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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.

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.

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.

In this article possibilities of fuel injection control in two-stroke engines are presented. This is a low cost in-cylinder fuel injection system for stratified charge engines according to idea of Professor Stanislaw Jarnuszkiewicz with modified system of gases movement organization, that is much simpler than alternatives. The authors modified this pneumatic fuel injection system by means of hot exhaust gases drawn from one cylinder during the working stroke and, following the addition of fuel, forced into another cylinder during the compression stroke. Spraying and injection of fuel by means of hot exhaust gases give additional possibilities of complete evaporation of light fuels, alternative fuels with extended fraction and heavier fuels, such as diesel oil, kerosene and vegetable oil.

The paper concerns to the filling efficiency in spark ignition two-stroke engines of small power with loop-scavenged system. Amount of lost fresh charge to exhaust system has been presented. By changing of geometrical dimensions of transfer and exhaust ports scavenge efficiency, delivery ratio and exhaust loss of fresh charge can be changed. Full analysis of mass flow rate of air-fuel mixture and exhaust gases was conducted. Comparison of velocity vectors in an opened cylinder by means of finite element method in a CFD-program and during measurement is shown in graphs. There was obtained a big conformity of results from experimental research and calculation, which allowed carrying out the spatial analysis of fresh charge distribution in the cylinder in dependence on shape of combustion chamber. Principally geometry of ports and combustion chamber influence on emission of unburned hydrocarbons in exhaust system.

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.

In modern two-stroke SI engine applying one or two segments of catalytic converter in exhaust system is needed to fulfil requirements of emission of toxic components in burnt gases. In the paper dependence of location of catalytic converter with defined mass flow rate and resistance inside outflow system on engine performance, especially power and fuel consumption is described. Paper gives mathematical model of gas flow in a ‘tuned’ exhaust system with taking into account resistant of gas flow through catalytic converter. On the base of mathematical model calculation of physical parameter of gas for different location of monolith were done with overall engine output parameters. This enables optimisation of whole exhaust system at conservation of high temperature in the monolith. In the paper result of simulation (torque, fuel consumption, residual gas etc.) were given in comparison to original engine.

The article presents the possibilities of improvements the crankcase delivery ratio in small two-stroke engines by modification of the inlet system by means of an additional side volume connected with the inlet pipe. The results of calculations from numerical simulation of gas physical parameters, taking into account thermodynamic phenomena in the inlet system and crankcase, are closed to those obtained during experiments. Influence of different geometrical parameters of the inlet system on the crankcase delivery ratio is considered. The application of such system increases engine delivery ratio and improves air-fuel ratio over the whole range of engine speed, especially with part-throttle openings and higher engine rotational speed. Simulation and experimental variations of pressure and delivery ratio for various systems have been presented. Good correlation between theory and experiment makes possible a selection of this system at the early stage of design.

A new concept of mathematical model of gas flow through reed valve fitted to a small two stroke petrol engine with inlet port controled by piston was performed. Load and movement of reed petals, distribution of pressure and filling the crankcase by assumption of unsteady turbulent gas flow m an inlet pipe were determined in detail. The movement of a reed petal is solved by a more complete system of partial differential equations in forced vibration of plates. The results achieved from the simulation were verified by the experiments conducted on a real power-driven two stroke engine. The pressure measurement in an inlet duct and a crankcase helped to compare the computer simulation and tests results. The paper covers a theoretical model with mathematical equations system and their solution. It gives some diagrams of pressure, valve lift, velocity and delivery ratio obtained from calculations.