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Ben­e­fit from Knowl­edge and Ex­pe­ri­ence

Here you can find out more about the top­ics and chal­lenges where we have been able to apply our ex­per­tise in the past to de­vel­op and im­ple­ment project-spe­cif­ic so­lu­tions for our cus­tomers.

Some IfTA Ref­er­ences

Siemens Energy CEC (Clean Energy Center)

Siemens en­er­gy - CEC
burn­er test rig

Prod­uct: Ar­gusOMDS

In­ves­ti­ga­tion of com­bus­tion os­cil­la­tions in gas tur­bines under real con­di­tions.
 

More In­for­ma­tion

Service on gas turbines

Sig­nal Test­ing on Ga­s tur­bi­nes

Prod­uct: Charge sig­nal Gen­er­a­tor

Mea­sure­ment chain test­ing on sta­tion­ary gas tur­bines for power gen­er­a­tion.

More In­for­ma­tion

SWM Mu­nich, early
warn­ing sys­tem

Prod­uct: Ar­gusOMDS + Pre­cur­sor

In­creas­ing the ef­fec­tive­ness of gas tur­bines by using an early warn­ing sys­tem.

More In­for­ma­tion

MTU &
UniBw M

Prod­uct: AIC-Sys­tem

Aero­nau­ti­cal re­search pro­gram for ac­tive com­pres­sor con­trol.

More In­for­ma­tion

Large fur­naces in in­dus­try

Prod­uct: con­sult­ing and ser­vice

Avoid­ance of com­bus­tion os­cil­la­tions in dif­fer­ent­ly sized large burn­er ge­ome­tries.

More In­for­ma­tion

Small Fur­naces in daily life

Prod­uct: con­sult­ing and ser­vice

Avoid­ance of com­bus­tion os­cil­la­tions in gas ovens, large kitchen and heat­ing ap­pli­ances.

More In­for­ma­tion

Sie­­­mens En­er­gy, CEC Lud­wigs­felde - Burn­er Test Rig

Pro­duct: Ar­gusOMDS

  • Ini­tial Si­t­u­a­tion
  • The Chal­lenge
  • The IfTA So­lu­tion
  • Cus­tomer Value

With in­tel­li­gent vi­bra­tion mea­sure­ment tech­nol­o­gy to clean en­er­gy

The in­creas­ing use of re­new­able en­er­gies from pho­to­volta­ic and wind power leads to an in­creased de­mand for elec­tri­cal en­er­gy that can be gen­er­at­ed quick­ly if there are fluc­tu­a­tions in solar ir­ra­di­a­tion or wind sup­ply. Modern gas power plants bridge this sup­ply gap per­fect­ly be­cause they start up quick­ly and vary their out­put over a wide range. This com­plex in­ter­ac­tion is sig­nif­i­cant­ly sup­port­ed by in­tel­li­gent vi­bra­tion mea­sure­ment tech­nol­o­gy. The gas and steam tur­bine (CCGT) op­er­a­tion has a very good ef­fi­cien­cy with low CO2 emis­sions at the same time - about 60 % less than from brown coal power plants. The cur­rent­ly most mod­ern power plant of this type is lo­cat­ed north of Mu­nich in Irsching and has an ef­fi­cien­cy of 60.75%.

Test bench­es for op­ti­miz­ing gas tur­bines

Siemens En­er­gy has built an ultra-mod­ern test cen­ter, the Clean En­er­gy Cen­ter (CEC) in Lud­wigs­felde, near Ber­lin. There, in­di­vid­u­al gas-tur­bine com­bus­tors are op­er­at­ed under high- pres­sure and pre-heat­ed air or gas con­di­tions – in other words, under re­al­is­tic con­di­tions. In ad­di­tion to emis­sions, ther­moa­cous­tic phe­nom­e­na – also known as com­bus­tion dy­nam­ics – in the com­bus­tion cham­ber and the dy­nam­ic loads on ma­te­ri­als are also part of the CEC's in­ves­ti­ga­tions. To mea­sure these sig­nals, high-tem­per­a­ture pres­sure- and, ac­cel­er­a­tion sen­sors, strain gauges and var­i­ous other sen­sors are used.

The fol­low­ing chal­lenges had to be man­aged at the CEC:

  • Ex­treme con­di­tions of a com­bus­tion cham­ber - high tem­per­a­ture and high pres­sure, which the com­po­nents used have to with­stand
  • The oc­cur­rence of dan­ger­ous ther­moa­cous­tic vi­bra­tions, which re­quires per­ma­nent mon­i­tor­ing
  • Con­tin­u­ous mon­i­tor­ing gen­er­ates a large amount of data that needs to be pro­cessed
  • The pro­cess­ing of the data and anal­y­sis must be done in real-time
  • The test rigs must be re­li­ably pro­tect­ed, i.e. when crit­i­cal val­ues are reached, a re­ac­tion is re­quired to pre­vent major dam­age

The IfTA So­lu­tion

Planned orig­i­nal­ly as IfTA Dy­naMaster sys­tem and later up­grad­ed to an IfTA Ar­gusOMDS, IfTA vi­bra­tion mea­sure­ment sys­tems are part of the ad­vanced tech­nol­o­gy at CEC in Lud­wigs­felde. The sys­tem in­stalled is a fur­ther de­vel­op­ment of the proven IfTA Argus sys­tems that have been in use in var­i­ous types of gas tur­bines world­wide for over a decade. For the spe­cial mea­sure­ment re­quire­ments of a burn­er test rig, a new flex­i­ble input mod­ule was de­vel­oped at that time, the IfTA AD4Pro. More­over, test rig data are record­ed to­geth­er with dy­nam­ic sig­nals to fa­cil­i­tate anal­y­sis - both on­line and off­line. In ad­di­tion, the con­trolled ac­qui­si­tion of mea­sure­ment points and time ag­gre­gat­ed and av­er­aged data has also been re­al­ized.

Flex­i­bil­i­ty by mod­u­lar­i­ty

All of the CECs test stands are equipped with 32-chan­nel IfTA Dy­naMasters. All chan­nels are si­mul­ta­ne­ous­ly sam­pled for phase-syn­chro­nous mea­sure­ments using 24-bit ADCs and at rates of up to 51.2 kHz. The high-speed ana­log in­puts can be tapped via buffered out­puts. This vi­bra­tion mea­sure­ment sys­tem is round­ed off by a pow­er­ful mod­u­lar soft­ware plat­form. IfTA Ar­gusHost (pre­vi­ous to the IfTA DataHub soft­ware) runs di­rect­ly on the IfTA sys­tem and it is the hub of mea­sur­ment-data han­dling. It al­lows ei­ther man­u­al­ly-con­trolled or au­to­mat­ic stor­age of data on the built-in stor­age medi­um.

In ad­di­tion to vi­bra­tion data, IfTA DataHub can also dis­trib­ute and re­ceive other data via OPC. The con­sol­i­da­tion of all data streams from dif­fer­ent sources al­lows fast and ef­fi­cient eval­u­a­tion of com­plex re­la­tion­ships, such as the ef­fect of en­vi­ron­men­tal pa­ram­e­ters or fuel com­po­si­tion on com­bus­tion in­sta­bil­i­ties. Enor­mous amounts of data re­sult from this ap­pli­ca­tion's high sam­pling rates and sheer num­ber of chan­nels, so the CEC places very spe­cif­ic de­mands on the abil­i­ties of its data anal­y­sis. In ad­di­tion to streams of raw data, col­lect­ed streams of data are gen­er­at­ed over time. This al­lows a quick over­view over long pe­ri­ods of time.

Each sen­sor is com­pat­i­ble with each input

Con­trary to power plants, far more sen­sors and sen­sor types are used in test beds. The IfTA AD4Pro mod­ule with its uni­ver­sal mea­sure­ment in­puts op­ti­mal­ly meets the re­quire­ments of a burn­er test rig and helps to save costs and re­duce com­plex­i­ty.

The IfTA AD4Pro mod­ule sup­ports the mea­sure­ment of volt­age and cur­rent sig­nals for each chan­nel. In ad­di­tion, an in­te­grat­ed dif­fer­en­tial charge am­pli­fi­er en­ables di­rect con­nec­tion of piezo­elec­tric high-tem­per­a­ture sen­sors for pres­sure and ac­cel­er­a­tion. A mea­sur­ing am­pli­fi­er for strain gauges is also in­clud­ed, to which quar­ter, half and full bridges can be di­rect­ly con­nect­ed. Sup­port for piezore­sis­tive pres­sure- and ac­cel­er­a­tion sen­sors, such as Kulite sen­sors, and an ap­pro­pri­ate power sup­ply for IEPE sen­sors are also fea­tured. The de­sired input mode is sim­ply se­lect­ed via soft­ware.

Modern data anal­y­sis through user-friend­ly soft­ware

The data anal­y­sis soft­ware IfTA TrendView­er, which can be used in the sys­tem, is a tool with which even files with 10 GB can be quick­ly load­ed and an­a­lyzed. In ad­di­tion to dy­nam­ic data and en­vi­ron­men­tal and process pa­ram­e­ters, the sys­tem also stores cal­cu­lat­ed val­ues such as peak-to-peak, RMS and en­tire spec­tra. These dif­fer­ent val­ues are eval­u­at­ed in spe­cial­ized plots such as spec­tro­gram, Nyquist plot or Bode plot. With IfTA TrendView­er sev­er­al test en­gi­neers mon­i­tor the on­line mea­sure­ment data streams dur­ing the mea­sure­ment run in in­di­vid­u­al­ly con­fig­urable views. After a test run, the record­ed data can then be fur­ther an­a­lyzed off­line and shared.

Test bench pro­tec­tion made easy

To en­sure pro­tec­tion of the test bench in the event of high vi­bra­tion am­pli­tudes, the IfTA Dy­naMaster in the CEC has been up­grad­ed with out­put mod­ules to an IfTA Ar­gusOMDS. The mod­u­lar con­cept al­lows a free choice of the de­sired out­put mod­ules. For ex­am­ple, ana­log and dig­i­tal out­puts as well as Profibus are avail­able for com­mu­ni­ca­tion with the test bench con­trol sys­tem. The sys­tem elim­i­nates many error sources of con­ven­tion­al mea­sur­ing sys­tems and thus min­i­mizes - not only in the CEC - the risk of in­cor­rect mea­sure­ments dur­ing com­plex cam­paigns. Dy­nam­ic mea­sure­ment sys­tems are the in­dis­pens­able part­ners on the way to clean en­er­gy.

com­fort­able data anal­y­sis

  • With IfTA TrendView­er, test en­gi­neers mon­i­tor live data dur­ing the mea­sure­ment and can thus react im­me­di­ate­ly
  • Up to 10 test en­gi­neers can mon­i­tor the on­line data streams si­mul­ta­ne­ous­ly
  • Com­bin­ing all data streams from dif­fer­ent sources en­ables the anal­y­sis of com­plex cor­re­la­tions
  • After test runs, IfTA TrendView­er can be used to con­tin­ue off­line anal­y­sis and col­leagues can share data and re­sults at other lo­ca­tions
  • IfTA TrendView­er of­fers a seam­less in­te­gra­tion of on­line and off­line anal­y­sis that ex­cites users

Avoid sources of error and re­duce costs

  • To avoid dis­turb­ing ground loops, each of the board's chan­nels is gal­van­i­cal­ly iso­lat­ed. This al­lows shared mea­sure­ment through sen­sors in places with high po­ten­tial dif­fer­ences, as found in large test fa­cil­i­ties such as the CEC
  • The elec­tri­cal iso­la­tion in­volved is ex­e­cut­ed in a man­ner that does not ad­verse­ly af­fect sig­nal qual­i­ty. Thus over­all, a sig­nal to noise ratio of up to 145 dB is achieved
  • The in­te­gra­tion of the am­pli­fi­er not only re­duces costs: the re­sult­ing great­ly sim­pli­fied mea­sure­ment setup also avoids sources of error
  • Changes in am­pli­fi­er set­tings are au­to­mat­i­cal­ly logged by the sys­tem and are thus re­pro­ducible at any time. This means that po­ten­tial­ly error-prone man­u­al doc­u­men­ta­tion of ex­ter­nal am­pli­fi­ca­tion fac­tors is no longer nec­es­sary
  • The an­nu­al ef­fort in­volved in cal­i­bra­tion is also re­duced con­sid­er­ably

Mea­sure­ment Chain Test­ing on Gas Tur­bines

Pro­duct: Charge Sig­nal Gen­er­a­tor

  • Ini­tial Si­t­u­a­tion
  • The Chal­lenge
  • IfTA So­lu­tion
  • Cus­tomer Value

Com­plex Mea­sure­ment Se­tups

Depend­ing on the op­er­at­ing point and am­bi­ent con­di­tions, strong pres­sure os­cil­la­tions might de­vel­op in­side gas tur­bine com­bus­tion cham­bers. This and sim­i­lar phe­nom­e­na are broad­ly re­ferred to as com­bus­tion dy­nam­ics. Their un­con­trolled oc­cur­rence may con­sid­er­ably re­duce life­time or main­te­nance in­ter­vals of the re­spec­tive ma­chine. There­fore, such op­er­at­ing con­di­tions should be iden­ti­fied and avoid­ed if pos­si­ble. This re­quires the con­tin­u­ous mon­i­tor­ing of pres­sure fluc­tu­a­tions in­side the com­bus­tion cham­bers, which is often con­duct­ed using high-tem­per­a­ture pres­sure sen­sors. These - usu­al­ly piezo-based - sen­sors gen­er­ate a charge sig­nal which, due to its sus­cep­ti­bil­i­ty to in­ter­fer­ence, must be con­vert­ed into a volt­age sig­nal for fur­ther trans­mis­sion. Due to high am­bi­ent tem­per­a­tures, the elec­tron­ics re­quired for this con­ver­sion can­not be in­te­grat­ed di­rect­ly into the sen­sor as it is com­mon for many other ap­pli­ca­tions. In­stead, ex­ter­nal charge am­pli­fiers are re­quired. This leads to a more com­plex mea­sure­ment setup and thus to an in­creased sus­cep­ti­bil­i­ty of the mea­sur­ing chains to er­rors.

In the pic­ture to the left, the tech­ni­cian stand­ing next to a sin­gle gas tur­bine com­bus­tion cham­ber il­lus­trates the di­men­sions of the ma­chine. One re­al­izes that check­ing the mea­sure­ment chains in­volves a con­sid­er­able amount of work, as one tech­ni­cian has to climb to each sen­sor while an­oth­er is sit­ting in the con­trol room. In most cases, the sit­u­a­tion is ag­gra­vat­ed by the fact that di­rect com­mu­ni­ca­tion be­tween the two is not pos­si­ble due to the dis­tances be­tween the tur­bine and the con­trol room. Often the in­spec­tion of the elec­trode must even be car­ried out by a sin­gle per­son.

Com­mon Mis­takes in the field

  • Wrong­ly wired mea­sure­ment chains are one of the most com­mon er­rors we see in the field. If such er­rors are not de­tect­ed, dam­ages due to ex­ces­sive pres­sure am­pli­tudes may be as­signed to the wrong com­bus­tion cham­ber. As a con­se­quence, in­spec­tion and main­te­nance may be car­ried out at the wrong place.
  • Po­lar­i­ty er­rors occur rather fre­quent­ly, as well. If un­de­tect­ed, they can limit prop­er mon­i­tor­ing and pro­tec­tion, for ex­am­ple, by the early warn­ing sys­tem IfTA PreCur­sor.
  • Oc­ca­sion­al­ly, sen­sor ca­bles are con­nect­ed in­cor­rect­ly to the charge am­pli­fi­er, which can lead to mains hum.
  • Due to the con­stant vi­bra­tions of the gas tur­bine, the ca­bles can chafe, come loose or be dam­aged by hot gases in case of leak­age, which can ul­ti­mate­ly lead to their fail­ure.
  • The charge am­pli­fiers can also show signs of aging over time, which may lead to a de­crease in sig­nal qual­i­ty.

In the lat­ter two cases, there is a risk that a mea­sure­ment chain goes "blind" and thus can no longer ful­fill its mon­i­tor­ing task. Rou­tine checks of all mea­sure­ment chains are hence es­sen­tial, es­pe­cial­ly after a new in­stal­la­tion, a re­place­ment or a mod­i­fi­ca­tion in the course of main­te­nance works. A por­ta­ble charge sig­nal gen­er­a­tor is an im­por­tant tool for this task. It sim­u­lates the out­put sig­nal of a sen­sor with a clear­ly de­fined fre­quen­cy and am­pli­tude and can there­fore be used to test the elec­tri­cal part of a mea­sure­ment chain.

 

 

 

IfTA Charge Sig­­nal Gen­er­at­or Helps to Elim­in­ate Er­rors

Rou­tine check­ing of the mea­sure­ment chain is in­dis­pens­able, es­pe­cial­ly after new in­stal­la­tion, re­place­ment or mod­i­fi­ca­tion in the course of gas tur­bine main­te­nance work. A por­ta­ble charge sig­nal gen­er­a­tor is an im­por­tant tool for this pur­pose. It sim­u­lates the out­put sig­nal of a sen­sor with clear­ly de­fined fre­quen­cy and am­pli­tude and can thus be used to test the elec­tri­cal mea­sure­ment chain.

It is there­fore a com­mon strat­e­gy to feed charge sig­nals of dif­fer­ent fre­quen­cies and well-de­fined am­pli­tudes to all sen­sor po­si­tions, e.g. 110 Hz to sen­sor 1, 120 Hz to sen­sor 2, and so forth. While doing this, the mea­sure­ment data is con­tin­u­ous­ly record­ed in the con­trol room. Thus, if there are er­rors in the wiring of the mea­sur­ing chains, these can be rec­og­nized and eas­i­ly as­signed to the in­di­vid­u­al sen­sors based on the fre­quen­cies in the record­ed data logs. Re­ly­ing on sig­nal path trac­ing meth­ods, faulty wiring or dam­age can then be quick­ly found and, if nec­es­sary, cor­rect­ed.

Test­ing of Meas­ure­­ment Chains Saves Costs

Up to 16 dy­nam­ic high-tem­per­a­ture pres­sure sen­sors con­tin­u­ous­ly mon­i­tor the com­bus­tion process of mod­ern heavy-duty gas tur­bines. All of them are con­nect­ed to a cen­tral mea­sure­ment sys­tem via ex­ter­nal charge am­pli­fiers. The com­plex­i­ty of such set­ups re­quires the care­ful and sys­tem­at­ic test­ing of all mea­sure­ment chains by use of a charge sig­nal gen­er­a­tor (CSG). An un­de­tect­ed faulty wiring or dam­age can lead to gas tur­bine fail­ure, which may cause high costs very quick­ly.

Test bench pro­tec­tion fa­cil­i­tat­ed

To en­sure pro­tec­tion of the test bench in the event of high vi­bra­tion am­pli­tudes, the IfTA Dy­naMaster in the CEC has been up­grad­ed with a real-time ca­pa­ble com­put­ing unit (DSP) and out­put cards to IfTA Ar­gusOMDS. The mod­u­lar con­cept al­lows a free choice of the de­sired out­put card. For ex­am­ple, ana­log and dig­i­tal out­puts as well as Profibus are avail­able for com­mu­ni­ca­tion with the test bench con­trol sys­tem. The IfTA Dy­naMaster elim­i­nates many error sources of con­ven­tion­al mea­sur­ing sys­tems and thus min­i­mizes - not only in the CEC - the risk of in­cor­rect mea­sure­ments dur­ing com­plex cam­paigns. Dy­nam­ic mea­sure­ment sys­tems are the in­dis­pens­able part­ners on the way to clean en­er­gy.

SWM Mun­ich, Early Warn­ing Sys­tem Pre­Cur­­­sor

Pro­duct: Ar­­gusOMDS + Pre­cur­­sor

  • More Ef­fi­cient Gas Tur­bines
  • Chal­lenges of this Ef­fi­cien­cy
  • Achieve­ments through IfTA So­lu­tion

Ef­fi­cien­cy in­creas­es in gas power plants in the con­text of en­er­gy tran­si­tion

The co­gen­er­a­tion plant South of SWM shows how it is pos­si­ble to meet the chal­lenges of the en­er­gy rev­o­lu­tion under the con­di­tions that no base load is re­quired: Utiliza­tion of wind and solar ra­di­a­tion in com­bi­na­tion with con­trol power from gas tur­bines. IfTA's mon­i­tor­ing and early warn­ing sys­tem en­sures the nec­es­sary eco­nom­ic ef­fi­cien­cy.


The en­er­gy tran­si­tion and the de­vel­op­ment to­wards re­new­able re­sources pose new chal­lenges for the en­er­gy mar­ket.  In con­crete terms, this means that more and more re­new­able en­er­gy is flow­ing into the elec­tric­i­ty grids with fluc­tu­a­tions due to solar ra­di­a­tion and wind. Con­trol en­er­gy is pro­vid­ed to com­pen­sate for these fluc­tu­a­tions. Since gas tur­bines can be flex­i­bly adapt­ed to the elec­tric­i­ty de­mand, they are often used to sup­ply this con­trol en­er­gy and thus sta­bi­lize the grid. At present, they are not com­pet­i­tive at the elec­tric­i­ty price in base-load op­er­a­tion com­pared with other plants such as coal power plants. In order to sup­ply this con­trol en­er­gy, the ma­chines are op­er­at­ed at par­tial load and thus react quick­ly to in­creas­ing or de­creas­ing en­er­gy re­quire­ments. A wide us­able power range as well as a low par­tial load limit are im­por­tant.

Chal­lenges of par­tial load op­er­a­tion

In a plant test at SWM's South co­gen­er­a­tion plant, the min­i­mum par­tial load of two GE Frame 9E gas tur­bines was test­ed. Using a steam tur­bine, they form a com­bined gas and steam plant with ad­di­tion­al heat feed into the 800 km long Mu­nich dis­trict heat­ing net­work. The Can-An­nu­lar ma­chines each have a rated out­put of 124 MW, with a lower par­tial load limit spec­i­fied by the man­u­fac­tur­er for pre­mixed com­bus­tion in com­pli­ance with the emis­sion limit val­ues of around 60 MW, de­pend­ing on at­mo­spher­ic con­di­tions. The aim is to be able to op­er­ate the ma­chines at low loads with­out any struc­tural mod­i­fi­ca­tions. The strat­e­gy is to close­ly mon­i­tor the phe­nom­e­na that limit the min­i­mum load. In ad­di­tion to emis­sions, com­bus­tion dy­nam­ics are a prob­lem in the op­er­at­ing area from time to time. These hard­ly pre­dictable vi­bra­tions, caused by the in­ter­ac­tion of acous­tics and heat re­lease, can reach very high am­pli­tudes, which im­pair op­er­a­tion and can even lead to dam­age.


It has been found that the acous­tics spread from can to can through trans­verse ig­ni­tion tubes around the en­tire cir­cum­fer­ence of the gas tur­bines. The con­di­tions under which they occur de­pend not only on the load, but also on at­mo­spher­ic con­di­tions, tran­sient heat­ing of the ma­chine and con­tam­i­na­tion of the burn­er el­e­ments.

Knowl­edge as a basis for ef­fec­tive op­er­a­tion

It has been found that the min­i­mum part load can be re­duced to 45 MW, in com­pli­ance with ap­pli­ca­ble emis­sion lim­its. Since the ther­moa­cous­tic cir­cum­fer­en­tial modes are con­stant­ly mon­i­tored, a change in the sta­bil­i­ty limit is de­tect­ed in time and the gas tur­bines can al­ways be op­er­at­ed under safe con­di­tions. The re­duc­tion of the min­i­mum load by around 20 % al­lows the flex­i­ble use of the ma­chines and cor­re­sponds di­rect­ly to the fuel sav­ings if no elec­tric­i­ty is re­quired, but the dis­trict heat­ing and/or con­trol power must be cov­ered. In ad­di­tion, wider power bands can be of­fered in the auc­tion process on the en­er­gy mar­ket. All in all, the power plant can thus be op­er­at­ed much more eco­nom­i­cal­ly.

MTU & UniBW M

Pro­duct: AIC

  • Re­search project MTU & UniBW M
  • Ac­tive com­pres­sor con­trol with Ifta sys­tems

IfTA re­search project with Univer­si­ty Bun­deswehr München and MTU Aero Engines

In­ter­dis­ci­plinary re­search and de­vel­op­ment at a high level was suc­cess­ful­ly car­ried out as part of a project spon­sored by the Free State of Bavaria. After three years of project work, all ini­tial­ly de­fined goals were achieved: the project part­ners ISA of uni­ver­si­ty Bun­deswehr München, MTU Aero Engines and IfTA GmbH were able to sig­nif­i­cant­ly in­crease the sta­ble op­er­at­ing range of ISA's own Larzac en­gine with the help of ac­tive com­pres­sor con­trol using the con­troller de­vel­oped by IfTA GmbH. This project was car­ried out as part of an avi­a­tion re­search pro­gram spon­sored by the Free State of Bavaria and ini­ti­at­ed by uni­ver­si­ty Bun­deswehr München.


The project in­ves­ti­gat­ed the pos­si­bil­i­ty of ac­tive­ly con­trol­ling com­pres­sor in­sta­bil­i­ties on an air­craft gas tur­bine. The aim of the re­search was to shift the pump limit of the LARZAC 04 C5 en­gine com­pres­sor avail­able at the In­sti­tute for Jet Propul­sion with the help of ac­tive mea­sures, i.e. the use of a con­troller, in such a way that the sta­ble op­er­at­ing range is in­creased and thus the ef­fi­cien­cy of the com­pres­sor is en­hanced.

IfTA as a com­pe­tent part­ner

After the first suc­cess­ful con­trol tests of other re­search in­sti­tu­tions on pure test com­pres­sors, this work rep­re­sent­ed a first ap­pli­ca­tion on a real and com­plete air­craft en­gine. IfTA GmbH sup­plied the en­tire con­troller hard­ware and soft­ware for this project and sup­port­ed the uni­ver­si­ty in sig­nal ac­qui­si­tion (mea­sure­ment tech­nol­o­gy, record­ing) and in­ter­pre­ta­tion (anal­y­sis, al­go­rithms). In ad­di­tion, fur­ther and new de­vel­op­ments of the hard­ware and soft­ware were of course car­ried out dur­ing the course of the project in order to en­able op­ti­mized con­trol.

The­mat­ic of the Cen­tral Phenomenon

The range of ap­pli­ca­tion of a com­pres­sor is lim­it­ed by the so-called com­pres­sor surge, which is ex­pressed in the phe­nom­e­non of "pump­ing" by a flow re­vers­ing across the en­tire cross-sec­tion of the com­pres­sor. As a weak­er and there­fore safer "pre­lim­i­nary stage" of this phe­nom­e­non, par­tial flow dis­tur­bances, also known as ro­tat­ing sep­a­ra­tions, cir­cu­lat­ing around the cir­cum­fer­ence of the com­pres­sor can also occur. The basic idea be­hind the ac­tive con­trol of a com­pres­sor is now to de­tect the so-called fore­run­ners of a pump­ing im­pulse or a ro­tat­ing sep­a­ra­tion in good time and to in­flu­ence the sys­tem via a con­troller and an ac­tu­a­tor in such a way that this un­de­sired op­er­a­tion of the com­pres­sor does not occur. Mo­du­lat­ed air in­jec­tion at the blade tip area of the first com­pres­sor stage has proven to be ad­van­ta­geous, as this is ex­act­ly where the in­sta­bil­i­ties are trig­gered.

Ac­tive con­trol with IfTA sys­tems

Based on a mod­i­fied form of the AIC sys­tem test­ed in the ac­tive in­sta­bil­i­ty con­trol of com­bus­tion dy­nam­ics on sta­tion­ary gas tur­bines, var­i­ous con­trol strate­gies were de­vel­oped in the course of the project which were op­ti­mized for the re­spec­tive prob­lem. With the help of these strate­gies and spe­cial­ly adapt­ed ac­tu­a­tors, the re­search project, which last­ed three years, suc­cess­ful­ly demon­strat­ed the func­tion­al­i­ty of the ac­tive com­pres­sor sta­bi­liza­tion sys­tem. Over­all, it was pos­si­ble to ac­tive­ly shift the pump­ing limit over the en­tire speed range of the com­pres­sor, thus demon­strat­ing the pos­si­bil­i­ty of in­dus­tri­al ap­pli­ca­tion of this in­no­va­tive tech­nol­o­gy. Com­pared to pure con­stant in­jec­tion, ac­tive sta­bi­liza­tion was more ef­fi­cient, i.e. the same sta­bi­liza­tion ef­fect could be achieved with less air or, with the same air con­sump­tion, the sta­ble work­ing range was ex­tend­ed be­yond the range achiev­able with con­stant in­jec­tion.

The in­no­va­tive and re­search-rel­e­vant con­tent of this col­lab­o­ra­tion is re­flect­ed in two joint pub­li­ca­tions at in­ter­na­tion­al sym­posia.

Large In­dus­tri­al Fur­naces

Ser­vice: Vi­bra­tion Di­ag­nos­tics

  • Ini­tial Si­t­u­a­tion
  • Com­bus­tion in­sta­bil­i­ties & IfTA So­lu­tion Ap­proach

Ini­tial Si­t­u­a­tion

The out­put of the large com­bus­tion burn­ers lies in the upper kW to lower MW range. They are used, for ex­am­ple, in larg­er of­fices or de­part­ment stores, in sta­di­ums or in air­ports. They no longer have their own com­bus­tion cham­ber, but are op­er­at­ed with var­i­ous boil­ers from other man­u­fac­tur­ers. This means that the burn­ers must be sta­ble in dif­fer­ent ge­ome­tries under vary­ing con­di­tions. There­fore it is im­por­tant to know ex­act­ly the ten­den­cy of the burn­ers to vi­brate in order to es­ti­mate their in­sta­bil­i­ty risk when used in dif­fer­ent ge­ome­tries.

Oc­cur­rence of com­bus­tion in­sta­bil­i­ties caused by the burn­er

In com­par­i­son to small fur­naces, i.e. con­dens­ing boil­ers, heat­ing ap­pli­ances, etc., which are in­tend­ed pri­mar­i­ly for do­mes­tic use and are of­fered as com­plete units, e.g. with burn­er, com­bus­tion cham­ber, heat ex­chang­er and ex­haust sys­tem, com­po­nents from dif­fer­ent man­u­fac­tur­ers are in­di­vid­u­al­ly com­bined in large fur­naces. The prod­ucts man­u­fac­tured by the burn­er man­u­fac­tur­er are used, for ex­am­ple, with boil­ers from an­oth­er man­u­fac­tur­er. Although com­bus­tion in­sta­bil­i­ties al­ways de­pend on the over­all sys­tem, i.e. burn­er, com­bus­tion cham­ber, ex­haust gas and in­take sys­tem, cer­tain ten­den­cies to­wards un­sta­ble be­hav­ior can be iden­ti­fied di­rect­ly at the burn­er. For ex­am­ple, com­bus­tion phe­nom­e­na based on fluid me­chan­i­cal prop­er­ties gen­er­ate cer­tain fre­quen­cy com­po­nents stronger than oth­ers. If these areas are close to an acous­tic nat­u­ral fre­quen­cy of a boil­er and other un­fa­vor­able con­di­tions are also met, cou­pling be­tween com­bus­tion and acous­tics is prob­a­ble, i.e. com­bus­tion in­sta­bil­i­ties are stim­u­lat­ed.

IfTA - a com­pe­tent part­ner

IfTA GmbH of­fers var­i­ous in­ves­ti­ga­tions into the caus­es of com­bus­tion dy­nam­ics as de­scribed above. These in­ves­ti­ga­tions in­clude mea­sure­ments di­rect­ly on the af­fect­ed plant or on our cus­tomers' test bench­es. To sup­port the ex­per­i­men­tal in­ves­ti­ga­tions of the phe­nom­e­na, a nu­mer­i­cal sim­u­la­tion of the acous­tic be­hav­ior of the boil­er ge­ome­tries is also rec­om­mend­ed. As a cus­tomer, you can rely on a com­pe­tent, fast and cost-ef­fec­tive han­dling of your prob­lems, as in the other areas. It goes with­out say­ing that we treat every issue con­fi­den­tial­ly.

Small Fur­naces in Every­day Life

Ser­vice: Vi­bra­tion Di­ag­nos­tics

  • Ini­tial Si­t­u­a­tion & Ef­fects
  • Mea­sures and con­sul­ta­tion from IfTA

Ini­tial Si­t­u­a­tion

By small fir­ing sys­tems we un­der­stand com­bus­tion sys­tems in the lower kW range, which are used e.g. as gas heaters, con­dens­ing boil­ers, oil burn­ers etc. in apart­ments, sin­gle-fam­i­ly hous­es and apart­ment build­ings. Fur­ther­more, these in­clude gas ovens or roast­ers for can­teen kitchens, gas heaters in camp­ing areas and sim­i­lar sys­tems with a de­fined com­bus­tion cham­ber ge­om­e­try in which acous­tic nat­u­ral os­cil­la­tions can es­tab­lish them­selves, as well as a flame burn­ing in them.

Ef­fects

Espe­cial­ly in the field of heaters, in ad­di­tion to low-emis­sion and ef­fi­cient op­er­a­tion, quiet com­bus­tion is of par­tic­u­lar im­por­tance, since di­rect or in­di­rect noise gen­er­a­tion by the com­bus­tion sys­tem can lead to a con­sid­er­able im­pair­ment of the qual­i­ty of liv­ing and thus also of the qual­i­ty of life. As with large sys­tems, com­bus­tion os­cil­la­tions in small com­bus­tion sys­tems can be caused by in­con­spic­u­ous en­vi­ron­men­tal changes (gas com­po­si­tion, in­stal­la­tion con­di­tions, op­er­at­ing point, am­bi­ent tem­per­a­ture, etc.). The ef­fects of these changes can be man­i­fold: low-fre­quen­cy hum­ming with fixed or vari­able fre­quen­cy when start­ing up, sud­den, short-term oc­cur­rence of in­sta­bil­i­ties, e.g. caused by clos­ing a door (and the as­so­ci­at­ed pres­sure surge), high-fre­quen­cy whistling (about 800Hz, 120dB) when op­er­at­ing at a cer­tain op­er­at­ing point, etc.

Oc­cur­rence of com­bus­tion in­sta­bil­i­ties caused by the burn­er

In com­par­i­son to small fur­naces, i.e. con­dens­ing boil­ers, heat­ing ap­pli­ances, etc., which are in­tend­ed more for do­mes­tic use and are of­fered com­plete with burn­er, com­bus­tion cham­ber, heat ex­chang­er and flue gas sys­tem, com­po­nents from dif­fer­ent man­u­fac­tur­ers are in­di­vid­u­al­ly com­bined in large fur­naces. The prod­ucts man­u­fac­tured by the burn­er man­u­fac­tur­er are used, for ex­am­ple, with boil­ers from an­oth­er man­u­fac­tur­er. Although com­bus­tion in­sta­bil­i­ties al­ways de­pend on the over­all sys­tem, i.e. burn­er, com­bus­tion cham­ber, ex­haust gas and in­take sys­tem, cer­tain ten­den­cies to­wards un­sta­ble be­hav­ior can be iden­ti­fied di­rect­ly at the burn­er. For ex­am­ple, com­bus­tion phe­nom­e­na based on fluid me­chan­i­cal prop­er­ties gen­er­ate cer­tain fre­quen­cy com­po­nents more strong­ly than oth­ers. If these areas are close to an acous­tic nat­u­ral fre­quen­cy of a boil­er and other un­fa­vor­able con­di­tions are also met, cou­pling be­tween com­bus­tion and acous­tics is prob­a­ble, i.e. com­bus­tion in­sta­bil­i­ties can be ex­cit­ed.

IfTA as a com­pe­tent part­ner

IfTA GmbH of­fers a wide range of in­ves­ti­ga­tions into the caus­es of com­bus­tion in­sta­bil­i­ties de­scribed above. These in­ves­ti­ga­tions in­clude mea­sure­ments di­rect­ly on the af­fect­ed plant or on our cus­tomers' test bench­es. To sup­port the ex­per­i­men­tal in­ves­ti­ga­tions of the phe­nom­e­non, a nu­mer­i­cal sim­u­la­tion of the acous­tic be­hav­ior of the boil­er ge­ome­tries is also rec­om­mend­ed. As a cus­tomer, you can rely on a com­pe­tent, fast and cost-ef­fec­tive han­dling of your prob­lems, as in the other areas. It is a self-ev­i­dent fact for us that we treat your prob­lem con­fi­den­tial­ly.

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