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In the last few years the requirement to optimize powertrain noise and vibration has increased significantly. This was caused by the demand to fulfill the vehicle's exterior noise legislative limits in Europe, and by increased customer awareness for high ride comfort. Much effort concentrated on the engine and the powertrain as prime sources of noise and vibration in a vehicle. The cranktrain with its moving components is a significant source of noise and vibration excitation within the engine. This paper describes results of investigations to evaluate various design alternatives in respect to NVH. The influences of crankshaft material, of balancing rate and of secondary shaking forces are discussed, with the aim to evaluate these various design options.

A single cylinder engine was modified to study the potential of reducing fuel consumption and emissions in stratified, direct injection, spark ignition engines with the use of air-assisted nozzles. The spray angle of the nozzle was varied (60° and 90°), and two injection strategies were investigated: (I) the fuel was injected in the nozzle prior to transportation into the chamber via the air flow and (II) the fuel was injected directly into the air flow. The results of the engine experiments were compared with the spray characteristic of each configuration. To facilitate the comparison, two-dimensional images of the sprays were recorded under atmospheric conditions. The fuel was visualized using Planar Laser-Induced Fluorescence (PLIF). The optical chamber was equipped with three optical accesses and a standard injection system from a production engine.

In this study, we report experimental investigations on the air/fuel distribution in the combustion chamber of a spark ignition engine during the first stage of combustion, and prior to ignition. Several modifications were made to a single cylinder to give optical access to the combustion chamber via a glass cylinder. These modifications included the addition of electro-magnetic valves, with a strategic placement for internal exhaust gas recirculation (EGR), and a quartz glass cylinder for optical access. With the placement and timing of the electro-magnetic valves and exhaust gas recirculation rates up to 40 % mass, the engine's combustion process was greatly improved. These improvements included a reduction of fuel consumption by 8 % and a reduction in NOx emissions of 90 %. The flow of air/fuel mixture into the combustion chamber was visualized by Planar Laser-Induced Fluorescence (PLIF) and captured as 8-bit gray scale images.

Due to the increased requirements for chain drive systems of 4-stroke internal combustion engines CAE-tools are neccessary to design the optimum dynamic system. In comparison to models used in the past the advantage of the new model CDD (Chain Drive Dynamics) is the capability of simulating the trajectory of each chain link around the drive system. Each chain link is represented by a mass with two degrees of freedom and is coupled to the next by a spring-damper element. The drive sprocket can be moved with a constant or non-constant speed. As in reality the other sprockets are driven by the running chain and can be excited by torques. Due to these unique model features it is possible to calculate all vibration types of the chain, polygon effects and radial or angular vibrations of the sprockets very accurately. The model includes the detailed simulation of a mechanical or a hydraulic tensioner as well.

The study presented in this paper is concerned with the application of a finite element based technique to deal with crankshaft-crankcase interaction. A finite element model of the crankshaft and the crankcase was developed and appropriately reduced. This model was used for a crankshaft optimization, strategy to analyse related effects on the NVH performance with focus on main bearing acceleration. The crankshaft and the cylinder block were modelled using beam and shell elements with structural and dynamic properties correlated up to 1600 Hz. The interaction between crankshaft and the cylinder block was represented by using non-linear properties. Applying this model, the dynamic crankshaft and engine block behaviour and repercussion on NVH performance was analysed by investigating main bearing acceleration.

The NVH optimization is a key issue for the development of future powertrains. This includes the radiated noise in terms of noise level and sound quality as well as the structure-borne noise excitation via the engine mounts. Experience shows that there are generally no single noise relevant components on modern powertrains which dominate the NVH behaviour. In contrast, a good NVH performance can only be achieved if the optimization process includes every single component and excitation. Only the combination of these optimized designs can lead to a first-class powertrain NVH. Within this paper the NVH optimization process of an existing 4-cylinder in-line spark-ignition powertrain is described. Examples for positive NVH designs are presented and their effect on the NVH behaviour are explained. Combining all positive NVH features into the engine resulted in a noise reduction of 3-5 dBA without any negative effect on fuel economy and performance.

We report quantitative experimental investigations on the air/fuel distribution in the combustion chamber of a spark ignition engine prior to ignition and during the first stages of combustion. A four cylinder VW four-stroke engine was modified to give optical access to the combustion chamber via the piston. The fuel concentration was visualised by planar laser-induced fluorescence (PLIF). The choice of an appropriate fuel dopant is very important. Several properties have to be considered simultaneously. The most crucial influence results from the sensitivity to quenching by oxygen. Since fuel distributions recorded at different engine operating conditions wore to be compared on a quantitative scale, this effect had to be taken into account most carefully. The long fluorescence lifetime and the extraordinarily low quenching rate of vapour-phase fluoranthene in a high pressure environment as pertaining to engines led to its choice as dopant.

Two-stroke engine gas exchange simulation requires several significant code modifications in comparison to standard four-stroke application. This paper describes the present work based on the PROMO code. Important features currently modelled are a scavenging model, a crank case model and a reed valve model. First results based on calculations for a crank case scavenged engine show the present state of the code and the influence of some design parameters on the engine performance.

The engine is the most important source of noise and vibration in a passenger car. Together with the oil pan the engine block in general radiates more than 50% of the total engine noise. Additionally structure-borne noise is transferred from the block through the engine mounts into the car body. All design features, which influence the structural integrity of the engine block, will therefore have an impact on the customer perceived noise and vibration behaviour of the vehicle. In order to develop an engine block towards a good noise and vibration performance, the first design decisions at the begin of a new engine programme should support this goal. This will facilitate the further development later on. This paper outlines some possibilities of computation and a testing method applicable in an advanced phase to evaluate different engine block design features without having either the complete engine or even the final design of the engine block.

Due to the high amount of valve train noise in multi-valve engines measures were developed to reduce this noise. These measures are dynamically optimized profiles and cam phasing (small angular shift between neighboured cams). Both measures show a drastic reduction in valve train noise and also overall engine noise but do not have any negative effects on performance, economy and costs. Not only overall noise is improved but also sound quality especially impulsiveness characterized by the Kurtosis factor. To assess these design changes with respect to radiated noise in the early design stage an estimation method was used. The estimation method is based on the calculated force and velocity time histories and shows good correlation with the measured data.

A model for valvetrain dynamics is presented, which aims at both accuracy and efficiency. Important aspects in achieving these aims were (i) to formulate the dynamical equations in terms of deviations from the kinematic displacement. (ii) a tappet stiffness which varies with contact point. (iii) a model of the hydraulic lash adjuster. (iv) a model of valve spring dynamics in terms of spring surge modes. The model results show good agreement with measured accelerations for a DOHC engine with direct acting bucket tappets. Moreover the model allows one to quickly gain an insight into the dynamics of valvetrains.