A study of the early life of gasoline particulate filters: Reactive and dissipative acoustic effects

Abstract

The presence of after-treatment systems (ATS) has some side effects as they modify the wave dynamics, back-pressure and acoustic behavior of the exhaust system, that define the boundary conditions for the main silencing device. Gasoline particulate filters (GPF) have a considerable influence on these traits as their working principle depends on wall-flow monoliths; additionally, particulate filters have an inherent transient behavior due to the loading-regeneration cycles during their operation. In this paper, the steady and unsteady behavior of a typical device containing a three-way catalyst (TWC) and a GPF has been characterized in "new" (prior to any use) and "used" (after regeneration) conditions, with special focus on the role of dissipation. Pressure drop measurements were used in steady flow, whereas an acoustic energy balance was performed in the unsteady case that allows for the identification of the reactive and dissipative contributions. The results obtained for the GPF suggest that after it has been used for a relatively short time it oscillates between a maximum and a minimum loading over load–regeneration cycles burning the soot, never reaching back brand–new cleanness due to accumulation into the substrate pores and only suffering from ash accumulation over very long times. The results were then used to analyze the ability of a standard gas-dynamic code to reproduce the influence of the loading on the reactive and dissipative effects observed, with the main conclusion that by properly tuning the model parameters it is possible to reproduce, at least qualitatively, the trends observed in the experiments. The model can thus be used to provide adequate inlet conditions for the design of the exhaust line.

Acoustic and fluid-dynamic characterization of state-of-the-art exhaust after-treatment systems.

“…Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering. DOI : 10.1177/09544070221127330 [2]. Torregrosa, A. J., Piqueras, P., Sanchis, E.,J., Redondo, Á.…”

“…3.6, the inlet and outlet sections are both eccentrical, of irregular shape and connected to open volumes before and after the monoliths, respectively. This device was classified into the "intermediate geometry" group and assessed exhaustively as a knowledge gap was identified about the changes occurring during the first few load-regeneration cycles; this analysis is presented in Chapter 6 and in the related paper [2]. This device was designed for gasoline engines to meet Euro 6b emission standard and it has two FT TWC monoliths, whose characteristics are presented in Table 3.4.…”

“…Part of the results and analysis presented in this chapter, particularly in the section The very early life of GPF can also be found in the paper A study of the early life of Gasoline Particulate Filters: Reactive and dissipative acoustic effects [2], which is a JCR publication derived from this part of the research. Also the discussion on reactive and dissipative effects derived from the application of decomposition analysis might share points with those presented in the other thesis-related publications enumerated in the Publications section.…”