Determining the Characteristics for the Rational Adjusting of an Fuel-air Mixture Composition in a Two-stroke Engine with Internal Carburation

An operating process for engines with spark ignition and direct fuel injection engines which ensures the formation of a stratified lean fuel-air charge under the modes of partial loads and the power composition of the fuel-air mixture at high loads has been developed.The design of a two-stroke spark-ignition engine was modernized by installing a direct fuel injection system, placing the nozzle in the cylinder wall, and changing the combustion chamber shape.A procedure of adjustment of the composition of the fuel-air mixture in the cylinder of a two-stroke spark-ignition engine has been developed. The procedure features the recording of engine parameters and indicators at a constant cycle fuel feed and intake air adjustment. The proposed procedure makes it possible to more accurately adjust the composition of the fuel-air mixture due to a more accurate dosage of air than the cycle fuel feed.Experimental studies were carried out and adjustment characteristics were constructed in terms of the air-fuel mixture composition in the cylinder of a two-stroke engine with a developed operating process.Load characteristics (at n=3,000 rpm) of rational adjustment in terms of economy and maximum power were constructed based on data on the adjustment characteristics for the composition of the fuel-air mixture.It was found that in terms of the load characteristic of rational economy adjustment, the composition of the fuel-air mixture in the engine cylinder (λcyl.ec) varied from 1.31 to 1.94 and the minimum fuel consumption was ge min=259 g/(kWh). In terms of the load characteristic of rational power adjustment, the composition of the fuel-air mixture in the engine cylinder (λcyl.pow) varied from 1.31 to 1.7, and the fuel consumption at partial loads was ge=270 g/kWh.Characteristics of airflow rate depending on the cycle fuel feed can be used to change the composition of the fuel-air mixture with automatic adjustment of the engine loa

Development of A Three-zone Combustion Model for Stratified-charge Spark-ignition Engine

A thermodynamic model for calculating the operating process in the cylinder of a spark-ignition engine with internal mixture formation and stratified air-fuel charge based on the volume balance method was developed. The model takes into account the change in the working fluid volume during the piston movement in the cylinder. The equation of volume balance of internal mixture formation processes during direct fuel injection into the engine cylinder was compiled. The equation takes into account the adiabatic change in the volume of the stratified air-fuel charge, consisting of fuel-air mixture volume and air volume. From the heat balance equation, the change in the fuel-air mixture volume during gasoline evaporation in the fuel stream and from the surface of the fuel film due to external heat transfer was determined. Basic equations of combustion-expansion processes of the stratified air-fuel charge were derived, taking into account three zones corresponding to combustion products, fuel-air mixture and air volumes. The equation takes into account the change in the working fluid volume due to heat transfer and heat exchange between the zones and the walls of the above-piston volume. Dependences for determining the temperature in the three considered zones and pressure in the cylinder were obtained. Graphs of changes in the volumes of the combustion products, fuel-air mixture and air zones with the change of the above-piston volume in partial load modes (n=3,000 rpm) were plotted. With increasing load from bmep=0.144 MPa to bmep=0.322 MPa, at the moment of fuel ignition, the volume of the fuel-air mixture increases from 70 % to 92 % of the above-piston volume. At the same time, the air volume decreases from 30 % to 8 %. Analysis of theoretical and experimental indicator diagrams showed that discrepancies in the maximum combustion pressure do not exceed 5