Comments from the LeadershipTeam – Steve Caddy

EditorialEditor: Alison Smith Editorial Team: Jodie Stephenson, Owen Ryder, Melanie Summers, Kirsty Needham, Rebecca Barron, Sara Hill. Freelance Copywriter: Alan Bunting E-mail: turbo.enquiries@holset.com

HTi is the Holset magazine focusing on the world of heavy-duty turbocharging. It aims to bring you news on product and market developments.

HTi is produced using an environmentally approved printing process and is printed on fully recyclable and biodegradable paper.

Copyright © 2005 Holset Engineering Company Ltd. All rights reserved. Holset®, VGT™, Command Valve™ and Super MWE™ are trademarks of Holset Engineering Company Ltd.

Holset continues to increase its share of agrowing global market for turbochargers.Unprecedented sales growth and customerdemand for new and established productshas led to a new facility being built atCharleston, South Carolina in the USA. This builds on our expansion at Dewas,India, earlier this year and the opening ofour new facility in Wuxi, China, in 2004.

Key to our success has been Holset’s focuson the mid-range and heavy-duty dieselmarkets and the specific technologiesdemanded in those applications. Lookingtowards the end of the decade andbeyond, we are committed to ensuringthat Holset will be ready with turbochargertechnologies matching the ever moreadvanced, fuel efficient, low emissiondiesel engines now being developedthroughout the world.

Engine refinements addressing each newcycle of emissions legislation are becomingprogressively more sophisticated. We havealready seen the successful introduction ofvariable geometry turbocharging (VGT™)to meet Euro 3 and in North America, EPA ’02/’04 on-highway emission laws.Holset’s R&D teams have moved on to ournew product Value Package Introduction(VPI) programmes to introduce further newtechnologies for Euro 4 and EPA ’07requirements.

We are already working with all our enginemanufacturer customers on thedevelopment of technologies able to meetthe exceptionally demanding emissionlimits proposed or expected by 2010 andbeyond. Prototype Holset turbochargerinstallations are already under evaluationwith customers.

Ever more severe exhaust emission limits,together with different demands fromspecific markets, will inevitably lead us togreater product diversity in the future; thiswill require both customer and marketdedicated solutions, implying a broaderproduct range. This in turn will bring thechallenge of how we support such productdiversity whilst ensuring robust productdesign. Here a vital tool in our strategy isan increasing use of Design for Six Sigma(DFSS) in our product developmentmethodology.

Holset has stepped up its commitment toDFSS over the past 12 months and we willcontinue with further training of all ourengineers until DFSS becomes thepreferred way in which we undertake allnew product design and development.

In order to provide the customer withtechnologies to meet their designsolutions, Holset increased its engineeringstaff in its worldwide technical centre inthe UK by nearly a third in 2004 and wecontinue to recruit through the business in2005.

My colleagues and I are excited by thechallenges and opportunities we face inthe future. With ever greater globalisationof the engine business, we are committedto increasing our understanding of the keyissues facing our customers, most notablytheir drive to control emissions withoutcompromising fuel economy. Holset isdetermined to work ever more closely withits customers to achieve our mutual goals.

Steve CaddyTechnical Director

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Steve CaddyTechnical Director

New Charleston PlantStrengthens Holset in the USAWritten by Jodie Stephenson, Worldwide Marketing Communications Leader

Holset is further expanding its operations inthe USA. Plans have been announced toestablish a new $13 million (USD) plant inCharleston, South Carolina. It carries forwardthe company’s corporate business strategy ofexpanding production capacity in key marketsto meet the growing global demand forturbochargers. It builds on Holset’s expansionat Dewas, India earlier this year and theopening of the new facility in Wuxi, China in2004.

After a detailed review of many potentialsites across the world, Charleston waschosen for a variety of strategic reasons, notleast its geographical proximity to the vitalNorth American diesel engine market. Thenew facility will be situated in PalmettoCommerce Park, 14 miles (22.5 km) fromHolset’s existing Charleston plant and whilst it will interact closely with the existingCharleston operation, the new plant will berun as a stand alone facility.

Over 180 new employment opportunities willbe created and the plant will expand Holset’scapacity by 200,000 units per annum whilstproviding space for further growth.

Heading up the venture in Charleston will beBrian Keighley, formerly General Manager ofHolset’s Wuxi joint venture in China. The newUSA plant will focus on manufacturingHolset’s latest technology VGTTM product,providing turbochargers for both USA andother global markets. Construction of the newfacility commenced in May 2005 andproduction start up is scheduled for the thirdquarter of 2006.

Holset’s declared policy is tocontinue to expand itsworldwide manufacturingcapacity to meet the growingglobal demand for dieselengine turbochargers. The USAis a key resource base for thecompany.

On-going investment will helpto consolidate Holset’sposition as one of the world’stechnology leaders in theincreasingly specialised field ofturbocharger development.

Evidence of that continued investment andexpansion came with the opening earlier thisyear of Holset’s regional office in Shanghai,China, which has created a base for customeraccount teams to provide closer contact withthe company’s engine manufacturercustomers in the Asia region. In a similarmove, Holset has also opened an office inPune to serve the increasingly importantIndian diesel engine industry, whilst alsosupporting Holset’s wider global operations.

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Holset regional office in Shanghai, China, which is shared with one of our sister companies.

Artist impression of the new Charleston facility

The prime aim of a turbocharger is toincrease the air density in the engine.This allows the efficient combustion of more fuel, leading to higher poweroutputs, crucially without increasing the engine’s swept volume.

To increase the air density, the waste exhaust gasis used to spin a turbine wheel, which in turnrevolves a compressor wheel via a connectingshaft. The turbine/compressor wheel assembly is often referred to as the rotor. The compressorcreates the raised charge air density that is fed to the cylinders via the inlet manifold.

When we need to design a compressor wheel for a new customer application, expand therange of applications that an existing componentcan cover or develop new technology for futureapplications, the Holset facilities around theworld are ideally configured to carry out this test work.

The performance characteristics of a compressor are defined in a performance map, which ismeasured on a test cell. The following articledescribes the map and test methods used at Holset.

A Compressor Wheel Performance MapFigure 1 shows a typical compressor wheel mapproduced from a test cell.

The centre portion of the map or ‘Heart’ withinthe innermost contour line is the area where the turbocharger is working at its peak efficiency.This is the ideal operating region. Moving awayfrom this region reduces compressor efficiencywith a likelihood of unstable running in extreme conditions.

‘Surge’ is an undesirable phenomenon to the leftof the map, where the flow of air through thecompressor becomes highly unstable. It occurswhen the air flow through the compressor is lowwhile the back pressure is high and can lead tothe compressor wheel momentarily stalling as itattempts to pump the air against a higherdownstream pressure. The point at which surgeoccurs can be calculated by the test cellcomputer, enabling surge to be defined inpercentage terms as a specified pressurefluctuation worse than that seen during normalflow conditions.

‘Choke’ is a characteristic occurring to the rightof the map, where the air flow is high andmoving close to the speed of sound. Whenconditions move into this region, there is a rapid drop in compressor efficiency. Theconstant speed lines become nearly vertical tothe right of the choke line, indicating that a slight increase in mass flow will result in anundesirable and rapid decrease in pressure ratio.Choked operation of the compressor leads togross inefficiency and should be avoided.

‘Excess rotor speed’ is a condition that must be avoided. As the speed of the rotor increases,centrifugal forces and mechanical stresses increaseto a point where the wheel may ‘burst’, suffering a catastrophic mechanical failure. The wheel is notto be run above this design speed and is oftenoperated at a pre-determined percentage of thisspeed giving a margin of safety.

‘Efficiency contours’ are lines showing areas ofconstant efficiency. They are also re-plotted ascurves in the upper graph so it is possible to seethe efficiency of the compressor at any particularcombination of flow rate and speed parameter.There is one curve per speed line.

The results obtained from Holset test cells around theworld are directly comparablewith each other due to the waythey are mapped.

Test Cell ConfigurationThe test cells created by Holset are designed to bemodular ensuring consistency worldwide. Each isdesigned, installed and commissioned to tried andtested methods. These designs are based on in-house knowledge, experience and also meetnational and international standards. Thesestandards include BS EN ISO 5167:2003, formerlyBS1042 Measurement of Flow in Closed Conduits,Dangerous Substances and Explosive AtmospheresRegulations 2002 and many more equipment,health, safety, performance and environmentalstandards. In line with continuous improvementpractices, there is also a rolling programme ofupgrades to bring older facilities up to the latestspecifications and capabilities. Each cell issubjected to a regular measuring instrumentationcalibration. As test programmes are carried out onthe cells, base turbocharger units are used toprovide before, during and after performancecomparisons to ensure repeatability. 6 Sigmastatistical methods are used to monitor these baseturbocharger tests and they provide acomplimentary early warning system that canindicate small fluctuations in the cell’s performance,which can be corrected before larger issues arise.

The results obtained from Holset test cells around the world are directly comparable with each other due to the way they are mapped. Each set of resultsis normalised to account for differences in ambienttemperature and pressure. Corporate units ofmeasurement are used so that once a performancemap has been created and plotted, Holset orcustomer engineers at any location can read andinterpret the results.

Figure 2 shows a typical test cell layout to enablecompressor mapping. The turbocharger is held inposition by the normal bolted joint at its turbine inletflange. V-bands are typically used to support the otherconnections; turbine exhaust, compressor inlet andcompressor outlet, also known as boost. Thecompressor inlet is connected to the plenum chambervia a horn or flow nozzle (shown in red), which allowsthe inlet air flow rate to be calculated from pressuremeasurements. On the compressor outlet pipe,temperature and pressure measurements are takenenabling pressure ratios and efficiencies to becalculated. The turbine side of the turbocharger isdriven by hot gas from a diesel fuel combustor,typically controlled to 600°C. This then drives thecompressor wheel to the required running conditionsso that the compressor performance can be evaluated.

Mapping Performance TestingBefore the start of each test, the programmeengineer specifies the range of turbochargerrunning speeds to be investigated. In compressormapping, the maximum design speed is neverexceeded for safety reasons. Once the surge pointhas been found for a given rotational speed andpressure ratio, the flow through the compressor isincreased by slowly opening a valve in thecompressor outlet piping. Computer controlled testsystems calculate the running conditions that give60% compressor efficiency (defined as the chokepoint) and then hold the conditions steady to allowsnapshot readings to be taken of all theinstrumentation channels. Once the pressure ratiosand flow rates are known for surge and chokeconditions, the computer calculates severalintermediate points. The boost valve is then closedto these intermediate flows in order to obtainadditional measurement points. Instrumentationreadings are electronically taken at each of thesepoints once conditions have become stable, thus a constant speed parameter ‘running line’ iscreated. The procedure will then be repeated foreach of the remaining test speeds to produce thegraph as shown in figure 1.

Different compressors, differentapplications…Many factors can influence the performance of a compressor and the map is used to investigatesuch criteria. Some compressors are designed toprovide ‘narrow’ performance bands, typically forstationary, single-speed engines. Othercompressors, notably for applications where thereare large fluctuations in engine speed and load aredesigned to have an appropriately ‘wider’ map. This gives more flexibility over a range of flow,pressure and speed conditions; it is thereforepossible to apply one frame size of turbocharger to many engines from a single manufacturer.

For further information on some of the technologiesused to create these wider maps, see edition 4 ofHTi where Super Map Width Enhancement (SuperMWE™) is discussed.

Compressor PerformanceMapping Written by Andrew Pell, Senior Mechanical Facilities Engineer

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Fig 1 - Compressor Performance MapFig 2 - A compressor mapping cell layout

Reasons for China’s development arehowever more complex than the abundanceof consumers, cheap land and relatively lowlabour costs. Recent changes in governmentsupport aimed at accelerating reform arealleviating the government debt burdenallowing more opportunities for growth.New technology and investment fromoutside the country as well as productimports are transforming the commercialscene in China since the policy of openingup and reform was adopted.

Many observers see automotive manufacturebecoming one of the backbone industriesaround which the Chinese economy willgrow. It is already playing a key role in thecountry’s development and helping to raisethe standard of living for significant sectionsof the population. Since the first mid-rangetruck rolled off the First Auto Works (FAW)production line in Changchin in 1956, theindustry has grown, gaining hugemomentum in the last decade.

Changes in the Chinese MarketWritten by Kirsty Needham, Marketing Assistant

In 1999, the total Chinese output of road vehicleswas more than 1.8 million units covering morethan 150 basic automotive types including trucks,tippers and tractors as well as cars and dualpurpose vehicles. By 2004, output had grownnearly threefold, to 5.2 million, itself a 14%increase on the 2003 figure of 4.6 million. Trucksnow account for more than half of the total figure;nearly all powered by diesel engines, the majorityof these are now turbocharged.

Last year Wuxi Holset, Holset's joint ventureoperation with Wuxi Diesel increased its productionby 50% over the 2003 total. The Chinese plantcurrently manufactures HX35, HX40, HX50 and HX55turbocharger models. Wuxi Holset supplies theChinese domestic market as well as meeting demandfrom overseas.

Chen Hua, Wuxi Holset’s Deputy General Manager,sees the drive towards quality excellence as a majorfactor in the growth of the company. He commented,“We have put a lot of emphasis on making sure thatour quality levels are high, which has ensured healthysales in China as well as in export markets as well.”In a country where the quality of finished goods hassometimes been regarded as inferior to foreignproduced items, he points to a series of qualityawards that the company has won from variouscustomers including Dalian Diesel, Wuxi Diesel, YulinDiesel and the Jiangsu Government. In 2004 the plantalso won the Holset Worldwide Quality Award.

There are plans to increase export sales from WuxiHolset considerably in coming years. In 2003 thecompany exported just 5% of its total production and10% in 2004. However, it is estimated that this willrise markedly to 30% in 2005.

With a 26% market share for Wuxi Holset of theChinese heavy-duty turbocharger market last year,there is anticipation of a more intense battle forcustomers in the future. Chen Hua commented,“There is perhaps just one major competitor in Chinaat the moment but in the future there will be manymore international players fighting for turbochargerbusiness and some have major investment plans.

That’s why we have such a commitment to quality.There are exciting prospects for us, especially if you look at the number of new engine makerscoming into China. Their arrival offers greatopportunities for us.”

He added that the company is also planning amajor promotion of its capabilities in China. “I really want to promote the Holset Turbochargerbrand more widely in China. In the past we havejust focused on our capacity but we need now toimprove brand awareness and to promote ourmarket leadership in the mid-range to heavy-dutysegment and the fact that our leading position hasbeen driven by focused technology.”

Reinforcing the Holset Turbochargers brand hasnever been more important than in today’sincreasingly competitive market. Counterfeit orpirate turbocharger components of inferior quality,which are potentially dangerous, are becoming anincreasing problem in China. Holset is taking stepsthrough its marketing strategies to restrict theactivities of such copiers. The company is alreadypursuing legal opposition to a company in Chinatrying to register a trade mark bearing markedsimilarities to the previous Wuxi Holset companylogo. “With the help of Holset UK, Wuxi Holset andWuxi Diesel we have a very strong case of stoppingsuch action”, assures Chen Hua.

Awareness of intellectual property rights isrelatively new in China. However, it is of everincreasing importance and not just for Holset. There are many companies now operating in Chinathat are focusing on technology as well asmanufacturing. As a result they are protecting theirproducts through the use of trade marks, patentsand copyrights. It is estimated that annual globallosses from counterfeiting now amount to over$350 billion (USD). It is not just multi-nationalcompanies who are adversely affected through thegrowth of counterfeit products, which can be andoften are hazardous to the innocent end user aswell as jeopardising product performance, reliabilityand durability. In the past China has been criticisedfor the poor enforcement of intellectual propertyrights, however, this is thankfully changing.Education, technology transfer and licensing are all providing a platform, which may help reducecounterfeiting activities in the long term.

Holset is committed to taking serious legal actionagainst those involved in the violation of trademarks and copyrights of Holset Turbochargers orthe distribution of ‘pirate’ product. The launch ofHolset’s ‘Insist on Genuine’ marketingcommunications campaign is already underway andthere are plans to intensify our activities againstthe copiers in the coming financial year.

China Country Fact File 2004

Population 1,298,847,624Per Capita GDP (PPP) $5,000GDP Growth Rate 9.1%Total Automotive Sales 2004 5,173,003

(2,328,237)*

Total Automotive 5,164,294Production 2004 (2,318,753)*

Market Growth 2003 vs 2002 39.3% (72.7%)*Market Growth 2004 vs 2003 16.0% (14.4%)*

Best sold model PC Volkswagen Santanasegment 2004 (9.6%)

Best sold model LCV Chang’ an Carrysegment 2004 (15.0%)

* = passenger cars

Source: Segment Y Automotive Intelligence onemerging market. www.segmenty.com/China

There are plans to increase exportsales from Wuxi Holsetconsiderably in coming years.

Since China moved away from a centrally planned and controlled economy and became a fullmember of the World Trade Organization (WTO), the huge potential of the Chinese market has become apparent. With more than 1.3 billion people looking to buy, sell, manufacture and consume, the opportunities in trade, both import and export, retail and wholesale, as well as investment, support services and of course manufacturing are clearly immense.

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Image courtesy of DFM

Image courtesy of FAW

Integrating an electric motor/generatorinto the rotor of a turbocharger, as ameans of augmenting boost at lowerengine speeds, is an attractive solutionto what has been perceived as aturbocharger shortcoming.

The electric machine can be incorporated within thebearing housing between the compressor andturbine wheels. Holset’s project work on theconcept has been undertaken as part of theELectric Exhaust Gas Turbocharger (ELEGT) project,which has been partly funded by the EuropeanCommission. Holset’s partners in the project wereDurham University in the UK, Iveco in Italy andSwitzerland, ATE in Germany for electrical machinesand Thien in Austria for electronics.

Electrically assisted turbochargers are worthy ofinvestigation because they can:

Increase boost pressure at low engine speedswhere exhaust flow available to drive theturbine is limited; electrical power from thevehicle’s battery can be harnessed to drive theturbocharger to higher speeds.

Maintain turbocharger speed during gearshifts,when engine revs typically fall away; electricalpower can augment the work done by the turbine.

Reduce turbocharger speed under high enginepower conditions, using the electrical machineto apply a restraining torque to that exerted bythe turbine.

Recover exhaust energy that would otherwisebe wasted, by using the electrical machine ingenerator mode, converting excess shaft powerto electrical power for battery charging andperhaps eventually eliminating the need for aseparate alternator.

Vehicles in the future are expected to havenumerous auxiliaries, which today are mechanicallydriven by gears or belts but will then be electricmotor driven on a much more efficient power ondemand basis. Excess exhaust energy may be usedto generate the additional electrical power requiredon a vehicle to drive such auxiliaries.

A further role for the electrically boostedturbochargers might also be found in a hybridpowertrain. The turbocharger's electrical machinecould supply power to an integrated starteralternator damper (ISAD) mounted on the engine'sdrive shaft, supplementing the engine's output likea turbocompound installation, but with an electricalrather than a mechanical connection (see figure 1).

An analysis of typical turbocharger shaft torque andspeed (see figure 2) provided a logical startingpoint for the ELEGT investigations. Shaft torquevaries between about 1Nm when the turbocharger isaccelerating and minus 1.5Nm when it isdecelerating. Clearly, if the electrical machine couldadd an additional 1Nm accelerating torque, thenboost pressure would be significantly enhanced atlow engine speeds. An electrical generatingrequirement of 7.6kW was set, based on the typicalexcess exhaust power available for ‘recycling’ athigh engine speeds (see figure 3).

Giving turbochargers an electrical boost Written by Jeff Carter, Consulting Engineer

For the electrical machine to survive in the extremetemperatures and high vibrations of a turbochargerenvironment while meeting severe durabilityrequirements, the electrical machine needed to bevery robust. A number of different electrical machinetypes were reviewed: permanent-magnet, switchedreluctance and induction (asynchronous). The induction machine was chosen primarily for itsrobustness; it can also tolerate the large rotor tostator air gap required by a turbocharger shaft’sfloating bearing system. It is also a relatively lowcost type of electrical machine.

Most induction machines have a rotor formed of astack of silicon-iron laminations to carry themagnetic flux and bars running through slots in thelamination stack to carry the electrical current. Thebars are joined at each end of the lamination stackby end rings. In small electrical machines it is usualto use aluminium for the bars and end rings.However, because of the high rotor temperature, the ELEGT machine was deemed to require castcopper conductors.

Figure 4 shows the Mk 1 ELEGT machine partiallydismantled, from left to right: bearing housing,stator, rotor, bearing housing end cap and turbinewheel. Figure 5 shows the cross sectioned threedimensional model.

Testing of the Mk1 machine in Holset’s UK technicalcentre at Huddersfield showed that the shaft motionof the system was acceptable and that thetemperature of the bearing housing conformed tofinite element analysis predictions. However, it wasfound that when the coils of the motor/generator

were energised, their temperature rose rapidly to thelimit of the coil potting material. A Mk2 design (seefigure 6) was accordingly developed with deeperstator slots, allowing a bigger winding with lowerelectrical resistance. Also the winding pottingmaterial was changed to increase its temperaturetolerance, while the coolant circuit within theturbocharger was re-routed to bring the coolantcloser to the surface of the motor/generator.

Complementing the test work at Huddersfield,Durham University is undertaking other ELEGTdevelopment work, notably investigating the ‘solidrotor’ machine, where the rotor of themotor/generator is formed of a simple cylinder ofhomogeneous material, replacing the laminationstack, bars and end-rings. The material used for therotor has to be able to carry both magnetic flux andelectrical current. Surprisingly, common mild steelwas found to be quite suitable, although othermaterials are also being investigated. It is hoped thesolid rotor design will make the machine even morerobust, simplify assembly and reduce costs. Holsethas submitted a patent application for this design.

Finally, computer modelling of the system has beencarried out both at Durham University and at Holset,to determine what level of fuel savings could bebrought about by using the generating capability of the ELEGT machine. Depending on a number of factors including vehicle duty cycle and electricalload, fuel savings of approximately 5% are predicted(figure 7).

•

•

•

Larger statordiameter- deeper slots,

lower windingresistance

Coolant closerto statorsurface.

Improved motormaterials

Fig 6 - MK2 ELEGT Machine

Water inWiring

Oil in

Stator RotorWater

out

Fig 4 - Turbocharger – Motor Assembly

Fig 5 - Turbocharger Integration – Mk1 Squirrel-Cage Machine

Fig 7 - Example Results of Fuel Savings

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Engine

ControlSystem

EnergyStorage

ElectricTurbo

OtherElectrical

Loads

Efficiency Benefits

Drive shaft

No longerparasitic

loads

PASCooling Fan

Air CompressorWater Pump

Oil PumpA/C

ISAD or Hybrid Drive Train

Fig 1 - Integrated Electrical System

Fig 2 - Typical Turbocharger Operation

Fig 3 - Electrical Machine Outline Specification

The ELEGT project is financially supported by the European Commission’s GROWTH Programme, as Contract 63083 Project G3RD-CT-2002-00788

This article has been adapted from a paperpresented earlier this year by Jeff Carter entitled ‘The development of turbocharger acceleratormotors and drives and their integration into vehicleelectrical systems’, at the Institution of ElectricalEngineers’ first Automotive Conference in Londonattended by 175 delegates. It was co-authored byDr. Jim Bumby, Prof. Ed Spooner and Dr. SueCrossland of Durham University.

Jeff Carter obtained a BEng in Electronic and ControlEngineering from the University of Birmingham. He later returned to the university as a researchassociate and completed a PhD, titled ‘A Study of the Single-Phase Three-Level PWM Converter’,relating to electrical power conversion for railwaylocomotives.

He started work at Holset in 1996 as a SeniorDevelopment Engineer and is currently a ConsultingEngineer, working on various aspects of sensors,control systems, dynamicmodelling, electricactuators and the highspeed electrical machinesrequired for the ELEGTproject.

A high-speed pyrometry system prototype, designedfor operation at temperatures between 70 and 280°C was developed at the Technical University, Berlin andoperated in one of Holset’s turbocharger test cells atHuddersfield in the UK.

In recent years the demand for ever higher specific outputs, or powerdensities has led to an inevitable requirement for progressivelygreater boost pressures in turbocharged diesel engines. As a result,creep and fatigue due to thermal and mechanical stresses on theimpeller are posing more severe challenges for impeller designers.More detailed stress analyses are required in strategies aimed atachieving the necessary impeller strength and component durability.For a computer based finite element model to be sufficiently precise,detailed and accurate boundary conditions must be included in theinput data. Usually such data is supplied by computational fluiddynamic (CFD) simulation results. Significant uncertainty neverthelessremains about the temperature distribution in the impeller.

Ideally, surface as well as internal temperatures in the impellermaterial need to be measured accurately. As the component rotatesat high speeds, measurement of metal temperatures is notstraightforward. Several approaches using embedded thermocoupleshave been tried at Holset. Whilst useful data was acquired near theimpeller hub, it proved difficult to obtain reliable temperaturereadings towards the outside diameter of the impeller.

It seemed that a promising solution would be remote sensing of the temperatures, using an infrared pyrometry technique. The Technical University in Berlin had previously developed such asystem for high speed, high resolution temperature measurements on blades of industrial gas turbines. It was suggested thatapplication of that experience could be used to develop a pyrometrytechnique suitable for the lower temperatures of impellers. It neededto be capable of providing the accurate temperature readingsrequired for creep calculations as well as for calibrating CFD modelswith improved accuracy.

Design of the Pyrometry SystemFor turbocharger machinery pyrometry systems, it is necessary to usea small probe to gain access to the blades. The radiation is thentransferred to the detector using a light guide. Such a configurationallows the sensitive detector and the data acquisition electronics tobe protected from the harsh environment. Figure 1 shows such atypical setup for a turbine pyrometer.

Measurements in a Turbocharger Test CellA prototype pyrometer was built, calibrated using a black bodyradiator. The pyrometer was set up in a Holset test cell on an HX82turbocharger. The impeller had been anodised with a black coatingin order to ensure low reflectivity. The pyrometer was installed at the back of the impeller for access reasons. Two thermocoupleswere also used to provide comparison readings with the pyrometerdata. One thermocouple measured the gas temperature just after the impeller, while the other monitored diffuser plate temperature. Figure 2 shows the experimental installation.

LOW TEMPERATURE, HIGH SPEED PYROMETRYMEASUREMENTS ON A TURBOCHARGER IMPELLERWritten by Mike Eastwood, Principal Engineer

Figure 3 shows the measured gas and detector temperatures over time, which matched quite well except for the first 25 minutes while equilibrium wasbeing reached.

It was originally expected that the pyrometer would show a constanttemperature for a constant speed but some slight variations in temperaturecould be seen in the signal, see figure 4. When synchronising the temperaturevariations with the revolutions of the turbocharger, it became clear that thevariations correlated with the 16 blades and balance groove. A difference ofonly 7°C between minimum and maximum temperature can be crucial indetermining the creep behaviour at high operating temperatures. Although unexpected, it was valuable and instructive to see how the heatconduction in the impeller influenced the temperature distribution on the back of the impeller.

Numerical Calculations In order to understand the apparent dynamic temperature variations observedby the pyrometry measurements shown in figure 4, a three dimensional finiteelement analysis of the compressor wheel was undertaken. This gave theexpectation of gaining back face temperature predictions that could be used tocompare and allow calibration of the dynamic pyrometry voltage output.

A complete impeller finite element model was used to predict temperaturedistribution and compare those predictions with the pyrometry measurements.Only one full impeller finite element model was available and unfortunately itwas not the HX82 impeller as tested. So the existing model was scaled up toHX82 outer diameter size. The main differences between the finite elementmodelled impeller and that used for test was the existence of two balancegrooves on the back face instead of one and 14 blades rather than 16 blades.The two balance grooves were diametrically opposite each other as can beseen in Figure 5.

Figure 6 shows a plot of temperature distribution along a line of constantradius on the impeller back face. The plot’s two large peaks coincide with thebalance groove positions and 14 troughs line up with the 14 blades on theimpeller. The predicted temperature variation seen on the back face of thecompressor is caused by the heat transferred between the back face and theblades on the front side of the disc. In the location of the balance groove, theback face disc is significantly thinner, which accounts for the highertemperatures in that area. Each balance groove coincides fully with two bladesand the two higher temperature troughs.

The overall temperature decrease at blade locations was 2°C whilst an increaseof 5°C was seen at balance grooves. Comparing the temperature variations with those from measurements in figure 4 it can be seen that they are ofsimilar magnitude, helping to validate the very high speed resolution capability of the pyrometry technique.

Using the new pyrometry system for high speed, low temperaturemeasurements on turbocharger impellers, based on a prototype system testedon a Holset turbocharger compressor in a test cell, it was possible to measurethe different heat conduction conditions in the impeller. The results weresupported by a finite element analysis of boundary conditions from statictemperature measurements. Unexpected variations in the temperature signalsfrom the pyrometry system were found not to be caused by spurious signals in the prototype system.

Using the new pyrometry system, it is possible tomeasure the different heat conduction conditions in the impeller.

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Fig 1 - Setup of a typical turbine pyrometry system

th

23 5

2 3 5 .5

2 36

2 36.5

2 37

2 37.5

2 38

2 38.5

2 39

2 39.5

2 4 0

-2 0 0 -1 5 0 -1 0 0 -5 0 0 5 0 1 0 0 1 5 0 2 0 0

Angle (deg)

Temper

ature (de

g C)

TEMP

Blade Locations

ThermocouplesData logger

CT

OscilloscopeAmplifierDetectorLight guide

Fig 2 - Experimental pyrometer installation in thecompressor and the additional thermocouples

Fig 3 - Gas temperatures measured in the diffuser channeland impeller temperatures measured by the pyrometer

Fig 4 - Detected temperature variations over 2.4 revolutionsat an impeller speed of 70,000 rpm

Fig 6 - Temperature variations calculated using finite element analysis andboundary conditions from static measurements. The plot shows temperaturedistribution along a line of constant radius on the impeller back face

Fig 5 - Finite element model of impeller showing two balance grooves

Mike Eastwood, Principal Engineer at Holset, co-presented a paper on this topic at the 6th Turbomachinery Conference in Lille in March 2005. The five day conference was attended by around 300 delegates. Thank you also to Jonas Nickel of TU Berlin who worked on this project.

A graduate in Mechanical Engineering, Mikeworked as a stress engineer for David BrownTractors, British Aerospace, Williams FaireyEngineering and Rolls Royce Wellman Boothbefore joining Holset in 1994. He became aMember of the IMechE in 1993.

At Holset, Mike has worked in AppliedMechanics on stress analysis of mostcomponents and specialises in thermo-mechanical stress and fatigue analysis of turbine housings and creep analysis. He also chairs the Thermal Applications Limits forum.

Holset is piloting a new supply chainmanagement system using Wesupplysoftware. The decision to use Wesupplyand the resulting supply chain processarose from a 6 Sigma project aimed atimproving product deliveries to customers.

In pursuit of customer excellence, Holset iscommitted to continually reducing lead-times to our customers and have set out to streamlinecommunications, with the objective ofdisseminating information on a daily basis acrossthe whole supply chain.

At the same time we wanted to ensure theavailability of material in the supply chain to giveHolset suppliers, typically foundries and machiningcompanies, more flexibility and control of theirproduction and available capacity. Results from the6 Sigma project showed that the greatest impact onour customer delivery performance would comefrom improving the availability of ‘end housings’,that is compressor covers and turbine housings.The pilot scheme is accordingly being implementedacross our end housing supply chain, linkingfoundries, machinists and Holset through onegeneric system.

Wesupply is a web-based hosted supply chainmanagement solution designed to provide anumber of key benefits:

Demand information can be communicated daily, in a common format, across the supply chain.

Shortfalls can be identified proactively through exception based alerting, under such headings as: ‘Shipment overdue’, ‘Under-receipt’, ‘Forecast error’, ‘Stock below minimum’.

Material availability in the total pipeline, including in-transit consignments, is assessed.

A means of managing and maintaining consignment stock at all levels in the supply chain is provided, leading to a significant reduction in Holset’s own inventory.

Ready visibility of all stock transactions across the supply chain leads to improved inventory control.

Safety stock/Kanban levels needed to support Holset customers’ lead-times are dynamically recalculated and automatically adjusted.

Suppliers are given more flexibility and control of their production and available capacity, through defined tolerance bands.

Advanced Shipment Notification (ASN) information can be sent to and received by suppliers.

A common measurement system is provided tomeet agreed service level objectives. Alltransactions and information can be easilyintegrated within the suppliers’ own systems.

The Wesupply application has been configured tomanage inventory levels for castings and machinedparts categorised as ‘scheduled’, ‘Kanban’ and‘consignment’. The intention is to implement a pullprocess throughout the supply chain,

thereby reducing overall inventory while increasingHolset’s ability to react to customer requirements.

Suppliers at every point in the supply chain havereal-time access to their requirements from Holset,allowing them to react to changes more efficientlyand effectively.

Application of business rules within Wesupplyallows tight controls on inventory levels.

By the end of September 2005, the new supplychain control structure is expected to be fullyoperational for all component parts from six pilotsuppliers. A cross-functional senior managementteam is assessing the benefits of the pilot scheme,with the aim of determining a roll-out strategy forits wider implementation. If successful, furtherapplications of the scheme using the Wesupplysoftware are envisaged, including supplier capacitymonitoring and self-billing.

Wesupply’s Solutions Consulting Group Director,Andy Wood comments, “This project has been atremendous example of the benefits that can beachieved with a solution that enables all thetrading partners in the supply chain to workcollaboratively to meet a common goal.” TheWesupply project team is confident that this pilotimplementation will derive the expected benefits.

All transactions and informationcan be easily integrated within the suppliers’ own systems.

STREAMLINING THE SUPPLY CHAINWritten by Steve Fritchley, 6 Sigma Black Belt

For the first time, Holset exhibited at the2005 Goodwood Festival of Speed, heldin the UK. The Goodwood event is one ofthe world’s biggest and most diversecelebrations of the history of motorsport.Over three days some of the world’s mosthistorical and famous cars andmotorbikes are raced on the famousGoodwood circuit, with many more onstatic display. Holset showed theAmerican Dodge Ram 2500 Quad Cab 4x4SLT pick-up, powered by a 5.9 litreCummins 600 diesel engine and equippedwith a Holset HE351CW turbocharger.

The specially engineered turbochargerboosts the engine to deliver more powerand torque than the 2003 variant in asimilar high performance Ram pick-up,despite being the same turbocharger frameand rotor size. The new turbocharger isthe first production model from Holset to utilise the compressor cover mountedCommand Valve™ wastegate technology(see HTi edition 3).

Across the Atlantic, the annual Associationof Diesel Specialists (ADS) conventiontook place from 3 to 6 August in LasVegas, Nevada. The ADS is the dieselindustry’s leading trade association,dedicated to the highest level of serviceon diesel fuel injection and relatedsystems. Holset exhibits each year at theassociation’s four-day August convention.

Meanwhile Holset Brazil attended theannual Automech trade show event, heldin July at the convention centre inAnhembi, São Paulo. Over the four daysmore than 73,000 visitors attended. The exhibition gave Holset theopportunity to showcase its latestproduct technologies.

Holset turbochargers have been chosen by theIndian truck manufacturer Eicher Motors Ltd for itslatest 3.3 litre E483 light commercial vehicle (LCV)diesel engine, which meets the Euro 2 level exhaustemission standards now being demanded in India.

The contract with Eicher Motors marks a furtherstage in Holset’s business strategy of establishingtechnology partnerships with market leaders,especially in rapid-growth markets in thedeveloping world.

Eicher Motors, a part of the Eicher group, wasfounded in 1982 to manufacture and market 5to 25 tonne commercial vehicles. Itsmanufacturing facility is situated at Pithampur,in the province of Madhya Pradesh in centralIndia. In 1986, Eicher Motors entered into atechnical and financial collaboration withMitsubishi Motor Corporation of Japan tomanufacture the Canter range of vehicles. The technology transfer agreement withMitsubishi ended in 1994 and Eicher Motorstoday is one of the fastest growing players in

the LCV segment in India, with a 33% market sharein the 7 to 11 tonne segment and an 8% overallcommercial vehicle market share in India. Eicherhas more recently made advances into the heavytruck segment with locally designed and developedchassis.

In what has been a successful beginning to apromising business relationship, Holset has begunsupplying HX25W turbochargers for Eicher’s E483LCV engine. With the light truck model now inseries production, the Indian company is now welladvanced with plans to introduce Holsetturbochargers on its middleweight truck enginerange. Eicher expects to build around 33,000commercial vehicles in 2005-06, of which about20,000 will be LCVs.

Holset turbocharger specifiedon Eicher trucks in India

Exhibiting Acrossthe World

Page 12Page 11

HX25W Turbocharger

Holset exhibits each year at the ADS convention

Holset exhibit at 2005 Goodwood Festival of Speed

Eicher E483 LCVImage courtesy of Eicher MotorsHolset celebrate successful business relationship

with Eicher

Turbine high cycle fatigue (HCF) is a phenomenon that presents areal challenge to turbocharger designers and developmentengineers. It occurs when aerodynamic forces acting on theturbine blades make the wheel resonate to an undesirable extent.

With each resonant cycle, the blades are deflected from their natural shape,being bent backwards and forwards. Eventually, such repeated bending canlead to material cracking and an ultimate fracture, typically with a piece ofblade breaking away, triggering severe out of balance forces likely to cause afailure of the whole turbocharger system. Such an event is referred to as highcycle fatigue because the blades resonate at a very high frequency (around10,000 Hz cycles per second). It is not to be confused with low cycle fatigue(LCF), arising through the alternating stresses caused by the wheel speedvarying due to the operation of the engine, for example in a bus application,where the vehicle is repeatedly accelerating and slowing down.

High cycle fatigue is a difficult problem to avoid and expensive to correctexperimentally. Therefore an analysis tool that enabled the engineer to predictHCF blade deflections at the turbine design stage would be extremely helpful.

So how could such an analysis tool be developed?

Firstly, it is necessary to predict the frequency at which the blade will deflect.This is not a straightforward exercise, as there are a number of naturalfrequencies associated with a piece of rotating machinery. This is because theblades deflect in a number of ways, from a simple, fairly easily understood,bending of the blade through to very complicated bending and twisting modes,often with frequencies increasing as the modes get more complex. Figure 1shows a picture of the blade with contours of deflection for mode 1 and mode 5.These natural frequencies are calculated by running a modal computer analysis,using the ANSYS finite element package, though with supporting validationusing a laser vibrometry measurement technique.

Although such an analysis calculates a turbine blade’s natural frequencies, itreveals nothing about the amplitudes, neither does it help distinguish betweena good or bad design. Any computer analysis strategy is dependent for itsaccuracy on having a good experimental technique against which it can bevalidated. Holset’s R&D team has accordingly developed a method to measureblade deflection. It entails applying a strain gauge to two of the blades,running wires down the shaft and picking up the signal via a telemetry systemmounted on the compressor end of the turbocharger. Figure 2 shows the straingauge installation. This associated test is normally run on an engine bed whereload and speed are varied until the natural frequencies occur. The maximumamplitude is then recorded as the turbine resonance is maintained.

Before attempting to predict the blade strain it is first necessary to understandthe mechanism that produces the force, which in turn ‘excites’ the blades. Asthe exhaust gas enters the housing it swirls around the volute before enteringthe wheel. Some gas particles enter the wheel just downstream from the inletsections, while others swirl right around the volute before passing through theblades (see figure 3). This aerodynamic flow structure creates a pressure fieldthrough which the blades pass. This repeating once per revolution pressurefield can be broken down into a series of Fourier components or sine waves,each with an amplitude and phase angle. In figure 4 these are shownsuperimposed on the pressure field. When the wheel speed reaches a pointwhere its multiple equals one of the wheel’s natural frequencies, forcedresonance will occur because the force is pushing and pulling the blades atprecisely the frequency needed to cause the amplitude to grow. This is called a‘multiplier effect’ and determines the order of excitation. For example, if thenatural frequency of the first mode of vibration is 10,000 Hz and the wheel isrotating at 120,000 rpm then the strain amplitude will occur at 5th order as120,000/60 = 2,000 rps x 5 = 10,000 Hz. That is to say the 5th order Fouriercomponent of the pressure field is providing the alternating force at theresonant frequency. The amplitude of the pressure distribution and the Fouriercomponents is a key contributing factor to blade deflection and HCF.

It follows that the aerodynamic design of thehousing volute is one of the keys to HCF. Figure5 shows two pressure distributions from an olddesign and new aerodynamic design. The newdesign has a much smoother distribution, fromwhich a lower blade vibration could be expected.

Using CFX computational fluid dynamics programit is possible to calculate the full unsteady flowin the housing/wheel combination using our 32node parallel PC cluster. This calculation cantake up to a week to run, even with plenty ofcomputing power. However, from the calculationwe can obtain the amplitude and phase angle ofthe pressure field at every node on the surfaceof the blade. This can then be used as inputinto the ANSYS program enabling a full harmonicanalysis of the blade deflection.

This calculation was run for the new and oldhousing using the same wheel. The strainsagainst the telemetry measurement for 5th and

6th order vibration were compared (see figure 6).Clearly the prediction compares well with themeasurement and the new housing produces asmaller strain, therefore it should be much lessvulnerable to HCF.

Through this work Holset engineers haveimproved their understanding of how high cyclefatigue occurs and the related contributingfactors. Through experimental and computationaldevelopment a tool is now available that can beused to improve understanding of the interactionbetween wheel and housing, and of howdifferent wheels behave under vibration. Themethod works well for simple first modevibration, although further work is needed tovalidate the method for more complex modesand work will continue in the quest to gain abetter understanding of what are quite complexphenomena.

Fourier Transform of Pressure Wave

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-180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180

Angle from Tongue ( %)

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New Design

Distance around volute (degrees)

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Fig 1 - Contours of deflection for modes 1 and 5

Fig 4 - Turbine housing pressure field with 1st to 5th Fourier components

Fig 5 - Pressure field from new and oldturbine housing design

Fig 2 - Turbine wheels with strain gauges attached

Fig 3 - Computation of exhaust flow around the turbinehousing and wheel

ImprovingAnalysisCapability inorder to reduceTurbine HCF

Page 14Page 13

Written by Stuart Kitson, Chief Engineer – Turbocharger Technology

0

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Fig 6 - Predicted and measured relative blade strainfrom old and new housing

Giving turbochargers an electrical boost

HTithe latest news for holset turbochargers’ customers

edition 5

Inside this edition:P3 CompressorPerformance Mapping

P5Chinese MarketChanges

P9Temperature Measurementon a TurbochargerImpeller

Our GoalsHolset Turbochargers place the utmost importance on achieving high levels of product and service quality.

Our people are the single most valuable asset we have to ensure we meet your requirements. Through structuredtraining development programmes we encourage ouremployees to spend approximately 5% of their workingtime in training and personal development.

Our operations worldwide are certified to TS16949 qualitystandard and we welcome suggestions as to how we canfurther improve our performance to meet your needs.

We take our environmental obligations seriously and all our worldwide sites have achieved ISO14001. Our products have an important part to play in helping to improve engine emissions.

Our goal is to provide the lowest total cost solution for your turbocharging needs.

Part No. 3766118 Issue 5 Ref: AJS/OR