Influence of combustion chamber shape on the gas-dynamic characteristics of air swirl

   The article is devoted to the study of the influence of the combustion chamber shape of a piston internal combustion engine on the gas-dynamic characteristics of the air swirl, i. e., on the mean and fluctuating flow velocity, turbulence intensity, and the Kolmogorov scale. The literature review has shown that the gas-dynamic characteristics of the air swirl significantly affect the dynamics of the fuel combustion process and, consequently, the environmental and energy performance of the engine.

   It is noted that improving the gas-dynamic characteristics of the air swirl is an important stage in the design of new engines.

   The combustion chamber shape was varied using pistons with different crown geometries: flat, hemispherical, Hesselman, and YaMZ with a truncated cone. A methodology for numerical simulation of a piston engine is presented. The grid convergence analysis in calculating the turbulence characteristics of the air swirl has demonstrated the feasibility of using hexahedral cells with a size of 0.5–1 mm in the computational mesh of the engine.

   Based on this, it is concluded that when calculating thermodynamic characteristics, the use of course meshes with a cell size greater than 4 mm is acceptable.

   The application of numerical simulation methods implemented in the ANSYS Fluent software package made it possible to study in detail the gas-dynamic characteristics of the flow and their dependence on the crankshaft rotation angle and the combustion chamber shape. It is shown that the degree of influence of the combustion chamber shape on the gas-dynamic characteristics significantly depends on the crankshaft rotation angle. It is established that for all combustion chamber shapes, as the piston approaches top dead center, a peak in turbulence intensity and a minimum Kolmogorov scale are observed; therefore, at top dead center, the influence of turbulence on the combustion process is maximal. The results may be of practical relevance for studying engine working processes using computational fluid dynamics methods.

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