Modelling warm-up of an automotive catalyst substrate using the equivalentcontinuum approach

To predict automotive catalyst light-off time, an understanding of the proc esses controlling warm-up prior to light-off is necessary. Warming substrat e temperature is predicted by numerical solution of the energy equations us ing the equivalent continuum approach, and predictions are compared with me asurements. The experimental studies on warm-up, without chemical reactions , were performed with the substrates supplied via a sudden expansion or a c onical diffuser. Encouraging agreement is obtained for washcoated and non-w ashcoated, metal and ceramic samples. The important parameters which charac terize the substrate and the warming process are: (hA(v)), the product of t he heat transfer coefficient and the wetted surface area per unit volume; ( rho(w)C(w)), the product of the bulk density and the wall material specific heat; m', the mass flow rate; and xi(t), the rate of rise with time of gas temperature at inlet. The significance of these parameters and their influ ence on warm up is reviewed.