Nitrogen oxide formation with nonuniform fuel distribution in diesel engine

Abstract

The high requirements for limiting the toxic components of exhaust gases of modern internal combustion engines require significant expenditures both for the improvement of existing engines and for the development and implementation of new types of engines. Some European organizations are raising the issue of limiting the use of diesel engines and even a possible cessation of their production in the next 5-10 years. This article reflects the results of studies on the formation of one of the most toxic components of exhaust gases - nitrogen oxides. The calculations were carried out according to the thermodynamic cycle model, which makes it possible to estimate the main characteristics of the operating cycle as the fuel-air charge burns out. Calculations are carried out with regards to a gas-diesel modification of an air-cooled engine with a dimension of 120 x 120 mm, which assumes the supply of the main gas-air charge through the inlet pipeline and a limited dose of diesel fuel injected into the cylinder to ignite the charge. The model shows the conditions for the burnout of the charge and the formation of nitrogen oxides in 10 equal in mass and successively burnout zones of the charge in the diesel cylinder. Calculations show that the formation of nitrogen oxides can be significantly reduced by 50 … 80% by adjusting the charge stratification scheme, that is, by changing the fuel concentration in the burnt-out portions, due to the mutual regulation of diesel and gas fuel supplies. The results of experimental verification of the calculations are presented below, which confirms the adequacy of the model. The effect in the total reduction of NOx emissions can be significantly improved by using partial charge throttling and using exhaust gas recirculation. The data obtained confirm the feasibility of further fine-tuning the working process of gas-diesel engine modifications and meeting the requirements of toxicity standards.