~ 51GA--2463 This invention relates to gas turbine engines and more particularly to an apparatus for monitoring the op~ration oE
a gas turbine combustion system, Combustion systems for gas turbines usually e~ploy one or more combustion liners of either annular or can type wherein fuel is burned to generate a generally annular hot gas steam fox driving the turbine.
Because of the extremely hostile pressure and temperature environment of a gas turbine combustion system, relatively minor combustion system problems can propogate into serious gas turbine damage if left unattended~
A primary o~ject of this invention~ there~ore~ is to provide an apparatus for monitoring the combustion system of a gas turbine and for shutting down the turbine or sounding an alarm when an abnormalty is detected.
Another object of this invention is to provide an apparatus for detecting gas turbine combustion system problems at an early stage, The above and other-objects and advantayes are achieved in the present invention by providing means for sensing the temperature of the hot gas steam generated by a gas turbine combustion system and means for determining whether the com-bustion system is functioning improperly as a function of such sensed temperatures, The sensing means comprise a plurality o~ sensors, such as thermocouples, disposed in a spaced annular `~ array along the hot gas stream flow path, such as in the ex-haust duct, Means are provided for determining what the spread is between var1ous sensed temperatures and for generating a ~-signal when the spread exceeds a predetermined or selected amount, In one form, means are provided to determined the spread ~; between the highest sensed temperature and the average of the sensed temperatures and between such average and the lowest ~ ~ .
~ 738 51GA-2463 sensed temperature and for then shutting dow~l the gas turbine if either spread is greater than a predetermined or calculated amount. In another Eorm~ the spread is determined between the maximum and minimum sensed temperatures and a shut-down s.ignal is generated when this spread exceeds a predetermined amount.
m e invention may also smploy means for determining the kime rate of increase of the temperature spread and for generating a shut-do~n or alarm signal when t:his rate exceeds a pre-determined amount The invention preferably employs a digital computer, in-put circuit means for input to the computer of the sensed tempexature signals, and temperature sensor select circuit means, with the computer being programmed to cause the circuit select means to sequentially sample each temperature sensor and computer the desired spread or spreads and genexate a signal when the spread or one of the spreads exceeds the predetermined or selected amount While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of this invention, it is believed that the invention will be better understood upon reading the following description oE the pre-ferred embodiment in conjunction with the accompanying drawings, wherein:
FIGURE l is a diagrammatic representation of a gas turbine system employing the combustor monitor of this invention;
FIGURE 2 is a schematic, in block diagram form7 showing one form of the combustor monitor of this invention;
FIGURE 3 is a block diagram schematically showing one form of the digital c-omputer of ~IG. 2;
FIGURE 4 is a flow graph of a program which may be used in the present invention for the digital computer of FIG 3;
FIGURE 5 is a continuation of the flow graph of FIG 4;
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.;2738 51GA ~2 4 6 3 FIGURE 6 is a flow graph, like that of. Fig 4, showing the preferred method of and proyram for use in the present in-v~ntion; and FIGURE 7 is a continuation oE the flow graph of Fig. 6.
Referring now to the drawings and particularly to Fig. 1 an exemplary heavy duty gas turbine has been shown generally at 10 as including a compressor 12~ a combustor 14, and a turbine 16. Air is delivered to the compressor 12 through a suitable inlet 18 and is compressed and delivered to a com-bustor 14 through suitable ducting~ shown diagrammatically at20. Fuel is delivered to the combustor 14 through a plurality of suitable fuel nozzles 22 and is burned in the combustor to generate a motive or hot gas stream for driving the turbine 16.
The hot gas stream generated by the combustor 14 is de-livered to the tuxbine 16 through suitable ducting, as di--agrammatically shown at 24 The turbine 16 is drivingly con-nected to the compressor 12 and a load 26, such as a generator, by shaft connections 28 and 30~
A suitable gas turbine control means for controlling the fuel flow to the gas turbine 10 has been shown generally at 32 as being responsive to a speed signal on line 34 which is generated by a suitable speed sensor 363 a flame detector signal on line 38 which is generated by a suitable flame de-tector 40, and an exhuast gas temperature signal or signals on lines 42, 44~ 46, and 48, which are generated by suitable temperature sensors 50 disposed in an annular array in the exhaust duct 52 of the gas turbine As diagrammatically in-dicated by line 54, the gas turbine contxol 32 regulates ~uel flow to the nozz;les 22 by way of a suitable variable delivery fuel pump or gas valve 56.
For a more detailed description o the gas turbine control 32, reference is made to U S Patent 3~520,133, issued July 14, 51GA-24~3 7~3 1970, and assigned to the assignee o~ the present inven-tion, It should be understood~ however, that other gas turbine controls could be used with the present invention and that the present invention is not limited to use with th~ exemplary gas turbine control re:Eerenced above, Likewise~ while the yas turbine 10 has been shown and desc:ribed as being of the single rotor type~ the combustor monitor apparatus of this invention may be benefically employed on gas turbine which employ more than one rotor, With continued reference to Fig, 1, the combustion monitor has been shown generally at 58 as receiving a temperature signal on lines 60, 42, 44) 46 and 48. The signal on line 60 is generated by a suitable sensor 62 which monitors the tem-perature of the compressed air leaving compressor 12, The ssignals on lines 42, 44, 46 and 48 are indicative of khe exhaust gas temperature, As will be hereinafter explained more fully7 the combustion monitor means of this invention operates on these input signals to determine whether the com-bustion system (lincluding Euel nozzles 22, combustor 14 and ducting 24~ is operating properly, In the event of a detected malfunction, the combustion monitor sends an appropriate shut-down signal on line 64 or alarm signal on line 66 or- 68 to the engine control 3~.
While only four exhaust gas temperature sensors 50 have been depicted in Fig, 1, it should be understood that such a showing is simplified and that in actual practice as many as twelve or more genérally equally spaced temperature sensors would be used in an annular axray, The spacing between adjacent sensors is preferably equal and selected such that a hot or cold streak in the hot gas stream which is produced by a mal-function in the combustion system would affect more than one -temperature sensor, :
51GA-2~63 7~
T~hile the sensors 50 have been shown as being located at different axial positions relative to the hot gas stream flow, it should be understood that in practice all the sensors 50 would be positioned at approximately the same axial location or, stated another way, generally equidistant from the turbine 16.
The means of this invention ior monitoring the operation of the combustion system generally comprise means for sensing the temperature of the hot gas stream, such as temperature sensors 50 disposed in exhaust duct 52, such as the combustor monitor 58, for determining whether the gas turbine combustion system is operating abnormally as a function of the sensed temperatures and for generating a signal operative to cause gas turbine control means 32 to shut off fuel ~low to the combustor 14 when abnormal operation is detected In pre-ferred form, the combustor monitor 58 computes one or more temperature spreads and compares these spreads to a pre-determined or selected amount.
With reference now to Fig 2~ the combustion monitor 58 has been shown, in one rorm, as comprising a digital computer 70, a temperatuxe sensor input circuit 72, a temperature sensor select circuit 7~, and a display circuit 76. The alarm and shutdown signal lines 64, 66l and 68 pre~erably include a suitable photo isolator 78 to protect the gas turbine control from any spurious siynals from the digital comput~or 70~
While two exhaust gas temperature sensors 50 have been schematically shown at 80? it should be understood that up to twelve or more sensors would be used in actual practice. Each sensors would be used in actual practice. Each sensor S0 is connected to the gas turbine control 32 and the temperature sensor input circuit 72 through suitable switching means~
such as normally closed contacts 82 and normally open contacts ; - 5 -.:
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84 of a relay 86, and through lines 88, 90~ 92~ and 94.
The compressor discharge temperature sensor 62 is also connected to the input circuit 72 through lines 927 94 and through switch means, such as normally open contacts 96 of a relay 98, The temperature sensor select circuit 74 includes address decoder means 100 for receiving a 4-bit binary signal on line 102 from digital computer 70 and for selectively energizing one of re~ays 86, 98 in response to such signal through a suitable driver or amplifier lQ4, me decoder means 100 may be a 1 of 16 decoderO
The temperature sensor input cixcuit 72 has been shown as including a signal amplifier 106 for receiving and ampli~ying the t~mperature signal on lines 92, 94, limiter means 108 and an analog to digital converter means 110, The limitex means 108 is adapted to receive the signal output ~rom amplifier 106 on line 112 and limit the input signal to the converter means 110 on line 114~ and may comprise a diode limiter and an amplifier with a gain of 1, The converter means 110 is adapted to convert the temperature signal received on line 114 into a : suitable 8-~it binary signal for processingly by computer 70 in response to a "start computation" signal received from computer 70 on line 116. The converter means 110 is also adapted to provide a signal to the computer 7~ thxough line 118 to indicate when a particular analog to digital conversion has been made. The digital temperature signal generated by con-verted means 110 is delivered to the computer 70 through a suitable 8-bit binary line 120~
The display circuit 76 includes a binary to binary coded decimal converte~d means 122 for receiving an 8-bit binary tem-perature spread signal ~rom digital computer 70 on line 124 and for ~onverting this signal to a 10-bit binary coded decimal .
51 ~YA - 2 ~ 6 3 signal, This binary coded decimal si~nal is then delivered to a suitable cligital display 126 throuyh lines 128, A photo isolator 78 may be provided between the combustion monitor and the gas turbine control 32 for lines 64, 66 and 68 and for line 69, Line 69 functio.ns to deliver an enable signal from gas turbine control 32 whi~h is effective to turn on the computer 70, A suitable reset switch is p:rovicled at 130 to selectively ground line 132 and thereby reset the computer 70 on reset or index the program ~or computer 70 -to its "0" position, With reference now to FIG, 3~ the digital computer 70 has been shown in block diagram form as including input means 1~0 a central processing unit 142 (hereinafter referred to as "CPU"), a clock 144 for the CPU3 a memory decoder 1~6, a state decoder 1487 a memory 150~ an input/output decoder 152 and output means 154.
The input means 140 is adapted to selectively receive an input signal from one of lines 69, llB3 120 in response to a command signal received on one of lines 160 and deliver this signal to the CPU 142 for further processing on line 162, As will be understood, the clock means 144 functions to time the sequential operations of the CPU 14~ so as to ensure : that a new operation is not started until the prior operation has been completed, When înformation is to be stored or read our of memory 150, a memory address signal is generated by the CPU 142 and delivered to th~e memory decoder 146 on line 164, Based on the memory address signal, the memory decoder 146 provides a memory select signal to memory 150 on line 166, ;30 The state ,decode.r means 148, in response to a signal on line 168 from CPU 142, functions to selectively energize the - input and output means 140 and 154 by way of lines 170 and 172, , 73~ 5 :L~,A ~ 2 ~ ~ 3 respecti~ely~ ancl tells the memory 150 whether it should function in a memory read or memory write mode. ~nlen the memory read mode is energized by line L74, the inEormation stored at the locatlon selected by memory decoder 146 is delivered to the CPU 142 on line 176 Likewise, when the memory ~rite mode is energized by line 178i information is delivered on line 180 by the CPU 142 and stored at the memory address selected by memory decoder 146 The input/output decoder means 152, in response to a signal on line 182 from the CPU 1429 delivers a select signal on one of line 160 to the input means 140 and the output multiplex means 154 which tells these means which of lines 64, 66, 68, 69, 102, 118, 120 or 124 should be sampled. For example, when line 102 of the temperature sensor select circuit 74 of Figure 2 is selected, the coded binary signal indicative of which temperature sensor 50 is to be sampled is delivered on line 184 from the CPU and, hence, through out-put means 154 and line 102 In operation, the twelve temperature sensors 50 and the compressor discharge temperature sensor 62 are sequentially sampled on a continuous bàsis. Their respective temperature readings are ampli~ied7 converted to an 8-bit offset binary digital signal and delivered to the CPU 142 ~y the temperature sensor input circuit 727 As will be hereinafter described in greater detail, the computer 70 ~irst determines, at least on a preliminary basis, whether each sensor 509 62 is operating properly I~ it is not, the temperature signal from the de~ective sensor is dis-regarded and an alarm signal may be issued on line 64~
I~ the digital computer 70 determines that an exhaust gas sensor is opexating properly, the temperature signal from that sensor is compared with the maximum and minimum exhaust gas 3~ 51GA~2463 temperature readings thus far ohserved, If the new temperature reading is greater than the previously observed maximum or less than the previously observed minimum, the new temperature read-ing is substituted therefore, The digital computer 70 con-tinuously computes the temperature spread between selected ex~
haust gas temperature readings and may also compute the rate of change o~ this temperature spread, If the temperature spread exceeds a predetermined amount or if the rate of change of the temperature spread exceeds a predetermined rate, alarm and shutdown signals are delivered to the gas turbine control 32 on lines 66, 68, While each connection between the components of Figures
2 and 3 have been depicted and described as a single lineg it will be understood that those lines that transfer digital in-formation are preferably comprised of multiple conductors.
Flow graphs for the digital computer 70 are shown in Figures 4, 5 and 7 for a combustion monitor system employing twelve exhaust gas temperature sensors, In these figures, ~; "Tcd" represents the temperature reading of the compressor discharge temperature sensor 62; "Ti" represents the tem-perature reading of one of ~he exhaust gas temperature sensors 50; "Hil" represents a first predetermined or calculated amount and "Hi2" represents a second predetermined or calculated amount, "S" represents the spread between the maximum and minimum observed exhaust gas temperature sensors; " ~ s"
represents the rate of change of temperature spread between ~ :
the maximum and minimum exhaust gas temperature sensox read-ings, "MAX" represents the maximum observed exhuast gas tem- :
perature; "MIN" represents the minimum observed exhaust gas temperature; and TAVG represents the average of the observed exhaust gas temperature readings, With reference to Figs, 4 and 5, after enabling and xe-~ 9 ~
; ~ - . ' , ~ J~ 3~ SlGA~2~63 setting the counter at 1, the compressor discharge tem pe.rature is sampled at 200~ Next, the first exhaust gas temperature sensox 50 is sampled at 202 At 204, the com-pressor discharge temperature .is compared to a predetQrmined value, such as 400 ~. If the sensed discharge compressor temperature is not greater than 400 F, then the exhaust gas tempeLatUre reading is compared t:o 400 F at 206. If the reading from a particular exhaust: gas sensor S0 is less than 400 F the reading is considered invalid and is not used in computing temperature spread Where the compressor discharge temperature is greater than 400 F~ then the sensed exhaust temperature is compared at 208 to the compressor discharge temperature Again, if the sensed exhaust temperature is not greater than the compressor discharge temperature, the sensed exhaust temperature is considered invalid and is not used in computing temperature spreadO
At 210, each valid exhaust gas temperature reading is compared with the prior maximum exhaust gas temperature reading and the prior minimum exhaust gas temperature reading If a temperature reading is higher than the previous high reading, it displaces the old maximum reading at 212~ Likewise~ if the temperature reading is lower than the old low reading, it displaces the old low reading~ it displaces the old minimum reading at 212. When each of the temperature sensors 50 have been sequentially sampled3 the spread or difference between the maximum and minimum sensed temperatures is computed at 214 In the embodiment of Fig S~ the temperature spread "S" is ~ first compared at 216 with a first predetermined amount "Hil"~
- If "S" is greater than "Hil", then a shutdown and alarm signal is generated at 218. If "S" is less than "Hil", then it is compared with a second predetermined amount "Hi2" at 220 If "S'~ is less than "Hi2"5 the cycle is repeated~ However~ if "S"
-. . : :
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~ 3~ 51GA-2463 is greater than "Hi2 ~ an alarm may b~ sounded as at 222 and the absolute ~alue of S storqd at 224 over an appropriate period of time and the chanye in the temperature spread over that period computed as at 226. If the change in temperature spread exceeds a predetermi~ed amount, for example 10 F/hour, a shutdown and alarm signal may be generated as at 218. Where the change in tempexature spread does not exceed such pre-determined amount, the cycle i5 repeated and each of the sensors 50 is again sampled.
In the flow graph of Figures 6 and 7 9 the comprassor discharge temperature is sampled at 230 and compared to an upper and lower limit at 232. If this temperature is out-side the limits, it is rejected as a bad thermocoupled at 234 and a preselected value3 such as 400 F, is used in place of the compressor discharge temperature. If the compressor discharge temperature reading is within the limit o~ 232, then the ~irst exhaust gas temperature sensor 50 is sampled at 236. The exhaust gas kemperature sensor reading is preliminarily scxeended Eor validity at 238 by comparing it with an upper and lower limit. If it is within the limits it is compared with the previous maximum and minimum readings at 240 and if it is greater than the previous maximum or less than the old minimum it displaces such previous reading at 242. If the exhuast gas temperature sensor reading is not within the limits of 238 then an alarm is sounded at 244 and the reading is rejected from ~urther use as being invalid and the next sensor is sampled at 236.
When each of the sensors 50 have been sequentially sampled9 the average temperature sensor reading is computed at 246, the high spead or dif~erence between the maximum observed tem-perature sensor reading and the average temperature sensor reading is computed at 248, and the low spread or difference ~ 7~ 63 between the average temperature readiny and the minimum tem-perature reading is computecl at 250 In computing the average temperature sensor reading at 246, it may be desirable to discard one or more temperature sensor readings. For example, it may be desirable to exclude the MAX and/or MIN readings when such average is computed At 252~ the high spread is compared to a first predeter-mined or calculated limit and i~ it exceeds this limit an alarm is sounded and the gas turbine is shutdown at 254 If the high spead is lower than this limit, then the low spead is compared to a second limit at 256 and if it is less than this limit and after an appropriate delayl the entire cycle is repeated. Where the low spread exceeds the limit at 256, it may be desirable to determine with greater precision whether this is due to a faulty thermocoupled or whether it is due to a low temperature streak in the hot gas stream which would be indicative o~ a combustion system malfunction.
mus, at 258, the thermocouples adjacent the thermocouple on which the minimum temperature was observed are examined to determined whether they ar0 within predetermined bounds. If the adjacent readings are high or low then an alarm would be activated and the gas turbine shutdown at 254 If the adjacent thermocouples are within predetermined bounds then the minimum thermocoupled reading is rejected at 262 as being invalid and the complete cycle o sampling thermocouples is repeated In preferred form and with the sensors S0 disposed in an annular array, the two adjacent sensors 50 on each side of the suspect sensor are examined It will be understoodg however, that the exact number of adjacent sensors to be examined will vary ~ 30 depending upon the total number of sensors used and the ; nature o the expected temperature profile with the postulated combustion system malfunction~
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~ 7~ 51G~ 2~6~
Combustion system problems can generally be expected to manifest themse:Lves by either hot or cold streaks in the annular hot gas stream. Foe example, a plugged fuel nozzle would produce a cold streak whi.le a clogged or collapsed cooling or dilution hole or louver would produce a hot streak, Accordingly, by providing an apparatus that senses the tem-perature of the annular hot gas stream at a number of spaced points and determines whether the spread between the high and low reading exceed a precletermined amount, problems in the combustion system may be detected at an earlier stage so as to permit appropriate corrective action, The temperature sensors or thermocouples 50 are preferably provided in su~ficient quantity so that the spacing between thermocouples is such that a cold or hot streak produced by a mal~unctioning combustion system would affect more than one thermocouple, In this manner, by examining adjacent thermo-couples, it is possible to detect whether an unusually low or high temperature reading is due to a bad thermocouple or ; due to a temperature streak, Although the present invention has been shown as employing a digital computer 70, it will be understood by those skilled in the ar that the digital computer could be replaced by suitable analag circuitry, While a preferred embodiment of the invention has been depicted and described~ such embodiment is intended to be : exemplary only and not definitive and it will be appre¢iated by those skille~d in the art tha-t many substitutions, al-ternations and changes may be made thereto without departing ~rom the fundamental theme of the invention, _ 13 -5~GA-2463 SUPPLEMENTARY DISCLOSURE
In addition to the foregoing disclosed em~odiment wherein the computer is programmed to cause the circui-t select means to sequentially sample each temperature sensor and compute the desired spread or spreads and generate a signal when the spread or one of the spreads exceeds the predetermined or selected amount, the compute:r may alternatively be programmed to cause the circuit select means to sequentially sample each hot gas stream temperature sensor and determine the median hot gas stream temperature, compute the allowable temperature limits and generate a signal when a predetermined number of hot gas stream temperature sensor readinys exceed the temperature limits in a predetermined pattern. The functions of circuits and components other than the computer are as previously disclosed.
This other embodiment of the invention is illustrated in supplementar~ Figures 8 and 9, wherein:
Figure 8 is a flow graph of a program according to the second em~odiment for use with the digital computer of Fig. 3, and Figure 9 is a continuation of the flow graph of Fig. 8.
Referring the function of the second embodiment to the operation of the apparatus illustrated in Fig. 2, ; the combustor monitor 58 determines whether the gas turbine combustion system is operating abnormally as a function of ~, the sensed temperatures, and generates a signal operative to -cause the gas turbine control means 32 to shut off fuel flow to the combustor 14 when abnormal operation is detected.
While each connection between the components of 3Q Figures 2 and 3 has been depicted and described as a single line, it will be understood that those lines transfer digital ' `3 ` '':
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, ~ ,, . , . ' ' ' :' ~
- , ' 51GA~2463 information are preferably comprised of multiple conductors.
As will be hereinafter described in greater detail, the computer 70 first determines the median temperature sensor readiny "Tm" based on one complete scan of each of the temperature sensors 50. sased on "Tm" the computer then calculates a predetermined number of temperature limits as a function of the compressor discharge temperature ''TCd'' and "T " and determines whether these limits are exceeded by a ; m predetermined number of sensors 50 in a predetermined pattern.
Flow graphs for the digital cornputer 70 are shown in Figures 8 and 9 for a combustion monitor system employing twelve exhaust gas temperature sensors 50. In these figures, "TCd" represents the temperature reading of the compressor discharge temperature sensor 62; "Ti" represents the temperature reading of one of the exhaust gas temperature sensors 50;
"Tm" represents the median temperature as a result of a single scan of each of the temperature sensors 50; "~1" represents the high alarm limit; "AL" represents the low alarm limit;
"T~ " represents the high trip limit; and "TRL" represents the low trip limit.
With continued reference to Figs. 8 and 9, after enabling and resetting the counter at 1, the compressor discharge temperature is sampled at 200 and compared at 202 to an upper and lower limit, such as 200 and 1200. If ''TCd'' is outside of these limits, it is rejected as a bad thermocouple at 204 and a preseIected value, such as 400F, is - used in place of the sampled ''TCd''~ N~xt, each exhaust gas temperature sensor is sampled at 206~
At 208, each exhaust gas temperature reading is compared wlth the prior maximum exhaust gas temperature reading and the prior minimum exhaust gas temperature reading. If a temperature reading is higher than the previous high reading, .
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51~A-2463 it displaces the old ma~imum reading at 210. Likewise, it the temperature readiny is lower than the old low reading, it displaces the old minimum reading at 210. When each of the temperature sensors 50 have been sequentially sampled, the median temperature from a single such scan is determined at 212. As will be understood, when an odd number of sensors 50 are employed, the median temperature will be the temperature sensor reading of the middle reading sensor. On the other hand, where an even number of temperature sensors 50 are employed, the median temperature will be the average of the readings taken from the two middle reading sensors. At 214, high and low alarm and trip limits (AH and AL, and TRH and TRL) are computed as predetermined functions of the median temperature and the compressor discharge temperature. While particular functions of "Tm" and ''TCd'' are shown at 214, it will be recognized that the precise function used may vary from one gas turbine design to another.
With continued reference to the flow chart of Figure 9, each temperature sensor reading from a single complete scan is compared at 216 to "AH" and "AL" to determine if any reading is above l'AH" or below "AL" and, if there are any such out of bounds readings, to determine whether they exist in a predetermined pattern. In the embodiment of Figure 9, two patterns are addressed. If any three circumferen-tially adjacent temperature sensors are above "AH" or below "AL" in any combination and if this condition exists for three consecutive sc-ans of the sensors 50, then an alarm signal will be given at 2]7 to indicate a potential combustion system problem. Likewise, if any two circumferentially adjacent 30 sensors 50 are below the "AL" limit and any one sensor 50 is above "AH", and if this condition exists for three consecutive scans of the sensors 50, then the alarm signal will be given at :, ~ i, .
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51GA-2~63 217 to indicate a potential combustion system problem. It has been determined that the foregoing patterns fairly anticipate the temperature patterns that would be expected with most failure modes of a gas turbine combustion system, although it should be understood that these patterns may be varied, for example, with the number of temperature sensors employed and type of combustor.
While the arrangement of Figure 9 requires a deviation on three consecutive scans so as to prevent transient operating conditions from sounding an alarm, it should be recognized that this number may be varied.
In the event that any of the patterns of high or low sensor readings of 216 are found, the temperature sensor readings are further analyzed at 218 to determine whether the sensor readings are above "TRH" or below "TRL" in the same patterns described in connection with 216. If one of the patterns of high and low temperature sensor readings at 218 is found and exists for nine consecutive scans, a trip signal is generated to shut o~f fuel to the gas turbine.
If none of the patterns of 218 have not been found for nine consecutive scans of the sensors 50/ then each sensor 50 is examined at 220 to determine whether it exceeds "TR~1" or is below "TRL". If all sensors 50 read within "TRH" and "TRL"
then a new scan of the temperature sensors is started at A in Figure 8. If any four or more of the readings from a single scan of temperature sensors 50 are above "TRH" or below "TRL", in any combination, and such condition exists for nine con-secutive scans, a normal shutdown signal is generated at 222 which is operative to cause the gas turbine to shutdown in a normal sequence.
` While it has been found that the patterns of 216, 218 and 222 reasonably anticipate those temperature patterns or ,: :
~ 51GA 2~63 73~
profiles that appear in the exhaust gas stream for most failure modes of a gas turbine combustion system, it should be understood tha-t these patterns may be varied, for example, as a function of the number of temperature sensors and the type of combustor employed.
While the arrangement of Figure 9 requires the patterns of 216, 218, or 222 to be found during a specified number of consecutive scans before an alarm signal or a trip or shutdown signal is generated so as to prevent transient operating conditions from triggering these signals, it should be understood that the number of required consecutive scans may be varied and may be reduced to a single scan.
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