Two-Stroke Wankel Type Rotary Engine: A New Approach for Higher Power Density

Abstract

The Wankel engine is a rotary type of four-stroke cycle internal combustion engine. The higher specific power output is one of its strong advantages. In Wankel rotary engine, every eccentric shaft revolution corresponds to one four-stroke cycle, whereas conventional reciprocating engine fulfills four-stroke cycle in two crankshaft revolutions. This means the power stroke frequency is twice that of conventional engines. Theoretically, application of two-stroke cycle on Wankel geometry will duplicate the power stroke frequency. In this research, a single-zone thermodynamic model is developed for studying the performance characteristic of a two-stroke Wankel engine. Two different port timings were adapted from the literature. The results revealed that late opening and early closing port geometry (small opening area) with high supercharging pressure has higher performance at low speed range. However, as the rotor speed increases, the open period of the port area becomes insufficient for the gas exchange, which reduces power performance. Early opening and late closing port geometry (large opening area) with supercharging is more suitable in higher speed range. Port timing and area, charging pressure, and speed are the main factors that characterize output performance. These preliminary results show a potential for increasing power density by applying two-stroke cycle of the Wankel engine.

Modelling A Single-Rotor Wankel Engine Performance With Artificial Neural Network At Middle Speed Range

“…As can be seen from the comparison on Figure 1, the reciprocating engine performs the four-stroke cycle in two crankshaft revolutions (720 ℃A-Crank Angle) while the eccentric shaft of Wankel engine fulfills three revolutions at each rotor revolution (1080°EA-Eccentric Angle) as the rotor completes its own 4-stroke cycle at each revolution. This means that each eccentric revolution in the shaft corresponds to one four-stroke and let engine generate power accordingly [2]. So that according to the working principle, Wankel engine has advantages in terms of efficiency, smoothness, compactness, high revolutions per minute and a high power-to-weight ratio compared to reciprocating engines.…”

“…Considering modelling process, two approaches; thermodynamic models and fluid dynamic models come forward. [2,5]. As can be seen from the modelling approaches, almost all the modelling approaches and related developments are to investigate Wankel engines mechanically except some of the useful studies which are mainly focus on the control for the test and analyze purposes [1,7].…”

“…The Wankel engine is a rotary type of four-stroke cycle internal combustion engine. Different from the conventional linear piston or reciprocating engine that processes two crankshaft revolutions for one four-stroke cycle, Wankel engine completes one four-stroke cycle with one eccentric shaft revolution [1,2]. Research and development studies for the Wankel engine have started in 1950s with the NSU Company and continued by various companies, researches [3] and institutes.…”

“…Wankel engines attract attention because of their simple rotational motion without reciprocating parts. Beside the weakness in terms of wear, leakage and fuel consumption lead Wankel engines fail in long term usage [2,6]. Considering heavy and complicated moving parts such as pistons and rods of reciprocating engines, Wankel (Rotary) engines come to the forefront with higher power output, simpler structure, lower NOx emissions and lower vibration advantages.…”

A Design of the Compression Chamber and Optimization of the Sealing of a Novel Rotary Internal Combustion Engine Using CFD

“…On the other hand, there is no intense research on rotary engines, resulting in only one commercially available engine for passenger cars, the (four stroke) Wankel engine, also used in other applications (e.g., aviation, motorsport) [12], while its two-stroke version is also examined in combination with supercharging aiming at higher power density [13]. The main drawbacks of this engine are the combustion chamber shape (high surface to volume ratio at ignition) and the leakage of the working medium between the adjacent chambers (blow-by effect) [14].…”