Abstract
This work aims to investigate the possibility to apply open-cell foams as catalytic substrates in SCR systems for Diesel engines, as a replacement of traditional honeycombs. In the literature, many studies compare the performance of foams and honeycombs as catalytic substrates, showing, in general, a better mass transfer behavior in foams, compensated on the other hand by a higher pressure drop. In this work, we consider the low-pressure injection of Ad-Blue and we evaluate the performance of the open-cell foam in enhancing the mixing and the evaporation of the spray. A Eulerian-Lagrangian CFD model has been adopted to simulate the spray evolution and its interaction with the microstructure of the open-cell foam. The model has been applied to evaluate the spray evaporation and the uniformity of the ammonia distribution in different sections of the substrate. Different operating conditions were tested comparing substrates with different geometrical properties. The results of this preliminary analysis can be regarded as promising, showing the capability of the foam to enhance the mixing of the spray and to achieve a uniform distribution of the ammonia over all the catalyst substrate.
Highlights
In the past decades, open-cell foams have been largely studied with possible applications in different fields, ranging from the development of heat-exchange devices to the design of compact catalytic reactors, highlighting their interesting performances in terms of high heat/mass-transfer and low pressure drop [1]
Giani [2] proposed the definition of a performance index to evaluate the mass transfer in relation to the pressure drop induced by the structure: the substrate is more efficient as the mass transfer increases with the same pressure drop or the pressure drop decreases with the same mass transfer
The aim of this work is to explore the possibility to design an novel mixing device based on Periodic Open Cell Structures (POCS) which combines: a) the capability to promote the uniform distribution of the droplets and their mixing with the gas flow; b) the capability to act at the same time as catalytic substrate for the activation of the reactions
Summary
Open-cell foams have been largely studied with possible applications in different fields, ranging from the development of heat-exchange devices to the design of compact catalytic reactors, highlighting their interesting performances in terms of high heat/mass-transfer and low pressure drop [1]. With regards to the specific field of the aftertreatment systems for internal combustion engines, several studies compared open-cell foam substrates with traditional honeycombs. The test showed that the system with open-cell foams was penalized at high flow rates, requiring a specific optimization to be adopted for this application. In the last few years, the recent developments in the Additive Layer Manufacturing (ALM) technology enabled the possibility to design optimized microstructures, giving the spur to further studies in this field of application. Recent examples of application in the field of the catalyst substrate design and application to engine ATS are reported in [5, 6]
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