paper no.: 128 new turbochargers for more powerful engines running under stricter ... ·...

CONSEIL INTERNATIONALDES MACHINES A COMBUSTION

INTERNATIONAL COUNCILON COMBUSTION ENGINES

PAPER NO.: 128

New turbochargers for more powerful enginesrunning under stricter emissions regimes

Peter Neuenschwander, ABB Turbo Systems Ltd, SwitzerlandMartin Thiele, ABB Turbo Systems Ltd, SwitzerlandMartin Seiler, ABB Turbo Systems Ltd, Switzerland

Abstract: The latest and coming rounds of emis-sions legislation for reciprocating engines in ma-rine, stationary and mobile applications require muchcleaner exhaust gas emissions. At the same time, de-mand for higher engine power density and reduced lifecycle costs is steadily increasing, with the latter andthe volatile price of fuel translating into the underly-ing requirement that improvements be achieved at un-changed or reduced specific fuel consumption.

The possible technical solutions for meeting thetargets described depend on the field of applicationof the engines. These differ widely and, with its roleas a central influence on the combustion process,decisively affect the demands made on - and by -the turbocharging system. The simultaneous achieve-ment of emissions compliance, targeted power densityand lowest specific fuel consumption are decisivelyaffected by charge air pressure and particularly withlow speed engines exhaust gas receiver pressure asa function of engine load and engine speed. Basedon these values, the turbocharger air pressure ratioand efficiency can be derived. Other parameters, like

the specific volume flow of the compressor, variableelements of the turbocharging system and the designof the turbocharger itself, are mainly related to eco-nomics, service-friendliness and reliability as well asto the physical restrictions imposed by flows and ma-terials.

In a first step, this paper discusses the principalthermodynamic requirements of turbocharger designfor diesel and gas engines with enhanced emissions,higher power density and optimised fuel consumptionand how they have evolved for the three major enginetypes i.e. low, medium and high speed.

In a second step, using the evolution of ABB’s A100turbocharger generation as an example, the practicalrealisation of turbocharging systems for the fulfilmentof these requirements is described, including the prod-uct objectives reliability and service friendliness. Thepaper emphasises the new technical features againstthe background of future engine requirements but alsojustifies the retention of well-proven principles frompredecessor generations. Finally, the paper concludeswith a summary of field experience to date is given.

c©CIMAC Congress 2010, Bergen

© CIMAC Congress 2010, Bergen Paper No. 128 2

INTRODUCTION

In anticipation of the IMO Tier II emissions limits and market demand for diesel and gas engines with higher power densities and lower fuel consumption, around the middle of the past decade ABB began to look closely at the impact of the factors on turbo-charging and turbochargers. Discussions with en-gine-builders and end-users, plus a detailed market analysis, showed, that the new engines would re-quire compressor pressure ratios and efficiencies which were significantly higher than those currently available. As well as forecasts of a steady, long term rise in the price of fuel, increased awareness of greenhouse gas emissions reinforced fuel con-sumption as a key priority. As a result of its investi-gations ABB has developed the A100 turbocharger generation which is now being introduced to the market (Figure 1).

Figure 1 ─ A100 turbocharger generation A100-L with VTG in the frame-size A175-35T

In this paper the new turbocharger A100-H for high speed engines, the A100-M for medium speed en-gines and the A100-L for low speed engines – all for single-stage turbocharging applications – are presented. From the starting point of the different engine applications to be covered and the impact of turbocharger efficiency and compressor pressure ratios on fuel consumption and emissions, the dis-tinct solutions which emerged for the various turbo-chargers are explained.

THERMODYNAMIC REQUIREMENTS

Operating conditions of engines and turbochargers for engines with power output above 500 kW

In accordance to the engine segments and to match their specific operating conditions and re-quirements, three dedicated turbochargers series are offered.

The A100-H turbochargers are designed for high speed engines requiring light diesel fuels, natural gas or comparable gases as fuels. Scavenging of the cylinders is not needed or is minimised in case of pre-mixing of gas and air. The engines and tur-bochargers may experience exhaust gas tempera-tures up to 750 °C due to comparable low air to fuel ratios. Miller valve timing for the inlet valves is well established as a way of reducing NOX emissions and fuel consumption. The reduction of NOX emis-sions using primary measures is currently limited by achievable charge air intake pressures delivered by the turbochargers. Secondary methods of emis-sions reduction might be readily adapted from the truck industry. Load acceptance specifications are often essential as well as the altitude capability of the charging system. The first cost of high speed engines is absolutely decisive for emergency power supply applications or other engines with short run-ning hours under full load operation.

A100-M turbochargers are designated for medium-speed engines operated on heavy or distillate ma-rine fuel oils, natural gas or comparable gases. Scavenging of the cylinders is needed when heavy or distillate fuel oil is used. Exhaust gas tempera-tures are limited to approximately 550 °C with heavy fuel oil for continuous operation due to com-bustion deposits and material characteristics. The Miller Cycle, involving revised inlet valve timing is well established as a way of reducing NOX emis-sions minimising fuel consumption penalties. De-pending on the application and intensity of the Miller Cycle, even fuel savings can be realised. The primary reduction of NOX emissions is currently limited by achievable air intake pressures produced by the turbochargers. Selective catalytic reaction (SCR) is an established method of secondary re-duction of NOX emissions and does not influence the turbocharger since the catalyst is installed after the turbocharger. Exhaust gas recirculation (EGR) is subject of industrial research and will impact the choice and specification of the turbocharger.

A100-L turbochargers are specifically designed for low speed engines which typically operate on heavy fuel oil. Scavenging of the cylinders is a must. Ex-haust gas temperatures need to remain below 520 °C. IMO Tier I emissions limits are fulfilled via fuel injection measures e. g. retarded injection and “rate shaping”. Primary methods to fulfil the IMO Tier II emissions limit compromise fuel con-sumption as long as air receiver pressure is not in-creased. This aspect drives the requirement for higher turbocharger compressor pressure ratios. SCR is established as a method of secondary re-duction of NOX emissions but there are few appli-cations in the field. SCR catalysts have impacts on the turbochargers due to their large thermal capac-


ity and the exothermic reaction involved. EGR is subject of research. At the time of writing pilot field tests are scheduled to begin in the near future. The impact of EGR on the choice and specification of the turbocharger may include the addition of vari-able turbine geometry (VTG) to give smooth engine operation when switching the EGR unit on and off.

Impacts of charging systems on thermodynamic turbocharger requirements

Constant pressure charging is applied on low speed and high speed engines. However, the charging of these engine types is fundamentally different. As mentioned, the functioning of low speed two stroke engines relies on scavenging of the cylinders whereas high speed engines do not need scav-enging. With constant pressure systems, scaveng-ing is driven by the pressure difference between the air and exhaust receivers, which remains nearly constant over the whole engine cycle. The pressure difference between the receivers is directly related to turbocharger efficiency and exhaust gas tem-perature. The unscavenged cylinder of a high speed engine contains residual gas. To feed the cylinder with the same amount of ambient air, higher air-receiver pressures are necessary. Com-pared to low speed engines, high speed engines accept higher pressure ratios and lower thermody-namic efficiency in the turbocharging system therefore.

Pulse charging is applied for high and medium speed engines. On the one hand it supports the scavenging of the cylinders by making use of the pressure variation in the exhaust pipes, which in-creases the pressure difference to the air-receiver. On the other hand it provides powerful exhaust pulses to the turbine due to reduced losses at the exhaust valves and via the higher pressure reach-ing the turbine.

Meeting the demands of the emissions legislation

Emission legislation coming into effect in the near future can be met for all engine types using primary methods of emissions reduction and single-stage turbocharging. By contrast, for engines with very high mean effective pressures, or for engines oper-ated in areas with especially strict emissions legis-lation, two-stage turbocharging or SCR as a secon-dary method are already necessary. Nonetheless, the following considerations focus on engines to be operated under IMO Tier II and equivalent emis-sions regulations.

TURBOCHARGER THERMODYNAMIC REQUIREMENTS

Figure 2 shows the progression of compressor pressure ratio requirements in the various engine segments and Figure 3 shows the associated tur-bocharger efficiencies.

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Figure 2 ─ Required compressor pressure ratios depending on engine type and mean effective pressure

It is noteworthy that the pressure ratio requirements in the high speed segment are rising faster than in other segments due to gas engine applications. The requirements are set to reach a level comparable with the medium speed segment.

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Figure 3 ─ Required turbocharger efficiencies depending on engine type and mean effective pressure

The analysis of the thermodynamic requirements on the turbochargers shows only slight differences between the high and medium speed segments but major differences to the low speed segment.


Effects of deviations between thermodynamic requirements and effective performance

The fuel consumption and the NOX emissions of a diesel engine are inversely proportional to each other when the widespread technique of retarded fuel injection timing is the only NOX reduction measure used. If the engine is tuned for lower emissions, brake specific fuel consumption (bsfc) increases. This correlation is valid for high, medium and low speed engines. An early start of combus-tion reduces fuel consumption while a late start of combustion lowers NOX emissions (Figure 4).

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Figure 4 ─ Example correlation of NOX emissions / brake specific fuel consumption and impact on this correlation of air receiver pressure / turbocharging efficiency

However, an increase in air receiver pressure and higher turbocharging efficiency can compensate the higher fuel consumption to a certain degree. Based on an engine with 4.2 bar air receiver pressure and a turbocharging efficiency of 66%, the impact on NOX emissions and fuel consumption is shown for a 3 % increase in turbocharging efficiency and a 1.3 bar increase in air receiver pressure in Figure 4.

Depending on turbocharger make and model, the air receiver pressure and turbocharging efficiency achieved will differ. The impact on fuel consumption of deviations in turbocharger performance is shown in Figures 5 and 6 for constant NOX emissions. The increase in air receiver pressure allows more ag-gressive Miller timing. The increase in turbo-charging efficiency is used via adjustments to in-take- and exhaust-valve timing.

The sensitivity of fuel consumption to air receiver pressure and turbocharger efficiency is marked as a dotted field due to the range of various influencing factors.

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Figure 5 ─ Sensitivity of brake specific fuel con-sumption with respect to changes in air receiver pressure

This sensitivity depends on the engine type and on the application conditions, in particular on the ab-solute level of the air receiver pressure, the ambient air temperature and pressure and on the mechani-cal capabilities of the engine with regard to maxi-mum cylinder pressure and valve actuating forces. Some of these dependencies are discussed in [1].

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Figure 6 ─ Sensitivity of brake specific fuel con-sumption with respect to changes in turbocharger efficiency

In addition to performance, the amount of savings achievable depends on fuel quality and fuel prices respectively. For a 1’000 kW high speed engine burning distillate fuel, a fuel consumption reduction of 1 g/kWh equates to circa USD 3,400 (680 USD/MT) over 5’000 running hours. For a 50 MW low speed engine burning heavy fuel oil, a fuel consumption reduction of 1 g/kWh amounts to USD 120,000 over 5,000 running hours (480 USD/MT). These figures indicate short pay-back times for high performance turbochargers.


REALISATION OF THE THERMODYNAMIC PERFORMANCE

Turbocharger performance

Compared to their predecessors the new A100-turbochargers provide higher compressor pressure ratios for the high and medium speed engine seg-ment and favourable performance in combination with higher pressure ratios for the low speed seg-ment. Figures 7 and 8 present the performance of the new generation in comparison to the previous product generation.

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series and previous turbocharger gen-eration in relation to volume flow

At around 0.5, the increase in compressor pressure ratio is same for all A100 series turbochargers (Fig-ure 7). For the low speed segment an increase in efficiency could be achieved,(Figure 8) as de-manded by engine requirements (Figure 4).

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The A100-H and TPS..-F are representative of the A100-M and the TPL..-C since they demonstrate only minor performance differences (Figure 8).

The particularly high efficiency requirements of low speed engines at part load made a complete new design of the turbocharger for low speed engines necessary: the A100-L.

The turbochargers for the high and medium speed engines are based on the well proven TPS and TPL platforms. The A100-H and A100-M series with radial turbine have the same flange measures as the TPS series. The rotating parts of the A100-H and A100-M were designed from scratch. The flow channels were subject to a re-design. The individ-ual design features are described in more detail in the following chapter “Design concept of the turbo-chargers”.

The increased performance requirements of the engines dictate not only turbochargers with higher performance but also demand very precise match-ing of the turbocharger to the engine. Three effects make this more challenging than in the past. Firstly, the high performance level requested of the com-pressors and turbines of the A100 series make operation either side of the design point less ac-ceptable, requiring specific compressor and turbine designs for the specific volume flow rates [2]. Sec-ondly the efficiency characteristics of the turbines and thirdly a higher sensitivity towards changes of flow area both require a finer stepping of turbine trims and nozzle rings. These three effects lead to “tailor made” products increasing the variety of parts to be developed, tested and stocked.

Compressor-stage

The pressure ratios of the A100 are achieved by using new developed compressor stages featuring further optimised impeller blading and new diffus-ers. For the A100-L the design of the air recircula-tor, already a field-proven feature of ABB’s TPS and TPL turbochargers has been optimised, as has the shape of the volute. The A100 turbochargers achieve their targeted pressure ratios using alu-minium alloy compressor wheels avoiding the use of expensive materials such as titanium. Compres-sor pressure ratios around 5.2 are achievable thanks to cooling of the compressor wheel. The cooling is realised via the established cooling air system, as already applied on TPL..-C turbocharg-ers. The slight performance loss due to the cooling air consumption of the turbocharger is acceptable on high and medium speed engines due to the high efficiency level of the new turbochargers. An addi-tional benefit of this material selection is the lower inertia of turbocharger rotors with aluminium com-pressor wheels compared to those with titanium compressor wheels. It is especially beneficial in power plant applications since they promote supe-rior load acceptance.


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Figure 9 ─ Compressor performance of the ABB A100-H and TPS..-F turbocharger series

Figure 9 shows the compressor performance of the new turbochargers for the high and medium speed segments in comparison to the current turbocharger generation.

A100-H and A100-M feature optional compressor cooling. Up to pressure ratios of approximately 5.2 no cooling of the compressor wheels is needed.

The level of this threshold depends on the load profile of the application, the compressor inlet tem-perature and on the targeted exchange interval of the compressor wheel. Up to the pressure ratio threshold mentioned, compressor efficiency is ap-proximately 1% higher than shown in the map Fig-ure 9 on the right side.

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Figure 10 ─ Compressor performance of the ABB A100-L and TPL..-B turbocharger series


The compressors of the A100-L turbocharger series achieve pressure ratios of at least 4.7 without cool-ing of the compressor wheel. This is important for the targeted applications on low speed engines due to the sensitivity of two-stroke engines to proper scavenging (Figure 10). The high peak efficiency of the A100-L compressor at part load is achievable due to the lower pressure ratio requirements com-pared to the A100-H and A100-M series.

The volume flow of the new turbochargers is main-tained at a high level compared to the turbocharger frame size by increasing the compressor wheel diameters relative to the size of the casings, in spite of the fact that the new compressors feature re-duced specific flow rates due to the higher com-pressor pressure ratios. The reduction in the flow rate follows the Rodgers-rule [3]. Figure 11 shows the trend of the technical development. However the absolute values of the compressor efficiency depend on the size of the specific compressor.

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Turbine-stage

Requirements for increased performance made specific demands on the design of the turbines for each area of application. The whole range of high speed engine applications and a part of the medium speed application range is covered by turbocharg-ers with radial turbines. The medium-speed range with large volume flows is covered by axial turbine turbochargers. Both turbine-types are qualified for pulse turbocharging with single gas entry inlet cas-ings, the qualifications for multi gas entry inlet are ongoing.

Special attention was paid to the mechanical design of the A100-H and A100-M due to the high circum-ferential rotor speeds needed for the high compres-sor pressure ratios. The turbochargers with radial-

turbine stages feature turbines with optimised tur-bine wheel blading. The turbochargers with axial turbine stages A100-M and A100-L are character-ised by their optimised gas inlet and gas outlet casings as well as the completely new design of their turbine stages. For the mechanically chal-lenging environment inherent to four-stroke engine applications and the high circumferential speeds concerned, a shrouded turbine concept was chosen (Figure 12). This concept allows higher turbine efficiency compared to the traditional damping wire concept.

Figure 12 ─ Turbine blades with shroud

Figure 13 shows the impact of a finer stepping of the turbine trims on turbine efficiency. The addi-tional trims enable 84% turbine efficiency over the relevant effective flow area range, from 39 to 73 cm2. Compared to the original stepping, minimal values increase 2.5%.

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Figure 13 ─ Improved turbine performance by means of finer stepping of the turbine trim


DESIGN CONCEPT OF THE TURBOCHARGERS

The design of the A100 turbocharger generation is based on the proven reliability and technical per-formance of the TPS and TPL turbocharger plat-forms.

Radial turbine turbochargers for four-stroke engines

The A100-H and A100-M series with radial turbines are derived from the TPS..-F series. Regardless of the conceptual origin of the TPS series design, analysis showed that almost all parts of the A100-H and A100-M needed adjustments to meet the higher thermodynamic and mechanical require-ments. The result of the redesign is a modular turbocharger combining a well-proven turbocharger concept with new design details and new technol-ogy. It features higher power density with identical flange measurements compared to the predecessor product (Figure 14).

Figure 14 ─ A100-H/M with radial turbine in the frame-size A140-H

Axial turbine turbochargers for four-stroke engines

The A100-M with axial turbine derives from the TPL..-C series (Figure 15) The all-embracing re-design of the TPL..-C was triggered by the higher thermodynamic and mechanical load requirements.

Figure 15 ─ A100-M with axial turbine in the frame-size A100-M65

Axial turbine type turbochargers for two-stroke engines

The A100-L series is a completely new develop-ment based on the TPL..-B experience (Fig-ures 16). The A100-L design incorporates TPL..-B field experience accumulated over hundreds of thousands of successfully completed running hours, to the benefit of reliability, service friendliness and operational safety.

Figure 16 ─ A100-L cut-away view


Bearings

Bearings are key to reliable turbocharger operation and long times between overhauls (TBOs). Due to the exceptionally good field experience with the concepts chosen for current turbochargers, design with plain bearings and squeeze film dampers were retained for all the three A100 series. A thrust bearing with floating disc was also retained for the turbochargers with axial turbines. For the A100-L another proven, but modified, feature taken from the TPL..-B is the lube oil tank, which is integrated into the bearing casing along with the mounting foot.

Casings

The higher charge air and exhaust gas pressures, as well as the larger kinetic energy of the rotating parts made reinforcement of the casings necessary. The modifications take account of thermo-mechani-cal stresses due to rapid changes in temperature when starting and stopping the engine, forces due to vibration, the stiffness needed to achieve high natural frequencies, rigid housings with sufficient fixing hole length to accommodate stretch bolts giving suitable pretension and, finally, containment of the rotating parts in case of excessive rotor over-speed. The channels and plenum needed for com-pressor cooling on the A100-H and A100-M series were integrated into the bearing casing and neighbouring parts without compromising compact dimensions compared to the current products.

Variable elements

ABB has longstanding experience with the suc-cessful use of variable elements on its turbocharg-ers. TPL and TPS turbochargers are available with variable turbine geometry (VTG) in certain frame sizes. VTG is fundamentally applicable to all ABB’s new turbochargers. The effective introduction of this feature on the A100-turbocharger generation will depend on market demand.

For the A100-L the market requested VTG for cer-tain frame-sizes at an early stage. ABB has thus already introduced VTG. The package includes the control unit, the actuator and the mechanical ele-ments. To facilitate rapid installation work and minimise cabling ABB has decided against stand alone control systems, i.e. the VTG control unit is mounted on the turbocharger itself (Figure 17).

Figure 17 ─ A100-L..T control unit and actuator of the VTG

The mechanical parts of the VTG are compact in design (Figure 18). The VTG turbochargers have identical flange measurements to turbochargers with fixed nozzle rings.

Figure 18 ─ A100-L..T mechanical part of the VTG


Service

For low speed marine applications the exchange intervals for the rotors and bearings of the A100-L turbochargers remain the same as for the TPL..-B generation in spite of their higher component load-ing.

Service friendliness was a key priority when devel-oping the A100. ABB’s service organisation offers endoscopic inspections of the turbine of the A100, thereby avoiding unnecessary dismantling for in-spection work and reducing downtime (Figure 19).

Figure 19 ─ Endoscopic inspections of the turbine stage

The choice of the turbocharger servicing concept is largely determined by the weight and the dimen-sions of the turbochargers and their components, as well as by material temperatures caused by the gas temperatures on the turbine inlet side. Turbo-chargers for low speed engines can be serviced from the gas inlet side because gas inlet tempera-ture does not exceed approximately 500 °C. At other engines, the first access to the turbocharger from the "hot" side is often not acceptable due to the high material temperatures. The service con-cept of the A100 series was based on these con-siderations.

Due to excellent experience in the field, the A100-M turbochargers for medium speed engines have an identical service concept as the TPS and TPL gen-eration. This concept allows the removal of the so-called cartridge, consisting of the rotor and directly related casings but without the gas inlet parts. Hence the hottest parts of the turbocharger remain on the engine. However, for the A100-H turbo-chargers installed on high speed engines, replace-ment of the whole turbocharger as a single unit is recommended due to the small size of these turbo-chargers.

Field experience with low-speed engines showed that in the overwhelming number of TPL..-B service operations the gas inlet casing of the turbochargers was removed. The service concept of the A100-L takes account of this experience. An advantage of the new design is that service can be carried out without having to remove insulation, notably reduc-ing downtime (Figure 20). Ship operators also benefit from a service concept recently introduced for TPL..-B turbochargers; exchange intervals of 36000 running hours have been retained for all A100-L turbochargers.

Figure 20 ─ A100-L gas inlet casing with nozzle ring and insulation standing on feet

FIELD EXPERIENCE

A100-turbochargers are subject to the standard ABB in-house qualification processes as a prereq-uisite for their release as new products. However the final proof of reliability is acquired on the engine in the field.

Several engine builders have tested the A100-H and A100-M radial turbochargers in extensive vali-dation trials (for example on the MWM TCG2032V16 gas engine, see Figure 21). Both thermodynamic and endurance tests formed parts of the test programs. During the endurance tests the new turbochargers were operated for about 500 running hours or more. The A100-H and A100-M radial turbochargers achieved pressure ratios of 5.6 on laboratory and field engines during their quali-fication process.


Figure 21 ─ 2 A140-H66 on MWM TCG2032V16 well covered from the insulation

After the tests the turbochargers were thoroughly inspected. In all cases the bearings were found to be in excellent or even pristine condition. Even after several hot shutdown tests and black starts, the bearings were fully functional. Figure 22 shows as an example the condition of a thrust bearing after a black start test.

Figure 22 ─ Thrust bearing after black start test

The plenum and channel for compressor cooling were without exception found to be in a clean con-dition with no signs of clogging detected. This result underlines the high reliability of the chosen com-pressor cooling method and confirms favourable experience with the application of cooling gained on the TPL turbocharger platform. Air cooled TPL..-A turbochargers have been operating for many years on passenger ferries in the Mediterranean as pilot applications and more than 250 air cooled TPL..-C units have been delivered yet.

During operation at high inlet temperatures atten-tion was turned to signs of oil carbonizing on the bearing casings, but even under extreme conditions no traces which might affect the good functioning of the turbocharger were observed.

On one application the intensive prototype testing revealed the need for an improvement in the turbine end shaft sealing. The necessary design improve-ments were executed, qualified and introduced before the new turbocharger generation’s release for serial production and have, in the meantime proven themselves. On the basis of findings ABB is expanding the internal qualification test procedure to cover issues of this kind for further turbocharger generations. This example emphasises the impor-tance of an early and intensive collaboration be-tween the engine builder and the turbochargers manufacturer. Such close bonds supported the development of the A100 turbocharger generation from the very beginning.

At the beginning of 2010 more than 400 of the A100-H and A100-M radial turbochargers were already delivered or on order.

Worldwide, some 10 engine builders are applying or testing the new radial turbocharger generation, which is available in four different frame sizes. The first units have all logged 4,000 running hours in commercial operation. For example, immediately following the production release of the A100 gen-eration, Rolls-Royce Marine AS / Engines-Bergen equipped their C25:33L6 with the A140-M65 (Fig-ure 23).

Figure 23 ─ A140-M65 on Rolls-Royce C25:33L6

With regard to the A100-L, ABB has gained field experience based on several thousand operating hours with the A175-L..T. To date both the turbo-charger itself and its VTG components have given problem free performance. At the beginning of


2010, A100-L orders totalled more than 1 GW of supercharged engine power.

Figure 24 ─ Engine with A175-L on the test-bed

CONCLUSIONS

ABB has introduced the A100 turbocharger genera-tion as a means of enabling the customers to meet the IMO Tier II emissions legislation using primary methods of emission reduction. These new, stricter emission regimes require higher air receiver pres-sures and higher turbocharging efficiencies for all engine types. The A100-H and A100-M are de-signed for high charge air pressures; they achieve compressor pressure ratios of up to 5.8. The A100-L is designed for high efficiency, particularly at part load; it achieves turbocharger efficiencies of up to 75% and compressor pressure ratios of at least 4.7.

The A100 series achieve improvements in perform-ance to an extent which allows a wide margin of compliance with the emissions regimes. Addition-ally they enable more powerful engines and lower fuel consumption. Low fuel consumption is neces-sary not only as a means of minimising lifecycle costs but also for reducing emissions of the green-house gas carbon dioxide (CO2). The application of A100 turbochargers thus results in considerable economic and environmental benefits: For example, on a 50 MW low speed diesel engine burning heavy fuel oil, the A100-L is capable of enabling fuel sav-ings of up 500 t, equating to financial savings of up to USD 250,000 over 5,000 operating hours.

The A100 is based on the well proven design and technology of the TPS and TPL platform, retaining time-tested design features wherever applicable and introducing new concepts when beneficial. The new concepts of the radial turbine versions of the A100-H and A100-M series and the concept of the A100-L series have already been validated under commercial operating conditions over several thou-sand operating hours.

NOMENCLATURE

EGR Exhaust gas recirculation SCR Selective catalytic reaction VTG Variable turbine geometry bsfc Brake specific fuel consumption pRec Air receiver pressure ηTC Turbocharger efficiency πC Compressor pressure ratio

ACKNOWLEDGEMENTS

The authors wish to thank Mr. Daniel Brand and Mr. Andriu Bonnevie for their contributions to this pa-per.

REFERENCES

[1] Codan, E. and Mathey, Ch., “2-Stage Turbocharging – Flexibility for Engine Op-timisation”, CIMAC 2010

[2] Gwehenberger, T., et al., ”Single-Stage High-Pressure Turbocharging”, Proceed-ings of ASME Turbo Expo 2009

[3] Rodgers, C., “The Efficiencies of Single Stage Centrifugal Compressors for Aircraft Applications”, ASME Paper no. 91-GT-77, 1991

BIBLIOGRAPHY

HANDBUCH DIESELMOTOREN, Klaus Mollen-hauer (Hrsg.), Springer 1997

Authors: Peter Neuenschwander, Dr. sc. techn. ABB Turbo Systems Ltd Product Line Large Turbochargers ZTT-L1 Bruggerstrasse 71a, P.O. Box CH-5401 Baden/Switzerland Martin Thiele, Dr.-Ing. ABB Turbo Systems Ltd Product Line Radial Turbochargers ZTT-R Bruggerstrasse 71a, P.O. Box CH-5401 Baden/Switzerland Martin Seiler, Dipl.-Ing. ABB Turbo Systems Ltd R&D Turbochargers Bruggerstrasse 71a, P.O. Box CH-5401 Baden/Switzerland

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