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What are the requirements of customers in an urban environment? What will sustainable mobility look like in the future? This presentation gives an overview of the integrated approach used by BMW to develop the BMW i3 - a purpose-built battery electric vehicle. Very low driving resistances for such a vehicle concept enable the delivery of both impressive range and driving excitement. A small optional auxiliary power unit offers range security for unexpected situations and opens up BEVs to customers who are willing to buy a BEV but are still hesitant due to range anxiety. Additional electric vehicles sold to the formerly range anxious will create additional electric miles. Presenter Franz Storkenmaier, BMW Group

Modern exhaust systems contain not only a piping network to transport hot gas from the engine to the atmosphere, but also functional components such as the catalytic converter and turbocharger. The turbocharger is common place in the automotive industry due to their capability to increase the specific power output of reciprocating engines. As the exhaust system is a main heat source for the under body of the vehicle and the turbocharger is located within the engine bay, it is imperative that accurate surface temperatures are achieved. A study by K. Haehndel [1] implemented a 1D fluid stream as a replacement to solving 3D fluid dynamics of the internal exhaust flow. To incorporate the 3D effects of internal fluid flow, augmented Nusselt correlations were used to produce heat transfer coefficients. It was found that the developed correlations for the exhaust system did not adequately represent the heat transfer of the turbocharger.

The requirement of the start of the internal combustion engine (ICE) not only at vehicle standstill is new for full hybrid electric vehicles in comparison to conventional vehicles. However, the customer will not accept any deterioration with respect to dynamics and comfort. ICE-starting-systems and -strategies have to be designed to meet those demands. Within this research, a method was developed which allows a reproducible maneuver-based analysis of ICE-starts. In the first step, a maneuver catalogue including a customer-oriented maneuver program with appropriate analysis criteria was defined. Afterwards, the maneuvers were implemented and verified in a special test bench environment. Based on the method, two sample hybrid vehicles were benchmarked according to the maneuver catalogue. The benchmarking results demonstrate important dependencies between the criteria-based assessment of ICE-starts and the embedded ICE-starting-system and -strategy.

Raising demands towards lightweight design paired with a loss of originally predominant engine noise pose significant challenges for NVH engineers in the automotive industry. From an aeroacoustic point of view, low frequency buffeting ranks among the most frequently encountered issues. The phenomenon typically arises due to structural transmission of aerodynamic wall pressure fluctuations and/or, as indicated in this work, through rear vent excitation. A possible workflow to simulate structure-excited buffeting contains a strongly coupled vibro-acoustic model for structure and interior cavity excited by a spatial pressure distribution obtained from a CFD simulation. In the case of rear vent buffeting no validated workflow has been published yet. While approaches have been made to simulate the problem for a real-car geometry such attempts suffer from tremendous computation costs, meshing effort and lack of flexibility.

The Noise Vibration and Harshness (NVH) characteristics and requirements of vehicles are changing as the automotive manufacturers turn their focus from developing and producing cars propelled by internal combustion engines (ICE) to electrified vehicles. This new strategic orientation enables them to offer products that are more efficient and environmentally friendly. Although electric powertrains have many advantages compared to their established predecessors they also bring new challenges that increase the difficulty of matching the high quality requirements of premium car producers especially regarding NVH. Electric motors are one of the most important sources of vibrations in electric vehicles.

The G-equation model was implemented in the commercial code ANSYS CFX and validated against experimental data in order to successfully simulate turbulent premixed combustion in internal combustion engines. The model is based on the level-set approach. Two transport equations are solved respectively for the G-scalar mean value, representing the local distance function from the time-averaged mean flame front, and its variance, correlated to the turbulent flame brush thickness. The model closure for tracking the flame front is based on an algebraic expression for the turbulent burning velocity. The composition of the reacted mixture is evaluated by coupling the code with flamelet libraries generated with the ANSYS CFX-RIF package by means of a reaction progress variable computed as a function of the G-related quantities.

The thermal prediction of a vehicle under-body environment is of high importance in the design, optimization and management of vehicle power systems. Within the pre-development phase of a vehicle's production process, it is important to understand and determine regions of high thermally induced stress within critical under-body components. Therefore allowing engineers to modify the design or alter component material characteristics before the manufacture of hardware. As the exhaust system is one of the primary heat sources in a vehicle's under-body environment, it is vital to predict the thermal fluctuation of surface temperatures along corresponding exhaust components in order to achieve the correct thermal representation of the overall under-body heat transfer. This paper explores a new method for achieving higher accuracy exhaust surface temperature predictions.

In order to meet the severe emission restrictions imposed by SULEV and EURO V standards the catalytic converter must reach light-off temperature during the first 20 seconds after engine cold start. Thermal losses in the exhaust manifold are driven by the heat transfer of the pulsating and turbulent exhaust flow and affect significantly the warm-up time of the catalyst. In the present paper an investigation concerning the gas-side heat transfer in the exhaust system of a spark ignited (SI) combustion engine with retarded ignition timing and secondary air injection into the exhaust port is reported. Based on this analysis, the warm-up simulation of a one-dimensional flow simulation tool is improved for an evaluation of different exhaust system configurations.

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.

While hybrid-electric powertrain features such as regenerative braking and electric driving can improve the fuel economy of a vehicle significantly, these features may also have a considerable impact on driving dynamics. That is why extra effort is necessary to ensure safety and comfort that customers usually expect from a conventional vehicle. The purpose of this paper is to initiate a discussion regarding different drivetrain concepts, necessary changes in chassis systems, and the impact on vehicle dynamics. To provide input to this essential discussion, braking and steering systems, as well as suspension design, are analyzed regarding their fit with hybrid systems. It is shown how an integration of hybrid technology and chassis systems benefits vehicle dynamics and why “by-wire” technology is a key enabler for safe and comfortable hybrid-electric vehicles.

AJ alloy is used with a new Aluminum-Magnesium Composite Design, which is an innovative approach to lightweight crankcase technology. The component is manufactured using high pressure die cast process. A wide range of chemical compositions was used to develop a good understanding of the behavior of this alloy system (castability, thermophysical, mechanical, microstructure). The basic mechanical properties were determined from separately die cast samples and also from samples machined out from high pressure die cast components. Tensile, creep, bolt load retention/relaxation and high cycle fatigue properties were established and analyzed using multivariate analysis and statistical approach. This methodology was used to select the optimal chemical composition to match the requirements. The sensitivity of the alloy to heat exposure was investigated for both mechanical properties and microstructure.

For the first time, the BMW Active Steering system allows driver-independent steering intervention at the front axle with the mechanical link between the steering wheel and the front axle still in place. The system is primarily comprised of a rack-and-pinion steering system, a double planetary gear and an electric actuator motor. This new level of freedom enables continuous and situation-dependent variation of the steering ratio and therefore adaptation of the transmission behaviour between the steering wheel and the vehicle's reaction to the relevant driving situation. Comfort, steering effort, handling and directional stability have been extensively optimised as a result of this. In addition, driver-independent steering intervention also guarantees vehicle stabilisation in critical driving situations. As a world exclusive, the new Active Steering system will be available for the first time as an option in the new BMW 5 Series.

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.

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.

Engine management systems in modern motor vehicles are becoming increasingly extensive and complex. The functionality of the control units which are the central components of such systems is determined by the hardware and software. They are the result of a lengthy development and production process. Road testing of control units, together with testing them on the engine test bench, is very time consuming and costly. An alternative is to test control units away from their actual environment, in a virtual context. This involves operating the control unit on a Hardware-in-the-Loop test bench. The control unit's large number of individual and interlinked functions necessitates a structured, reproducible test procedure. These tests can, however, only be conducted once an engine prototype has been completed, as the parameters for the existing conventional models are determined from the data measured on the test bench.

The quiet nature of hybrid and electric vehicles has triggered developments in research, vehicle manufacturing and legal requirements. Currently, three countries require fitting an Approaching Vehicle Alerting System (AVAS) to every new car capable of driving without a combustion engine. Various other geographical areas and groups are in the process of specifying new legal requirements. In this paper, the design challenges in the on-going process of designing the sound for quiet cars are discussed. A proposal is issued on how to achieve the optimum combination of safety, environmental noise, subjective sound character and technical realisation in an iterative sound design process. The proposed sound consists of two layers: the first layer contains tonal components with their pitch rising along with vehicle speed in order to ensure recognisability and an indication of speed.

In addition to the creep properties, the fatigue properties are essential for the design of a power-train component in Mg which is operated at elevated temperatures. In case of the new BMW I6 composite Mg/Al crankcase using the AJ alloy system, material testing focused on both subjects. The basic mechanical properties were determined from separately die cast samples and also from samples machined out from high-pressure die cast components. Tensile, high cycle fatigue properties, low cycle fatigue and crack propagation properties were established and analyzed within the technical context for power-train applications reflected in the temperature and load levels. The aspects of mean stress influence, notch sensitivity and crack propagation are evaluated to estimate the performances of the AJ62A alloy 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.

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.

Increasing demands on engine efficiency and specific power have resulted in progressively higher loadings on internal components of combustion engines. Therefore the durability assessment of such components is increasingly in demand, triggered by both reliability and economic requirements. Within this context the TMF cylinder head simulation process established at BMW is presented in the following article. The numerical model is able to account for thermo-mechanical loading histories. These lead to a transient evolution of the material characteristics during the lifetime due to aging in aluminum alloys. Therefore a viscoplastic constitutive model is coupled with an aging model to handle the change in precipitation structure and the effect on the material properties, especially for non heat-treated secondary aluminum alloys. The local damage evolution is modeled based on the growth of micro cracks.