Automotive catalyst warm-up to light-off by pulsating engine exhaust

This paper presents the results of studies on a range of different catalyst substrates warmed by engine
exhaust. Engine speeds were in the range 1200 to 3000 rpm. One substrate was non-washcoated, four
were washcoated but non-reactive, and four were washcoated and reactive. The temperature at four
locations within the non-reactive substrates was measured. The reactive substrates were warmed to
light off by the pulsating exhaust flow from an engine running fuel rich of stoichiometric. Both
substrate temperatures and hydrocarbon conversion were measured. Predicted temperatures and
conversion were obtained from a 1D CFD model. The model was based on the porous medium
approach and incorporated a simple 3-way chemical scheme. Comparison was made of measurements
with predictions, with particular reference to the time taken to achieve light-off. Pulsing flow CFD
predictions were found to be almost identical to steady flow predictions for the conditions investigated.
The CFD predictions were found to be in fair agreement with the engine test results, but using kinetic
rate constants higher than previously reported values.