CLIL CLIL CLIL LANGUAGE IMMERSION MECHANICS AND PROPULSION SYSTEMS DIESEL EMISSIONS Diesel exhaust gases are mainly made up of CO2 (carbon dioxide), H2O (water vapour) and some residual amount of engine charge air. The quantity of CO2 and H2O is directly proportional to the engine load while the amount of O2 is indirectly proportional. Their concentrations usually follow these ranges: CO2 from 2 to 12 %; H2O from 2 to 12 %; O2 from 3 to 17 %; N2 balance Apart from CO2 causing the greenhouse effect, these principal emissions are not harmful but Nitrogen are always accompanied by other dangerous pollutants released after imperfect processes have occurred during combustion. These noxious Oxygen exhaust gases contain carbon monoxide (CO), particulate matter (PM), nitrogen oxides (NOx) or unburned hydrocarbons (HC). Incomplete Water vapor combustion of fuel, chemical reactions between mixture components under high temperature and Pollutant Carbon dioxide pressure, and the combustion of non-hydrocarbon emissions components of diesel fuel such as sulphur compounds are the factors that most frequently result in these highly toxic emissions. Their concentrations can be lowered to near zero levels in advanced diesel engines equipped with emission after-treatment devices such as NOx reduction catalysts and particulate filters. Such after-treatment systems aim at transforming the pollutants produced by the engine into nonpolluting elements before they are released into the atmosphere. Carbon monoxide is emitted when air in the combustion chamber is not enough for complete fuel combustion: it can reduce the amount of oxygen carried around our body by the haemoglobin in our blood, causing serious breathing difficulties. Incomplete combustion also generates particulates consisting of a mix of elemental carbon particles, soluble organic carbon and other metallic compounds. DPM (Diesel Particulate Matter) may also contain some small amounts of nitrates, sulfates and sulphuric acid. DPM can contribute to smog, reduce visibility, affect local climate change and increase global warming. When inhaled, particulates can enter our blood causing cancer or respiratory diseases. Nitrogen oxides are also very irritating for our lungs and, along with sulphur dioxides, are at the origin of acid rain which harms wildlife and accelerates the decay of building materials in our cities. Other harmful emissions can be caused not only by additives introduced into the fuel or lube oil but also by low cost quality fuels, often containing heavy metals and other toxic compounds. GLOSSARY additive: additivo to affect: influenzare after-treatment device: dispositivo post-trattamento to breath: respirare 284 disease: malattia to inhale: inalare load: carico to lower: abbassare lube: lubrificante noxious: dannoso particulate: particolato, in particelle to release: rilasciare, fare uscire to result in: causare wildlife: animali e piante selvatiche