*Article* **On the Impact of Particulate Matter Distribution on Pressure Drop of Wall-Flow Particulate Filters**

### **Vicente Bermúdez, José Ramón Serrano, Pedro Piqueras \* and Enrique José Sanchis**

CMT-Motores Térmicos, Universitat Politècnica de València, Camino de Vera s/n, Valencia 46022, Spain; bermudez@mot.upv.es (V.B.); jrserran@mot.upv.es (J.R.S.); ensanpac@mot.upv.es (E.J.S.)

**\*** Correspondence: pedpicab@mot.upv.es; Tel.: +34-96-387-7650

Academic Editor: Antonio Ficarella

Received: 26 January 2017; Accepted: 24 February 2017; Published: 2 March 2017

**Abstract:** Wall-flow particulate filters are a required exhaust aftertreatment system to abate particulate matter emissions and meet current and incoming regulations applying worldwide to new generations of diesel and gasoline internal combustion engines. Despite the high filtration efficiency covering the whole range of emitted particle sizes, the porous substrate constitutes a flow restriction especially relevant as particulate matter, both soot and ash, is collected. The dependence of the resulting pressure drop, and hence the fuel consumption penalty, on the particulate matter distribution along the inlet channels is discussed in this paper taking as reference experimental data obtained in water injection tests before the particulate filter. This technique is demonstrated to reduce the particulate filter pressure drop without negative effects on filtration performance. In order to justify these experimental data, the characteristics of the particulate layer are diagnosed applying modeling techniques. Different soot mass distributions along the inlet channels are analyzed combined with porosity change to assess the new properties after water injection. Their influence on the subsequent soot loading process and regeneration is assessed. The results evidence the main mechanisms of the water injection at the filter inlet to reduce pressure drop and boost the interest for control strategies able to force the re-entrainment of most of the particulate matter towards the inlet channels' end.

**Keywords:** internal combustion engines; emissions; particulate matter; wall-flow particulate filter; pressure drop; soot distribution; particulate layer
