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In the past decade automotive industries have focused on the development of new technologies to improve the overall engine efficiency and lower emissions in order to satisfy the always more stringent emission standards introduced all around the world. Technical progress has primarily focused on two aspects; the optimization of the air-fuel mixture in the combustion chamber as well as the combustion process itself, leading to simultaneous improvements in both, efficiency (lowering fuel consumption for same power output) and emissions levels which ultimately result from the optimized combustion process. Although engine technology has made significant progress, even modern Diesel combustion engines do not exceed a maximum efficiency of approximately 40%. Hence, around 60% of the available energy carried by the fuel and entering the combustion chamber is dissipated as heat to the environment. The next steps in engine optimization will see the integration of waste heat recovery systems (WHRS) to increase the overall energy efficiency of the propulsion system by means of recovering parts of the waste heat generated during normal engine operation. The presented was aimed at analyzing the availability as well as the quality of heat to be used in WHRS for the case of heavy-duty Diesel (HDD) engines employed in Class-8 tractors, which are suitable candidates for optimization via WHRS implementation as their engines spend most of their time operating at quasi steady state conditions, such as highway cruise. Three different primary energy sources have been considered: exhaust gas recirculation (EGR) cooling system, engine cooling system and exhaust gas stream. Experimental data has been gathered at West Virginia University’s Engine and Emissions Research Laboratory (EERL) facility in order to quantify individual heat flows in a model year (MY) 2004 Mack® MP7-355E HDD engine operated over the 13 modes of the European Stationary Cycle (ESC). Analysis based on second law efficiency underlined that not the whole amount of waste heat can be successfully used for recovery purposes and that heat sources which offer a large amount of waste energy reveal to be inappropriate for recovery purposes in case of low operating temperature. Time integral analysis revealed that engine modes which appear to offer high recovery potential in terms of waste power may not be suitable engine operating conditions when the analysis is performed in terms of waste energy, depending on the particular engine cycle. Finally a simple thermodynamic model of a micro power unit running on an Organic Rankine Cycle (ORC) has been used to assess the theoretical improvement in engine efficiency during steady state operations based on a second law efficiency analysis approach.Copyright © 2012 by ASME

Diesel particulate filters (DPFs) are well assessed aftertreatment devices, equipping almost every modern diesel engine on the market to comply with today’s stringent emission standards. However, an accurate estimation of soot loading, which is instrumental to ensuring optimal performance of the whole engine-after-treatment assembly, is still a major challenge. In fact, several highly coupled physical-chemical phenomena occur at the same time, and a vast number of engine and exhaust dependent parameters make this task even more daunting. This challenge may be solved with models characterized by different degrees of detail (0-D to 3-D) depending on the specific application. However, the use of real-time, but accurate enough models, may be the primary hurdle that has to be overcome when confronted with advanced exhaust emissions control challenges, such as the integration of the DPF with the engine or other critical aftertreatment components (selective catalytic reduction or other NOx control components), or to properly develop model-based OBD sensors. This paper aims at addressing real time DPF modeling issues with special regard to key parameter settings, by using the 1-D code called ExhAUST (exhaust aftertreatment unified simulation tool), which was jointly developed by the University of Rome Tor Vergata and West Virginia University. ExhAUST is characterized by a novel and unique full analytical treatment of the wall that allows a highly detailed representation of the soot loading evolution inside the DPF porous matrix. Numerical results are compared with experimental data gathered at West Virginia University engine laboratory using a MY2004 Mack®MP7-355E, an 11 liter, 6-cylinder, inline heavy-duty diesel engine coupled to a Johnson Matthey CCRT diesel oxidation catalyst + CDPF, catalyzed DPF exhaust aftertreatment system. To that aim, the engine test bench was equipped with a DPF weighing system to track soot loading over a specifically developed engine operating procedure. Results indicate that the model is accurate enough to capture soot loading and back pressure histories with regard to different steady state engine operating points, without a need for any tuning procedure of the key parameters. Thus, the use of ExhAUST for application to advanced after-treatment control appears to be a promising tool at this stage.

Despite their overwhelming popularity and widespread use, diesel engines have to strive to meet the continually tightening emission regulations. One of the most effective methods to control diesel particulate matter (PM) emissions from heavy duty diesel engines is to use wall flow Diesel Particulate Filters (DPFs). It is still a major challenge to get an accurate estimation of soot loading, which is crucial for the engine aftertreatment assembly optimization. In the recent past, several advanced computational models of DPF filtration and regeneration have been presented to assess the cost effective optimization of future particulate trap systems. In this study, the already presented 1D code [1,2] was extended to understand the impact of 2D representation to predict the transient behavior of a catalyzed Diesel Particulate Filter (CDPF). Quasi-steady state conservation of mass and momentum was solved to find the flow velocity and a previously validated, advanced filtration/regeneration model allowed a highly detailed representation of the soot loading, permeability, porosity and filtration efficiency. Results are presented in terms of comparison with the 1D code, over FTP engine transient cycle data gathered at the West Virginia University Engine and Emissions Research Laboratory (WVU-EERL), by keeping constant parameter set, for the sake of general validation of simplifying assumptions of the 1D code. Results generally state that the ID representation is effective toward PM loading prediction, although presenting considerable axial effects at higher DPF temperature.Copyright © 2011 by ASME