engine selection for very large container vessels

Winterthur Gas & Diesel Ltd.

Engine selection for very largecontainer vessels

Engine selection for very large container vessels – WinGD September 2016 1

Contents

1 Introduction – 8’000 to 22’000 TEU container vessels ..................................................................... 2

2 Boundary conditions for the engine selection ..................................................................................... 3

2.1 Energy Efficiency Design Index – EEDI ....................................................................................... 3

2.2 The global economy, worldwide container transport capacity and fuel prices ....................... 3

2.3 Fuels and related regulations ...................................................................................................... 4

2.4 NOX Emission limits ...................................................................................................................... 4

2.5 Flexible propulsion setup ............................................................................................................. 4

3 Engine power and speed selection ....................................................................................................... 6

3.1 Vessel speed and operational economy – slow steaming ........................................................ 6

3.2 Define engine rating ...................................................................................................................... 6

3.3 Propeller selection ........................................................................................................................ 7

4 Engine selection ...................................................................................................................................... 8

4.1 Engine types and their characteristics ........................................................................................ 8

4.1.1 Available engines for operating on diesel and LNG ............................................................... 8

4.1.2 Common characteristics of the X82 and X92 diesel and gas engines ................................ 9

4.1.3 Low pressure X-DF engines .................................................................................................. 11

4.2 Engine tuning .............................................................................................................................. 11

4.3 Waste heat recovery .................................................................................................................. 12

4.4 NOx and SOx emission reduction technologies ...................................................................... 12

4.4.1 DF ready ................................................................................................................................. 12

4.4.2 SCR solutions ......................................................................................................................... 13

4.5 Flexible operation adaptation ................................................................................................... 14

4.5.1 Dual tuning ............................................................................................................................. 14

4.5.2 Dual rating .............................................................................................................................. 14

4.5.3 Changing from diesel to LNG ................................................................................................ 14

5 Newbuilding cases ............................................................................................................................... 15

5.1 X82 and X92 for 14’000 TEU vessels ..................................................................................... 15

5.2 12X92 and 12X92DF for DF ready 20’000 TEU vessels ...................................................... 16

6 Conclusions .......................................................................................................................................... 18


1 Introduction – 8’000 to 22’000TEU container vessels

The trend towards increased vessel capacityfor the transportation of containers iscontinuing to meet the steadily increasingdemand in goods transportation between thefive continents.

The first vessels able to transport containerswith a volume of more than 8’000 TEU(Twenty-foot equivalent unit) were built in1997. In 2013, the first vessel with a capacityabove 18’000 TEU was delivered and wentinto operation. The first vessel with more than21’000 TEU is expected to come into servicein 2017.

Initially, the installed main engine powerfollowed the trend with increased output. Butaround 2010 this declined as a result of theconsistent application of slow steaming. Thefirst 8’500 TEU vessels driven by 12RT-flex96C engines went into operation with61’900 kW power. Main engines with a powerrating above 80’000 kW were installed in14’000 TEU vessels delivered from 2006onwards (engine type 14RT-flex96C).

But the newest vessels, with a capacity ofmore than 18’000 TEU, are being ordered witha comparatively low main engine power outputof close to 60’000 kW (engine type Wärtsilä11X92). Similarly, some new 14’000 TEUvessels have been ordered with power ratingsof less than 40’000 kW (8X92 or 9X82).

The lower power demand of these containervessel orders can be explained by the

increased focus on reduced fuel consumption:Shipyards have improved hull designs andhydrodynamic propulsion efficiency, therebyreducing power demand at the same vesselspeed by ~10%, and combining this with de-rated engines having better fuel efficiency.

On the operational side, vessel owners andoperators have reduced vessel target designspeeds considerably, thus allowing largersteps in reducing main engine powerrequirements.

WinGD’s low-speed engines are following themarket trends. Today, the built-in flexibility oftheir engine specifications allows shipyardsand ship owners to adapt performance tospecifically meet the intended operationalrequirements.

This paper is intended to assist in the selectionof the best WinGD low-speed engine for new,competitive, and future proof very largecontainer vessels.

Figure 1: Very large container vessel deliveries over20 years (Source: Clarksons Research June 2015)with starting dates for high number deliveries ofvessels in the range of 80’00TEU, 14'000TEU and18'000TEU.


2 Boundary conditions for theengine selection

2.1 Energy Efficiency Design Index– EEDI

In 2012 the IMO (International MaritimeOrganisation), the regulatory body forinternational seagoing vessels, introduced theEnergy Efficiency Design Index (EEDI) to helpdrive efforts aimed at reducing greenhousegas emissions, specifically CO2, from seagoingvessels. The vessel specific EEDI is calculatedas being the CO2 emitted by a vessel for everytransported cargo in dwt per nautical mile.

The reference EEDI depends on the date of thecontract, and is defined in regulation 21 of theMarpol Annex VI (also described in the IMOresolutions MEPC 203(62), see www.imo.org).A guideline for evaluating a vessel’s EEDI valueis given in resolution MEPC 245(66). To ensurecontinuous improvement and innovationwithin the shipping and shipbuilding industries,the target levels are reduced in stages.

The target EEDI for container vessels builtbetween 1. January 2013 and 31. December2014 is calculated by the formula:

174.22 * DWT^(-0.201) in g/dwt/nm

The curve reflects the possibility for reducingCO2 emissions per TEU by applying largervessels.

From 1. January 2015 the target EEDI isreduced by 10%, from 1. January 2020 by atotal 20%, and from 1. January 2025 by a totalof 30%.

A 14’000 TEU vessel with a DWT of around160’000 built after 2015 needs to meet thelimit of 14.1 g/dwt/nautical mile.

To achieve a low EEDI, the following mainmeasures can be considered:

1. Reduce the installed engine power(either by increasing the hull andpropulsion efficiency, or by reducingthe maximum vessel design speed)

2. Select engines with lower fuelconsumption

3. Install additional energy savingtechnologies, such as waste heatrecovery

4. Burn gas instead of HFO because ithas less CO2 emissions for the energyequivalent volume burnt.

2.2 The global economy, worldwidecontainer transport capacityand fuel prices

The target vessel speed is a key factor indefining the required main engine power. Theoptimum vessel speed is strongly influencedby the actual economic environment and thestate of the container shipping market.

For example, in the case of a low ratio ofmarket transportation demand against theavailable container vessel transportationcapacity, reducing the vessel speed can beconsidered as a way to reduce operating costsand ensure well loaded vessels. Conversely,high market demand may justify a highervessel speed.

At very low fuel prices (per ton), theimportance of fuel to operating costs isreduced and an increase in vessel speed maybe considered for maximizing the vessel’soperating result. When targeting for a specificnumber of containers to be transported pervoyage, one consequence would be to alsoreduce the number of vessels required to coverthe specific roundtrip.

By defining a scenario for the coming years inview of expected market developments, theoverall available shipping capacity, as well asfuel market trends, the right choice ofpropulsion system becomes easier to make.Figure 2: The EEDI target levels introduced by the

IMO for very large container vessels


2.3 Fuels and related regulations

Regulations, issued either by the IMO or bylocal authorities, that limit the maximumallowed sulphur content in the fuel used canhave a significant impact on today’s vesseloperational costs. The worldwide sulphur caplimit of 3.5% introduced in 2012 is planned tobe lowered to 0.5%. This limit will be applied inEU waters from 2020. The IMO will decide in2018 on the worldwide sulphur capimplementation in 2020 or 2025.

The different sulphur levels as such have onlya small impact on the choice of engine, astoday’s WinGD designed marine two-strokediesel engines can burn any kind of diesel fuelwithout restrictions (considering the adaptedfuel treatment and cylinder lubrication).

However, the sulphur limitations may influencethe choice of either running on low sulphurfuels, or continue with high sulphur HFO fuelsand apply exhaust gas scrubbers to removethe sulphur oxide (SOX) emissions from theexhaust gas flow.

Another option is the application of LNG as themain fuel, thus cutting sulphur emissions tothe lowest level and also reducing CO2

emissions by 25% to 30%. For WinGD X-DFengines, a low-pressure dual-fuel enginetechnology breakthrough has been realized. Byapplying the low pressure gas concept, theinvestment in an expensive high pressure gassystem is avoided, and no NOX reductionsystem is needed for operating in NOX

emission control areas – see chapters 4.1.3and 5.2 for more details.

2.4 NOX Emission limits

The first globally applied NOX emission limitswere implemented by the IMO in 2000 (Tier I),and were followed by a further reduction in2011 (Tier II). The Tier III regulations representan even bigger step, even though the loweremission limits are only valid in designatedECA areas (Figure 4).

To meet the low Tier III NOx emission limits,diesel engines necessitate an investment inNOX reducing technologies. For WinGD’s low-speed engines, SCR technology is offered withtwo solutions:

a) The high pressure SCR (HP SCR)installed between the exhaust receiverand the turbocharger takes the leastamount of space but requires beingplaced in the engine room

b) The low pressure SCR (LP SCR)solution allows installation of the SCRreactor after the turbocharger outsideof the engine room or in the stack.

Choosing the right solution needs to be basedon the ship’s design and the operator’srequirements. See chapter 4.4 for moredetails.

2.5 Flexible propulsion setup

Compared to the situation before 2008, theboundary conditions for ships and theiroperators are now changing more frequentlythroughout the life of the vessel. The changingdemand and supply situation, varying fuelprices, the possibility to utilise different fuels,and new emission regulations give anadvantage to flexible vessel and propulsiondesigns able to be reconfigured for optimumperformance according to any and allconditions.

–97% –86%–71%–78%–67%

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Figure 3: Present and future IMO sulphur emissionregulations.

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81012141618 17.0 Tier I

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Figure 4: Valid IMO NOx emission limits dependingon vessel keel laying date


Year 2017 2020 2025Item \ Description Vessel travels only

between Europe andAsia with slowsteaming

0.5% fuel sulphur capintroduced worldwide.Continue operatingwith high sulphur HFOand install sulphurscrubber.Good marketcondition allowshigher vessel speed

LNG becomes muchcheaper than HFO.Convert propulsionsystem fully forcontinuous LNGoperation.Extension ofoperations to UScoast.

Engine X92 derated X92 with higher rating Conversion to X92DFFuel HFO & engine and

vessel installationready for LNG

no change LNG

NOx emission level Tier II no change Tier III – enginealready compliant withX-DF technology

Sulphur strategy HFOLSFO in ECA area

Installation ofscrubber

LNG operation.Removal of scrubber

Propeller Propeller optimizedfor low speed

Change propeller forhigh speed operation

-

Table 1: Example of possible operational scenarios for owners to decide on the appropriate propulsion andengine technology

This flexibility can be addressed in threedifferent ways, which correspond to thedifferent compromise concepts between easeof flexibility and the related costs to achieve it:- Apply a design, which can be easily

changed to operate efficiently at any newboundary condition. For example, bypreparing the engine for optimum slow orfast operation with dual tuning or dualrating of the main engine

- Make small investments in the initialdesign to prepare the vessel for laterconversion and upgrades, with less costand less time out of operation. Forexample, prepare the vessel forinstallation of a NOx reducing technology,LNG supply, or the installation of anexhaust scrubber.

- Make no preparations during thenewbuilding stage, and decide oninstallation modifications when a majorchange in boundary conditions occurs.


3 Engine power and speedselection

3.1 Vessel speed and operationaleconomy – slow steaming

Slow changes in vessel speed (v) are correlatedwith high changes in engine power (PE). Thecorrelation is shown as:

PE = const * vβ

The factor β depends on the actual propellerand hull design. For very large containervessels designed for a speed of 21 knots, β isabout 3.4 leading to the following correlation:

The above curve is similar to the theoreticalideal propeller law correlating engine speed(now vessel speed) and power, applying afactor 3.

Deciding on a newbuilding series of containervessels to cover a transportation route withseveral vessels, fuel costs represent only oneaspect to be considered. The total cost ofownership might look as follows, including theinvestment (capital) costs, operating costs(manning, maintenance, insurance, etc.) andvoyage costs including fuel and travelling fees:

The achievable total cost of ownership savingsthrough increasing the size of the fleet willdepend on the actual fuel prices and interestrates, as well as the realized vessel purchasingprice.

3.2 Define engine rating

The starting point for any engine selection isthe power and propeller speed required toachieve the target vessel speed. The referencevalue set for ideal ambient conditions, andwith the vessel’s hull in new condition, requirethe addition of margins for safe operation ofthe engine in real life. The additional marginsare:

LRM – Light running margin to reflect thechanged propeller curve (power versus vesseland propeller speed) due to fouling of the hulland propeller and heavy weather conditions

SM – Sea margin to reflect the increasedpower demand with fouling and heavyweather conditions

EM – Engine margin as mechanical andthermodynamic power reserve for operatingwith the best fuel consumption

Figure 7: Light running margin (LR), Sea margin (SM)and Engine margin (EM) (%-values are examples)

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Figure 5: Power and vessel speed correlation for avery large container vessel

Figure 6: Qualitative figures for total cost ofownership per year with different numbers ofcontainer vessels (8 to 14) and adjusted vesseldesign speeds for the same total transportationvolume per year


For the light running margin, a value ofbetween 4% and 7% is recommended. Typicalvalues for the sea and engine margins are 15%and 10% respectively.

3.3 Propeller selection

The choice of propeller design influences thepropulsion efficiency considerably.

As a basic law, the lower the propeller rotationspeed, the larger can be the diameter of theselected propeller (the maximum propellerrotation speed being limited by the maximumallowable tip speed). And the bigger thepropeller, the greater is the achievablemaximum propeller efficiency.

The propeller diameters used on very largecontainer vessels are between 9 and 11metres. The maximum attainable open waterpropeller efficiency ηO achievable with aspecified propeller diameter at propeller speedn is described by the factor α, usually beingabout 0.2 for large container vessels:

ηO = const *nα

The value of const depends on the selectedhull and propeller technology. The improvedopen water efficiency of the propeller with anincreased diameter has to be balanced againstthe higher investment costs for the propellerand shaft, and the limitation in space under thehull given by the draft limitations of the vessel.At the upper limit of the allowable diameter,losses in hull efficiency also need to beconsidered.

In addition to the diameter, the number ofblades can also be increased or reduced so asto move the efficiency peak to lower or higherpropeller speed ranges while keeping the samediameter. This avoids changing the hull designand ensures keeping the propeller fully inwater – a propeller with the highest number ofblades achieves the best efficiency at lowerrotation speeds. As a rule of thumb, one bladedifference moves the efficiency peak by about10% of the rotation speed.

Figure 8: Example of achievable propellerefficiencies at given vessel design and propellerspeeds, with varying propeller diameters andnumber of blades


4 Engine selection

4.1 Engine types and theircharacteristics

4.1.1 Available engines for operatingon diesel and LNG

The WinGD X-engine series succeeds the RT-flex engine series introduced from 1999onwards. It has been designed to meet thelatest emission regulations with the lowestfuel consumption and increased maintenancefriendliness.

To meet the target power range of betweenabout 35000kW and 70’000kW, two enginetypes can be considered:

The X82 engine with 6 to 9 cylinders or theX92 available with 6 to 12 cylinders (see Table2).

Both the X82 and X92 engines are availablefor operating on HFO and MDO/MGO, and alsocome in X82DF and X92DF versions foroperation with LNG or diesel fuel.

The power and speed range covered by thetwo engines is shown in Figure 9.

Basic engine parameters Unit WX82-B WX92Bore mm 820 920Stroke mm 3375 3468Stroke / bore - 4.11 3.77Number of cylinders - 6 - 9 6 – 12

Speed range rpm 58 - 84 70 - 80Max mean piston speed m/s 9.45 9.25Max mean effective pressure bar 21 21

Fuel consumption (R1, standard tuning) g/kWh 165 166Power / cyl kW 2765 - 4750 4070 - 6450

Table 2: The main characteristics of the X82 & X92 engines

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Figure 9: Power and speed range covered by theX82 (6- to 9-cylinder), X92 (6- to 12-cylinder) andtheir related gas engine versions, the X82DF andX92DF.


4.1.2 Common characteristics of theX82 and X92 diesel and gasengines

Basic layout:

The design of the new X-engines is a result ofthe continuous research and developmentefforts by WinGD on marine low-speed enginesaimed at enhancing reliability, engineperformance, and easy maintainability.

Common proven technology platforms formthe basis for the full X-engine portfolio withindividual adaptations of the engine to meetdifferent engine size and power requirements.

Flex common-rail system

Since its introduction in 1999, the unique Flexcommon-rail system has been continuouslyimproved to increase component reliability andlifetime and to reduce the maintenance costs.

The X82 and X92 engine series incorporatethis well proven technology with furtherimprovements.

The Flex common-rail technology allowsindividual control of the fuel injectors in eachcylinder, thereby optimising the operatinginjectors’ atomization characteristics accordingto the available air and fuel demanded.

Flex common-rail technology provides greatflexibility in the engine setting for lower fuelconsumption, lower minimum running speeds,smokeless operation at all running speeds, and

better control of the exhaust emissions. Theintegrated redundancy maintains the highreliability of the engines.

In combination with the optimised thermo-dynamic process and the adaptive engineparameter setting concept, the common-railsystem provides superior engine performance.The ability to regulate the engine’s operationalperformance results in good manoeuvringcapabilities and allows the lowest possibleoperating speeds, for example, during canaltransit and port entrance.

The X-engines’ Flex common-rail technologyplays a key role in enabling ship owners tomeet the challenge of higher fuel costs.

Advanced cylinder lubrication concept

The trends related to slow steaming vesseloperations and towards high stroke to boreratios, require improved cylinder lubricationsystems to cope with the more challengingconditions in the combustion chamber.

The X82 and X92 engines apply the electroniccontrolled Pulse Lubricating Systems (PLS)introduced in 2006 to replace the mechanicallycontrolled CLU3 lubrication system. Sincethen, the PLS has been continuously improvedand adapted to meet the latest operatingboundary conditions. It now includes Pulse Jettechnology to provide the best possiblecylinder oil distribution on the cylinder liner andpiston rings.

Figure 11: The unique Flex common-rail systemallowing individual fuel injection characteristics andexhaust valve timing

Figure 10: Common technology platforms for the X-series


Through the use of additional isolation, reducecooling area and/or bypass cooling, great carehas been taken to increase the liner walltemperatures against cold corrosion underslow steaming conditions, thus allowingcontinuous operation at between 10% and100% load.

Automation concept

The X82 and X92 engines are controlled by ahighly redundant engine control system withdistributed intelligence.

The well proven and validated WECSembedded control system allows the engine tobe operated even if the bridge managementsystem is out of order. It features a high levelof redundancy to ensure the highest engineavailability.

Communication with external systems(Propulsion Control, Alarm Monitoring, and TierIII solutions) is facelifted by CAN or Mod-Busand is ready for interfacing with newtechnologies, such as BIG DATA.

Low maintenance costs

WinGD X82 and X92 engines are designed toachieve as much as five-year’s time betweenoverhauls (TBO).

The TBO of low-speed marine diesel enginesare largely determined by wear to the pistonrings and cylinder liners. The X-engines’ piston-running package with a chrome ceramiccoating ensures extended life time of thesecomponents, whilst maintaining lowlubricating oil consumption.

The well-proven combustion component bore-cooling principle is employed in the cylindercover, exhaust valve seat, cylinder liner, andpiston crown to control both high temperaturecorrosion and stress factors.

All other engine components exposed to wearand tear have also been further optimised toachieve a high TBO.

The crank train bearings are of white metaldesign, and the cross head bearings with theirwell proven lubricating oil pockets functionwith excellent reliability. For X82 enginesselected in the low speed area of the ratingfield (low engine speed), high pressure systemoil (10 - 14 bar) is used to ensure trouble freeoperational behaviour of the cross headbearings.

Figure 13: Cylinder bypass cooling for the lowest linerand ring wear rates at any load

Figure 12: The Pulse lubricating system withpulse jet technology to distribute the oil evenly onthe cylinder liner surfaces


4.1.3 Low pressure X-DF enginesFor the operation with LNG an additionalinjection system is required to introduce LNGinto the combustion chamber for optimumcombustion, performance and emissionresults.

The X-DF engines are the only low-speedmarine engines able to operate according tothe Otto combustion principle, which is theonly technology able to combine the use ofreliable and cost efficient low-pressure gasinjection with high performance and the lowestexhaust gas emission levels.

With the inclusion of the fuel gas supplysystem (FGSS), the propulsion system looks asfollows.

This low-pressure technology reduces NOxemissions in compliance with IMO Tier III limitswithout any additional cost intensive reductiontechnology.

The advantage of the low-pressure systemfrom a financial investment and operationalperspective is described in chapter 5.2.

4.2 Engine tuning

The X-engines can be optimised for low,partial, or high load operation. The followingtuning options can be selected:

1. Standard Tuning: high load tuning,optimised for engine loads above 90 % (inthe same way that mechanical engineshave been tuned)

2. Delta Tuning: part load tuning, optimisedfor engine loads between 75%-90%

3. Delta Bypass Tuning: part load tuning,optimised for increasing steam productionabove 50% engine load, and reduced fuelconsumption below 50% engine load.

4. Low-Load Tuning: optimised for engineloads below 75 %.

5. TC cut off: Where applicable, X82 and X92diesel engines with a multi-turbochargerconfiguration can be equipped with TC cutoff tuning that significantly reduces theengine’s fuel consumption at low loads.One of three turbochargers can be cut offto improve low load performance.

Figure 15: The low pressure fuel gas supply system(FGSS) for the low pressure X-DF engine with tank,low pressure compressor and pumps, and piping.Only low gas pressure components are required.

Figure 14: The low-pressure gas injection systemfor the X-DF engine

Figure 16: Reduced emissions of X-DF engines withlow-pressure gas technology. The NOx levelmeeting IMO Tier III limits is achieved withoutadditional equipment


An additional option is the “steam productioncontrol” (SPC). Instead of a bypass valve,which can only be fully open or closed, it canvary the bypass rate continuously. This allowsthe opening to be set according to the needsof the economizer for steam production, whileat the same time ensuring the best possibleengine fuel consumption.

4.3 Waste heat recovery

Waste heat recovery is an effective technologyfor simultaneously cutting exhaust gasemissions and reducing fuel consumption.High- Efficiency Waste Heat Recovery plantswith WinGD engines enable up to 10% of themain engine shaft power to be recovered aselectrical power for use as additional shippropulsion power and for shipboard services.These WHR plants thus cut exhaust gasemissions, deliver fuel savings of up to 10%,and improve the ship’s EEDI.

Steam based WHR plants have already beensuccessfully fitted in several installations usingWinGD low-speed marine engines. In the WHRplant, a turbo-generator combines the inputfrom a steam turbine with an exhaust gaspower turbine to generate electrical power,while steam from the economiser is availablefor the ship’s service heating.

4.4 NOx and SOx emissionreduction technologies

In order to achieve compliance with the IMOTier III NOx regulations and the requirementsfor SOx control, various solutions are possible.These may include alternative fuels, advancedtuning concepts, the addition of selectedsubstances, and after treatment systems.

4.4.1 DF readySwitching from liquid to gas fuel is a viablesolution for dealing simultaneously with boththe NOx and SOx requirements. X-engineshave been designed to be DF ready, meaningthat the standard diesel engine can beconverted to a low-pressure X-DF engine by

25 50 75 100

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target steam production

Figure 18: Variable steam production with avariable bypass for steam production control (SPC)

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Figure 17: Engine tuning options to optimize fuelconsumption for individual operational profiles

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Figure 59: Effective overall fuel consumption byapplying SPC (red curve) compared to steamincrease by a thermal boiler (green curve)

Figure 20: Layout diagram with waste heat recoverysystem


adding only the gas components. Operating ongas as X-DF, compliance with IMO Tier III NOxand SOx limits is guaranteed.

The installation of an LNG fuelled propulsionsystem, including the fuel gas supply system(FGSS), requires significantly higherinvestments for new vessels.

Therefore, from a total cost of ownership pointof view, an investment in X-DF operationsmakes sense only if LNG can be bunkered atmuch lower prices than HFO or MDO.

If the operational savings with LNG are not bigenough, operating on diesel and installing anSCR system for IMO Tier III compliance wouldbe the preferred solution.

4.4.2 SCR solutionsX-engines comply with the IMO Tier III limitsfor NOx thanks to the designed interface withSCR systems.

SCR technology reduces emissions of nitrogenoxides (NOx) by means of a reductant (typicallyammonia, generated from urea) at the surfaceof a catalyst in a reactor.

Compared to EGR, SCR is a proven technologythat has been used for decades in land basedpower plants as well as on marine engines.Due to the higher investment and maintenancecosts, as well as the imminent risk to enginereliability by re-circulating polluted exhaust gasinto the cylinder, EGR is not viewed as beingthe primary solution for compliance with theIMO Tier III NOx limits.

In the SCR reactor, the temperature of theexhaust gas is controlled to maintainconstraints on both the upper and lower sides.The latter is particularly relevant with fuelscontaining higher fractions of sulphur, such asthose present in the typical quality of heavyfuel oil (HFO).

High pressure SCR (HP SCR)

The SCR reactor is installed on the high-pressure side, before the turbine. Thisconfiguration allows the reactor to bedesigned in the most compact way because ofthe higher density of the exhaust gas.

All X-engines have been designed for easyinterfacing with HP SCR systems. A specificengine tuning for IMO Tier III allows fuelconsumption to be minimized whilst therequired exhaust gas temperature, themechanical interface for the HP SCR off enginecomponents, and the SCR valve controlsystem are controlled.

HP SCR can be operated with MDO/MGO orHFO.

Low pressure SCR (LP SCR)

The SCR reactor is installed on the low-pressure side, after the turbine. The two-stroke engine interface specifications for lowpressure SCR applications comply with allknown low pressure SCR system providers.Low pressure SCR systems are typically largerin volume, but have the possibility to beintegrated into the exhaust stack stream.

Again, the engine tuning is defined to minimizefuel consumption whilst controlling therequired after turbocharger exhaust gastemperature.

Depending on the ambient condition andselected engine tuning, slightly higher fuelconsumption than that of HP SCR may have tobe accepted.

Only MDO/MGO can be used with LP SCR.

When considering liquid fuels only, acombination of individual solutions can beapplied to control the two key pollutants NOxand SOx: For fuels with a sulphur contentbelow 0.1%, LP and HP-SCR solutions can beapplied. With high sulphur contents, a SOxscrubber has to be combined with the HP SCRsolution.

Concept 1 Concept 2Fuel MDO 0.1% S HFOSOx - SOx-scrubberNOx HP or LP SCR HP-SCR

Table 3: Concepts for addressing SOx and NOxemission compliance limitations for diesel engines


4.5 Flexible operation adaptation

4.5.1 Dual tuningDual Tuning can be selected when a specialoperating profile is required. All X-engines canbe built and certified with two different tuningcombinations.

For example, typical applications include:- Delta Bypass Tuning (DBT) and Low Load

Tuning (LLT)or- Delta Tuning (DT) and Low Load Tuning

(LLT)

These engine tuning options providecustomers with benefits in terms of specificfuel consumption, and improved exhaust gasflow and temperatures.

The engine’s NOx certification is carried outwith individual Technical Files and EIAPPcertificates for each tuning. Thus, NOxemissions on the test bed need to bemeasured for both tunings.

4.5.2 Dual ratingX-engines can be designed and shop tested fortwo different engine ratings. This means thatthe engine can have two optimised CMCRspoints following the same propeller curve.

As a consequence, the ship operator can selecttwo possible optimal service speeds,depending on the market conditions.

Figure 22: Fuel consumption optimisationpossibilities for two different operating profilesthrough the selection of two CMCRs on the samepropeller curve – savings in low load operation withCMCR_2 compared to higher rating CMCR_1.

4.5.3 Changing from diesel to LNGBoth engines, the X82-B as well as the X92,can be converted for dual fuel operation withthe emphasis on the use of LNG. The majorretrofitting work on the vessel concerns theinstallation of the LNG fuel tanks and the fuelgas supply system (FGSS):- LNG tank- Cryogenic pumps and evaporators for cold

LNG to produce LNG at max 16 bar- Optional compressor pumps for boil off gas

(BOG)- Gas valve unit to control gas pressure and

supply before the engine

The original diesel engines are modified toX82DF or X92DF respectively by:- Installation of the low pressure gas fuel

injection system- Adding the pilot fuel injection system for

ignition of the LNG engine- Install the control system for LNG

operation- Adapt the turbocharging system for LNG

operation

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Figure 21: Selection of two engine rating points onthe same propeller curve


5 Newbuilding cases

5.1 X82 and X92 for 14’000 TEUvessels

The target vessel should be able to transport14’000 TEU while meeting the followingperformance specifications:

Vessel design speed 22 KnCMCR 1 required enginepower with 76 rpm

42500 kW

As an option, a dual rating can be consideredas a means to improve the fuel consumptionfor low load operation, while applying thesame propeller:

Vessel 2nd design speed 19.3 KnCMCR 2 required enginepower with 66.5 rpm(according to propellerlaw)

28500 kW

To improve the propulsion efficiency, theimpact of a larger propeller achieving 22 Kncan be considered for an engine layout at 72rpm:

Vessel design speed 22 KnCMCR 3 required enginepower with 72 rpm(constant speedcoefficient α=0.2)

42000 kW

and a 3rd design speed:

Vessel 3rd design speed 20.3 KnCMCR 4 required enginepower with 70 rpm

33200 kW

To cover the above demand, the followingengines can be considered:

- 9X82- 7X92- 8X92

In the layout field for power and enginespeeds, the selected points look as follows:

9X82 7X92 8X92CMCR 1, 22 Kn42500 kW@76 rpm

x x x

CMCR 2, 19.3 [email protected] rpm

x

CMCR 3, 22 Kn42000kW@72 rpm

x

CMCR 4, 20.3 Kn33200kW@70 rpm

x x x

Table 4: 3 engine options for four layout points

All three engines can be applied for CMCR 1.The lower propeller speed option is availableonly with the 8X92, whereas the 9X82 engineallows the widest dual rating as requested.

For best performance, Low Load Tuning isselected. The engine’s fuel consumption ing/kWh over load for the different engines looksas follows:

Vessel speed v= 22 KnAlpha = 0.2

25,000

27,500

30,000

32,500

35,000

37,500

40,000

42,500

45,000

47,500

50,000

52,500

55,000

60 65 70 75 80 85 90

Pow

er[k

W]

Speed [rpm]

W7X92W9X82W8X92CMCR 1CMCR 2CMCR 3CMCR 4

Figure 23: CMCR selection, propeller curves andX82 and X92 engine layout field

Figure 24: Power specific fuel consumption overload for the different engine and rating selectionsfor different maximum vessel speed


Drawings of fuel consumption over vesselspeed indicate the potential of the deratedengine for low load operation below 18.5 Kn:

The 9X82 engine has the best fuelconsumption when derated by 33% power forCMCR 2, or the 8X92 when derated by 22%.The 7X92 has the highest power specific fuelconsumption in CMCR 1.

When calculating tons per day at 20.0 Kn or 18Kn, and then calculating the fuel tonsconsumed per TEU for a single trip (consideringthe longer trip with 18Kn), the followingresults can be seen:

At 20 Kn, the best fuel consumption isobtained with the 8X92, saving at least 2.3%in fuel costs compared to the 7X92 and 9X82.By taking the larger propeller for CMCR 3, thefuel costs can be reduced by an additional0.5%, thus reaching 2.8%.

The derated engines give the best results at avessel speed of 18Kn. 22% to 23% savingscan be achieved for the transport of one TEUfrom A to B by reducing the vessel speed. Thelowest fuel cost per TEU in this case can beachieved with the derated 8X92, which has a1% advantage compared to the derated 7X92and 9X82 engines.

In this specific study, the strongest derated9X82 engine (CMCR 2) would give benefits atcontinuous vessel speeds below 17 Kn.

For investment purposes, the above savingsneed to be counterbalanced against theinstallation costs and the obtainable revenue:- With a 8X92, the savings of 2.3 to 2.8%

have to be counterbalanced against a higherinvestment cost for one more cylindercompared to the 7 cylinder X92

- By derating and slow steaming, thereduced cost per TEU needs to beconsidered in view of the fewer number ofvoyages the vessel can make per year,thereby reducing the income for the vessel.The additions to the operational costs tocover the higher financing costs for thevessel need to be increased to ensure thesame payback time (see explanation inchapter 3.1).

5.2 12X92 and 12X92DF for DFready 20’000 TEU vessels

The target vessel with a 20’000 TEUtransportation capacity should meet thefollowing performance specifications:

Vessel design speed 22 KnCMCR required enginepower with 78 rpm

60’000 kW

The ship owner anticipates switching to LNGwhen the HFO sulphur cap is reducedworldwide to a maximum of 0.5%. The vesselshould be run at the same speed with bothdiesel and LNG. The engine therefore shouldbe easily convertible to X-DF for dual fueloperability.

At the time of conversion, IMO Tier III NOxcompliance is also required.

Figure 25: Power specific fuel consumption drawnover ship speed.

Figure 26: Comparison of fuel ton / hour andresulting savings in % per TEU transported from Ato B at 20Kn and 18Kn speeds


The best selection for this requirement is the12X92/12X92DF engine:

It is important to note the Tier III complianceof the 12X92DF compared to the 12X92engine, since the installation of NOx reducingsystems, on or after the engine, are notrequired. Furthermore, CO2 and particulatematter can also be reduced considerably. Allthese low values are achieved not only in ECAareas, but whenever the engine is operatedwith LNG fuel.

A switch to LNG operation starts to makessense with the much lower price of LNGcompared to low sulphur HFO (LSHFO). In thefollowing case study, it shall be assumed thatLSHFO costs 500 USD / ton and LNG 400USD / ton.

With savings of some 24’000 USD per daywhen running continuously at 80% load,annual savings of about 6 Mio USD can beconsidered. Taking into consideration theinvestments needed for operating the vesselon LNG, including the LNG fuel handling

infrastructure and the engine, which one canassume to be in the range of 30 to 50 MioUSD, the payback time would be 5 to 9 years.

40,000

45,000

50,000

55,000

60,000

65,000

70,000

75,000

80,000

65 70 75 80 85

Pow

er[k

W]

Speed [rpm]

W12X92

W12X92DF

CMCR

Figure 27: Operating line in the engine layout fieldsfor the 12X92 and 12X92DF engines

0

20

40

60

80

100

120

CO2 NOx SOx PM

Emiss

ions

(%)

12X92 12X92DF_diesel

Figure 28: Emissions reduction comparisonbetween the 12X92 in diesel operation and the12X92DF in LNG mode.

89.0

65.2

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

0.0

25.0

50.0

75.0

100.0

125.0

150.0

12X92 12X92DF_bsfc_eq

Fuel

cons

umpt

ion

savi

ngs

/trip

/TEU

Fuel

cost

kUS$

/day

US $/day Savings/TEU/trip

Figure 29: Fuel costs per day and savings with LNGcompared to diesel at a continuous 80% loadassuming a fuel price of 400USD/ton for LNG and500 USD/ton for low sulphur HFO.


6 Conclusions

The WinGD X82 and X92 low-speed dieselengines and their related versions, the X82DFand X92DF for LNG operation, representoptimal propulsion engine solutions for verylarge container vessels with freight capacitiesbetween 8’000TEU and 22’000TEU.

One great advantage is the high level offlexibility by which the engines can beconfigured. The various engine tunings andratings to optimize the operation for differentoperating profiles and varying fuel costscenarios, as well as the possibility to use anydiesel fuel or LNG, provide the means offinding the optimum installation for any need.As such, these engines can meet customerrequirements, both at the initial project stageas well as after some years of operation. Theengines can be adapted with low modificationcosts for any future new boundary conditionsregarding the vessel’s operational profile, fuelapplication, or environmental regulations.

The data contained in this document serves informationalpurposes only and is provided by Winterthur Gas & DieselLtd. without any respective guarantee.

engine selection for very large container vessels

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