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Potential Analysis and Virtual Development of SI Engines Operated with Synthetic Fuel DMC+

FKFS-Cornelius Wagner, Michael Grill, Mahir-Tim Keskin
FKFS / University of Stuttgart-Michael Bargende
  • Technical Paper
  • 2020-01-0342
To be published on 2020-04-14 by SAE International in United States
On the way to emission-free mobility, future fuels must be CO2 neutral. To achieve this, synthetic fuels are being developed. In order to better assess the effects of the new fuels on the engine process, simulation models are being developed that reproduce the chemical and physical properties of these fuels. In this paper, the fuel DMC+ is examined. DMC+ (a mixture of DMC and MeFo mainly, characterized by the lack of C-C Bonds and high oxygen content) offers advantages with regard to evaporation heat, demand of oxygen and knock resistance. Furthermore, its combustion is almost particle free. With the aid of modern 0D/1D-Simulation methods, an assessment of the potential of DMC+ can be made. It is shown that the simulative conversion of a state-of-the-art gasoline engine to DMC+ (a mixture of DMC and MeFo mainly, characterized by the lack of C-C Bonds and high oxygen content) fuel offers advantages in terms of efficiency in many operating points even if the engine design is not altered. This is mainly due to the higher knock resistance and…
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Investigation of Transient Aerodynamic Effects on Public Highways in Comparison to Individual Driving Situations on a Test Site

FKFS-Felix Wittmeier, Andreas Wagner, Jochen Wiedemann
German Aerospace Center (DLR)-Henning Wilhelmi, Andreas Dillmann
  • Technical Paper
  • 2020-01-0670
To be published on 2020-04-14 by SAE International in United States
Natural wind, roadside obstacles, terrain roughness, and traffic can influence the incident flow of a vehicle driven on public roads. These on-road conditions differ from the idealized statistical steady-state flow environment utilized in CFD simulations and wind tunnel experiments. To understand these transient on-road conditions better, measurements were taken on a test site and on German Autobahn, resulting in the characterization of the transient aerodynamic effects around a vehicle. A compact car was equipped with a measurement system that is capable of determining the transient airflow around the vehicle and the vehicle’s actual driving state. This vehicle was driven several times on a fixed route to investigate different traffic densities on public highways in southern Germany. The tests were conducted under consistent weather conditions and average wind velocities of 2-5 m/s. During the tests the transient incident flow and pressure distribution on the vehicle surface were measured. With the same vehicle, individual driving situations were recreated on a test site. This paper presents a comparison of the aerodynamic characteristics measured by the vehicle during a…
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In The Wake of Others: Unsteady Bonnet Surface Pressure Predictions and Measurements

FKFS-Oliver Beland
Dassault Systemes-Joaquin Gargoloff, Jonathan Jilesen
  • Technical Paper
  • 2020-01-0676
To be published on 2020-04-14 by SAE International in United States
In use cars often drive through the wakes of other vehicles. It has long been appreciated that this imposes a fluctuating onset flow which can excite a structural response in vehicle panels, particularly the bonnet. This structure must be designed to be robust to such excitation to guarantee structural integrity and maintain customer expectations of quality. As we move towards autonomous vehicles and exploit platoons for drag reduction, this onset flow condition merits further attention. The work reported here comprises both measurements and simulation capturing the unsteady pressure distribution over the bonnet of an SUV following a similar vehicle at both high speed and in relatively close proximity. Measurements were taken during track testing and include 48 static measurement locations distributed over the bonnet where the unsteady static pressures were recorded. This is complemented by computational fluid dynamics simulations using a commercially available Lattice-Boltzmann based Very Large Eddy Simulation approach. Comparisons between experiment and simulation are based on both time-averaged static pressure coefficients and spectra. This provides a dataset that includes both time-averaged and unsteady…
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Virtual Development of Injector Spray Targeting by Coupling 3D-CFD Simulations with Optical Investigations

FKFS-Marco Chiodi
University of Stuttgart-Antonino Vacca, Simon Hummel, Karsten Müller, Marc Reichenbacher, Michael Bargende
  • Technical Paper
  • 2020-01-1157
To be published on 2020-04-14 by SAE International in United States
Further improvements of internal combustion engines to reduce fuel consumption and to face future legislation constraints are strictly related to the study of mixture formation, in order to supply the engine with homogeneous charge, towards the direction of a global stoichiometric blend in the combustion chamber. Fuel evaporation and thus mixture quality, mostly depend on injector atomization features and charge motion within the cylinder. 3D-CFD simulations offer great potential to study not only injector atomization quality but also the evaporation behavior. Nevertheless coupling optical measurements and simulations for injector analysis is an open discussion because of the large number of influencing parameters and interactions affecting the fuel injections reproducibility. For this reason, detailed numerical investigations are used to describe the injection phenomena. For a virtual development of internal combustion engines this intensive calculations are not advisable but it is rather reasonable to find a methodology for a numerical characterization of the fuel injection process that takes into account macroscopic spray properties and to integrate these models into the complete engine simulations. Based on these concepts…
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A Quasi-Dimensional SI Burn Rate Model for Predicting the Effects of Changing Fuel, Air-Fuel-Ratio, EGR and Water Injection

FKFS-Michael Grill
IVK, University of Stuttgart-Sebastian Hann, Michael Bargende
  • Technical Paper
  • 2020-01-0574
To be published on 2020-04-14 by SAE International in United States
As a result of the shifted R&D focus from internal combustion engines to electrified powertrains, resources for the development of internal combustion engines are restricted more and more. With that, the importance of highly efficient engine development tools is increased. In this context, 0D/1D engine simulation offers the advantage of low computational effort and fast engine model set-up. To ensure a high predictive ability of the engine simulation, a reliable combustion model is needed. Considering the increasing interest in alternative fuels, the aspect of predicting the fuel influence on combustion is of special importance. To reach these targets, the change of engine combustion characteristics with changing fuels and changing air-fuel-ratios is investigated systematically in a first step. For this purpose, engine test bed data is compared with expected fuel-dependent flame wrinkling trends based on Markstein / Lewis-number theory. Furthermore, the possibility of influences caused by the Darrieus-Landau instability is evaluated. Based on these comparisons, an existing combustion model is improved by adapting the sub-models for laminar and turbulent flame speed as well as the approach…
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A Phenomenological Homogenization Model Considering Direct Fuel Injection and EGR for SI Engines

FKFS-Michael Grill
IAV GmbH-Oliver Dingel
  • Technical Paper
  • 2020-01-0576
To be published on 2020-04-14 by SAE International in United States
As a consequence of reduced fuel consumption, direct injection gasoline engines have already prevailed against port fuel injection. However, in-cylinder fuel homogenization strongly depends on charge motion and injection strategies and can be challenging due to the reduced available time for mixture formation. An insufficient homogenization has generally a negative impact on the combustion and therefore also on efficiency and emissions. In order to reach the targets of the intensified CO2 legislation, further increase in efficiency of SI engines is essential. In this connection, 0D/1D simulation is a fundamental tool due to its applica-tion area in an early stage of development and its relatively low computational costs. Certainly, inhomogeneities are still not considered in quasi dimensional combustion models because the prediction of mixture formation is not included in the state of the art 0D/1D simulation. Therefore, a phenomenological homogenization model has been developed in this work based on 3D CFD simulations. The model is based on a finite volume approximation of the 2D convection diffusion equation rep-resenting the in-cylinder flow field. The velocity field is…
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Simulation of Transient On-Road Conditions in a Closed Test Section Wind Tunnel using a Wing System with Active Flaps

FKFS-Andreas Wagner, Jochen Wiedemann
German Aerospace Center DLR-Henning Wilhelmi, James Bell, Daniela Heine, Claus Wagner
  • Technical Paper
  • 2020-01-0688
To be published on 2020-04-14 by SAE International in United States
There is a high interest to improve the static approach of wind tunnel testing by simulating realistic transient flow conditions. To determine these conditions, different driving maneuvers (driving behind, passing) were conducted in previous experiments on a runway. The transient, incoming flow and the vehicle’s surface pressure were measured. To create the realistic inflow conditions in a wind tunnel, a new system of four symmetric airfoils with active flaps was developed for the Side-Wind Facility Göttingen (SWG), a closed loop, closed test-section facility with a moving belt and suction system. The airfoils heights are half the test section’s height and the trailing third of their chords are active flaps. The reduced inertia - resulting from only one third of the airfoil moving - allows for individual high-speed, rotational movements of the flap at with up to 50 Hz and angles of up to ±20°. Time-resolved velocity component measurements in the empty test section were conducted with an array of eleven 5-hole probes connected to an ESP64HD pressure transducer system for various flap configurations. These measurements…
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The Application of E-Fuel Oxymethylene Ether OME1 in a virtual Heavy-Duty Diesel Engine for ultra-low Emissions

FKFS-Michael Grill
Universitat Stuttgart-Qirui Yang, Michael Bargende
  • Technical Paper
  • 2020-01-0349
To be published on 2020-04-14 by SAE International in United States
For long haul transport, diesel engine due to its low fuel consumption and the low operating costs will remain dominant over the long term. In order to achieve CO2 neutrality, the use of electricity-based, synthetic fuels (e-fuels) provides a solution. Especially the group of oxymethylene ethers (OME) is considered promising for its soot-free combustion. The new fuel properties and combustion characteristics place new demands on engine design and also open up new degrees of freedom to operate diesel engines. In this work, the effects of dimethoxymethane (OME1) were investigated by means of 1D simulation at three different operating points on a virtual truck diesel engine. The subsystems of fuel injection, air path and exhaust gas were sequentially adjusted for the purpose of low emissions, especially low nitrogen oxides (NOx). Thanks to the inexistent soot-NOx trade-off, NOx can be considerably reduced using high exhaust gas recirculation (EGR) for a nearly stoichiometric operation, without compromising power output. Conceivable configurations of exhaust aftertreatment system were analyzed. At last, a holistic layout of a future OME-powered engine was proposed.
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Experimental Investigation of Automotive Vehicle Transient Aerodynamics with a Reduced-Scale Moving-Model Crosswind Facility

FKFS-Andreas Wagner, Jochen Wiedemann
German Aerospace Center (DLR)-James R. Bell, Henning Wilhelmi, Daniela Heine, Klaus Ehrenfried, Claus Wagner
  • Technical Paper
  • 2020-01-0671
To be published on 2020-04-14 by SAE International in United States
Automotive vehicles operate in complex, transient aerodynamic conditions that can potentially influence operational efficiency, performance and safety. A moving-model facility combined with a wind-tunnel is an experimental methodology that can be utilized to model some of these transient aerodynamic conditions. This methodology is an alternative to wind-tunnel experiments with actively yawing models or active flaps, and has the added benefit of modelling the correct relative motion between the vehicle and the ground/infrastructure. Experiments were performed at the moving-model facility at DLR, Göttingen. A 1:10 scale VW Golf 7 (geometry provided by VW) model was equipped with 24 surface pressure taps. The model was accelerated by a hydro-pneumatic driven catapult over a 60 m long track, through a 25 m long test-section, and decelerated in a braking tank of polystyrene balls. Crosswinds were generated by a closed-loop, open-jet wind-tunnel with four 30 kW fans perpendicular to the track, 5 m long and 1 m high, with a maximum velocity of 25 m/s. The moving-model facility was adapted from its standard high-speed train configuration to a new…
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Thermal Behavior of an Electronics Compartment with Respect to Real Driving Conditions

FKFS-Adrian Bernhard, Jochen Wiedemann, Nils Widdecke, Andreas Wagner
Daimler AG-Heinrich Reister, Thomas Binner
  • 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…