Experimental investigation of the role of soot volatile organic fraction in the regeneration of diesel filters

Abstract

This paper involves an experimental investigation of the role of the volatile organic fraction ( VOF ) adsorbed on the diesel particulate, in the initiation of regeneration of a SiC diesel lter installed on a modern diesel engine, run on catalytic additive-doped fuel. VOF adsorption-desorption and oxidation behaviour is mainly determined by performing a thermogravimetric analysis ( TGA) of samples collected directly from a SiC lter installed on the engine running under low-and mediumspeed and low-and medium-load conditions, as more representative of city driving. Based on the TGA analysis results, the percentage VOF content in soot was calculated and mapped as a function of engine speed and load in the range of investigation. The e ect of adsorbed hydrocarbons on the regeneration behaviour was assessed by comparing regeneration experiments with the stepwise load increase for a lter loaded with soot at di erent VOF concentration levels. The appearance of a number of incidents of stochastic regeneration behaviour during loading at low exhaust temperatures with a relative high VOF content was observed and discussed. An e ort was made to correlate regeneration rate with the VOF content in soot and the prevailing engine operation point during loading. This work aims at better understanding of diesel lter behaviour with modern diesel engines and also aims to support improved modelling of fuel-additive assisted regeneration by use of fuel additives at low temperatures (150-400°C ).

Pyrolysis Characteristic Analysis of Particulate Matter from Diesel Engine Run on Diesel/Polyoxymethylene Dimethyl Ethers Blends Based on Nanostructure and Thermogravimetry

“…It can be deduced that the moisture and volatile matter content were very low in the PM samples, which may be related to the sampling method used. In the exhaust pipe, where temperatures are high, most of the volatile materials are present in the gas phase and it is difficult for them to be adsorbed or coagulate into existing PM (Stratakis and Stamatelos, 2003). The oxidation reaction of solid carbon in the PM occurs at high temperatures (400-750°C).…”

“…Pyrolysis kinetic parameters are commonly calculated using the TG curve. This study adopted the method of Stratakis and Stamatelos (2003). Using the Arrhenius formula, the kinetic parameters of the PM samples were calculated from the mass reduction during PM pyrolysis.…”

Experimental investigation of catalytic soot oxidation and pressure drop characteristics in wall-flow diesel particulate filters

“…In chapter 4 and [69], measurements of pressure drop resistance of individual channels of a filter were carried out. The results indicated that there exist significant variations in soot loading or quality [72] among different channels (centre versus periphery of the filter), during the loading phase. This fact hints to the existence of flow maldistribution at filter inlet during the loading phase (centre versus periphery).…”

“…The O2 concentration was calculated by the A/F ratio obtained from the UEGO sensor installed before the filter inlet. The experimental layout of the filter loading-regeneration experiments is presented in Figure 3 • Collected soot characteristics (VOF content [72], etc) and, indirectly, also the effect of • Exhaust gas mass flow rate Fuel additive concentration. The effect of fuel additive concentration on the regeneration was checked at a characteristic medium operation point of 2250 rpm -60 Nm for the catalytic regeneration, employing as reference for the thermal regeneration the non-catalytic regeneration.…”

“…Two characteristic engine operation points were selected for the assessment of differences in VOF content of soot: 3000 rpm -40 Nm (6.8% VOF), versus 1800 rpm -90 Nm (2% VOF). These points are characterized by equivalent total particulate matter emissions and cover a range of filter wall temperatures from 300 o C to 400 o C that is responsible for the VOF variation [72]. Secondary effects due to the dynamic phenomena of adsorption-desorption may also affect soot oxidation kinetics.…”