Thermal and System Management Apprach fr Exhaust Systems Amit Deshpande, Frank Ppielas, Chris Prir, Rhit Ramkumar, Kevin Shaver Sealing Prducts Grup, Dana Hlding Crpratin Abstract: The autmtive and heavy-duty industry (ff- and n-highway) requirements fr emissin, nise and fuel reductin and cntrl have becme mre stringent. Based n the cmplexity f the system with its invlved cmpnents and perating envirnment a new apprach needed t be develped t meet the new demands. Tday it is almst given that CAE plays the central rle in engineering develpment, nt nly des it ffer the ptential fr shrter develpment cycles and reduced csts but it als ffers the ptential t ptimise cmplex systems and demnstrate cmpnent and system limitatins. A cmprehensive apprach as described in the present paper requires a detailed understanding f the cmpnents, their functins and interactin as well as their future develpment trend. Fr its implementatin a cmplex testing infrastructure is needed t serve as a basis fr cmpnent and system validatin and crrelatin. The testing infrastructure is a critical part f the prcess fr develping the material prperties needed fr CAE input A mdern exhaust system is dealing with extreme temperature envirnments, which can be briefly characterized with key wrds like heat sak, transient cnditins, aging, creep, distrtin, fluid and air flw, heat flux, radiatin, cnvectin, reflectin, time, plasticity, etc. This cllectin f terms alne gives an enrmus feeling f the cmplexity we are dealing with. Frm a simulatin perspective it invlves disciplines such as FEA, CFD, NVH and FSI. Bringing this tgether under ne umbrella is the bjective f the presented paper. It ranges frm newly develped experimental and simulatin techniques t data handling and management thrugh SLM. Keywrds: CAE, CFD, FSI, Fluid Structure Interactin, NVH, Thermal Management, System Management, Creep, Aging, Transient, reflectin, radiatin, cnvectin, plasticity, flw, flw rate, heat sak, thermal imaging 2009 SIMULIA Custmer Cnference 1
1. Intrductin 1.1 Exhaust systems in the autmtive / heavy duty industry It is well knwn that regulative requirements fr emissin, nise and fuel reductin and cntrl in the areas f autmtive and heavy-duty industries (ff- and n-highway) are becming mre stringent. Histrically the exhaust system was a basic arrangement f cmpnents t channel and guide waste cmbustin gas frm the engine. With the renewed fcus n emissins, NVH and fuel efficiency mre emphasis is being placed n the exhaust system as a critical cmpnent t achieve these gals. Hardware cmpnents like catalysts (CAT), turb chargers, exhaust gas recirculatin (EGR), active diesel particulate filters (adpf) and Selective Catalytic Reductin (SCR) technlgy have emerged thrugh rapid develpment t meet the legislative requirements (reduced emissin regarding NO x, CO and diesel particulates) placed n sme markets and regins. In additin t the legislative requirement the exhaust system must als meet the market expectatins fr cst, NVH and fuel efficiency. As new technlgy was added t the exhaust system, the cntrl, management, functinality and rbustness were cntinually refined and imprved. Tday s exhaust and after treatment systems have their wn cmputer cntrl unit and ften designed in the frm f a cascade system, like sequential turb charging, flexible EGR and active catalytic cnverters. The ultimate gal is t have a real-time, clsed lp cntrl system based n cmbustin measurements and exhaust system readings. This fully integrated system apprach wuld als utilise a certain level f intelligence fr cntinuus cntrl and management. Besides thse develpments, the exhaust system integratin is being applied frm passenger car applicatins, t n-highway heavy duty truck applicatins and als t ff-highway applicatins. There is meanwhile tight regulatin in place (and will be even strnger in the future) fr cnstructin equipment especially when perating in residential envirnments. 1.2 Rle f sealing applicatin fr exhaust systems As mentined it is very clear that the exhaust system has becme mre cmplicated nt just frm a management perspective but als based n the sheer number f additinal cmpnents. The challenge then is t cnnect and jin these cmpnents prviding adequate sealing, rbustness and durability in a very hstile envirnment. The additinal types f jint and cnnectins include Pipe flanges Manifld flanges Slip jints V-clamps 2 2009 SIMULIA Custmer Cnference
Welds Etc. All but the welded jint require sme kind f a sealing element. Since the exhaust system has develped frm a simple pathway fr the exhaust gas, s t have the demands placed n the sealing elements. These additinal demands include: Thermal management (Insulating / Cnducting ) Damping functin t reduce, eliminate r avid nise and excitatin Thermal expansin cntrl. The sealing functin itself became mre rigrus with clear sealability targets being demanded fr each applicatin. Quite cmmn tday is t have a maximum limit f 2l/min pre and pst peratin. Even thugh this is already a tugh requirement the future will demand even further imprvements fr sealing. 1.3 Operating envirnment Since we are talking abut the exhaust system, naturally we are dealing with a higher temperature envirnment. Besides a harsher thermal envirnment there are als additinal cnsideratin fr higher back pressures and vibratin issues. In general we expect t see the fllwing cnditins: Maximum exhaust gas temperature: 1050ºC fr gasline applicatins 850ºC fr diesel applicatins. Based n the driving cnditins, the engine packaging envirnment and the shielding f specific areas, the skin and flange temperature f the cmpnents are cntinuusly changing. With gd air flw management arund the engine cmpartment and exhaust system, the flange temperatures are nrmally lwer than the exhaust gas temperature. Hwever, nce air flw becmes stagnated (heat sak), like idle cnditins, in an encapsulated envirnment r aftertreatment peratin, temperatures may actually rise beynd the maximum gas temperature. A gd maximum temperature assumptin is 1100ºC. Exhaust back pressures have cntinued t increase with the additin f exhaust gas aftertreatment. Design cnsideratins fr back pressures in excess f 5Bar are cmmn depending n the applicatin and system design. Besides increased temperature and system back pressure, the additinal cmpnents (such as multiple turb chargers) in general create a much higher prbability fr vibratin and, thus nise and fatigue. Especially critical is the crrect placement f cmpnents fr their supprt and surrunding envirnment. A wrngly psitined and supprted turb can create excitatin in 2009 SIMULIA Custmer Cnference 3
excess f 25g that will ultimately fail surrunding cmpnents in a very shrt time perid. The system and cmpnent resnance is als a key cnsideratin. Cnsidering the jint r cnnectin fr each cmpnent f the exhaust system is nt just a simple questin f sealability. The thermal, vibratin and system interactin is critical t achieve a cst effective and rbust exhaust gas after treatment system. T ensure that these gals are met a system apprach is needed fr design. This is nt just frm a gemetrical pint f view, as dne t ften in the past making sure that all cmpnents just fit tgether, but frm a functinal and peratinal perspective. This is why we started with the Thermal and System Apprach fr Exhaust Systems. 1.4 The rle f CAE Since we are in a fast-mving envirnment where time-t-market, cst, first-time-right, design and quality are majr driving factrs in develping new designs, there is a definite need t lk int new tls in develpment. Cmputer Aided Engineering (CAE) started here t play the majr rle. It has lng prven its reliability fr the different applicatins regarding accuracy, hwever t achieve this level f accuracy requires a detailed understanding f the materials and their prperties, which is especially challenging in the exhaust envirnment. Hw CAE as an verall develpment tl is implemented plays a majr rle fr its effectiveness regarding cst minimizatin and reductin in time-t-market. Factrs influencing here, are: Hardware architecture Sftware perfrmance and interactin with hardware Sweet spt identificatin fr the specific mdel / prduct simulatin envirnment Simulatin prcess flw. Leaders in the market implemented the s-called analysis-led-design philsphy in develpment, this made it pssible fr them t deliver huge ptential fr cst savings and avidance. 4 2009 SIMULIA Custmer Cnference
2. Thermal and System Management Apprach fr Exhaust Systems 2.1 Thermal and System Management Apprach The cmplexity f the exhaust system as described abve and in light f the mentined stricter regulatins requires a new apprach away frm just a jint evaluatin. It is a must that all the cmpnents are linked int a whle: a system. This system des nt have t be, at the initial stage, the cmplete exhaust / aftertreatment system but a sub-system. Examples fr such a sub-system are: Cylinder head / exhaust manifld / turb charger / catalytic cnverter / shielding cmpnents when evaluating just the exhaust manifld gasket Exhaust manifld / turb charger / EGR / SCR / shielding cmpnents Exhaust manifld / catalytic cnverter / dwn pipes / DPF / shielding cmpnents EGR / intake system / shielding cmpnents. Just thse few examples prvide a gd verview f the challenges related t linking the exhaust system cmpnents tgether. This alne explains the need fr such an apprach when talking abut develping the system while ptimizing the nise level at the same time. The mst challenging factr thugh is the thermal factr. In the past when develping / designing the individual jints separately frm each ther the evaluatin criteria were different as well. By saying this it becmes clear that just jining the cmpnents is nt the slutin. The evaluatin criteria need t be adjusted as well. This means that the system has t be tested under the same cnditins. Only this guarantees that the thermal interactin between the different cmpnents is n the same level and ffers ptential crrelatin. It is like testing all the cmpnents f the system / sub-system tgether n the dynammeter r the ht-gas-test bench. The first factr which needs t be cnsidered fr the system is thermal interactin, nt s much the mechanical interactin. Thermal interactin means: Thermal stress induced int the structural cmpnents Thermal balance in the system. Thermal balance is the cnsideratin and understanding f: Cnductin Cnvectin Radiatin between the interacting cmpnents. 2009 SIMULIA Custmer Cnference 5
In CAE terms we are talking abut a cmplex multi-physics envirnment f fluid-structureinteractin (FSI). This leads int the Thermal Management / System apprach fr exhaust systems (Figure 1): Figure 1: Thermal Management / System Apprach System understanding: understanding f the verall system layut, functin, and, especially the thermal flw between the cmpnents Benchmarking: Understanding f the system cmpnents and their develpment trends Evaluatin f the market trends fr sealing prducts and their cmpetitive strategy Advanced develpment: Basic develpment and study f the basic features / mechanism / cmpnents and designs fr sealing prducts in exhaust applicatins, like: Frictin and it s influence n fretting and fatigue Material develpment Cating develpment Sealing feature develpment, like bead r stpper types fr metal gaskets Test methd develpment CAE technique develpment. Jint parameters: design recmmendatins and standards fr the verall jint cmprising f: Structural cmpnents Sealing cmpnent. 6 2009 SIMULIA Custmer Cnference
Applicatin guidelines: specific design recmmendatin fr sealing prducts fr the different exhaust applicatins Manufacturing: manufacturing guidelines fr the recmmended sealing prducts. The bjective f all this is t understand the cmplex interactin f the exhaust / aftertreatment system (including intake system) in rder t design, simulate and test (precisely and efficiently) Dana Sealing Prducts applicatins, alng with crdinatin with ther suppliers and the final custmer. The main drivers fr the exhaust / after treatment system are, as mentined: Emissin cntrl Fuel cnsumptin NVH cntrl. Understanding thse drivers and their influence in the cntext f the exhaust / aftertreatment system fr sealing prducts, ne can derive the main influencing factrs fr thse applicatins: Thermal influence Structural influence Calibratin f the system. Thermal influence: The trend in the system is twards higher exhaust gas temperatures. Emissin and fuel cnsumptin requirements als define limitatins n the upper spectrum f the temperatures range fr certain exhaust cmpnents, like the DPF r catalytic cnverter. The mst critical cnditin is usually the cld start. The faster the system can reach the lwer temperature limit f the ptimal range fr the mentined cmpnents the less emissin will be emitted. Basically thermal influence can be characterized with the fllwing factrs: Maximum temperature will increase The system will be subjected t steeper thermal gradients. Structural influence: The factrs in this categry are clearly interlinked with each ther and cannt be evaluated independently: Jint and cmpnent rigidity 2009 SIMULIA Custmer Cnference 7
Weight Material Assembly between cmpnents. Fuel cnsumptin drives twards lwer weight. This pushes the develpment and use f alternative light weight materials. Weight als can be reduced by ptimizing the gemetry f the structure. Thus, it s influencing the jint and cmpnent rigidity. The thermal influence / trend as mentined abve requires new strategies regarding materials used t withstand thse thermal cnditins and being creative in implementing new structural designs. An example here is the trend frm cast exhaust maniflds t fabricated single r even dual-walled exhaust maniflds. The cmplexity f cmpnents in the exhaust system requires a special apprach in the assembly f thse cmpnents. The engine packaging space, at best, has remained cnstant and in sme applicatins has reduced due t vehicle crash zne requirements. T add t the challenge, this limited space availability is required t package a greater number and cmplexity f cmpnents. This requires an innvative assembly strategy fr relative ease f assembly during manufacturing as well as under service cnditins in the field. This usually results in fewer r smewhat simplified blting / fastening layuts and prcedures. This f-curse has a dramatic influence n sealing capability / perfrmance f a jint and vibratin behavir under perating cnditins. In rder t understand hw thse drivers, factrs and perating cnditins may influence the sealing technlgy and, thus, exhaust system behavir we need t let s have a lk what Dana Sealing Prducts are invlved in fr exhaust applicatins. When talking abut Dana Sealing Prducts applicatins fr pwertrain and exhaust systems ne first needs t knw what is understd under sealing prducts. Thse prducts include flat gaskets and ring seals, rubber-mlded gaskets and seals, cvers and pans (therm-plastic and therm-set), shielding cmpnents. Flat gaskets and ring seals, like: Cylinder head gasket Rcker cver gasket Cylinder blck hand hle gaskets Exhaust manifld gasket Turb charger gasket Exhaust gas recirculatin (EGR) gasket Slip jint gasket V-band gasket,.. 8 2009 SIMULIA Custmer Cnference
Rubber-mlded gaskets and seals, like: Valve cver gasket Cam cver gasket Frnt cver gasket Windw gasket Intake gasket Valve stem seal Rubber inserts,.. Cvers and pans, like: Valve cver Cam cver Frnt cver Oil pan,. Shielding cmpnents, like: Exhaust manifld shields Dwn pipe shields CAT adpf Sensr shields,.. Figure 2 gives a visual pwertrain example f what s typically invlved fr Dana Sealing Prducts. 2009 SIMULIA Custmer Cnference 9
Figure 2: Sealing System Thse applicatins range frm: Lw temperature (belw 400ºC) t high temperature (abve 1000ºC) Quasi-static t dynamic Cmbustin gas t fluid seals Thermal t nise shielding Thermal reflectin t thermal insulatin Frictin withstanding t frictin reducing Sealing t cntrlled metering f fluids,. 2.2 The new rle f CAE The apprach fr analyzing the different sealing jints and thereby the sealing system fr a pwertrain as a whle is accmplished by fllwing step-by-step prcess utlined belw in Figure 3. Since there are several different cmpnents and different materials invlved in the exhaust system, it is all the mre imprtant t have a database with a cllectin f material prperties at different thermal cnditins. The apprach can be slightly mdified fr the different parts f the exhaust system. The main driving factr here is the gas temperature, which dictates the different 10 2009 SIMULIA Custmer Cnference
material types and the design directin that is chsen. Since several cmpanies are invlved designing and manufacturing these different cmpnents, it is all the mre imprtant t bring all the cmpnents tgether, t analyze them tgether and t lk at the interactin between each ther. Cmbustin Mdeling Heat Transfer Analysis fr Pwertrain Clant Flw Analysis FSI Analysis f exhaust cmpnents Thermal-Stress Analysis Figure 3: Analysis Flw Prcess The starting pint f CAE analysis is the cmbustin mdeling using a 1D CFD cde like GT- Pwer. This prcess invlves the mdeling f the intake system, exhaust system and als ther sub cmpnents like turb chargers and EGR. This data r analysis may be dne in-huse r received frm a Pwertrain OE. A typical mdel fr a 4 cylinder gasline engine is shwn in Figure 4. 2009 SIMULIA Custmer Cnference 11
Figure 4: GT-Pwer Mdel Example The results frm the GT pwer mdels such as heat transfer cefficients and the skin temperature prvide the inputs fr a heat transfer analysis f the pwertrain. The utputs frm GT-Pwer are als used as inputs fr the flw rates and temperature f the exhaust gases fr the CFD calculatin. The initial flw thrugh the exhaust systems can be ptimized by using a 1D CFD sftware such as GT-Pwer. This analysis can be used as an input fr mre detailed sub-system simulatin. GT- Pwer is a 1D cde that is widely used t simulate pwertrain systems, representing all system cmpnents with 1D mdels. Hwever, certain cmpnents, like intake and exhaust maniflds, exhibit a high degree f three dimensinal behavir and cannt be accurately represented by a 1D mdel. T mre accurately represent these cmpnents in the pwertrain system mdel, a CFD simulatin can be cupled t a GT-Pwer simulatin. By cupling the tw techniques, 3D cmpnents can be simulated with CFD cde while simulating the rest f the system using the 1D mdel available in GT-Pwer. Thrughut the simulatin, infrmatin is cntinually passed back and frth between the cdes, resulting in mre accurate results frm cmpnent level as well as n system level. The next step fr the study f the exhaust system is the CFD analysis f the exhaust gas flw path. CFD analysis gives gas velcity distributin within the ht exhaust gas regin. In CFD analysis, the ht flw regin f the gases (see Figure 5); starting frm the exhaust prts all the way t the dwn-pipe is cnsidered. This may include exhaust manifld, EGR, turb charger, catalytic cnverter and ther exhaust system cmpnents. The analysis can be separated fr different cmpnents depending n the cmpnents included r the cmplexity f the results that need t be btained frm the analysis. Once the fluid flw distributin is achieved alng with the temperature prfile in the fluid dmain, the fluid dmain is cupled with the structural dmain using a cupling prgram such as MpCCi t run a heat transfer analysis t btain the temperature distributin n the structural cmpnents. The temperature distributin can be a steady state distributin which represents cntinues perating cnditins f the cmpnents r it can be a transient cnditin, which represents the initial start up cnditins, cl dwn r in general thermal swing cnditins. This heat transfer analysis results in the thermal distributin n the structural cmpnents which are further used in the sequentially cupled thermal-stress analysis fr the structural dmain. Analysis f the assembly cnditins plus the perating cnditins is carried ut as well as the durability analysis f the jint by subjecting the hardware t heating and cling cycles (thermal cycle). 12 2009 SIMULIA Custmer Cnference
Figure 5: Velcity and static cnturs f exhaust gas flw in the manifld The jint behavir such as between head and exhaust manifld in this case, is a strng functin f the maximum temperature and rate f temperature change. Hence, the temperature data btained frm the CFD analysis is significant in this case. This demands a ratinal set f bundary cnditins (BC s) fr the CFD analysis. Fr steady state case, a generic set f ratinal BC s is Mass Flw Inlet and Pressure Outlet. It includes the gas temperature at the inlet and als natural cnvective heat transfer cefficients n all the ther uter surfaces. In case f a transient CFD analysis, a prfile file invlving flw rates at different crank psitins is read in as an input fr CFD analysis. The FSI here invlves the transfer f temperatures and surface heat transfer cefficients (HTC s) frm the CFD slver (Fluent) t structural slver (Abaqus). The cupling prgram used t cuple the fluid and slid regin, transfers the temperatures, HTC s; and Abaqus calculates the temperature distributin within the slid as steady state is reached. Any intermediate temperature prfile gives the rate f heat diffusin within the slid. The structural mdel shuld have all the cntact data with three main material prperties: Thermal cnductivity Density Specific heat. By using instantaneus temperature prfiles at any step, transient effects can be simulated within the Abaqus mdel. The temperature gradient plays a dminant rle in the structural sundness f the different cmpnents f the exhaust system. It als defines hw different cmpnent interact with each ther. Fr every jint in the system, there is, usually a gasket r ther sealing element that takes 2009 SIMULIA Custmer Cnference 13
care f the sealing. The gasket plays a significant rle in the design f nt nly the jint, but als the system as a whle. Until recently mst f the structural analysis was dne n a cmpnent r jint-by-jint basis due the cst f cmputatin pwer and the sftware limitatins. But nw with the multi-cre cmputer technlgy and the distributed memry prcessing technlgy available in Abaqus, larger and mre detailed mdels can be created and analyzed within a much shrter time frame. The faster turnarund time als helps in incrprating design-f-experiments (DOE) which in turn fine tunes design aspects nt nly fr the gasket but als fr cmpnents and material selectin. One f the primary jints where this was implemented was the jint between the head and the exhaust manifld. Usually the exhaust gasket was analyzed alne with the head & the manifld as the mating surface nly, but hw this jint impacted the cylinder head gasket functinality was rarely studied. Including the exhaust gasket and the intake gasket alng with their respective maniflds, fr the cylinder head gasket analysis shws hw the different blted jints behave tgether and hw the thermal stress in the cylinder head affects the intake jint and exhaust jints r vice versa. The different cmpnents blted n the cylinder head als influence the defrmatin f the cylinder head during the assembly t blck and, thus the thermal balance f the whle system. The exhaust system usually invlves sme srt f shielding whse functins are tw-fld. Thermal Acustical Prtective Shields (TAPS) (Figure 6) help in prtecting the electrnic cmpnents frm getting damaged due t heat as well as trapping the heat between the cmpnent and heat shield. It can als prvide as a nise absrber fr the vibratins in the exhaust system. Due t the presence f the heat shield, the cmpnents such as exhaust manifld can be htter due t the radiated heat that is reflected back t the manifld. This in turn increases the temperature in the manifld and the dwn pipes, which needs t be cntrlled fr ptimal perfrmance f the catalytic cnverter. This has t be cnsidered when running a heat transfer analysis and a subsequent thermal stress analysis. Figure 6: Thermal Acustical Prtective Shield with Integrated Exhaust Manifld Gasket The impact f airflw arund the cmpnents may als need t be studied, as the heat shield can be used t deflect ht air frm thermally sensitive cmpnents. In sme cases, the air dmain is mdeled alng with the structural cmpnents t study hw the ht air frm, as example the turb 14 2009 SIMULIA Custmer Cnference
charger envirnment and ther ht pipe areas, can rise and affect different temperature sensitive areas (Plastics, sensrs, wires etc). The material selectin f the gasket plays an imprtant rle in the thermal distributin between the jint as well as the structural behavir. The gasket can act as an insulatr r a cnductr and this has t be cnsidered when running the heat transfer analysis f the system. The structural respnse f the gasket plays a rle in the selectin f the flange thickness, amunt f blt lad required and als the material fr the flanges and blts. The different sealing features, such as stpper heights and tpgraphy etc, alng with the thermal cnductivity f the gasket can help with reducing flange distrtin, creep, and a reductin f blt lad lss and thereby increasing the life f the assembly. The basic material prperties such as mechanical prperties alng with the thermal cnductivity, specific heat and density f the different materials used in the analysis need t studied as a functin f temperature and time fr an exhaust applicatin. In rder t understand the dynamics f the system, the dependency f material prperties n time and temperature must be studied. The thermdynamic changes in material prperties are accelerated at higher temperatures. It is necessary t determine the relatinship between time and temperature in rder t ptimize testing prcedures. The test methds must allw fr accelerated develpment while maintaining a realistic cmparisn t actual perating cnditins. The temperature dependent material behavir fr a gasket design as shwn belw is studied at different lad cnditins (Figure 7). This type f data is dcumented fr varius gasket designs and different materials using SLM (Simulatin Lifecycle Management) sftware, which helps the analyst t quickly search fr the relevant data. In case new data is added t the database the analyst is prmpted t rerun the analysis with the new data t update the results. Crrelatin is an essential part f the CAE analyst s jb. As a design prject prgresses, mre and mre data is cllected, and this helps in reevaluating the analysis parameters that were previusly used during the design phase and als in crrelating the different results that were btained frm the analysis wrk. The typical types f crrelatin wrk include the cmparisn f bead heights and lad deflectin data f samples at end-f-test (EOT) against the riginal analysis results. Als the remaining blt lad data can be cmpared t the analysis predictin. In the case f heat transfer simulatin, the thermal map that was btained frm a cuple analysis r just CFD analysis can be cmpared t therm graphic camera images as shwn in Figure 12. 2009 SIMULIA Custmer Cnference 15
Figure 7: Lad / Defrmatin behavir f a sealing bead at different temperatures 2.3 Testing fr exhaust sealing systems Testing fr exhaust sealing systems plays an essential rle in ptimizing and crrelating simulatin results. The prper inputs must be prvided t guarantee the best results. High temperature systems intrduce additinal testing requirements that are nt generally cnsidered fr ther applicatins. The challenges f evaluating material prperties and cmpnent interactin at extreme temperatures require develpment f advanced testing techniques. In rder t understand interactins and verall behavir f a thermal system, testing needs t be applied t all levels f the thermal system. Testing prcedures can be divided int three main levels: Material Cmpnents Full systems. Thse levels need t cver the fllwing techniques: Establish material prperties Prvide validatin Crrelatin supprt. 16 2009 SIMULIA Custmer Cnference
Fretting and frictin play a central rle in the develpment f high temperature sealing slutins. The extreme changes in perating temperature can generally cause ptentially damaging frictin frces. These frces are intrduced by thermal expansin and cntractin and are magnified by the dissimilar nature f the jint and gasket materials. Mst cmmercially available frictin analysis prcedures prvide a lw-temperature shrt-term result. A technique has been develped that invlves evaluating the hysteresis f the frictin frces and intrduce a wear cmpnent t the testing. This is a requirement fr understanding the wear behavir seen in exhaust sealing systems. It is necessary t understand hw the frictin cefficients behave ver thusands f thermal cycles as surface cnditins are altered due t mechanical wear. A thermal cycle is a relatively slw phenmenn. The best ptin fr accelerating the cycle is t apprximate the mtin using mechanical methds. The entire fixture can be heated and cled as required t induce the thermal changes in the materials. Figure 8 shws an image f the frictin testing fixture. The frictin frces must be sampled at a high rate t ensure a distinct utput can be assembled that cmpletely describes the frictin curve hysteresis. Figure 8: Frictin Test Fixture Temperature lgging and cntrl is an integral part f any high temperature testing system. In rder t generate thermal maps a large array f thermcuples can be emplyed. An alternate methd invlves the use f thermal imaging. New imaging equipment and sftware allws fr nearly infinite reference pints cmpared t the relatively lw limits f cnventinal data lgging hardware. The thermal imaging system can recrd all visible areas f the hardware and gather transient thermal data. When this surface temperature data is cmbined with material prperties and thermcuple measurements frm within the hardware and exhaust stream, a highly accurate thermal map can be cnstructed. This helps t understand and predict thermal influences such as flange distrtin and thermal-mechanical threshlds. The infrmatin is als used t identify the critical design areas fr specific applicatins. Figure 9 illustrates the use f a thermal imaging system t measure surface temperatures f an exhaust system. 2009 SIMULIA Custmer Cnference 17
Figure 9: Thermal Imaging f an Exhaust System Static lab testing allws fr sme f the mst basic material input fr simulatin analysis. The challenge fr exhaust systems is taking the industry standard test prcedures and evlving them t be cmpatible with high-temperature equipment. A variety f thermal chambers are adapted t wrk inline with existing test equipment t make test setups mre mdular and adaptable fr the needs f the specific peratin. Special attentin must be paid t the selectin f materials used in the cnstructin f fixtures and supprting equipment. Almst all test equipment used fr evaluating exhaust systems must be custmized since cmmercially available testing slutins are rarely cmpatible with the high temperatures dictated by the end-use applicatins. Additinally, mst available systems are designed fr tensin testing, while gasket testing needs t be cnducted under cmpressin. This requires additinal rbustness f the test equipment materials, especially regarding creep initiatin due t higher induced stress. Figure 10 shws an example f a high temperature furnace adapted fr lad frame cmpatibility and design fr cmpressin testing. 18 2009 SIMULIA Custmer Cnference
Figure 10: High Temperature Cmpressin Testing Furnace It is als necessary t perfrm dynamic evaluatins in rder t tie the material and cmpnent layers f testing int the verall system level. An engine test is the mst cmmn methd used t evaluate the perfrmance f exhaust gaskets. This type f test is very expensive and has lw availability. It als has the disadvantage f narrw peratinal ranges and interdependency n ther systems. The ultimate gal in high temperature exhaust testing is t have a test stand that can cmpletely cver the mst extreme ranges f engine perating cnditins and t increase flexibility in terms f parameter setup. A dedicated exhaust test stand that can heat a stream f gas t temperatures higher than 1000ºC is emplyed t give the best results. Figure 11 shws a ht gas test stand setup and the test stand in peratin t demnstrate the extreme temperatures prduced during this test. 2009 SIMULIA Custmer Cnference 19
Figure 11: Ht Gas Test Stand and setup with glwing hardware The stand is able t prduce dwnstream pressures cmparable t mdern turbcharged exhaust backpressures. Mass flw rates greater than 1000kg/h are generated. This setup enables custmizatin f test cnditins well beynd that available in any single engine. This equipment is used t generate simulatin input and als t verify results f the analysis. Figure 12 illustrates the use f ht gas testing and thermal imaging t verify FEA simulatin results. Figure 12: Thermal imaging test result with crrelatin t CAE 20 2009 SIMULIA Custmer Cnference
2.4 Data management Management f the large amunt f material data and analysis data is anther area which needs t be addressed. While simulatin technlgy is cnstantly evlving t meet the demands f designers and engineers, there remains a wide disparity in the effectiveness f simulatins t impact prduct/prcess design decisins. This disparity exists at multiple levels: acrss industry segments, acrss cmpanies within an industry segment, acrss simulatin disciplines (structural, fluid, chemical, etc.), within a cmpany, and even acrss individual methdlgies within a simulatin discipline. The quest t markedly imprve the efficiency and effectiveness f simulatin remains a challenging but fundamental gal fr many cmpanies. [1] The efficiency and effectiveness f simulatin within a wrkgrup r enterprise is driven by several factrs, including: Cmpetency f the simulatin technlgy and the peple utilizing it Integratin, adptin, and acceptance within standard business prcesses Capture, management and reuse f the resulting intellectual prperty. A well-knwn data management tl in the industry is Prduct Lifecycle Management (PLM). PLM systems have evlved rapidly in recent years and nw prvide cllabrative Virtual PLM f cmplex prduct, prcess, and resurce infrmatin - frm marketing and design t manufacturing and maintenance. The requirements f simulatin technlgy, methds, data and prcesses are in many ways mre demanding than thse assciated with PLM, including: Data Mdel Perfrmance Cntext. The emerging attentin fcused n imprving simulatin effectiveness within PLM and scientific envirnments, is referred t as Simulatin Lifecycle Management (SLM) [1]. This cvers the different disciplines invlved in the thermal management / system apprach. The data, fr example generated thrugh simulatin can be divided int 3 main categries [2]: Data directly supprting prduct / prcess IP (intellectual prperty) Data supprting simulatin IP Un-retained data. The degree f integratin acrss the simulatin and prduct/prcess wrlds will vary with rganizatinal type and structure and is driven by a number f factrs, but there are several critical 2009 SIMULIA Custmer Cnference 21
principles that must be adhered t achieve the full benefits SLM can deliver. At its cre, an SLM slutin must have been designed frm the utset t pssess the apprpriate architecture t satisfy the integratin, deplyment and maintenance demands f a brad and cnstantly changing set f infrmatin technlgy (IT) envirnments. Fur functinal elements that an effective slutin must prvide are [2]: Built-in Cllabratin Simulatin Data Management Prcess Autmatin, Integratin and Optimizatin Decisin Supprt. The aspects described in this paper regarding a thermal management apprach and its detailed cmplexity epitmizes the need fr an SLM system. By cllabrating with SIMULIA n develping and implementing SLM and develping specific features fr ur business needs will prvide us with the necessary tls t guarantee a functinal system apprach fr the future. This is nt just frm a simulatin but als frm a management perspective. By studying the SLM architecture and the needs f ur apprach we can ensure, frm the utset that all ur structural, data and dcumentatin requirements are met and future prfed. 2.5 Cnclusin A cmprehensive Thermal Management / System Apprach has been develped t better reflect the cmplexity f an exhaust / after treatment system fr autmtive and heavy duty applicatins. This apprach cvers all the different stages during develpment frm design cncept ver ptimisatin and validatin t crrelatin f simulatin results. It prvides an imprved understanding f why simulatin cannt exist in islatin but needs t be cmbined with a basic understanding f the exhaust system, the generatin f material prperties and the evlving experimental testing techniques. Nne f these elements can exist in islatin they must cmplement and interact with each ther t make sure that the final prpsed design can meet the highest functinal and quality standards, as well as prviding the best tls t meet the first-timeright gal. It was als shwn that because f the cmplexity f this apprach n all levels there is a need fr a new data management apprach. This can be realized by implementing SLM technlgy. It prvides mre than just a classical data management apprach by ffering greater efficiency and smarter simulatin IP with its different layers f engagement, it helps t use the data based n the need f respnse. Nt nly has the analyst benefited frm its structure but als the entire engineering team and management where the data can be used fr decisin making. We are aware that there are still a lt f tasks t be accmplished fr the fine-tuning f this apprach and implementing sme f the features. The success achieved s far and frm custmer feedback fr this apprach it is clear that this is the future fr cntinued develpment and a rute fr cmpetitive advantage. References 22 2009 SIMULIA Custmer Cnference
1. SIMULIA: The Case fr Simulatin Life Cycle Management; reprt 1 f 3; White Paper 2. SIMULIA: The Case fr Simulatin Life Cycle Management; reprt 2 f 3; White Paper 2009 SIMULIA Custmer Cnference 23