Influence of turbulence on transient premixed flame propagation inside closed vessels

Abstract

The explosion behaviour of CH,/air mixtures inside a closed 0.065 m3 spherical and a 1 m3 cylindrical vessel was investigated to determine the effect of turbulence on the structure and propagation rate of transient turbulent flames for different initial turbulence levels generated by 4 ventilators installed inside the equipment. Laser-Doppler and hot wire anemometry were used to measure the turbulent motion. It was found that fairly uniform turbulence could be achieved in the central zones of the vessels and that the RMS-values of flow velocity were proportional to the ventilator speed. The evaluation of burning velocity from the pressureltime records showed that, starting from an initial burning velocity which depends on the initial turbulence level, the flame accelerates as a result of pressure, temperature and turbulence effects. Maximum burning velocity coincides with the inflexion point of the pressureltime curve, and is followed by a rapid deceleration of the flame front. A linear relationship between burning velocity and measured RMS-velocity is recognized in the observed range of RMS-values.

Flammability limits in flowing ethene-air-nitrogen mixtures: An experimental study

“…Furthermore, flame propagation is more difficult through a fast flowing system because of the increased level of turbulence and therefore an increased heat transfer from the flame front to the unburnt gas, which may extinguish the flame. Lewis and Von Elbe (1961), Leuckel et al (1989), Chippett (1993) and Watanabe et al (1983) all come to the conclusion that the flammability limit is influenced by the degree of turbulence in the gas mixture. It has also been mentioned that flammability limits in reality differ from those found in laboratory experiments.…”