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Truck Encyclopedia (19): Supercharging and turbocharging have to be called brothers
Today's truck encyclopedia is a simple science popularization of how superchargers work.
▎The turbo has to be called grandpa when it sees it - supercharging
Mechanical supercharging first appeared in 1860, when Philander and Francis Roots invented and applied for the "Rouge" mechanical supercharging technology. At that time, this technology was not used in cars, but as a ventilation device for mines. Directly in 1900, Gottleib Daimler installed a Lu-type supercharger on a car engine for the first time, which was indissoluble with the car.
When mechanical supercharging was first invented, it was called Supercharge, and later after the invention of turbocharging, in order to distinguish between the two, turbochargers were called Turbo Superchargers, and mechanical superchargers were called Mechanical Superchargers. Over time, the two were simplified to Turbocharger and Supercharger respectively
● Step by step and calmly supercharge
There is a clear difference in power output between mechanical supercharging and turbocharging, the former has a linear output close to natural air intake, while the latter has a little more abruptness and less calmness because of the phenomenon of turbo hysteresis.
The advantage of supercharging is that the compressor is directly driven by the engine crankshaft, as long as the accelerator is stepped on, the supercharger speed will increase with the engine speed, and there will be no power lag, so the output performance of the supercharged engine is very similar to that of a naturally aspirated engine, but it can have greater horsepower and torque.
The disadvantages of supercharging are fuel consumption and compressor efficiency. The compressor needs to consume engine power, and it enters the working state from the moment the engine starts, consuming engine power all the time. Now there is also a plan to add a clutch to the supercharger, which is disconnected when it is not needed to work to save engine power.
Compared with the supercharging of exhaust gas turbines, the efficiency of superchargers is still lower.
▎How does a supercharger work?
According to the different principles of supercharging, the supercharger mainly includes Lu supercharging, roots supercharging (double worm), centrifugal supercharging, in addition to rolling supercharging and other supercharging forms, let's talk about them one by one.
● Lu supercharger
The Lu supercharger is the supercharger invented in 1860 that we introduced above. The Lu supercharger consists of two rotors that mesh, which rotate to draw in external air for supercharging.
The rotor of the early Lu supercharger was straight toothed like the rotor in the animation above, and was improved in the later period to engage in a helical tooth manner.
The load of the helical rotor is not as hard as the straight rotor, so the helical rotor works more smoothly, the impact vibration is small, and the silence is better.
A simple understanding of the Lu supercharger is like a meat grinder, and the meat here is air. Air enters perpendicular to the rotor axis and flows out in the same direction.
● Double worm supercharger (roots fan)
The double worm supercharger, also known as the roots blower, is very similar to the Rouge supercharger.
The double worm supercharger also draws in air through a set of worm rotors that engage the flange. Unlike Lu's supercharger, the worm of the double helix supercharger is an asymmetrical worm, one male and one female.
When the air flows from the inlet to the exhaust port of the supercharger, the air is further compressed with the contraction of the airway, so that the compression of the air can be carried out continuously.
This not only improves the compression efficiency of the supercharger, but also makes the supercharger not need to be very large. Therefore, the double worm supercharger is more efficient than the Lu supercharger.
● Centrifugal supercharger
The principle of centrifugal supercharger is similar to that of exhaust gas turbocharger, which also sucks air into the narrow compressor housing at high speed through the rotation of the impeller for pressurization. However, the impeller of the centrifugal supercharger is driven by the engine, which is not limited by the amount of exhaust gas, and as long as the engine is in working condition, the centrifugal supercharger can provide supercharging.
Because it is similar to an exhaust gas turbine, many people will think that it is an exhaust gas turbocharger. But in terms of drive form, the centrifugal supercharger is a real supercharger.
● Rolling supercharger VW G-Lader Supercharger
Rolling superchargers are now basically hard to find. In the 90s of the 20th century, rolling superchargers were assembled by Volkswagen on top of the Volkswagen POLO G40 and Corrado G60.
The principle is to arrange an eccentric drive wheel in the center of a spiral-shaped air intake channel, and then install another spiral blade on the drive, and the spiral blade is parallel to the spiral air intake.
Under the rotation of the eccentric wheel, the spiral blades continue to roll in the spiral inlet channel, continuously squeezing the incoming air to form pressurization.
Almost all trucks today use diesel engines, and the high compression ratio of diesel oil makes it very suitable for turbocharging. In addition, the smoothness improvement brought by supercharging does not have obvious advantages and attractions for trucks, so few truck engines are equipped with supercharging now.
However, as a long-standing supercharging technology, mechanical supercharging is still worth learning and researching. If you have any other thoughts and discussions about superchargers, please leave a message in the comment area below and share it with your circle of friends.
Today's principle and structural form of supercharger are introduced here. The supercharger is not as efficient and valuable as exhaust gas turbocharging, but its unique charm still has a place in the hearts of some manufacturers and enthusiasts.
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