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A numerical study was conducted to examine how leakages across apex seals affect the flow field in one combustion chamber of a motored, two-dimensional, Wankel rotary engine. Results are presented which show the effects of engine speed, leakage area, and compression ratio on velocity field, distribution of turbulent kinetic energy, and volume-averaged pressure when there are apex seal leakages. These results indicate that apex seal leakages can have a significant effect on the flow field. This numerical study is based on the density-weighted-ensemble-averaged continuity, “full compressible” Navier-Stokes, and total energy equations, closed by a k-ε model of turbulence with wall functions. The numerical method used to obtain solutions was the approximate factorization algorithm of the ADI type. All convection terms were treated by second-order accurate upwind differencing through flux-vector splitting. All diffusion terms were treated by second-order accurate central differencing.

A computer program -- LeRC3D.Wankel -- was developed to study the flow, spray, and spray combustion in the combustion chambers of Wankel rotary engines. LeRC3D. Wankel is based on an Eulerian-Lagrangian formulation. The gas phase was modelled by an Eulerian approach using the density-weighted, ensemble-averaged conservation equations of mass, momentum (full compressible Navier-Stokes), total energy, and species, closed by a low Reynolds number k-ε turbulence model. The liquid phase, made up of fuel droplets, was modelled by using a Lagrangian approach in which droplet groups are tracked in time. The combustion process which takes place after fuel droplets evaporate and mix with the surrounding air was assumed to be chemical kinetics controlled via a two-step global mechanism. This paper describes the formulation employed in the computer program as well as the essence of the numerical method used to generate solutions. Some computed solutions for the flow field are also presented.

The meaningfulness of numerical studies on Wankel engine flow fields depends strongly on turbulence modelling and the numerical methods used to obtain solutions. This investigation examined two different turbulence models and several variations of a numerical method for calculating turbulent flow fields inside one of the combustion chambers of a motored, two-dimensional Wankel engine. The two turbulence models examined were the standard k-ε model with wall functions and the low Reynolds number k-ε model of Chen and Patel. The numerical method used in this investigation was the approximate-factorization method of the ADI type with upwind differencing of the convection terms based on flux-vector splitting.

The effects of mixture stratification at the intake port and gaseous fuel injection on the flow field and fuel-air mixing in a two-dimensional rotary engine model have been investigated by means of a two-equation model of turbulence, an algebraic grid generation method and an approximate factorization time-linearized numerical technique. It is shown that the fuel distribution in the combustion chamber is a function of the air-fuel mixture fluctuations at the intake port The fuel is advected by the flow field induced by the rotor and is concentrated near the leading apex during the intake stroke. During compression, the fuel concentration is highest near the trailing apex and lowest near the rotor. The penetration of gaseous fuel injected into the combustion chamber during the compression stroke increases with the injection velocity and results in recirculation zones between the injector and the leading apex and between the injector and the trailing apex.