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Internal combustion engines are generally reciprocating or, to a less extent, Wankel rotary engine types. Reciprocating engines are bulky, heavy and complex, mainly due to the need for intake and exhaust valves and their associated cam-train, and their complicated crankshaft. Wankel rotary engines overcome these deficiencies but have other undesirable features. An alternative to the Wankel engine is the Szorenyi Three Chamber Rotary Engine concept created by the Rotary Engine Development Agency (REDA). This paper analyses the design features of the two rotary engine types and directly compares the merits of the designs.

Currently automotive engines are reciprocating or Wankel rotary engine types. Reciprocating engines are bulky, heavy and complex, mainly due to the intake and exhaust valves and their associated cam-train. Wankel engines have a low rotor rev limit, and have inefficient sealing of the apex seals leading to poor economy and undesirable emission gases. The Rotary Engine Development Agency (REDA) has designed a new three-chamber rotary internal combustion engine concept using an adaptation of the patented Szorenyi Curve. The new design is an evolution of the design which was the subject of SAE Technical Paper 2017-01-2413 and SAE publication ‘So You Want to Design Engines: UAV Propulsion Systems’. This paper describes the features of the new three-chamber engine concept and includes an analysis of the major shortcomings of the Wankel engine.

A four-chamber Otto cycle rotary engine, the Szorenyi Rotary Engine, has been invented and developed by the Rotary Engine Development Agency (REDA) in Melbourne, Australia. The engine concept has been awarded a U.S. Patent (Number 6,718,938 B2). A prototype engine has been constructed and a successful proof-of-concept engine test was achieved in 2008. The stator of the Szorenyi engine is a similar shape to a Wankel engine. However, the geometric shape of the engine rotor is a rhombus, which deforms as it rotates inside the contour of the mathematically defined stator. This geometry translates to a rotary engine with four combustion chambers. Each revolution of the crankshaft produces one revolution of the rotor; a complete engine cycle in each of the four chambers; and therefore four power strokes. In contrast, the Wankel engine produces one power stroke per crankshaft revolution.