TURBULENCE MEASUREMENTS AND OBSERVATIONS OF TURBULENT PREMIXED FLAMESAT ELEVATED PRESSURES UP TO 3.0 MPA

In order to explore the characteristics of turbulence and turbulent pr emised flames in a high-pressure environment, a nozzle-type burner wit h a turbulence generator was installed in a high-pressure chamber. Tur bulence measurements and combustion experiments were conducted with th e chamber pressure up to 3.0 MPa. Methane-air mixtures were used for t he combustion experiments and confirmed that the turbulent premixed fl ames were successfully stabilized. Flame observations were made using instantaneous Schlieren photographs and high-speed laser tomography. T urbulence measurements were conducted using a hot-wire anemometer inst alled in the high-pressure chamber. It was found that the scales of tu rbulence generated by perforated plates at elevated pressure are small er than those at atmospheric pressure. From flame observations, the fo llowing features of the flames at elevated pressure were found: (1) wr inkled structures of the flames become very fine and complex, and the cusps become sharp as pressure rises; (2) the flamelet breaks at many points of the flames and the scales of broken flamelets become small; (3) small-scale parts of the flame front convex to the unburned mixtur e frequently occur and move quickly to the unburned side. The effects of ambient pressure on turbulence characteristics and possible mechani sms which produce the wrinkled structure of the fine scales and genera te flame front disturbances in the high-pressure environment are discu ssed. Copy-right (C) 1997 by The Combustion Institute