Vehicle exhaust emissions consist of atmospheric air debris, carbon dioxide (CO), water vapor and numerous compounds in particulate or gaseous form, most of which are the result of incomplete fuel combustion. Distribution studies have revealed that motor vehicle emissions contribute to inhalable particles in the air. Governments have implemented requirements for permissible exhaust emission standards due to the adverse effects of diesel emissions on health and the environment. A thermal reactor with hot air injection can reduce CO and HC emissions significantly.
None of these major diesel emissions (with the exception of CO2) have adverse effects on health or the environment. Organizations and agencies are working to prevent damage to the environment and human health caused by greenhouse gases and pollutant emissions. CO and HC are emitted due to incomplete combustion and unburned fuel, while NOx emissions are due to high combustion temperatures above 1,600°C. Automakers must comply with a series of European emission standards that set maximum limits for harmful substances emitted by new cars.
Research has shown that hydrocarbon emissions in diesel and biodiesel exhausts can be speciated. Studies have also found a correlation between vehicle-induced concentrations of specific gases in the cabs and several test parameters, including the state of the windows, the type of cabin configuration, and the presence of exhaust leaks and openings in the lower part of the cabin. In large cities in developed countries, motor vehicle emissions represent 48-63% of total emissions from all available sources. Animals exposed to different dilutions of diesel engine exhaust for six months to two years showed an increase in hemoglobin adduct levels (2-hydroxyethylvaline and 2-hydroxypropylvaline).
A relatively small part of the flue gas is undesirable, harmful or toxic substances, such as carbon monoxide (CO) from incomplete combustion, hydrocarbons (CxHy), unburned fuel, oxides of nitrogen (NOx) from excessive combustion temperatures and particulate matter (mainly soot). SCR catalyst systems use urea as a NOx reductant, which can lead to ammonia emissions as well as a number of products of incomplete urea decomposition. Nitroarenes, as well as other oxygenated PAH species, are highly dependent on source conditions. Therefore, it is important to understand the major exhaust emissions from an engine in order to reduce their impact on health and the environment.