Simulation of NOx emission

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Simulation is illustrated on the example:
The calculation of NOx emission in tractor diesel D-120 at a different values of compression ratio.

   At burning of sprayed liquid fuel in diesels, there are high local concentrations of active centres of chain reactions. These are atoms and free radicals arising in result of destructive transformations, oxidation and disintegration of hydrocarbons in vicinities of evaporating and burning drops. In these conditions the formation of harmful substances in diesels, such as soot, NOx, CO, differs by two main peculiarities. At first, the decisive role in this process plays not thermal, but chain acceleration of reactions at the expense of high local concentrations of active particles. Secondly, the processes of their formation are closely connected by a competition in the consumption of active particles and oxygen. The formation of NOx occurs through complex transformations of reactions products of fuel radicals with the nitrogen of air in before-burning and after-burning zones. The rate of these processes depends on the concentration of nitrogen in the volume of the cylinder, rate of combustion, share of the burned out fuel, and also on the rate of competing reactions of products of incomplete combustion, including CO and soot particles.

   On the basis of general laws of chain reactions, Professor N. F. Razleytsev developed an effective method of NOx emission calculation depending on the influencing factors. The comparison between the results of calculation of nitrogen oxides emission and specific fuel consumption on the one hand and experimental data on another hand is represented below. The simulation is carried out for different values of compression ratio of a tractor diesel D-120.

Comparision between calculated data and experimental ones

Heat release rate at  different values of   compression ratio e

NOx emission and   specific fuel consumption "be" as  functions of  compression ratio e.

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Visualization of mixture formation and combustion

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The experimental data are obtained by joint-stock company " VTZ "

rpm=2000;
Capacity=22 kW

The intensity of an air swirl in a combustion chamber at the TDC is characterized by swirl ratio H=3.

 

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