Gas-Dynamic Analysis of Processes in a Small-Sizes Two-Stroke Combustion Engine

ABSTRACT

The paper presents a procedure for gas-dynamic analysis of processes in the air-gas channel of a small-sized two-stroke combustion engine. All steps are described. At the first stage a three-dimensional model of the interior space of the air-gas channel of a piston small-power engine was built; this model was split into nine different volumes according to the methodology of volumes partition for different kinds of grids application, which is provided in source materials. At the second stage all required sizes and types of finite elements were set for the correct operation of functions of resplitting and layer-by-layer re-formation of a grid in the cylinder volume and in the sub piston area. At the third stage all the necessary settings in the CFD-code ANSYS Fluent were made. Such as a transient simulation method, a turbulence model, parameters of mixture formation and fuel evaporation process, setup of intersection zones of the grid, setup of permeability of the boundaries between the calculated areas, setup of grid re-formation parameters, motion parameters of the piston and other moving elements of the simulated engine were introduced, setup of parameters and characteristics of the fuel injection process. User Defined Function (UDF) was used to set the rotation of the crankshaft. The calculations found fields of distribution of the basic parameters in the air-gas channel of the small-sized combustion engine, such as pressure, temperature, speed and composition of the working body. According to the simulation results power and fuel efficiency of the small-sized enginewere calculated.

Keywords:

ANSYS, boundary conditions, CAD/CAE-systems, combustion engine, combustion engine engineering, fluent, grid of finite-elements.