Stuttgart Mühlhausen, Germany
Stuttgart Mühlhausen, Germany

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De Jong A.T.,Technical University of Delft | Bijl H.,Technical University of Delft | Hazir A.,FKFS | Wiedemann J.,FKFS
Journal of Sound and Vibration | Year: 2013

The present investigation focuses on simulation of the aero-acoustic resonance of partially covered cavities with a width much larger than their length or depth, that represent simplified door and trunk lid gaps. These cavities are under influence of a low Mach number flow with a relatively thick boundary layer. Under certain conditions, flow-induced acoustic resonance can occur. The requirements to simulate the resonance behavior using a Lattice Boltzmann method (LBM) model are investigated. Special focus is put on the effect of simulation spanwise width and inflow conditions. In order to validate the simulations, experiments have been conducted on simplified geometries. The configuration consists of a partially covered, rectangular cavity geometry 32×50×250 mm3 in size, with opening dimensions of 8×250 mm. Cavity flow induced acoustic response is measured with microphones at different spanwise locations inside the cavity. Hot-wire measurements are performed to quantify the boundary layer characteristics. Furthermore, high speed time resolved particle image velocimetry is used to capture the instantaneous velocity field around the opening geometry. Flow simulations show that the turbulent fluctuation content of the boundary layer is important to correctly simulate the flow induced resonance response. A minimum simulation spanwise width is needed to show good resemblance with experimental cavity pressure spectra. When a full spanwise width simulation is employed, base mode and higher modes are retrieved. © 2012 Elsevier Ltd.


Freuer A.,FKFS | Reuss H.-C.,FKFS
SAE International Journal of Alternative Powertrains | Year: 2013

This paper presents an autonomous cruise control for battery electric vehicles. The presented approach is based on the usage of predictive route data which is extracted out of a digital map and a wide range radar system in order to capture vehicles in front. By using the predictive route data and the information of the radar system, the autonomous cruise control can control the vehicle's speed over a wide range of driving situations without any driver interaction. The main aim of the presented autonomous cruise control is to optimize the battery electric vehicle's energy consumption. The main idea is to use predictive route data in order to calculate a consumption optimal vehicle speed trajectory by means of online optimization. The benefits of the autonomous cruise control are shown by means of real test drives and measured data evaluation. Also, this paper gives an outlook how energy consumption can be further optimized by using an automatic transmission in the battery electric vehicle in combination with a predictive gear selection strategy. Copyright © 2013 SAE International.


Wolany A.,University of Stuttgart | Glahn C.,Development Engineering International | Berner H.-J.,FKFS | Bargende M.,University of Stuttgart
SAE Technical Papers | Year: 2016

For scavenging the combustion chamber during the gas exchange, a temporary positive pressure gradient between the intake and the exhaust is required. On a single-scroll turbocharged four cylinder engine, the positive pressure gradient is not realized by the spatial separation of the exhaust manifold (twin-scroll), but by the use of suitable short exhaust valve opening times. In order to avoid any influence of the following firing cylinder onto the ongoing scavenging process, the valve opening time has to be shorter than 180 °CA. Such a short valve opening time has both, a strong influence on the gas exchange at the low-end torque and at the maximum engine power. This paper analyzes a phenomenon, which occurs due to short exhaust valve opening durations and late valve timings: A repeated compression of the burned cylinder charge after the bottom dead center, referred to as "recompression" in this paper. By means of a new energetic analysis (available technical work capacity) the energetic contribution of the recompression to the boost pressure generation has been examined and is presented in this paper. Furthermore two different variable exhaust valve train systems in combination with a part-scroll-separation exhaust manifold are compared in this paper. The aim is to reduce fuel consumption at the nominal power. The two exhaust valve train systems increase the valve opening duration by either a two step system or by a system with the ability to offset the valve timing. It is shown in simulation results how both systems in combination with a prolonged part-scroll-separation in the exhaust manifold reach a potential to reduce fuel consumption up to 10 %. © Copyright 2016 SAE International.


Chiodi M.,FKFS | Ferrari A.,FKFS | Mack O.,FKFS | Bargende M.,FKFS | Wichelhaus D.,Volkswagen AG
SAE Technical Papers | Year: 2011

Until a few years ago the discussion of reduction of CO2- emissions was completely out of place in motorsports. Nowadays, also in this field, car manufacturers want to investigate different approaches towards a more responsible and sustainable concept. For this target an interesting and feasible solution is the use of methane as an alternative fuel. At the 2009 edition of the 24-hour endurance race of the Nürburgring the Volkswagen Motorsport GmbH, in addition to vehicles powered by gasoline engines, introduced two vehicles powered by turbo-charged CNG engines. The aim was to prove that also an "environment-friendly" concept is able to provide the required efficiency, dynamic and reliability for a successful participation in motorsports. After the success in the 2009 edition the engagement has been continued in 2010; this time exclusively with CNG-vehicles. This paper aims to give an overview on the potentiality of a CNG engine for race applications starting from thermo-dynamical considerations up to a concrete comparison with the gasoline engine from which it has been derived. The availability of experimental data and the use of modern simulation tools widen the possibility for studying different scenarios for performance development. Copyright © 2011 SAE International.


Grill M.,FKFS | Bargende M.,FKFS | Rether D.,University of Stuttgart | Schmid A.,University of Stuttgart
SAE Technical Papers | Year: 2010

Two combustion models are presented: A quasi-dimensional approach, based on the injection shape and an empirical model. Both models have computation times of less than one second per cycle. The quasi-dimensional approach for CI combustion discretizes the injection jet in slices. Pilot-injections are modeled as separate zones. The forecast capability and the limitations of the model are discussed on the basis of measurements. Mentioned above the base of the quasi-dimensional model is the injection rate. Often it is difficult to obtain these data. There is therefore another empirical approach for combustion, which does not need the injection rate as input. Both models have to be calibrated. This can be done by an automatic calibration tool on the basis of the advanced Powell method. The differences and advantages compared with other optimization methods are shown. Emission-simulation models are highly important in simulating CI engines. The nitrogen-oxide and soot emissions are simulated with a "combined" approach based on an inhomogeneous two-zone model. © 2010 SAE International.


Winke F.,FKFS | Berner H.-J.,FKFS | Bargende M.,University of Stuttgart
SAE Technical Papers | Year: 2015

This study presents a comparison of different approaches for the simulation of HEV fuel consumption. For this purpose a detailed 1D-CFD model within an HEV drivetrain is compared to a 'traditional' map-based combustion engine model as well as different types of simplified engine models which are able to reduce computing time significantly while keeping the model accuracy at a high level. First, a simplified air path model (fast running model) is coupled with a quasi dimensional, predictive combustion model. In a further step of reducing the computation time, an alternative way of modeling the in cylinder processes was evaluated, by replacing the combustion model with a mean value model. For this approach, the most important influencing factors of the 1D-CFD air path model (temperature, pressure, A/F-ratio) are used as input values into neural nets, while the corresponding outputs are in turn used as feedback for the air path model. However, while the computing speed of the simulation can be further increased, this model type loses its predictiveness, compared to detailed combustion models. The performance of said engine models is evaluated within a HEV drivetrain model. Results for the New European Driving Cycle as well as the Artemis Urban Driving Cycle are shown. © 2015 SAE International.


Wittmeier F.,FKFS | Kuthada T.,FKFS
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2015

Cooling air flow is an important factor when it comes to vehicle performance and operating safety. In addition, it is closely linked to vehicle aerodynamics. In recent years more and more effort is being spent to optimize the losses generated by the flow through the vehicle. Grille shutters, better sealing and ducting are only some examples for innovations in this field of work, resulting in a lower contribution of the cooling air flow to overall drag. When investigating those effects, both experiments and numerical simulations are commonly used in the automotive environment. Still, when comparing the results from both methods, differences in the effect of cooling air flow can often be observed. To better understand the effects of cooling air flow, the ECARA Subgroup CFD decided to establish a common design for a generic open source vehicle model with a detailed underhood compartment to lay the foundation for a common investigation model. The DrivAer-model, developed at the TU Munich, was chosen as the baseline vehicle, due to its high level of detail and the good acceptance in the community in recent years. Based on the input of the members of the group, FKFS designed a baseline version of the underhood compartment including a radiator package with fan and a representation of the engine in close cooperation with TU Munich. Since the majority of DrivAer models built are for scale model testing, the engine features a simplified design to be used as a starting point for CFD validation. This simplified design fits well to the level of detail of the original model. The underhood flow can both exit through defined openings in the front wheel houses and into the underfloor region, which allows different cooling air concepts to be investigated. The cooling air package is based on component data of a mid-size passenger car. This paper gives some insight into the model and presents first results from both CFD and wind tunnel measurements in quarter scale including rotating wheels and state-of-the-art ground simulation. Copyright © 2015 SAE International.


Seboldt D.,Robert Bosch GmbH | Lejsek D.,Robert Bosch GmbH | Wentsch M.,FKFS | Chiodi M.,FKFS | Bargende M.,University of Stuttgart
SAE Technical Papers | Year: 2016

CNG direct injection is a promising technology to promote the acceptance of natural gas engines. Among the beneficial properties of CNG, like reduced pollutants and CO2 emissions, the direct injection contributes to a higher volumetric efficiency and thus to a better driveability, one of the most limiting drawbacks of today's CNG vehicles. But such a combustion concept increases the demands on the injection system and mixture formation. Among other things it requires a much higher flow rate at low injection pressure. This can be only provided by an outward-opening nozzle due to its large cross-section. Nevertheless its hollow cone jet with a specific propagation behavior leads to an adverse fuel-air distribution especially at higher loads under scavenging conditions. This paper covers numerical and experimental analysis of CNG direct injection to understand its mixture formation. For this purpose experimental investigations were carried out by the Robert Bosch GmbH using a two-cylinder SI engine at a high load operating point with high scavenging degree. To understand the mixture phenomena the test-bench activities were supported by numerical simulations with the 3D-CFD-tool QuickSim at the FKFS. The experiments included various injection timings and valve overlaps. Additionally, the tests were performed with two different nozzle concepts (outward- and inward-opening injector) to identify the influence of the jet shape on the fuel-air distribution. The simulations also contained these parameters and particularly considered the jet development and flow field in the combustion chamber and the intake port. The test-bench investigations revealed a close dependence of the mixture formation on the injection timing and jet characteristic during scavenging operation. The associated numerical studies resulted in a good agreement with the engine performance and led to a conclusive interpretation of the observed phenomena. Copyright © 2016 SAE International.


Kaal B.,University of Stuttgart | Grill M.,FKFS | Bargende M.,University of Stuttgart
SAE Technical Papers | Year: 2016

This paper presents a quasi-dimensional emission model for calculating the transient nitric oxide emissions of a diesel engine. Using conventional and high-speed measurement technology, steady-state and transient emissions of a V6 diesel engine were examined. Based on measured load steps and steady-state measurements a direct influence of the combustion chamber wall temperature on the nitric oxide emissions was found. Load steps to and from, as well as steady-state measurements down to almost stoichiometric global combustion air ratios were used to examine the behavior of nitric oxide formation under these operating conditions. An existing emission model was expanded in order to represent the direct influence of the combustion chamber wall temperature on the nitric oxide emissions as well as enabling the forecasting of nitric oxide emissions at low global combustion air ratios: Both particularly important aspects for the simulation of transient emissions. This also improves forecasting at steady-state operating points and enables forecasting for low global combustion air ratios in the first place. The improved model was validated for both steady-state and transient cases using measurements. In the area of the measured engine characteristics, an enhanced forecasting quality of the improved model was demonstrated for steady-state operating points. The simulated transient load steps delivered significantly better forecasts with the improved model. Overall, the improved model thus enables not only the prediction of nitric oxide emissions in a wider operating range, but rather also delivers more precise forecasts within the complete performance map, as well as in the case of transient operation. Copyright © 2016 SAE International.


« BMW to showcase AirTouch in Vision Car concept at CES | Main | New family of hydrophobic ionic liquid rocket propellants could replace hydrazine-based fuels » A consortium led by the Bosch Group has developed a standardized integrated diagnostic system that in the future will be able to clearly identify and locate defects in the electrical powertrain. The consortium’s project on diagnosis and repairs for electric vehicles—“DINA”—was funded with €2.8 million (US$3.1 million) by Germany’s Federal Ministry of Education and Research as part of the leading-edge “Electric Mobility South-West” cluster. Besides the Bosch Group, the consortium included DEKRA Automobil GmbH, the Fraunhofer Ernst-Mach-Institut, and the Research Institute of Automotive Engineering and Vehicle Engines Stuttgart (FKFS). The results of this research have important implications for suppliers, automakers, workshops, and testing organizations. Any company looking to succeed in the electric vehicle market needs a competitive aftersales concept. From July 2012 to July 2015, part of the DINA project was devoted to drawing up standards for the diagnosis and repair of high-voltage systems in electric vehicles and to researching suitable measurement methods. Consortium members also created an integrated diagnostic system to help detect and localize problems in an electric vehicle’s powertrain, from the high-voltage battery and inverter to the motors and charging system. This allows workshops to carry out “modularized repairs”. If it is possible to precisely determine where problems lie, there is no need to replace whole systems. Instead, in the future it will be possible to pinpoint and replace defective parts individually. This makes repairs not only faster, but also much more affordable. Being able to locate problems with precision is especially important when dealing with high-voltage batteries that consist of numerous independent cells. To make future battery systems easier to repair, the study also makes specific suggestions for how to build them. The diagnostic and repair methods the consortium has developed can now be contributed to the automotive industry’s development projects. A look at aftersales reveals how critical the DINA project’s research is. For example, flawless powertrain testing and diagnostics are an indispensable part of technical tests such as general vehicle inspections. What’s more, an electric vehicle’s value depends heavily on its condition, age, and the state of health of the valuable high-voltage battery. The project produced key insights into how to determine this state of health. Similarly, electrical powertrains call for new measuring devices and equipment for workshops and test benches. This is also an area the study addresses with recommendations and approaches for development work. With some 100 players from science and industry, the leading-edge “Electric Mobility South-West” cluster is an important regional associations in the field of electromobility. Coordinated by the regional agency e-mobil BW GmbH, the cluster aims to drive forward the industrial-scale manufacture of e-mobility in Germany and to establish the German state of Baden-Württemberg as one of the major providers of electromobility solutions. It brings together leading corporations and SMEs, especially those in the region covering Karlsruhe, Mannheim, Stuttgart, and Ulm, and networks them with local research institutions in four fields of innovation: vehicles, energy, information and communication technology, and production. In addition, the cluster features specialized working groups to ensure full coverage of all topics. The “intelligent move” working group, for instance, focuses on digitalization and automated driving.

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