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For efficiency, the majority of modern diesel engines implement multiple injection strategies, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potential contributor towards pollutant emissions. To investigate the underlying processes, highspeed optical measurements at the microscopic scale were performed inside a motored diesel engine under low load/idling conditions. Visualisation of the injector nozzle surface and near nozzle region permitted an indepth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface when the engine is not fired. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading.

Vibration testing is common in automotive industry validation and gains greater significance with increasing numbers of electrical components, which are particularly suspectable to vibration related failures. While the nature and intention of vibration testing is common, many contradicting testing standards claim to be a one-size-fits-all solution, leading to questions of which standard is correct for any specific application. This is compounded by the vast variation in vehicle types and applications (suspension systems, dampers, powertrain mass, tire radius, intended usage, etc.) This paper seeks to offer and demonstrate a method to determine characteristic vibration profiles, based on vehicle classes, and illuminate the process to accelerate these to an appropriate test profile. This can either be used to directly validate a system or to support the selection of the most appropriate vibration profile from options within standards.

Validation of powertrain systems is nowadays performed with specific durability relevant load cycles, which represent the lifetime requirement of individual powertrain components. The definition of such durability relevant load cycles, which are used for vehicle testing should ideally be based on the actual vehicle's usage. Recording driving cycles within a vehicle is one of the most typical ways of collecting vehicle usage and relevant end customer behavior, but the generation of such measured vehicle data can be time consuming. In addition, this method of capturing on-road measurements has limitations in the variation of vehicle loadings (e.g., number of passengers, luggage, trailer usage etc.). Especially for new applications, entering new target markets, these kinds of in-vehicle measurements are not possible in early development stages, as the required vehicle or powertrain configuration is not available in hardware or incapable of measurements.

Due to more challenging future emission legislations and the trend towards downsizing, the number of turbocharged (TC) engines, especially petrol engines, is steadily increasing. The usage of TC has high risk to cause different noise phenomena apparent in the vehicle interior which are often perceived as annoying for the passengers. In order to further improve consideration of TC topics in the development, objective judgment and monitoring of TC noise issues is of high importance. Therefore, objective parameters and corresponding tools that are especially focusing on TC noise phenomena have to be developed. One main target of these tools is to deliver an objective TC assessment in an efficient way and with minimum additional effort. Application of the criteria presented in this publication therefore allows acoustic engineers to judge the NVH behavior and annoyance of the TC with respect to its vehicle interior noise contribution.

Expansion chamber mufflers are commonly applied to reduce noise in HVAC. Dissipative materials, such as microperforated plates (MPPs), are often applied to achieve a more broadband mitigation effect. Such mufflers are typically characterized in the frequency domain, assuming time-harmonic excitation. From a computational point of view, transient analyses are more challenging. A transformation of the equivalent fluid model or impedance boundary conditions into the time domain induces convolution integrals. We apply the recently proposed finite element formulation of a time domain equivalent fluid (TDEF) model to simulate the transient response of dissipative acoustic media to arbitrary unsteady excitation. As most time domain approaches, the formulation relies on approximating the frequency-dependent equivalent fluid parameters by a sum of rational functions composed of real-valued or complex-conjugated poles.

Despite the increasingly stringent emissions legislation, users and owners of commercial diesel vehicles are continually demanding that each new engine generation is more economical than the previous one. This is especially important for commercial vehicles where the majority of engines are in the 1-2ltr./cyl. class. The demands are being reflected in new engine designs with lower friction and improved structural stiffness, together with fuel systems having increased pressure capability, higher spill rates, injection rate shaping and advanced control features. These fuel system requirements have led to a variety of new fuel injection systems and in the search for increased injection pressure these fuel systems have placed greater demands on the engine, especially in areas such as the cylinder head and fuel system drive, sometimes with adverse effects on the combustion and fuel injection system induced mechanical noise.

Knocking combustion places a major limit on the performance and efficiency of spark ignition engines. Spontaneous ignition of the unburned air-fuel mixture ahead of the flame front leads to a rapid release of energy, which produces pressure waves that cause the engine structure to vibrate at its natural frequencies and produce an audible ‘pinging’ sound. In extreme cases of knock, increased temperatures and pressures in the cylinder can cause severe engine damage. Damage is thought to be caused by thermal strain effects that are directly related to the heat flux. Since it will be the maximum values that are potentially the most damaging, then the heat flux needs to be measured on a cycle-by-cycle basis. Previous work has correlated heat flux with the pressure fluctuations on an average basis, but the work here shows a correlation on a cycle-by-cycle basis. The in-cylinder pressure and surface temperature were measured using a pressure transducer and eroding-type thermocouple.

Rattle noise produced in the vehicle interior due to broadband excitation by road irregularities is a major concern with respect to driving comfort, and therefore has become one of the most important topics of acoustic development in recent years. A quantification i.e. measurement of this rattle noise is of fundamental importance for systematic development work and production control. Common noise level measurements (dB, dBA, etc. ) do not represent the rattle character in the vehicle interior as revealed during initial investigations. To overcome this problem and to substitute the subjective assessment with a combination of measurable parameters, the psychoacoustic software AVL-EAR was applied to create an Interior Rattle Quality Index. Based on more than 40 different vehicles that have been subjectively assessed by approximately 70 test persons, the index was generated by means of multiple pair comparisons and statistics on measurement data.

Today, the number of downsized engines with two or three cylinders is increasing due to an increase in fuel efficiency. However, downsized engines exhibit unbalanced interior sound in the range of their optimal engine speed, largely because of their dominant engine orders. In particular, the sound of two-cylinder engines yields half the perceived engine speed of an equivalent four-cylinder engine at the same engine speed. As a result when driving, the two-cylinder engine would be shifted to higher gears much later, diminishing the expected fuel savings. This contribution presents an active in-car sound generation system that makes a two-cylinder engine sound like the more familiar four-cylinder engine. This is done by active, load-dependent playback of signals extracted from the engine vibration through a shaker mounted on the firewall. A blind test with audio experts indicates a significant reduction of the engine speed when shifting to a higher gear.

The automotive trend towards increased levels of electrification is showing a clear direction for hybrid technologies. Nowadays Mild- and plug-in-hybrids open a very wide area of future developments whereas battery electric vehicles (BEV) are still evident but still perceived as niche products with limited production volumes. Nevertheless, major OEMs are working on these kinds of vehicles and have also brought such EV concepts into series production. All of these designs show a clear trend that, beside the topic of electric traction motor and energy storage systems, the internal combustion engine (ICE) is also coming into focus again. In many of these vehicles the range extender (RE) unit is foreseen as an emergency unit to recharge the batteries if the state of charge (SOC) is too low. One of the major advantages of a BEV over other designs is the very good acoustic behavior, so the NVH performance becomes the most challenging topic for RE development.

The sealing effect of piston rings in reciprocating engines have a major impact on blow-by and lube oil consumption (LOC). The sealing is achieved by the gas forces acting on the top and back side of the rings. In addition, the load in the radial direction is increased by the initial ring tension. Inertia forces arising from the oscillating vertical stroke and shear forces due to the secondary piston movement influence this sealing effect by a reduction in contact pressure. Numerical simulation of the piston and ring dynamics solves this non-linear problem and predicts the interaction between piston secondary motion, axial ring motion, and 2nd land pressure. This paper describes the modeling of the cylinder kit dynamics of a six-cylinder truck diesel engine for several operating conditions and ring modifications. The influence of boundary conditions and adjustment parameters on piston ring motion and gas penetration was investigated.

The target of the investigation is the particular influence of a fuel injection system and its components as a noise source in automotive engines. The applied methodology is demonstrated on an automotive Inline 4-cylinder Diesel engine using a common rail system. This methodology is targeted as an extension of a typical standard acoustic simulation approach for combustion engines. Such approaches basically use multi-body dynamic simulation with interacting FEM based flexible structures, where the main excitation crank train, timing drive, valve train system and piston secondary motion are considered. Within the extended approach the noise excitation of the hydraulic and mechanical parts of the entire fuel system is calculated and subsequently considered within the multi-body dynamic simulation for acoustic evaluation of structural vibrations.

In a joint research project between industrial companies and a number of research institutes, nitrogen oxide conversion in oxygen containing exhaust gas has been investigated according to the following procedure Basic investigations of elementary steps of the chemical reaction Production and prescreening of different catalytic material on laboratory scale Application oriented screening of industrial catalyst material Catalyst testing on a lean bum gasoline engine, passenger car diesel engines (swirl chamber and DI) and on a DI truck engine Although a number of solid body structures show nitrogen oxide reduction by hydrocarbons, only noble metal containing catalysts and transition metal exchanged zeolites gave catalytic efficiencies of industrial relevance. A maximum of 25 % NOx reduction was found in the European driving cycle for passenger cars, about 40 % for truck engines in the respective European test.

Modern Diesel engines require an integrated development of combustion strategies, air management and exhaust aftertreatment. This study presents a comprehensive simulation approach with the aim to support engine development activities in the virtual environment. A real-time capable engine, vehicle and control model is extended by three key features. First, a pollutant production model is embedded in a two-zone cylinder model. Second, a framework for catalytic pollutant conversion is built focusing on modern diesel exhaust aftertreatment systems. Third, an extended species transport model is introduced considering the transport of pollutants through the air path. The entire plant model is validated on the example of a passenger car Diesel engine. The predicted engine behavior is compared with steady-state measurements. The NO formation model is investigated for a series of steady-state and transient operating conditions.

A growing development of hybrid or fully electrical drives increases the demand for an accurate prediction of noise and vibration characteristics of electric and electronic components. This paper describes the numerical and experimental investigation of noise emissions from power electronics, as one of the new important noise sources in electric vehicles. The noise emitted from the printed circuit board (PCB) equipped with multi-layer ceramic capacitors (MLCC) is measured and used for the calibration and validation of numerical model. Material properties are tuned using results from experimental modal analysis, with special attention to the orthotropic characteristic of the PCB glass-reinforced epoxy laminate sheet (FR-4). Electroacoustic excitation is pre-calculated using an extension of schematic-based EMC simulation and applied to the structural model. Structural vibrations are calculated with a commercial FEM solver with the modal frequency response analysis.

Direct injection Diesel engines are a propulsion technology that is continuously developed to meet emission standards. Great optimization potential lies in the combustion process itself. The application of closed loop combustion control allows reacting online to environmental conditions and stabilizing the combustion regarding performance and emissions. Dedicated real-time plant models help to develop and calibrate control algorithms in office and hardware in the loop environments. The present work describes a real-time capable, crank-angle resolved engine, cylinder and combustion model. The cylinder applies an 0D, two-zone approach and a phenomenological combustion model describes ignition delay, premixed and diffusive combustion. The latter is enhanced by a quasi-dimensional description of the injection spray. The model is validated with dedicated measurements. The plant model is applied in two use-cases for closed loop combustion control.

The reduction of acoustic excitation due to piston slap as well as friction loss power and seizure are main issues when simulating the oil film lubricated piston - cylinder contacts of internal combustion engines. For a correct representation of the contact conditions between a piston skirt and a cylinder liner surface both the dynamics of the contacting flexible bodies, the shape of the contacting surfaces, the amount of available oil and the properties of the lubricant itself play important roles. Besides an appropriate representation of the hydrodynamic load carrying capacity using an averaged Reynolds equation with laminar flow conditions, the simulation has to use an appropriate asperity model to consider the mixed lubrication condition. The lubricant properties are in particular influenced by its thermal conditions.

A new category of hypereutectic aluminum liners, made by PM route is now available on the market (SILITEC) and it is successfully applied to high-pressure die casting process to produce open deck cylinder blocks. The claimed achievable engine performances over cast-iron liners (weight saving, reduction of oil consumption, optimal heat transfer, wear and friction losses reduction) justify the interest of automotive industry in developing such a technology. The paper will present the experience and the achieved results in permanent mold gravity casting with Silitec liners, where metal flow definition and temperature distribution control make the casting technique more challenging for the manufacturing of closed deck cylinder blocks.

Modern powertrain noise investigation in the development process and during trouble shooting is a combination of experiment and simulation. In simulation in recent years main focus was set on model completeness, consideration of all excitation mechanisms and efficient and stabile numerical algorithms. By that the total response of the virtual powertrain is already comparable to the overall noise level of the real powertrain. Actual challenge is to trace back the overall response to its main excitation and noise generating mechanism as well as to their main driving parameters to support the engineer not only in reaching absolute values, but also to derive the root cause of a response or potential problem and to get hints on how to improve the specific behavior. Approaches by parameter sensitivity studies are time consuming and not unambiguous.

The parameterization of the electrochemical pseudo-two-dimensional (P2D) model plays an important role as it determines the acceptance and application range of subsequent simulation studies. Electrochemical impedance spectroscopy (EIS) is commonly applied to characterize batteries and to obtain the exchange current density and the solid diffusion coefficient of a given electrode material. EIS measurements performed with frequencies ranging from 1 MHz down to 10 mHz typically do not cover clearly isolated solid state diffusion processes of lithium ions in positive or negative electrode materials. To extend the frequency range down to 10 μHz, the distribution function of relaxation times (DRT) is a promising analysis method. It can be applied to time-domain measurements where the battery is excited by a current pulse and relaxed for a certain period.