Patent Publication Number: US-7917278-B2

Title: System and method for lean blowout protection in turbine engines

Description:
This is a Divisional of application Ser. No. 11/286,246, filed Nov. 22, 2005. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to turbine engines, and more specifically relates to fuel flow control in turbine engines. 
     BACKGROUND OF THE INVENTION 
     Gas Turbine Engines are used in modern aircraft and other vehicles for both propulsion and auxiliary power. They are also commonly used for electricity production. The reliable operation of these turbine engines is of critical importance. Typical gas turbine engines may be automatically controlled via an engine controller such as, for example, a DEEC (Digital Electronic Engine Controller). The engine controller receives signals from various sensors within the engine, as well as from various pilot-manipulated controls. In response to these signals, the engine controller regulates the operation of the gas turbine engine. 
     One issue in maintaining reliability in a turbine engine is avoiding lean blowout (LBO), a condition sometimes also referred to as flame out. In general, lean blowout occurs when the fuel flow falls below the level needed to maintain combustion. When a lean blowout occurs the combustion in the turbine engine ceases until it is restarted using the ignition system. 
     When used for vehicle propulsion the turbine engine must be able to operate over a wide range of speeds and it must be able to change engine speeds at a relatively high rate. For example, the turbine engine must be able to decelerate quickly when needed. This requires that the fuel system be able to reduce fuel flow sufficiently to slow the turbine engine at the needed rate. However, as described above, a low fuel flow can result in a lean blowout, especially when the low fuel flow occurs in a relatively cold engine. Such a lean blowout in a turbine engine is highly undesirable for reliability and safety reasons. 
     To prevent lean blowout, many turbine engines are designed to follow a lean blowout schedule that defines a minimum fuel flow delivered to the turbine engine based on operating conditions. During operation of the turbine engine the commanded fuel flow is maintained above a minimum value, called the lean blowout schedule. The lean blowout schedule is designed to ensure that lean blowout out does not occur in the engine, while still allowing for sufficient control of the turbine engine for low output and/or deceleration. 
     Unfortunately, previous techniques for setting the lean blowout schedule have had significant limitations. For example, previous techniques have used fixed lean blowout schedules. However, due to engine and control system variations and differing atmospheric conditions, these fixed lean blowout schedules can be higher than is required for most situations yet lean blowout can still occur in other situations. Thus, the use of fixed lean blowout schedules has reduced engine speed control and/or has been unable to completely eliminate the possibility of lean blowout. Hence, there remains a need for a system and method for controlling fuel flow in a turbine engine that provides needed engine control while further reducing the possibility of lean blowout. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a turbine engine lean blowout protection system and method that facilitates improved lean blowout protection while providing effective control of turbine engine speed. The lean blowout protection system and method selectively biases the lean blowout (LBO) schedule based on current engine data. Specifically, the system and method adds a gradually increasing positive bias to the LBO schedule when the commanded fuel flow is greater than the LBO schedule by a specified margin. Then, when the commanded fuel flow falls below the margin the system and method gradually decreases the positive bias until the commanded fuel flow reaches the LBO schedule. The increasing and decreasing of the LBO bias provides a selectively increased LBO schedule that improves lean blowout protection while maintaining fuel flow control ability to decelerate the engine. Furthermore, the gradual nature of the LBO biasing helps assure that lean blowout is prevented while allowing the LBO schedule to return to the low, unbiased value if needed to attain low engine output (such as idle). The slower power or speed reduction to idle is small and is normally acceptable and preferable to lean blowout. 
     In one embodiment, the LBO bias is selectively disabled in certain circumstances to provide improved engine control in these circumstances. For example, the LBO bias can be selectively disabled in takeoff situations to facilitate a fast response in the event of a rejected takeoff Furthermore, the LBO bias can be selectively disabled during engine startup to facilitate low fuel flow during startup to avoid hot starts. In both deceleration from takeoff power and starting lean blowout is not likely. Thus, the present invention provides a turbine engine lean blowout protection system and method that facilitates improved lean blowout protection while providing effective control of turbine engine speed and temperature. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The preferred exemplary embodiment of the present invention will hereinafter be described in conjunction with the appended drawings, where like designations denote like elements, and: 
         FIG. 1  is a schematic view of a lean blowout protection system in accordance with an embodiment of the invention; 
         FIG. 2  is a schematic view an exemplary LBO bias mechanism in accordance with an embodiment of the invention; 
         FIG. 3  is a schematic view an exemplary LBO schedule mechanism in accordance with an embodiment of the invention 
         FIG. 4  is a schematic view of an exemplary turbine engine in accordance with an embodiment of the invention; and 
         FIG. 5  is a schematic view of a computer system that includes a lean blowout protection program. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments of present invention provide a turbine engine lean blowout protection system and method that facilitates improved lean blowout protection while providing effective control of turbine engine speed. The lean blowout protection system and method selectively and gradually biases the lean blowout (LBO) schedule based on current engine data. This facilitates improved lean blowout protection while providing effective control of turbine engine speed and temperature. 
     Turning now to  FIG. 1 , a schematic view of a lean blowout protection system  100  is illustrated. The lean blowout protection system  100  includes a LBO schedule mechanism  102  and a LBO bias mechanism  104 . The lean blowout protection system  100  receives temperature data  110 , engine speed data  112 , and commanded fuel flow data  114  and from that data generates an LBO schedule  116 . The LBO schedule  116  defines the minimum fuel flow delivered to the turbine engine. Specifically, during operation of the turbine engine the LBO schedule  116  is used to ensure that the fuel flow to the turbine engine does not go below a level where lean blowout could occur in the turbine engine. The LBO schedule may be defined in fuel flow or other equivalent parameters such as fuel ratios, commonly called WFR. The term fuel ratios may be used synonymously herein with fuel flow. Fuel ratios is defined as fuel flow divided by combustor pressure, both in any convenient units. For example, fuel ratios is commonly defined as fuel flow, in pound per hour divided by combustor absolute pressure in pounds per square inch. 
     In general, the LBO schedule mechanism  102  receives the temperature data  110  and the engine speed data  112  and generates a preliminary LBO value. The LBO bias mechanism  104  receives the engine speed data  112 , the commanded fuel flow data  114 , and a feedback of the current LBO schedule  116 . From this, the LBO bias mechanism  104  selectively biases the preliminary LBO value to generate the LBO schedule  116 . 
     Specifically, the LBO bias mechanism  104  adds a gradually increasing positive bias when the commanded fuel flow is greater than the LBO schedule  116  by a specified margin. Then, when the commanded fuel flow falls below the margin the system and method gradually decreases the positive bias. The increasing and decreasing of the LBO bias provides a selectively increased LBO schedule  116  that improves lean blowout protection while maintaining fuel flow control ability to decelerate the engine. Furthermore, the gradual nature of the LBO biasing provided by the LBO bias mechanism  104  assures that LBO bias persists long enough to prevent lean blowout while allowing the LBO schedule  116  to return to the low, unbiased level to ensure that speed can be reduced to idle. The slower power reduction due to the bias is small and is normally acceptable and preferable to lean blowout. 
     In one embodiment, the LBO bias mechanism  104  selectively disables the bias in certain circumstances to provide improved engine control in these circumstances. For example, the LBO bias mechanism  104  can selectively disable the bias for takeoff situations to facilitate a fast response in the event of a rejected takeoff. Furthermore, the LBO bias mechanism  104  can selectively disable the bias during engine startup to facilitate low fuel flow during startup to avoid hot starts. Thus, the lean blowout protection system  100  with the LBO bias mechanism  104  provides improved turbine engine lean blowout protection while providing effective control of turbine engine speed and temperature. 
     Turning now to  FIG. 2 , a schematic view of an LBO bias mechanism  200  in accordance with one embodiment of the invention is illustrated. The LBO bias mechanism  200  is one example of the type of mechanism that can be used in the lean blowout protection system  100 . In general, the LBO bias mechanism  200  provides a gradually increasing positive bias when the commanded fuel flow is greater than the LBO schedule by a specified margin. Then, when the commanded fuel flow falls below the LBO schedule plus the margin the system and method gradually decreases the positive bias until the commanded fuel flow reaches the LBO schedule. Additionally, the LBO bias mechanism disables the bias during takeoff and engine startup. 
     The LBO bias mechanism  200  includes subtraction logic  202 , addition logic  226  and  246 , multiplication logic  220  and  232 , compare logic  204 ,  222 , and  228 , inverter logic  208 ,  210  and  214 , delay logic  206  and  212 , latch  216 , AND logic  224 , OR logic  230 , switching logic  234  and  250 , limiter logic  248  and ramp logic  252 . The LBO bias mechanism  200  receives various sensor parameters and control values, including engine speed data, commanded fuel flow data, and the current LBO value. In the illustrated embodiments, the LBO bias mechanism receives a margin input  260 , an N 1 _TKO input  262 , an N 1  input  264 , a threshold input  266 , a delay input  268 , a % N 1 _IDLE input  270 , an N 1 _IDLE input  272 , an N 1  input  274 , a WFR input  276 , a LBO input  278 , a margin input  280 , a manual input  282 , a bias step input  284 , a bias min input  288  and a bias max input  290 . 
     In general, during operation of the turbine engine the current LBO schedule value is received at LBO input  278 . A specified margin is received at margin input  280 . The addition logic  226  adds the LBO schedule value to the margin and passes its output to the compare logic  228 . The compare logic  228  receives the current commanded fuel flow from WFR input  276 . Thus, the compare logic  228  compares the current commanded fuel flow to the LBO schedule plus the specified margin (e.g., 0.3 fuel ratios). When the current commanded fuel flow is greater than the LBO schedule plus the specified margin, the output of compare logic  228  is asserted. If the output of compare logic  222  is also asserted (which will be discussed in greater detail below) the output of AND logic  224  is asserted and passed to the OR logic  230 . The OR logic  230  also receives the manual input  282 . The manual input  282  facilitates manual enablement of the LBO bias. Thus, if either the output AND logic  224  or the manual input is asserted, the output of OR logic  230  will be asserted. 
     The bias step input  284  provides the increment that is used to gradually increase and decrease the LBO bias. Thus, the bias step input  284  is passed to a first input on switching logic  234 . The bias step input  284  is also negated using multiplication logic  232  and the −1.0 input  286 , and the negated bias step input  284  is passed to the second input on switching logic  234 . When the output of OR logic  230  is asserted, the switching logic  234  selects the upper terminal and thus bias step input  284  is passed to the addition logic  246 . When the output of OR logic  230  is not asserted, the switching logic  234  is selects the lower terminal and thus the negated bias step input  284  is passed to the addition logic  246 . In one example implementation, the bias step input  284  is set to reduce the bias from BIAS MAX to BIAS MIN in about 15 seconds. 
     The addition logic  246  also receives the LBO bias value  298  through the delay logic  252 . The addition logic  246  thus adds the bias step or the negated bias step to the previous LBO bias value. Thus, the addition logic  246  effectively gradually increments or decrements the LBO bias value as controlled by the OR logic  230  output. 
     The output of the addition logic  246  is passed to the limiter logic  248 . The limiter logic  248  limits the range of LBO bias value to between the bias min value and the bias max value. Specifically, the limited output of the limiter logic  248  is passed through switching logic  250 , and thus provides the LBO bias value when the switching logic  250  is switched to the lower terminal In one example implementation, the bias min value is zero and the bias max value is 1 fuel ratio. 
     To summarize the operation of the LBO bias mechanism  200  described so far, when the commanded fuel flow is greater than the current LBO level by a specified margin, the addition logic  246  increments the LBO bias by the bias step input  284  value. When the commanded fuel flow is not greater than the LBO plus the specified margin, the addition logic  246  decrements the LBO bias by the bias step input  284  value. The ramp logic  252  causes the incrementing and decrementing of the LBO bias, the bias step is selected to make the change gradual, and the limiter logic  248  limits the LBO bias to be between a specified bias minimum value and a bias maximum value. The selective incrementing and decrementing of the LBO bias provides a selectively increased LBO schedule that improves lean blowout protection while maintaining fuel flow control ability to decelerate the engine. 
     The LBO bias mechanism  200  also provides full bias when the control is in standby when the DEEC output is disabled and the engine is controlled by other “manual” means. This is accomplished by incrementing the LBO bias upward. Specifically, by asserting the manual input  282 , the switching logic  234  can be controlled to increment the LBO bias. This provides for full bias to prevent lean blowout upon the transfer from standby to auto control. 
     The LBO bias mechanism  200  also facilitates selective disabling of the LBO bias in certain circumstances to provide improved engine control in these circumstances. For example, the LBO bias mechanism  200  can selectively disable the bias during engine startup to facilitate low fuel flow during startup to avoid hot starts. Furthermore, the LBO bias mechanism  200  can selectively disable the bias for takeoff situations to facilitate a fast response in the event of a rejected takeoff 
     Specifically, the LBO bias mechanism  200  disables bias during engine startup by comparing the current engine speed to a specified percentage of the idle speed. N 1  input  274  receives the current engine fan speed. The N 1 _IDLE input  272  specifies the N 1  value that indicates full idle speed, and the % N 1 _IDLE input  270  is a percentage of the full idle speed used (e.g., 90%). The multiplication logic  220  multiplies the N 1 _IDLE input  272  by the percentage specified by % N 1 _IDLE  270 . The compare logic  222  compares the N 1  engine speed to the resulting product. If the N 1  engine speed is less than the product, then the compare logic  222  output is not asserted. When the compare logic is not asserted, the LBO bias decrements as described above. Thus, if the N 1  engine speed is less than a specified percentage of the N 1 _IDLE speed, then the LBO bias is decremented. It should be noted that in this particular embodiment the bias is decremented at slower speed and incremented at higher speed during startup rather than completely shut off. This helps avoid sudden changes in LBO bias that could otherwise occur during startup as speed approaches idle. 
     Additionally, the LBO bias mechanism  200  can selectively disable the bias for takeoff situations to facilitate a fast response in the event of a rejected takeoff. Specifically, the LBO bias mechanism  200  disables LBO bias during takeoff by comparing the current engine speed to the takeoff speed minus a specified margin. N 1  input  264  receives the current engine fan speed. The N 1 _TKO input  262  specifies the N 1  value that indicates takeoff speed, and the margin input  260  is a percentage of the full takeoff speed used as a margin (e.g., 7%). The subtraction logic  202  subtracts the margin from the N 1 _TKO  262 . The compare logic  204  compares the N 1  engine speed to the resulting value. If the N 1  engine speed is greater than the N 1 _TKO value minus the margin percentage, then the compare logic  204  output is asserted. 
     The output of the compare logic  204  is passed to input of the delay logic  206 , is inverted by inverter logic  208  and passed to the reset input of delay logic  206 . Additionally, the output of the compare logic  204  is inverted by inverter logic  210 , and the inverted output is passed to input of the delay logic  212 , is inverted again by inverter logic  214  and passed to the reset input of delay logic  212 . 
     The delay logic  206  and  212  are configured to reset immediately, but will delay passing an input to the output by a time specified by the delay input. Thus, when the N 1  engine speed is greater than the N 1 _TKO value minus the margin percentage, then the compare logic  204  output is asserted, asserting the input to the delay logic  206 . After a delay equal to the delay specified by the DELAY 1  input  266 , the set input on latch  216  is asserted. This causes the output Q of latch  206  to become asserted, which switches switching mechanism  250 , causing the LBO bias to be immediately reset to zero. 
     The compare logic  204  asserted output is also passed to the delay logic  212  input through inverter logic  210 . The inverted output is passed from the output of delay logic  212  after a delay equal to the delay specified by the DELAY 2  input  268 . When the N 1  engine speed drops below the N 1 _TKO value minus the margin percentage, the compare logic  204  output is de-asserted, asserting the input to the delay logic  212 . The inverted output is passed from the output of delay logic  212  after a delay equal to the delay specified by the DELAY 2  input  268 . This causes the output Q of latch  206  to become de-asserted, which switches switching mechanism  250 , allowing the LBO bias to again be incremented and/or decremented by the output of switching logic  234 . 
     Thus, delay logic  206  and  212  and latch  216  function to disable the LBO bias after a delay equal to DELAY 1  when the N 1  engine speed is above the N 1 _TKO value minus the margin percentage, and likewise function to enable LBO bias after a delay equal to DELAY 2  when the N 1  engine speed is below the N 1 _TKO value minus the margin percentage. Typically, DELAY 2  would be selected to be much larger than DELAY 1 . For example, DELAY 2  could be set to 9 seconds, while DELAY 1  is set to 1 second. This causes LBO bias to be disabled relatively quickly, when needed, but causes LBO bias being enabled to be further delayed. This ensures that a relatively short time at high power will set the directly bias to zero. This corresponds to a warm engine which is unlikely to be at risk of lean blowout. Conversely, when the bias is set to zero it causes the bias to remain at zero for a relatively long period of time. This ensures that the LBO bias will be zero long enough for the engine to decelerate rapidly to idle power if power is suddenly reduced from takeoff power. 
     Thus, a lean blowout protection system using the LBO bias mechanism  200  provides improved turbine engine lean blowout protection while retaining effective control of turbine engine speed and temperature. 
     Turning now to  FIG. 3 , a schematic view of an LBO schedule mechanism  300  in accordance with one embodiment of the invention is illustrated. The LBO schedule mechanism  300  is one example of the type of mechanism that can be used in the lean blowout protection system  100 . In general, the LBO schedule mechanism  300  receives the temperature data and the engine speed data and generates a preliminary LBO value. 
     The LBO schedule mechanism  300  includes division logic  302 , subtraction logic  304  and  312 , addition logic  314 ,  316  and  320 , multiplication logic  308  and  310 , and limiter logic  306  and  318 . The LBO schedule mechanism  300  receives various sensors parameters and control value values, including engine speed data and temperature data. In the illustrated embodiments, the LBO schedule mechanism receives a margin LBO_ADJ input  330 , C 2  input  332 , a NUM input  334 , a TEMP input  336 , a C 1  input  338 , a speed input  340 , a C 4  input  342 , a C 3  input  344 , a MIN 1  input  346  and a MIN 2  input  348 . Additionally, the LBO schedule mechanism  300  receives the LBO bias input  298  from the LBO bias mechanism. 
     In operation, the division logic  302  divides the NUM input  334  by the TEMP input  336 . Typically, the NUM input  334  is set to 1.0, and the output of the division logic  302  is thus the inverse of the TEMP input  336 . A variety of temperature data sources could be used as the TEMP input, including the total inlet temperature (TT 2 ). A constant is received from the C 1  input  338 , and the subtraction logic  304  subtracts the constant C 1  from the output of the division logic  302 . The result is passed to limiter logic  306 , which prevents the output from falling below the MIN 1  output value (e.g., 0). The multiplication logic  308  multiples the output of the limiter logic  306  is by a constant received from the C 2  input  332 . 
     Multiplication logic  310  multiplies the speed input  340  by a constant received from the C 4  input  342 , and the resulting product is subtracted from the constant received from the C 3  input  344  by subtraction logic  312 . The addition logic  314  adds the output of the subtraction logic  312  to the output of the multiplication logic  308 . The addition logic  316  adds the output of the addition logic  314  to the LBO_ADJ input  330 . The result is passed to limiter logic  318 , which prevents the output from falling below the MIN 2  output value (e.g., 3.0 fuel ratio). The output of the limiter logic  318  is the preliminary LBO value, which is then added to the LBO bias input  298  using addition logic  320 . 
     In general, the engine speed and temperature are combined with the constants C 1 , C 2 , C 3  and C 4  to determine the preliminary LBO value. The LBO_ADJ input  330  provides the ability for the initial value to be manually adjusted. The values for C 1 , C 2 , C 3  and C 4  would depend on the particular turbine engine and its application, and would be selected to convert the speed and temperature values into appropriate fuel ratios for the engine. 
     The lean blowout protection system  100  can be implemented in a wide variety of different types of turbine engines. Thus, although the present embodiment is, for convenience of explanation, depicted and described as being implemented in combination with a multi-spool turbofan gas turbine jet engine, it will be appreciated that it can be implemented in various other types of turbines, and in various other systems and environments. 
     Turning now to  FIG. 4 , an embodiment of an exemplary multi-spool gas turbine main propulsion engine  400  is shown, and includes an intake section  402 , a compressor section  404 , a combustion section  406 , a turbine section  408 , and an exhaust section  410 . The intake section  402  includes a fan  414 , which is mounted in a fan case  416 . The fan  414  draws air into the intake section  402  and accelerates it. A fraction of the accelerated air exhausted from the fan  114  is directed through a bypass section  418  disposed between the fan case  416  and an engine cowl  422 , and generates propulsion thrust. The remaining fraction of air exhausted from the fan  414  is directed into the compressor section  404 . 
     The compressor section  404  may include one or more compressors  424 , which raise the pressure of the air directed into it from the fan  414 , and directs the compressed air into the combustion section  406 . In the depicted embodiment, only a single compressor  424  is shown, though it will be appreciated that one or more additional compressors could be used. In the combustion section  406 , which includes a combustor assembly  426 , the compressed air is mixed with fuel supplied from a fuel source (not shown). The fuel/air mixture is combusted, generating high energy combusted gas that is then directed into the turbine section  408 . 
     The turbine section  408  includes one or more turbines. In the depicted embodiment, the turbine section  408  includes two turbines, a high pressure turbine  428 , and a low pressure turbine  432 . However, it will be appreciated that the propulsion engine  400  could be configured with more or less than this number of turbines. No matter the particular number, the combusted gas from the combustion section  406  expands through each turbine  428 ,  432 , causing it to rotate. The gas is then exhausted through a propulsion nozzle  434  disposed in the exhaust section  410 , generating additional propulsion thrust. As the turbines  428 ,  432  rotate, each drives equipment in the main propulsion engine  400  via concentrically disposed shafts or spools. Specifically, the high pressure turbine  428  drives the compressor  424  via a high pressure spool  436 , and the low pressure turbine  432  drives the fan  414  via a low pressure spool  438 . 
     As  FIG. 4  additionally shows, the main propulsion engine  400  is controlled, at least partially, by an engine controller  450  such as, for example, a DEEC (Digital Electronic Engine Controller). The engine controller  450  controls the operation of the main propulsion engine  400 . More specifically, the engine controller  450  receives selected signals from various sensors and from various pilot-manipulated controls and, in response to these signals, controls the overall operation of the propulsion engine  400 . A variety of different sensors can be used by the engine controller, including various speed sensors, including fan speed (N 1 ) and main shaft speed (N 2 ) sensors, temperature sensors, fuel flow and pressure sensors. Additionally, a power lever angle (PLA) signal can also be included and used by the engine controller  450 . 
     In one embodiment of the invention, the lean blowout protection system is implemented at least partially in the engine controller  450 . For example, the lean blowout protection system can be implemented at least partially as software that is executed by the engine controller  450 . The lean blowout protection system would receive the various sensor data and generate an LBO schedule which is then used by the engine controller  450  to define the minimum fuel flow delivered to the turbine engine. Specifically, during operation of the turbine engine the engine controller  450  ensures that that the commanded fuel flow to the turbine engine does not go below the LBO schedule determined by the lean blowout protection system, thus providing lean blowout protection for the turbine engine. As described above, the lean blowout protection system adds a gradually increasing positive bias to the LBO schedule when the commanded fuel flow is greater than the LBO schedule by a specified margin. Then, when the commanded fuel flow falls below the margin the system decreases the positive bias until the commanded fuel flow reaches the LBO schedule. The increasing and decreasing of the LBO bias provides a selectively increased LBO schedule that improves lean blowout protection while maintaining fuel flow control ability to quickly decelerate the engine. 
     The lean blow out protection system can be implemented in a wide variety of computational platforms. Turning now to  FIG. 5 , an exemplary computer system  50  is illustrated. Computer system  50  illustrates the general features of a computer system that can be used to implement the invention. Of course, these features are merely exemplary, and it should be understood that the invention can be implemented using different types of hardware that can include more or different features. The exemplary computer system  50  includes a processor  110 , an interface  130 , a storage device  190 , a bus  170  and a memory  180 . In accordance with the preferred embodiments of the invention, the memory  180  includes a lean blowout protection program. 
     The processor  110  performs the computation and control functions of the system  50 . The processor  110  may comprise any type of processor, including single integrated circuits such as a microprocessor, or may comprise any suitable number of integrated circuit devices and/or circuit boards working in cooperation to accomplish the functions of a processing unit. In addition, processor  110  may comprise multiple processors implemented on separate systems. In addition, the processor  110  may be part of an overall vehicle control, navigation, avionics, communication or diagnostic system. During operation, the processor  110  executes the programs contained within memory  180  and as such, controls the general operation of the computer system  50 . 
     Memory  180  can be any type of suitable memory. This would include the various types of dynamic random access memory (DRAM) such as SDRAM, the various types of static RAM (SRAM), and the various types of non-volatile memory (PROM, EPROM, and flash). It should be understood that memory  180  may be a single type of memory component, or it may be composed of many different types of memory components. In addition, the memory  180  and the processor  110  may be distributed across several different systems that collectively comprise system  50 . 
     The bus  170  serves to transmit programs, data, status and other information or signals between the various components of system  50 . The bus  170  can be any suitable physical or logical means of connecting computer systems and components. This includes, but is not limited to, direct hard-wired connections, fiber optics, infrared and wireless bus technologies. 
     The interface  130  allows communication to the system  50 , and can be implemented using any suitable method and apparatus. It can include a network interfaces to communicate to other systems, terminal interfaces to communicate with technicians, and storage interfaces to connect to storage apparatuses such as storage device  190 . Storage device  190  can be any suitable type of storage apparatus, including direct access storage devices such as hard disk drives, flash systems, floppy disk drives and optical disk drives. As shown in  FIG. 5 , storage device  190  can comprise a disc drive device that uses discs  195  to store data. 
     It should be understood that while the present invention is described here in the context of a fully functioning computer system, those skilled in the art will recognize that the mechanisms of the present invention are capable of being distributed as a program product in a variety of forms, and that the present invention applies equally regardless of the particular type of computer-readable signal bearing media used to carry out the distribution. Examples of computer-readable signal bearing media include: recordable media such as floppy disks, hard drives, memory cards and optical disks (e.g., disk  195 ). 
     Thus, the embodiments of present invention provide a turbine engine lean blowout protection system and method that facilitates improved lean blowout protection while providing effective control of turbine engine speed. The lean blowout protection system and method selectively and gradually biases the lean blowout (LBO) schedule based on current engine data. This facilitates improved lean blowout protection while providing effective control of turbine engine speed and temperature. 
     The embodiments and examples set forth herein were presented in order to best explain the present invention and its particular application and to thereby enable those skilled in the art to make and use the invention. However, those skilled in the art will recognize that the foregoing description and examples have been presented for the purposes of illustration and example only. The description as set forth is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching without departing from the spirit of the forthcoming claims.