What is a turbocharged car engine?

Turbocharged engine

Turbo engine. The task of increasing engine power and torque has always been relevant. Engine power is directly related to the displacement of the cylinders and the amount of air-fuel mixture supplied to them. That is, the more fuel burns in the cylinders, the more power is developed by the power unit. However, the simplest solution is to increase engine power. An increase in its working volume leads to an increase in the dimensions and weight of the structure. The amount of the supplied working mixture can be increased by increasing the speed of rotation of the crankshaft. In other words, the implementation of more work cycles in cylinders per unit of time. But there will be serious problems associated with an increase in inertia forces and a sharp increase in mechanical loads on the parts of the power unit, which will lead to a reduction in engine life.

Turbo engine efficiency

The most effective way in this situation is power. Imagine the suction stroke of an internal combustion engine. The engine at the time works like a pump, and is also very inefficient. The duct has an air filter, bends in the intake manifold, and gasoline engines also have a butterfly valve. All this, of course, reduces the filling of the cylinder. To increase pressure in front of the inlet valve, more air will be placed in the cylinder. Refueling improves the filling of the cylinders with a fresh charge, which allows them to burn more fuel in the cylinders and thus obtain higher engine power. Three types of amplification are used in an internal combustion engine. Resonance that uses the kinetic energy of the air volume in the intake manifolds. In this case, no additional charge / boost is required. Mechanical, in this embodiment, the compressor is driven by a motor belt.

Gas turbine or turbo engine

A gas turbine or turbocharger, the turbine is driven by an exhaust stream. Each method has its advantages and disadvantages, which determine the scope. Personal intake manifold. For better filling of the cylinder, the pressure in front of the inlet valve should be increased. Meanwhile, increased pressure is not necessary at all. It is enough to lift it at the moment of closing the valve and load an additional portion of air into the cylinder. For a short-term pressure increase, a compression wave that runs along the intake manifold with the engine running is ideal. It is enough to calculate the length of the pipeline itself so that the wave reflected several times from its ends reaches the valve at the right time. The theory is simple, but its implementation requires considerable ingenuity. The valve does not open at different speeds of the crankshaft and, therefore, use the effect of resonant amplification.

Turbo engine - dynamic power

With a short intake manifold, the engine performs better at high speeds. While at low speeds, a long suction path is more efficient. The variable inlet pipe length can be created in two ways. Either by connecting a resonant chamber, or by switching to the desired input channel or connecting it. The latter option is also called dynamic power. Resonant and dynamic pressure can accelerate the flow of the intake column. The amplification effects caused by fluctuations in air pressure are in the range of 5 to 20 mbar. For comparison, using a turbocharger or mechanical gain, you can get values ​​in the range from 750 to 1200 mbar. To complete the picture, we note that there is still an inertial amplifier. In which the main factor for creating excess pressure in front of the valve is the head with a high flow pressure in the inlet pipe.

Increasing the power of the turbo engine

This gives a slight increase in power at high speeds of more than 140 kilometers per hour. Mainly used on motorcycles. Mechanical fillers allow a fairly simple way to significantly increase engine power. Bringing the engine directly from the engine crankshaft, the compressor is able to pump air into the cylinders at a minimum speed without delay, increasing the boost pressure in strict proportion to the engine speed. But they also have flaws. They reduce the efficiency of the internal combustion engine. Because part of the power generated by the power supply is used to drive them. Mechanical pressure systems take up more space, require a special drive. The timing belt or gearbox makes a loud noise. Mechanical fillers. There are two types of mechanical superchargers. Volumetric and centrifugal. Typical bulk fillers are Roots supergenerators and a Lysholm compressor. The design of Roots resembles an oil gear pump.

Features turbo engine

The peculiarity of this design is that the air is not compressed in the supercharger, but outside in the pipeline, getting into the space between the housing and the rotors. The main disadvantage is the limited amount of gain. No matter how accurately the filler parts are set, when a certain pressure is reached, air begins to flow back, reducing the efficiency of the system. There are several ways to fight. Increase the rotor speed or make the supercharger two or even three stages. Thus, it is possible to increase the final values ​​to an acceptable level, but multi-stage designs do not have their main advantage - compactness. Another disadvantage is uneven discharge of the outlet, as the air is supplied in portions. Modern designs use triangular swivel mechanisms, and the entrance and exit windows are triangular in shape. Thanks to these techniques, bulky superchargers practically got rid of the pulsating effect.

Turbo engine installation

Low rotor speeds and hence durability, coupled with low noise levels, have resulted in well-known brands such as DaimlerChrysler, Ford and General Motors generously equipping their products. Displacement superchargers increase power and torque curves without changing their shape. They are already effective at low to medium speeds and this best reflects the acceleration dynamics. The only problem is that such systems are very fancy to manufacture and install, which means they are quite expensive. Another way to simultaneously increase the air pressure in the intake manifold was proposed by the engineer Lisholm. The design of the Lysholm fittings is somewhat reminiscent of a conventional meat grinder. Two additional screw pumps are installed inside the housing. Rotating in different directions, they capture part of the air, compress it and place it in cylinders.

Turbo engine - tuning

Such a system is characterized by internal compression and minimal loss due to precisely calibrated clearances. In addition, the pressure of the screw acts in almost the entire range of engine speeds. Quiet, very compact, but extremely expensive due to manufacturing difficulties. However, they are not neglected by such well-known tuning studios as AMG or Kleemann. Centrifugal fillers are reminiscent of turbochargers in design. Excessive pressure in the intake manifold also creates a compressor wheel. Its radial blades capture and push air around the tunnel using centrifugal force. The difference from the turbocharger is only in the drive. Centrifugal blowers have a similar, albeit less noticeable, inertial defect. But there is another important feature. In fact, the magnitude of the generated pressure is proportional to the square speed of the compressor wheel.

Turbo engine

Simply put, it must rotate very quickly in order to pump the necessary charge of air in the cylinders. Sometimes ten times the engine speed. Efficient centrifugal fan at high speeds. Mechanical centrifuges are less convenient to use and more durable than gas centrifuges. Because they work at lower extreme temperatures. The simplicity and, accordingly, the cheapness of their design have gained popularity in the field of amateur tuning. Intercooler engine. The mechanical overload control circuit is quite simple. At full load, the bypass cover is closed and the inductor is open. All air flow enters the engine. During part-load operation, the throttle valve closes and the pipe damper opens. Excess air returns to the inlet of the supercharger. The charging cooling air included in the Intercooler circuit is an almost indispensable component of not only mechanical, but also gas turbine amplification systems.

Turbocharged engine

Compressed air is pre-cooled in the intercooler before being fed into the engine cylinders. By its design, it is a conventional radiator, which is cooled either by the flow of intake air or by the cooling liquid. Lowering the temperature of the charged air by 10 degrees allows you to increase its density by about 3%. This, in turn, allows you to increase engine power by about the same percentage. Turbocharger engine. In modern car engines, turbochargers are more widely used. In fact, this is the same centrifugal compressor, but with a different drive circuit. This is the most important, perhaps the fundamental difference between mechanical superchargers and turbocharging. This is the drive circuit, which largely determines the characteristics and applications of various designs.

The advantages of a turbo engine

The turbocharger has an impeller located on the same shaft as the impeller, a turbine. Which is built into the exhaust manifold of the engine and is driven by exhaust gases. Speed ​​may exceed 200 rpm. There is no direct connection to the engine crankshaft, and the air supply is controlled by exhaust pressure. The advantages of a turbocharger include. Improving engine efficiency and economy. A mechanical drive receives power from the engine, the same uses exhaust energy, therefore, efficiency increases. Do not confuse specific and overall engine performance. Naturally, the operation of an engine whose power has increased due to the use of a turbocharger requires more fuel than a similar engine with less power with a natural aspirator.

Turbo engine power

In fact, filling the cylinders with air improves, as we recall, to burn more fuel in them. But the mass fraction of fuel per unit of power per hour for an engine equipped with a fuel cell is always lower than that of a similar design of a powerful unit without amplification. The turbocharger allows you to achieve the specified characteristics of the power unit with smaller dimensions and weight. Than in case of use of the atmospheric engine. In addition, the turbo engine has the best environmental performance. The pressure in the combustion chamber leads to a decrease in temperature and, as a consequence, to a decrease in the formation of nitrogen oxides. When refueling gasoline engines, more complete combustion of the fuel is achieved, especially in transient conditions. In diesel engines, an additional air supply allows you to push the boundaries of smoke, i.e. deal with soot particle emissions.

Diesel turbo engine

Diesels are much more suitable for boosting in general and turbocharging in particular. Unlike gasoline engines, where boost pressure is limited by the danger of detonation, they are not aware of this phenomenon. A diesel engine can be pressurized to the limit of mechanical stresses in its mechanisms. In addition, the absence of an intake air throttle and a high level of compression provide a higher exhaust pressure and lower temperature compared to gasoline engines. Turbochargers are easier to manufacture, which pays off with a number of inherent disadvantages. At low engine speeds, the amount of exhaust gas is small, respectively, the compressor efficiency is low. In addition, a turbocharged engine usually has a so-called Turboyama.

Ceramic metal turbo rotor

The main difficulty is the high temperature of the exhaust gases. A ceramic metal turbine rotor is about 20% lighter than those made from heat-resistant alloys. And it also has a lower moment of inertia. Until recently, the life of the entire device was limited to camp life. They were essentially crankshaft-like bushings that were lubricated with pressurized oil. The wear of such conventional bearings was, of course, great, but spherical bearings could not withstand the enormous speeds and high temperatures. The solution was found when it was possible to develop bearings with ceramic balls. The use of ceramics, however, is not surprising, the bearings are filled with a constant supply of lubricant. Getting rid of the shortcomings of the turbocharger allows not only to reduce the inertia of the rotor. But also the use of additional, sometimes quite complex boost pressure control circuits.

The principle of operation of a turbo engine

The main tasks in this case are to reduce the pressure at high engine speeds and increase it at low. All problems can be completely solved with the help of a turbine with a variable geometry, a turbine with a variable nozzle. For example, with moving blades, the parameters of which can be changed over a wide range. The principle of operation of the VNT turbocharger is to optimize the flow of exhaust gases directed to the turbine wheel. At low engine speeds and low exhaust volumes, the VNT turbocharger directs the entire exhaust stream to the turbine wheel. Thus increasing its power and increasing pressure. At high speeds and high gas flow rates, the VNT turbocharger places the moving blades in the open position. An increase in cross-sectional area and the removal of certain exhaust gases from the impeller.

Turbo engine protection

Protection against excessive speed and maintaining boost pressure at the required engine level, eliminating overload. In addition to single amplification systems, two-stage amplification is common. The first stage, which drives the compressor, provides effective amplification at low engine speeds. And the second, a turbocharger, uses the energy of exhaust gases. As soon as the power unit reaches a speed sufficient for normal operation of the turbine, the compressor automatically shuts off, and when they fall, it starts again. Many manufacturers install two turbochargers on their engines at once. Such systems are called biturbo or twinturbo. There is no fundamental difference between them, with one exception. Biturbo involves the use of turbines of different diameters, and hence productivity. In addition, the algorithm for their inclusion can be both parallel and sequential.

Questions and answers:

What is turbocharging for? The increased fresh air pressure in the cylinder ensures better combustion of the air-fuel mixture, which increases engine power.

What does turbocharged engine mean? In the design of such a power unit, there is a mechanism that provides an enhanced flow of fresh air into the cylinders. For this, a turbocharger or turbine is used.

How does turbocharging work on a car? The exhaust gases spin the turbine impeller. At the other end of the shaft, a pumping impeller is fixed, installed in the intake manifold.