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Technical Paper

A Numerical Methodology to Compute Temperatures of a Rotating Cardan Shaft

2013-04-08
2013-01-0843
In this paper a new numerical methodology to compute component temperatures of a rotating cardan shaft is described. In general temperatures of the cardan shaft are mainly dominated by radiation from the exhaust gas system and air temperatures in the transmission tunnel and underbody. While driving the cardan shaft is rotating. This yields a uniform temperature distribution of the circumference of the shaft. However most simulation approaches for heat protection are nowadays steady-state computations. In these simulations the rotation of the cardan shaft is not considered. In particular next to the exhaust gas system the distribution of the temperatures of the cardan shaft is not uniform but shows hot temperatures due to radiation at the side facing the exhaust gas system and lower temperatures at the other side. This paper describes a new computational approach that is averaging the radiative and convective heat fluxes circumferentially over bands of the cardan shaft.
Journal Article

An Experimental Methodology for Measuring of Aerodynamic Resistances of Heavy Duty Vehicles in the Framework of European CO2 Emissions Monitoring Scheme

2014-04-01
2014-01-0595
Due to the diversity of Heavy Duty Vehicles (HDV), the European CO2 and fuel consumption monitoring methodology for HDVs will be based on a combination of component testing and vehicle simulation. In this context, one of the key input parameters that need to be accurately defined for achieving a representative and accurate fuel consumption simulation is the vehicle's aerodynamic drag. A highly repeatable, accurate and sensitive measurement methodology was needed, in order to capture small differences in the aerodynamic characteristics of different vehicle bodies. A measurement methodology is proposed which is based on constant speed measurements on a test track, the use of torque measurement systems and wind speed measurement. In order to support the development and evaluation of the proposed approach, a series of experiments were conducted on 2 different trucks, a Daimler 40 ton truck with a semi-trailer and a DAF 18 ton rigid truck.
Technical Paper

Ash Transport in Diesel Particle Filters

2012-09-10
2012-01-1732
Lubricant oil derived ash deposits still represent a major issue in diesel particulate filter operation in vehicles. In literature various ash deposition patterns are described. The two boundary deposition patterns are (a) wall layer and (b) filling at the back end of the inlet channels. The patterns are often associated with different regeneration methods. Continuous regeneration is supposed to result in a homogeneous ash layer, whereas periodic (active) regeneration is reported to result in back end filling. The current contribution describes the basic mechanisms associated with ash transport phenomena in particle filters. On the basis of (a) frequency of ash exposure to flow (b) ash particle structure re-entrainment and finally (c) axial ash transport the different deposition pattern can be explained. Exposure to flow accomplished by periodical soot removal, either by passive or active regeneration is the first step.
Technical Paper

BLUETEC Diesel Technology - Clean, Efficient and Powerful

2008-04-14
2008-01-1182
Diesel engines have a strong contribution to the CO2 reduction in Europe in the past years. To enable these C02 reduction potential to the US market Mercedes Benz developed the BLUETEC technology for light duty diesel engines. The BLUETEC technology contains an optimized diesel engine and combustion system, an aftertreatment system with DOC, DPF and an active SCR catalyst with AdBlue Dosing System and an enhanced ECU functionality and calibration. For fulfilling the world strongest emission limits of the US legislation there have to be solutions developed for the handling of AdBlue under cold climate below -11°C, managing the refilling event, and the onboard diagnostic. To ensure the emission stability over full useful life on high NOx conversions level, intensive testing of the catalyst technology had to be done. In addition there are self learning functionalities for adapting the dosing strategy to ensure the maximum NOx performance.
Technical Paper

Bluetec Emission Control System for the US Tier 2 Bin 5 Legislation

2008-04-14
2008-01-1184
While the market share for diesel engines for LD vehicles in Europe has grown continuously in the past years, the market share in North America is still negligible. Until now, it has been possible to fulfill the limits for nitrogen oxides (NOx) both in Europe and in North America by engine measures alone, without using an active NOx aftertreatment system. With the introduction of Tier II Bin 8 and Tier II Bin 5 emissions legislation in the US in 2007, most new diesel applications will now require NOx aftertreatment. One of the possible technologies for the reduction of nitrogen oxides in lean exhaust gas is the NOx storage catalyst which has become the generally-accepted choice for engines with gasoline direct injection systems and which is also utilized in the current diesel Bluetec I systems from Daimler. For heavier applications urea-SCR is the preferred technology to fulfill NOx legislation limits.
Technical Paper

Challenges for the Next Generation of BlueTEC Emission Technology

2011-04-12
2011-01-0294
Mercedes-Benz BlueTEC passenger cars have been on the cutting edge of clean diesel technology since 2006. These BlueTEC vehicles furthermore passed millions of kilometers in the hands of customers. SCR-equipped passenger cars already meet the most stringent exhaust emissions standards in international markets such as the USA, Europe and Japan. Diesel engines with BlueTEC technology also reduce CO₂ emissions and provide the high torque and performance associated with the diesel engine in addition to keeping exhaust emissions at the lowest possible level. Nowadays the requirements for SCR emission concepts are increasing continuously. In fact the emission legislation is getting stricter with the LEVIII emission standards in 2015. Additionally the requirements and effort for on-board diagnosis are increasing year after year. In combination with ambitious CO₂ targets all these issues constitute the further challenges of BlueTEC SCR emission concepts for worldwide markets.
Video

Challenges in Automotive Electrification and Powertrain Component Development

2011-11-07
An overview of Daimler?s progression to advance powertrain technology in a growth industry shows many different solutions to improvement in transportation. Daimler continues to make breakthroughs in technology development and application building on 125 years of automotive development. Optimization of current powertrains will enable a significant gain in CO2/mi reductions, that dependent on product mix can be augmented with additional technologies. There is however no bypass to some form of electrification, enabling efficiency gains and alternative forms of power supply. Development of hybrid powertrains continues in an established manner and enhanced development of further electrified powertrains are in development. Organizationally and technically, significant skills and adjustments need to continue to be undertaken enabling OEMs and in particular the supply base to develop optimized solutions efficiently. The outlook is bright for novel component development and innovation.
Journal Article

Cold Start Effect Phenomena over Zeolite SCR Catalysts for Exhaust Gas Aftertreatment

2013-04-08
2013-01-1064
NH₃/urea SCR is a very effective and widely used technology for the abatement of NOx from diesel exhaust. The SCR mechanism is well understood and the catalyst behavior can be predicted by mathematical models - as long as operation above the temperature limit for AdBlue® injection is considered. The behavior below this level is less understood. During the first seconds up to minutes after cold start, complete NOx abatement can be observed over an SCR catalyst in test bench experiments, together with a significant increase in temperature after the converter (ca. 100 K). In this work these effects have been investigated over a monolith Cu-zeolite SCR catalyst. Concentration step experiments varying NO, NO₂ and H₂O have been carried out in lab scale, starting from room temperature. Further, the interaction of C₃H₆ and CO with NOx over the SCR has been investigated.
Technical Paper

Daimler Aeroacoustic Wind Tunnel: 5 Years of Operational Experience and Recent Improvements

2018-09-24
2018-01-5038
Since 2013 the new Daimler Aeroacoustic Wind Tunnel (AAWT) is in operation at the Mercedes-Benz Technology Center in Sindelfingen, Germany. This construction was the second stage of a wind tunnel center project, which was launched in 2007 and started with the climatic wind tunnels including workshop and office areas. The AAWT features a test facility for full-scale cars and vans with a nozzle exit area of 28 m2, a five-belt system, and underfloor balance to measure forces with best possible road simulation. With a remarkable low background noise level of the wind tunnel, vehicle acoustics can be investigated under excellent conditions using high-performance measurement systems. An overview is given about the building and the design features of the wind tunnel layout. The aerodynamic and aeroacoustic properties are summarized. During the first years of operation, further improvements regarding the wind tunnel background noise and vehicle handling were made.
Technical Paper

Development of Energy Management Strategies and Analysis with Standard Drive Cycles for Fuel Cell Electric Vehicles

2012-09-10
2012-01-1609
In order to reduce fuel consumption in Fuel Cell Electric Vehicles, effective distribution of power demand between Fuel Cell and Battery is required. Energy management strategies can improve fuel economy by meeting power demand efficiently. This paper explains development of various energy management strategies for Fuel Cell Electric Vehicle with Lithium Ion Battery. Drive cycles used for optimization and analysis of the strategies are New European Drive cycles (NEDC), Japanese Drive cycles (JAP1015), City Drive cycles, Highway Drive cycles (FHDS) and Federal Urban Drive cycles (FUDS). All Fuel consumption and ageing calculations are done using backward model implemented in MATLAB/SIMULINK.
Technical Paper

Development of Universal Brake Test Data Exchange Format and Evaluation Standard

2010-10-10
2010-01-1698
Brake system development and testing is spread over vehicle manufacturers, system and component suppliers. Test equipment from different sources, even resulting from different technology generations, different data analysis and report tools - comprising different and sometimes undocumented algorithms - lead to a difficult exchange and analysis of test results and, at the same time, contributes to unwanted test variability. Other studies regarding the test variability brought up that only a unified and unambiguous data format will allow a meaningful and comparative evaluation of these data and only standardization will reveal the actual reasons of test variability. The text at hand illustrates that a substantial part of test variability is caused by a misinterpretation of data and/or by the application of different algorithms.
Technical Paper

Development of a LIF-Imaging System for Simultaneous High-Speed Visualization of Liquid Fuel and Oil Films in an Optically Accessible DISI Engine

2018-04-03
2018-01-0634
Downsizing and direct injection in modern DISI engines can lead to fuel impinging on the cylinder walls. The interaction of liquid fuel and engine oil due to fuel impinging on the cylinder wall causes problems in both lubrication and combustion. To analyze this issue with temporal and spatial resolution, we developed a laser-induced fluorescence (LIF) system for simultaneous kHz-rate imaging of fuel and oil films on the cylinder wall. Engine oil was doped with traces of the laser dye pyrromethene 567, which fluoresces red after excitation by 532 nm laser radiation. Simultaneously, the liquid fuel was visualized by UV fluorescence of an aromatic “tracer” in a non-fluorescent surrogate fuel excited at 266 nm. Two combinations of fuel and tracer were investigated, iso-octane and toluene as well as a multi-component surrogate and anisole. The fluorescence from oil and fuel was spectrally separated and detected by two cameras.
Journal Article

Durability Simulation with Chassis Control Systems: Model Depth for a Handling Maneuver

2016-09-02
2016-01-9111
This paper makes a contribution toward a more efficient chassis durability process for the development of passenger cars, in which the simulation of relevant load data is a time-consuming part. This is especially due to the full vehicle model complexity which is usually determined by the demands of rough road simulations. However, for the load calculation on a racetrack, time saving model approaches that are more simplified might be sufficient. Our investigation comprises two levels of vehicle model complexity: one with all chassis parts modeled in a multibody system environment and one characteristic curve based model in an internal simulation environment. Both approaches consider an original chassis control system as a Software-in-the-Loop model. By the evaluation of real-world experiments the main influence factors in terms of durability are demonstrated. With the help of those highly sensitive durability criteria the measurement and simulation results are then compared.
Technical Paper

Finding All Potential Run-Time Errors and Data Races in Automotive Software

2017-03-28
2017-01-0054
Safety-critical embedded software has to satisfy stringent quality requirements. All contemporary safety standards require evidence that no data races and no critical run-time errors occur, such as invalid pointer accesses, buffer overflows, or arithmetic overflows. Such errors can cause software crashes, invalidate separation mechanisms in mixed-criticality software, and are a frequent cause of errors in concurrent and multi-core applications. The static analyzer Astrée has been extended to soundly and automatically analyze concurrent software. This novel extension employs a scalable abstraction which covers all possible thread interleavings, and reports all potential run-time errors, data races, deadlocks, and lock/unlock problems. When the analyzer does not report any alarm, the program is proven free from those classes of errors. Dedicated support for ARINC 653 and OSEK/AUTOSAR enables a fully automatic OS-aware analysis.
Journal Article

Fire Fighting of Li-Ion Traction Batteries

2013-04-08
2013-01-0213
The number of full electric and hybrid electric vehicles is rapidly growing [1][2][3]. The new technologies accompanying this trend are increasingly becoming a focal point of interest for rescue services. There is much uncertainty about the right techniques to free trapped occupants after an accident. The same applies to vehicle fires. Can car fires involving vehicles with a lithium ion traction battery be handled in the same way as conventional vehicle fires? Is water the right extinguishing agent? Is there a risk of explosion? There are many unanswered questions surrounding the topic of electric vehicle safety. The lack of information is a breeding ground for rumours, misinformation and superficial knowledge. Discussions on various internet platforms further this trend. Tests were conducted on three lithium ion traction batteries, which were fuel-fired until burning on their own. The batteries were then extinguished with water, a surfactant and a gelling agent.
Technical Paper

Improved Full Vehicle Finite Element Tire Road Noise Prediction

2017-06-05
2017-01-1901
This paper presents the application to full vehicle finite element simulation of a steady state rolling tire/wheel/cavity finite element model developed in previous work and validated at the subsystem level. Its originality consists in presenting validation results not only for a wheel on a test bench, but for a full vehicle on the road. The excitation is based on measured road data. Two methods are considered: enforced displacement on the patch centerline and enforced displacement on a 2D patch mesh. Finally the importance of taking the rotation of the tire into account is highlighted. Numerical results and test track measurements are compared in the 20-300 Hz frequency range showing good agreement for wheel hub vibration as well as for acoustic pressure at the occupant’s ears.
Journal Article

Investigation of Tire-Road Noise with Respect to Road Induced Wheel Forces and Radiated Airborne Noise

2014-06-30
2014-01-2075
Low interior noise levels in combination with a comfortable sound is an important task for passenger cars. Due to the reduction of many noise sources over the last decades, nowadays tire-road noise has become one of the dominant sources for the interior noise. Especially for manufactures of luxury cars, the reduction of tire-road noise is a big challenge and therefore a central part of NVH development. The knowledge of the noise transmission behavior based on the characteristics of the relevant sources is a fundamental of a modern NVH - development process. For tire-road noise the source characteristics can be described by wheel forces and radiated airborne noise. In combination with the related vehicle transfer functions it is possible to describe the noise transmission behavior in detail. A method for estimating wheel forces and radiated airborne noise is presented.
Technical Paper

Investigation on the Performance of a Mechanistic Electric Turbocharger Model for a Vehicular Fuel Cell System

2011-08-30
2011-01-1742
The electric turbocharger is a promising type of air supply unit for future automotive fuel cell drive systems. It comprises of a centrifugal compressor, a variable geometry turbine and a permanent magnet synchronous motor assembled on a single shaft. Compared to other types of vehicular fuel cell air supplies, like for example a screw or roots compressor, it needs less installation space and has lower weight while also causing less noise and vibration. This paper presents a validated mechanistic model of the electric turbocharger. The stationary compressor model is based on a set of aerodynamic loss models with surge and stone wall line prediction capability. Similarly, the stationary variable axial turbine is a detailed station based model derived from aerodynamic losses at the turbine wheel and the stator blades. The aerodynamic losses incorporated in the compressor and the turbine models are implemented under MATLAB/Simulink and show a good correlation with the experimental data.
Technical Paper

Investigations of Spray-Induced Vortex Structures during Multiple Injections of a DISI Engine in Stratified Operation Using High-Speed-PIV

2013-04-08
2013-01-0563
Modern gasoline direct injection engines with spray-guided combustion processes require a stable and reliable fuel mixture formation as well as an optimal stratification at time of ignition. Due to the limited time for this process the temporal and spatial analysis of the in-cylinder flow field and its influence is of significant interest. The application of a piezo injector with outward opening nozzle and its capability to realize multiple injections within the compression stroke provides additional degrees of freedom for the stratified engine operation. To improve the performance of this combination a detailed knowledge of the in-cylinder flow field and its interaction with the spray propagation during and after multiple injections is essential. The flow field measurements were applied in an optical borescope single-cylinder research engine using a high-speed particle image velocimetry (HSPIV) setup.
Video

Maturity Level and Variant Validation of Mechatronic Systems in Commercial Vehicles

2011-12-05
Driver assistance systems (e.g. the emergency brake assist Active Brake Assist2, or ABA2 for short, in the Mercedes-Benz Actros) are becoming increasingly common in heavy-duty commercial vehicles. Due to the close interconnection with drivetrain and suspension control systems, the integration and validation of the functions make the most exacting demands on processes and tools involved in mechatronics development. Presenter Thomas Bardelang, Daimler AG
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