Gas and particle size characterizations of a soot generator for fouling studies in exhaust gas recirculation systems

Abstract

More new stringent regulations have made fouling one of the major problems affecting the design of EGR systems since their performance must be warranted over the life time of the vehicle. Soot deposition and hydrocarbon condensation are mainly responsible for fouling of EGR cooler in diesel engines, highly dependent on the engines operating conditions. In this work, a study was carried out in an experimental setup designed and assembled for analysing the fouling process in the technologies commonly employed in EGR coolers. A soot generator, mini-CAST burner, has been used to reproduce the conditions particles emitted from diesel engines. This equipment allows to control the size and concentration of soot particles in a controlled environment, avoiding the influence of other variables such as lubricants, fuel composition, etc. Six calibrated points were obtained, changing the combustion conditions, and they were characterized. The fouling layer is deposited on a sample collection surface located in the test section, that is provided with the precise instrumentation (thermocouples and pressure sensors) required. The soot particles diameters found a range from 10nm to 650nm while soot particle concentration varies between 0 to 5E+08 part/cm³, both according to typical values of current diesel engines under EGR conditions. For each point, the exhaust gas composition was determined with an AVL DITEST 1000 gas analyser while a TEXA OPABOX opacimeter was used for the determination of the opacity values. A scanning mobility particle sizer (SMPS) was employed for the measurement of the different particle size distribution generated, the exhaust gas being previously diluted in two stages at different temperatures. In addition, Scanning Electron Microscopy (SEM) and TGA-DSC techniques were carried out to obtain information about morphology and composition of the fouling layer in each experimental point.