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Journal Article

A Miniature Catalytic Stripper for Particles Less Than 23 Nanometers

2013-04-08
2013-01-1570
The European Emissions Stage 5b standard for diesel passenger cars regulates particulate matter to 0.0045 g/km and non-volatile part/km greater than 23 nm size to 6.0x10₁₁ as determined by the PMP procedure that uses a heated evaporation tube to remove semi-volatile material. Measurement artifacts associated with the evaporation tube technique prevents reliable extension of the method to a lower size range. Catalytic stripper (CS) technology removes possible sources of these artifacts by effectively removing all hydrocarbons and sulfuric acid in the gas phase in order to avoid any chemical reactions or re-nucleation that may cause measurement complications. The performance of a miniature CS was evaluated and experimental results showed solid particle penetration was 50% at 10.5 nm. The sulfate storage capacity integrated into the CS enabled it to chemically remove sulfuric acid vapor rather than rely on dilution to prevent nucleation.
Journal Article

Accelerated Fatigue and Modal Parameter Identification of Lightweight Structures

2014-06-30
2014-01-2095
Car components are exposed to the random/harmonic/impact excitation which can result in component failure due to vibration fatigue. The stress and strain loads do depend on local stress concentration effects and also on the global structural dynamics properties. Standardized fatigue testing is long-lasting, while the dynamic fatigue testing can be much faster; however, the dynamical changes due to fatigue are usually not taken into account and therefore the identified fatigue and structural parameters can be biased. In detail: damage accumulation results in structural changes (stiffness, damping) which are hard to measure in real time; further, structural changes change the dynamics of the loaded system and without taking this changes into account the fatigue load in the stress concentration zone can change significantly (even if the excitation remains the same). This research presents a new approach for accelerated vibration testing of real structures.
Technical Paper

Catalytic Activity in the Regeneration of the Ceramic Diesel Particulate Trap

1992-02-01
920362
The rare occurrence during city driving of the exhaust temperature levels required for ceramic trap regeneration without catalytic aid, seems to be the main reason of delay in wide application of the trap. The use of catalysts seems to be more or less necessary. Study of the catalytic activity during trap regeneration had not been very effective so far. This holds equally true for the case of catalyzed trap as for the case of catalytic fuel additives. The lack of a satisfactory theory for the explanation and prediction of catalytic activity, directed international research and development towards the quest of the optimum catalyst, which could support a very simple and low-cost regeneration system. The new approach to the explanation of catalytic activity presented in this paper, denies the above assumption.
Technical Paper

Cordierite Filter Durability with Cerium Fuel Additive: 100,000 km of Revenue Service in Athens

1992-02-01
920363
The first two of a series of traps retrofitted on a pilot fleet of 110 buses of the Athens Bus Corporation were removed for examination after 100,000 km of revenue service. These buses were gradually equipped with the ELBO Trap Oxidiser since the beginning of 1989 and are constantly operated on Cerium based fuel additive. The physical properties and the chemical composition of filters and ash residues were analysed by the filter manufacturers and the fuel additive producer. The results have shown that after two years of operation the filter material remained intact and the ash deposits (consisting mainly of CeO2) exhibit a limited interaction with the cordierite. More than 94% of these deposits are filtered by the monoliths and could be removed to a large extent with the application of conventional methods.
Technical Paper

Diffusion Supporting Passive Filter Regeneration- A Modeling Contribution on Coated Filters

2018-04-03
2018-01-0957
Wall flow particulate filters have been used as a standard exhaust aftertreatment device for many years. The interaction of particulate matter (PM) regeneration and catalytically supported reactions strongly depends on the given operating conditions. Temperature, species concentration and mass flow cause a change from advective to diffusive-controlled flow conditions and influence the rate controlling dominance of individual reactions. A transient 1D+1D model is presented considering advective and diffusive transport phenomena. The reaction scheme focuses on passive PM conversion and catalytic oxidation of NO. The model is validated with analytical references. The impact of back-diffusion is explored simulating pure advective and combined advective diffusive species transport. Rate approaches from literature are applied to investigate PM conversion at various operating conditions.
Technical Paper

Durability Test Suite Optimization Based on Physics of Failure

2018-04-03
2018-01-0792
Dynamometer (dyno) durability testing plays a significant role in reliability and durability assessment of commercial engines. Frequently, durability test procedures are based on warranty history and corresponding component failure modes. Evolution of engine designs, operating conditions, electronic control features, and diagnostic limits have created challenges to historical-based testing approaches. A physics-based methodology, known as Load Matrix, is described to counteract these challenges. The technique, developed by AVL, is based on damage factor models for subsystem and component failure modes (e.g. fatigue, wear, degradation, deposits) and knowledge of customer duty cycles. By correlating dyno test to field conditions in quantifiable terms, such as customer equivalent miles, more effective and efficient durability test suites and test procedures can be utilized. To this end, application of Load Matrix to a heavy-duty diesel engine is presented.
Technical Paper

Effects of Pulsating Flow on Exhaust Port Flow Coefficients

1999-03-01
1999-01-0214
Five very different exhaust ports of diesel and gasoline engines are investigated under steady and unsteady flow to determine whether their flow coefficients are sensitive to unsteady flow. Valve lift is fixed for a specific test but varied from test to test to determine whether the relationship between steady and unsteady flow is lift dependent. The pulse frequency is chosen to correspond to the blow-down phase of an engine running at approximately 6000 rpm, but the pressure drop across the port is much smaller than that present in a running engine. Air at room temperature is used as the working fluid. It is shown that unsteady flow through the five exhaust ports causes, at most, a 6% increase or a 7% decrease in flow coefficient.
Technical Paper

Fatigue Strength Effect of Thread Forming Process in Cast Aluminum

2006-04-03
2006-01-0780
Two thread forming processes, rolling and cutting, were studied for their effects on fatigue in cast aluminum 319-T7. Material was excised from cylinder blocks and tested in rotating-bending fatigue in the form of unnotched and notched specimens. The notched specimens were prepared by either rolling or cutting to replicate threads in production-intent parts. Cut threads exhibited conventional notch behavior for notch sensitive materials. In contrast, plastic deformation induced by rolling created residual compressive stresses in the notch root and significantly improved fatigue strength to the point that most of the rolled specimens broke outside the notch. Fractographic and metallographic investigation showed that cracks at the root of rolled notches were deflected upon initiation. This lengthened their incubation period, which effectively increased fatigue resistance.
Technical Paper

Magnetostrictive and Magnetic Sources of Noise in the Electric Motors

2016-06-15
2016-01-1838
In electric motors the working torque results from the magnetic forces (due to the magnetic field). The magnetic forces are also a direct source of structural excitation; further, the magnetic field is an indirect source of structural excitation in the form of magnetostriction. In the last decade other sources of structural excitation (e.g. mechanical imbalance, natural dynamics of the electric motor) have been widely researched and are well understood. On the other hand, the excitation due to the magnetic forces and magnetostriction is gaining interest in the last period; especially in the field of auto-mobility. Due to the broadband properties of the magnetic field (e.g. Pulse-Width-Modulation(PWM), multi-harmonic excitation), the direct structural excitation in the form of magnetic forces is also broadband.
Technical Paper

Modeling of Reactive Spray Processes in DI Diesel Engines

2017-03-28
2017-01-0547
Commonly, the spray process in Direct Injection (DI) diesel engines is modeled with the Euler Lagrangian discrete droplet approach which has limited validity in the dense spray region, close to the injector nozzle hole exit. In the presented research, a new reactive spray modelling method has been developed and used within the 3D RANS CFD framework. The spray process was modelled with the Euler Eulerian multiphase approach, extended to the size-of-classes approach which ensures reliable interphase momentum transfer description. In this approach, both the gas and the discrete phase are considered as continuum, and divided into classes according to the ascending droplet diameter. The combustion process was modelled by taking into account chemical kinetics and by solving general gas phase reaction equations.
Technical Paper

Modeling of the System Level Electric Drive using Efficiency Maps Obtained by Simulation Methods

2014-04-01
2014-01-1875
This work presents a physical model that calculates the efficiency maps of the inverter-fed Permanent Magnet Synchronous Machine (PMSM) drive. The corresponding electrical machine and its controller are implemented based on the two-phase (d-q) equivalent circuits that take into account the copper loss as well as the iron loss of the PMSM. A control strategy that optimizes the machine efficiency is applied in the controller to maximize the possible output torque. In addition, the model applies an analytical method to predict the losses of the voltage source inverter. Consequently, the efficiency maps within the entire operating region of the PMSM drive can be derived from the simulation results, and they are used to represent electric drives in the system simulation model of electric vehicles (EVs).
Technical Paper

Modelling the Knocking Combustion of a Large Gas Engine Considering Cyclic Variations and Detailed Reaction Kinetics

2014-10-13
2014-01-2690
The combustion efficiency of large gas engines is limited by knocking combustion. Due to fact that the quality of the fuel gas has a high impact on the self-ignition of the mixture, it is the aim of this work to model the knocking combustion for fuel gases with different composition using detailed chemistry. A cycle-resolved knock simulation of the fast burning cycles was carried out in order to assume realistic temperatures and pressures in the unburned mixture Therefore, an empirical model that predicts the cyclic variations on the basis of turbulent and chemical time scales was derived from measured burn rates and implemented in a 1D simulation model. Based on the simulation of the fast burning engine cycles the self-ignition process of the unburned zone was calculated with a stochastic reactor model and correlated to measurements from the engines test bench. A good agreement of the knock onset could be achieved with this approach.
Technical Paper

New Fuel Mass Flow Meter - A Modern and Reliable Approach to Continuous and Accurate Fuel Consumption Measurement

2000-03-06
2000-01-1330
Over the past few years, the fuel mass measurement gained in importance to record the consumed fuel mass and the specific fuel consumption [g/kWh] with high accuracy. Measuring instruments, such as positive displacement meters, methods based on the burette or the Wheatstone bridge mass flow meter measure either the volumetric flow and a temperature-dependant fuel density correction is necessary or they have old technology and therefore poor accuracy and repeatability. A new-generation Coriolis sensor featuring an ideal measurement range for engine test beds but still with flow depending pressure drop has been integrated in a fuel meter to ensure that no influence is given to the engine behaviour for example after engine load change. The new Coriolis meter offers better accuracy and repeatability, gas bubble venting and easy test bed integration. For returnless fuel injection systems the fuel system supplies the fuel pressure.
Technical Paper

Simulation and Application of Lightweight Damping Sandwich Material for I.C. Engines

2018-06-13
2018-01-1565
Making lighter engines is in the agenda of all OEMs in order to make their cars lighter and to reduce CO2 emission based on regulations. On the other hand, the noise regulations are getting more stringent and the customer impression of interior sounds is still an important aspect in vehicle development. Vehicle noise legislation has been revised numerous times since it was first established in February 1970. The latest revision in EU legislation introduces a revised test method which is used to enforce diminishing noise limits in three phases (EU Regulation No. 540/2014). Since 2016 the noise limit for passenger cars has been 72 dB(A). It will be reduced to 70 dB(A) in 2020 and to 68 dB(A) in 2024. These vehicle pass by noise limits cascade down to limitations on engine noise. New engine designs face a trade-off between a lightweight design and fulfilling the NVH targets. The conventional design updates are done by adding ribs and usually mass to the engine.
Journal Article

Synergetic DOC-DPF System Optimization Using Advanced Models

2017-01-10
2017-26-0121
Modern ‘DOC-cDPF’ systems for diesel exhaust are employing Pt-, Pd- as well as Pt/Pd alloy- based coatings to ensure high conversion efficiency of CO, HC even at low temperatures. Depending on the target application, these coatings should be also optimized towards NO2 generation which is involved in low temperature soot oxidation as well as in SCR-based deNOx. Zeolite materials are also frequently used to control cold-start HC emissions. Considering the wide variety of vehicles, engines and emission targets, there is no single optimum coating technology. The main target is therefore to maximize synergies rather than to optimize single components. At the same time, the system designer has nowadays a wide range of technologies to choose from, including PGM alloyed combinations (Pt/Pd), multiple layers and zones applicable to both DOCs and DPFs.
Journal Article

The Damage Operator Approach: Fatigue, Creep and Viscoplasticity Modeling in Thermo-Mechanical Fatigue

2011-04-12
2011-01-0485
In the last decades the development time of vehicles has been drastically reduced due to the application of advanced numerical and experimental methods. Specifications concerning durability and other functional attributes for every new model improve for every vehicle. In particular, for machines and components under variable multiaxial loading, fatigue evaluation is one of the most important steps in the design process. Appropriate material testing and simulation is the key to efficient life prediction. However, the life of automotive components, power plants and other high-temperature facilities depends mostly on thermo-mechanical fatigue (TMF). This is due to the normally variable service conditions, which contain the phases of startup, full load, partial load and shut-down.
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