Analysis of the Design Features of the Wankel and Szorenyi Rotary Engines

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. The paper analyses the Wankel engine’s geometry which causes an excessive eccentric shaft deflection due to the centrifugal force of the rotor that is eccentric to the engine centreline and which results in limiting the engine rotor to low revs; a combustion chamber shape that causes a high-speed transfer of the combusting gases (the ‘squish’ effect) which results in incomplete combustion; and a large overlap of intake and exhaust timing which results in excessive leakage between chambers. The analysis reveals that these deficiencies are inherent to the geometry of the engine and cannot be practically overcome. The analysis of the Szorenyi engine reveals that, whilst also geometrically based, it has a balanced rotor which will not result in a need to limit the engine revs; a combustion chamber which does not exhibit the same squish effect; and has ideal Otto cycle port timing. The paper concludes that the Szorenyi engine concept has significant advantages over the Wankel and reciprocating engines and can replace it in a broad range of applications.