Since its birth, in the late 19th century, the thermal engine has contributed to drive Society towards a continuous development, which finally led everybody to live in the so called Global Village. In this new modern World, the keyword is mobility. Mobility for money, for goods, for people. Nowadays of course, not all these things actually move by car but we all have a new mindset, for which everything is on hand and everywhere is right behind the corner. Worldwide, according to the economic development of each country, more and more families are getting a slice of this freedom, as example by affording a new car, so that we can now count, on the planet, about one billion vehicles running every day, and this is just about the private fleet. But this last kind of freedom comes at a price. All these vehicles work burning fossil fuels and so producing emissions, made of a large variety of polluting substances, plus CO2. This is now affecting cities, human health and global climate to such a level that governments of the World started imposing compelling limitations to these emissions. Consequently, Automotive OEMs began to develop their cars from a new point of view: nowadays a car, in order to catch customers, has to ensure the same freedom as always while also being greener. From the engineering point of view, this has been the starting point from where the development of new internal combustion engines (I.C.E.) and vehicles in general began to be a business not just for automotive engineers, but also for new ranges of professionals, such as IT, Electric, Materials Science and Chemical engineers. The development of a greener car is now so complex that it became a sort of multidisciplinary job, now more than ever. At the beginning, the different approaches were barely connected to each other but, as the complexity was increasing, the need of much dialogue arose. The challenge for the Automotive Industry of today is to provide technologies that still grant freedom of mobility for everyone but making its products environmentally sustainable. About this subject, the most interesting proposals are gradually swapping the fleet towards electric-like vehicles but current technologies about batteries and fuel cells are not fully developed and ready for this revolution as they need more time for their wide spreading on the market, which appears indeed to be pushed far in the future. In the meanwhile, a prompt solution to the quest for a sustainable mobility can be found in the development of greener thermal engines (beside the change of the traditional mobility paradigm, topic of this research). From the chemical engineer’s point of view, these new greener I.C.E. offer several challenges, such as the development of better after-treatment systems, new solid and liquid lubricants tailored on non-ferrous surfaces and cleaner and more sustainable fuels. These three macro-subjects, coupled with new thermomechanical designs and better IT technologies integration, are crucial to make an engine greener, also offering the opportunity to be applied as retrofit, enhancing the speed of their spreading. One of the first successful approaches to cost and emissions reduction, maybe the one which really found its way in most transport applications (from motorsport to motorbikes), has been the so-called downsizing. Smaller but more efficient engines units can squeeze more power off a single drop of fuel than their predecessors, with consequent reduction of fuel consumption and emissions. Turbocharging, variable valve timings, lighter alloys are technologies examples but above all friction reduction allowed this outstanding result. Light alloys in particular, can be sources of high gain and high pain at the same time. To let light alloys work as engine components, they must be protected by proper coatings in those zones which are more severe for friction and wear, and this may cause some issues to lubricants. Lubricants in fact, have been developed for decades with a chemistry based on ferrous surfaces: are these recipes still effective on non-ferrous, coated surfaces? A study of the effects of a modern lubricant’s recipe on bare steel and DLC coated steel is presented in this work, with interesting outcomes and some suggestions about how to achieve an effective, universal lubricant for automotive applications without using Sulphur and Phosphorous based compounds, considered to be responsible of catalysts poisoning and, consequently, of emissions increasing. Since particulate matter emissions now concern also gasoline engines, the abatement of this pollutant is more than ever a trend topic in catalysis research environments. For the particular solid/solid reaction between the catalyst and the soot particle is proven to be highly dependent from the contact, a study of new morphologies and their effects on catalysts reactivity is presented in this thesis. Three different morphologies of ceria-based catalysts have been compared: amorphous nitrate-decomposition ceria to structured ceria nanofibers, self-assembled ceria microstars and ceria nanocubes. The investigations on materials characterization and particular soot oxidation tests will show if and how the morphology plays a relevant role in solid/solid catalytic reactions. Finally, since efficiency and cleanliness of engines cannot be treated only considering external agents like lubricants, coatings or exhaust after-treatment, but it is above all a matter of better design, the role of the so-called Virtual Engines has become more and more relevant throughout years, for their speed, cheapness and reliability, compared to traditional test benches, nowadays relegated to a mere validation role. The rush for the zero-emission vehicle sets on the table the old chimaera of automotive engineers: the HCCI engine. This particular engine has high efficiency and produces neither PM nor NOx but, however, for its development, it cannot be simulated trustfully with virtual tools (because of the complexity of that kind of combustion) nor tested on real benches (because of the dangerousness of that kind of combustion). In partnership with a virtual engine developer, a better description of the combustion characteristics of gasoline and ethanol-blended gasoline surrogates has been developed, as far as flame speed and ignition point is concerned, and the results are presented in this work. These three topics are individual subjects, all of them worthy of consideration from a chemical engineering point of view, but nevertheless they are linked to each other. Since exhaust aftertreatment is considered to be an essential device of modern vehicles, it does deserve to be improved more and more, but its catalysts suffer very much of S and P poisoning originated by lubricants (and fuels), which now need to be tailored on non-ferrous surfaces - brought in by downsizing approach - and, however, aimed towards ultra-low friction performances without using S and P based compounds. Finally, the comprehension of combustion by developing better gasoline surrogates for simulation tools it’s not just helpful for the achievement of the aforementioned HCCI engine, but also opens research opportunities towards alternative, cleaner and sustainable fuels in a faster and cheaper way. Three little steps towards the zero-emission vehicle.
A multifunctional approach to the reduction of I.C.E. emissions / Miceli, Paolo. - (2018 Mar 26).
|Titolo:||A multifunctional approach to the reduction of I.C.E. emissions|
|Data di pubblicazione:||26-mar-2018|
|Appare nelle tipologie:||8.1 Doctoral thesis Polito|