Characterization of Particulate matter and the capture efficiency in open metal substrates

Poster (konferens), 2015

Introduction Emission of particulate matter (PM) constitutes a big threat to the climate as well as to human health. Therefore it is necessary to apply best available practice for all diesel vehicles as one means to reduce premature death [1]. Since the Diesel Particulate Filter (DPF) is viable way to reduce PM emissions the detailed understanding of the DPF is important to enable improved performance. This includes oxidation kinetics, PM transformations and the fluid dynamics for PM capture. In order to enable systematic studies of this complex process, an experimental setup (Exhaust After Treatment System, EATS) that can isolate individual phenomena has been developed [2]. The PM is prone to contain volatile hydrocarbons (HC) which will influence both the capture efficiency as well as the performance of the catalyst. In a previous study, we have shown how the HC contribution can be isolated from the solid fraction [3]. In this work we present how an open (inert) monolith placed upstream the filter can be used to remove the volatile part of the PM. By isolating the volatile part from the solid part in-situ, the hydrodynamic process of PM capture is better understood which is vital when dealing with these very complex systems. Materials and Methods The EATS was used to study the PM from a single cylinder Heavy Duty diesel engine and the Capture efficiency (CE) over a novel metal substrate [4]. The temperature and linear velocity was systematically varied in combination with the effect of the inert monolith placed upstream. The particle size distribution (PSD) was measured using a Fast Particle sizer (DMS500 from Cambustion) at different positions. Results and Discussion By applying the methodology developed earlier [3] the HC fraction of the PM could be determined. The difference between observed CE and theoretical CE is used to derive how much HC is needed to explain the capture efficiency over the inert monolith (for validation, see [5]). The PM exiting the inert monolith has no remaining volatiles [6] and the capture efficiency over the metal substrate in thus possible. From the Capture efficiencies in Figure 1, it can be seen that the CE over the inert monolith is influenced by HC content. The CE over the metal substrate is similar to previous studies on similar geometries [7]. Conclusions By applying an experimental methodology adapted for the highly transformative PM, the systematic study of CE over a novel metal substrate is enabled. These types of experiments are necessary to gain the understanding of the different processes in a DPF. By a detailed understanding improved performance and lowered emissions are possible.