (ESTOL) aircraft. At least some known STOVLs and ESTOLs use vertical thrust posts that facilitate short, and extremely short, take-offs and landings. In aircraft using vertical thrust posts or nozzles, exhaust from a common plenum is channeled to thrust posts during take-off and landing operations, and, at a predetermined altitude, the exhaust is channeled from the common plenum through a series of valves, to a cruise nozzle. 
         [0006]    At least some known gas turbine engines include combustion control systems that include symmetric channels for providing electric signals to the control system. However, such channels may allow common design deficiencies in each channel to cause transients during operation of the control system and/or gas turbine engine. For example, at least one such known combustion control system is an over-speed system that protects an airframe and/or a pilot from turbine and/or compressor wheel transients caused by a rotational speed over the design limits of a turbine and/or a compressor. More specifically, when the rotational speed is over a design limit, the over-speed system will shut down the gas turbine engine by preventing fuel from flowing to the engine. As such, the over-speed system can prevent turbine and/or compressor wheel transients from occurring. 
         [0007]    However, if the circuitry within full authority digital engine controls (FADECs) that control such an over-speed system have a common design deficiency, both channels of the FADECs may inadvertently command the over-speed system to prevent fuel from flowing to the engine, even though a rotational speed in excess of a design limit has not been reached, causing an unexpected engine shut down. Accordingly, it is desirable to have a combustion control system that will not inadvertently shut down a gas turbine engine when operating conditions are within design limits. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    In one aspect, a method for assembling a gas turbine engine is provided. The method includes coupling a first fuel system interface (FSI-1) to a second fuel system interface (FSI-2) and coupling one of the FSI-1 and the FSI-2 to the gas turbine engine. The method also includes coupling a first control system to the FSI-1 and to the FSI-2, and coupling a second control system to the FSI-1 and to the FSI-2. The first control system includes a first driver A and a second driver A and the second control system includes a first driver B and a second driver B. The method also includes configuring the first control system to apply a first over-speed logic algorithm to determine operation of at least one of first driver A, second driver A, first driver B, and second driver B, and to apply a second over-speed logic algorithm to determine operation of at least one of first driver A, second driver A, first driver B, and second driver B. The method also includes configuring the second control system to apply the first over-speed logic algorithm to determine operation of at least one of first driver A, second driver A, first driver B, and second driver B, and to apply the second over-speed logic algorithm to determine operation of at least one of first driver A, second driver A, first driver B, and second driver B. 
         [0009]    In another aspect, an over-speed protection system for a gas turbine engine including a rotor is provided. The over-speed protection system includes a fuel throttling/shutoff valve coupled to a fuel supply coupled to the gas turbine engine, a first fuel system interface (FSI-1) coupled to the fuel throttling/shutoff valve, and a second fuel system interface (FSI-2) coupled to the FSI-1. The system also includes a first control system coupled to the FSI-1 and to the FSI-2. The first control system includes a first driver A and a second driver A and is programmed with a first logic algorithm and a second logic algorithm. The system also includes a second control system coupled to the FSI-1 and the FSI-2. The second control system includes a first driver B and a second driver B and is programmed with the first logic algorithm and the second logic algorithm. 
         [0010]    In yet another aspect, a gas turbine engine is provided. The gas turbine engine includes a rotor, a fuel delivery system configured to supply fuel to the engine for operating the rotor, and an over-speed protection system coupled to the fuel delivery system. The over-speed protection system includes a fuel throttling/shutoff valve coupled to the fuel delivery system, a first fuel system interface (FSI-1) coupled to the fuel throttling/shutoff valve, and a second fuel system interface (FSI-2) coupled to the FSI-1. The over-speed protection system also includes a first control system coupled to the FSI-1 and to the FSI-2. The first control system includes a first driver A and a second driver A and is programmed with a first logic algorithm and a second logic algorithm. The over-speed protection system also includes a second control system coupled to the FSI-1 and the FSI-2. The second control system includes a first driver B and a second driver B and is programmed with the first logic algorithm and the second logic algorithm. 
         [0011]    Accordingly, the embodiments described herein facilitate preventing inadvertent gas turbine engine shut down by including the above-described features. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine. 
           [0013]      FIG. 2  is a schematic illustration of an exemplary rotor over-speed protection system that may be used with the gas turbine engine shown in  FIG. 1 . 
           [0014]      FIG. 3  is a priority logic table that may be used with the rotor over-speed protection system shown in  FIG. 2 . 
           [0015]      FIG. 4  is a schematic illustration of an exemplary control system coupled to the rotor over-speed protection system shown in  FIG. 2 . 
           [0016]      FIG. 5  is a schematic illustration of the control system shown in  FIG. 4  and coupled to a plurality of independent over-speed sensors. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Identifying and preventing rotor over-speed conditions is critical due to damage that may occur to an engine should a rotor speed exceed a maximum speed. It is also desirable to minimize false determinations of over-speed conditions. Minimizing false determinations of over-speed conditions is especially important in single-engine aircraft, where determination and action to facilitate prevention of a rotor over-speed condition may lead to the loss of an aircraft. 
         [0018]    Accordingly, it is desirable to have a rotor over-speed protection system that does not allow common design deficiencies in each symmetric channel to cause transients during operation of a control system and/or a gas turbine engine. For example, in one embodiment, the over-speed protection system includes multiple differing fuel system interfaces, and as such, does not include common design deficiencies. In another example, an over-speed protection system includes a control system that has asymmetric driver circuits. The embodiments described herein include two different driver circuits and, more particularly, a torque motor driver circuit and a solenoid driver circuit used for controlling combustion within a gas turbine engine. In yet another example, an over-speed protection system includes a control system that includes a plurality of independent logic algorithms. 
         [0019]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine  10  that includes a low pressure compressor  12 , a high pressure compressor  14 , and a combustor  16 . Engine  10  also includes a high pressure turbine  18 , and a low pressure turbine  20 . Compressor  12  and turbine  20  are coupled by a first rotor shaft  24 , and compressor  14  and turbine  18  are coupled by a second rotor shaft  26 . In operation, air flows through low pressure compressor  12  and compressed air is supplied from low pressure compressor  12  to high pressure compressor  14 . Compressed air is then delivered to combustor  16  and airflow from combustor  16  drives turbines  18  and  20 . 
         [0020]      FIG. 2  is a schematic illustration of an exemplary rotor over-speed protection system  40  for use with example, engine  10 , for example. In the exemplary embodiment, engine  10  includes a fuel metering system  42  that is in flow communication with a fuel delivery system  44 . Fuel metering system  42  includes a fuel metering valve  46  and a fuel throttling/shutoff valve  50 . Fuel delivery system  44  supplies fuel to engine  10  through fuel metering system  42 , which controls a flow of fuel to engine  10 . Fuel throttling/shutoff valve  50  is downstream from fuel metering valve  46  and receives fuel flow from fuel metering valve  46 . In one embodiment, fuel throttling/shutoff valve  50  is a pressurizing shutoff valve. 
         [0021]    In the exemplary embodiment, fuel throttling/shutoff valve  50  is coupled downstream from fuel metering valve  46  and in flow communication with fuel delivery system  44 . Fuel throttling/shutoff valve  50  is coupled to fuel metering valve  46  by a fuel line  52 . A separate fuel line  54  couples throttling/shutoff valve  50  to combustor  16  to enable fuel throttling/shutoff valve  50  to modulate and to control a flow of fuel to combustor  16  based on a pressure of the fuel received by fuel throttling/shutoff valve  50  and a desired discharge pressure. The throttling/shutoff valve  50  operates in conjunction with fuel metering valve  46  to facilitate metered fuel flow during nominal operation. The throttling function of valve  50  responds to fuel metering valve  46  to maintain a constant pressure drop across fuel metering valve  46  and deliver a fuel flow to combustor  16  that is proportional to an orifice area of fuel metering valve  46 . 
         [0022]    During operation, rotor over-speed protection system  40  facilitates preventing engine rotors, such as turbines  18  and  20  (shown in  FIG. 1 ), from operating at a speed that is greater than a pre-set operational maximum speed, known as an over-speed condition. Additionally, system  40  facilitates preventing either engine rotors from accelerating to a speed that is greater than a pre-set operational maximum speed, known as an over-speed condition, when an engine independent speed sensing system (not shown in  FIG. 2 ) determines normal engine operating limits have been exceeded. Moreover, system  40  facilitates preventing engine rotors from accelerating to a boost that is greater than a pre-set operational maximum boost, known as an over-boost condition, when an engine independent sensing system (not shown in  FIG. 2 ) determines normal engine operating limits have been exceeded. 
         [0023]    In the exemplary embodiment, rotor over-speed protection system  40  includes a first fuel system interface  56  and a second fuel system interface  58 . Second fuel system interface  58  is coupled in series between throttling/shutoff valve  50  and first fuel system interface  56 . Control lines  64  and  68  couple first fuel system interface  56  to second fuel system interface  58 , and couple second fuel system interface  58  to throttling/shutoff valve  50 , respectively. First fuel system interface  56  and second fuel system interface  58  provide a control pressure to throttling/shutoff valve  50 . In the exemplary embodiment, first fuel system interface  56  includes an over-speed servovalve  70  and a shutoff shuttle valve  74 . Moreover, in the exemplary embodiment, second fuel system interface  58  includes an over-speed servovalve  78  and a shutoff shuttle valve  80 . In the exemplary embodiment, servovalves  70  and  78  are electro-hydraulic servovalves (EHSV). Alternatively, other types of servovalves may be used that enable rotor over-speed protection system  40  to function as described herein. For example, a solenoid, or combination of solenoid &amp; EHSV, arranged in series, may be used to perform the function of the EHSV. Although described herein as an over-speed protection system, over-speed protection system  40  may also facilitate preventing over-boost conditions using the systems and methods described herein. 
         [0024]    In the exemplary embodiment, rotor over-speed protection system  40  provides an independent and a secondary means of over-speed detection and fuel flow control to supplement the fuel flow control provided by fuel metering valve  46  and fuel throttling/shutoff valve  50 . Servovalve  78  is coupled to at least one independent sensing system (shown in  FIGS. 4 and 5 ) and as such, receives over-speed indications from at least one independent sensing system. Moreover, servovalve  70  is coupled to at least one independent sensing system and receives electrical over-speed indications from at least one independent sensing system. 
         [0025]      FIG. 3  illustrates a priority logic table  90  of an exemplary relationship between fuel metering valve  46  and over-speed protection system  40 . As described above, if fuel metering valve  46  determines a rotor over-speed condition has occurred, fuel metering valve  46  and fuel throttling/shutoff valve  50  prevent fuel flow to combustor  16 . Table  90  illustrates that when fuel metering valve  46  and fuel throttling/shutoff valve  50  cease fuel flow to combustor  16 , combustor  16  is not supplied fuel to prevent damage to engine  10 . However, in the exemplary embodiment, as an additional layer of over-speed protection, fuel flow to combustor  16  may also be discontinued by throttling/shutoff valve  50  upon a determination of an over-speed condition by first fuel system interface  56  and second fuel system interface  58 . This additional layer of over-speed protection may prevent an over-speed condition from damaging engine  10  in the event that fuel metering valve  46  becomes inoperable or malfunctions. For example, if a contaminant causes fuel metering valve  46  to remain in an “open” state (i.e., allowing fuel flow to combustor  16 ), even though valve  46  determines the occurrence of an over-speed condition, fuel system interfaces  56  and  58  detect the over-speed condition and prevent potential damage to engine  10 . 
         [0026]    As is shown in table  90 , fuel flow is only discontinued when both fuel system interface  56  and fuel system interface  58  sense the occurrence of an over-speed condition. As described above, throttling/shutoff valve  50  controls a fuel pressure provided to combustor  16 , and closes (i.e., discontinues fuel flow to combustor  16 ) when first fuel system interface  56  and second fuel system interface  58  sense an over-speed condition. 
         [0027]    Priority logic table  90  illustrates the conditions under which engine fuel flow may be initiated in light of the various combinations of signals affecting fuel metering valve  46 , fuel throttling/shutoff valve  50 , over-speed protection system  40 , and throttling/shutoff valve  50 . More specifically, priority logic table  90  provides that when fuel throttling/shutoff valve  50  is activated, as a result of receipt of a signal indicating an over-speed condition, fuel flow can only be initiated when the over-speed signal is removed. 
         [0028]    In the exemplary embodiment, servovalve  78  opens shuttle valve  80  upon receipt of a signal indicating the occurrence of an over-speed condition. Such a signal may be provided by a logic control system (shown in  FIG. 5 ), described in more detail below. However, shuttle valve  80  alone will not cause throttling/shutoff valve  50  to discontinue fuel flow to combustor  16 . Rather, servovalve  70  opens shuttle valve  74  upon receipt of a signal indicating the occurrence of an over-speed condition. Because first fuel system interface  56  and second fuel system interface  58  are coupled together in series, only when both shuttle valves  74  and  80  are open, will a control pressure be provided to throttling/shutoff valve  50  that causes throttling/shutoff valve  50  to close and discontinue fuel flow to combustor  16 . By requiring an over-speed determination from both first fuel system interface  56  and second fuel system interface  58 , the probability of a false determination of an over-speed condition is facilitated to be reduced. As such, undesirable and inadvertent engine shut downs based on false indications are also facilitated to be reduced. 
         [0029]      FIG. 4  is a schematic illustration of an exemplary control system  100  coupled to rotor over-speed protection system  40 . Alternatively, control system  100  may be integrated into over-speed protection system  40 . In the exemplary embodiment, control system  100  includes a first driver control system  102  and a second driver control system  104 . In the exemplary embodiment, first driver control system  102  and second driver control system  104  are full authority digital electronic controls (FADEC), which are commercially available from General Electric Aviation, Cincinnati, Ohio. 
         [0030]    In the exemplary embodiment, first driver control system  102  includes a first driver A  106  and a second driver A  108 . In an alternative embodiment, first driver control system  102  is coupled to first driver A  106  and second driver A  108 . First driver control system  102  is programmed with software that includes a first logic algorithm and a second logic algorithm. In the exemplary embodiment, first driver A  106  is a solenoid current driver and second driver A  108  is a torque motor current driver. As such, deficiencies in first driver A  106  are not repeated in the second driver A  108  because first driver A  106  and second driver A  108  are different types of drivers. In an alternative embodiment, first driver A  106  is a first suitable type of driver, and second driver A  108  is a second suitable type of driver that is different than the first type of driver such that each driver A  106  and  108  is controlled using different logic and/or outputs. 
         [0031]    In the exemplary embodiment, second driver control system  104  includes a first driver B  110  and a second driver B  112 . In an alternative embodiment, second driver control system  104  is coupled to first driver B  110  and second driver B  112 . Second driver control system  104  is programmed with software that includes the first logic algorithm and the second logic algorithm. More specifically, in the exemplary embodiment, first driver B  110  is a solenoid current driver and second driver B  112  is a torque motor current driver. As such, deficiencies in first driver B  110  are not repeated in the second driver B  112  because first driver B  110  and second driver B  112  are different types of drivers. In an alternative embodiment, first driver B  110  is a first suitable type of driver, and second driver B  112  is a second suitable type of driver that is different than the first type of driver such that each driver B  110  and  112  is controlled by different logic and/or outputs. In the exemplary embodiment, first driver A  106  and first driver B  110  are the same type of driver, and second driver A  108  and second driver B  112  are the same type of driver. 
         [0032]    In the exemplary embodiment, engine  10  includes a sensor system, such as a sensor system  114  that senses an over-speed condition within engine  10 . More specifically, sensor system  114  includes at least one speed sensor that measures a rotational speed of either first rotor shaft  24  (shown in  FIG. 1 ) and/or second rotor shaft  26  (shown in  FIG. 1 ). As such, sensor system  114  outputs the rotational speed of rotor shaft  24  and/or rotor shaft  26  as an electric speed signal. Specifically, the electronic speed signal is transmitted from sensor system  114  to control system  100 , which includes logic to determine if the speed signal is indicative of an over-speed condition. More specifically, the speed signal is transmitted to first driver control system  102  and second driver control system  104 , such that first driver A  106 , second driver A  108 , first driver B  110 , and second driver B  112  each receive the transmitted speed signal to determine whether an over-speed condition exists. 
         [0033]    First driver control system  102  is coupled to first fuel system interface  56  and second fuel system interface  58 , and second driver control system  104  is coupled to first fuel system interface  56  and second fuel system interface  58  for transmitting an over-speed signal thereto. More specifically, each driver control system  102  and  104  must independently determine that an over-speed condition exists for an over-speed signal to be transmitted to either first fuel system interface  56  and/or second fuel system interface  58 . In the exemplary embodiment, first driver A  106  is communicatively coupled to first fuel system interface  56 , second driver A  108  is communicatively coupled to second fuel system interface  58 , first driver B  110  is communicatively coupled to first fuel system interface  56 , and second driver B  112  is communicatively coupled to second fuel system interface  58 . As such, first drivers  106  and  110  are coupled to first fuel system interface  56 , and second drivers  108  and  112  are coupled to second fuel system interface  58 . More specifically, in the exemplary embodiment, solenoid current drivers are coupled to first fuel system interface  56 , and torque motor current drivers are coupled to second fuel system interface  58 . 
         [0034]    When the speed signal transmitted from sensor system  114  is indicative of an over-speed condition, each driver  106 ,  108 ,  110 , and  112  transmits an over-speed signal to a respective fuel system interface  56  or  58 . More specifically, in the exemplary embodiment, both first drivers  106  and  110  transmit an over-speed signal to first fuel system interface  56  to open shuttle valve  74 , and both second drivers  108  and  112  transmit an over-speed signal to second fuel system interface  58  to open shuttle valve  80 . If the speed signal is not indicative of an over-speed condition, a deficiency in first drivers  106  and  110  or in second drivers  108  and  112  may cause an over-speed signal to be transmitted to a respective fuel system interface  56  or  58 . However, such a driver operational transient signal will not prevent fuel from flowing to combustor  16  because both fuel system interfaces  56  and  58  must receive an over-speed signal before fuel is prevented from flowing to combustor  16 . As such, the non-symmetry of first drivers  106  and  110  and second drivers  108  and  112  provides an additional safety redundancy before fuel is prevented from flowing to combustor  16 . 
         [0035]      FIG. 5  is a schematic illustration of control system  100  coupled to a plurality of independent over-speed sensors  220  and  222 . As described above, control system  100  includes first driver control system  102  and second driver control system  104 . 
         [0036]    In the exemplary embodiment, first driver control system  102  includes first driver A  106  and second driver A  108  and is programmed with software that includes a first logic algorithm and a second logic algorithm. Moreover, in the exemplary embodiment, first driver A  106  is controlled according to an output of the first logic algorithm and second driver A  108  is controlled according to an output of the second logic algorithm. 
         [0037]    Similarly, in the exemplary embodiment, second driver control system  104  is coupled to first driver B  110  and second driver B  112  and is programmed with software that includes the first logic algorithm and the second logic algorithm. In the exemplary embodiment, first driver B  110  is controlled according to an output of the first logic algorithm and second driver B  112  is controlled according to an output of the second logic algorithm. 
         [0038]    In the exemplary embodiment, the first logic algorithm uses, for example, different methodologies, calculations, and/or over-speed thresholds than the second logic algorithm to determine the occurrence of an over-speed condition. In one embodiment, first logic algorithm and second logic algorithm are developed such that deficiencies, for example software defects, included in either logic algorithm are not included in the other logic algorithm. Moreover, two independent logic algorithms facilitate reducing the risk that a single, common software fault may inadvertently cause over-speed protection system  40  to unnecessarily stop fuel flow to combustor  16 . 
         [0039]    Additionally, in the exemplary embodiment, first driver control system  102  is coupled to a first set of over-speed sensors  220  and to a second set of over-speed sensors  222 . Over-speed sensors  220  are separate, and function independently from over-speed sensors  222 . Moreover, over-speed sensors  220  and  222  are positioned within engine  10  to measure engine operating parameters and to provide first and second driver control systems  102  and  104  with engine operating information. In the exemplary embodiment, first driver control system  102  controls operation of first driver A  106 , and uses the first logic algorithm to identify a rotor over-speed condition. First driver control system  102  executes the first logic algorithm to identify a rotor over-speed condition and controls operation of first driver A  106  accordingly. The first logic algorithm determines the desired operation of first driver A  106  based on engine operating measurements provided by first set of logic sensors  220 . 
         [0040]    In the exemplary embodiment, first driver control system  102  controls a state of second driver A  108  by executing the second logic algorithm, and bases a determination of the occurrence of a rotor over-speed condition and desired operation of second driver A  108  on engine operating measurements provided by second logic sensors  222 . 
         [0041]    Similarly, second driver control system  104  is coupled to over-speed sensors  220  and to over-speed sensors  222 . In the exemplary embodiment, second driver control system  104  controls operation of first driver B  110  and uses the first logic algorithm to identify an over-speed condition. Second driver control system  104  executes the first logic algorithm to identify a rotor over-speed condition, and controls operation of first driver B  110  accordingly. The first logic algorithm uses engine operating information provided from first set of logic sensors  220  to determine the desired operation of first driver B  110 . 
         [0042]    In the exemplary embodiment, second driver control system  104  controls a state of second driver B  112  by executing the second logic algorithm, and bases a determination of the occurrence of an over-speed condition and the desired operation of second driver B  112  on engine operating measurements provided by second logic sensors  222 . 
         [0043]    In the exemplary embodiment, before first driver control system  102  can signal an over-speed condition that would cause over-speed protection system  40  to stop fuel flow to combustor  16 , the first logic algorithm must determine that an over-speed condition is occurring based on engine operating information provided by first set of logic sensors  220 , and the second logic algorithm must also determine that an over-speed condition is occurring based on engine operating information provided by second set of logic sensors  222 . Moreover, first driver control system  102  cannot cause over-speed protection system  40  to stop fuel flow without second driver control system  104  also signaling the occurrence of an over-speed condition. However, for second driver control system  104  to signal an over-speed condition, the first logic algorithm must determine that an over-speed condition is occurring based on engine operating information provided by first set of logic sensors  220 , and the second logic algorithm must also determine that an over-speed condition is occurring based on engine operating information provided by second set of logic sensors  222 . 
         [0044]    As described above, logic sensors  220  are separate, and operate independently from logic sensors  222 . By independently measuring engine operating parameters, false over-speed determinations caused by, for example, a malfunctioning sensor, are facilitated to be reduced. Furthermore, by analyzing the engine operating information provided by logic sensors  220  and  222 , in two separate driver control systems  102  and  104 , false over-speed determinations caused by, for example, a malfunctioning driver control system, are facilitated to be reduced. Moreover, by programming each of first driver control system  102  and second driver control system  104  with two independent logic algorithms, false over-speed determinations caused by, for example, a single software fault, are facilitated to be reduced. 
         [0045]    The rotor over-speed protection system as described above includes an integrated throttling/shutoff system. The systems and methods described herein are not limited to a combined throttling/shutoff system, but rather, the systems and methods may be implemented as a separate shutoff system, distinct from the fuel metering and throttling functions. Further, the specific embodiments may be implemented into a bypass type of fuel metering system, as well as into a direct injection type of system that does not include a separate metering/throttling function. 
         [0046]    The above-described rotor over-speed protection system is highly fault-tolerant and robust. The rotor over-speed protection system facilitates a rapid fuel shutoff to prevent damage to an engine caused by a rotor over-speed. Additionally, the above-described rotor over-speed protection system addresses a number of potential causes of false over-speed determinations to facilitate preventing unnecessary, and potentially costly, fuel shutoffs due to false over-speed determinations. The above-described rotor over-speed protection system facilitates preventing common deficiencies, for example, common design deficiencies and/or common component failure deficiencies, from causing an unnecessary fuel shutoff due to a false over-speed determination. As a result, the rotor over-speed protection system prevents rotor over-speeds in a cost-effective and reliable manner. 
         [0047]    The above-described rotor over-speed protection system includes a first fuel system interface and a second fuel system interface that provide redundant over-speed protection to, for example, an engine that includes a first form of over-speed protection, such as, a fuel metering system. By requiring an over-speed determination be made by both fuel system interfaces before fuel flow to the engine is discontinued, the above-described rotor over-speed protection system facilitates reducing the probability of a false determination of an over-speed condition. 
         [0048]    Further, the above-described rotor over-speed protection system includes a current driver system that has an asymmetric driver configuration that facilitates reducing the impact of a deficiency within a driver of the current driver system. More specifically, the current driver system includes first and second solenoid current drivers that are coupled to a first fuel system interface, and first and second torque motor current drivers that are coupled to a second fuel interface. As such, a false positive initiated by either one of the drivers will not prevent fuel from flowing to a combustor. Accordingly, the asymmetric driver configuration of the current driver system facilitates preventing inadvertent engine shut-downs. By selectively adding asymmetric features into the current driver system at certain critical locations, the possibility of introducing common design deficiencies is facilitated to be reduced because operation of a solenoid driver in one channel and a torque motor driver in the other channel will be required prior to the engine being shut down and therefore, such a design substantially prevents a common design flaw from inadvertently shutting down the engine. 
         [0049]    Further, the above-described rotor includes a first driver control system and a second driver control system that are each coupled to a plurality of independent over-speed sensors. Each driver control system includes at least a first logic algorithm and a second logic algorithm. Two independent logic algorithms facilitate reducing the risk that a single, common software fault may inadvertently cause the over-speed protection system to unnecessarily stop fuel flow to the engine. 
         [0050]    Exemplary embodiments of systems and method for controlling combustion within a gas turbine engine are described above in detail. The systems and method are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the method may be utilized independently and separately from other components and/or steps described herein. For example, the systems and method may also be used in combination with other combustion systems and methods, and are not limited to practice with only the gas turbine engine as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other control applications. 
         [0051]    Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
         [0052]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.