The Effect of Pulsations in Conditions related to Catalytic Converters

The effect of pulsations in a catalyst converter is investigated with the aim of determining if a steady flow captures the same physical phenomena as the pulsating flow. For this specific case, guide vanes are mounted in the sudden expansion to obtain a uniform inlet flow to the catalytic layers. The test rig is successfully validated against other similar measurements, done with a steady flow.

The experiments are carried out with a Reynolds number of 105, a Womersley number orders of magnitude larger than 1, but with an ratio between the fluid though time and pulsation period below one. This last part results in a quasi-static boundary condition. For the present setup different amplitudes and pulsation frequencies are investigated.

It is thus shown experimentally that they have no influence on the mean flow. A repeatability study has been conducted which shows an overall repeatability of around 2%. An error is observed, where unwanted fractions of the packing block parts of the catalyst dummy. These fractions influence the velocity fields by clogging the hules of the catalyst dummy, but the influence is assumed to be small.

Based on the results it is concluded that the mean flow field for this case is independent of the pulsations. When air enters the system a vortex ring appears in front of the catalyst dummy.