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Two-stroke opposed piston engines (2sOPEs) have great potential for industrial applications due to their simple design, technology and high efficiency, particularly with a turbocharging system. The paper presents possibilities for altering 2sOPE working parameters by changing geometrical parameters and boosting parameters. Obtaining higher engine efficiency is realised by altering the crank phase shift of the exhaust piston in relation to the transfer piston. It has been assumed that only the piston of the exhaust cylinder changes its position relative to the piston in the cylinder with transfer ports. Modifying the scavenging process by changing pistons’ position through connecting with two crankshafts enables asymmetrical scavenging timing. Closing the exhaust ports before the compression process and extending the time allotted to empty exhaust gases from the cylinder provides greater engine work, and a high boost ratio increases engine power.

The paper presents a modeling and simulation of the pneumatic injection process of a fuel mixture and exhaust gases in two-cylinder two-stroke SI engine. The fuel is injected to the small chamber between two cylinders which is connected with combustion chambers of both cylinders by duct and gas flow is controlled by a valve. The pneumatic injection system enables the reduction mostly of the hydrocarbons by controlling of the valve opening and fuelling phase. The paper presents the mathematical zero-dimensional model of the fuel evaporation in the mixing chamber and 1-dimensional model of the unsteady multi-phase charge between the cylinders. The mathematical model takes into account also the thermodynamic processes taking place in the cylinders. The paper performs the engine parameters for different engine configurations and calibrations obtained from simulation. This is the initial development step of such engine, which was designed and recently made and will be tested by the author.

Paper includes a description of a two-stroke engine with a rich mixture injection system. The injection of the fuel mixture follows from an additional chamber as a result of pressure difference between the chamber and the cylinder. Formation of the fuel mixture both in the chamber and in the cylinder is described by a simple mathematical model. The fuelling system of the engine was analysed both by use of zero-dimensional model and 3-dimensional model on the base of modified KIVA program. The results were compared with that obtained from the simple computer program based on given mathematical equations and experimental tests on real engines. A diagram of the fuelling system explains a principle of work and enclosed figures show variation of pressure and temperature in the chamber, vaporisation of fuel during crankshaft rotation and visualisation of the mixture injection to the cylinder at different engine speeds.

Recently in order to decrease of the exhaust emission and fuel consumption in the modern small SI two-stroke engines a direct fuel injection is applied or a rich fuel mixture is delivered directly to the cylinder. In order to increase the time required to vaporize all injected fuel and create a stratified charge with the rich mixture near the spark plug, a new concept of preparation and injection of the fuel mixture was analysed and tested. This paper includes a short description of the system shown in enclosed figures, the mathematical model of the charge exchange in the chamber and the cylinder and also the model of fuel vaporization in the chamber. The main aim of the paper was a comparison of the thermodynamic parameters especially the emission of CO, HC and CO2 obtained from experimental tests and from a simulation process in KIVA program for the standard carburetted engine and the engine with proposed system at some rotational speeds and control configurations.

Paper includes a description of the new system of rich mixture injection by applying of additional chamber and gas flow controlled by electronic valves. The system enables decreasing of hydrocarbons emission and specific fuel consumption. The paper includes mathematical model of exchange charge in the chamber and cylinder, injection process, simulation results of physical processes, which occur in the cylinder and chamber. A diagram of the fuelling system explains a principle of work and figures show variation of gas pressure, temperature and vaporization of fuel during crankshaft rotation. The system is designed for one-cylinder two-stroke engine, but can be applied also for multi-cylinder engines.

The paper gives a short description of a rich mixture injection system (RMIS) with an additional mixing chamber shown in the enclosed Fig. 26. A mathematical model of air-fuel charge exchange with vaporization of fuel in the chamber is presented. The paper includes the results of thermodynamic parameters in the cylinder and the chamber taken from measurements and calculations. The main work was carried out to determine the influence of control parameters of the pneumatic valves for two filling systems of the mixing chamber on CO, HC and CO2 emission. Calculations were done by using of a modified code of the KIVA3V program and a specially written computer program. The program was based on a zero- and one-dimensional model of engine work cycles, unsteady gas flows and emission of exhaust gas. The paper presents possibilities of toxic exhaust gas components reduction and decrease of fuel consumption in RMIS engine in comparison to the standard engine.