Sutkowski Wartsila Ss 3 2011

8/17/2019 Sutkowski Wartsila Ss 3 2011

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Marek SUTKOWSKI PTNSS–2011-SC-046

Wärtsilä 18V50SG – the world’s biggest four-stroke spark-ignitedgas engine

Abstract:

In 2010 Wärtsilä introduced brand new four-stroke spark-ignited lean-burn gas engine to its portfolio. Thenew engine generates close to 19MW of power with efficiency about 46%. The product follows market needs andexpectations for decentralised power generation combined with reliable and flexible operation.

In this paper technical specification of the Wärtsilä 180V50SG will be presented. The description will includedevelopment background as well as the engine operation performance, emission levels and fuel requirements.The main components of the engine and applied technology will be also described.

Finally, some typical applications of the Wärtsilä 18V50SG will be shown including the newest power plantconcept for high-efficency decentralised power generation. The most significant operational features of theengine will be also covered in this paper.

Key words: four-stroke spark-ignited lean-burn gas engine

Wärtsilä 18V50SG – najwi ększy na świecie czterosuwowy silnik gazowy o zapłonieiskrowym

Streszczenie:

W 2010 roku Wärtsilä wprowadziła do oferty nowy czterosuwowy silnik gazowy o zapłonie iskrowymspalaj ący mieszanki ubogie. Nowy silnik ma moc nominalna prawie 19MW i charakteryzuje si ę sprawno ścią 46%. Ten nowy produkt jest odpowiedzi ą na zapotrzebowanie rynku silników gazowych oraz rosn ącychoczekiwa ń bran ż y zdecentralizowanej energetyki charakteryzuj ą cej si ę wysoka pewno ścią działania orazelastyczno ścią pracy obiektów.

Artykuł zaprezentuje dane techniczne silnika Wärtsilä 18V50SG. Opis b ędzie równie ż zawierał tło całego procesu rozwoju nowego silnika oraz parametry operacyjne silnika takie jak osi ągi, emisje oraz wymogiodno śnie paliwa gazowego, którym silnik mo ż e by ć zasilany. Dodatkowo najwa ż niejsze komponenty silnika oraz

zastosowana technologia zostan ą uwzgl ędnione w artykule.

Ponadto artykuł przedstawi tez typowe zastosowania silnika Wärtsilä 18V50SG obejmuj ą c równie ż najnowsza elektrownie koncepcyjna dla zdecentralizowanej wysokosprawnej energetyki. Ta cz ęść obejmujerównie ż główne aspekty pracy tego silnika.

Słowa kluczowe: czterosuwowy silnik gazowy o zapłonie iskrowym zasilany mieszanka uboga

1. Introduction The history of Wärtsilä gas engines starts in

1987 when the first gas-diesel engine was intro-duced. This technology was mainly dedicated tooffshore applications, although it also could be usedfor power generation.

In 1992 the development of the lean-burn spark-ignited gas engine has started and the first spark-ignited gas engine was released in [5, 6]. The en-gine offered very good performance and cleancombustion (lean gas mixture) with self-learningand self-adjustable functions in control system.

At the end of 20th century, the high-efficiencylean-burn Wärtsilä 34SG engine family based on

the new Wärtsilä 32 diesel engine frame was intro-duced. This new engine family has replaced the old

one and is dedicated to very efficient Wärtsilä gaspower plants.

New trends in power generation require com-bined high-efficiency, high-flexibility and high-reliability technology. Decentralised power genera-tion stations are getting bigger and they have tohave several functions in energy system: grid stabil-ity, peak power generation, base-load operation etc.This creates many challenges and out-dated tech-nology needs to be replaced. The Wärtsilä18V50SG, the world’s biggest four-stroke spark-ignited gas engine is a response for these require-ments. The engine introduced in 2010 providespower around 19 MW combined with high-efficiency and flexibility. A huge experience gained

by Wärtsilä over many years of gas engines devel-


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opment results in high reliability and operationavailability.

2. Engine technology & design

The Wärtsilä 18V50SG engine benefits from

well-proven Wärtsilä lean-burn spark-ignited gasengine concept as well as from the Wärtsilä18V50DF dual-fuel engine technology. The Wärt-silä 18V50SG engine is built on the same framelike the Wärtsilä 50DF and the Wärtsilä 18V46diesel engine.

The Wärtsilä 18V50SG is turbo-charged four-stroke medium-speed engine with ported gas injec-tion and a spark ignition system with a pre-chamber. The engine stroke is 580 mm (the samelike in the Wärtsilä 18V46) and bore is 500 mm(increased from 460 mm like in Wärtsilä18V50DF). The main engine data are presented in

the Table 1.

Table 1. The Wärtsilä 18V50SG engine data [9]Cylinder configuration 18VCylinder bore / stroke 500 / 580 mmSpeed 500 or 514 rpmMean piston speed 9.7 or 9.9 m/sCompression ratio 11:1V-angle 45°Engine length 12 460 mmEngine width 4 420 mmEngine height 5 160 mmEngine weight 217 000 kg

A nodular cast has been chosen for the engineblock due to its strength and stiffness. Advancedfoundry technology results in a pipe-free engineblock with integrated oil and water channels. Theengine block has large crankcase covers for easymaintenance access. The crankshaft design providesvery good bearing conditions and very high stiff-ness, since the cylinder spacing is only 1100 mm.Each cylinder liner is equipped with two sensors forcontinuous temperature monitoring. Typically forWärtsilä engines, pistons are made of the low-

friction composite type with aluminium skirt andforged steel top.The Wärtsilä 18V50SG engine has been de-

signed for optimal cooling and heat recovery. Theopen-interface cooling system has four circuits:cylinder cooling (jacket), charge-air high-temperature cooling, charge-air low-temperaturecooling and lube-oil cooling. The lubricating oilsystem includes a wet oil sump, an engine-drivenmain pump as well as an electrically driven pre-lubricating pump, cooler and filters. The pre-lubricating system is used before engine starting; ithelps to reduce wear of engine components.

A specially designed pre-chamber combines lowNO x emission, extended spark plug life, rapid igni-

tion and stable combustion with high combustionefficiency. Its shape was developed from smallerspark-ignited gas engine i.e. Wärtsilä 20V34SG,optimized with 3-dimentional CFD simulations andthen verified during many hours of engine test runs.The ignition module is integrated into the Wärtsilä

Engine Control System (WECS), which sets theglobal ignition timing. The module itself sets indi-vidual ignition timing for each cylinder to providethe most efficient combustion and to avoid knock.The spark plug was developed together with sparkplug suppliers to withstand high cylinder pressuresand temperatures which negatively affect typicalspark plug lifetime.

In the Wärtsilä 18V50SG, engine ported-gas-admission technology is used which is identical tothe one from Wärtsilä 18V50DF and eliminates therisk of backfire in the air intake manifold, gives agood load response and enables a different delivery

of gas fuel to each cylinder. The main gas admis-sion valves are located right upstream of the inletvalves. Each cylinder is controlled separately byWECS, which is continuously monitoring parame-ters like engine load and speed, exhaust tempera-tures and pressure inside each cylinder. The pre-chamber receives gas via mechanically-driven hy-draulically- controlled valve. This solution hasproven to be very reliable and provides excellentignition properties of pre-chamber mixture.

All Wärtsilä 18V34SG engines are equippedwith two turbo-chargers, which were chosen fortheir minimum flow losses and very good effi-ciency. A charge air pressure reaches 450 kPa atfull load operation. The engine has a pneumaticstarting system with starting valves in the cylinderheads on one bank only. Valves are operated by anair distributor while starting limiter valves switchoff the starting system as soon as the engine runs.

The Table 2 presents typical life time for mainthe Wärtsilä 18V50SG engine components. Thecomponents life time is based only on total operat-ing hours and the engine starts, stops or loadinghistory have no influence on maintenance schedule.

Table 2. The Wärtsilä 18V50SG main componentslife time [9]

Engine component Typical life time(operating hours)Piston 72 000Piston rings 18 000Cylinder liner 96 000Cylinder head 72 000Inlet valve and valve seat 36 000Exhaust valve and valve seat 36 000Crankshaft bearings 36 000Camshaft bearing 72 000Main gas admission valve 24 000

Pre-chamber valve 18 000Pre-chamber 36 000


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Ignition coil on plug 18 000

3. Engine operation & performance

In lean-burn engines, the peak temperature is

kept low which results in a low NO x emission,reduces the knock tendency and enables a highthermal efficiency. Unfortunately, too lean mixturecan lead to misfiring and high emission of unburnedhydrocarbons. The WECS is designed to controlevery cylinder separately and to keep each cylinderin its optimal operating window (Fig.1).

The system is based on cylinder pressure meas-urements supported by exhaust gas temperaturemeasurements, engine speed measurements andturbocharger speed measurements. The engine canoperate at 500 rpm or 514 rpm and the brake meaneffective pressure is equal to 2.2 MPa, which pro-vides 1045 kW (at 500 rpm) or 1070 kW (at 514rpm) of power per cylinder with a maximum firingpressure of 17.8 MPa. The engine has 90% me-chanical efficiency and over 47% overall effi-ciency.

The engine is usually integrated with an electri-cal generator on a common frame base with elec-

tricity generating efficiency of the set 46%, whichresults in 18320 kW of electrical power at 500 rpm[8, 9]. The gas fuel requirements for continuousengine operation at full load are presented in theTable 3 and the engine performance data are pre-sented in the Table 4.

The Wärtsilä 18V50SG engine is design accord-ing to the newest requirements regarding flexiblepower generation. The engine is able to reach fullload within 10 minutes from start signal. The en-gine efficiency doesn’t change much over verywide load range (from 50% to 100% load), which isvery beneficial when part load operation is required

for a longer time. In emergency situation the enginecan start-up and load-up even quicker. The start-up

and loading procedures are shown in the Figures 2and 3.

Table 3. The Wärtsilä 18V50SG gas fuel re-quirements for continuous full load operation [9]Lower heating value Min. 28 MJ/m³

Methane number Min. 70Methane contents, CH 4 Min. 70%Hydrogen sulphide, H 2S Max. 0.05%Hydrogen, H 2 Max. 3%Condensates Not AllowedAmmonia Max. 25 mg/m³Chlorine + Fluorine Max. 50 mg/m³Particles or solids(content and size) Max.

50 mg/m³5 m

Gas inlet temperature Range 0 – 60 °C

Table 4. The Wärtsilä 18V50SG performancedata at full load [9]Mean effective pressure 2.20 MPaMaximum firing pressure 17.8 MPa

Power per cylinder 1045 kW (500 rpm)1070 kW (514 rpm)Engine mechanical effi-ciency 90%

Engine overall efficiency 47.4%Electricity generating setefficiency 46.2%

NO x emission 1.2 g/kWhCO emission 1.06 g/kWhHC emission 3.2 g/kWh

Typical CO2 414 g/kWhParticulates emission 0,064 g/kWhFormaldehyde 0,27 g/kWhTotal sound power level 129 dBA

Fig. 2. The Wärtsilä 18V50SG start-up procedure (514rpm nominal speed) [9]

The successive loading can be combined withload steps, if the engine is operating in island mode(speed control). The minimum continuous load is30%. The maximum permissible load step whichmay be applied at any given load is presented in the

Figure 4. Furthermore the stated values are limitedto a running engine that has reached nominal oper-

Fig.1. The Wärtsilä 18V50SG cylinder optimal

operating window [8]


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ating temperatures, or for an engine which has beenoperated at above 30% load within the last 30 min-utes.

Fig. 3. The Wärtsilä 18V50SG loading and unloadingcurves [9]

Fig. 4. The Wärtsilä 18V50SG instant loading steps [9]

4. Typical applications

All Wärtsilä gas engines can be used as a powersource in pumping stations for pipelines and thedual-fuel engines can be also used for marine pur-poses. The Wärtsilä spark-ignited gas engines anddual-fuel ones are mainly dedicated for power gen-eration applications. Wärtsilä gas power plants canoperate in parallel to the grid or in island mode.They can be controlled at site or remotely and canbe connected to condition based maintenance centrewhere Wärtsilä service personnel has access to

plant operation system, as well as engine operationsystem and they even check signals from particularsensors mounted on the engine.

The Wärtsilä has delivered already more than700 spark-ignited engines to more than 200 gaspower plants and their total power is more than5000 MW. Also the Wärtsilä 46 and the Wärtsilä50DF that share frame and components design withWärtsilä 50SG have impressive reference record:more than 700 engines and more than 10 GW oftheir total power.

The Wärtsilä 18V50SG engine is meant to re-place the Wärtsilä 20V34SG in new gas power

plants projects with plant output over 150 MW. Theengine can operate on pipeline quality natural gas

as well as on liquefied natural gas (LNG). TypicalWärtsilä gas power plants are used as power sourcefor industry (mining, cement, petroleum etc.), forlocal utilities (airports, hotels etc.) or as part of anelectrical grid system.

The engine can be core part of combined cycle

gas power plant. This solution requires exhaust gassteam boilers and a steam turbine. By implementingthis power generation capacity of plant can be in-creased by 8% to 10% and electricity generationefficiency can reach totally over 50% .

The Plains End power plant is excellent exam-ple of the Wärtsilä spark-ignited engine applicationas important part of an electricity generation system(Fig. 5). The plant is located in Denver in USA.The first phase (Plains End I) was delivered in 2002and has twenty Wärtsilä 18V34SG engines generat-ing together 111 MW with 41% of electricity gen-eration efficiency. Originally plant was meant to be

peaking power plant started once per day only forcovering peak power demand. Soon after plantoperation started client (PG&E National EnergyGroup) discovered great potential for flexible gasfired power plants and has changed operation pro-file by providing grid stability service as support forgrowing wind power plants capacity in that region.The client also ordered the extension of existingpower plant (Plains End II) with fourteen Wärtsilä20V34SG engines providing additional 118 MWwith 44% of electricity generating efficiency. ThePlains End gas power plant can generate up to 230MW and full power of the plant can be reached inless than 5min. The plant is started and ramped-upwhen wind generated electricity decreases as aresult of wind behaviour. This kind of operationrequires over 1000 starts and stops per year onaverage. The short start-up time or frequent startshas no influence on the maintenance schedule.

Fig. 5. Examples of Wärtsilä power plants as typicalapplications of the Wärtsilä 18V50SG. Top: 230 MW

flexible grid stability gas power plant Plains End I & II (Denver, USA); bottom: 308 MW base load gas power plant Sangachal (Azerbaijan) [1]


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Another potential application example for theWärtsilä 18V50SG comes from the Caspian Seaarea. The largest so far Wärtsilä gas power plant islocated in Azerbaijan. The plant is based on eight-een Wärtsilä 18V50DF gas engines and is locatednear the biggest oil terminal in that region. This 308

MW gas power plant started operation at the end of2008 and is a very important component of thecountry power generation system.

5. Summary

The Wärtsilä 18V50SG gas engine is the newestWärtsilä lean-burn gas engine dedicated to the mostefficient large Wärtsilä gas power plants. The en-gine is the world’s biggest 4-stroke spark-ignitedgas engine and its design is based on advancedtechnology and sophisticated solutions providingexcellent performance, reliable operation, easy

maintenance and long life of engine components.The Wärtsilä 18V50SG is a very efficient(47.4% overall efficiency) and powerful (over 19

MW) engine suitable for flexible power generation.The engine can operate on pipeline quality naturalgas or on liquefied natural gas (LNG).

The engine maintenance schedule is based onoperating hours and is independent from the num-ber of start and stops. The multi-unit design enables

high part-load plant efficiency, excellent plantavailability and reduced need for back-up capacity.A start-up procedure and engine loading-up to fullload takes all together only 10 minutes.

Wärtsilä gas power plants with Wärtsilä18V50SG engines offer also combined cycle solu-tion which increases plant efficiency to the level of50%. It provides also stepwise investment withsmaller risk and optimized profit generation. Wärt-silä gas power plants provide full integration andexcellent flexibility and high performance in allambient conditions, which is a valuable characteris-tic for modern decentralized power generation.

Nomenclature / Skróty i oznaczenia

WECS Wärtsilä Engine Control System / silnikowysystem automatyki i sterowania wärtsilä

WOIS Wärtsilä Operators Interface System / inter- fejs systemu operacyjnego Wärtsilä

Bibliography / Literatura

[1] “Gas power plants”, Wärtsilä Corporationbrochure

[2] Klimstra J.: The road to obtaining the ultimateperformance of gas engines – opportunitiesand challenges, 5 th Dessau Gas Engine Con-ference proceedings, 2007

[3] Kuurio H.: Wärtsilä large gas power plants – amodular approach offering a wide range ofcapabilities, Twentyfour7 Wärtsilä QuarterlyMagazine 03.2006, pp. 44-45, 2006

[4] Sutkowski M.: The combustion systems in thehigh-power stationary internal combustionengines, XX International Symposium onCombustion Process proceedings, 2007

[5] Sutkowski M., Latvasalo T.: The 20V34SG –a high-efficiency lean-burn gas engine for

highly efficient Wärtsilä gas power plantscombustion systems in the high-power sta-tionary internal combustion engines, Combus-tion Engines PTNSS-2007-SC1, pp. 27-38,2007, PL ISSN 0138-0346

[6] “Wärtsilä 34SG engine technology”, WärtsiläCorporation brochure

[7] “Wärtsilä 50DF engine technology”, WärtsiläCorporation brochure

[8] “Wärtsilä 50SG engine technology”, WärtsiläCorporation brochure

[9] “Wärtsilä 50SG performance manual”, Wärt-silä report

Mr Marek Sutkowski, PhD, MSc, Eng. – SeniorDevelopment Manager in Gas Plants at WärtsiläFinland.

Dr in ż . Marek Sutkowski – starszy kierownikds. rozwoju w dziale elektrowni gazowych,Wärtsilä Finland.

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Sutkowski Wartsila Ss 3 2011