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Reducing emissions
The combustion of fuel in a diesel engine takes economical due to the high density and excess air and - with reservations - environmentally friendly. The exhaust fumes contain only a small amount of carbon monoxide (CO) and nitrogen oxide (NOx). Even if compared with gasoline engines diesel engines can be evaluated as the best in terms of emissions of CO, HC and NOx, and there are drawbacks. For example, selection of carbon black (particle) and sulfur dioxide (SO2).
| Fig. 4.98. Schematic operation of the catalyst: 1 - ceramic honeycomb carrier; 2 - gauze; 3 - a casing of heat-resistant alloy steel; 4 - Net funnel
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On diesel engines, the E-Class is fitted as standard oxidation catalyst. The casing and the catalyst tubes are made of stainless steel. A coating of noble metals on the catalyst (fig. 4.98) activates additional oxidation exhaust gas, wherein hydrocarbons (HC) and carbon monoxide (CO) are converted into carbon dioxide (CO2) and water (H2O). Through this process, and reduces particulate emissions. Soot particles can not be deposited on the hydrocarbon compounds and are ejected.
Technical Dictionary Exhausts Carbon monoxide (CO). Measured under the control of the exhaust gases. The premise for the low levels of CO - precise adjustment of the amount and the time of injection, and even whirling stirring the mixture. Indoors poisonous air combines with oxygen of air to harmless carbon dioxide, which, however, may cause the greenhouse effect. Hydrocarbons (CH). Partially can not burn in the cooler areas and narrow angles of the combustion chamber. The proportion depends on the design of the engine (unchangeable size); too rich or too lean mixture increases their output. Together with nitrogen oxides to form smog. Nitrogen oxides (NOx). Their weight increases with increasing combustion temperature. They are distinguished, for example, on engines adjusted to a low content of CO and HC in exhaust gases (reduced fuel consumption). At high concentrations, causing a burning sensation in the airways. When interacting with water to form nitric acid (acid rain). Sulphur dioxide (SO2). In small quantities, is formed only for diesel engines. The reason - the content of sulfur in diesel fuel. In the light forms a sulfuric or sulfurous acid, both lead to acid rain. However, sulphurous acid from car emissions account for only 3% of all produced sulfurous acid. |
Improving parameters of exhaust gases when using e-diesel system (EDS) To lower nitrogen oxides, hydrocarbons and soot contained in the exhaust of diesel engines in addition to the oxidation catalytic converter equipped with exhaust gas recirculation (Fig. 4.98) and adjustable suction pressure. Exhaust gas recirculation (AGR)
| Fig. 4.99. Components EGR: 1 - intake air temperature sensor; 2 - the lever of pressure control valve; 3 - cell vacuum pressure control valve; 4 - cell vacuum exhaust system (ARF); 5 - control valve exhaust gas return systems; 6 - suction pipe of exhaust gases; 7 - an outlet; 8 - Front silencer
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At high temperatures of combustion in diesel engines dramatically increases the proportion of nitrogen oxides in the exhaust gases. The possibility of reducing the temperature in the combustion chamber - the supply of exhaust gases. Out of the total flow of the exhaust gas of the engine is given by using EGR (Fig. 4.99). Dose is determined depending on the engine load and is directed back to the air supply duct downstream of the valve control pressure. Since the exhaust gas contains almost no flammable substances, it can not be burned again. However, it restricts the supply of fresh air for combustion and thereby reduces the temperature in the combustion chamber and the proportion of nitrogen oxides. Along with an electronically controlled exhaust gas recirculation, contributing to reduction of nitrogen oxide emissions, CDI-engines are equipped with catalytic converters, as well as a second exhaust gas cleaner, located under the bottom.
PRACTICAL ADVICE When repairing the exhaust gazovnelzya good closure metal rusting. This measure - only for a short time. Fasteners and clips of rubber last longer than metal. On systems with two or more sections of the muffler after the replacement of one in a few months has to be replaced and others. Therefore, changing the service stations usually entire installation. However, it is not always necessary. Check the condition of the system and first decide whether you will change the section individually, or the entire system. |
1. Place the vehicle on a jack. 2. If it is impossible to dismantle, unscrew the bolts, then cut away or drill them. When mounting, use new screws and nuts. 3. For safety and replace the rubber clamps, gaskets and so on. 4. If there is already replaced with at least one part of the exhaust system, then detach the inserted pipe ends better when heated. To do this in the workshops used a welding torch. You can also use a propane burner. But be sure to keep a fire extinguisher. If these funds do not try to use a tool to remove the rust. 5. Joints sections disconnected strong rotating motion or by hammer blows. 6. If this fails, saw off the pipe at 10 cm from the junction with the evil section. Propylene residue sections in length and bring down using a chisel or a large screwdriver. 7. All bolting and nuts are spun next time easier if you during installation threads greased heat-resistant grease. It is desirable to make connections and junctions.
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