Automotive and Engine Technology最新文献

With the electrification of powertrains and the progressive implementation of assisted and automated driving functions, the vehicle wiring harness is becoming increasingly important in the automotive industry. The design of the wiring harness is gaining considerable variation and is becoming more and more complex. In order to master this complexity in the manufacturing processes in a reliable manner, new approaches are required for the progressive automation of the wiring harness production. Additive manufacturing processes have not yet been used in the production of vehicle wiring harnesses. The development of additive processing of conductive materials therefore creates a new basis for the development of automation solutions to produce vehicle wiring harnesses. With the approach of function-integrated multi-material application, the possibility of using electrically conductive polymers in the vehicle wiring harness is specified in detail. A fundamental study was carried out to determine the values of electrical conductivity that can be achieved in the field of plastics. Based on these findings, the research question being addressed is whether polymers can be made electrically conductive to an extent that is suitable for use in a vehicle’s wiring harness. The materials of electrically conductive components from conventional vehicle electrical systems serve as a reference. A specially developed test set-up for measuring the electrical conductivity of polymers provided the required measured values. The quantitative evaluation of the measurements clearly shows that the use of conductive polymers as a conductive material in the vehicle wiring harness is only possible to a limited extent. The major benefit of the study identified the use of electrically conductive polymers for the automatable production of electrical connections.

The anode subsystem is a major energy consumer of polymer-electrolyte-membrane (PEM) fuel cell systems. A passive hydrogen recirculation system, like an ejector, is an excellent solution to maximize hydrogen utilization while maintaining low parasitic losses. However, high development efforts are necessary to maximize the performance of the ejector for the entire operating range. This research paper provides part of a toolchain for ejector development, consisting in particular of a multi-parameter simulation based on rotational symmetric 2D CFD. The 2D CFD greatly helps optimize the design of the ejector, reducing development effort, and increasing accuracy. In addition, the main correlations between thermodynamic states and geometry on the entrainment ratio are evaluated. Subsequently, an ejector is designed for a PEM fuel cell application using 2D CFD and the results show in which operating range a single ejector can be applied. This toolchain enables rapid design and optimization of ejector geometry, saving development time and cost while increasing accuracy and extending the operating range.

This article presents results of the optical spray investigations of a methanol high-pressure direct injector for maritime applications. The injector is a two-in-one fuels injector, with a diesel path to inject diesel centrally for the diesel mode or to inject a small pilot amount of diesel for igniting methanol. The methanol will be injected via three nozzles, which are placed around the central diesel needle. The experimental studies were performed at a pressurized injection chamber with three different injection pressures, two fuels and three nozzle designs to evaluate first the basic spray characteristics of the spray of this two-in-one fuel’s injector concept with four needles as well as the impacts of the varied parameters. For the injection analysis, ethanol was used instead of methanol due to the extensive safety requirements for methanol. Furthermore, a 3D-CFD numerical analysis of the nozzle flow of the methanol path is presented in this article. Correlations between the calculated nozzle flow and the experimental measured spray data are given.

Today’s governmental legislations require region specific emission standards for passenger vehicles. Continuously increasing legal requirements demand the development of more complex exhaust gas after treatment systems to further reduce harmful gases like carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NO_x). Due to specific load profiles and other boundary conditions, the efficiency of the aftertreatment system declines over lifecycle, so that the emissions might increase. Consequently, the durability of the system becomes a critical design parameter with upcoming legislation demanding emissions stability over the vehicle life cycle. Within this publication, catalyst aging effects due to air–fuel ratio (AFR) swing are analyzed experimentally. To create catalyst aging conditions, a modern eight-cylinder turbocharged engine was modified and specific aging cycles with a variation of AFR swing amplitude and frequency were conducted. Light-off curves were used to depict the negative impact of the AFR swing on the aging catalyst systems. A higher swing frequency resulted in an increased temperature amplitude within the entrance area of the catalyst, while an elevated amplitude lead to more exothermic heat release and stronger aging over the complete catalyst, as visualized via conversion maps. A theoretical calculation of thermal loads by Arrhenius equation supports the results and indicates the direction of supplementary experimental approaches.

Trends such as autonomous driving, non-driving related activities and digitalisation are contributing to a revolution in vehicle concept design. An aspect of this is the consideration of future use cases in shaping vehicle architectures. Future user scenarios can help identify relevant use cases, from which the user needs and system requirements can be derived. The derived requirements need to be matched to vehicle functions and architectural modules that can fulfil them. However, the optimal combination of functions and modules can be difficult to identify due to the numerous possibilities. The aim of this paper is to apply a matrix-based methodology that enables the systematic matching of requirements to vehicle functions and/or modules, as well as the identification of an ideal module/function combination for all the considered requirements. An example is presented that considers a requirement specification that has been derived from predetermined user needs. The requirements are matched to suitable functions/modules and the best possible combinations are determined using the proposed matrix-based methodology. Two optimal combinations are selected, one for a vehicle in the entry level segment and the other for a premium vehicle. The results indicate it is possible to determine an optimal combination for both vehicle segments considered, as well as the substantial influence the rating parameters have on the end result. Lastly, it is shown how the results can be applied by concept designers in order to draft tailored, user-orientated interior concepts.

The number of traffic accidents resulting in personal injury and property damage is increasingly being reduced by effective advanced driver assistance systems (ADAS). Nevertheless, many traffic accidents still cannot be prevented today because they are due to wet, snow- and ice-covered roads. For this reason, the Institute of Automotive Engineering (IAE) of the Technical University of Braunschweig is investigating the road friction coefficient sensitivity and adaptation of advanced driver assistance systems (ADAS) currently in series production from 2018 to 2021 as part of the ‘Road Condition Cloud’ research project funded by the German Research Foundation (DFG) to increase driving safety, particularly on wet, snow- and ice-covered roads. In this article, the road friction coefficient sensitivity and adaptation of an automatic emergency steer assist is simulatively investigated. This assist overrides the driver to automatically execute an evasive maneuver. The driving maneuver used is a standardized obstacle-avoidance maneuver that is simulatively repeated on a dry, wet, snow- and ice-covered road. The road friction coefficient sensitivity shows that this test is already failed on a wet road because the simulated vehicle does not pass the second lane without errors. Subsequently, a road friction coefficient adaptation of the emergency steer assist is investigated. This adaptation varies the maximum lateral acceleration of the evasive trajectory depending on an estimated value of the road friction coefficient in order not to exceed the maximum adhesion coefficient of the wheels during the evasive maneuver. Ideally, the estimated value matches the true road friction coefficient so that the second lane is passed without errors even on a wet, snow- and ice-covered road. In contrast, an existing difference determines whether the second lane is reached. Finally, the necessary accuracy requirements of the road friction coefficient estimation are determined in an novel estimation error diagram. A road friction coefficient adaptation increases the driving safety of driver advanced assistance systems (ADAS) that are in series production today and future highly automated driving functions (HAF) and is necessary for automated driving because the driver is not present as a fallback level. The described results were presented before in [1].

In publications and conferences on the subject of wheel brakes, different concepts of electromechanically actuated wheel brakes can be found, as well as investigations into their suitability for the use in passenger cars. The vast majority of these brakes are disc or drum brakes, which are actuated by an electric motor. In the present publication, a brake concept is considered, that combines an electromagnetically actuated full-pad disc brake with a 10″ duo-duplex drum brake. The brake concept is researched in a project regarding brakes for autonomous shuttles and thus dimensioned using vehicle data of an example shuttle. The electromagnet was designed using finite element methods and the overall brake prototypically realized. The validation of the system design is carried out in component and system tests. The results show the suitability of the concept for the selected vehicle in terms of dynamics, installation space and energy requirements. However, there is a strong dependence of the braking torque output on the frictional sliding speed. Using hypothesis-based testing, electromagnetic effects like eddy currents are ruled out as a possible cause and the friction coefficient within the full-pad disc brake is identified as the main cause for the loss in torque. Consequently, the associated development conflict is identified and lies in the double function of the flux-carrying material in the electromagnet, which also acts as a friction partner for the braking disc.

A cost model for the estimation of production costs of permanent magnet synchronous machines (PMSM) is presented, which allows to alter design choices such as wire technology, winding layout, cooling system, materials and more. With the goal to make results reproducible by others, the methods are explained in detail and used data and assumptions are given. The developed model helps to understand the interaction between the design of PMSM, manufacturing methods and the resulting costs. With it, different PMSM technologies and materials can be evaluated regarding its influence on the production costs, which is a perquisite to find the best compromise between performance and costs. Production volume is shown to be the most decisive factor for the resulting production costs. Between minimum and maximum assumed volumes, an average cost per unit reduction of 67% could be observed. Furthermore, the results imply that the winding production is responsible for the greatest part of the overall costs, followed by the rotor assembly (including rare earth magnets). When using the model to compare different wire types, it can be stated that up to a production volume of roughly 150,000 units/year, hairpin wires are more expensive to produce. Above this volume, hairpin windings will get cheaper than round wire windings due to its higher grade of automation of the production process. Through the conducted investigations and the presented results, it is demonstrated that the cost model can serve to evaluate technologies with regards to costs in the early development stage. This way a more holistic assessment of technologies for PMSM is possible, helping to find the ideal compromises between costs and performance and to increase the attractiveness of sustainable mobility.

The reduction of carbon dioxide emissions and the corresponding increase in gasoline engine efficiency are crucial in engine development. Wall heat losses are a major cause of efficiency loss, accounting for 15–30% of the total fuel energy. One promising solution is the use of "thermal swing" coatings at the combustion chamber walls because of offering the possibility that the surface wall temperature following the working gas temperature, whereby the wall heat transfer can be reduced at any time during the engine cycle. This type of coating material is characterized by low thermal conductivity and, at the same time, low heat capacity. Based on the idea of the “thermal swing” coatings, yttria stabilized zirconia (YSZ) was selected as the coating material for the piston surface and its efficiency potential was experimentally investigated on a single-cylinder gasoline engine. The use of highly dynamic temperature probes in the piston allowed precise analysis of cycle-based temperature fluctuations, especially on the piston surface. The transmission of the piston temperatures was cable-based and accomplished through the use of a lever system in the engine. The measurement results confirmed the minimal impact on the efficiency that was determined in preliminary simulations. However, the effect of the coating could be established through the measurements.

The swirling motion of the intake air creates a flow field within the engine’s cylinder, which enhances the mixing of air and fuel, as well as combustion and emissions. Moreover, swirl formations in the cylinder and their subsequent breakdown into turbulence kinetic energy reflect the importance of in-cylinder flow structures. This study combined the PIV technique with the POD method to investigate the velocity fields in a single-cylinder diesel engine. The experiments were conducted at various pressure conditions and different engine rpm. Based on the obtained results, the average flow velocities from expansion to exhaust strokes were reduced in comparison with intake strokes. In all engine pressure and speed conditions, compression and exhaust strokes showed a significant change in flow patterns with changes in pressure and speed. At various crank angles, the POD modes demonstrated flow properties of the swirling motion, along with a dissimilarity feature and evolution of the in-cylinder flow.