Orbital engine
Encyclopedia
The Sarich orbital engine is a type of internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

, featuring rotary rather than reciprocating motion of its internal parts. It differs from the conceptually similar Wankel engine
Wankel engine
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...

 by using a shaped rotor that rolls around the interior of the engine, rather than having a trilobular rotor that spins "in place".

Overview

The theoretical advantage is that there is no high-speed contact area with the engine walls, unlike in the Wankel where edge wear is a problem. However, the combustion chambers are divided by blades which do have contact with both the walls and the rotor, and are said to have been difficult to seal due to the perpendicular intersection with the moving impeller.
The orbital engine was invented in 1972 by Ralph Sarich
Ralph Sarich
Ralph Tony Sarich is a Western Australian multi millionaire businessman and qualified engineer of Croatian descent—his parents came to Australia in 1930 from the Šibenik area. He was responsible for developing the Orbital Engine in 1972...

, an engineer from Perth, Australia, who worked on the concept for years without ever producing a production engine. A prototype was demonstrated, running on the bench with no load. The engine can run on compressed air or steam. The engine does not need oil to run at all. It produces very high revs. It has only one moving part which can be run as a pump.

Technical Problems

The Sarich orbital engine has a number of fundamental unsolved problems that have kept it from becoming a practical engine. Some key components cannot be cooled and others cannot readily be lubricated. It is very susceptible to overheating. At one press conference where Ralph Sarich presented the engine, automotive engineer Phil Irving
Phil Irving
Philip Edward Irving OBE, C.Eng., M.I.Mech.E., M.S.A.E., was an Australian engineer and author, most famous for the Repco-Brabham Formula One and Vincent motorcycle engines...

 (designer of the Vincent Motorcycle and Brabham Formula One
Formula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

engines) pointed out a number of technical difficulties.
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