5.6.2. Decrease in toxicity of the fulfilled gases
Combustion of fuel in the diesel engine happens economically at the expense of the high density and excess of air and — with reservations — is eco-friendly. Exhaust gases contain only a small amount of carbon oxide (SO) and nitrogen oxide (NOx). Even if in comparison with petrol engines diesel engines can be estimated as the best allocations on indicators WITH, the NANOSECOND and NOx, is shortcomings. For example, release of soot (particle) and content of dioxide of sulfur (SO2).
Fig. 4.98. Schematical work of catalytic converter: 1 – ceramic carrier of cellular structure; 2 – metalfabric; 3 – a casing from the heat-resistant alloyed steel; 4 – mesh funnel
On diesel engines of the E-class oxidizing converter serially is established. The casing of the catalyst and a tube are made of the alloyed steel. The covering from precious metals on the catalyst (fig. 4.98) activates additional oxidation in exhaust gases, at the same time hydrocarbons (NANOSECONDS) and carbon oxide (SO) turn into carbon dioxide (CO2) and water (H2O). Thanks to this process also emission of solid substances decreases. Parts of soot cannot be besieged on hydrocarbonic connections and are removed outside.
The fulfilled gases
Carbon oxide (SO). It is measured at control of exhaust gases. A prerequisite for low contents WITH — exact adjustment of quantity and the moment of injection, and also uniform vortex hashing of mix. In the enclosed space it is poisonous, on air connects to air oxygen to harmless carbon dioxide which, however, can cause greenhouse effect.
Hydrocarbons (SN). Can partially not burn down in cold zones and narrow corners of the combustion chamber. Their share depends on an engine design (the unchangeable size); too rich or too poor mix increases their emission. Together with oxides of nitrogen form a smog.
Oxides of nitrogen (NOx). Their share increases at combustion temperature increase. They are allocated, for example, on the engines adjusted on low contents WITH and NANOSECOND in exhaust gases (the cut fuel consumption). At high concentration cause burning in airways. At interaction with water form nitric acid (acid rains).
Dioxide of sulfur (SO2). In small amounts it is formed only at diesel engines. The reason — the content in diesel fuel of sulfur. On light forms sulfuric or sulphurous acid, both lead to acid rains. However sulphurous acids from automobile exhausts make only 3% from all formed sulphurous acids.
Improvement of parameters of the fulfilled gases when using electronic diesel system (EDS)
That there are less oxides of nitrogen, hydrocarbons and soot contained in an exhaust, diesel engines in addition to oxidizing catalytic converter are equipped with system of recirculation of the fulfilled gases (fig. 4.98) and adjustment of pressure of absorption.
Recirculation of the fulfilled gases (AGR)
Fig. 4.99. Knots of system of recirculation of the fulfilled gases: 1 – the sensor of temperature of the soaked-up air; 2 – lever of the valve of adjustment of pressure; 3 – cell of depression of the valve of adjustment of pressure; 4 – cell of depression of the exhaust system (ARF); 5 – the adjusting valve of system of return of the fulfilled gases; 6 – the soaking-up pipeline of the fulfilled gases; 7 – final branch pipe; 8 – forward part of the muffler
At high temperatures of combustion of fuel at diesel engines the share of oxides of nitrogen in the fulfilled gases sharply increases. A possibility of decrease in temperature in the combustion chamber — a supply of the fulfilled gases. From the general stream of the fulfilled gases of the engine a part by means of system of recirculation of the fulfilled gases (fig. 4.99) is taken away. The dose is defined depending on loading of the engine and goes back to the pipeline of system of air supply behind the valve of management of pressure. As the fulfilled gas practically does not contain combustible substances, it cannot be burned once again. However it limits a supply of fresh air for combustion and, thus, promotes decrease in temperature in the combustion chamber and shares of oxides of nitrogen.
Along with the electronically controlled recirculation of the fulfilled gases promoting decrease in release of oxides of nitrogen, CDI engines are equipped with converters, and also the second cleaner of the fulfilled gases located under the bottom.
At repair of system of release fulfilled газовнельзя it is good to make the metal which underwent corrosion. This measure — only for a short time. Fastenings and collars from rubber keep longer, than metal. On systems with two and more sections of the muffler after replacement of one in several months it is necessary to replace also others. Therefore at car repair shops change, as a rule, completely all system. However it is not always obligatory. Check a condition of system and at first solve whether you will change sections separately or all system entirely.
SEQUENCE OF WORKS
1. Install the car on a jack.
2. If at dismantle it is impossible to turn off bolts, then cut off them or drill. At installation use new bolts and nuts.
3. For safety also replace rubber collars, laying and other.
4. If at least one detail of an exhaust system was already replaced, then it is better to disconnect the inserted ends of pipes when heating. For this purpose in workshops the welding torch is used. You can use a propane torch also. But surely have near at hand the fire extinguisher. If these means are absent, try to use means for removal of a rust.
5. Joints of sections are disconnected by strong rotary motions or by means of blows by the hammer.
6. If it does not help, saw off a pipe in 10 cm from a junction with unusable section. Saw through the rest of section on length and bring down by means of a chisel or the big screw-driver.
7. All bolt connections and nuts will be turned off next time easier if you at installation grease a carving with heat-resistant fat. It is desirable to make it also on joints of connections.