Measurement of the local gas velocity at the outlet of a wall flow particle filter

Recent measurements and models show that the soot distribution and the permeability of the soot layer depend on the selected engine operating points both while loading and during regeneration. The influence of an upstream oxidation catalyst on the soot distribution has been shown. Most interestingly, a radial velocity profile has been observed by an optical measuring technique.

However, in actual practice only the overall pressure drop due to the thousands of parallel channels of a wall flow filter is measured. In order to find out experimentally whether or not aging and thermal instability of diesel particle filter correlate with inhomogeneous flow conditions a simple set-up was developed to measure the outlet velocity profile.

A Prandtl-tube with an inner diameter of 1 mm was scanned in x- and y-direction across the outlet channels of a catalytically coated wall flow filter, which was attached to a blower. The settings of its electro motor were kept constant in all the experiments. The resolution of the micro Prandtl-tube is sufficient to resolve the flow profile of individual channels.

Different loading strategies and a regeneration were examined in a time-sequence.