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Numerical Investigation of Tonal Noise at Automotive Side Mirrors Due to Aeroacoustic Feedback

Daimler AG-Alexander Schell, Mark Eiselt
  • Technical Paper
  • 2020-01-1514
To be published on 2020-06-03 by SAE International in United States
In addition to the typical broadband noise character of wind noise, tonal noise phenomena can be much more disruptive, regardless of the overall interior noise quality of the vehicle. Whistling sounds usually occur by flow over sharp edges and resonant gaps, but can also be caused by the feedback of sound waves with laminar boundary layers or separation bubbles and the resulting frequency-selective growth of boundary layer instabilities. Such aeroacoustic feedback can e.g. occur at the side mirror of a vehicle and one compellingly needs the coupling of acoustic and flow field. A compressible large eddy simulation (LES) is in principle suitable but one has to take care of any numerical artifacts which can disturb the entire acoustic field. This paper describes the possibility to resolve aeroacoustic feedback with a commercial 2nd/3rd order finite volume CFD code. A zonal RANS/LES approach is used to ensure a realistic flow around the exterior side mirror mounted at a Mercedes-Benz C-Class. The provided compressible LES are using non-reflecting boundary conditions in combination with a sponge zone approach to…
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Optimization of an Asymmetric Twin Scroll Volute Turbine under Pulsating Engine Boundary Conditions

Daimler AG-Torsten Palenschat, Peter Wahl, Galin Nakov, Kai Hoffmann
Imperial College London-Ricardo Martinez-Botas
  • Technical Paper
  • 2020-01-0914
To be published on 2020-04-14 by SAE International in United States
Future CO2 emission legislations require the internal combustion engine to become more efficient than ever. Of great importance is the boosting system enabling down-sizing and down-speeding. However, the thermodynamic coupling of a reciprocating internal combustion engine and a turbocharger poses a great challenge to the turbine as pulsating admission conditions are imposed onto the turbocharger turbine. This paper presents a novel approach to turbocharger turbine development developed at Daimler Truck AG, and outlines this process using the example of an asymmetric twin scroll turbocharger applied to a heavy duty truck engine application. In a first step relevant operating points are defined taking into account fuel consumption on reference routes for the target application. These operation points are transferred into transient boundary conditions imposed on the turbine. These pulsating admission conditions to the turbocharger turbine are analyzed and subsequently discretized using the method of quasi-steadiness to avoid numerically very expensive unsteady CFD simulations. Following, an automated in-house developed workflow based on a parametrized model of the entire turbine stage is introduced and described. The parametrization is…
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Thermal Behavior of an Electronics Compartment with Respect to Real Driving Conditions

Daimler AG-Heinrich Reister, Thomas Binner
FKFS-Adrian Bernhard, Jochen Wiedemann, Nils Widdecke, Andreas Wagner
  • Technical Paper
  • 2020-01-1299
To be published on 2020-04-14 by SAE International in United States
Reliability of electronic components is of increasing importance for further progress towards automated driving. Thermal ageing processes such as electromigration is one factor that can negatively affect reliability of electronics. Resulting failures are mainly depending on components’ thermal load within vehicle lifetime - called temperature collective, which is described by the temperature frequency distribution of the components. At present, the only possibility to examine the temperature collective is performed by vehicle endurance testing. Knowledge about the temperature frequency distribution in early development stages is one of the key factors to ensure electronics’ reliability in future vehicles. Vehicle Thermal Management (VTM) tools, which provide numerical simulation, allows lifetime thermal prediction in early development stages, but also challenges current VTM processes. Due to changing focus from underhood to numerous electronic compartments in vehicles, the number of simulation models has steadily increased. Since the electronics compartments are mostly located inside the vehicle cabin, common load cases such as the “Slow Uphill Drive” and the “High Speed” cannot be applied to these models. Defining new load cases for maximum…
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Performance Improvement of an Asymmetric Twin Scroll Turbocharger Turbine through Secondary Flow Injection

Daimler AG-Torsten Palenschat
Nanyang Technological University-Zheng Liu, Alessandro Romagnoli
  • Technical Paper
  • 2020-01-1011
To be published on 2020-04-14 by SAE International in United States
An efficient turbocharger turbine benefits the engine in many aspects, such as better transient response, lower 〖NO〗_x emissions and better fuel economy. The turbine performance can be further improved by injecting the secondary flow through an injector over the shroud section. The secondary flow can effectively reduce the vortex separation on the suction side and reduce associated losses. A secondary flow injection system can be integrated to a conventional turbine without affecting its original design parameters, including the rotor, volute, and back disk. Therefore, the swallowing capacity and thrust loading characteristics are kept the same as the original turbine, thereby maintaining the same turbocharger-engine matching and turbine-compressor matching. In this study, a secondary flow injection system has been developed to fit for an asymmetric double-entry turbocharger turbine, designed for a 6-cylinder heavy-duty diesel engine, aiming at reducing the brake specific fuel consumption at 1100 rpm under full-loading conditions. The shape of the flow injector is similar to a single-entry volute, but can produce the flow angle in both circumferential and meridional directions, when the flow…
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Imaging and Simulation of Oil Transport Phenomena in the Upper Piston Skirt Region

Daimler AG-Jonathan Schöler, Sebastian Schiefer, Stefan Wigger, Hans-Jürgen Füßer, Volker Lagemann
University of Duisburg-Essen-Sebastian A. Kaiser
  • Technical Paper
  • 2019-01-2359
Published 2019-12-19 by SAE International in United States
The oil transport phenomena in the chamfer beneath the oil control ring of a piston in a motored engine were investigated with a combined experimental-numerical approach. High-speed laser-induced fluorescence was used to visualize the oil distribution crank-angle-resolved on both thrust side and anti-thrust side of an optically accessible single cylinder engine. Corresponding three-dimensional volume-of-fluid CFD simulations were calibrated with the experiment and then utilized to analyze the cross sectional flows in the chamfer. Phenomena triggered by inertial forces and the lateral piston motion, e.g. oil transport from the piston to the liner (bridging) and the formation of a circular flow in the chamfer, are described in detail.
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Energetic Costs of ICE Starts in (P)HEV - Experimental Evaluation and Its Influence on Optimization Based Energy Management Strategies

Daimler AG-Lukas Engbroks, Pascal Knappe, Daniel Goerke, Stefan Schmiedler, Tobias Goedecke
Vienna University of Technology-Bernhard Geringer
Published 2019-09-09 by SAE International in United States
The overall efficiency of hybrid electric vehicles largely depends on the design and application of its energy management system (EMS). Despite the load coordination when operating the system in a hybrid mode, the EMS accounts for state changes between the different driving modes. Whether a transition between pure electric driving and internal combustion engine (ICE) powered driving is beneficial depends, among others, on the respective operation point, the route ahead as well as on the energetic expense for the engine start itself. The latter results from a complex interaction of the powertrain components and has a tremendous impact on the efficiency and quality of EMSs. Optimization based methods such as dynamic programming serve as benchmark for the design process of rule based control strategies. In case no energetic expenses are assigned to a state change, the resulting EMS suffers from being sub-optimal regarding the fuel consumption. However, an exact determination of such engine start costs has hardly been researched, yet leads to a more efficient EMS.This paper focuses on the experimental evaluation of the energetic…
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Possibilities of Wall Heat Transfer Measurements at a Supercharged Euro VI Heavy-Duty Diesel Engine with High EGR-Rates, an In-Cylinder Peak Pressure of 250 Bar and an Injection Pressure up to 2500 Bar

Daimler AG-Christian Hennes, Jürgen Lehmann
KIT Karlsruhe Institute Of Technology-Thomas Koch
Published 2019-09-09 by SAE International in United States
A raise of efficiency is the strongest selling point concerning the total cost of ownership (TCO), especially for commercial vehicles (CV). Accompanied by legislations, with contradictive development demands, satisfying solutions have to be found. The analysis of energy losses in modern engines shows three influencing parameters. Wall heat transfer (WHT) losses are awarded with the highest optimization potential.Critical for the occurrence of these losses is the WHT, which can be described by representing coefficients. To reduce WHT accompanying losses a decrease of energy transfer between combustion gas and combustion chamber wall is necessary. A measurement of heat fluxes is necessary to determine the WHT relations of the combustion chamber in an engine. As this has not been done for a Heavy-Duty (HD) engine, with peak pressures up to 250 bar, an increased in-cylinder turbulence and high exhaust gas recirculation (EGR)-rates before, it is presented in the following.Different methods to determine wall heat flux, as well as data transfer variants for data measured at the piston, are presented and compared. The non-integer system identification method (NISI)…
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How to Model Real-World Driving Behavior? Probability-Based Driver Model for Energy Analyses

Daimler AG-Tobias Schuermann, Tobias Goedecke, Stefan Schmiedler, Daniel Goerke
University of Applied Sciences Esslingen-Kai André Boehm
Published 2019-04-02 by SAE International in United States
A wide variety of applications such as driver assistant and energy management systems are researched and developed in virtual test environments. The safe testing of the applications in early stages is based on parameterizable and reproducible simulations of different driving scenarios. One possibility is modeling the microscopic driving behavior to simulate the longitudinal vehicle dynamics of individual vehicles. The currently used driver models are characterized by a conflict regarding comprehensibility, accuracy and calibration effort. Due to the importance for further analyses this conflict of interests is addressed by the presentation of a new microscopic driver model in this paper. The proposed driver model stores measured driving behaviors with its statistical distributions in maps. Thereby, the driving task is divided into free flow, braking in front of stops and following vehicles ahead. This makes it possible to display the driving behavior in its entirety. The comprehensibility of this driver model is given by its simplicity and the calibration effort is low with existing measurement data. These data are recorded with a testing vehicle by a map-…
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Development of the TOP TIERTM Diesel Standard

Daimler AG-Daniel Kozub
Center For Quality Assurance-Michael Kunselman
Published 2019-04-02 by SAE International in United States
The TOP TIERTM Diesel fuel standard was first established in 2017 to promote better fuel quality in marketplace to address the needs of diesel engines. It provides an automotive recommended fuel specification to be used in tandem with regional diesel fuel specifications or regulations. This fuel standard was developed by TOP TIERTM Diesel Original Equipment Manufacturer (OEM) sponsors made up of representatives of diesel auto and engine manufacturers. This performance specification developed after two years of discussions with various stakeholders such as individual OEMs, members of Truck and Engine Manufacturers Association (EMA), fuel additive companies, as well as fuel producers and marketers. This paper reviews the major aspects of the development of the TOP TIERTM Diesel program including implementation and market adoption challenges. Various fuel properties of concerns from OEMs perspective are discussed, and details of the TOP TIER TM Diesel standard, including the test methods and corresponding limits, are described.
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Daimler Aeroacoustic Wind Tunnel: 5 Years of Operational Experience and Recent Improvements

Daimler AG-Ralph Buckisch, Berthold Schwartekopp, Juergen Pfisterer
Published 2018-09-24 by SAE International in United States
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. Changes in the surface of the contraction and the reduction of rough surfaces in the test section reduced the self-noise of the wind tunnel. For the standard test section configuration…
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