Numerical simulation of ignition mixtures of methane and acetylene with air

The research object is the process of ignition in mixtures of methane and acetylene with air. The promoting effect of the addition of acetylene on the ignition of these mixtures has been demonstrated. The effect of the additive on the acceleration of ignition is noticeable; the tem-perature of the lower boundary of the region of rapid ignition of methane is found. The results of numerical simulation of chemical kinetics in the mixtures under consideration are presented, which make it possible to determine the conditions of non-ignition and ignition in methane-acetylene mixtures with air. In experiments carried out at the Research Institute of Mechanics of Moscow State University. For the given values of the methane concentration, the two clos-est values of the acetylene concentration were found. At a lower value, the mixture did not ig-nite, and at a higher value, it ignited. In the calculations, at a lower value of the acetylene con-centration, the non-ignition temperature was found, and at a higher value, the ignition temperature. Thus, numerical simulation made it possible to satisfactorily explain the experi-mental data.

combustible mixture, methane, acetylene, air, ignition

Volume 23, issue 2, 2022 year

Численное моделирование воспламенения смеси метана и ацетилена с воздухом

Объектом исследования является процесс воспламенения в смесях метана и ацетилена с воздухом. Продемонстрировано промотирующее влияние добавки ацетилена на воспла-менение этих смесей. Заметно влияние добавки на ускорение воспламенения, найдена температура нижней границы области быстрого воспламенения метана. Приведены ре-зультаты численного моделирования химической кинетики в рассматриваемых смесях, позволяющие определить условия невоспламенения и воспламенения в метано-ацетиленовых смесях с воздухом. Для заданных значений концентраций метана находи-лись два ближайших значения концентрации ацетилена. При меньшем значении смесь не воспламенялась, а при большем воспламенялась. В расчётах при меньшем значении концентрации ацетилена находилась температура невоспламенения, при большем - тем-пература воспламенения. Таким образом, численное моделирование позволило удовле-творительно объяснить экспериментальные данные.

горючая смесь, метан, ацетилен, воздух, воспламенение

Volume 23, issue 2, 2022 year

Shown here are the dependences of methane and acetylene at a methane concentration of 1%. The calculations were carried out up to the time tk = 20 s. As can be seen from the left figure, at a temperature of 1000 K, the curves for acetylene at a1 and a2 completely coincide. The curves for methane m1 and m2 coincide in most of the sweeps, but at a higher concentration of acetylene a2, at the very end of the sweep, the beginning of its rapid decay is visible. At lower temperatures, the agreement was complete for the methane curves as well. Therefore, the figure really reflects the state of non-ignition of the mixture.
As the temperature of the mixture rises by 25 K, the state of the mixture changes qualita-tively. As follows from the right figure, both curves for methane and acetylene demonstrate a sharp (almost vertical) drop in the concentrations of these components and a synchronous change in the m2, a2 and m1, a1 regimes at times of about 10 s. For temperatures above 1025 K, ignition occurs faster for both modes with a1 and a2. Thus, indeed, non-ignition can occur for the highest value of the non-ignition temperatures, and ignition - for the lowest value of the ignition tempera-tures.