Abstract:Wall-flow filters are a standard component in exhaust gas aftertreatment and have become indispensable in vehicles. Ash and soot particles generated during engine combustion are deposited in diesel or gasoline particulate filters. During regeneration, the soot particles are oxidized. The remaining ash particles can form different deposition patterns: a homogenous layer or plug-end filling. It has not yet been clarified whether the plug-end filling is first formed by rearrangements of agglomerates before and du… Show more
“…The specific experimental procedure relevant in the context of this work is described in § 5.4. A more detailed description of the experimental set-up and relevant parameters can be found in Thieringer et al (2022).…”
Section: Two-channel Set-upmentioning
confidence: 99%
“…A more detailed description of the experimental set-up and relevant parameters can be found in Thieringer et al. (2022). Figure 3.( a ) Sketch and ( b ) 3-D model of the stacked layer design used in the experimental set-up.…”
The exhaust from combustion engines contains particulate matter (PM), which poses potential health risks to human lungs. Current emission laws place increasingly strict limitations on both PM and particle number, leading to the necessity of using wall-flow filters to separate out a significant amount of the introduced PM. As this leads to an increase in the filter's loading, it is regenerated continuously or periodically, leading to the rearrangement of individual particulate structures inside the filter channels. Such rearrangement events cause the formation of specific deposition patterns, which affect the filter's pressure drop, its loading capacity and the separation efficiency. In order to derive predictions on the formation of specific deposition patterns, the transient behaviour of individual particle structures needs to be examined. The present work investigates the detachment and transport of particle structures during filter regeneration with three-dimensional surface-resolved simulations using a lattice Boltzmann method. The goal of this work is the determination of relevant key quantities and their interpretation with respect to predictions regarding the resulting deposition patterns. In this context, it is shown that lift forces are not the predominant detachment forces for non-spherical particle structures, and that the stopping distance of such structures is too long to avoid back-end deposition.
“…The specific experimental procedure relevant in the context of this work is described in § 5.4. A more detailed description of the experimental set-up and relevant parameters can be found in Thieringer et al (2022).…”
Section: Two-channel Set-upmentioning
confidence: 99%
“…A more detailed description of the experimental set-up and relevant parameters can be found in Thieringer et al. (2022). Figure 3.( a ) Sketch and ( b ) 3-D model of the stacked layer design used in the experimental set-up.…”
The exhaust from combustion engines contains particulate matter (PM), which poses potential health risks to human lungs. Current emission laws place increasingly strict limitations on both PM and particle number, leading to the necessity of using wall-flow filters to separate out a significant amount of the introduced PM. As this leads to an increase in the filter's loading, it is regenerated continuously or periodically, leading to the rearrangement of individual particulate structures inside the filter channels. Such rearrangement events cause the formation of specific deposition patterns, which affect the filter's pressure drop, its loading capacity and the separation efficiency. In order to derive predictions on the formation of specific deposition patterns, the transient behaviour of individual particle structures needs to be examined. The present work investigates the detachment and transport of particle structures during filter regeneration with three-dimensional surface-resolved simulations using a lattice Boltzmann method. The goal of this work is the determination of relevant key quantities and their interpretation with respect to predictions regarding the resulting deposition patterns. In this context, it is shown that lift forces are not the predominant detachment forces for non-spherical particle structures, and that the stopping distance of such structures is too long to avoid back-end deposition.
“…The approach was then used in a following work [10] for the investigation of the detachment, acceleration and deceleration of individual PM layer fragments, resulting from the fragmentation of a continuous PM deposition layer during the filter's regeneration. This work includes a pressure drop comparison with investigations conducted on an experiment rig described in Thieringer et al [15]. In the most recent work [11], a comprehensive quantification of the stability and accuracy of both particle-free and particle-including flow was provided for elevated inflow velocities of up to 60 m s −1 .…”
Section: Introductionmentioning
confidence: 99%
“…Contrary to previous works in which the simulations' stability, accuracy and validity was accessed with convergence studies, literature findings and experimental results, the present work does not attempt such evaluations, but rather focusses on the derivation of quantitative statements. The challenges inherent to experimental investigations of the transient processes of interest [15], which are the motivation behind the present study in the first place, impede a thorough validation of the simulation results at this point. Single-valued key quantities, such as the plug density, are, however, compared to literature findings.…”
Wall-flow filters are applied in the exhaust treatment of internal combustion engines for the removal of pm. Over time, the pressure drop inside those filters increases due to the continuously introduced solid material, which forms pm deposition layers on the filter substrate. This leads to the necessity of regenerating the filter. During such a regeneration process, fragments of the pm layers can potentially rearrange inside single filter channels. This may lead to the formation of specific deposition patterns, which affect a filter’s pressure drop, its loading capacity and the separation efficiency. The dynamic formation process can still not consistently be attributed to specific influence factors, and appropriate calculation models that enable a quantification of respective factors do not exist. In the present work, the dynamic rearrangement process during the regeneration of a wall-flow filter channel is investigated. As a direct sequel to the investigation of a static deposition layer in a previous work, the present one additionally investigates the dynamic behaviour following the detachment of individual layer fragments as well as the formation of channel plugs. The goal of this work is the extension of the resolved particle methodology used in the previous work via a discrete method to treat particle–particle and particle–wall interactions in order to evaluate the influence of the deposition layer topology, pm properties and operating conditions on dynamic rearrangement events. It can be shown that a simple mean density methodology represents a reproducible way of determining a channel plug’s extent and its average density, which agrees well with values reported in literature. The sensitivities of relevant influence factors are revealed and their impact on the rearrangement process is quantified. This work contributes to the formulation of predictions on the formation of specific deposition patterns, which impact engine performance, fuel consumption and service life of wall-flow filters.
Particulate filters are used as a standard component in the exhaust gas aftertreatment of vehicles. The reactive (soot) and inert (ash) particles generated during engine operation are deposited in wall-flow filter. The resulting particle layer increases the differential pressure of the filter, which is why it is regenerated regularly. During regeneration of the filter, the reactive particles oxidize, and the inert particles remain in the filter. The oxidation of the soot particles results in a layer break-up, and the resuspension of particle structures can occur. The layer break-up over the entire length of an inlet channel and the resuspension of particle structures have not yet been observed, which is why the fundamental processes in a particulate filter have not yet been fully clarified. In these investigations, the regeneration of a single wall-flow filter channel is observed in situ with high temporal and spatial resolution. For this purpose, the filter is loaded with soot particles and regenerated subsequently. The regeneration of the filter is analyzed in relation to the process parameters of temperature, layer thickness, and flow velocity. Before the visual layer break-up, the pressure drop decreases and declines to a constant value before resuspension of particle structures are detected. As the temperature is increased, the regeneration time is reduced. With a thicker particle layer, the particle structures formed during layer break-up become larger, the location of resuspension shifts to the posterior channel region, and the number of resuspensions increases. A higher flow velocity causes more particle structures to be resuspended and transported to the channel end.
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