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MASTER EN AUTOMOCIÓN ESCUELA DE INGENIERÍAS INDUSTRIALES TRABAJO FIN DE MÁSTER Evolution of mixture formation, combustion and exhaust gas treatment systems in gasoline engines according to the EURO standards

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MASTER EN AUTOMOCIÓN ESCUELA DE INGENIERÍAS INDUSTRIALES TRABAJO FIN DE MÁSTER Evolution of mixture formation, combustion and exhaust gas treatment systems in gasoline engines according to the EURO standards EU3, EU4 and EU5 Evolución de sistemas de formación de mezcla, combustión y tratamiento de gases en motores de gasolina de acuerdo a las normas EU3, EU4 y EU5 Autor: D. José David Conejero Roselló Tutor: D. Francisco V. Tinaut Fluixá Valladolid, Septiembre de 2015 Escuela Ingenierías Industriales Depto. Ingª Energética y Fluidomecánica Paseo del Cauce s/n Valladolid (España) Fundación Cidaut Parque Tecnológico de Boecillo, Boecillo (Valladolid) España Evolution of mixture formation, combustion and exhaust gas treatment systems in gasoline engines according to the EURO standards EU3, EU4 and EU5 ABSTRACT European emissions regulations for light-duty vehicles have developed over many years, with consequent continuous development of engine and emissions control technologies to meet the legislative requirements. The development of spark ignition internal combustion engines technologies to overcoming the standards restrictions has had to be accomplished in parallel with its improvement to prevent neglecting performance and efficiency. As standards become more strict, systems become more complex and must work together to get the required result. After treatment systems require an accurate control on mixture formation and combustion to be feasible their functionality; mixture formation requires a precise fuel injection system; and all these set of elements working together, couldn't exist without the electronic control. Then these systems and techniques that were developed for the fulfillment of standards EU3 to EU5 be described. Gasoline ICE evolution according to EU standards EU3 to EU5 I Evolución de sistemas de formación de mezcla, combustión y tratamiento de gases en motores de gasolina de acuerdo a las normas EU3, EU4 y EU5 RESUMEN La normativa europea de emisiones para los vehículos ligeros se ha desarrollado desde hace décadas, con el continuo desarrollo consecuente de las tecnologías en los motores y de control de emisiones para cumplir con los requisitos legales. El desarrollo de los motores de combustión por chispa de para superar las restricciones normativas ha tenido que llevarse a cabo en paralelo con su mejora para evitar dejar de lado el rendimiento y la eficiencia. Los países de la Unión Europea (y también los que conforman el Espacio Económico Europeo) siguen los llamados European emission standards (Normas Europeas de Emisiones), en las que se regulan los límites de emisiones. A lo largo de los años se han actualizado éstas normas por medio de direcitvas. Este trabajo se centra en los límites de emisiones impuestos a los motores de gasolina, por las directivas Euro 3, Euro 4 y Euro 5; y qué tecnologías han sido necesarias introducir por los fabricantes para poder superarlas. Euro 1 (1993) Para vehículos de pasajeros 91/441/EEC (93/59/EEC) Euro 2 (1996) Para vehículos de pasajeros cars 94/12/EC (96/69/EC) Euro 3 (2000) Para cualquier vehículo 98/69/EC. Para motocicletas 2002/51/EC (row B) 2006/120/EC Euro 4 (2005) Para cualquier vehículo 98/69/EC (2002/80/EC) Tabla I.I- Directivas de emisiones Europeas. Euro 5 (2008/9) Para vehículos de pasajeros ligeros y vehículos comerciales 715/2007/EC Euro 6 (2014) Para vehículos de pasajeros ligeros y vehículos comerciales 715/2007/EC En la figura I, se puede apreciar la drástica reducción aplicada por la norma a lo largo de los años. Figure I.I Reducción de emisiones debidas a las normas Euro para vehículos de gasolina. Gasoline ICE evolution according to EU standards EU3 to EU5 II Como normas se vuelven más estrictas, los sistemas se vuelven más complejos y deben trabajar en paralelo para obtener el resultado requerido y no dejar de lado el rendimiento para cumplir con la norma. El desarrollo tecnológico en motores de combustión interna de gasolina tiene tres vías diferenciadas: Sistemas de formación de la mezcla. Sistemas de combustión. Sistemas de post-tratamiento de gases de escape. En la tabla I.II se aprecian las normas Euro y los sistemas introducidos en cada uno de sus periodos de aplicación para poder superarla. Euro 3 Euro 4 Euro 5 (2000) (2005) (2008/9) PFI PFI PFI Wall-guided DIG Homogenous DIG Homogeneous DIG Closed loop Closed loop (O2 or WR) Spray stratified DIG Electronic EGR Hybrids Alt fuels (CNG, ethanol) Port deactivation ETC Hybrids Closed coupled cat 80 mj Ignition Closed loop (O2 or WR) VVT (hydraulic) ETC Close coupled cat Mixture motion VVT (hydraulic) Boosting VVL (discrete) 80mJ ignition (multi-strike) Closed coupled cat NOx Trap Tabla I.II Incremento del contenido tecnológico de acuerdo a la introducción de las normas Euro. Inyección multipunto: Se deja atrás as los complejos y menos eficientes carburadores para optar por sistemas de inyección que permiten la dosificación precisa de combustible para el correcto funcionamiento de los sistemas de post-tratamiento de gases de escape. Closed loop (lazo cerrado): Es necesaria la interconexión mediante sensores de los sistemas de alimentación y post-tratamiento de gases mediante sensores y controlados por la Unidad de Control Electrónico. Desactivación de puerto: En motores multivávulas, para evitar que el descenso de la velocidad de entrada de aire a bajo régimen de motor, incida en la formación de la mezcla, se cierra total o parcialmente parte de la admisión para generar aumento de velocidad, mayor turbulencia y mejora de la mezcla aire combustible. Control electrónico del acelerador: Este Sistema determina el flujo de aire apropiado y consecuentemente el correcto ángulo de mariposa para entregar el par demandad por el conductor, y el consiguiente ahorro de combustible Gasoline ICE evolution according to EU standards EU3 to EU5 III Modos de combustión con carga homogénea y con carga estratificada: Se ha visto que los modos de combustión con carga estratificada en gasolina, son adecuados para zonas de baja carga, y que reducen significativamente el consumo de combustible y por ende, de CO2.. Los modos de carga homogénea son menos eficientes a baja carga pero mayores a alta. Algunos fabricantes como Mitsubishi, han desarrollado sistemas mixtos para aprovechar los beneficios de ambos modos. VVT (sistema de sincronización variable de válvulas): permite incrementar el par y la potencia, haciendo el motor más eficiente. El overlap (cruce de las válvulas), es el tiempo que permanecen abiertas las válvulas de admisión y escape al mismo tiempo. Menor overlap produce una menor velocidad idle (ralentí) y mayor par a baja velocidad, pero un desempeño pobre a alta velocidad porque no se tiene el suficiente aire para una buena combustión. Mayor overlap genera un buen rendimiento a altas velocidades pero bajo rendimiento a bajas velocidades, produciendo altas emisiones contaminantes. Los motores, en los que no cambia el overlap, están diseñados para lograr la mayor eficiencia a una velocidad (80 95 Km/hr), sin embargo por debajo o por arriba de esta velocidad pierden eficiencia. Dado lo anterior, si se cambia el tiempo de apertura de alguna de las válvulas para que el overlap sea pequeño a bajas velocidades y grande a altas velocidades, se tendrá un motor más eficiente a baja y a alta velocidad. Los motores VVT cambian el overlap haciendo que el motor sea entre un 10% y un 20% más eficiente. Catalizador: Para aquellas emisiones que no son posible reducir en la cámara de combustión, se hace necesario el uso de un sistema que intervenga antes de la expulsión de gases en el ambiente. Los catalizadores, son elementos capaces de acelerar las reacciones químicas de oxidación y reducción de los elementos nocivos en lo gases de escape. Son elemento complejos en cuanto a su construcción, caros por sus componentes, pero hoy en día imprescindibles para el cumplimiento de la norma. Todos estos nuevos sistemas introducidos, cada cual más complejo, necesitan la interconexión entre ellos para poder funcionar de manera adecuada. La adición de sensores y elementos electrónicos ha sido paralela a la de estos sistemas, y además los elementos de control imprescindibles para su funcionamiento. Gasoline ICE evolution according to EU standards EU3 to EU5 IV ACKNOWLEDGEMENTS La finalización de este Trabajo Final de Máster supone el cierre de una dura etapa de cambio y renovación. Llega el momento de echar la vista atrás y agradecer a todas las personas que me mostraron su apoyo y ayuda para cumplir este objetivo. En primer lugar, a mi tutor Francisco Tinaut, porque aun con la distancia, siempre mostraba su apoyo aunque fuera a través de una llamada o un simple correo. Y por supuesto, alentarme a cumplir con los plazos. A mis padres, por estar siempre ahí, dispuestos a cualquier cosa. Y en general a toda mi familia. Gracias a vosotros, parece no estar tan lejos de casa. A mi amigo Gilberto Geraldo, por compartir sus conocimientos, explicaciones y experiencia en el mundo de los motores de gasolina. A Gigi, por creer en mí y haberme dado soporte todos estos años. Gasoline ICE evolution according to EU standards EU3 to EU5 V NOTATIONS AND ACRONYMS ICE Internal Combustion Engine TDCO Overlap at TDC SUV Sub Urban Vehicle ITDC Ignition at TDC EPA Enviromental Protection Agency BDC Bottom Dead Center PM Particulate Matter IT Ignition Point THC Total Hydrocarbon Excess Air Ratio NMHC Non-Methane Hydrocarbon rfq Relative fuel quantity NOx Nitrogen oxides rac Relative air charge CO Carbon monoxide EGR Exhaust Gas Recirculation DI Direct Injection DIG Direct Injection Gasoline DISC Direct Injection Stratified Charge PN Particle Number ETC Electronic Throttle Control NEDC New European Driving Cycle PCV Positive Crankcase Ventilation MNEDC Modified New European Driving Cycle TBI Throttle Body Injection PFI Port Fuel Injection MPI Multi-Point Fuel Injection UDC Urban Driving Cycle A/F Air Fuel Ratio SI Spark Ignition ECU Electronic Control Unit I Intake Valve ETB Electronic Throttle Body IO Intake Valve Opens ESP Electronic Stability Program IC Intake Valve Closes ABS Anti-lock Braking System E Exhaust Valve CVT Continuously Varying Transmission EO Exhaust Valve Opens HEV Hybrid Electric Vehicle EC Exhaust Valve Closes VVT Variable Valve Timing TDC Top Dead Centre EMS Engine Management System OBD On Board Diagnostics SOHC Single Overhead Camshaft Gasoline ICE evolution according to EU standards EU3 to EU5 VI Contents 1 FOREWORD General context Purpose LITERATURE REVIEW Emission standards European standards Gasoline internal combustion engine. Spark ignition Method of operation Valve timing Air/fuel ratio Induction-mixture distribution in the combustion chamber Ignition and flame propagation Cylinder charge REGULATION INCREASING TECHNOLOGY CONTENT (EU3 to EU5) Multi-point fuel injection Direct injection gasoline Homogenous Direct Injection Gasoline Direct Injection Stratified Charge (DISC) Mixed-mode Direct Injection Gasoline Fuel control (closed loop) Electronic Exhaust Gas Recirculation (EGR) Electronic Throttle Control (ETC) Port deactivation Variable Valve Timing (VVT) Discrete VVT Hydraulic VVT Boosting Closed coupled catalyzer NOx Trap BMW M43/N42/N45 ENGINE EVOLUTION PSA XU ENGINE EVOLUTION Conclusion References Gasoline ICE evolution according to EU standards EU3 to EU5 VII Gasoline ICE evolution according to EU standards EU3 to EU5 VIII 1 FOREWORD 1.1 General context Due to its impact on human health and the nature surrounding us, engine emissions have been significantly reduced over the last decades. This reduction has been enforced by the legislating organs around the world that gradually have made the manufacturers transform their engines to today s complex high Tech products. The strategy of progressively tighter standards and regulations for emissions from conventional motor vehicles has worked well in terms of reduced vehicle emissions of local and regional air pollutants. Over the last years, tighter standards have led to progressive improvements in vehicle technology. Improved engine technologies and fuels have contributed to significant reductions in emissions of local air pollutants from new vehicles. Gasoline vehicles sold in Europe from 2000 onwards (and thus meeting Euro 3 standards) emit around 90% less CO, NOx and HC than vehicles sold in the 1980s, and emissions from new diesel vehicles have also been reduced significantly. This has contributed to reductions in local pollutants as newer vehicles with lower emissions have replaced older, more polluting vehicles. In most OECD countries, fleet emissions of NOx, CO and HC were at their highest levels in the early 1990s. Since then, they have dropped significantly (by 20-50%), despite a continuous increase in vehicle-kilometres travelled (+25% between 1990 and 2000). The overall result illustrates that technological improvements have made a significant contribution to improvements in local air quality in most OECD countries over this period. [1] The vehicle emission standards have been tightened further since then. After the programmed introduction of these new standards (and equivalent standards adopted in other countries), all new conventional gasoline and diesel vehicles that meet these tighter standards will be extremely low emitters (and therefore near clean ) in terms of local air pollutants. The expected availability of conventional motor vehicles with such low emissions of local pollutants is an important development that significantly improves the prospects for widespread use of low-emission vehicles in future. Conventional gasoline vehicles meeting Euro 4 and/or Tier 2 standards can be readily regarded as lowemission vehicles in an air pollution sense. With respect to diesel vehicles, this may also be the case, depending on whether they are supplied to the market with advanced after-treatment systems (diesel engines may be able to meet Euro 4 standards without particulate filter traps or de-nox devices). With the application of exhaust after-treatment and filter traps, light-duty diesel vehicles could perform as well as gasoline vehicles even in terms of NOx and PM emissions and will therefore also be properly considered low-emission vehicles. [2] As the programmed tightening in standards takes effect and older technology vehicles in current fleets are replaced with conventional vehicles with the best current technology, the improvements in per-vehicle emissions of local pollutants will continue and levels of local pollutant emissions from motor vehicle fleets will continue to fall. Until year 2008 (EU5), the gasoline technology content has focused on emissions driven, while from that year has shifted to efficiency driven, that is to say, reduce fuel consumption and CO2. This is because the number of CO2 targets required before 2008 by the standard. On figure 1 are shown the EU fleet averages evolution. Gasoline ICE evolution according to EU standards EU3 to EU5 1 Figure 1.1 EU fleet averages 1.2 Purpose By this TFM is intended to show the chronological evolution of gasoline internal combustion engines (ICE), including subsystems, forced to be cleaner by the changes imposed for European standards, from EU3 to EU5. All this throughout the perspective of manufacturers (Bosch, Delphy, BMW, Mitsubishi, Toyota, ). During this period and nowadays, engine s research and development has moved to get these standards targets and not only performance. All the systems and strategies used to aim the EU levels will be exposed and slightly explained to give the reader a global perspective of the changes introduced in gasoline ICE. Gasoline ICE evolution according to EU standards EU3 to EU5 2 2 LITERATURE REVIEW 2.1 Emission standards Emission standards are legal requirements governing air pollutants released into the atmosphere. These standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over specific timeframes. They are generally designed to achieve air quality standards and to protect human health. Focusing on regulating pollutants released by automobiles (motor cars), a vehicle emission performance standard is a limit that sets thresholds above which a different type of emission control technology might be needed. While emission performance standards have been used to dictate limits for conventional pollutants such as oxides of nitrogen and oxides of sulphur (NOx and SOx), this regulatory technique may be used to regulate greenhouse gasses, particularly carbon dioxide (CO2). In the US, this is given in pounds of carbon dioxide per megawatt-hour (lbs. CO2/MWhr), and kilograms CO2/MWhr elsewhere. The emissions legislation includes not only specific emissions limits, but also specific driving cycles and test procedures. Laws on emissions are introduced successively in stages and the limits are continuously decreasing. There are three main bodies of legislation in the world shown in the next map: European, called Euro 1 to 6, United States, called Tier I or II, Japanese legislation. Those regulations and standards are respectively compulsory in European countries (in fact not only European Union countries, but all countries belonging to the European Economic Space), United States of America and Japan. For other countries in the world, each country may have adopted one of those three regulations, at least as a reference and in most cases with a time delay on the enforcement dates. In the figure, the countries following the European legislation are in different darkness of blue. The countries following the US legislation are in different darkness of brown. The Japan-based legislation is currently followed by Japan and is represented here in green. Not all the countries are at the same limits but the goal is the same: to force the transport sector to produce cleaner vehicles. [3] Gasoline ICE evolution according to EU standards EU3 to EU5 3 Figure 1.2 Regulation distribution by country around the world. In the United States, emissions standards are managed by the Environmental Protection Agency (EPA). The State of California has special vehicle emissions standards, and other states may choose to follow either the national or California standards. Federal (National) Tier 1 regulations went into effect starting in 1994, and Tier 2 standards are being phased in from 2004 to Automobiles and light trucks (SUVs, pickup trucks, and minivans) are treated differently under certain standards. The EPA has separate regulations for small engines, such as grounds-keeping equipment. The states must also promulgate miscellaneous emissions regulations in order to comply with the National Ambient Air Quality Standards. European emission standards define the acceptable limits for exhaust emissions of new vehicles sold in EU member states. The emission standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards. Starting June 10, 1968, the Japanese Government passed the Japanese: Air Pollution Control Act which regulated all sources of air pollutants. As a result of the 1968 law, dispute resolutions were passed under the 1970 Japanese: Air Pollution Dispute Resolution Act. As a result of the 1970 law, in 1973 the first release of four sets of new emissions standards was introduced. Interim standards were introduced on January 1, 1975 and again for The final set of standards were introduced for [10] While the standards were introduced they were not made immediately mandatory, instead tax breaks were offered for cars which passed them. [11] The standards were based on those adopted by the original US Clean Air Act of 1970, but the test cycle included more slow city driving to correctly reflect the Japanese situation. [12] The 1978 lim
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