Influence of initial conditions at the nozzle exit on the structure of round jet

A study and comparison of the modes of diffusion combustion of hydrogen and methane at their outflow from the annular nozzle together with the flow of supplied air from the coaxially located circular nozzle

“…As the flow rate increases, a bottleneck is formed and the flame is divided into two zones: laminar and turbulent (Figure 3(b)). Near the nozzle exit, the laminar section acquires a spherical shape, the combustion scenarios are similar to those previously described in [4]. With a further increase in the outflow velocity, the turbulent flame descends closer to the nozzle exit (Figure 3(c)), and the laminar section of the flame decreases until it finally disappears, after which the separation of the turbulent flame from the nozzle exit is observed (Figure 3(d)).…”

“…A lot of theoretical and experimental works are devoted to the study of micro and macrojet flows. When outflowing from nozzles with micro diameters, some peculiarities are observed in the flow, for example, in [4,5] it is shown that the jet remains laminar at a much greater distance from the nozzle exit than in the case of macro diameters.…”

“…The main scenarios of diffusion combustion of hydrogen associated with the presence of a twozone flame structure in a wide range of flow rates or velocities of the microjet outflow are revealed. According to the results of [4] on hydrogen flowing out of circular nozzles with diameter d = 250-500 μm, depending on the flow velocity of the jet U0, the following combustion scenarios are observed:…”

On Helical Structures in a Round Turbulent Jet

“…Эти структуры участвуют в интенсивном перемеши-вании [4][5] и играют значительную роль в генерации акустического шума [6]. Динамика и характеристики когерентных вихревых структур в существенной степени зависят от начальных и граничных условий [7][8][9][10][11] и определяют асимптотические автомодельные состояния течения при больших временах эволюции и расстояниях от области формирования [12][13]. Глубокое понимание динамики и пространственной организации энергонесущих крупномасштабных вихревых структур необходимо для разработки и развития эффективных методов управления турбулентными потоками.…”

Stability of Subsonic Microjet Flows and Combustion

“…However, this mechanism still remains unclear. The experimental studies [6][7][8][9][10][11][12] and other, where the influence of the initial conditions at the nozzle exit and acoustics on the development of round and plane microjets in the absence of combustion at low Reynolds numbers were investigated in detail, which made it possible to understand and explain some phenomena in the flame behaviour observed during propane combustion in these jets. The results of these studies are presented in this paper.…”