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The mixture formation of a direct injection HCCI engine was optimized by a new nozzle geometry in combination with a multi-pulse injection scheme. To achieve this injection strategy, a highly flexible Piezo-Common-Rail injection system was used at the single cylinder research engine (DC BR 500, compression ratio reduced to 14:1). Optical probes for local, time resolved temperature and soot concentration measurement (Two-Color-Method) were adapted. Furthermore, a camera system was applied to detect the radiation of UV light (especially emitted by OH radicals which is an important indicator of the ignition process). So, the behaviors of different fuels in regard to the combustion process have been investigated. Diesel, SMDS and mixtures of n-heptane and iso-octane were tested with various EGR ratios, boost pressures and air/fuel ratios.

A phenomenological heat transfer model for direct injection diesel engines has been developed. Utilizing the thermodynamic results of a combustion model as an input, the model is able to predict the temporal variation of the heat losses from the cylinder gas to the cylinder walls. Additionally, the division into isothermal combustion chamber subsurfaces allows the consideration of the spatial variation of the wall heat fluxes. The physical mechanisms such as flow dependent convection, heat radiation due to hot soot particles and isolation effects of deposited soot layers are described in detail. Thus, the effects of these mechanisms on the overall heat transfer can be studied. The heat transfer model was verified successfully by comparison to measured wall heat fluxes in a single-cylinder direct injection diesel engine. It is shown that the effects of engine speed and load, turbo-charging and soot deposition can be predicted with good accuracy.

Two of the objectives in developing internal-combustion engines are to keep wear and - at the same time - the related friction losses between the piston rings and cylinder liner as low as possible. To this end, optimization of the hydrodynamic conditions and designing for reduction of mixed friction have become the goals of many engine manufacturers and developers. As part of this project, a two-dimensional computation model is developed to include modelling of four areas: gas dynamics, lubrication-oil hydrodynamics, solid-body contact, and piston-ring dynamics. The gas pressures in the ring pack are calculated either using the one-dimensional Navier-Stokes equation or the unsteady adiabatic-flow model. The hydrodynamic pressure distribution ranging from the piston-ring running surface to the cylinder wall is calculated by solving Reynold's differential equation for rough surfaces /1/. This was accomplished under the use of flow factors.

The potential of the two-stroke engine has become more and more subject to increasing research work trying to optimise the power-weight ratio as well as the pollutant emissions, especially with the development of high efficient direct injection systems. Doubtless is the scavenging process of the two-stroke engine a most complex and troublesome problem with the numerical simulation or design of new developments. Since the proposal of the perfect mixing model of HOPKINS in 1914 lots of different models have been offered to draw conclusions about the quality of the scavenging process. These may be classified into 3 main categories, the single zone, the multi zone and the fluid mechanical models, while precision and expenditure are increasing dramatically in this order. Every category serves a special purpose. By using single zone models, a simple and handsome way is offered to collect information about the trend behaviour of an engine.