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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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Reduced Model of a Vehicle Cabin for Transient Thermal Simulation

Daimler AG-Wolfgang Roessner
FKFS-David Klemm, Nils Widdecke, Jochen Wiedemann
Published 2018-05-30 by SAE International in United States
In the proposed work the transient thermal modeling of a vehicle cabin has been performed. Therefore, a reduced model has been developed based on a one-node discretization of the cabin air. The conduction in the solid parts is accounted for by a one-dimensional heat transfer approach, the radiation exchange between the surfaces is based on view factors adopted from a 3D reference and the convective heat transfer from the cabin surfaces to the cabin air is conducted with the help of heat transfer coefficients calculated in a 3D reference simulation. The cabin surface is discretized by planar wall elements, including the outer shell of the cabin and inner elements such as seats. Each wall element is composed of several homogeneous material layers with individual thicknesses. Investigations have been conducted on the temporal and spatial resolution of the layer structure of these wall elements, for the 3D model as well as for the reduced one. The cabin air is discretized as one thermal mass, which acts as a reference temperature for both the convective heat fluxes…
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Investigation of the Disc Deflection Behavior of Shim Valves in Vehicle Shock Absorbers

Daimler AG-Timo Hofmann, Tobias Brenner
Brandenburg University of Technology-Dieter Bestle
Published 2018-04-03 by SAE International in United States
Todays tuning of hydraulic vehicle shock absorbers is mainly an empirical iterative process performed in time-consuming and expensive ride tests, whereas the majority of damper simulation models used for investigating vehicle ride behavior is based on an abstract parameterization. For the manufacturing of automotive dampers, however, the valve code is essential. Minor changes in the valve code describing the shim stack in the hydraulic valves may have a noticeable impact on the damper characteristics, while the physical effects are still not sufficiently understood. Therefore, the paper presents a detailed physics-based structural model to investigate the pressure-deflection behavior of shim stacks and the influence of specific discs in the stack. The model includes a variety of effects like friction and preload, and is capable to predict the damper characteristics. The modeling approach has no limitations on geometric quantities like disc diameter and thickness or the number of discs. Short computational time, fully automated preprocessing, simulation and post processing may reduce the time for damper tuning drastically, enable investigations of tolerance influence on damper forces or application…
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Development of a LIF-Imaging System for Simultaneous High-Speed Visualization of Liquid Fuel and Oil Films in an Optically Accessible DISI Engine

Daimler AG-Torben Mueller, Stefan Wigger, Hans-Juergen Fuesser
University of Duisburg Essen-Sebastian Kaiser
Published 2018-04-03 by SAE International in United States
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. Both the laser and the cameras were capable of kHz repetition rates. Preliminary studies in a thin-film cuvette investigated the optical properties of tracer/fuel-mixtures and mixtures with a first-fill engine oil…
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Steady-State Experimental and Meanline Study of an Asymmetric Twin-Scroll Turbine at Full and Unequal and Partial Admission Conditions

Daimler AG-Torsten Palenschat, Markus Mueller
Imperial College London-Peter Newton, Ricardo Martinez-Botas
Published 2018-04-03 by SAE International in United States
The use of twin-scroll turbocharger turbines has gained popularity in recent years. The main reason is its capability of isolating and preserving pulsating exhaust flow from engine cylinders of adjacent firing order, hence enabling more efficient pulse turbocharging. Asymmetrical twin-scroll turbines have been used to realize high pressure exhaust gas recirculation (EGR) using only one scroll while designing the other scroll for optimal scavenging. This research is based on a production asymmetrical turbocharger turbine designed for a heavy duty truck engine of Daimler AG. Even though there are number of studies on symmetrical twin entry scroll performance, a comprehensive modeling tool for asymmetrical twin-scroll turbines is yet to be found. This is particularly true for a meanline model, which is often used during the turbine preliminary design stage. This study presents the development of a generalized meanline model for a twin-scroll turbine, which can be used in the early design stages, concentrating on asymmetrical scrolls. The improvements from the previous meanline model, i.e., the inlet duct and interspace model, in order to enable asymmetrical scroll…
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Wall Heat Transfer in a Multi-Link Extended Expansion SI-Engine

Daimler AG-Morris Langwiesner, Christian Krueger, Sebastian Donath
University of Stuttgart-Michael Bargende
Published 2017-09-04 by SAE International in United States
The real cycle simulation is an important tool to predict the engine efficiency. To evaluate Extended Expansion SI-engines with a multi-link cranktrain, the challenge is to consider all concept specific effects as best as possible by using appropriate submodels. Due to the multi-link cranktrain, the choice of a suitable heat transfer model is of great importance since the cranktrain kinematics is changed. Therefore, the usage of the mean piston speed to calculate a heat-transfer-related velocity for heat transfer equations is not sufficient. The heat transfer equation according to Bargende combines for its calculation the actual piston speed with a simplified k-ε model.In this paper it is assessed, whether the Bargende model is valid for Extended Expansion engines. Therefore a single-cylinder engine is equipped with fast-response surface-thermocouples in the cylinder head. The surface heat flux is calculated by solving the unsteady heat conduction equation. By using a surface-ratio related weighting method, it is possible to determine a global wall heat loss from the local heat fluxes.The natural-gas test engine has a multi-link cranktrain to achieve, based…
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