Roots type supercharger
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The Roots type supercharger or Roots blower is a positive displacement type device that operates by pulling air through a pair of meshing lobes not dissimilar to a set of stretched gears. Air is trapped in pockets between the lobes and carried between the intake side to the exhaust. The supercharger is typically driven directly from the engine's crankshaft via a belt.
It is named for the brothers Philander and Francis Roots, who first patented the basic design in 1860 as an air pump for use in blast furnaces and other industrial applications. In 1900, Gottlieb Daimler included a Roots-style supercharger in a patented engine design, making the Roots-type supercharger the oldest of the various designs now available.
Out of the three basic supercharger types the Roots has historically been considered the least efficient. However, recent engineering developments by Eaton Corporation has resulted in a new Roots type supercharger that yields a pump that is more efficient than all previous models and supercharger types. In addition, the Roots type supercharger is simple and widely used and thus is invariably the most cost efficient. It is also more effective than alternative superchargers at developing compression at low engine rpms, making it a popular choice for passenger automobile applications. Peak torque can be achieved by about 2000 rpm.
All supercharger types benefit from the use of an intercooler to remove heat produced during compression.
The Roots design is commonly used on two-stroke diesel engines, which require some form of forced induction since there is no intake stroke. In this application, the blower does not often provide significant compression and these engines are considered naturally aspirated; turbochargers are generally used when significant boost is needed.
The superchargers used on top fuel engines, funny cars, and other dragsters, as well as hot rods, are in fact derivatives of General Motors superchargers for their diesel engines, which were adapted for automotive use in the early days of the sport. The model name of these superchargers delineates their size; i.e. the once commonly used 6-71 and 4-71 blowers were designed for General Motors diesels having 6 cylinders of 71 cubic inches each, and 4 cylinders of 71 cubic inches each, respectively. Current competition dragsters use blowers of 14-71 design.
[edit] References
- (April 5, 2002). Roots Type Superchargers Explained. SuperchargersOnline.com. Accessed September 11, 2004.
- Blower Briefing. Tom Henry Racing. Accessed September 11, 2004.
- Eaton TVS Supercharger The Eaton TVS Supercharger. Accessed November 11, 2006
