With the continuous advancement of social productivity and technology, how can people's demand for transportation vehicles continue to increase, and how can a small-displacement engine burst into a large-displacement engine? Pressurization technology is one of the most effective methods. The air intake pressurization technology we currently use in automotive engines originated from the need for flying at high altitude. We all know that the general engine uses the piston to move down to form a vacuum and sucks in air to achieve the process of air intake. This is called Naturally aspirated engine. Because the natural suction method achieves the "passive" intake action, the air intake efficiency is not high due to thin air in the high altitude, which greatly affects the function of the engine. In order to improve the engine intake efficiency, he invented the pressurized intake technology.
Turbochanger and supercharger are two different ways of intake pressurization. The main difference lies in the way the supercharger is driven. The earliest turbochargers were all mechanical superchargers. They were called Superchargers when they were invented, and they were later developed to distinguish the two. At first, the turbocharger was called the Turbo Supercharger, and the supercharger was called the Mechanical Supercharger. Over time, the two were reduced to Turbocharger and Supercharger respectively. The Germans called the supercharger Kompressor because of the German language. This is why the Mercedes-Benz 1.8L supercharged engine is called 200K. The German vocabulary Kompressor is also printed on other German cars equipped with a supercharger. on.
The mechanism and working principle of the turbochanger:
"Turbo fans often reach tens of thousands of revolutions during normal operation."
Turbocharging is driven by the exhaust gas from the engine. The turbine consists of two parts. One is the fresh air pressurization end (compression pump wheel) and the other is the exhaust gas drive end (exhaust turbine). There is an impeller at both ends and there is a leakage between the two turbines on the same shaft. The Wastegate is located on the side of the exhaust turbine. When the pressure of the compression turbine is too high, the pressure will push the trigger to open the valve of the exhaust turbine and lower the pressure to prevent excessive pressurization.
Turbocharger used in VW Group's classic 1.8T engine
The bearing of the turbine axle is the bearing design inside the bush sleeve. The bearing design can be divided into ball bearing and floating bearing. The rotational power of the turbocharger impeller comes from exhaust gas. Exhaust gas drives the turbine, on the other side of the turbine, the blades compress the air. The turbocharger housing is made of nickel, chromium and silicon alloys, and the shafts are chromium and molybdenum alloy materials. More importantly, the turbocharger is operated under high temperature and high speed conditions. In order to ensure its normal operation, the turbocharger is filled with oil and coolant to ensure effective lubrication and cooling, and improve working conditions. .
"Turbocharger Working Diagram"
The exhaust gas emitted by the engine with high temperature and certain pressure enters the supercharger, and the impeller driving the shaft rotates at a high speed of up to tens of thousands or even hundreds of thousands of revolutions per minute. At idle, the impeller speed is 12,000 rpm, when the whole When the load is applied, the impeller rotation speed can exceed 135,000 rpm, and ordinary bearings cannot withstand the high temperatures and wear caused by such high speeds. Therefore, the lubrication and cooling of the oil in the turbocharger system are critical. Diesel engines also have many turbocharger systems, and the maximum boost value of diesel engines is generally higher than the maximum value of gasoline engines. It is also for the turbocharger's good heat dissipation requirements that a vehicle equipped with a turbocharger generally requires an idle operation before turning off.
Representative models of turbine engines:
"FAW-Volkswagen Magotan is equipped with a 2.0TSI engine."
"Subalu Impreza is equipped with a horizontally opposed 2.5T engine."
"The BMW 750Li is equipped with a V8 Twin Turbo engine."
"Parallel turbocharger used on BMW 7 Series"
Porsche's VTG Variable Turbine Geometry Blade Technology
Turbocharger A/R:
The A/R value is often indicated in the turbocharger sales book of the refitting market to express the characteristics of the turbine. A is the area, which refers to the transverse section of the blade turbine receiving the narrowest side inlet of the exhaust gas. Cross-sectional area, R is Radius (radius), refers to the distance between the center point of A (cross-sectional area) and the center point of the turbine body, and the ratio of the area to the distance between two center points is the A/R value.
A smaller A/R value indicates that the inlet is relatively small and the starting inertia of the turbine blade is low, the flow velocity is relatively high, the low-rotation reaction is relatively good, and the hysteresis effect of the turbine is not obvious. On the contrary, the larger the A/R value is, the larger the inlet is, the higher the blade inertia is, the slower the reaction is slower, and the turbo hysteresis is more obvious, but the performance is much more intense at high turn. In simple terms, the A/R value can reach about 0.7 for turbines with high power output, while the A/R value is about 0.2 for turbines with low torque output. Porsche's VTG variable turbine geometry blade technology achieves different turbine characteristics by changing the A/R value of the turbine.
Supercharger structure and working principle:
The driving force of the supercharger compressor comes from the crankshaft of the engine. Generally, the belt is used to connect the crankshaft pulley, which indirectly drives the torsion of the crankshaft to drive the supercharger to achieve the purpose of supercharging. According to the different structures, there are many types of mechanical supercharging, including Vane, Roots, Wankle, etc. Piston movement is also considered to be a type of mechanical supercharging. Today, the Lodz turbocharger is the most widely used, and it is the hot spot for conversion. The Lodz turbocharger has two types of double-blade and three-blade rotors. At present, the double-blade rotor is more common. Its structure is to install two serpentine-shaped rotors in the oval-shaped housing, and there is a very small gap between the rotors. Instead of being directly connected, the rotating shaft of one of the rotors is linked with the driven pulley by interlocking the helical gears. The electromagnetic clutch is mounted on the pulley of the rotor shaft. When the boost is not required, the clutch is released to stop boosting, and the clutch is controlled by Computer control to save fuel.
"Supercharger structure diagram"
The advantages of supercharging: In addition to the boost at low speeds, the power output of the boost is also proportional to the crankshaft speed. That is, the throttle response of the supercharged engine increases with the speed and the power output increases. Therefore, supercharged engine operation feels very similar to naturally aspirated, but it can have a greater horsepower and torque. The disadvantage is that the power of the engine itself is always lost, and the efficiency is not high at high revolutions.
Representative model of supercharged engine:
"Corvette ZR1 equipped with a Rhodes supercharger"
"1.8L supercharged engine used by Mercedes-Benz E200K and C200K"
Therefore, Volkswagen's GOLF 1.4TSI adopts TSI double boost technology, and one engine is equipped with two types of boosters at the same time, which draws on the advantages of two types of booster modes, making the 1.4-engine engine capable of 2.0 engine power. In simple terms, when the engine speed is low, the supercharger is used to boost the pressure and the throttle response is improved. When the high speed engine is used, the turbocharger is used to increase the supercharging efficiency. However, the manufacturing is complicated and the cost is high.
"Original Intercooler for Subaru Impreza WRX STI"
The last thing to say is that no matter what kind of pressurization method, the pressurized air must be sent to the intercooler to cool down (pressurization is equal to doing work on the air, and when the pressure increases to 1bar, the temperature will rise to 80 degrees. Left and right, after the temperature rises, the air volume will increase. When the same volume, the quality of the air entering the combustion chamber will be reduced, which will be detrimental to the boost pressure, so use an intercooler to cool it.) Excessive pressure will be in the pressure relief valve (Blow-off Wastegate) ) Let go, so sometimes we can hear the buzzing noise on the turbo car. The pressurized air is finally sent to the combustion chamber.
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