Superchargers History and Types: Roots, Two Stroke, Screw, Diesel, Centrifugal, Variable Ratio, Rotary Vane, and Scroll-Type Superchargers
You may find it surprising that superchargers were invented before automobiles. Over the years, new types of superchargers were created and advancements have been made on them along the way. Since there are multiple uses for superchargers other than in automobiles, superchargers have a bit of a complex history. For the purpose of this article I’m going cover supercharges used in automobiles.
Common Terms: Superchargers, Compressors, and Blowers
Before I get started on the the different types of superchargers, I want to clear something up. There is some confusion as too what the terms supercharger, compressor, and blower are referring too. In practical conversation, these terms are referring to the same thing. There is also some confusion about the difference between superchargers and turbo chargers. That is the topic of another article.
In 1860 Philander and Francis Roots patented the very first supercharger. This supercharger is called a “Root” type supercharger to this day, after it’s founders. The original purpose of the root supercharger was too ventilate mine shafts. The root supercharger is a type of positive displacement supercharger.
Roots superchargers are composed of two meshing lobes which are basically elongated gears. They are interlocked and spin in the same direction. As they turn, they force air between them from side of the supercharger to the other. This effectively “blows air” which is why even today, superchargers are also commonly called blowers.
Two Stroke Supercharger
Dugald Clerk was a Scottish engineer. In 1878 he developed the two stroke engine cycle and successful developed an engine using this principle in 1880. In his engine was two cyclinders, one functioning cylinder and another cylinder that functioned to fill the functioning cylinder with air. Some people consider this an early supercharger. Clerk himself stated that the purpose of this cylinder was not to compress air but rather to pump air. I think this design should be considered a precursor to superchargers.
The screw compressor was invented in Germany by Heinrich Krigar in the year 1878. The screw compressor is an advancement upon the root compressor. They look a lot alike and are both mounted on top of the engine. The difference is that the screw compressor actually compresses air as the air passes through it.
In the 1890s Rudolph Diesel (who I consider an extremely prolific inventor) was working on concept of the diesel engine. In the year of 1896 Rudolph Diesel invented the first supercharger for the diesel engine.
In 1902, Louis Renault, one of the main founders of the Renault Automotive Group, patented a centrifugal supercharger in France.
Centrifugal superchargers are the most efficient superchargers. The way centrifugal compressors work is by sucking in air at a very fast rate but the air gets slowed down on it’s way to the engine. This combination of fast suction and slowing of the airflow compresses air very effectively.
Centrifugal superchargers are small and fit under the hood easily. They attach to the front or side of the engine instead of on top. They sort of look like a giant snail. The trade off with centrifugal superchargers is that, the amount of added horsepower is dependent on how many rpms you are revving. This means that when you’re accelerating, you’re not getting the same boost as you would with other superchargers. This may sound much more like turbochargers than other superchargers and that’s because it is. Centrifugal devices are more often used as turbochargers, the difference is that turbochargers are connected to the exhaust rather than the crankshaft.
Centrifugal superchargers accomplish this by having a belt connected to the crankshaft. The belt is not connected directly to the supercharger but instead to a set of gears that that power a rotor which powers the supercharger.
Centrifugal compressors are not to be confused with centrifugal superchargers. In 1899 Auguste Rateau a man chiefly known for his work on steam technology invented the world’s first centrifugal compressor. Centrifugal compressors serve the same function as superchargers and are used on aircrafts and can be found in jet engines.
Rotary Screw Supercharger
In 1935, Alf Lysholm invented the rotary screw compressor in Sweden. This is also sometimes called the Lysholm twin screw compressor.The twin screw compressor looks a lot like the root compressor and functions but it is an advancement upon the root supercharger. The difference is that air gets compressed while it is passing through the two lobes of the twin lobe compressor. In the root compressor air doesn’t get compressed until it passes through the lobes.
Variable Ratio Centrifugal Supercharger
A variable ratio supercharger is a supercharger that functions at rpms independently from the engine’s rpms. This adds alot of functional ability to the supercharger. The driver has the capability of adjusting the supercharger from the driver’s seat. Unfortunately, most automotive variable ratio centrifugal superchargers have not been effective. There were many patents over the years, but most have not proven fruitful in the automotive field.
Rotary Vane Supercharger
Rotary vane superchargers are also called rotary vane pumps and they are used for many other applications other than in automobiles such as vacuum systems and milk machines. The rotary vane pump was invented by Charles Barnes in 1874. Rotary vane superchargers are positive displacement superchargers.
When looking at a rotary vane supercharger, it looks like a metal cylinder. What you can’t see is that inside the housing is a rotor with metal sheets called “vanes” which extend from the rotor to the internal side of the housing. There are two openings in the housing, one for air entry and one for air exit. As the rotor spins air enters, circulates through the internal side of the housing, gets compressed and exits. The rotary vane reminds of a revolving door and is a similar concept, the main difference is that in a rotary vane, the air is getting squeezed together before it exits.
The rotary vane supercharger is less popular than other superchargers. The first reason is that this supercharger requires lubrication which isn’t the end of the world but can become an extra hassle. The second reason is that rotary vane superchargers often experience more wear and tear than other superchargers which means there’s a higher likelihood that they’ll need to be replaced sooner.
The scroll-type supercharger was invented in 1905 by Leon Creux in France. This is a less commonly used supercharger than other superchargers. It is most known for it’s use in the Volkswagen GT G40. The scroll type supercharger is also called a spiral supercharger.
From the outside, the scroll-type supercharger looks like a metal dome. On the inside are two metal sheets bent into the shape of spirals. The two metal spirals are the same size with one being placed inside the other. The outside spiral is fixed in placed and the inner spiral oscillates. This creates a maze for the entering air and as air travel through the maze into narrower air it becomes compressed.