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CFD has been widely used to predict the flow behavior inside 2-stroke engines over the past twenty years. Usually a mass flow profile or a simple 0D model is used for the inlet boundary condition, which replaces the complete intake geometry, such as reed valve, throttle, and air box geometries. For a CFD simulation which takes into account the exact reed valve geometry, a simulation of all above mentioned domains is required, as these domains are coupled together and thus interact. As the high speed of the engine affects the opening dynamic and closure of the reed valve, the transient data from the crank case volume and the section upstream the reed valve have an important influence on the reed petal dynamic and therewith on the sucked fresh air mass of the engine. This paper covers a methodology for the transient CFD simulation of the reed petals of a 2-stroke engine by using a 2D model.

Discussions about the optimal technology of propulsion systems for future ground vehicles have been raising over the last few years. Several options include different types of technologies. However, those who are advocating conventional internal combustion engines are faced with the fact that fossil fuels are limited. Others favor hydrogen fuel as the solution for the future, either in combination with combustion engines or as an energy carrier for fuel cells. In any case, the production and storage of hydrogen is an ongoing challenge of numerous research works. Finally, there are battery-electric or hybrid propulsion systems in use, gaining more and more popularity worldwide. Ongoing advances in power electronics help to improve control systems within automotive applications. New developed or designed components enable more efficient system architectures and control.

Lean burn combustion concepts with high mean effective pressures are being pursued for large gas engines in order to meet future stringent emission limits while maintaining high engine efficiencies. Since severe boundary conditions for the ignition process are encountered with these combustion concepts, the processes of spark ignition and flame initiation are important topics of applied research, which aims to avoid misfiring and to keep cycle-to-cycle combustion variability within reasonable limits. This paper focuses on the fundamental investigation of early flame kernel development using different ignition system settings. The investigations are carried out on a rapid compression-expansion machine in which the spark ignition process can be observed under engine-like pressure and excess air ratio conditions while low flow velocities are maintained.

The absence of combustion engine noise pushes increasingly attention to the sound generation from other, even much weaker, sources in the acoustic design of electric vehicles. The present work focusses on the numerical computation of flow induced noise, typically emerging in components of flow guiding devices in electro-mobile applications. The method of Large-Eddy Simulation (LES) represents a powerful technique for capturing most part of the turbulent fluctuating motion, which qualifies this approach as a highly reliable candidate for providing a sufficiently accurate level of description of the flow induced generation of sound. Considering the generic test configuration of turbulent pipe flow, the present study investigates in particular the scope and the limits of incompressible Large-Eddy Simulation in predicting the evolution of turbulent sound sources to be supplied as source terms into the acoustic analogy of Lighthill.

Worldwide increasing energy consumption, decreasing energy resources and continuous restriction of emission legislation cause a rethinking in the development of internal combustion engines and fuels. Alternative renewable fuels, so called bio-fuels, have the potential to contribute to environmentally friendly propulsion systems. This study concentrates on the usage of alcohol fuels like ethanol, methanol and butanol in non-automotive high power engines, handheld power tools and garden equipment with the focus on mixture formation and cold start capability. Although bio-fuels have been investigated intensely for the use in automotive applications yet, the different propulsion systems and operation scenarios of nonautomotive applications raise the need for specific research. A zero dimensional vaporization model has been set up to calculate the connections between physical properties and mixture formation.

Dual fuel combustion processes, which burn varying ratios of natural gas and diesel, are an attempt to reach high efficiencies similar to diesel engines while exploiting the CO2 savings potential of natural gas. As shown in earlier studies, the main challenge of this combustion process is the high emission of unburned hydrocarbons during low load operation. Many publications have focused on a layout which utilizes port injection of natural gas and a direct injection of diesel to initiate combustion. However, previous studies indicated that a sequential direct injection of both fuels is more promising. It enables charge stratification of natural gas and air, whereby a remarkable reduction of the unburned hydrocarbon emissions was observed. This work develops this approach further, utilizing a low pressure direct injection of natural gas.

As emission limits become increasingly stringent and the price of gaseous fuels decreases, more emphasis is being placed on promoting gas engines. In the field of large engines for power generation, dual fuel combustion concepts that run on diesel/natural gas are particularly attractive. Knock in diesel/natural gas dual fuel engines is a well known yet not fully understood complex phenomenon that requires consideration in any attempt to increase load and efficiency. Thus combustion concept development requires a reliable yet robust methodology for detecting knock in order to ensure knock-free engine operation. Operating parameters such as rail pressure, start of injection and amount of diesel injected are the factors that influence oscillations in the in-cylinder pressure trace after the start of combustion. Oscillations in the pre-mixed combustion phase, or ringing, are caused by the rapid conversion of large parts of the injected diesel.

Aerodynamic CFD simulations in the automotive industry, which are based on the steady-state RANS (Reynolds-averaged Navier-Stokes) approach typically utilize approximate numerical methods to account for rotating wheels. In these methods, the computational mesh representing the rim geometry remains stationary, and the influence of the wheel rotation on the air flow is modelled. As the rims are considered only in one fixed rotational position (chosen arbitrarily in most cases), the effects of the rim orientation on the aerodynamic simulation results are disregarded and remain unquantified. This paper presents a numerical sensitivity study to examine the impact of the rim orientation position on the aerodynamic parameters of a detailed production vehicle. The simulations are based on the steady-state RANS approach.

High-pressure direct injection (HPDI) of natural gas into the combustion chamber enables a non-premixed combustion regime known from diesel engines. Since knocking combustion cannot occur with this combustion process, an increase in the compression ratio and thus efficiency is possible. Due to the high injection pressures required, this concept is ideally suited to applications where liquefied natural gas (LNG) is available. In marine applications, the bunkering of and operation with LNG is state-of-the-art. Existing HPDI gas combustion concepts typically use a small amount of diesel fuel for ignition, which is injected late in the compression stroke. The diesel fuel ignites due to the high temperature of the cylinder charge. The subsequently injected gas ignites at the diesel flame. The HPDI gas combustion concept presented in this paper is of a monovalent type, meaning that no fuel other than natural gas is used.

Hydrogen nowadays is considered one promising energy carrier for future mobility scenarios. Its application as a fuel in ICEs greatly benefits from Direct Injection (DI) strategies, which help to reduce the disadvantages of PFI systems such as air displacement effects, knocking, backfiring and low power density. In SI-engines one appropriate way to increase efficiency is the reduction of wall heat losses by jet- and/or wall-guided mixture formation systems. In theory, Compression Ignition (CI) systems employing a diffusion type of combustion allow for a significant raise in compression ratio and, thus, are likely to excel the SI concept in terms of efficiency. The following paper deals with results obtained from investigations on H2 Compression-Ignition (H2-CI) combustion systems by employing both thermodynamic research engines and 3D CFD simulation.

Energy politics and environmental circumstances demand novel strategies for private transport. Several studies have shown that one of these possibilities can be an electric vehicle with a range extender - REX. Today these REX engines are under way as derivation from modern internal combustion engines. As the need for an optimized usage of energy will further increase in the future, alternative energy converter systems have to be investigated. For DENSO, as supplier of components, it is of strong interest how the basic layout of these concepts could look like. This is necessary in order to be prepared for the specific needs of these concepts in terms of auxiliaries, electric / electronic components as well as for the cabin climate & various control strategies. In these REX-concepts all energies have to be considered. A sophisticated usage of energy inside a REX vehicle is required which leads to the investigation of a combined heat and power usage on-board.

Research and development engineers have paid much attention to coupling commercial tools for examining complex systems, recently. The purpose of this paper is to demonstrate an automated coupling of a CFD program with a commercial thermal radiation tool. Based on a previous work the coupling behaviour of a parallelized CFD code is being demonstrated. The automation thus speeds up the calculation procedure even for transient simulations not relying on codes of just one vendor. The simulation is then compared with measurements of temperatures of an actual SUV and conclusions are drawn.

Synergies in infrastructure and customer acceptance can be achieved by running internal combustion engines on mixtures of hydrogen and natural gas. Alongside the bridging effect between natural gas and hydrogen, such mixing offers advantages in terms of reduced emissions and improvements to the combustion process. The wide ignition limits and high flame speed of hydrogen have as positive an impact on the combustion of H2NG mixture as does the higher energy density of natural gas on range. A bi-fuel gasoline-natural gas vehicle was adapted to operation with gasoline, natural gas, hydrogen and any H2NG mixtures. For that purpose, the intake manifold was replaced by an aluminum construction, the injectors were replaced and the ECU had to be adjusted. Essentially quality-controlled hydrogen operation was possible throughout the engine map.

In the automotive industry well-established different simulation tools targeting different needs are used to mirror the physical behavior of domain specific components. To estimate the overall system behavior coupling of these components is necessary. As systems become more complex, simulation time increases rapidly by using traditional coupling approaches. Reducing simulation time by still maintaining accuracy is a challenging task. Thus, a coupling methodology for co-simulation using adaptive macro step size control is proposed. Convergence considerations of the used algorithms and scheduling of domain specific components are also addressed. Finally, the proposed adaptive coupling methodology is examined by means of a cross-domain co-simulation example describing a hybrid electric vehicle. Considerable advantages in terms of simulation time reduction are presented and the trade-off between simulation time and accuracy is depicted.

This paper presents an analysis of the potential of E85 (a mixture of 85 % (bio)ethanol and 15 % gasoline) as a fuel for spark-ignition (SI) direct-injection internal combustion engines. This involves investigation of not only application to downsizing concepts with high specific power but also behavior relating to emissions and efficiency at both part and full load. Measurements while running on gasoline were used for comparison purposes. The first stage involved analysis using 1D simulation of two different downsizing concepts with regard to turbocharging potential and performance. Following this, various influential parameters such as injector position, injection pressure, compression ratio, degree of turbocharging etc. were investigated on a single cylinder research engine. In the case of high pressure direct injection, particulate emissions also play an important role, so particulate count and particulate size distribution were also studied in detail.

Focus is pointed on the highly favorable physical properties of hydrogen (H2) with regard to its combustion characteristics in internal combustion engines. Thereby it will be shown in how far the performance of next generation hydrogen engines can be improved by implementing a direct fuel injection system instead of the conventional port injection approach. Results from numerical as well as from experimental investigations will be used to clearly give a vision of the overall future potential of hydrogen for combustion engines in comparison to fuel cell systems.

An efficient and economic method to increase the performance of four stroke engines can be accomplished by utilizing the crankcase supercharging method. The lubrication of the movable parts in the crankcase by mixing the intake air with lubricant leads to a high oil consumption and disadvantages in the emission characteristics. This paper describes parts of a research project with the goal to develop a supercharged four–stroke engine with a closed loop lubrication system for the crank train and the cylinder head. The thermodynamic layout and the development of an oil separating system have been carried out with the help of simulation tools and development work on a flow test bench.

Using natural gas as a fuel in internal combustion engines is a promising way to obtain efficient power generation with relatively low environmental impact. Dual fuel operation is especially interesting because it can combine the safety and reliability of the basic diesel concept with fuel flexibility. To deal with the greater number of degrees of freedom caused by the interaction of two fuels and combining different combustion regimes, it is imperative to use simulation methods in the development process to gain a better understanding of the combustion behavior. This paper presents current research into ignition and combustion of a premixed natural gas/air charge with a diesel pilot spray in a large bore diesel ignited gas engine with a focus on 3D-CFD simulation. Special attention was paid to injection and combustion. The highly transient behavior of the diesel injector especially at small injection quantities poses challenges to the numerical simulation of the spray.

A worldwide decrease of legal limits for CO2 emissions and fuel economy led to stronger efforts for achieving the required reductions. The task is to evaluate technologies for CO2 reduction and to define a combination of such measures to ensure the targets. The challenge therefor is to find the optimal combination with respect to minimal costs. Individual vehicles as well as the whole fleet have to be considered in the cost analysis - which raises the complexity. Hereby, the focus of this work is the consideration and improvement of a new model series against the background of a fleet and the selection of measures. The ratio between the costs and the effect of the measures can be different for the each vehicle configuration. Also, the determination of targets depends whether a fleet or an individual vehicle is selected and has impact on the selection and optimization process of those measures.

Vehicles driven by electric or hybrid technologies have the advantage that a high torque potential can be used from the start, hence the initial vehicle acceleration is higher compared to conventional propulsion concepts [1]. The speed-torque characteristic of electric machines is nearly ideal for the use in automotive applications and electrical machines can be controlled with a high efficiency. The aim of the present work is the examination of different sensor technologies, which are used in such automotive applications to measure the rotor position of electric motors. The project includes the assessment and evaluation of different sensor technologies, e.g. resolver, eddy current sensors and sensors based on magneto-resistive effects. The quality of the sensor angular measurement depends on different parameters, for example misalignment in planar direction, longitudinal direction, tilt angle, temperature, rotational speed and supply voltage.