CA1053915A - Gas turbine control - Google Patents

Abstract

GAS TURBINE CONTROL
Abstract of the Disclosure A fuel and burner variable geometry (BVG) control for a gas turbine engine. Fuel is controlled in response to the product of desired overall fuel-air ratio and a value of air flow derived from gas generator turbine speed. The desired fuel-air ratio is controlled by a speed governor, and by acceleration and deceleration limits varied as a function of measured burner inlet temperature. A compensated turbine inlet temperature (TIT) signal is derived from measurement of actual turbine inlet temperature and acceleration or decele-ration compensation based upon rate of change of the desired fuel-air ratio. The difference between the compensated TIT
and the burner inlet temperature (BIT) is the burner tempe-rature rise.
The setting of air flow control devices in the com-bustion apparatus (BVG) determines the ratio of primary to total air. The desired ratio to control BVG is computed by dividing burner temperature rise by flame temperature rise.
Flame temperature rise is the difference between the desired flame temperature and the measured BIT. The desired flame temperature is scheduled as a function of BIT and BVG. The ratio of primary to total air may be limited temporarily during starting of the engine.

Description

My inv~n~orl rel~tes o contrc~l3 ~o~ gas turbine engine~3 in whidn t~e cs~ ustio~ a~par3~u~ include3 llQe~ns, curta~only call~d burn~r ~ria~le geo~ ry or BV~, to ~ary the xatio of primasy OE cor,lbustion air ~o the to~al air ~
3~ throu.gh ~h2 coT~bus~ion appa3~atu~ sy3~er~ inclu~es means

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3L~535~5 i~or controllirlg fuel flow a~ wall as mean~ for controllin~
BVG. A system according to my invention is particularly adapted ~o the reguiremellts of gas turbine engines w}lich include a freely rotating gas generator w~ich deliver~ motive ~luid to a power turbine which drives a load., My control is adapted ~o control fuel flaw (Wf) and BVG in response to a con~rolling inpu~ of desired engine power output tspecificallY as gas yenerator spee(3) and measurements of gas generator speed, ~urner inlet temperature (BI~), and turbine inlet temperature (TIT) of the engine ~ I
~s adapted to s:ontrol flame tempera~uxe so as to minim.ize production of undesired product~ of c!o~bustion ~uch as oxides of nitrogen and incom~pletely buxned hydrocarbon.
5~h~ nature o~ a control sy~tem according to my i~vention may be appreciated from the following ou~line of the preerred enibodiment. Air Plow through the gas generator : i5 determined as a function of measured gas generator speed.
l~he fuel supplied to the engine is controlled by multiplying this air flow signal by a ~ignal oiE desired :Euel-air ratio.
~l!he fuel~.air ratio ~ignal i5 based primarily upon a control input o:E dcsired gas generator ~peed which ~oacts with a gas generator speed signal to govern gas generato~ spead. ~n addition, th0 desired fuel~air ratio has m~ximum and minimum limit~ which are function~ of BI~a~d which are provided to assure:~lean combustion and avoid lean blowou~s~ among o~her objectiv~3.
A Yalue of compensated TIT is derived ~ro~ corrected , mea~ured TIq~ and co~pensations ~Eor gas senerator ~peed ~ran- ~-~3ients. Specificall~r, the~e tran~ients are representedl b~
30~ unctiol~s of rate o~ change of t~e desired uel-air ratio `~
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;3~15 during 2ccsle~ration or d~celeration of ~h~ ga~ ge~lerator,, ~e ~emperature ri~e ~cro~ the burner i~ deter~ned by ~ub~
~ctir~g the m~sur~d E~IT f~ he comp~n~al:~d ~XT 8i~
~he ~atio of primary to tota~ air flow i~ de~rmined :Ero~
the burner ~er~pera~ure ri~ ~nd the te~per~t:u~e ri~e in S:~IQ
flame or combustion zone of ~he burn~rO q~ lal:ter ~ a ~unction of Bl~ and BVG. B~ a ~unction oiE the de~ired ra~io of primary ~con~u~ion) ~o ~o~l air fl~w. The BVG
signal control~ ~n ac~ tor to vary th~ con~:'igura~ion o 10 the burner.
A featurQ of the inv~ntion i~ that c:ombu~tion Z021e tem~r~ture, which i3 the large co~rolling f~cto~ in ~he generat~on of undesired co~ibu3tion product~ ontroll~d $~depend~ntly of the burrler outlet temperature (TIT) by varying the burner geometxy. Anokher fe2ture i~ ~hat control of the ~urner geanetry i~ e~fected by m~a~urernent o~@ TIq~ and .

BIT. Amo~g t~he advan~ageou~ re~ul~ of t~e c~nt~ol ~re ~ha~
3ao a~ient temperature c~mpen~atlon i~ requi~ed an~ lik~ise no warm-up ~ 3ns~tion ~uring 3tart o the engine,, Al~o, 20 direct ~asuremsnt of flam~3 te~np~sra~ure i~ avoided.
q~e principal objects o~ my invention are to impxove t~e ~per~ormarlce o~ ga8 tu:rbin~ enS~ine~" particularly th2 e~i~ n characteri3tic~ of ~uch eng~ne~ to E~rovide 8il11p1el ade~uate co~trol for the bu~aaer v~riable geometEy of turbin~ engine~ nd tc~ pr~ride ~uel and buJ:n2r Yariabl~
g-aaetry cvntrol~ whic}l zlre responoive to input~ o ga~ ~:
ger~ral:or a~tual and reque~ted pe~ds~ ~urner inlet t~mpe rature, and burner ou~le~ temp~ra~e.
~e rlaturs o~ s~y inventis~n ~nd it~ ad~ntage~
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1~539~L5 ~e more fully ap~arent fro~ ~he succeeding detailed descrip-t~o~ of the ~re~erred embodiment o the invention and the acoomFanying drawings thereof.
Figure 1 is a schema~ic diagram o:~ a regenera~ive ~as-~oupled gas turbine engine wi~h buxner variable geom~try~
Figure 2 is a plot illu trating factors involved in scheduling flame temperature as a fun~tion of burner variable ~-geometry.
~ ig~re 3 is a schematic diagram o a control system fox an sngine such as that shown in Figure 1.
Figure 1 illustrates a well known type of gas turbine ~gine. The engine includes a compressor 2 which takes in ~tmospheric air and delivers it ~hrough one pass of a heat exchanger 3 (a regenerator or recuperator) to a comb~stion apparatus or ~ner 40 The combu~tion appara~us includes the ual hou~ing or outer case 6 which receive~ the compressed ~ir and a c~mbustion liner 7. Fuel is supplied to the ~om-~u~tion liner through a fuel line 8. The fuel is burned inth~ air within the liner and the ~ombustion products are delivered thro~gh a duct 10 into a:turbine 11 to pro~ide ~otive fluid or the turbine. The turbine 11 i~ coupled through a ~haft 12 to the compresso~ to drive the compres or.
~he portion~ of the engine thus ~r des~ribed consti~ute a 9a5 generator. The~hot gaces exhausted ~om the ~as ge~erator : ::
: provide ~otiYe ~luid for an independently rotatable p~wer tu~bine 14. It:will~be realized that these turbines m~y be ~:
:coupled t~get~er ~y power transfer means s~ch ~s tho~e des-: . :
crik~d in Flanigan ~t al U.SO patent ~o. 3~237,404 ~rantedrch 1~ 6. Turhi~e~14 drlves a p~wer output ~ha~t 15 ~30 w~ioh m~y k~ con~ected through a suitabl2 trangmi~si~ tc) the ~ ~ , ' ' ' .

~0539~L5 driven load ~,~icn may, for example, be tha road wheels o~
a vehicle" The trans~ssion or load may limit the speed of turbine 14, or it may be otherwise limited" ~he exhaust from turbine 14 is led through a duct 16 and the other pass of heat excharlger 3 to an exhaus~ pipe lS~ e engine may ~e ~tzlrted by cranking ~he gas generator b~r any suitable ~arter 19.
Fuel i9 supplied to the cc~rr~uætion apparatu~ ~rom - any suitable source, s~xdinarily by a pump driven by the engine, ~ illu~trated. Pump 20 is driverl b~ a power take-o$f drive 22 from 3haft 120 although it could ~ otherwi~e driven. ~he power takeoff drive also drives a gas generator speed transmitter or Nl sen~or 23. As illustratedO pump 2û
~upplies fuel through a throttling or ~low controlling metering ~lve 24 into line 80 ~he rate of ~low through ~:
valve 24 i~ controlled by a 3ui~able actuator 26 whic~
prefexably electrically controlled.
q~ho~e ~lcilled in the art will recognize that fuél :
con~rols for a ga turbine engine ~Lay include other elemen~s not shown hereO paxticularly a head regula~ing ~y-pass valve w~i~h by~ ses excess p~np discharge to khe pump inlet und~r ~ach control as to maintain a constant pressure ~rop ~cross the~ metering valve 24.
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; ~ The tem~?erature o~ the aix enterinq the combustion app~ratu~, identified as T3 or BIT6, is measured by a ~ui~able thermooouple or oth~r sensor 27. q!he temperature o the motiv~ ~lui~ delivered to the ~urbille, 1d~3ntified as turbine .
inlèt t~mE~rature or q!4, i~ measured b~ a th~rmocc)uple or the like 2~ mounted on duc~ 10~, q~he ccsr~ustion apparatus 4 is of a variab~e geometry ~: ~
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: ' 39:~5 typa~ as illustrated sc~ematically~ q~e fuel entering fro~
line 8 is atomized or evaporated and burned in the upstrear~
end of the liner 7. Primary or co~u~ion air is supplied near the up~trea~ end of the liner through ports 30.
Dilution air (the xemainder of total air) i~ supplied near the down~tream end c~f the liner through ports 31. q~he are~s of these ports are ~aried by sleeves 32 an~d 34 recipro~able ~long the combustion liner so as to vary reversely the area o~ ports 30 and 31, or by other ~uitable means. ~s illus-trated, sleeves 32 and 34 are connec~ed ~ogethar and to a~
actuator 35 through the pull rod 36. ~or those in~erested in the detail~ of a combustion appara~us suitable for an enginc of the type described ~ere, re~rence m~y be rQade to Ander~on et al U.S. patent No. 3,85g,787 i~sued January 14, 1975. mi3 ~?atent describes the operation of a co~bu~tion chaTr~er including variable geometry to contrc:l t~e flow oi~
primary and ~econdary ai~. Obviou lyt the ratio of primary ;
' air to to~al air ~low is a functic:~ of the posi~iorl oiE the sleeve~ and =y be readily determined for any particular configuration of con~bustion apparatus. me ports Iflay be (::
conigured to provide a desired or suitable ran~e and ~urve of the ratio of primary to total air ~low as a fun~tio~ of the position of the actuating rod 360 It~will be cle~ to tho~;e ~killed ~n t~e art tha~
the t~np~rature rise in the: com~ustion apparatus; that is, the diS~erence ~tween :tempe~cature :of the air entering th~
co~bustion apparatus and that entering the t~ine is a . .
direct function o~ the ratio of ~fu~l to a~r. Thu, ~X~ is a :; dire~t ~unction o his ratio plus BIT. me ~empera~ure 30: r~se ~om BIT to temperature i~ the co~bu~tion ~vne of the ~ .

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b~ner (fla~e temperature) is a direct function of the r~tio of fuel to primary aix. Obviously, fla~e temperature will the 81~1tl of` this t~m~eratl~re rixe and ~IT,.
It follow~ fx~ thi~ tha~ the ratio o~E primary aix to tot~l air egual~ the ratio o~ t~IT minu~ B:1:5r) to ~la~
~e~pe~ature minu~ BIq~) ., ~is rela1:ion i~ u~ed a~ a l~
o~ s~y. ~yster~ o:E controlO It i~ well Isnown to ~ose ~killed i~ the art that too high flame tempera~ure~ lead to production of unde~ired amount3 of nitrogen o~id~. On the other hand, 10 tos low ~lame tesaperatu~es are l~ l~ely to le~d to delivery t~f ~uch pollutarlts as carbon monoxide and other unburned hyl3ro-~arbon products. ~ Also" too high a flame ~emperature may danage tho ~lame tube Wall3 and too low a cor~bu~tion ternpe-rature leaas to uns~ahle con~bustion ana difficulty with fl~eout~ of the co~bustor, particularly during deceleration.
e xelations a~e illu~tra~ed for a typical co~ustor by ~he curves of Figlare 2. ~ ~ ~
~ he abscissa in Figure 2 i~ BVG position with ra~io ~- ~ pri~ary to total air increasing fro~ le~t to right on the 20 d~gra~n. Ra~io of pri~a~y to ~otal air is approxima~ely a lin~ar ~ction o burner variable geomatry in the part~cular app~atu~ urlder discussion here. 1~e ordin~te is ~lame temperatur2. It may be ~180 pointed ou~ t~a~: th~ l~w BV~
osltion: in other word~, low ratio of prinary to total ~ir . .
atterlded ~ hi~Th re~idence time in the fla~e zoneO
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;`: A~dl Wi~ll inc~eaaing :pri~ry aiir ~law the residallce tim2 decrea~-3 . Produ :tlon o undesired nitrogen o~cides is a fun~ion of r~ide~ce time as well as temperatuxeC tQnding :
: t o in~rea~ wi~h both. Ot~ other hand~ increasing :~
30 ~ ro~idenc~ time ten~ to ~inimize ~canplete c~u3tion.

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~53~L5 I~ ~igure 2, the shaded line 38 illustrates an upper l ~ it to flame temperatuxe based upon un~u~ production o~
nitrogen oxide. The shaded line 39 is a limit Lmposed to aYoid unduly high combustion liner wall te~mperature. Th2 sh~ded line 40 rep~esents a lower limit of 1ame temperature below whi~h ~lameout is likely, otherwise known as the lean ~lowout l~mit. A fouxth line 42 repre~ent.~ combustion conditions which lead to undesired level~ of carbon monoxide in ~he combustion produc~s. It will be seen tha~ a æuitable zone for combu~tion lies between these lines and~ of coursa, that the actual combustion conditions may be ~aried to some ~xtent to achieve the most desirable overall perfoxmance in terms o~ clean com:bustion and responsive performance of the 5~as turbine engineO
q~he line 43 on Figure 2 rel?resents a preferred ~ontr~l schedule o~ flame tempsrature for a pax~icular a~gine. In this case the con~rol o~ variable geome~ry i~
~ch~dul~ so as to provide a flame temperature o approxi~
mately 1200 & . through abou~ ~he ~ir~t third o ~e schedule with incra~sing ratio of pri~ary to total air, then a gradual aecrease to about 1140 C. through appr~ximately another third of t~a curvet and ~hen control to give 1140& ~ flame tempe-ratur~ i~ the hig~er power operation o~ ~he engin~. It hould be unders~ood that these refer ~o flam~ emperature a~d ~ot to burner discharge tempera.ur2 (~IT).
~i~h thi~ introduction~ we proceed to discu~ion of organiza~i~n of the preferred control system as set out in Fig~re 3 where it will be no.ed the ~1 tran3duceE 23, BI~
transducer 27~ ~IT transauc~r 28, fuel me~.ering valv~ 240 `30 actua~or 26, ~VG 32, 34, and ac~at~ 35 are indicatlsd ~ , :

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3~Ji5 ~ ematically. In addition to the inputs representing c~n-ditions in the engine; a speed setting or governor ~etting device is repze~ented by the elemen~ 44 be,aring the legend in ~1 set which may, of course, be a thro~tle lever or accelera~or pedal to con~rol ~he speed of the gas generato~
~nd thu~ engine power level.
q~he ~chematic of Fi~ure 3 may be taken to represer~t ~n el~ctrical or electronic sy~em in which signal~ are ~epre~en~ed by currents or voltages or ot~er electrical .10 ~uantity or to represent a mechanical, hydrome~hanical, or otber ~yskem 90 long a~ the sy~tem contain~ element~ which can perform the anal~g calculator func~ions de~cribed in the succeeding text. For various reasons ~uch a~ economy and compaetne~, electronic circuit computing and function ge~erating units are preferred or the engine co~rol. Such ~ystem~ include function genera~or~ which act as equivalents of ca~s to generate an ou~put of particular desired functio~
of an input. ~hey include various types of gates, multiplying a~ dividing circui~, adding circuit~, and circuit~ for 20 generating inte~ral an~ di~erential signal~ o~ mixtures of ~:
.the~e ~or stabili~ation or co~pensating purposes. We will not enter into description of the details of such known elements of co~trol ~ystem~, since it is not nece~sary or ~nder~tandin~ the inv~ntion or for practice of the invention by ~ho e skilIed in the artO
~ s sh~wn in Fig~re 3, th~ ~as generator speed signal ~ro~ transducer ~3 is fed to a ~fu~ctio~ generator 46 w~ich develops an o~tput ~ignal repr~.senting ~he sch~duled we~.ght :~ o~air deli~e~ed in unit time by the compxessor for the : 30 pD~tiC ~1ar rotati~al speed. ~h~ approxim~te sh~pe oi th~s ' .

~ (~5~9~5 enrve is indicated on the schematic. The scheduled weight of aix signal i~ txans~itted to a multipli~r 47 where it i~
~ultiplied by a signal of a de ired ratio of ~uel to air by weigh~O The produ~t i~ the de~ired w~ight o~ fuel flow in unit t~meO Thi~ signal is tran~mit~ed to a function generator 48 which may ~nclude a driver f~r the actucltor 26 and which develops an ou~put current I~ which, ha~ing regard to the characteristics of ~he actuator and of ~alve 240 will provide the xa~e of ~uel flaw ca~led ~or by the inpu~ signal ~o the ~nction generator 48.
~ hi8 b~ings us to the matter o generation of the desired fuel-air ratio signal, which is the other input to multiplier 47. A function generator 50 generate~ a 3ign~1 of acc~leration fuel-air ratio (maximum acceptable fuel-air ratio) based upon an input o~ BI~ ~rom sen~or 27. A ~econd ~u~t~on gen~rator S1 generates a signal of dec~lerat~on fuel-air ratio (mi~imum fu~l-air xatio to ~kirt lean b~owouts~
lik~wi e based ~ the input of BIT. Both these uel-air ratios decrease a~ BIT increases~ The~e ~rve to compensate 20 f~r amb~ent temperature and for te~perature rise in the ~ompressor and regenerator.
The ~hir~ inp~t to determLne fuel-aix ratio i~ ~rom a ga8 generator governor which con~rols engi~e speed by controlling fuel-air ratio and thereore fu~l sup~ly during ~teady ~ta~c operation. m e governor circuit re~sp~nd~ to an i~pu~ o~ desired gas generator speed f~om the operator n~ol 44 which is fed a5 a po~iti~re ~put into an addi~g ~levic~52 and the input o:f ga~ generatvx speed ~rom ~he : ta~ho~eter 23 w~ich is fed to tha addLng ~e~ice as a ~'~u~
~ign~l. me ou~pu~ 0~ ~dder 52 is thus prop~xti~nal to the 539~S
~ ed error and is positive if gas generator ~peed i~ bel~w t~ reque~t and negative i~ it i.~ above. q~iis ~ignal i~ ~ed to an integrator 54. The integrator pUt8 !~Om~ lag into the o stabilize the governing ~ ction and ~o slow the r~te o~ fuel changs in response to change~ i.n speed request 80 a~ ~o promo~e proper oper~tion o~ the 33VG~ control. A
si~nal i8 tran~mitted from the integrator 54 through a minu5 only gate 55 Z~3 a governor ~uel~ ratio ~3ignal to another adding device 56 where thi-~ ~ignal i~ added to thc ~0 aeceleration uel-air ~ignalO Since the governox ~ignal is negative, it i~ ~ubtracted from th~ acceleration uel-~ir ~ .
3ignal to provide ~ ~ignal on a channel 58 into a E!igh Wi~s yate 60,. A3~aing that ~he engine i~ running ancl an 13lcrease in speed i8 ~alled for, the goverrlor fuel-~ir ~atio ~ignal be~:Ome8 zero~ q!he sign~L on chalmel S8 therefore wlll equal the maximum ~uel-air or acc~leration ~uel-~ir or the partioula~ burn~r inlet l;emperatu~e. Acceleratiorl of the ga3 g0nerator will ultima~ly bring Nl up ~o ~nd above : tha level of the requ~t, at which point a nega~ive signal 20 1~ fed through the governor fu~l-air ratio channel into the add~ng dev~ce 56~. q!his signal reduce~ t~he ~ig~al on line 58 ; .
progressively until the ~uel air ratio is ~uch a~ to hold the gas g~nerator speed at khe re~ested ~lue.
I~ the æpeed signal fro;n input 44 is decreased~ th@
r~3sult i~ a~ ov~r~peed ~ignal f~o~ the governor which pro-: :~ : gr~ssiv~ly reduces the signal on chann~l 58 into the High W~ gate 60. Fuel thus decrea~es at a rat0 det~mined by the con~tants o~ the: int~gratin~g circu~t 54 urltil t:~he signal .
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on channel 58 ~ecomes l~s~ than the deceleration fuel-~ir ra~io si~nal on channel 59 fed into the ~igh ~ins gate 60.
~he output of t~e High Wins yate thus ca~not drop below the deceleration fuel-air ratio ~ignal. When the speed drops to the requested value, the gs~ernor again takes over and e~tablishe~ a fuel rate between the accele:ration a~d ~ecele ration limit.
Thi~ conclude~ ~he description of the mode of con-trolling uel flow to the engine. ~s will be seen, the uel .10 flow is ~etermined by a -~peed re~uest rom ~he ga~ generator speed setting input 44 and measurements o~ the two para~e~exs of gas generator speed and burner inlet temperature.
Proceeding now to th~ control of burner variable geometry tB~G). this i~ determined as a function o~ the ~Iq' 3ignal, the TIT ~ignal, and he desired fuel-air ratio signal ~he generation of which ha~ just been described. l!he con~ol~
do not depend directly upon the measurement of TIq~, ~ut rather upon a compensated TIT signal t:he generation r)~e w~ich i8 a~ 40110w~ he signal of TIT from ~e thermoc:ouple 28 20 iæ fed ~o a correcting circuit 62 which essentially adds a derivative term so as to c~rrect for the tim~ lag of the thermocouple. Such correcting circuit-q are well kno~ and need not be des~ribed at this point.
The ~orrected signal o$ measured TIT is fe~ thro~gh cha~el 63 into an adding device or circuit 6~. ~ere the ~i~al i3 compensated to provide the compen~ated ~IT si~n~l - : ~rom whie:h BIT i~ slibtracted to determi~ne the signal of T~ or burn~r temperature rise. me compensation involYes additi~al inputs~which refLect th~ effect of tran~i~nts . .
30 during accelerati~ and deceleration o ~e ga~ ~enexa$or~
, )539~5 The desired fuel~air signal from ~hannel 61 is supplied to ~wo derivaltive circuits or devices 66 and 67 which generate signals which are primarily deri~tatives oiE the fuel-air ~i~al and thus have a magnitude increasing with the rate of change of de~ired uel-air. me reason or having two su~h circuits is that the compensat ion during acceleration i8 d~fferent from that during deceleration in the particular installation described here. q~he output of derivative cireuit 66 is fed Ithrough a plus only gate 68 and th~ signal from 10 derivative device 67 through a minu~ only gate '10 as positive inputs to the adder 64. me gates 68 and 70 a~ure that the E~gnal i~rom derivativ~ circui~ 66 does raot reach the adder 64 when the fuel-air ratio i~ decreas~ing and the signal from dexivative device 67 does not reaGh tha adder when the engine l~ accelerating. If it were considered s~tis~actory to have . . .
the sam~ compensa~ion for both acc~leration and deceleration, a singie derivative device such as 67 could be conne~ed directly to the adder 64 without the gate and the other d~rivative device and ga~e could be omitted. The acceleration dexi~ative signal is instrumental in avoiding ~Qx peak~ and the decelerati~n derivative signal in avoid1ng lean blowouts during 3peed transients.
The compensatad TIT ~ignal is fed to an adder 71 in which the ~ignal o~ ~u~ner inlet temperature ~rom ~ensor 2 : i8 s~b~racted from the compensated TIT signal. The ~esult a si~al ~ burner temperature risc ~ TB which i8 fed : .
khrough a channel 74 1nto a dividing device or circuit 75O
~lere this sigrlal i~ divided by the ~lam~ tem~peratllre rise ~ :~ignal, t~e generatiorl of w~ich will ~e described, to arrive : 30 at the ~ignal oi~ ratio o:E prim~ry to t:otal air ~3d through a , .~, . .
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~153~5 channsl 76 in~o a ~c~ion genera~or 78. ~ ction generator txanslates the pri~ary to total ;air ratio signal into a signal of desired burner variable g~sometry position.
me nature of ~hi~ function is simply a ma~tter of the curve o:E ratio o pri~ry to total air plotted against the position of the burner variable georne1:ry, which can be d~termined ~y ~ea~uremen~ and whi<:h can be altered by re~shaping of the ports or ~hrottling sleeves in the conibustion ap~aratus.
me desired burner variable geometry sig~al or 10 channel 79 is fed ~ack to a lame tempera~ure schedulin function generator 800 l~i generates the curve 43 illu~-t:rates3 i~ E'igure 2 which, as described above, represen~ the de~ired schedule of ~lame temperatu:re as a ~unction of burner ~axiable ge~metxy and there~ore ffl re~idence t~e and other factor~ e co~hu8~ion ap~ratu~.
Ar~o~her factor that enters ir~to tha determination oi~ ~e~ired i~lame temper~ture i~ a ~ompensation for burneP
inlet t~np~:rature. In other wordsO ~nst2ad o ~imply ~
- ~ tractirsg the b~rner ir~let ~emperature from the ~la~ne tempe-2Q ratuxe ~ch~dule to arrive at the temperature rise in the con~bu~tion zoneS a comi?ensatiorl factor i~ ~ed in. q~e reas~n ~r ~his i~ that it ha~ been 40~d in a regenerative engine ~t ~here i~ a tende~cy to high emi~sia~ o:E aar~n ~n~noxide ~: and o occa~ic>nal ~ean blowout~ during the pe~iod o~ warm-up o~ the regenerator aftex startingO I~ the reger~erator i~
cold, ~he air fed to the co~bustion appara~us is much colder (on the order of 500 C. colder~ than w~eI~ the eagine is in Dc~r~l operation after the regenerator ha~ bee~ heated. For ~hi~ xeas~, an input of actu~l ~uxner inlet tempera~ure i~
30 3Eed to a function generator 8~ which provide~ an output .
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~)539~L5 ~ignal which i~xl the particular ca~e i~ constant at about 600 C. up t~ about 260 C~ BIT and t~en generally linearly arops to zero at about 600 C:. BIT. q~li8 co~n~eting ~3ignaî
i~ added to the Plame temperature s~hedule ~ignal ~ an add~r 83 tlla output o~ which is a de~irsd flam~ temperature ~ign~ channel 84 o l~ re~ult o~ ~he compens~tion i8 to call for ~ high~r flame tempera~ur2 when ~he r~gen~3rator i8 coLd,, 1~ c~Ll or higher flame temperature re~ult~ in flow o~ primary air to th~ co~bu~tion zone.
The flame tempsr~ture ri~e ~ l i9 derived f2~0Jn the desired ~Elame ter~perature by ~ubtra~ting BI~ from it in an ~ddar 86. The x~sulting sign~l i8 th~ di-vi~or supplied to the dividing device 75 to g~nerate the ~ignal of ratis: of primary to tot~l air previously ref~red lto~
completes t} e description o~ normal circuit or con~olling the burner variablQ geometry aad thus ~he split betwe~n primary a~d R~condary airl, ~n a particular -:
' engine it Wa8 :FourldO however, that better ~rting condition~
w~r~ a~r~ved a~ ~ limiting the ~7urner variable geomei:ry 20 ~tting to li~ the ratio of p~imary to total air for a tim~s durinç~ crEanking or ~rtirlg of the engin~ i8 acco~plished by putting a t~mporary li3nit Ol~ the ~ignal t~am3~itt~d fro~ line 79 i~to the burner ~rial:l~ gec>roe~ry æctuatos 35. ~li8 is zlccompli~hed by a conne~tion ro~ th~
~tart2~ or ~tarter erlergizing circuit8 lg into a ~ sr 87.
For a tilae a~t~r st~rting this ti~r generat~s a signal oi~
~xl~Q~ bwener v~riable ge~et~y whi~h ~ trArl~tt~ad throug~
ch~nnel 88 into a Law l~n~ gat- 90 whicll a~læo r~/~eisre~ th~
a31~sired burn~r v~ria~le ~o~t~y ~ignal ~rom ch~nnel 7~.
3Q After thi~ nited time,, which anay be o~ the o~der o~ 25 ', ': ~

- . .. , , :

53~L5 ~ec~d~, ~he tim~ ~.ignal ri~e3 above ~e maximum burn~r variable geomet~y so th~ the signal from f~c~ion generator 78 talces over control o~ actuato~ 35 of the burner variable geane~ry.
The ~y~teJn as des~xibed above ~chedul~ss ~lame temp~
~ature s~s ~ un~:tio~ o B~r and B~IG. I~ should be pointed out th~t other parameter3 may ba u~ed to sc'hedule ~lam~
temper~ture i ~o dasired~ Pla~s ~emparatu:re may ~ related to or ~cheduled i~rc~m en~ine ~peed, ct)~pres~r ~rariabl~
g~o~netry, or mas~; flow OVe~I:' pres~s ~ign~
It ~i~ eezl that ~he b~ner variabl~ gec~n~etry a~ontrol is a ~y~tem which T~ay be very simply irnplemerated by sta~dar~ electronic c:omponents to provide the function g~nerators, adders, multiplier" an~ divid~r,, It can also b~ implementPd ~echanically or hydroTrlec~anically if de~irQ~, a~ i8 well Xncwn to tho~e akilled in t.~e art of as~alog - c~nputing devices~. Cal$bration o~ the cale~ a~d curve nhapes o~ control elem~3nt~ is based a~ lasual on engine te~t~.
It should be appare~t to ~hQse skilled in *he art from ~he foregs~ng that my ~y~tem providles a very ~imple and -~
re~ponsi~?e ~ystem :Eor ~:on~olling ~uel and burner variabl~
gaor~atryO It xe~re~ r~latively simple andl e~l5ily gener~tad inpul~ and provide3 a ~ontrol which i8 ~ Eectiv~ to optimi20 air split ~ lthe ~:o~u~or and th~reby op~i~ize emi~sion~
Wit~QUt pre~uaici~g ellgi~ r~38pOn82 any more ~han iL~ :
~qui~it~
d~tailed de~c:~iptiorl o~;:the pre~erred ~r~odimer~
of ~he invention for th~ pu~pos~: of ~xplaining t:he principle~
:th~r~of ;i8 not to ~e c~sider~d a~ l.imiting or restric?tiL2lg th~ lnYenti~n~ sinc~ y r~odification~ may be ~nade by t~g ex~rc~a of s~cill is~ ~he art.

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.. ~ . . . . . . .

Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A control system for a gas turbine gas generator including a combustion apparatus with burner variable geometry (BVG), the system comprising, in combination, means operative to derive a fuel-air ratio signal; means responsive to the difference between turbine inlet temperature and burner inlet temperature (BIT) effective to generate a burner temperature rise signal; means effective to generate a flame temperature rise signal responsive to the difference between a signal of the desired flame temperature and BIT; means effective to generate a signal of the desired ratio of primary air flow to total air flow by dividing the burner temperature rise signal by the flame temperature rise signal; means responsive to the said desired air flow ratio signal operative to driven a BVG
signal; and actuating means responsive to the BVG signal operative to control burner variable geometry.

2. A control system of a gas turbine gas generator including a combustion apparatus with burner variable geometry (BVG), the system comprising, in combination, means operative to derive a fuel-air ratio signal; means responsive to the difference between turbine inlet temperature and burner inlet temperature (BIT) effective to generate a burner temperature rise signal, the last-named means including compensating means responsive to transients in the fuel-air ratio signal; means effective to generate a flame temperature rise signal responsive to the difference between a signal of the desired flame tempe-rature and BIT; means effective to generate a signal of the desired ratio of primary air flow to total air flow by dividing the burner temperature rise signal by the flame temperature rise signal; means responsive to the said desired air flow ratio signal operative to derive a BVG signal; and actuating means responsive to the BVG signal operative to control burner variable geometry.

3. A control system for a gas turbine gas generator including a combustion apparatus with burner variable geometry (BVG), the system comprising, in combination, means operative to derive a fuel-air ratio signal; means responsive to the difference between turbine inlet temperature and burner inlet temperature (BIT) effective to generate a burner temperature rise signal; means effective to generate a flame temperature rise signal responsive to the difference between a signal of generate a signal of the desired ratio of primary air flow to total air flow by dividing the burner temperature rise signal by the flame temperature rise signal; means responsive to the said desired air flow ratio signal operative to derive a BVG signal; actuating means responsive to the BVG signal operative to control burner variable geometry; and means operative to derive the desired flame temperature signal, the last-named means including a first signal generator responsive to burner inlet temperature, a second signal generator respon-sive to the BVG signal, and means for combining the outputs of the said signal generators.

4. A control system for a gas turbine gas generator including a combustion apparatus with burner variable geometry (BVG), the system comprising, in combination, means operative to derive a fuel-air ratio signal, means responsive to the difference between turbine inlet temperature and burner inlet temperature (BIT) effective to generate a burner temperature rise signal, to last-named means including compensating means responsive to transients in the fuel-air ratio signal; means effective to generate a flame temperature rise signal respon-sive to the difference between a signal of the desired flame temperature and BIT; means effective to generate a signal of the desired ratio of primary air flow to total air flow by dividing the burner temperature rise signal by the flame temperature rise signal; means responsive to the said desired air flow ratio signal operative to derive a BVG signal;
actuating means responsive to the BMG signal operative to control burner variable geometry; and means operative to derive the desired flame temperature signal, the last-named means including a first signal generator responsive to BIT, a second signal generator responsive to the BVG signal, and means for combining the outputs of the said signal generators.

5. A control system for a gas turbine gas generator including a combustion apparatus with burner variable geometry (BVG), the system comprising, in combination, means responsive to gas generator speed operative to derive a scheduled air flow signal; means responsive to burner inlet temperature (BIT) operative to derive maximum and minimum fuel-air ratio signals, means responsive to gas generator speed and a gas generator speed request operative to derive a governor fuel-air ratio signal, and means responsive to the three said fuel-air ratio signals operative to derive a desired fuel-air ratio signal; multiplier means responsive to the air flow and desired fuel-air ratio signals effective to derive a fuel flow signal; fuel control means responsive to the fuel flow signal operative to control fuel flow to the combustion apparatus;

means responsive to the difference between turbine inlet temperature and BIT effective to generate a burner temperature rise signal, the last-named means including compensating means responsive to transients in the desired fuel-air ratio signal;
means effective to generate a flame temperature rise signal responsive to the difference between a signal of the desired flame temperature and BIT; means effective to generate a signal of the desired ratio of primary air flow to total air flow by dividing the burner temperature rise signal by the flame temperature rise signal; means responsive to the said desired air flow ratio signal operative to derive a BVG signal;
actuating means responsive to the BVG signal operative to control burner variable geometry; and means operative to derive the desired flame temperature signal, the last-named means including a first signal generator responsive to BIT, a second signal generator responsive to the BVG signal, and means for combining the outputs of the said signal generators.

6. A control system for a gas turbine gas generator including a combustion apparatus with burner variable geometry (BVG), the system comprising, in combination, means responsive to gas generator speed operative to derive a scheduled air flow signal; means responsive to burner inlet temperature (BIT) operative to derive maximum and minimum fuel-air ratio signals, means responsive to gas generator speed and a gas generator speed request operative to derive a governor fuel-air ratio signal, and means responsive to the three said fuel-air ratio signals operative to derive a desired fuel-air ratio signal; multiplier means responsive to the air flow and desired fuel-air ratio signals effective to derive a fuel flow signal; fuel control means responsive to the fuel flow signal operative to control fuel flow to the combustion apparatus;

means responsive to the difference between turbine inlet temperature and BIT effective to generate a burner temperature rise signal, the last-named means including compensating means responsive to transients in the desired fuel-air ratio signal;
means effective to generate a flame temperature rise signal responsive to the difference between a signal of the desired flame temperature and BIT; means effective to generate a signal of the desired ratio of primary air flow to total air flow by dividing the burner temperature rise signal by the flame temperature rise signal; means responsive to the said desired air flow ratio signal operative to derive a BVG
signal; and actuating means responsive to the BVG signal operative to control burner variable geometry.