Host: The Japan Society of Mechanical Engineers
Name : The Ninth International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2017)
Date : July 25, 2017 - July 28, 2017
To meet stricter fleet consumption limits down sized gasoline engines have been introduced as power units for passenger cars. These engines offer excellent fuel consumption due to high specific loads. But at the same time fuel wall interaction becomes crucial since large amounts of fuel have to be injected into small combustion chambers.
Fuel wall interaction can lead to high particulate emissions and to combustion chamber deposits (CCD) on the piston top and the cylinder head. These deposits have several disadvantages concerning the combustion process such as pre-ignition, increased particulate emission, altered wall heat flux as well as influence on the flow field in the near wall region due to a change in surface roughness.
This study focuses on the change in surface roughness due to CCD. A single cylinder research engine with a prototype cylinder head and a central injector position is used to generate deposits on the piston top as wells as on the cylinder head. The piston has been equipped with a removable sample plate to enable the analysis of the CCD structure by means of an optical profiler. The optical profiler is able to measure the surface roughness without affecting the sensitive deposit structure and to generated a two dimensional map of the surface. To ensure representative results the sample plate is made of aluminum alloy used for commercially available pistons.
In addition to the ex situ measurements of the surface structure the deposit formation has been observed during engine operation using a low speed CCD color camera. In conjunction with the data recorded by the indication system these pictures can be used to evaluate operating behavior and the source of the increased particulate matter emissions during sustained engine operation.
