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Journal Article

Simulation of Underbody Contribution of Wind Noise in a Passenger Automobile

Wind noise is a significant source of interior noise in automobiles at cruising conditions, potentially creating dissatisfaction with vehicle quality. While wind noise contributions at higher frequencies usually originate with transmission through greenhouse panels and sealing, the contribution coming from the underbody area often dominates the interior noise spectrum at lower frequencies. Continued pressure to reduce fuel consumption in new designs is causing more emphasis on aerodynamic performance, to reduce drag by careful management of underbody airflow at cruise. Simulation of this airflow by Computational Fluid Dynamics (CFD) tools allows early optimization of underbody shapes before expensive hardware prototypes are feasible. By combining unsteady CFD-predicted loads on the underbody panels with a structural acoustic model of the vehicle, underbody wind noise transmission could be considered in the early design phases.
Technical Paper

Aerodynamic Performance Assessment of BMW Validation Models using Computational Fluid Dynamics

Aerodynamic performance assessment of automotive shapes is typically performed in wind tunnels. However, with the rapid progress in computer hardware technology and the maturity and accuracy of Computational Fluid Dynamics (CFD) software packages, evaluation of the production-level automotive shapes using a digital process has become a reality. As the time to market shrinks, automakers are adopting a digital design process for vehicle development. This has elevated the accuracy requirements on the flow simulation software, so that it can be used effectively in the production environment. Evaluation of aerodynamic performance covers prediction of the aerodynamic coefficients such as drag, lift, side force and also lift balance between the front and rear axle. Drag prediction accuracy is important for meeting fuel efficiency targets, prediction of front and rear lifts as well as side force and yawing moment are crucial for high speed handling.
Technical Paper

BMW High Precision Fuel Injectionin Conjunction with Twin-Turbo Technology: a Combination for Maximum Dynamic and High Fuel Efficiency

The new inline six cylinder Twin-Turbo gasoline engine forms the pinnacle of BMW's wide range of straight-six power units, developing maximum output of 300hp and a peak torque of 300 lb-ft with a displacement of 3.0 litre. Using two turbochargers in combination with the new BMW High Precision Fuel Injection leads to a responsive build-up of torque and to an impressive development of power over a wide engine speed range. This paper gives a detailed overview of the turbocharger-and the injection system and describes the effect of both systems on power and torque, as well as on fuel consumption and emission. The big advantage of using two small turbochargers is their low moment of inertia, even the slightest movement of the accelerator pedal by the driver's foot serving to immediately build up superior pressure and power. This puts an end to the turbo “gap” previously typical of a turbocharged power unit.
Technical Paper

Transportation Fuels for the Future

This paper analyzes the availability of fossil resources and the projected demand development for transport energy. A continuation of current trends would lead to a gap between fuel supply and demand in 10 to 15 years from now. Based on the 3 political key criteria (security of energy supply, greenhouse gas emission reductions, strengthening of the economy) potential alternative fuels are screened and analyzed according to their contributions towards these political goals. A scenario for the development of future fuels is presented.
Technical Paper

Light Weight Engine Construction through Extended and Sustainable Use of Mg-Alloys

Eight partners from Europe and one from North America have joined efforts in a EU-supported project to find new ways for sustainable production of Mg-based engine blocks for cars. The ultimate aim of the work is to reduce vehicle weight, thereby reducing fuel consumption and CO2 emissions from operation of the vehicle. Four new magnesium alloys are considered in the project and an engine block has been series cast - 20 each in two alloys. An extensive mechanical testing program has been initiated to identify in particular the high temperature limits of the four alloys and a significant experimental study of proper bolt materials for joining is being done in parallel. Engine redesign and life cycle analysis has also been completed to secure the future sustainable exploitation of the project results. This paper presents an overview of the work and results obtained until now - 3 months before the ending date of the project.
Technical Paper

Potentials of the Spray-Guided BMW DI Combustion System

The spray-guided BMW DI combustion system eliminates the most important disadvantages of the wall-and air-guided 1st generation DI combustion systems. With its central injector position, the spray-guided system provides a stratified mixture at the spark plug and reduces wall wetting significantly. The low spray penetration and high spray stability of the outward-opening piezo injector allow an extension of the stratified engine map to higher engine load and speed. The piezo drive permits an extremely fast opening of the injector needle, thus enabling multiple injections with very short delay times and high flexibility for the calibration strategy to supply a very efficient combustion with low unburnt hydrocarbon and carbon monoxide emissions. Compared to a conventional throttled SI engine, the spray-guided system shows a fuel consumption potential of about 20% in the NEDC.
Technical Paper

A Systematic Analysis of CO2-Reduction by an Optimized Heat Supply during Vehicle Warm-up

A transient 1D-network simulation model of the relevant power train components and fluid circuits of a state-of-the art passenger car has been developed, including engine, gearbox, coolant, motor oil and gearbox oil circuit. A system analysis was conducted to identify the subsystems of the vehicle where thermal intervention was expected to have major influence on fuel consumption during warm-up. Variable heat flows have been applied to those subsystems in the simulation model and their influence on the NEDC fuel consumption has been evaluated. The results show the potential fuel reduction effects of heat management measures on the respective system components with a special emphasis on the component interaction. A sensitivity study of variable heat distribution among the subsystems of the vehicle shows the optimization potentials of heat management measures. The results from the numerical simulation have been validated in an experimental setup.
Technical Paper

Developing Planar Laser-Induced Fluorescence for the Investigation of the Mixture Formation Process in Hydrogen Engines

Planar laser-induced fluorescence (PLIF) has been successfully used for the investigation of the mixture formation process in hydrogen engines. Detailed information has been obtained about the process development (qualitative measurements) and on the fuel/air-ratio (quantitative measurements) in the combustion chamber. These results can be used for further optimization of the mixture formation and the combustion process concerning emissions and fuel consumption. The measurement technique used here is not limited to hydrogen and can also be applied to other fuel gases like natural gas. The main topic of this paper is the experimental verification of the PLIF data by simultaneous Raman scattering measurements. By Raman scattering the fuel/air-ratio can directly be determined from the direct concentration measurements of the different gas species.
Technical Paper

Development and Application of a New Mass Spectrometer Based Measurement System for Fast Online Monitoring of Oil Emission in the Raw Exhaust Gas of Combustion Engines

An increasing environmental consciousness as well as the awareness for sustained preservation of natural resources causes new regulations for emissions and great efforts for fuel economy and increasing oil service intervals. For a better understanding of the process generating pollutants, the emissions of every phase of the combustion cycle have to be monitored online. Moreover, it is important to measure the raw exhaust gas during different driving cycles and investigate the influence of different parameters as for example changing engine operating conditions. The new mass spectrometer (MS) based measurement system allows the direct detection of unburned gaseous oil HC without tracers. The gas inlet system enables crank angle resolved monitoring of different raw exhaust gas compounds in the exhaust manifold or directly in the cylinder.
Technical Paper

Solid Oxide Fuel Cell Auxiliary Power Unit - A Paradigm Shift in Electric Supply for Transportation

Delphi Automotive Systems and BMW have been jointly developing Solid Oxide Fuel Cell (SOFC) technology for application in the transportation industry primarily as an on-board Auxiliary Power Unit (APU). In the first application of this joint program, the APU will be used to power an electric air conditioning system without the need for operating the vehicle engine. The SOFC-based APU technology has the potential to provide a paradigm shift in the supply of electric power for passenger cars. Furthermore, supplementing the conventional fuel with reformate in the internal combustion engine, extremely low emissions and high system efficiencies are possible. This is consistent with the increasing power demands in automobiles in the new era of more comfort and safety along with environmental friendliness.
Technical Paper

Research Results and Progress in LeaNOx II -A Co-operation for Lean NOx Abatement

In a consortium of European industrial partners and research institutes, a combination of industrial development and scientific research was organised. The objective was to improve the catalytic NOx conversion for lean burn cars and heavy-duty trucks, taking into account boundary conditions for the fuel consumption. The project lasted for three years. During this period parallel research was conducted in research areas ranging from basic research based on a theoretical approach to full scale emission system development. NOx storage catalysts became a central part of the project. Catalysts were evaluated with respect to resistance towards sulphur poisoning. It was concluded that very low sulphur fuel is a necessity for efficient use of NOx trap technology. Additionally, attempts were made to develop methods for reactivating poisoned catalysts. Methods for short distance mixing were developed for the addition of reducing agent.
Technical Paper

Fuel Cell Auxiliary Power Unit - Innovation for the Electric Supply of Passenger Cars ?

The first application in which the fuel cell will find a market in the passenger car is as an “electrochemical battery” serving the purpose the fuel cell can do best: To generate electricity for the electrical power bus with a high degree of efficiency. Such a fuel cell referred to as an APU (Auxiliary Power Unit) exceeds the power output and endurance of a battery and is able not only to supply power to all conventional electrical power-consuming items in the car, but also to provide new functions such as air conditioning when the car is at a standstill. In the long run, indeed, the fuel cell may even be able to replace the electrical alternator.
Technical Paper

The Third Generation of Valvetrains - New Fully Variable Valvetrains for Throttle-Free Load Control

The SI-engine has a disadvantage in fuel economy compared with a DI-Diesel engine. One of the major effects is the throttle-driven load control with its pumping losses. The main target is to reduce these losses in the thermodynamic process with a throttle-free load control. BMW has developed fully variable valve trains as a possible technical solution to realise a load control by regulating the valve lift and the closing time of the inlet valve. The essential variability can be achieved by fully variable mechanical valve trains or mechatronic systems both showing a robust running behavior in emissions and cyclic fluctuations. The camshaft driven mechanical system is based on the technology of the BMW Double-VANOS system. An additional variability makes it possible to shift the valve lift continuously in order to control the valve closing. The highest variability is given by a system with each valve being controlled seperatly.
Technical Paper

BMW's Energy Strategy - Promoting the Technical and Political Implementation

BMW can look back on 20 years of research activities on hydrogen propulsion systems. Hydrogen fuel is the only means of offering pure driving pleasure on the basis of a sustainable energy loop. As the hydrogen era is still quite a while away the BMW Energy Strategy „Via Natural Gas to Hydrogen” has been developed. The first step was to build series-production compressed natural gas (CNG) cars back in 1995. By switching to liquefied natural gas (LNG) not only is the cruising range tripled but technologically the final stepping-stone is reached in preparing the way for liquefied hydrogen. BMW's automotive and drive technology for hydrogen is now available and ready to move out of the laboratory on to the road. At Munich Airport a BMW „Clean Energy” car is already providing shuttle services. Its fuel is supplied by the world's first public filling station for liquefied hydrogen.