A Numerical Investigation of the Combined Effects of Initial Temperature and Catalyst Activity on the Dynamics of Soot C
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ORIGINAL PAPER
A Numerical Investigation of the Combined Effects of Initial Temperature and Catalyst Activity on the Dynamics of Soot Combustion in a Catalytic Diesel Particulate Filter Gianluca Landi1 · Valeria Di Sarli1 · Luciana Lisi1 Accepted: 28 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In the work presented in this paper, the combined effects of initial temperature and catalyst activity on the regeneration dynamics of a catalytic diesel particulate filter (DPF) have been investigated. To this end, CFD-based simulations of soot combustion in a single-channel configuration were performed. In the model, all the soot trapped inside the filter was assumed to be in contact with the catalyst. The initial temperature of the filter was varied over a wide range independently of the inlet gas temperature, which was kept constant. Numerical results have shown that three main different behaviors arise depending on catalyst activity. At low catalyst activity, as the initial temperature is increased, an abrupt transition occurs from a regime of slow regeneration, characterized by long times (around 10 min) and low peak temperatures (~ 700 K), to a regime of fast regeneration, characterized by short times ( 600 °C), active measures (e.g., fuel burners, electric heating—upstream or embedded in the filter through the use of heating wires, microwave heating, injection of fuel in the exhaust, recirculation of exhaust gas, etc.) can be employed. Such an approach, also referred to as thermal regeneration, implies additional energy costs and requires complex control systems. Furthermore, in some cases, it may lead to the formation of excessively hot regions, and DPF substrates may suffer thermal damage with peak temperatures above 1200 °C [2].
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Topics in Catalysis
Catalytic (i.e., catalyst-coated) DPFs have been proposed as an alternative or complementary approach to overcome or mitigate the drawbacks of thermal regeneration [3]. In the presence of a catalyst, at least in principle, it is possible to perform soot oxidation at much lower temperatures (250–550 °C) than those required by the thermal process and/or to shorten the regeneration time period, thus allowing for energy saving (at an added cost of the catalyst). However, the effective ability of a catalyst to oxidize soot at low temperatures is strictly dependent not only on its activity [4, 5], but also on the intensity of soot-catalyst contact [4–8]. It has been shown that, in order to maximize this intensity, it is essential to achieve a high dispersion with a deep penetration of catalyst inside the macro-pores of the filter walls and, at the same time, to minimize/avoid the accumulation of soot in the form of cake on top of the catalytic walls [6, 7]. Indeed, the cake is substantially segregated from the catalyst and, thus, its combustion takes place mainly via the thermal path [6]. The formation of hot zones is still an issue for regeneration of catalytic DPFs. On the other hand, the int
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