Numerical Investigation of the Combined Influence of Three-Plug Arrangement and Slot Positioning on Wankel Engine Performance

Shimon Pisnoy,Leonid Tartakovsky

doi:10.3390/en14041130

Abstract

A numerical methodology for three-dimensional fluid dynamics and chemical kinetics simulation of the combustion and gas-exchange processes in the Wankel engine was developed and validated. Two approaches of performance enhancement were studied—the addition of a slot in the rear side of the rotor recess, and installation of a third plug in the trailing side of the working chamber, in addition to the two available plugs mounted in the leading side of the baseline engine. The obtained results showed that the suggested three-plug arrangement significantly improves the engine performance. Furthermore, positioning the trailing plug further from the passage between the trailing and leading sides is of preference for higher mean in-chamber pressures. Nevertheless, for maximum performance, the distance should be brought to an optimum as during the intake stroke there is a loss of inducted charge due to backflow from the trailing plug hole. For the three-plug arrangement the presence of a slot is necessary for the prevention of early flame quenching in the trailing side, while keeping the added volume to a minimum. Moreover, positioning the slot and the trailing plug off-center, results in higher flow intensity towards the leading plugs, and accordingly, to a higher combustion efficiency. For dual-plug ignition system (two plugs in the leading side) it is preferable to maintain minimum clearance in the trailing side.

Highlights

For many years, the rotating configurations of internal combustion engines have attracted great attention as a promising alternative to the fundamental drawbacks of conventional reciprocating engines [1]
The results showed satisfactory correspondence of the calculated values of brake power and fuel consumption compared to the measured values
A 3D numerical model addressing the fluid dynamics and chemical kinetics was developed and implemented for the purpose of gaining deeper understanding of the physical phenomena occurring during combustion in the working chamber of the Wankel engine

Summary

Introduction

The rotating configurations of internal combustion engines have attracted great attention as a promising alternative to the fundamental drawbacks of conventional reciprocating engines [1] In this context, the Wankel engine uniqueness is that it has no conversion of linear reciprocating motion to the rotational one, and no reciprocating inertia forces, with their subsequent losses. The inner housing volume is divided by the rotor into three working chambers executing three full four-stroke cycles over each rotation of the rotor, or alternatively, over three rotations of the output shaft This geometrical arrangement greatly affects the flame propagation process as the resulted displacement volume is of a flattened shape and with high surface-to-volume ratio [4]. When most of the air-fuel mixture in the leading side is consumed, the burning rate slows down as it becomes mainly controlled by the flow rate of the fresh air-fuel mixture flowing from the edges of the working chamber

Methods

Findings

Discussion

Conclusion