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A confined oblique flame anchored on a bluff object was considered in a homogeneous propane/air mixture. A laser velocimeter employing a unique single-particle processor was used to quantify the turbulence velocity as well as spectrum. The results with combustion presented a striking contrast to the corresponding cold flow data. A major conclusion of the work is that the apparent suppression of turbulence observed in the separated combustion flow may be attributed to the significant dilatation effect by heat release in sheared flow regions. No vortex shedding was detected, and the negative production zone of turbulence energy was not observed. The turbulence structure was significantly distorted at the visible flame location.

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The aerodynamic characteristics of separated, recirculating flows behind a two-dimensional nozzle and bluff-body combination, which modeled a lean mixture combustor, was explored by a series of cold flow tests. The detailed distributions of mean velocities, static pressures, turbulent characteristics, and the tracer gas steady-state concentration were obtained. The flow velocity observations were successfully obtained by use of a laser velocimeter, whose data reduction system was devised particularly for use in highly turbulent flow measurements. Overall features of the mean field data revealed that the nozzle blowing diminished the longitudinal extent of the recirculation zone and substantially affected the mixing of tracer gas with the surrounding airflow. The Reynolds stress data imply that a zone of opposing shear was formed near the region of coexistence between negative and positive mean axial-velocities.

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