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

Abstract

This paper presents the results of studies on a range of different catalyst substrates warmed by engine exhaust. Engine speeds were in the range 1200–3000 r/min. 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 one-dimensional computational fluid dynamics (CFD) model. The model was based on the porous medium approach and incorporated a simple three-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.