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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 CEC Clean Energy Center Berlin

Siemens - CEC
Ber­lin - SGT5-8000H

Product: Ar­gusOMDS

In­vest­ig­a­tion of com­bus­tion os­cil­la­tions in gas tur­bines under real con­di­tions.

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

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

Sie­­­mens, CEC Ber­­­lin - SGT5-8000H

Pro­­duct: Dyn­aMaster

  • Ini­tial Situ­ation
  • IfTA Solu­tion
  • Cus­tomer Value
  • In­tel­li­gent Soft­ware
  • Test Bench Pro­tec­tion

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%. The world's most power­ful Siemens ma­chine, the SGT5-8000H gas tur­bine with an elec­tric­al out­put of over 375 MW, is in op­er­a­tion there.

Test benches for op­tim­iz­ing gas tur­bines

 

Siemens 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 IfTA Solu­tion

In order to learn the most from these vari­ous meas­ure­ments, a spe­cial­ist vi­bra­tion meas­ur­ing tool is part of the ad­vanced tech­no­logy at the CEC in Lud­wigs­felde: the IfTA Dyn­aMaster. Dyn­aMaster is a fur­ther de­vel­op­ment based on the proven IfTA Argus sys­tems that have been in use in vari­ous types of gas tur­bines world­wide, like the SGT5-8000H, for over a dec­ade. Through these ap­proved in­teg­ra­tions, five spe­cific­a­tions have turned out to be es­pe­cially de­cis­ive.

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. In ad­di­tion to the fast in­puts, 32 slow voltage- or cur­rent sig­nals can be meas­ured. There are 16 in­puts avail­able for di­git­al sig­nals. 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 DataHub, which runs dir­ectly on the IfTA Dyn­aMaster, is the hub of meas­ur­ment-data hand­ling. It al­lows either manu­ally-con­trolled or auto­mat­ic stor­age of data on the built-in stor­age me­di­um, which can be either SSD or HD. In ad­di­tion to vi­bra­tion data, IfTA DataHub can also dis­trib­ute and re­ceive other data via OPC or DataSock­et.

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

The heart of this sys­tem is the IfTA AD4Pro, a four-chan­nel, dy­nam­ic meas­ure­ment mod­ule with uni­ver­sal meas­ure­ment in­puts. This 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.

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.

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 IfTA Dyn­aMaster also stores cal­cu­lated val­ues such as peak-to-peak, RMS and en­tire spec­tra in the sys­tem. These dif­fer­ent val­ues are eval­u­ated in spe­cial­ized plots such as spec­tro­gram, Nyquist plot or Bode plot. In the same soft­ware en­vir­on­ment, sev­er­al test en­gin­eers mon­it­or the on­line meas­ure­ment data streams dur­ing the meas­ure­ment run in in­di­vidu­ally con­fig­ur­able views. For this pur­pose, the IfTA TrendView­er on the work­sta­tion com­puter is com­bined with the IfTA Dyn­aMaster.

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.

Meas­ure­ment Chain Test­ing on Gas Tur­bines

Pro­­duct: Charge Sig­nal Gen­er­at­or

  • Sum­mary
  • Ini­tial Situ­ation
  • Issue
  • IfTA Solu­tion

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.

 

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.

Com­mon Mis­takes

  • 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.

 

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.

 

 

IfTA Charge Sig­n­al Gen­er­­at­or Helps to Elim­in­ate Er­rors

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.

The IfTA charge sig­nal gen­er­at­or was de­veloped es­pe­cially for this field of ap­plic­a­tion and has already proven it­self in many power plants around the world. It was spe­cific­ally de­signed for mo­bile use. Thanks to bat­tery sup­ply, dis­play back-light­ing and car­ry­ing strap, the charge sig­nal gen­er­at­or can be used in dark and dif­fi­cult to ac­cess places. It is op­er­ated via but­tons at­tached to its upper side. A 2.7-inch dis­play al­lows to eas­ily se­lect fre­quency, amp­litude and sig­nal form.

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.

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