Comparative Analysis of Quasiturbine and Wankel Rotary Engine: Two Concepts 100 Years Apart

The Wankel rotary engine, introduced nearly a century ago, has undergone extensive development but has never posed a serious challenge to piston engines. While it demonstrated the feasibility of rotary designs, it also raised concerns about their practicality. This paper compares the Wankel (WK) engine with the more recent Quasiturbine (QT) concept, introduced in 1990, which offers improved efficiency, a more favorable surface-to-volume ratio, and superior environmental performance. By analyzing the conceptual strengths and limitations of both engines, this study aims to highlight the potential of rotary engines in modern applications, including hydrogen fuel and detonation techniques. The Wankel (WK) concept (based on an eccentric piston-like shaft) requires extensive explanation, as its triangular Rotor does not fit easy into the orthogonal Stator geometry, as it has a hybrid nature producing 70 % of his power radially and 30 % tangentially, as it has a 25 % torque dead time per rotation, and exhausts in a common chamber with fresh fuel mixture (somewhat like does the 2-stroke piston?). This explains why several conceptual difficulties of the Wankel engine remain unresolved. The Quasiturbine (QT) engine concept has received considerable attention for properties different from the Piston and the Wankel, and by explaining how the Wankel could have totally avoided difficulties in the first place. The Quasiturbine cycle is unique as the strokes do not experience acceleration reversal, firing at TDC with blades at their maximum tangential velocity and accompanying the fluid flow until the BDC at minimum (not null) velocity. Also unique, 100 % of the torque comes from the tangential chamber pressure (not radially) without torque dead time. All Quasiturbine components are external parts, including the Rotor accessible from the engine center. This step-by-step analysis of two complex engine devices with numerous differences, is a necessary piece of knowledge toward solutions not only equivalent, but superior to Piston engine in term of power density and environmental cleanness.