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In exhaust systems with selective catalytic reduction (SCR) a fast conversion of liquid urea to gaseous ammonia and a uniform distribution of the ammonia vapor upstream of the SCR catalyst are essential to reduce the nitric oxides efficiently. For the prediction of the mixing process and the transport of ammonia vapor with the CFD method an accurate description of the turbulent flow field is a basic requirement. This paper presents the comparison of simulation results using three different turbulence models (high-Re kε-RNG model, low-Re kω-SST model, Reynolds stress model) with measurements of the turbulent velocity field using Laser Doppler Anemometry (LDA). The investigations were carried out for a SCR system with a swirl mixer on a cold flow test bench for two different volume flows. From the measured velocity signals different components of the Reynolds-tensor were derived.

In this paper, the multi-physical simulation workflow from electromagnetics to structural dynamics for a squirrel-cage induction machine is explored. In electromagnetic simulations, local forces and rotor torque are calculated for specific speed-torque operation points. In order to consider non-linearities and interaction with control system as well as transmission, time-domain simulations are carried out. For induction machines, the computational effort with full transient numerical methods like finite element analysis (FEA) is very high. A novel reduced order electro-mechanical model is presented. It still accounts for vibro-acoustically relevant harmonics due to pulse-width modulation (PWM), slotting, distributed winding and saturation effects, but is substantially faster (minutes to hours instead of days to weeks per operation point).

Distributed integrated architectures in the automotive and avionic domain result in hardware cost reduction, dependability improvements, and improved coordination between application subsystems compared to federated systems. In order to support safety-critical application subsystems, a distributed integrated architecture needs to support fault-tolerance strategies that enable the continued operation of the system in the presence of failures. The basis for the implementation and validation of fault-tolerance strategies are realistic fault assumptions, which are captured in a fault hypothesis. This paper describes a fault hypothesis for distributed integrated architectures, which takes into account the sharing of the communication and computational resources of a single distributed computer system among multiple application subsystems. Each node computer serves for the execution of multiple jobs.

An optimized monofuel CNG light duty vehicle based on the Opel Zafira was investigated under real-world conditions and the results are presented in this study. To analyze the real-world performance of the monofuel CNG vehicle due to fuel consumption and exhaust emissions representative experimental test on road-test routes were performed, including sections with significantly different driving conditions. Furthermore, driving tests at different constant speeds on freeway were carried out. A benchmarking to the same vehicle with diesel powertrain was done as well. The test vehicles were equipped with a new compact on-board measurement system and additionally GPS tracking to link the received geographic information of the road-test routes with the measured exhaust mass emission data. The measurement results were validated with Matlab Simulink models of the powertrain and vehicle.

The goal of this project was to determine the exhaust mass emissions of light duty trucks (LDT) with three different engine concepts under real world conditions in the urban area of Vienna. Therefore three identical GM Opel Combo LDT with 1.6 liter monovalent CNG S.I. engine, 1.7 liter common rail turbo charged diesel engine and 1.4 liter Ecotec gasoline S.I. engine were tested systematically on representative urban routes and in parcel service. All engines corresponded to the new Euro IV emission standard and were within the same power range.

In this study the performance of a monofuel compressed natural gas articulated truck was investigated under real-world conditions. To analyze the CNG vehicle due to fuel consumption and exhaust emissions a representative road-test route was conducted, including sections with significantly different driving conditions. Moreover, driving tests on freeway under higher load were carried out. As experimental equipment, a new ultra compact on-board system measured the in-car exhaust mass emissions in real time. Every second, a full dataset of CO₂, CO, HC and NOx emission rates was provided. The real-world emission measurements are based on a modal analysis of the emission concentrations in the tailpipe of the vehicle. The exhaust gas mass flow is calculated from the air mass flow and the gas components with a real-time reaction model. In combination with the vehicle speed, the emission rates in g/s are then calculated in gram per kilometer.

The objective of the project was to compare the exhaust gas emissions and fuel consumption of a test vehicle, which was on a one hand operating with premium gasoline 95 RON (RON 95) and a mixture of 90% by volume premium gasoline 95 RON and 10% by volume of high purity bio ethanol (E10) on the other hand. As a test vehicle a Skoda Octavia station wagon was used. The engine of the tested vehicle corresponded to the Euro 4 emission standard. The investigations were conducted under the real world conditions, and also at the chassis dynamometer test bench. The tested vehicle was equipped with a new On-board measurement System (OBM) to determine the mass emissions on real world driving routes. The measurement method is based on modal analysis of the emission concentrations in the tailpipe of the vehicle, and real time exhaust mass flow determination.

There is a concern that the continuing trend on miniaturization (Moore's law) in IC design and fabrication might have a negative impact on the device reliability. To understand and to possibly quantify the physics underlying this concern and phenomenon, it is natural to proceed from the experimental bathtub curve (BTC) - reliability “passport” of the device. This curve reflects the combined effect of two major irreversible governing processes: statistics-related mass-production process that results in a decreasing failure rate with time, and reliability-physics-related degradation (aging) process that leads to an increasing failure rate. It is the latter process that is of major concern of a device designer and manufacturer. The statistical process can be evaluated theoretically, using a rather simple predictive model.

Future legislations claim further reduction of all restricted emissions as well as the limitation of soot emissions in diesel engines. Special alternative diesel fuels that do not contain aromatic compounds, therefore, promise great potential for further reduction of HC, CO and particulate emissions. During a research project carried out at the Institute for Powertrains and Automotive Technology at the Vienna University of Technology, the potential of alternative diesel fuels was investigated using a state-of-the-art diesel engine with common rail direct injection. The testing took part using an engine test rig as well as on the chassis dynamometer test bench to demonstrate the emission levels in real life conditions. As real biofuel, pure HVO (Hydrogenated Vegetable Oil) was investigated and additionally in different blends with fossil diesel fuel.

Long-term reliability is one of the major requirements for the operation of automotive exhaust aftertreatment systems based on selective catalytic reduction (SCR). For an efficient reduction of nitrogen oxides in the SCR catalyst it is desirable that the thermolysis of the injected urea water solution (UWS) is completed within the mixing section of the exhaust system. Urea might undergo a number of secondary reactions leading to the formation of solid deposits on system walls. A deeper understanding of the mechanisms and influence factors is a basic requirement to prevent and predict undesired decomposition products. This paper outlines the mechanisms of UWS transport and deposition on a typical mixing element geometry. The conditions leading to deposit formation were investigated based on optical and temperature measurements in a box with optical access. A good correlation with the deposit location observed at the close-to-series exhaust system was found.

In the future, conventional powertrains will increasingly be supplied by sustainable energy sources. Long-haul freight transport requires efficient energy storage and the ability to refuel quickly. For this reason, hydrogen-powered PEM fuel cells are being discussed as a future energy source for long-distance vehicles. However, there are numerous challenges in packaging, system cooling and service life. Above all, the dissipation of the fuel cell’s heat losses places high demands on the design of the cooling system due to the relatively low operating temperature. In the presented study, a complete generic drive train of a long-distance commercial vehicle was set up within a suitable simulation environment to investigate the required sizes of the fuel cell stack, the HV battery, the hydrogen tanks, and the cooling circuit.

Experimental studies have shown that knitted wiremesh mixers reduce the formation of solid deposits and improve ammonia homogenization in automotive SCR systems. However, their implementation in CFD models remains a major challenge due to the complex WM geometry. It was the aim of the current study to investigate droplet WM interaction. Essential processes, such as secondary droplet generation, wall film formation, and heat exchange, were analyzed in detail and a numerical model was set up. A box with heat resisting glass was used to study urea-water solution spray impingement on a WM under a wide range of operating conditions. High speed videography was used to identify the impingement regimes. Infrared thermography was applied to investigate WM cooling. In order to determine the impact of the WM on the spray characteristics, the droplet spectrum was measured both upstream and downstream of the WM using the laser diffraction method.

Current commercial vehicles' engines are complex systems with multiple degrees of freedom. In conjunction with current emissions regulations manufacturers are forced to combine highly developed engines with complex aftertreatment systems. A comprehensive simulation model including the engine and aftertreatment system has been set up in order to study and optimize the overall system. The model uses a phenomenological spray combustion model to predict fuel consumption and NO emissions. In addition physical models for the material temperatures and the reaction kinetics were generated for the aftertreatment system. Steady state and transient measurements were used to calibrate the engine as well as the aftertreatment model. The aim for a system-level optimization was a reduction of fuel consumption while meeting emission standards.

In recent years a new combustion phenomenon called Low-Speed Pre-Ignition (LSPI) occurred, which is the most important limiting factor to exploit further downsizing potential due to the associated peak pressures and thus the huge damage potential. In the past there were already several triggers for pre-ignitions identified, whereat engine oil seems to have an important influence. Other studies have reported that detached oil droplets from the piston crevice volume lead to auto-ignition prior to spark ignition. However, wall wetting and subsequently oil dilution and changes in the oil properties by impinging fuel on the cylinder wall seem to have a significant influence in terms of accumulation and detachment of oil-fuel droplets in the combustion chamber. For this reason, the influence of test fuels with different volatility were investigated in order to verify their influence on wall wetting, detachment and pre-ignition tendency.

A naturally aspirated SI engine with port fuel injection was investigated at the Institute for Powertrains and Automotive Technology of the Vienna University of Technology to analyze the impact of the ethanol blend E85 on the full load performance. Measurements and numerical studies with a predictive wall film model have been carried out to explain the mixture cooling, the calorific fluid properties after inlet valve closing and the volumetric efficiency with conventional fuel and E85. It could be shown that only with a detailed modelling of the wall film formation in the inlet port an accurate prediction of the engine's full load performance is possible when studying different fuels with varying fluid properties. Anyway, an integrated approach that includes measurements and numerical investigations is necessary to analyse the mixture preparation and the engine process correctly.

The Selective Catalytic Reduction (SCR) is a promising approach to meet future legislation regarding the nitric oxide emissions of diesel engines. In automotive applications a liquid urea-water solution (UWS) is injected into the hot exhaust gas. It evaporates and decomposes to ammonia vapor acting as the reducing agent. Significant criteria for an efficient SCR system are a fast mixture preparation of the UWS and a high ammonia uniformity at the SCR catalyst. Multiphase CFD simulation is capable to support the development of this process. However, major challenges are the correct description of the liquid phase behavior and the simulation of the ammonia vapor mixing in the turbulent exhaust gas upstream of the SCR catalyst. This paper presents a systematic study of the impact of the turbulence model and the numerical spatial discretization scheme on the prediction of the turbulent mixing process of the gaseous ammonia.

The piston ring and cylinder liner tribosystem is very sensitive. It is a heavily loaded system with high temperature and force exposure. High demands are made on the components in this area. These facts concern not only system components, but also the engine oil which can reach up to 300°C at the inner cylinder walls. High temperatures and force cause oil aging. As a part of the combustion chamber, the piston ring-cylinder liner tribosystem is in close contact with combustion constituents. If alternative fuels like ethanol are used, the influences to this tribosystem have to be investigated. In particular, the impacts of oil aging have to be considered to avoid higher wear and damage to the engine, to assure low fuel consumption, and to extend oil change intervals. Research work on abrasion of the ring-cylinder system was aimed to gain detailed information about the effects on this tribosystem.

Fuel cells as alternative propulsion systems in vehicles can achieve higher driving ranges and shorter refueling times compared to pure battery-electric vehicles, while maintaining the local zero-emission status. However, to take advantage of pure battery electric driving, an externally rechargeable battery can be combined with a fuel cell range extender. As part of a research project, an efficient air supply system for a fuel cell range extender was developed. To this end, a 25 kW PEM fuel cell system test bench was set up. The different parameter influences of the test bench, in particular of the air supply system, were analyzed and evaluated in terms of stack/system efficiency and functionality. The control software of the test bench was specifically developed for the flexible operating parameter variation. All adjustable variables of the system (air ratio, stack temperature, pressure, etc.) were varied and evaluated at steady-state operating points.

Turbocharged diesel engines are popular propulsion systems for automotive applications like trucks or passenger cars because of their high efficiency and advantageous torque characteristic. The high NOx emissions due to their combustion process and missing three-way catalyst are, however, a disadvantage. Consequently, to satisfy future emission legislations, NOx emissions must be reduced. In addition, growing environmental awareness requires reduction of CO2 emissions, respectively, consumption. Hybridization is an effective method to achieve these multiple goals. The general tendency in direction of electrification of the powertrain leads to a diversity of drive concepts. In this context, the study of the entire system is as important as the analysis and evaluation of the interaction of the system components.

In this work we extended the findings from a previous study by the authors on the mechanisms and influence factors of deposit formation in urea-based selective catalytic reduction systems (SCR) [1]. A broader range of operating conditions was investigated in detail. In order to quantify the boundary conditions of deposition, a representative set of deposits was studied during formation and decomposition. A box of heat resisting glass was equipped with a surrogate mixing element to monitor solidification timescales, temperatures and deposit growth. A chemical analysis of the deposits was performed using thermogravimetry. The depletion timescales of individual deposit components were systematically investigated. A moderate temperature increase to 350 °C was deemed sufficient to trigger fast decomposition of deposits formed below 250 °C.