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Diesel and gasoline direct injection engines emit nucleation mode particles either under special conditions or as part of their normally emitted size distribution, respectively. Currently, European legislation excludes nucleation mode particles as particle number vehicle emission measurements are limited down to 23 nm. The rationale behind such a cut-off size is based on the avoidance of significant uncertainties inherent in the sampling and measuring of sub-23 nm solid particles. However, the sub-23 nm particles have drawn increased attention since a large fraction of particles emitted by modern vehicles lies in this size range. In this study we investigate the possibility of accurate nucleation mode particles detection by using the Advanced Half Mini Differential Mobility Analyzer (HM-DMA).

Evolving marine diesel emission regulations drive significant reductions of nitrogen oxide (NOx) emissions. There is, therefore, considerable interest to develop and validate Selective Catalytic Reduction (SCR) converters for marine diesel NOx emission control. Substrates in marine applications need to be robust to survive the high sulfur content of marine fuels and must offer cost and pressure drop benefits. In principle, extruded honeycomb substrates of higher cell density offer benefits on system volume and provide increased catalyst area (in direct trade-off with increased pressure drop). However higher cell densities may become more easily plugged by deposition of soot and/or sulfate particulates, on the inlet face of the monolithic converter, as well as on the channel walls and catalyst coating, eventually leading to unacceptable flow restriction or suppression of catalytic function.

Nowadays diesel particulate filters (DPFs) with catalyst coatings have assumed one of the most significant roles for road vehicle emission control. DPFs made of re-crystallized SiC (SiC-DPFs) have guaranteed the soot filtration efficiency for the current regulation. In order to further enhance their filtration efficiency, even though a higher porosity and larger pore size must be adopted for sufficient catalyst coating capacity, we developed the concept of a filtration layer on the DPF inlet channel walls and researched its performance both theoretically and experimentally. First of all, models of the new filtration layer, closely resembling the real one made in the laboratory, were digitally reconstructed and soot deposition simulations were conducted.

Trends towards lower vehicle fuel consumption and smaller environmental impact will increase the share of Diesel hybrids and Diesel Range Extended Vehicles (REV). Because of the Diesel engine presence and the ever tightening soot particle emissions, these vehicles will still require soot particle emissions control systems. Ceramic wall-flow monoliths are currently the key players in the Diesel Particulate Filter (DPF) market, offering certain advantages compared to other DPF technologies such as the metal based DPFs. The latter had, in the past, issues with respect to filtration efficiency, available filtration area and, sometimes, their manufacturing cost, the latter factor making them less attractive for most of the conventional Diesel engine powered vehicles. Nevertheless, metal substrate DPFs may find a better position in vehicles like Diesel hybrids and REVs in which high instant power consumption is readily offered enabling electrical filter regeneration.

Catalyzed Diesel Particulate Filters (CDPFs) continue to be an important emission control solution and are now also expanding to include additional functionalities such as gas species oxidation (such as CO, hydrocarbons and NO) and even storage phenomena (such as NOx and NH3 storage). Therefore an in depth understanding of the coupled transport - reaction phenomena occurring inside a CDPF wall can provide useful guidance for catalyst placement and improved accuracy over idealized effective medium 1-D and 0-D models for CDPF operation. In the present work a previously developed 3-D simulation framework for porous materials is applied to the case of NO-NO2 turnover in a granular silicon carbide CDPF. The detailed geometry of the CDPF wall is digitally reconstructed and micro-simulation methods are used to obtain detailed descriptions of the concentration and transport of the NO and NO2 species in the reacting environment of the soot cake and the catalyst coated pores of the CDPF wall.

In previous work an advanced micro-scale simulation framework for DPF materials has been presented. This development comes as DPF developers continue to seek competitive advantage at the material level and the availability of computing power is improving to the point that micro-scale simulation may be considered for routine application for DPF materials optimization. The aim of the present work is to show an in-depth application of advanced micro-scale simulation methods to silicon carbide DPF materials currently in widespread use. The quality and utility of these simulations, targeting filtration and soot oxidation phenomena in SiC DPF material, is evaluated and the potential for the use of such advanced simulation technology is assessed in a materials development context.

Diesel Particulate Filter (DPF) material design based on a traditional design of experiments approach can be very time consuming and costly, due to the high number of tests and prototype material samples required. This provides an opportunity for the application of simulation tools at the microscopic scale, which are recently seeing increasing use in DPF material studies. The current work describes a framework for such micro-scale simulations based on high fidelity digital representations of the porous materials of interest, on the rationale that the performance of the latter materials depends strongly on the coupling of different physicochemical phenomena occurring at the microscopic scale where material morphology is important.

This paper describes work supporting the development of a new Diesel particulate trap system for heavy duty vehicles based on porous sintered metal materials that exhibit interesting characteristics with respect to ash tolerance. Experimental data characterizing the material (permeability, soot and ash deposit properties) are obtained in a dedicated experimental setup in the side-stream of a modern Diesel engine as well as in an accelerated ash loading rig. System level simulations coupling the new media characteristics to 3-D CFD software for the optimization of complete filter systems are then performed and comparative assessment results of example designs are given.

DPF design, system integration, regeneration control strategy optimization and ash ageing assessment, based on a traditional design of experiments approach becomes very time consuming and costly, due to the high number of tests required. This provides a privileged window of opportunity for the application of simulation tools and hence simulation is increasingly being used for the design of exhaust after-treatment systems with a Diesel Particulate Filter (DPF). DPF behavior depends strongly on the coupling of physico-chemical phenomena occurring over widely disparate spatial and temporal scales and a state-of-the-art simulation approach recognizes and exploits these facts introducing certain assumptions and/or simplifications to derive an accurate but computationally tractable DPF simulation tool, for the needs of industrial users.

In the present work we apply a computational simulation framework developed for square-cell shaped honeycomb Diesel Particulate Filters to study the filtration, pressure drop and soot oxidation characteristics of recently developed triangular-cell-shaped, high porosity wall-flow filters. Emphasis is placed on the evaluation of the applicability and adaptation of the previously developed models to the case of triangular channels. To this end Computational Fluid Dynamics, asymptotic analysis, multichannel and “unit-cell” calculations are employed to analyze filter behavior and the results are shown to compare very well to experiments available in the literature.

In recent years advanced computational tools of Diesel Particulate Filter (DPF) regeneration have been developed to assist in the systematic and cost-effective optimization of next generation particulate trap systems. In the present study we employ an experimentally validated, state-of-the-art multichannel DPF simulator to study the regeneration process over the entire spatial domain of the filter. Particular attention is placed on identifying the effect of inlet cones and boundary conditions, filter can insulation and the dynamics of “hot spots” induced by localized external energy deposition. Comparison of the simulator output to experiment establishes its utility for describing the thermal history of the entire filter during regeneration. For effective regeneration it is recommended to maintain the filter can Nusselt number at less than 5.