MAN B&W Auxilliary Engines

7/29/2019 MAN B&W Auxilliary Engines

1/18

Page 1 (18)

08031-0D/H5250/94.0

9.0

7

Installation Aspects ofMAN B&W Main and Auxiliary Engines

037/95.47

Contents: Preface

The MAN B&W diesel main and auxiliaryengine programmes

Two-stroke MC enginesFour-stroke GenSets

Fuel oil system- The 'Unifuel' system

Fuel oil systemDesign features and working principle

Operation at seaOperation in port

Central cooling water systemDesign features and working principleOperation at seaOperation in port

Starting air systemDesign features and working principle

Lubricating oil system

CoCoS - Computer Controlled SurveillanceCoCoS modules

Joint services main and auxiliary enginesMain and auxiliary engine spare partsCommon tools

Emission control and compliance

This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net


2/18

Page 2 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Preface

When the required vessel power profile has beenevaluated and determined, both with regard topropulsion load and electrical load, the next step is todesign the engine room configuration so that it willalso be optimal with regard to installation, operationand maintenance. MAN B&W Holeby has not onlylooked at this as an isolated case for the L16/24 typeauxiliary engines but, as described in the following,has also looked at it in relation to the MAN B&W two-

stroke main engine on board.

The goal is to make the layout of the engine room andthe operation and maintenance work in service assimple and effective as possible without jeopardizingthe safety on board. A further aspect has been com-pliance with emission regulations.

The unifuel system is the proof of this where the fueloil, cooling water and starting air systems are anintegrated entity, minimizing the use of componentsand space, lowering the first cost, and providingsimpler operation and maintenance.

In projects where both an MAN B&W main engineand MAN B&W auxiliary engines are ordered, pos-sibly even from the same supplier, the buyer willhave fewer contact people, common delivery andstand stronger in the negotiations of the price andextent of delivery. Even if the engines are orderedfrom different suppliers, there are still all the advan-tages mentioned in the following chapters of thispaper, and the possibility of having the best econo-mical choice of main and auxiliary engines, includingthe optimum solution in engine layout, power re-

quirements for auxiliary systems, system diagrams,list of necessary capacities and technical advice onsystems that deviate from MAN B&W Diesel stan-dard.

For a typical project, with one two-stroke propulsionengine and three auxiliary engines, commoninstallation documentation can be prepared andsupplied to the yard and the end-user. In suchmaterial, the advantages of choosing both main andauxiliary engines of MAN B&W design will be givenin detail, based on project-related engines.



3/18

Page 3 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

The MAN B&W Main and Auxi-

liary Engine Programmes

Two-stroke MC engines

The MC engines have been onthe market for thirteen years du-ring which time more than 3,500

engines have been sold. Inter-nationally recognised as thepri-me mover in merchant vessels

and power plants, the MC enginedoes not need many introductoryremarks for those involved ineither of these two fields. A re-ference list is given in Fig. 1.

The MC engine programme isconstantly being developed andis extremely comprehensive, of-fering the optimum prime moverfor each and every application.This is illustrated in Fig. 2, whichshows the engine programme of-

fered to the marine market.

Fig. 3 shows data indicating theevolution in ratings. There havealso been substantial componentimprovements.

Fig. 1. MC engines on order and in service as at 1st September,1995

No. of engines

On orderType or delivered In service

90MC 121 7180MC 339 307

70MC 456 36960MC 1,046 891

50MC 686 49542MC 132 10635MC 634 524

26MC 131 115

Total 3,545 2,878

Total = 52,188,000 BHP ~ 38,384,000 kW

Fig. 2. The MC marine engine programme 1995

Such improvements in component design, and thesubsequent increases in engine ratings, have been

possible only due to the extensive amount of serviceexperience gained with the MC engines, and thecontinuous use of more and more advanced cal-culation techniques.

The engines in the present MC programme are givenMk V or Mk VI designations, where all engines witha mean effective pressure of 18 bar and above arereferred to as Mk VI engines, and all others in thecurrent programme as Mk V engines.



4/18

Page 4 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Mk I II III V Mk III V VI Mk III VI Mk (III) V VIintroduced 1982 1984 1986 1991 introduced 1986 1991 1993 introduced 1986 1993 introcuced 1988 1991 1993

L50MC K80MC S50MC K80MC-C

bhp/cylinder 1440 1550 1650 1810 bhp/cylinder 4240 bhp/cylinder 1780 1940 bhp/cylinder 4410 4630 4900mep 15 16.2 16.2 17 mep 16.2 mep 17 18 mep 16.2 17 18r/min 133 133 141 148 r/min 100 r/min 123 127 r/min 104 104 104

L60MC K90MC S60MC K90MC-C

bhp/cylinder 2080 2240 2360 2600 bhp/cylinder 5360 5870 bhp/cylinder 2550 2780 bhp/cylinder 5590 5860mep 15 16.2 16.2 17 mep 16.2 17 mep 17 18 mep 16.2 17r/min 111 111 117 123 r/min 90 94 r/min 102 105 r/min 104 104

L70MC K90MC S70MC K90MC-Cbhp/cylinder 2830 3040 3200 3560 bhp/cylinder 6220 bhp/cylinder 3490 3820 bhp/cylinder 6210mep 15 16.2 16.2 17 mep 18 mep 17 18 mep 18r/min 95 95 100 106 r/min 94 r/min 88 91 r/min 104

L80MC S80MC

bhp/cylinder 3690 3970 4210 4670 bhp/cylinder 4560 4950mep 15 16.2 16.2 17 mep 17 18 Mk VIr/min 83 83 88 93 r/min 77 79 introduced 1994

L90MC S90MC-T K98MC-C

bhp/cylinder 4680 5040 5310 5860 bhp/cylinder 6200 bhp/cylinder 7760mep 15 16.2 16.2 17 mep 18 mep 18.2

r/min 74 74 78 82 r/min 75 r/min 104

Fig. 3. Design development of the MC engines

With regard to the testing of engines and auxiliarycomponents, the various MAN B&W departmentsexchange test results on a regular basis. This gives

the other sectors of our organisation access to theaccumulated experience and to the latest techno-logy.



5/18

Page 5 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Four-stroke GenSets

MAN B&W Holeby have produced GenSets forabout 75 years. The number of engines sold ofthe current Generating Set programme appear fromFig. 4.

The L16/24 GenSet covers a lower power range thanthe existing L23/30H, which means that the totalprogramme will cover a larger range.

The output ranges of the engine programme areshown in Fig. 5 and, as will be seen, they are able tocover the power needs of practically all ships in themerchant fleet today.

Fig. 5. Four-stroke layout areas

No. of engines

On order

Type or delivered In service

L23/30 1,166 923

L28/32 795 677

V28/32 51

Total 2,012 1,600

Total = 4,054,291 BHP ~ 2,981,931 kW

Fig. 4. Auxiliary engines on order and in service



6/18


7/18

Page 7 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Fig. 7. Electrical power requirements for tankers and bulk carriers equipped with MC engines

For the ship-dependent electricity consumption, wehave calculated with the following consumers: bowthrusters (300 - 1500 kW depending on ship type/size), ventilation, air condensing, separation equip-ment, etc.

We assume that during manoeuvring the electricalconsumption is twice that for calm sea operation andthat two auxiliary engines running at 80% load arecapable of delivering the entire electrical power

requirement during manoeuvring.

In Fig. 7 we have calculated the electrical powerrequirement for the MC engines in tankers and bulkcarriers.

The requirement for auxiliary power is very indi-vidual, however, our calculations are based onexamples of data obtained from shipowners andyards. In the column for engine-dependent electricalpower consumption, we have included all standardauxiliary systems, including auxiliary blowers.



8/18


9/18

Page 9 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

With such equipment, adequate separation of waterand fuel can be carried out in the centrifuge, for fuelsup to a density of 1010 kg/m3 at 15C. Therefore, thishas been selected as the density limit for new highdensity fuel grades.

Thus high density fuels are fully acceptable for ourengines provided that appropriate centrifuges areinstalled. They should be operated in parallel or inseries according to the centrifuge makers instruc-tions.

This recommendation is valid for conventional cen-trifuges. For more modern types, suitable for treatingfuels with densities higher than 991 kg/m3 at 15C, itis recommended to follow the makers specificinstructions.

In view of the fact that some fuel oil standardsincorporate fuel grades without a density limit, andalso the fact that the traditional limit of 991 kg/m3 at15C is occasionally exceeded on actual deliveries,some improvements in the centrifuging treatment

have been introduced to enable the treatment offuels with higher density.

Fig. 10. Fuel oil centrifuges - series and parallel operation



10/18

Page 10 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Fuel oil system

Design features and working principle

The fuel oil system is a common, pressurised sy-stem in which both heavy fuel oil and diesel oil can

be used. The purpose of pressurisation is primarilyto avoid boiling and cavitation in the system, which

may occur when the heavy fuel oil is heated toachieve the viscosity of 10-15 cSt required forinjection.

Fig. 11. Fuel oil system



11/18

Page 11 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Operation at sea

The fuel from the bunker tanks must be treated incentrifugal separators before entering the servicetanks. From the service tanks, the fuel enters thesupply system.

In the supply system, the fuel is pumped by thesupply pumps, into a circulating system at a pres-sure of 4 bar. The supply system may include a finefilter. All overflow from the supply pumps is recir-

culated in the by-pass piping, which incorporates theoverflow valve shown in order to keep the inlet pres-sure in the circulation loop constant, irrespective ofthe actual consumption.

The pumps in the circulation loop, raise the pressureof the fuel oil from the supply system to a constantinlet pressure of 7-8 bar before the engines. The inletpressure is maintained at the specified level by aspring-loaded overflow valve located on the mainengine. The temperature or viscosity controlled pre-heater heats the heavy fuel oil until it reachesthe necessary viscosity. To safeguard the injection

system components on the main engine, a full-flow50 filter, must be installed as close to the mainengine as possible. Such a filter is already built ontothe auxiliary engines.

Excess fuel oil supplied to the engines is recirculatedvia the venting box, where gases, if any, are releasedby a deaerating valve, to avoid cavitation in thesystem.

The flexibility of the system makes it possible, ifnecessary, to operate an auxiliary engine on diesel

oil by means of remote controlled 3-way valves,which should be located close to the auxiliaryengines.

A separate booster pump supplies diesel oil fromtank 2 to the auxiliary engines and returns any ex-cess oil to the tank. In order to ensure operation ofthe booster pump in the event of a black-out, thebooster pump must have an immediate possibility ofbeing powered by compressed air or by powersupplied from the emergency generator.

A 3-way valve is installed immediately before eachauxiliary engine for change-over between the pres-surised and the open MDO (Marine Diesel Oil)

supply system.

In the event of a black-out, the 3-way valve at eachauxiliary engine will automatically change over to theMDO supply system. The internal piping on theauxiliary engines will then, within a few seconds, beflushed with MDO and be ready for start up.

Operation in port

During operation in port, when the main engine isstopped, but power from one or more auxiliary engi-

nes is still required, the supply pump should berunning. One circulation pump should always bekept running when there is heavy oil in the piping.

The by-pass line with overflow valve between theinlet and outlet of the main engine serves the pur-pose of by-passing the main engine if, for instance,a major overhaul is required on the main engine fueloil system. During this by-pass, the overflow valvetakes over the function of the internal overflow valveof the main engine.



12/18

Page 12 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Central Cooling Water System

Central cooling waterJacket cooling waterSea water

Sea wateroutlet

Thermostaticvalve

Thermostaticvalve

Scavengeair cooler(s)

Main engine

Expansion tankfor fresh water

Lub. oilcooler

Jacketwater cool.

Fresh watergenerator

Jacket waterpumps

F3

P K

ML

N

F3 F3

G2G2 G2G1G1 G1

Centralcooler

Central coolingwater pumps

Sea waterpumps

Sea waterinlet

Sea waterinlet

Sea waterpump aux.eng. (portservice)

Central coolingwater pump aux.eng. (port service)

Camshaftlub.oil cool.

Deaerating tankalarm device

Deaeratingtank

Open at seaClosed in port

Closed at seaOpen in port

DeaeratingPort service

A

A

A

B

B

B

Fig. 12. Central cooling system


The central cooling system is an alternative to theconventional seawater cooling system, based on the

same design principles with regard to cooler lo-

cations, flow control and preheating, but with a cen-tral cooler and one additional set of pumps.



13/18

Page 13 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Maintenance work is minimised by the use of acentral cooler, as this is the only component that isin contact with seawater. All other parts of thesystem use inhibited freshwater in accordance withMAN B&Ws specifications.

The low and high temperature systems are directlyconnected to gain the advantage of preheating themain and auxiliary engines during standstill.

As all fresh cooling water is inhibited and common for

the central cooling system, only one common ex-pansion tank is necessary for deaeration of both thelow and high temperature cooling systems. This tankaccommodates the difference in the water volumecaused by changes in the temperature.

To prevent the accumulation of air in the cooling wa-ter system, a deaerating tank is located below theexpansion tank. An alarm device is inserted betweenthe deaerating tank and the expansion tank so thatthe operating crew can be notified if excess air or gasis released, as this signals a malfunction of enginecomponents.

Operation at sea

The seawater cooling pumps pump seawater fromthe sea chests through the central cooler, and over-board. Alternatively, some shipyards use a pump-less scoop system. On the freshwater side, the cen-tral cooling water pumps circulate the low-tem-perature freshwater, in a cooling circuit, directlythrough the lubricating oil coolers of the main en-gine, the auxiliary engines and the scavenge air

coolers.

The jacket water cooling system for the auxiliaryengines is equipped with engine-driven pumps anda by-pass system integrated in the low-temperaturesystem, whereas the main engine jacket system hasan independent pump circuit with jacket waterpumps, circulating the cooling water through themain engine to the freshwater generator and thejacket water cooler.

A thermostatically controlled 3-way valve at the jac-ket cooler outlet mixes cooled and uncooled water tomaintain an outlet water temperature of 80-85 Cfrom the engine.

Operation in port

During operation in port, when the main engine isstopped, but one or more auxiliary engines arerunning, valves A are closed and valves B are open.A small central water pump will circulate the neces-sary flow of water for the air cooler, the lubricating oilcooler, and the jacket water cooler of the auxiliaryengines. The auxiliary engine-driven pumps and theabove-mentioned integrated loop ensure a satis-factory jacket cooling water temperature at the

auxiliary engine outlet.

The main engine and the stopped auxiliary enginesare preheated by the operating auxiliary engine(s).

Starting Air System


Two air compressors, with automatic start and stop,maintain a starting air pressure of 30 bar in thestarting air receivers.

The main engine is supplied with 30 bar starting airdirectly from the starting air receivers. Through apressure reduction station, compressed air at 7 baris supplied as control air for the engine manoeuvringsystem, and as safety air for the emergency system.

Starting air and control air for the auxiliary engine(s)is also supplied from the same starting air receivers,via reducing valves that lower the pressure to a valuesuited to the actual type of MAN B&W four-strokeauxiliary engines chosen.

An emergency air compressor and a starting airbottle are installed for redundant emergency start ofthe auxiliary engines.

If high-humidity air is sucked in by the air com-pressors, an oil and water separator will removemoisture drops present in the 30 bar compressed air.When the pressure is subsequently reduced to 7 bar,as for the main engine manoeuvring system, the hu-midity in the compressed air will be very slight.Consequently, further air drying is considered unne-

cessary.



14/18

Page 14 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Fig. 13. Starting air system

From the starting air receivers, a special air lineleads to the valve testing equipment.

Lubricating Oil System

The lubricating oil systems cannot be combined, anddifferent grades of main lubricating oil may have tobe used, as the auxiliary engines operate without

stuffing boxes, and their combustion chamber is thusnot completely isolated from the oil sump. Thelubricating oil for the auxiliary engines therefore hasto have a higher TBN to obtain the appropriateneutralisation of sulphuric acid formed duringcombustion. An initial TBN level of at least 20 is

recommended for GenSets, whereas two-strokemain engines use TBN 5.



15/18

Page 15 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

CoCoS Computer Controlled Surveillance

CoCoS is a software program package for helpingthe engine room crew. CoCoS consists of fourmodules that can be used individually or together.The modules can help in fault finding, work planning,managing ships stock and handling spare partsorders. An electronic version of the instruction bookwill also be included in the complete package.

CoCoS has been developed within the MAN B&W

Diesel group and, in the programming, both MANB&W Diesels main engine and auxiliary engineshave been considered.

The development work is being performed as aninter-company project, involving MAN B&W Diesel inCopenhagen (MBD-K), Alpha Diesel (MBD-F),Holeby Diesel (MBD-H), MAN B&W Diesel inAugsburg (MBD-A) and Pielstick in France. Theengine diagnostics part is being developed on thebasis of the experience gained with MBD-Ks CAPA,MBD-As Modis and MBD-Hs HGM and will, whenfinished, be able to replace these products. The

three other modules include areas that are new to us.

CoCoS modules

The system consists of four modules:

CoCoS-EDS - Engine Diagnostics System CoCoS-MPS - Maintenance Planning System CoCoS-SPC - Spare Parts Catalogue CoCoS-SPO - Stock and Parts Ordering System

CoCoS-EDS is a system in which data from theengine is processed. Data can be collected directlyfrom sensors located on the engine. Data can alsobe keyed into the system manually.

What can CoCoS be used for? Well, values can beprocessed and compared with the values they oughtto be. On this basis a trend (tendency) is calculated,for example, how the various parameters willdevelop/change with time. All this can be used to findout whether something is wrong. If somethingabnormal is observed, it will be analysed/diagnosed,

and the result will be a diagnosis. One can make thecomparison with a doctor who makes a diagnosisand prescribes medicine. The medicine which the

system will prescribe here is a job of work. The workwill be ordered in the CoCoS-MPS module.

A Beta-version of CoCoS-EDS has been in ope-ration in a container vessel since July 1994, and thecrew has expressed great satisfaction. CoCoS-MPS, CoCoS-SPC and CoCoS-SPO becameavailable for Beta-testing in 1995.

CoCoS-MPS is used primarily for planning theinspection and maintenance work that must be

performed after a certain number of service hours orcalendar days. Jobs are listed and presented visu-ally. In this way, the user can see when and whatshould be done, choose jobs and make work sche-dules that suit the sailing schedule. CoCoS-EDS canbe used to specify personnel, work tools and spareparts that should be employed to make work gowithout a hitch.

CoCoS-EDS also contains a reporting function forthe recording of jobs that have been completed.Historical data concerning the different jobs can belogged, so as to retain valuable work experience.

The instruction book will also be included in thismodule, not only in the form of text and graphics but,in future versions, also in the form of video clips of thevarious jobs considered relevant. With video clipsincorporated in CoCoS-MPS, the user need not viewan entire film to get information, but can make do withjust those sequences which are actually needed.

CoCoS-SPC is an electronic catalogue that can beused to identify spare parts. Components can befound in three ways: by using a search word; by

clicking on a drawing (by this means one can zoomin on specific areas or parts of drawings, simply byclicking on them with the mouse, so that individualparts and components can be examined in moredetail); and a further possibility is a systematicbreakdown of the Plate / Item parts list, for example,to find a piston.

CoCoS-SPO is a combined inventory and spareparts ordering system which can be used to obtain allinformation about the size, weight, location on boardship of an individual component, how many there arein stock, etc. It will also be possible to follow-uphistorically on large components.



16/18

Page 16 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

The ordering part of the system gives the crew anadministrative tool for ordering spare parts from theshipowner or supplier and, at the same time, keepingcheck of all orders.

Joint Services Main and Auxiliary Engines

Main and auxiliary engine spare parts

Spare parts for the Holeby GenSets are produced in

accordance with the same demanding specifica-tions that are valid for the GenSets themselves.

The worldwide operation of Holeby GenSets isbacked-up by a spare parts stock containing over15,000 different items. The fastest possible deliveryof these parts depends on our receiving completeand accurate forwarding details.

To enable the fastest processing of marine spareparts orders, contact is to be made to Diesel Servicein Copenhagen, or one of our local offices, givingthem all details.

Because the same departments in Copenhagen areinvolved with spare part orders for the main engine,the same contacts, the same systems, the samehigh quality of spare parts are available for theHoleby GenSets. Accordingly, the newly introducedunit concept of cylinder covers, complete with val-ves, etc., being forwarded for parts exchange/recon-ditioning purposes to MAN B&W Diesel in Copen-hagen or one of our service centres will be treated inthe same way.

Common tools

In order to simplify overhaul, as well as to saveinvestment, space and stocks, the MAN B&W two-stroke engines and the Holeby GenSets can share anumber of common tools.

The following tools are normally the same for theMAN B&W Diesel main engine and the auxiliaryengines:

- Air driven high pressure pump for hydraulictools

- Manual high pressure pump- Eye screw for lifting of piston- Shackle for lifting of piston- Torque spanner- Max. pressure indicator

- Pressure testing pump for fuel valve.

Emission Control and Compliance

Emission rules and emission control techniques are

being discussed and developed internationally,nationally and regionally, particularly as regards NOx

and SOx.

Fig. 14 shows the internationally applicable targetlevels proposed by IMO the International MaritimeOrganisation.

Fig. 14. Proposed IMO emission limits

Another proposed rule is that of the EPA (Envi-ronmental Protection Agency) for the west coast ofthe USA based on a user fee penalty, depending onthe actual NO

xemission level.

These two sets of rules represent two very differentapproaches. Most other bodies seem to be taking a

wait-and-see attitude until these proposals havebeen fully discussed and developed.



17/18

Page 17 (18)

08031-0D/H5250/94.0

9.0

7


037/95.47

Fig. 15. NOxreduction potential shown with primary methods

While chemical methods and washing/scrubbingprocesses to remove SO

xfrom the exhaust gas are

known, the most pragmatic and economical ap-proach would probably be to control the fuel oilsulphur content. From the legislation and controlpoints of view this is the simplest approach.

As far as diesel engines are concerned, a reductionin the fuel oil sulphur content from the currentmaximum of 5% to a realistic lower value wouldinvolve no technical complications. Consequently,

efforts are being concentrated on NOx control me-thods.

It is realised that, irrespective of the rules, policing ofcompliance will be difficult. The California EPA willgenerally give economical favours to those withlower NO

x, as illustrated in Fig. 14, making policing

more demanding.

Owners are already starting to specify emissionmeasurements as part of shop-testing. Verificationof engine performance by testbed running will infuture be meaningless without corresponding emis-

sion measurements.

The technical possibilities for NOx

reduction in lowspeed diesels include both primary (internal) me-thods and secondary (external) methods.

Obviously, the market favours primary methods ofmeeting requirements like those proposed by theIMO and, indeed, this is the most practicable ap-proach.

Fig. 15 shows that with primary methods an 80%

reduction has been achieved on an S70MC enginein test conditions.

The IMO proposal assuming a reasonable andpragmatic formulation can be met with our mainengines using primary methods of NO

xcontrol,

whereas the generator set engines already meetIMO.

When using water emulsification (i.e. water emul-sified into the heavy fuel) or primary methods ofreducing the NO

xto the IMO level, the fuel injected

into the auxiliary engine will also have water addedwhen the unifuel system is being used.

This, however, is only an advantage since therelatively low NO

xlevel for the L16/24 engine will be

reduced further, with no disadvantage on engineperformance.

Fig. 16 shows the expected NOx

levels at different

loads for the L16/24 GenSets.

If further NOx

reduction to an extent calling forsecondary methods will be required, this can bedone by SCR (Selective Catalytic Reduction). Thetwo-stroke engine will require its own catalyst, butthe L16/24 auxiliary engines can operate on acommon catalyst. For the L16/24, primary methodshave great potential, and catalysts are not foreseen.



18/18

Page 18 (18)

08031-0D/H5250/94.0

9.0

7


Fig. 16. Expected NOxlevel for the L16/24 type engine

Note!

All our product ranges are constantly under review,being developed and improved as needs and condi-tions dictate.

We therefore reserve the right to make changes to

the technical specification and data without priornotice.

Documents

MAN B&W Auxilliary Engines