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Knowledge of the relevant cause-effect relationships for the combustion process, such as the interaction between the in-cylinder flow and the combustion behavior, are becoming essential for future combustion engines. Apart from the general interdependencies between the combustion rate and the turbulence intensity, specific combustion concepts, known from lean-burn engines, also strongly depend on the global flow structure which for example controls the mixing processes. Particle tracking velocimetry (PTV) was used to analyse the bulk in-cylinder flow of multi-valve production engines. The PTV results gave rise to well-aimed modifications of the intake ports and thus of the in-cylinder flow in order to achieve an optimized mixing of the charge or to affect the turbulence production during the compression stroke.

A new fiber optic sensor has been used to detect knocking combustion. With this sensor it is possible to detect high frequency signals which are free from electrical and mechanical disturbance. By using the maximum signal rise of the detected optical signals for each combustion cycle, it is possible to clearly seperate knocking and non-knocking cycles. The detected maximum signal rise was used in a preliminary test as the input of a knock control system.

This paper presents investigations on the combustion process in a single cylinder SI engine with direct injection. Different nozzle types are examined i.e. hollow cone nozzles and hole type nozzles both with different geometry of the injected spray. These nozzle types have been compared in view of their suitability of creating a homogeneous as well as a stratified mixture in the combustion chamber. To create a homogenous mixture, the fuel was injected during the intake stroke. In order to examine the homogeneity of the mixture in the case of direct injection, the engine was driven with mixture formation generated through intake port injection. The comparison of the direct injection method with the intake port injection for homogenous mixture formation has shown only small differences in engine behavior. To create a stratified mixture in the combustion chamber, the fuel was injected at the end of the compression stroke.