History of the construction of turbocharged diesel engines

The turbochargers were used to increase the power of internal combustion engines still in the development phase of this type of technology. In 1911, a turbocharger patented by an American, at the dawn of his development, played a significant role in the military aviation-turbished gasoline engines were placed on fighter jets and bombers to improve their height. The technology has recently been used in automotive dyslexia. The first serial car with a turbo diesel was introduced in 1978. Mercedes-Benz 300 SD, and in 1981 It was followed by VW Turbodiesel.

Device and operating principle of a turbocharged diesel engine

The operating principle of the diesel engine is based on exhaust gas. Leaving the cylinder, the exhaust gases enter the turbine's retina, rotate it and the turbine of the compressor built into the airflow into the cylinders.

Thus, in contrast to atmospheric diesels, turbcompressors have pressurized air into the cylinders at higher pressure. As a result, the volume of air entering the cylinder in one cycle is increasing. In combination with an increase in the volume of the burning fuel (the proportions of the fuel-air mixture remain unchanged) this gives an increase in the capacity up to 25%.

To further increase the volume of the intake air, an intercooler is also used, a special device cooling the atmospheric air in front of the engine. In physics, it is known that cold air is less than warm. Thus, refrigeration can "push" into the cylinder more air over the cycle.

As a result, the turbine has less specific fuel consumption (in grams per kilowatt-hour) and higher capacity (the number of horsepower per litre of engine capacity). All this makes it possible to significantly raise the total power of the engine without significantly increasing its size and number of turns.

Plus and minus diesel engine with turbocharged

The reverse side of the increase in the power of the engine while preserving the common characteristics, i.e., the forcing-more intensive wear of the knots, as a consequence, a reduction of the power plant resource. In addition, turbines require special types of motor oils and strict adherence to manufacturer's recommended service periods. The air filter is even more demanding. In addition, the turbine of low pressure turbines may have a turboyama effect, which is reflected in the noticeable "eating" at low and medium engine speeds.

Turbated motors are less economical than atmospheric diesel, consuming 20 to 50% more fuel at the same volume. Another obvious disadvantage of turbo-boost system is that it is very sensitive to the wear of the piston group. Increasing the pressure of the crankcase gases reduces the turbine resource. In such conditions there is a "oil fasting" and breakage of the turbocharger. The damage to this unit may well lead to the failure of the entire engine, while the turbo diesel engines are still less maintenable than their atmospheric brothers.

In general, the presence of a technically complex turbocharger, which requires additional pressure stabilization devices, emergency discharge, and so on makes the power installation of the car more sophisticated, increasing the number of parts, thus reducing overall reliability. In addition, the resource of the turbocharger itself is much smaller than that of the engine as a whole.

Modern Diesel Engine Improvements

The system of increasing the efficiency and flexibility of diesel mode as "Common-Rail" has gained considerable popularity today. If, in the traditional diesel engine, each high pressure pump section is supplied with fuel in a separate fuel line, which is closed per injector. Even though the thickness of the fuel lines is slightly different when they are pressurized in 1500-2000 atmosphere, they are slightly but "inflated". As a result, the portion of the fuel falling into the cylinder is different from the calculated fuel. "Dovesook" increases the fuel consumption, increases the opacity and reduces the complete combustion of the fuel-air mixture.

A good engineering solution to this problem was developed simultaneously by several automakers. In the new system, the high pressure fuel pump is pumping fuel into the common fuel rail, which, among other things, plays the role of a resiver, that is, a pressure stabilizer in the path. In the ramp, there is always a constant amount of fuel that is not under the pulsating pressure, but under constant pressure.

In addition, the development of intelligent technologies has enabled electronic opening systems (in traditional diesels, injection cycles are mechanically controlled by increasing pressure in the pipeline). The electronic unit, which controls the performance of the nozzles, shall take into account information on the position of the accelerator pedal, pressure in the ramp, engine temperature, load on the engine, etc. On the basis of this data the fuel portion of the fuel shall be calculated and fed.

Another novelty introduced by the development of automotive electronics is two-stage fuel feed into the combustion chamber. First, we're looking for a "split" (about a milligram). When combustion is added to the effect of compression increases the temperature in the chamber, and the main dose injected with the trace burns more smoothly, also increasing the pressure in the cylinder. As a result, the engine works softer and less noisily, while the fuel consumption is reduced by about 20% while torque is increased by 25%. What is important is reducing the soot in the exhaust.

Among the new developments designed to improve the environmental performance of the diesels while optimizing their economy, BlueTec is the most promising system developed by the specialists of Daimler AG. The main part of it is an innovative procedure for the catalytic reduction of exhaust gas.

Catalytic converters of modern vehicles work at the expense of ceramic or metallic "honeycomb", covered with a layer of reactive substances-catalysts. Catalyst oxidizes or restore toxic compounds of CO, CH and NOx to carbon dioxide, simple nitrogen and water.

However, the peculiarities of diesel fuel, as well as the processes of formation and combustion of the fuel-air mixture in diesel oil are such that the exhaust contains not only harmful chemical components, but a large amount of soot. Moreover, if you start to reduce the share of soot, the content of NOx increases, and vice versa. Thus, for the complex treatment of diesel exhas, a multicomponent chemist is needed, a mechanical system that complicates the construction of a car and, as a consequence, reduces the profitability of production.

BlueTec technology is built on a combination of traditional and new solutions. The exhaust gas has begun to pass through the resistance of the majority of diesel vehicles and the catalyst for "killing" carbon. Then, the exhaust injection is sprayed with an active reagent AdVlue based on urea (ammonia solution in water). The resulting mixture is placed in a special election catalyst (SCR), where ammonia from AdBlue under the influence of catalysis at 250-300 ° C is effective in the chemical reaction of nitrogen oxides by "taking" them to nitrogen and water. The rest of the harmful components are being burned here.

With obvious pros, BlueTec has no less obvious disadvantages. The Store of an AdLog component requires a separate capacity. The system itself is complicated by the presence of additional hubs and highways. In addition, the system is even more lustful to the quality of fuel and can only operate on salting with minimal sulphur content.

Another very relevant problem for Russia-the solution of Adlue is measured at minus 11.5 degrees. Therefore, BlueTec engineers are now actively working on improving systems without using urea. Today is the testing and refinement of the composite filter, platinum catalyst catalyst and two SCR-catalysts exclusively for nitrogen oxides. The system currently allows NOx to be used in diesel exhaust at approximately Euro 5.




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