Experimental and analytical study of the mechanical friction losses in the piston-cylinder liner tribological pair in internal combustion engines (ICE)

[ES] Con el aumento de la demanda de soluciones más amigables con el medio ambiente en la industria de la automoción, el motor de combustión interna alternativo (MCIA) enfrenta actualmente grandes desafíos para minimizar su consumo de recursos no renovables y especialmente, para reducir sus emisiones contaminantes. Debido a que el aporte de los MCIAs es fundamental para cubrir las necesidades de movilidad y de generación de energía alrededor de todo el mundo, y el hecho de que diferentes alternativas, como los motores eléctricos e hibrido, están y continuaran enfrentado múltiples obstáculos para su implementación masiva en el futuro cercano, la investigación continua en MCIA es fundamental para cumplir con los propósitos de reducción de emisiones. En este aspecto, una aproximación para el aumento de la eficiencia del motor y la reducción del consumo de combustible es mediante la implementación de alternativas dirigidas a reducir las pérdidas mecánicas por fricción. Estas alternativas tribológicas incluyen aquellas que requieren modificaciones en los componentes del motor, como materiales y acabados superficiales, y el uso de formulaciones de aceite lubricante de menor viscosidad o aditivos que mejoren las condiciones de lubricación del motor. Con la contante evolución y mejoras en el MCIA y las condiciones de trabajo cada vez más severas, también surgen nuevas alternativas tribológicas para enfrentar los nuevos desafíos del motor, y por tanto se requiere de investigaciones adicionales en este tema. Durante el desarrollo de esta Tesis, uno de los objetivos consistió en contribuir a la investigación del uso de aceites de baja viscosidad para el ahorro de combustible como un efecto conjunto con las condiciones de conducción del vehículo. Para llevar a cabo este objetivo, se desarrollaron ensayos experimentales bajo condiciones estacionarias en un banco de motor con formulaciones de aceite de diferente viscosidad HTHS, algunas de ellos con aditivo modificador de fricción para expandir el rango de reducción de fricción a condiciones de lubricación más severas. Los mapas de consumo de combustible resultantes de estos ensayos fueron utilizados en un modelo de simulación del vehículo para estimar su consumo de combustible como función del aceite y las condiciones de trabajo de tres ciclos de conducción. Con el objetivo de expandir los conocimientos en los fundamentos de lubricación de los MCIAs y tener la capacidad de evaluar otras alternativas para reducir las pérdidas por fricción, se consideró necesario enfocar la investigación en el conjunto pistón-camisa, que es el par tribológico con mayor aporte a las perdidas por fricción. Para conseguir este objetivo, durante esta Tesis se desarrolló una maqueta específica para el ensamble pistón-camisa, y un modelo teórico para simular la lubricación del segmento de compresión. Para la primera parte, la maqueta se desarrolló basada en el método de camisa flotante, en el cual la camisa fue aislada del resto del motor y la fuerza de fricción generada en la interfaz pistón-camisa pudo ser medida mediante sensores de fuerza. En esta instalación se desarrollaron diferentes ensayos los cuales permitieron llevar a cabo un análisis exhaustivo de los fundamentos de lubricación de este par tribológico como función de diferentes parámetros que tiene impacto en las condiciones de lubricación. Este estudio se complementó con el desarrollo de un modelo de lubricación para el segmento de compresión basado en el método de diferencias finitas. Finalmente, se llevó a cabo una comparativa de resultados experimentales y teóricos para el segmento de compresión, lo cual permitió validar los ensayos experimentales en la maqueta de camisa flotante, así como el modelo de simulación desde el punto de vista de datos de entrada, condiciones de contorno y supuestos.[CA] Amb l'augment de la demanda de solucions més amigables amb el medi ambient en la indústria de l'automoció, el motor de combustió interna alternatiu (MCIA) s'enfronta actualment a grans desafiaments per minimitzar el seu consum de recursos no renovables i especialment, per reduir les seves emissions contaminants . Tenint en compte que l'aportació dels MCIA és fonamental per a cobrir les necessitats de mobilitat i generació d'energia arreu de tot el món, i el fet que diferents alternatives, com els motors elèctrics i híbrids, estan i continuaran enfrontat múltiples obstacles per a la seva implementació massiva al proper futur, la investigació contínua en MCIA és fonamental per complir amb els propòsits de reducció d'emissions. En aquest aspecte, una aproximació per a l'augment de l'eficiència del motor i la reducció de consum de combustible és mitjançant la implementació d'alternatives dirigides a reduir les pèrdues mecàniques per fricció. Aquestes alternatives tribològiques inclouen aquelles que requereixen modificacions de components del motor, com materials i acabats superficials, i l'ús de formulacions d'oli lubricant de menor viscositat o additius que milloren les condicions de lubricació del motor. Amb la constant evolució i millores en el MCIA i les condicions de treball cada vegada més severes, també sorgeixen noves alternatives tribològiques per enfrontar els nous desafiaments del motor, i per tant es requereix d'investigacions addicionals en aquest tema. Durant el desenvolupament d'aquesta Tesi, un dels objectius va consistir a contribuir a la investigació de l'ús d'olis de baixa viscositat per a l'estalvi de combustible com un efecte conjunt amb les condicions de conducció de vehicle. Per dur a terme aquest objectiu, es van desenvolupar assajos experimentals sota condicions estacionàries en un banc de motor amb formulacions d'oli de diferent viscositat HTHS, algunes d'elles amb additiu modificador de fricció per expandir el rang de reducció de fricció a condicions de lubricació més severes . Els mapes de consum de combustible resultants d'aquests assajos van ser utilitzats en un model de simulació del vehicle per estimar el seu consum de combustible com a funció de l'oli i les condicions de treball de tres cicles de conducció. Amb l'objectiu d'expandir els coneixements en els fonaments de lubricació dels MCIAs i tenir la capacitat d'avaluar altres alternatives per reduir les pèrdues per fricció, es va considerar necessari enfocar la recerca al conjunt pistó-camisa, que és el parell tribològic amb major aportació a les perdudes per fricció. Per aconseguir aquest objectiu, durant aquesta Tesi es va desenvolupar una maqueta específica per al acoblament pistó-camisa, i un model teòric per simular la lubricació del segment de compressió. Per a la primera part, la maqueta es va desenvolupar basada en el mètode de camisa flotant, en el qual la camisa va ser aïllada de la resta del motor i la força de fricció generada en la interfície pistó-camisa va poder ser mesurada mitjançant sensors de força. En aquesta instal·lació es van desenvolupar diferents assajos els quals van permetre dur a terme una anàlisi exhaustiva dels fonaments de lubricació d'aquest parell tribològic com a funció de diferents paràmetres que tenen impacte en les condicions de lubricació. Aquest estudi es va complementar amb el desenvolupament d'un model de lubricació per al segment de compressió basat en el mètode de diferències finites. Finalment, es va dur a terme una comparativa de resultats experimentals i teòrics per al segment de compressió, la qual cosa va permetre validar els assajos experimentals a la maqueta de camisa flotant, així com el model de simulació des del punt de vista de dades d'entrada, condicions de contorn i hipòtesis.[EN] With the increasing demand for greener solutions in the automotive industry, the ICE is currently facing great challenges to minimize the consumption of nonrenewable resources and specially to reduce its harmful emissions. Given that the contribution of the ICE is fundamental to cover the actual mobility and power generation needs worldwide, and the fact that different power-train alternatives, such as electric and hybrid vehicles, are and will continue facing multiple obstacles for their large-scale implementation in the near future, the continuous research on the ICE is fundamental in order to meet the emissions reduction targets. In this regard, one approach to increase the engine efficiency and reduce the fuel consumption, is through the implementation of alternatives aimed to reduce the friction mechanical losses. These tribological alternatives include those that require modifications to the engine components, such as materials and surface finishes, and the use of lubricant oil formulation of lower viscosity or additives that improve the lubrication performance of the engine. With the ongoing evolution and improvement of the ICE and the increasingly severe working conditions, new tribological solutions also emerge to face the new challenges in the ICE, and therefore further research is required on this subject. During the development of this Thesis, one of the objectives was to contribute to the research on low viscosity engine oils for fuel economy as a joint effect with the driving conditions of the vehicle. To accomplish this, experimental tests were performed under stationary conditions in an engine bench test for oil formulations of different HTHS viscosity, some of them with friction modifier additive to expand the friction reduction effect to more severe lubrication conditions. The resultant fuel consumption maps were then employed in a vehicle model to estimate the fuel consumption of the vehicle as function of the oil formulation and the working conditions of the three driving cycles. With the aim of expanding the knowledge on the lubrication fundamentals of the engine and to have the capability to assess other alternatives to further reduce the friction mechanical losses, it was deemed necessary to focus the research on the piston-cylinder liner assembly, the tribo-pair of major friction share. In order to achieve this objective, a test rig was developed in this Thesis specific for the piston-liner assembly, and a theoretical model to estimate the lubrication of the piston compression ring. For the first part, the test rig was designed based on the floating liner method, where the cylinder liner was isolated from the rest of the engine and the friction force generated in the piston-liner conjunction could be measured by means of force sensors. Different tests were developed in this test rig which allowed a comprehensive analysis of the piston lubrication fundamentals as function of different parameters having an impact on the lubrication performance of this assembly. This study was complemented with the development of a piston compression ring lubrication model based on the finite differences method. A comparison of experimental and theoretical results was performed for the piston compression ring that helped to validate both the experimental tests in the floating liner and the simulation model from the point of view of input data, boundary conditions and assumptions.Bastidas Moncayo, KS. (2021). Experimental and analytical study of the mechanical friction losses in the piston-cylinder liner tribological pair in internal combustion engines (ICE) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172188TESI

Simulation of Border Deformation in Corrosion System by Coupling Analytical Solution and Finite Element Method

The objective of this work is to develop a digital model in order to envisage metal degradation on a microscopic scale. The reaction on the surface of the anodic considered as a degradation reaction when the surface forming the cathode remains unchanged. A one dimensional analytical solution representing the two mediums (anode and cathode), is introduced in the form of boundary conditions of Neumann type to the interface metal/electrolyte and thus the resolution was performed without mesh the analytical zone. Also, no re-meshing solving domain was need when simulating the border deformation.

Simulation of Border Deformation in Corrosion System by Coupling Analytical Solution and Finite Element Method

The objective of this work is to develop a digital model in order to envisage metal degradation on a microscopic scale. The reaction on the surface of the anodic considered as a degradation reaction when the surface forming the cathode remains unchanged. A one dimensional analytical solution representing the two mediums (anode and cathode), is introduced in the form of boundary conditions of Neumann type to the interface metal/electrolyte and thus the resolution was performed without mesh the analytical zone. Also, no re-meshing solving domain was need when simulating the border deformation.

Improved fleet operation and maintenance through the use of low viscosity engine oils: fuel economy and oil performance

[EN] For heavy-duty vehicles and road transportation, fuel consumption and associated CO2 emissions have been of great concern, which has led to the development and implementation of technologies to reduce their impact on the environment. Low viscosity engine oils have arisen as one proven cost-effective solution to increase the engine efficiency; however, for the heavy-duty vehide segment, engine protection against wear is a priority for end-users, and therefore there is some reluctance to the use of that new oil formulations. In this study, eight lubricant oils, representative of the HTHS viscosity reduction that heavy-duty oils have been undergoing and new API CK-4 and FA-4 categories, were evaluated for fuel economy, oil performance and engine wear, in a long-term test involving a fleet of 49 heavy-duty vehicles of four different engine technologies, some of them with diesel fuel and others with compressed natural gas. Results of fuel economy were positive for most of the buses' models. Regarding oil performance and wear, most of the formulations were found to be suitable for extended oil drain intervals (ODI); and although no alarming results were found, overall performance of the formulations of the fourth stage could lead to significant wear if the oil drain interval is extended. In this study, it should be noted that some of the information has been presented by the authors in other publications, here they are presented with the purpose of complementing the new results and summarize the entire test.Author Sophia Bastidas would like to thank the support of the program Ayudas de Investigacion y Desarrollo (PAID-01-17) of the Universitat Politecnica de Valencia.Macian Martinez, V.; Tormos, B.; Bastidas-Moncayo, KS.; Pérez, T. (2020). Improved fleet operation and maintenance through the use of low viscosity engine oils: fuel economy and oil performance. Eksploatacja i Niezawodnosc - Maintenance and Reliability. 22(2):201-211. https://doi.org/10.17531/ein.2020.2.3S20121122

Fuel economy optimization from the interaction between engine oil and driving conditions

[EN] Low viscosity engine oils have shown to be an effective solution to the fuel consumption reduction target, however, their potential is closely linked to the vehicle and engine design and to the real driving conditions. In this study the interaction between engine oil and driving conditions of two urban routes and one rural route in Spain and the United Kingdom has been put to test with the aim to evaluate their joint effect over fuel economy of a freight transport vehicle. In a first approximation, six different oil formulations, three of them belonging to the new API CK-4 and FA-4 categories and two with molybdenum-based friction modifier, were tested under stationary conditions with a medium-duty diesel engine. Followed by tests under real driving conditions of a freight transport vehicle, developed by means of computer simulations with an adjusted vehicle model, taking the fuel consumption maps of the six oil formulations, vehicle characteristics and the selected driving cycles as inputs to the model. Results of engine bench tests and simulations with oils of lower HTHS viscosity showed fuel consumption reduction values as expected. However unexpected results were found between the oils with molybdenum-based friction modifier added to their formulation.The authors would like to thank to the Spanish Ministerio de Economia y Competitividad for supporting the EFICOIL project (TRA2015-70785-R) and to the program Ayudas de Investigacion y Desarrollo (PAID-01-17) of the Universitat Politecnica de Valencia.Tormos, B.; Pla Moreno, B.; Bastidas-Moncayo, KS.; Ramirez-Roa, LA.; Perez, T. (2019). Fuel economy optimization from the interaction between engine oil and driving conditions. Tribology International. 138:263-270. https://doi.org/10.1016/j.triboint.2019.05.042S263270138Edwards, M. R., Klemun, M. M., Kim, H. C., Wallington, T. J., Winkler, S. L., Tamor, M. A., & Trancik, J. E. (2017). Vehicle emissions of short-lived and long-lived climate forcers: trends and tradeoffs. Faraday Discussions, 200, 453-474. doi:10.1039/c7fd00063dDente, S. M. R., & Tavasszy, L. (2018). Policy oriented emission factors for road freight transport. Transportation Research Part D: Transport and Environment, 61, 33-41. doi:10.1016/j.trd.2017.03.021Hofer, C., Jäger, G., & Füllsack, M. (2018). Large scale simulation of CO2 emissions caused by urban car traffic: An agent-based network approach. Journal of Cleaner Production, 183, 1-10. doi:10.1016/j.jclepro.2018.02.113Lepitzki, J., & Axsen, J. (2018). The role of a low carbon fuel standard in achieving long-term GHG reduction targets. Energy Policy, 119, 423-440. doi:10.1016/j.enpol.2018.03.067Solaymani, S. (2019). 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Tribology International, 127, 420-432. doi:10.1016/j.triboint.2018.06.024Triantafyllopoulos, G., Kontses, A., Tsokolis, D., Ntziachristos, L., & Samaras, Z. (2017). Potential of energy efficiency technologies in reducing vehicle consumption under type approval and real world conditions. Energy, 140, 365-373. doi:10.1016/j.energy.2017.09.023Macián, V., Tormos, B., Bermúdez, V., & Ramírez, L. (2014). Assessment of the effect of low viscosity oils usage on a light duty diesel engine fuel consumption in stationary and transient conditions. Tribology International, 79, 132-139. doi:10.1016/j.triboint.2014.06.003Macián, V., Tormos, B., Ruíz, S., & Ramírez, L. (2015). Potential of low viscosity oils to reduce CO2 emissions and fuel consumption of urban buses fleets. Transportation Research Part D: Transport and Environment, 39, 76-88. doi:10.1016/j.trd.2015.06.006Souza de Carvalho, M. J., Rudolf Seidl, P., Pereira Belchior, C. R., & Ricardo Sodré, J. (2010). 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SAE International Journal of Fuels and Lubricants, 5(3), 1426-1435. doi:10.4271/2012-28-0010Tormos, B., Ramírez, L., Johansson, J., Björling, M., & Larsson, R. (2017). Fuel consumption and friction benefits of low viscosity engine oils for heavy duty applications. Tribology International, 110, 23-34. doi:10.1016/j.triboint.2017.02.007Van Dam, W., Miller, T., Parsons, G. M., & Takeuchi, Y. (2011). The Impact of Lubricant Viscosity and Additive Chemistry on Fuel Economy in Heavy Duty Diesel Engines. SAE International Journal of Fuels and Lubricants, 5(1), 459-469. doi:10.4271/2011-01-2124Skjoedt, M., Butts, R., Assanis, D. N., & Bohac, S. V. (2008). Effects of oil properties on spark-ignition gasoline engine friction. Tribology International, 41(6), 556-563. doi:10.1016/j.triboint.2007.12.001Rao, L., Zhang, Y., Kook, S., Kim, K. S., & Kweon, C.-B. (2019). Understanding in-cylinder soot reduction in the use of high pressure fuel injection in a small-bore diesel engine. 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Simulation of Border Deformation in Corrosion System by Coupling Analytical Solution and Finite Element Method

The objective of this work is to develop a digital model in order to envisage metal degradation on a microscopic scale. The reaction on the surface of the anodic considered as a degradation reaction when the surface forming the cathode remains unchanged. A one dimensional analytical solution representing the two mediums (anode and cathode), is introduced in the form of boundary conditions of Neumann type to the interface metal/electrolyte and thus the resolution was performed without mesh the analytical zone. Also, no re-meshing solving domain was need when simulating the border deformation

Petrology, mineralogy, and geochemistry of the olivine diogenite NWA 4255: new insights into the magmatic evolution of asteroid 4 Vesta

Northwest Africa (NWA) 4255 is a meteorite found in the region of Tindouf (southwestern Algeria), classified as brecciated olivine diogenite. Based on textural observations and orthopyroxene compositions, two different lithologies were determined: harzburgitic and orthopyroxenitic. The orthopyroxenitic lithology contains orthopyroxene (Mg no. 73.99–75.68) and spinel (Cr no. 83.09–85.11, Mg no. 15.57–22.45). On the other hand, the harzburgitic lithology contains orthopyroxene (Mg no. 74.54–77.14) and olivine (Mg no. 70.94–72.57). The iron metal and the sulfides (Troilites) of this sample are present in both lithologies and are low in Ni (Ni < 0.1 wt%). The Fe/Mn ratio of orthopyroxenes ranges from 22.28 to 32.64 and show a large overlap between both lithologies. Lowest ratios are unusual; they are below the defined field for diogenites and olivine diogenites. ∆17O values are − 0.234 ± 0.003 (1σ) and confirm that the NWA 4255 originated from 4Vesta. The results of this study show that there is a genetic linkage between the two lithologies of NWA 4255 and correspond to in situ crystallization processes. This olivine diogenite reflects transition between two major magmatic processes in 4Vesta. The magma ocean of 4Vesta crystallized at equilibrium, allowing the formation of a dunitic and harzburgitic mantle. This late lithology is linked to the peritectic reaction between the olivines formed and the evolved liquid. Our sample then reflects this crucial step of separating this mantle from the residual liquid. This melt evolving on the peritectic allowed the formation of the observed harzburgitic assemblage and then evolves out from the peritectic reaction to proceed to a fractional crystallization process involving the formation of orthopyroxenite

Roles of GM-CSF in the Pathogenesis of Autoimmune Diseases: An Update.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was first described as a growth factor that induces the differentiation and proliferation of myeloid progenitors in the bone marrow. GM-CSF also has an important cytokine effect in chronic inflammatory diseases by stimulating the activation and migration of myeloid cells to inflammation sites, promoting survival of target cells and stimulating the renewal of effector granulocytes and macrophages. Because of these pro-cellular effects, an imbalance in GM-CSF production/signaling may lead to harmful inflammatory conditions. In this context, GM-CSF has a pathogenic role in autoimmune diseases that are dependent on cellular immune responses such as multiple sclerosis (MS) and rheumatoid arthritis (RA). Conversely, a protective role has also been described in other autoimmune diseases where humoral responses are detrimental such as myasthenia gravis (MG), Hashimoto\u27s thyroiditis (HT), inflammatory bowel disease (IBD), and systemic lupus erythematosus (SLE). In this review, we aimed for a comprehensive analysis of literature data on the multiple roles of GM-CSF in autoimmue diseases and possible therapeutic strategies that target GM-CSF production

Hochuekkito, a Kampo (Traditional Japanese Herbal) Medicine, and its Polysaccharide Portion Stimulate G-CSF Secretion from Intestinal Epithelial Cells

Kampo (traditional Japanese herbal) medicines are taken orally due to which the gastric mucosal immune system may act as one of the major targets for the expression of pharmacological activity. The inner surface of the intestinal tract possesses a large area of mucosal membranes, and the intestinal epithelial cells sit at the interface between a lumen and a lymphocyte-rich lamina propria. The cross talk that occurs between these compartments serves to maintain intestinal homeostasis, and the cytokine network plays an important role in the cross talk. In this study, the effect of Hochuekkito (HET), one of Kampo medicines, on cytokine secretion of intestinal epithelial cells was investigated. When murine normal colonic epithelial cell-line MCE301 cells were stimulated with HET, the contents of granulocyte colony-stimulating factor (G-CSF) in the conditioned medium were significantly increased in dose- and time-dependent manners. The enhanced G-CSF gene transcription in MCE301 cells by the stimulation of HET was observed by RT-PCR. The enhanced G-CSF secretion by HET was also observed in C3H/HeJ mice-derived primary cultured colonic epithelial cells. When the HET was fractionated, only the polysaccharide fraction (F-5) enhanced the G-CSF secretion of MCE301 cells, and the activity of F-5 lost after the treatment of periodate that can degrade the carbohydrate moiety. These results suggest that HET enhances secretion of G-CSF from colonic epithelial cells and the polysaccharide is one of the active ingredients of HET. The enhanced G-CSF secretion by HET may partly contribute to the clinically observed various pharmacological activities of HET including immunomodulating activity