Homogeneous Operating Strategies in a DI Diesel Engine With Pent-Roof Combustion Chamber and Tumble Charge Motion: Studies on a Single-Cylinder Test-Engine and an Optical Access Engine

This paper discusses a new kind of diesel engine with tumble charge motion, pent-roof combustion chamber and piston with pot recess. At the Robert Bosch GmbH, a conventional single-cylinder test engine and an identical optical access engine were built up to study this new engine concept. In this paper, a first attempt to run homogeneous diesel combustion on this engine is presented. A strategy consisting of three operating points with two to four injections was used. These operating points were first run on the conventional test engine and after that studied on the optical access engine with the same boundary conditions. The information of the image data of the optical access engine was then related to the emission results of the conventional test engine. It was found that it is in fact possible to separate the injection and mixture formation from the combustion, but with the used compression ratio of 18, the ignition delay is too short for a sufficient homogenization of the air-fuel mixture. The attempt to improve the homogenization with earlier injections caused a significant increase of products of incomplete combustion in the emissions.