Abstract

By the end of the 20th century, humanity faced the problem of the need to protect itself. The action of a number of complex interrelated factors has led to a violation of the biological balance in our world, in the system man - nature. The rapid development of scientific and industrial civilization, the demographic explosion, the insufficient requirements for environmental protection that were imposed on the developing industry in the past, the gradual reduction of free, uncultivated and forest territories, as well as the unplanned development of urban areas contributed to the disappearance of some forms of flora and fauna. Faced with the threat of gradual extinction, man finally understood that in order to protect the biological balance in nature, it is necessary to start a general war for the purity of air, water and land. In the international arena, this problem is recognized as one of the important ones. The appearance of smog was first recorded in Los Angeles in the late 1940s. Its cause was excessive air pollution by industrial and transport emissions. In 1952, the phenomenon of smog was observed in London. It caused catastrophic consequences - about 4,000 people became its victims, who died due to an increase in the number of respiratory diseases under the influence of smog. The exhaust gases produced by the combustion of the air-fuel mixture in the internal combustion engine contain pollutants such as carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC) and particulate matter (PM), which are very harmful to humans and the environment. Nitrogen oxides, which are formed at high temperature and excess oxygen, are especially toxic. Both of these conditions are present in the process of fuel combustion in any engine, but especially a lot of them are formed in a diesel engine, since the air entering its cylinders is not throttled and there is always an excess of it. In addition, a high temperature occurs in the combustion chambers, and the higher it is, the more nitrogen oxides are formed. For these reasons, a diesel engine emits much more nitrogen oxides in the exhaust gases compared to a gasoline engine.

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