The authors showed that the European Union norms for the toxicity of exhaust gases (Euro 1 – Euro 5) contributed to the reduction of main harmful components emissions by several times. In foreign countries, Stage and Tier regulations applied to tractor equipment, which also limited the content of toxic components at the legislative level.(Research purpose) To reduce the content of nitrogen oxides in exhaust gases by more efficient regulation of the fuel charge distribution in the gas-diesel engine cylinder, changes in the concentration of diesel and gas fuel in certain zones, as well as the use of exhaust gas recirculation.(Materials and methods) The authors analyzed the results of modeling the formation of nitrogen oxides by controlling the workflow in the gas-diesel modification of the diesel engine. In the calculations, the geometric parameters of the D-120 engine, operating at 2000 revolutions per minute, with a filling of 0.6-0.9 volume, were used. The average excess air ratio for the charge was 1.2-3.0, and the excess air ratios for the gas-air mixtures did not exceed 1.2-2.5.(Results and discussion) Using the computational model, the authors estimated the parameters at different pressures at the engine inlet within 0.05-0.09 megapascals, as well as with an increase in the residual gas coefficient in the range of 5-15 percent with a decrease in the concentration of nitrogen oxides from 2500 to 1100 parts per million. Experiments showed that when the power changed from 100 to 20 percent, the nitrogen oxides concentration decreased from 1940 to 800 parts per million.(Conclusions) The authors confirmed the adequacy of the calculation model. They determined that a 40-50 percent reduction in the nitrogen oxide concentration in exhaust gases was achieved with various layering schemes in the combustion chamber. They found that the standards for carbon monoxide, hydrocarbons and nitrogen oxides would require mixed engine regulation. It was proved that recirculation of 15 percent of exhaust gases could reduce nitrogen oxide emissions by another 50 percent.
