Scroll-type supercharger
From Wikipedia, the free encyclopedia
The scroll-type supercharger is a positive displacement supercharger, first invented by L. Creux of France in 1905 for aircraft use. It has not seen widespread use in this role, but has since been used on a small number of automobile applications.
The supercharger assembly consists of a spiral-shaped air channel formed in the housing. A power shaft runs through the middle of the housing, set slightly eccentrically. Attached to this shaft is the moving element, another spiral-shaped channel cut to "fit into" the one in the housing. As the shaft rotates the moving spiral moves eccentrically, closer and further from the housing's spiral. It is this motion that is used to compress the air.
Air is pulled into the device when the shaft rotates so the moving spiral is at its furthest from the housing's, 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 exhaust into the engine. The scrolls are shaped so the gap slowly decreases in size as it moves to the center, thereby compressing the air.
The most famous scroll-type supercharger is the G-lader (lader is German for charger), designed by Volkswagen for use in a version of the Corrado. The name comes from the internal shaping of the housing, which looks something like the letter "G". It was mounted on a 1763cc engine known as the G60, which offered performance about that of a 2.6 litre normally-aspirated engine. The G60 won International Engine of the Year when it was introduced in 1989.
The G60 engine was also available in limited numbers in the VW Passat, VW Golf and the VW Corrado. A similar, but smaller G40 was available in the VW Polo during the early 1990s. The 40 and 60 denote the displacer scroll width in mm.
All supercharger types benefit from the use of an intercooler to get rid of the heat produced during compression.
