Warm up of an automotive catalyst substrate by pulsating flow: a single channel modelling approach

Rapid warm up of an automotive catalyst substrate is important for early li ght off. This work considers the results from a model of warm up in a singl e channel. The mass flow is pulsating with high amplitude, about 75% of mea n flow, but without flow reversal. The how regime is laminar within the cha nnel. Pulsations occur with frequency in the range 16-100 Hz, and are impor tant in close-coupled systems where the catalyst is located near to the eng ine and where the rate of rise of gas inlet temperature with time is rapid, about 15 K/s. The use of a single channel model with conjugate heat transf er enables the heat transfer coefficient to be evaluated and compared with results from steady flow simulations. The value of the augmentation factor based on heat flux is found to be less than unity. The value of the augment ation factor based on heat transfer coefficient depends on the method for c alculating the mean heat transfer coefficient, but is generally less than u nity. The changes caused by pulsations will be small in practical systems. Changes in wall temperature found in the simulations are the result of the cumulative effect of changes in the mass flow rate. (C) 2000 Elsevier Scien ce Inc. All rights reserved.