Gas flow behaviour is an extremely complicated question on internal combustion engine and plays a key role in air-fuel mixing performance. A proper mixture process significantly improves the combustion performance and thus enhances the engine efficiency. This study estimates the effect of different piston bowl depths on the flow field development inside the combustion chamber of a CNG engine using Ansys Fluent. The cold flow model was utilized without considering the combustion behaviour. The three-dimensional model was developed based on a single cylinder CNG converted engine. Four different bowl heights were applied while the compression ratio was maintained as the designed value of 10. The tumble and swirl as well as the turbulent flow pattern were investigated to consider the gas flow behaviour. The simulation results indicate that the tumble and swirl ratio increase with increasing of piston bowl depth. The case of bowl height 17 mm shows better flow behaviour and higher velocity for a good mixing performance as well as turbulence dissipation.
Keyword
Single cylinder CNG engine, piston bowl depth, tumble ratio, swirl ratio, turbulent kinetic energy (TKE)
