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The present contribution gives an overview of the use of different simulation tools for the optimization of injection parameters of a diesel engine. With a one-dimensional tool, the behavior of the mechanics and fluid dynamics of the entire injection system is calculated. This simulation provides information on the dynamic needle lift, injection rates, pressures, etc. The flow within the injector is simulated using a three-dimensional CFD tool. By use of a two-phase model, it is possible to analyze the cavitating flow inside the injector and to calculate the effective nozzle hole area as well as the exit flow characteristics. Mixture formation, combustion and pollutant formation simulation is performed adopting three-dimensional CFD. In order to provide the initial and boundary conditions for the engine CFD simulation and to optimize the engine cycle performance a one-dimensional tool is adopted.

The internal combustion engines, and the heavy duty truck diesel engines in particular, are facing a severe challenge to cope with the upcoming stringent emission legislation world-wide. To comply with these low limits, engine internal measures must be complemented with exhaust gas aftertreatment systems with sophisticated electronic control. A reduction of NOx and particulate emission of more than 90% is required. Various strategies to comply with Euro 4, 5 and US 2007 are discussed, also in view of engine performance, fuel economy and cooling system load. Recommendations are given for the most suitable approach to comply also in future with emission legislation in Europe and the United States.

In the near future the effort on the development of exhaust gas treatment systems must be increased to meet the stringent emission requirements. If the relevant physical and chemical models are available, the numerical simulation is an important tool for the design of these systems. This work presents a CFD model that allows to cover the full range of applications in this area. After a detailed presentation of the theoretical background and the modeling strategies results for the simulation of a close-coupled catalyst are shown. The presented model is also applied to the oxidation of nitrogen oxides, to a diesel particle filter and a fuel-cell reformer catalyst.

Partial flow sampling methods in emissions testing are interesting and preferred because of their lower cost, smaller size and applicability to engines of all sizes. However the agreement of the results obtained with instruments based on this method to those obtained with the traditional, large tunnel full flow sampling systems needs to be achieved, and the factors of construction that influence this agreement must be understood. These issues have received more attention lately in connection with ISO and WHDC standardization efforts underway to achieve a world-wide harmony in the sampling methods for heavy duty diesel engines, and with the introduction of similar Bag-minidiluter techniques into light duty SULEV gaseous pollutant measurement. This paper presents the theory and practice of a partial flow probe and tunnel design that addresses and minimizes the undesirable effects of the necessary differences between the two sampling methods.

A broad variety of new technologies for improving fuel economy is currently under development or investigation. The general statement is that always a compromise between fuel economy benefit and engine oncost has to be found. This paper describes a new way for improving fuel economy based on existing technologies used in a refined way. It is shown that with very simple and robust measures on the intake and exhaust ports and on the valve train mechanism 2 valve and 4 valve engines can show a significant improvement in fuel consumption without having a great cost penalty for production. The basic system consists of a single cam phaser and a special port arrangement on a 2 valve engine with a single camshaft operated at stoichiometric air/fuel ratio utilizing internal EGR and a reverse “Miller-Cycle”. Variable charge motion is generated using a shared flow through the intake and the exhaust port by varying cam timing.

Exhaust emission legislation world-wide have a common trend towards very low limits, measured for compliance in transient cycles specific for the United States, Japan and Europe. The emission development strategy is focussing on lowest engine-out emissions to require a minimum of exhaust gas aftertreatment. The base engine concept is described and test results, complying with Euro 4, are shown. The emission reduction development for future regulations requires exhaust gas aftertreatment, test results are shown for US 2007, JNLTR and Euro 5. With exhaust gas aftertreatment, discussed in the appendix, the engine development is faced with a big challenge to ensure the minimum exhaust gas temperature required for their proper function.

In recent years several new gasoline engine technologies were introduced in order to reduce fuel consumption. Controlled autoignition seems to be an alternative to stratified part load operation, which is handicapped due to it's lean aftertreatment system for world wide application. The principal advantages of controlled auto ignition combustion under steady state operation - combining fuel economy benefits similar to stratified charge systems with nearly negligible NOx and soot emissions - are already well known. With the newly developed AVL- CSI system (Compression and Spark Ignition), a precise combustion control is achieved even under transient operation. For compensation of production and operation tolerances a cost optimized cylinder individual control was developed. Completely new functionalities of the engine management system are applied. This lean GDI concept complies with future emission standards without DeNOx catalyst and can be applied worldwide.

Turbulent combustion modeling in a RANS or LES context imposes the challenge of closing the chemical reaction rate on the sub-grid level. Such turbulent models have as their two main ingredients sources from chemical reactions and turbulence-chemistry interaction. The various combustion models then differ mainly by how the chemistry is calculated (level of detail, canonical flame model) and on the other hand how turbulence is assumed to affect the reaction rate on the sub-grid level (TCI - turbulence-chemistry interaction). In this work, an advanced combustion model based on tabulated chemistry is applied for 3D CFD (computational fluid dynamics) modeling of Diesel engine cases. The combustion model is based on the FGM (Flamelet Generated Manifold) chemistry reduction technique. The underlying chemistry tabulation process uses auto-ignition trajectories of homogeneous fuel/air mixtures, which are computed with detailed chemical reaction mechanisms.

A computational study of the flow in intake port geometries has been performed. Three different intake port geometries, namely two combined tangential and helical ports and one quiescent port were analyzed. Each of these cases was calculated for different valve lifts and the results were compared with available measurements. The focus of this paper is on the performance assessment of the variable resolution Partial-Averaged Navier-Stokes (PANS) method. Calculations have been also performed with the Reynolds-averaged Navier-Stokes (RANS) model, which is presently a state-of-the-art approach for this application in the industry. Besides the averaged integral values like a discharge coefficient and a swirl coefficient, the predicted velocity magnitude fields at the measured cross sections of the ports are compared due to available Particle Image Velocimetry (PIV) measurements.

Combustion of premixed stoichiometric charge is free of soot particle formation. Consequently, the development of direct injection (DI) spark ignition (SI) engines aims at providing premixed charge to avoid or minimize soot formation in order to meet particle emissions targets. Engine development methods not only need precise engine-out particle measurement instrumentation but also sensors and measurement techniques which enable identification of in-cylinder soot formation sources under all relevant engine test conditions. Such identification is made possible by recording flame radiation signals and with analysis of such signals for premixed and diffusion flame signatures. This paper presents measurement techniques and analysis methods under normal engine and vehicle test procedures to minimize sooting combustion modes in transient engine operation.

Different particulate mass (PM) portable emission measurement systems (PEMS) were evaluated in the lab with three heavy-duty diesel engines which cover a wide range of particle emission levels. For the two engines without Diesel Particulate Filters (DPF) the proportional partial flow dilution systems SPC-472, OBS-TRPM, and micro-PSS measured 15% lower PM than the full dilution tunnel (CVS). The micro soot sensor (MSS), which measures soot in real time, measured 35% lower. For the DPF-equipped engine, where the emissions were in the order of 2 mg/kWh, the systems had differences from the CVS higher than 50%. For on-board testing a real-time sensor is necessary to convert the gravimetric (filter)-based PM to second-by-second mass emissions. The detection limit of the sensor, the particle property it measures (e.g., number, surface area or mass, volatiles or non-volatiles) and its calibration affect the estimated real-time mass emissions.

With upcoming emission regulations particle emissions for GDI engines are challenging engine and injector developers. Despite the introduction of GPFs, engine-out emission should be optimized to avoid extra cost and exhaust backpressure. Engine tests with a state of the art Miller GDI engine showed up to 200% increased particle emissions over the test duration due to injector deposit related diffusion flames. No spray altering deposits have been found inside the injector nozzle. To optimize this tip sooting behavior a tool chain is presented which involves injector multiphase simulations, a spray simulation coupled with a wallfilm model and testing. First the flow inside the injector is analyzed based on a 3D-XRay model. The next step is a Lagrangian spray simulation coupled with a wallfilm module which is used to simulate the fuel impingement on the injector tip and counter-bores.

Accurate simulation tools are needed for rapid and cost effective engine development in order to meet ever tighter pollutant regulations for future internal combustion engines. The formation of pollutants such as soot and NOx in Diesel engines is strongly influenced by local concentration of the reactants and local temperature in the combustion chamber. Therefore it is of great importance to model accurately the physics of the injection process, combustion and emission formation. It is common practice to approximate Diesel fuel as a single compound fuel for the simulation of the injection and combustion process. This is in many cases sufficient to predict the evolution of the in-cylinder pressure and heat release in the combustion chamber. The prediction of soot and NOx formation depends however on locally component resolved quantities related to the fuel liquid and gas phase as well as local temperature.

During recent years several VVT devices have been developed, in order to improve either peak power and low end torque, or part load fuel consumption of SI engines. This paper describes an experimental activity, concerning the integration of a continuously variable cam phaser (CVCP), together with an intake port deactivation device, on a small 4 cylinder 16V engine. The target was to achieve significantly lower fuel consumption under normal driving conditions, compared to a standard MPFI application. A single hydraulic cam phaser is used to shift both the intake and the exhaust cams to retarded positions, at constant overlap. Thus, high EGR rates in the combustion chamber and late intake valve closure (“reverse Miller cycle”) are combined, in order to reduce pumping losses at part load.

The paper describes a feasibility test program on a 2 liter, 4 cylinder DI/TCI passenger car engine operated on the new alternative fuel Dimethyl Ether (DME, CH3 - O - CH3) with the aim of demonstrating its potential of meeting ULEV emissions (0.2 g/mi NOx in the FTP 75 test cycle) when installed in a full size passenger car. Special attention is drawn to the fuel injection equipment (FIE) as well as combustion system requirements towards the reduction of NOx and combustion noise while keeping energetic fuel consumption at the level of the baseline DI/TCI diesel engine. FIE and combustion system parameters were optimized on the steady state dynamometer by variation of a number of parameters, such as rate of injection, number of nozzle holes, compression ratio, piston bowl shape and exhaust gas recirculation.

The influence of fuel density on exhaust emissions from diesel engines has been investigated in a number of studies and these have generally concluded that particulate emissions rise with increasing density This paper reviews recent work in this area, including the European Programme on Emissions, Fuels and Engine Technologies (EPEFE) and reports on a complementary study conducted by CONCAWE, in cooperation with AVL List GmbH The project was carried out with a passenger car equipped with an advanced technology high speed direct injection turbocharged / intercooled diesel engine fitted with a complex engine management system which was referenced to a specific fuel density This production model featured electronic diesel control, closed loop exhaust gas recirculation and an exhaust oxidation catalyst Tests were carried out with two EPEFE fuels which excluded the influence of key fuel properties other than density (828 8 and 855 1 kg/m3) Engine operation was adjusted for changes in fuel density by resetting the electronic programmable, read-only memory to obtain the same energy output from the two test fuels In chassis dynamometer tests over the ECE15 + EUDC test cycle the major impact of fuel density on particulate emissions for advanced engine technology/engine management systems was established A large proportion of the density effect on particulate and NOx emissions was due to physical interaction between fuel density and the electronic engine management system Limited bench engine testing of the basic engine showed that nearly complete compensation of the density effect on smoke (particulate) emissions could be achieved when no advanced technology was applied

An optical sensor system provides access to standard SI engine combustion chambers via the cylinder head gasket. Flame radiation within the plane of the gasket is observed with optical fibers which are arranged to allow the tomographic reconstruction of flame distribution. The effect of convective in-cylinder air motion generated by variations of inlet ports and combustion chamber geometries on flame propagation is directly visible. A high degree of correlation between flame intensity distribution and NOx emission levels yields a useful assessment of combustion chamber configurations with minimum emission levels. The location of knock centers is identified.

This report shows the methods, which AVL uses for the calculation of gear box noise. The analysis of the gear box structure (housing) is done using finite element method (FEM), thereby the natural frequencies are calculated as well as forced vibrations. As input for the FE calculation of the forced vibrations, the dynamic bearing forces of the shafts in the gear box or the dynamic tooth mesh are used. These forces are determined using the MBS (multi body system) software GTDYN, considering the torsional vibrations as well as axial and bending vibrations. Several examples of calculation results for the investigation of the gear dynamics are shown within the scope of this report.

The characteristically good fuel economy of the high speed direct injection diesel engine has led to increased market share as the power unit of passenger cars. This trend is particularly true in Europe and, if not halted prematurely by emissions legislation, is likely to continue. However, another characteristic of the high speed DI engine is increased noise and vibration over its gasoline counterpart. This has meant that additional noise and vibration measures are required in order to approach the competitive refinement levels of gasoline engine installations. This paper considers some of the characteristic diesel engine noise and vibration problems associated with vehicle installation and passenger comfort. The paper also discusses subjective and objective assessment and considers approaches to engineering more desirable sound quality.

The requirement for increased power and reduced emission and fuel consumption levels for diesel engines has created very stringent demands on the cylinder head design. In current engine development programs it is often observed that the limiting design factor is given by the thermal mechanical fatigue strength of the cylinder head. Design iterations resulting from durability testing are often necessary due to the lack of adequate simulation techniques for prediction thermal mechanical fatigue (TMF) failure. A complete lifetime simulation process is presented in this paper with emphasis on a newly developed material model for describing the constitutive behavior of cast iron (i.e. gray cast iron and compacted graphite iron) under thermal cycling. The material model formulation is based on a continuum-damage-mechanics (CDM) approach in order to account for the tension / compression anomaly of cast iron.