Combining the Classical and Lumped Diesel Particulate Filter Models

The growing presence of Spark Ignition Direct Injection (SIDI) engines along with the prevalence of direct injected Compression Ignition (CI) engines results in the requirement of Particulate Matter (PM) exhaust abatement. This occurs through the implementation of Gasoline Particulate Filters (GPFs) and Diesel Particulate Filters (DPFs). Modeling of GPFs and DPFs are analogous because of the similar flow patterns and wall flow PM capture methodology. Conventional modeling techniques include a two-channel (inlet/outlet) formulation that is applicable up to three-dimensions. However, the numerical stiffness that results from the need to couple the solution of these channels in compressible flow can result in relatively long run times. Previously, the author presented a lumped DPF model using dynamically incompressible flow intended for an Engine Control Unit (ECU) in order to generate a model that runs faster than real time using a high-level programming language. Building on the favorable outcomes of temperature evolution from this prior effort, this work enhances the model to predict compressible flow gas dynamics in order to match the evolution of pressure drop. Another enhancement is the inclusion of deep bed filtration within the wall, and the transition to the cake layer. Results show comparable temperature profiles with the dynamically incompressible model with a pressure drop that follows appropriately by linking through the ideal gas model. However, solving chemical species as an independent equation separate from compressible flow still deviates significantly from the classical two-channel approach

The effect of working fluid properties on the performance of a miniature free piston expander for waste heat harvesting

International audiencePower generation from waste heat sources at the miniature length scales may be generated by using phase change working fluids (liquid-to-vapor) in a traditional boiler-expander-condenser-pump system. This paper builds on our prior work of boiler and expander design by investigating the effects of working fluid properties on an expander unit based on a Free Piston (FPE) architecture. Here, using first principles, a lumped-parameter model of the FPE is derived by idealizing the FPE as a linear spring-mass-damper system. Moreover, a linear-generator model is incorporated to study the effects on useful power output from the FPE directly. As a result, insight into the thermodynamic processes within the FPE are detailed and general recommendations for working fluid selection are established. They include: (1) to achieve a higher FPE efficiency, it is desirable for a working fluid to have high specific heat ratio, and (2) a peak output voltage of about 20 V AC and peak output power of around 2 W can be generated by coupling a centimeter-scale electromagnetic energy converter to the FPE. Overall, this effort shows the promise of reliable miniature thermal power generation from low temperature waste heat sources

Catalyzed diesel particulate filter modeling

This is the published version.An increasing environmental concern for diesel particulate emissions has led to the development of efficient and robust diesel particulate filters (DPF). Although the main function of a DPF is to filter solid particles, the beneficial effects of applying catalytic coatings in the filter walls have been recognized. The catalyzed DPF technology is a unique type of chemical reactor in which a multitude of physicochemical processes simultaneously take place, thus complicating the tasks of design and optimization. To this end, modeling has contributed considerably in reducing the development effort by offering a better understanding of the underlying phenomena and reducing the excessive experimental efforts associated with experimental testing. A comprehensive review of the evolution and the most recent developments in DPF modeling, covering phenomena such as transport, fluid mechanics, filtration, catalysis, and thermal stresses, is presented in this article. A thorough presentation on the mathematical model formulation is given based on literature references and the differences between modeling approaches are discussed. Selected examples of model application and validation versus the experimental data are presented

Adaptive Global Carbon Monoxide Kinetic Mechanism over Platinum/Alumina Catalysts

Carbon monoxide (CO) oxidation is one of the more widely researched mechanisms given its pertinence across many industrial platforms. Because of this, ample information exists as to the detailed reaction steps in its mechanism. While detailed kinetic mechanisms are more accurate and can be written as a function of catalytic material on the surface, global mechanisms are more widely used because of their computational efficiency advantage. This paper merges the theory behind detailed kinetics into a global kinetic model for the singular CO oxidation reaction while formulating expressions that adapt to catalyst properties on the surface such as dispersion and precious metal loading. Results illustrate that the model is able to predict the light-off and extinction temperatures during a hysteresis experiment as a function of different inlet CO concentrations and precious metal dispersion

Production of the cylinder head and crankcase of a small internal combustion engine using metal laser powder bed fusion

This effort investigates the use of metal additive manufacturing, specifically laser powder bed fusion (LPBF) for the automotive and defense industries by demonstrating its feasibility to produce working internal combustion (IC) engine components. Through reverse engineering, model modifications, parameter selection, build layout optimization, and support structure design, the production of a titanium crankcase and aluminum cylinder head for a small IC engine was made possible. Computed tomography (CT) scans were subsequently used to quantify whether defects such as cracks, geometric deviations, and porosity were present or critical. Once viability of the parts was established, machining and other post-possessing were completed to create functional parts. Final X-ray CT and micro-CT results showed all critical features fell within ±0.127 mm of the original equipment manufacturer (OEM) parts. This allowed reassembly of the engine without any issues hindering later successful operation. Furthermore, the LPBF parts had significantly reduced porosity percentages, potentially making them more robust than their cast counterparts

Curves in the space: a virtual laboratory

[EN] The theory of curves in the plane and in the space is a fundamental part in the formation in geometry of afuture engineer, architect, physicist or mathematician. We present here an interactive virtual laboratory developed to visualize the most important properties of curves: Frenet trihedron, curvature, torsion, etc. with the aim of students acquiring and strengthening their knowledge on the subject more quickly[ES] La teoría de las curvas en el plano y en el espacio forma parte fundamental en la formación en geometría de un futuro ingeniero, arquitecto, físico o matemático. En este trabajo presentamos un laboratorio virtual interactivo dedicado a la visualización de las propiedades más importantes de las curvas: el triedro de Frenet, la curvatura, la torsión, etc. con la idea de que los alumnos puedan adquirir y afianzar más rápidamente sus conocimientos sobre el tema.Giménez Palomares, F.; Monsoriu Serrá, JA. (2016). Curvas en el espacio: un laboratorio virtual. Modelling in Science Education and Learning. 9(1):87-96. doi:10.4995/msel.2016.4523SWORD879691Benitez, J. (2008) Curvas rectificables. Valencia: Universitat Politècnica de València, . [Consulta: 10 de mayo de 2015]Cordero L. A., Fernández M., Gray A. (1995). Geometría diferencial de curvas y superficies. Addison-Wesley IberoamericanaDepcik C., Assanis D.N. (2005). "Graphical user interfaces in an engineer in educational environment". Comput. Appl. Eng. Educ. Vol. 13. GIEMATIC UC (2012) [Consulta: 10 de mayo de 2015]Lastra A. (2015) Geometría de curvas y superficies con aplicaciones en arquitectura. Ed. Paraninfo.MATHWORKS, (2015) MATLAB® Creating Graphical User Interfaces. The MathWorks, Inc.Puente M. J. (2007) Curvas algebraicas y planas. Servicio Publicaciones Universidad de CadizRoman J. de B. (2013) Curvas planas y en el espacio. García Maroto Editores.Zoido R. J. (2008) "Curvas y superficies en la arquitectura". Segundo Congreso Internacional de Ma-temáticas en la Ingeniería y la Arquitectura

Influence of Fuel Injection System and Engine-Timing Adjustments on Regulated Emissions from Four Biodiesel Fuels

The use of biofuels for transportation has grown substantially in the past decade in response to federal mandates and increased concern about the use of petroleum fuels. As biofuels become more common, it is imperative to assess their influence on mobile source emissions of regulated and hazardous pollutants. This assessment cannot be done without first obtaining a basic understanding of how biofuels affect the relationship between fuel properties, engine design, and combustion conditions. Combustion studies were conducted on biodiesel fuels from four feedstocks (palm oil, soybean oil, canola oil, and coconut oil) with two injection systems, mechanical and electronic. For the electronic system, fuel injection timing was adjusted to compensate for physical changes caused by different fuels. The emissions of nitrogen oxides (NOx) and partial combustion products were compared across both engine injection systems. The analysis showed differences in NOx emissions based on hydrocarbon chain length and degree of fuel unsaturation, with little to no NOx increase compared with ultra-low sulfur diesel fuel for most conditions. Adjusting the fuel injection timing provided some improvement in biodiesel emissions for NOx and particulate matter, particularly at lower engine loads. The results indicated that the introduction of biodiesel and biodiesel blends could have widely dissimilar effects in different types of vehicle fleets, depending on typical engine design, age, and the feedstock used for biofuel production

Heat transfer modeling in exhaust systems of high-performance two-stroke engines

Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-stroke engines is underestimated using steady state with fully developed flow empirical correlations. This fact is detected when comparing measured and modeled pressure pulses in different positions in the exhaust system. This can be explained taking into account that classical expressions have been validated for fully developed flows, a situation that is far from the flow behavior in reciprocating internal combustion engines. Several researches have solved this phenomenon in four-stroke engines, suggesting that the unsteady flow is strongly linked to the heat transfer. This research evaluates the correlations proposed by other authors in four stroke engines and introduces a new heat transfer model for exhaust systems in two-stroke, high performance, gasoline engines. The model, which accounts for both the entrance length effect and flow velocity fluctuations, is validated against experimental measurements. Comparisons of the proposed model with other models are performed, showing not negligible differences in the scavenge process related parameters.Lujan Martinez, JM.; Climent Puchades, H.; Olmeda González, PC.; Jimenez Macedo, VD. (2014). Heat transfer modeling in exhaust systems of high-performance two-stroke engines. Applied Thermal Engineering. 69(1-2):96-104. doi:10.1016/j.applthermaleng.2014.04.045S96104691-

On the impact of DPF downsizing and cellular geometry on filtration efficiency in pre- and post-turbine placement

[EN] the current work a computational study to evaluate the effect of the DPF downsizing on filtration efficiency is performed. The DPF is conventionally placed downstream of the turbine. However, its placement upstream of the turbine is growing in interest because of the benefits in specific fuel consumption, passive regeneration and aptitude to downsizing. Hence both pre- and post-turbine placement are considered in presence of clean and soot loaded substrates. An in-house 1D wall-flow DPF model for unsteady compressible flow is used. Volume reduction is approached considering diameter and length variation. In parallel, the cell density is also varied modifying the meso-geometry, i.e. cell size and porous wall thickness, imposing constant thermal integrity factor. The sensitivity to this last parameter is also analysed resulting its influence of second order in comparison to volume and cellular geometry effects. The lower Peclet number in the pre-turbine placement leads to higher filtration efficiency than post-turbine location comparing at the same DPF volume. Diameter based volume reduction provides slightly better results in filtration efficiency than length based reduction because of the way the filtration velocity field is varied. This general behaviour involves additional advantages to the potential for volume reduction of pre-turbine DPFs. Thus, different strategies with boundaries defined by volume reduction at constant filtration area or at constant specific filtration area can be approached looking for the best balance between fuel economy reduction and filtration efficiency increase provided by pre-turbine DPF placement.This work has been partially funded by FEDER and Government of Spain through Project No. TRA2016-79185-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, J.; Bermúdez, V.; Piqueras, P.; Angiolini, E. (2017). On the impact of DPF downsizing and cellular geometry on filtration efficiency in pre- and post-turbine placement. Journal of Aerosol Science. 113:20-35. https://doi.org/10.1016/j.jaerosci.2017.07.014S203511