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This paper analyses the shape of the air-fuel mixture in the latest version of an internal combustion engine (gasoline direct injection GDI). In this type of an engine there is an ultra-lean combustion mode where the fuel injection occurs at the compression stroke. An ignition occurs at an ultra-lean air-fuel ratio of 30 to 40 even 55 including exhaust gas recirculation. This mode of combustion of the stratified mixture decreases fuel consumption by around 35% and even 40% during idling. This gasoline engine becomes as efficient as a Diesel engine. The problem considered is the shaping of the air-fuel mixture in such an engine where the injector is situated at an angle to the axis of a curved piston. The analysis in this paper includes the following parameters: the diameter of the opening and the angle of the injector, the pressure of the injected fuel, the shape of the surface of the curved piston, the speed of the piston as a function of the crank angle, and dimensions of an engine.

The paper presents a mathematical model describing kinetic behaviour of the injected fuel stream in a Gasoline Direct Injection Engine. Mathematical analysis of the stream aims at calculating the time length the stream requires to reach the piston, rebound from it, and reach the electrodes of the spark plug. The results of the performed analysis were given in following parts of this paper.

This work conducts an analysis of the advantages coming from application of the constant depression carburettor with a fuel feeder. The fuel feeder enables an automatic change of the dynamic characteristic to the economic characteristic of the carburettor. The computer analysis of the characteristic of the constant depression carburettor was conducted based on a mathematical model. The comparison was made between the prototype of the constant depression carburettor and a standard one. The greatest advantages are for the partial loads of an engine. The fuel consumption was decreased by about 18% comparing to the standard carburettor. The additional advantage of a constant depression carburettor is the automatic change of its economic characteristic to dynamic one during the work of an engine.

The work presents a description of a characteristic of a carburettor of a standard internal combustion engine as a function of an angle of rotation of a crankshaft. Included in the analysis were the changes of pressure and velocity of the inlet flow in the intake system. Also included in the computer simulation model were: ambient parameters geometric dimensions of a carburettor and the intake system inlet losses in the intake system geometric parameters of a cylinder, crankshaft, connecting rod and piston outflow of fuel from a jet to a throat of a carburettor We developed an algorithm and modelling program of the process of creation of a mixture in the carburettor. Through a series of experiments we determined the air-flow coefficient at a carburettor throat and a outflow coefficient of fuel from the main jet of a carburettor. Then we used those parameters to model the characteristic of a carburettor.