Nils Widdecke

Classification of aerodynamic tyre characteristics

The geometric shape of the tyres can have a large influence on the aerodynamic drag of a passenger car as it has been shown already in different publications. However, so far it is not possible to quantify the aerodynamic characteristics of a tyre without measuring it mounted on a vehicle in a wind tunnel and comparing it to other tyres. For this reason a research project at the Institute for Internal Combustion Engines and Automotive Engineering at the University of Stuttgart (IVK) was launched with the intention of categorising the aerodynamic characteristics of passenger car tyres.

Investigation of visibility properties through wetted glass planes on vehicles

When driving a car, the view onto the surrounding traffic must be ensured at all times. Especially the view through the side window onto the rear view mirror and other traffic participants is very important. When driving on a wetted road, water and dirt can impair driving comfort and safety. Surface bound water droplets and rivulets on the windshield and the side glass reduce the visibility. Therefore, a new evaluation method is presented which assesses the view through pools of water on a horizontal glass plane depending on wettability of the glass and the volume of single droplets or the height of water films. It provides information about the transparency behavior of water droplets and the impact factors of a soiled side window on the view through it.

Increase in range of a battery electric vehicle by means of predictive thermal management

Battery electric vehicles (BEV) allow local emission free travelling and are also capable of reducing the anthropogenic emission of CO2. Since the waste heat of a BEV is much smaller than in any combustion engine driven car the energy for the heating of the cabin has to be taken from another source. If the energy is drawn from the traction battery the driving range is affected severely. Hence, offering more comfort and extending the driving range become counteracting development strategies. To predict how the driving range is influenced by the need for comfort a predictive simulation tool was developed. The paper will show how the range of the battery electric vehicle can be increased by thermal management strategies. The objective of the presented investigations is to quantify the potential of optimizations of the thermal management system. Therefore, the thermal management system is configured in a modular way. Thus, it is possible to attribute savings achieved via single alterations in the system, such as the addition of a cabin heat exchanger or a heat pump. For the use in a BEV the capability of the thermal management system has been increased to be able to include predictive strategies and adapt to the driver’s demands. Furthermore, the effect of preconditioning on the total energy balance and range is analyzed and depicted. This shows the importance of including preconditioning in thermal management to increase the range of a BEV. The paper is a summary of the results of the FVV project “Warmemanagement an batteriebetriebenen Elektrofahrzeugen (WBEF)”.

Investigation of Time-Resolved Nozzle Interference Effects

Automotive wind tunnels still see an increasing significance in the vehicle development process. Nevertheless, the flow topology in the test sections of open jet wind tunnels is not yet understood completely. A large source for transient structures is the shear layer developing between the high velocity nozzle flow and the calmly air in the plenum.

Windkanäle und Messtechnik

Dass die Aerodynamik heute integraler Bestandteil eines modernen Fahrzeugentwicklungsprozesses ist, geht sehr deutlich und detailliert aus den vorangegangenen Kapiteln dieses Buches hervor. Sowohl die Erfullung der Lastenheftvorgaben in Bezug auf die aerodynamischen Gesamtkrafte und -momente, die z. B. die CO2-Emissionen und die Fahrstabilitat wesentlich beeinflussen, als auch die Funktion wichtiger Baugruppen, wie Motor- und Bremsenkuhlung, Klimatisierung, Dichtungen, Turen, Klappen und Anbauteile erfordert die Mitwirkung der Fahrzeugaerodynamiker, die hierzu ihre wichtigsten Prufstande, die Windkanale, einbringen. Windkanale simulieren – wie im Ubrigen auch die computergestutzte Stromungssimulation (CFD) und die computergestutzte Aeroakustik (CAA) – die Fahrt auf der Strase, allerdings mit experimentellen statt mit numerischen Mitteln. Die Strasenfahrt bleibt dabei stets das Mas der Dinge, weil auch der Kunde sein Fahrzeug auf der Strase einsetzt und nicht auf Prufstanden. Fur die aerodynamische Entwicklungsarbeit sind Strasenversuche in der Regel wenig geeignet, u. a. weil sie nur schwer reproduzierbare Versuchsbedingungen aufweisen. Darauf wird in diesem Kapitel noch eingegangen. Windkanale weisen als stationare Prufstande solche Nachteile nicht auf. Allerdings sind, wie bei jeder Simulation, ihre Grenzen der Anwendbarkeit zu beachten. Dies erfordert ein tiefes Verstandnis ihrer Physik. Auch dazu wird dieses Kapitel detailliert beitragen.

Twenty years of automotive wind tunnels at the institute for combustion engines and automotive engineering of Universität Stuttgart 1989–2009

The transmission becomes more important in terms of evaluating emissions, drivability and comfort. These developments have caused an increase in the complexity of the transmission control units of automatically shifting transmissions (automatic transmissions, dual-clutch transmissions and automated manual transmissions) for more than twenty years. Additionally, the increasing popularity of these transmission concepts in all markets leads to more vehicle-engine-transmission combinations which have to be calibrated. The growing effort also means that more personnel and longer calibration times are required, which thus results in higher development costs. The Institute of Automotive Engineering of the Technische Universitat Braunschweig (Germany) describes methods and tools to reduce the effort for TCU calibration in terms of shift comfort by means of efficient transmission calibration on a roller dynamometer.

20 Jahre Fahrzeugwindkanäle der Universität Stuttgart am Institut für Verbrennungsmotoren und Kraftfahrwesen 1989–2009

Im Jahr 1989 nahmen der neue Fahrzeugwindkanal und der Modellwindkanal beim Institut fur Verbrennungsmotoren und Kraftfahrwesen (IVK) der Universitat Stuttgart in Stuttgart-Vaihingen den Betrieb auf. Beide Windkanale wurden in den vergangenen Jahren umfangreich technisch nachgerustet, und auch kunftig sind weitere Optimierungen geplant. Mit der Intensivierung der numerischen Stromungsberechnung begann die Entwicklung eines integrierten, aus Experiment und Simulation bestehenden Ansatzes zur aerodynamischen Fahrzeugoptimierung. Die Parallelitat und enge Vernetzung von Experiment und Simulation weist den Weg in die Zukunft der Automobilaerodynamik.