Experimental assessment of a pre-turbo aftertreatment configuration in a single stage turbocharged diesel engine. Part 2: Transient operation

This paper corresponds to the second part of a work devoted to analyse the impact of the pre-turbo aftertreatment configuration on the performance of a single stage turbocharged Diesel engine. This second part focuses on the analysis of the engine response under transient operating conditions. To address the causes and effects of the change in engine response several types of transient processes consisting of driving cycles and load transient tests have been evaluated as starting point of the analysis. These tests make possible to account for the influence of the aftertreatment thermal inertia and how it affects the engine and aftertreatment performance obtained during driving cycles and under highly demanding transient operation. The pre-turbo aftertreatment placement also provides advantages in terms of faster aftertreatment warm-up. Therefore, the benefits on DPF (diesel particulate filter) passive regeneration as well as DOC (diesel oxidation catalyst) light-off leading to lower gas emissions have been assessed. The results have been compared against baseline emissions measured during experiments with post-turbo aftertreatment placement. Finally the influence of the thermal inertia on driveability in sudden accelerations as a function of the wall temperature along the exhaust line and boosting architecture is assessed combining the analysis of experimental and modelled data.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness through Grant No. TRA2013-40853-R.Lujan Martinez, JM.; Serrano Cruz, JR.; Piqueras Cabrera, P.; García Afonso, Ó. (2015). Experimental assessment of a pre-turbo aftertreatment configuration in a single stage turbocharged diesel engine. Part 2: Transient operation. Energy. 80:614-627. https://doi.org/10.1016/j.energy.2014.12.017S6146278

Filtration modelling in wall-flow particulate filters of low soot penetration thickness

A filtration model for wall-flow particulate filters based on the theory of packed beds of spherical particles is presented to diagnose the combined response of filtration efficiency and pressure drop from a reliable computation of the flow field and the porous media properties. The model takes as main assumption the experimentally well-known low soot penetration thickness inside the porous wall. The analysis of soot loading processes in different particulate filters shows the ability of the proposed approach to predict the filtration efficiency as a function of the particle size distribution. Nevertheless, pressure drop and overall filtration efficiency are determined by the mode diameter of the raw particulate matter emission. The results reveal the dependence of the filtration efficiency in clean conditions on the sticking coefficient. However, the dynamics of the pressure drop and filtration efficiency as the soot loading varies is governed by the soot penetration thickness. This parameter is closely related to the porous wall Peclet number, which accounts for the porous wall and flow properties influence on the deposition process. The effect of the transition from deep bed to cake filtration regime on the pressure drop is also discussed underlying the importance of the macroscale over microscale phenomena.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness through Grant No. TRA2013-40853-R. Additionally, the Ph.D. student E. Angiolini has been funded by a grant from Conselleria de Educacio, Cultura i Esport of the Generalitat Valenciana with reference GRISOLIA/2013/036. These supports are gratefully acknowledged by the authors.Serrano Cruz, JR.; Climent, H.; Piqueras, P.; Angiolini, E. (2016). Filtration modelling in wall-flow particulate filters of low soot penetration thickness. Energy. 112:883-898. https://doi.org/10.1016/j.energy.2016.06.121S88389811

Packed bed of spherical particles approach for pressure drop prediction in wall-flow DPFs (diesel particulate filters) under soot loading conditions

The soot loading process in wall-flow DPFs (diesel particulate filters) affects the substrate structure depending on the filtration regime and produces the increase of pressure drop. Deep bed filtration regime produces the decrease of the porous wall permeability because of the soot particulates deposition inside it. Additionally, a layer of soot particulates grows on the porous wall surface when it becomes saturated. As soot loading increases, the pressure drop across the DPF depends on the porous wall and particulate layer permeabilities, which are in turn function of the substrate and soot properties. The need to consider the DPF pressure drop influence on engine performance analysis or DPF regeneration processes requires the use of low-computational effort models describing the structure of the soot deposition and its effect on permeability. This paper presents a model to describe the micro-scale of the porous wall and the particulate layer structure assuming them as packed beds of spherical particles. To assess the model s capability, it is applied to predict the DPF pressure drop under different experimental conditions in soot loading, mass flow and gas temperature.This work has been partially supported by the Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia through grant number SP20120340-UPPTE/2012/96 and by the Conselleria de Educacio, Cultura i Esport de la Generalitat Valenciana through grant number GV/2013/043.Serrano Cruz, JR.; Arnau Martínez, FJ.; Piqueras Cabrera, P.; García Afonso, Ó. (2013). Packed bed of spherical particles approach for pressure drop prediction in wall-flow DPFs (diesel particulate filters) under soot loading conditions. Energy. 58:644-654. https://doi.org/10.1016/j.energy.2013.05.051S6446545