Technical Paper
In-Cylinder Soot Deposition Rates Due to Thermophoresis in a Direct Injection Diesel Engine
1992-09-01
921629
An investigation of the mechanism causing in-cylinder soot deposition in a direct injection diesel engine was carried out. First, an analytical study was undertaken to determine which of following possible deposition mechanisms, thermophoresis, Brownian diffusion, turbulent diffusion, inertial impingement, or electrophoresis were responsible for the deposition of the soot on the combustion chamber walls. Based on a series of numerical models comparing each mechanism under conditions typical of diesel engine combustion, thermophoresis was singled out as the most likely cause of in-cylinder soot deposition. Second, an experiment was performed to test the hypothesis that the soot deposition was caused by thermophoresis. An optical probe was designed to fit an access port in the cylinder head of a Cummins NH250 single cylinder test engine.