Scroll-type supercharger
Encyclopedia
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
. It is a compromise between the more rugged rotating lobe, and the more efficient sliding vane type superchargers, and is considered to offer the highest potential in regard to efficiency, noise and pressure fluctuation.
History
The basic concept of the scroll-type supercharger was invented by Léon Creux of France in 1905, originally for aircraft use, though Creux did consider it as a possible form of steam engineSteam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
. However, Creux's supercharger failed due to the relatively poor casting
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...
techniques available at the time. This type of supercharger has not seen widespread use in the aviation role, but has been used on a small number of automotive applications.
Description
The moving parts of the supercharger is a disc-shaped displacer with identical spirals (or scrolls) projecting from each side, and manufactured from light alloy to reduce inertiaInertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
. A pair of fixed scrolls supported by the end walls of the compressor chamber are interleaved with the moving scrolls. Rather than rotating, the displacer is driven in an orbital motion to create a pumping action between the pairs of scrolls.
Air is pulled into the device when the moving scrolls are at their furthest from the fixed scrolls, leaving a large gap. As the shaft rotates the gap closes, and the point of widest opening rotates to a point further "into" the charger. As the process continues the gap eventually ends up on the middle of the housing, at the point where the higher pressure air exhausts into the engine. The scrolls are shaped so the gap slowly decreases in size as it moves to the centre, thereby compressing the air.
The edges of the scrolls are sealed by strip-type seals, while the supercharger's main shaft bearings use radial seals to prevent the charge air from becoming contaminated with oil.
Volkswagen G-Lader
The most common and well known scroll-type supercharger is the G-LaderG-Lader
The G-Lader is a scroll-type supercharger used in various Volkswagen Passenger Cars models. Its purpose is to increase the motive power output from the internal combustion engine attainable with a given engine displacement. Since it is not enough to simply inject more fuel, as this produces too...
(Lader is German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
for charger), designed by Volkswagen
Volkswagen
Volkswagen is a German automobile manufacturer and is the original and biggest-selling marque of the Volkswagen Group, which now also owns the Audi, Bentley, Bugatti, Lamborghini, SEAT, and Škoda marques and the truck manufacturer Scania.Volkswagen means "people's car" in German, where it is...
for use in a version of the Mk2 Polo
Volkswagen Polo
The Volkswagen Polo is a supermini car manufactured by Volkswagen. It is sold in Europe and other markets worldwide in hatchback, saloon, coupé and estate variants....
called the GT G40
Volkswagen Polo G40
The Volkswagen Polo Mk2 and Polo Mk2F were available as supercharged G40 models - called the Volkswagen Polo G40 .-Mk2:...
. Launched first as a limited batch of about 500 cars in 1987, most were sold to Volkswagen workers. A normal production version of the G40 was launched as part of the Mk2F range. The name comes from the "G" shape of its compression channels. It was mounted on a 1272 cc petrol engine
Petrol engine
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol and similar volatile fuels....
, which offered performance about that of a 2 litre normally aspirated engine.
A similar, but larger G60
G60
G60 refers to an inline-four cylinder automobile petrol engine, which uses a specific method of forced induction - by way of a specific type of supercharger...
became available in the Volkswagen Corrado
Volkswagen Corrado
The Volkswagen Corrado is a hatchback coupé developed by German automaker Volkswagen and built by Karmann in Osnabrück, Germany, between 1 September 1988 and 31 July 1995....
during the early 1990s
1990s
File:1990s decade montage.png|From left, clockwise: The Hubble Space Telescope floats in space after it was taken up in 1990; American F-16s and F-15s fly over burning oil fields and the USA Lexie in Operation Desert Storm, also known as the 1991 Gulf War; The signing of the Oslo Accords on...
, and was also available in limited numbers in the Volkswagen Passat
Volkswagen Passat
The Volkswagen Passat is a large family car marketed by Volkswagen Passenger Cars through six design generations since 1973. Between the Volkswagen Golf / Volkswagen Jetta and the Volkswagen Phaeton in the current Volkswagen line-up, the Passat and its derivatives have been badged variously as...
and Volkswagen Golf
Volkswagen Golf
The Volkswagen Golf is a small family car manufactured by Volkswagen since 1974 and marketed worldwide across six generations, in various body configurations and under various nameplates – as the Volkswagen Rabbit in the United States and Canada , and as the Volkswagen Caribe in Mexico .The...
. The G60 won International Engine of the Year
International Engine of the Year
The International Engine of the Year is an annual competition for automotive industry internal combustion engines, judged by a panel of automobile journalists from around the world. It is organised by the United Kingdom's largest technical motoring, aerospace and traffic management publication...
when it was introduced in 1989.
The "40" and "60" denote the displacer scroll width in millimetres.
All supercharger types benefit from the use of an intercooler
Intercooler
An intercooler , or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric cooling, which removes...
to get rid of the heat produced during compression, and therefore help increase the density of the charged air.