Manipulation of Large-Scale Vortical Structures and Mixing in a Coaxial Jet with Miniature Jet Actuators Toward Active Combustion Control

作者：Saiki Yu^*; Tanaka Shigehiro; Hattori Shunya; Nakura Kasumi; Ishino Yojiro

来源：Flow, Turbulence and Combustion, 2016, 97(4): 1127-1145.

DOI：10.1007/s10494-016-9771-0

• Coaxial jet flame
• Miniature jet actuator
• Active control
• Large-scale vortex
• Mixing
• Particle image velocimetry

Manipulation of large-scale vortical structures and associated mixing in a methane-air coaxial jet is carried out by using miniature jet actuators installed on the inner surface of the annular nozzle. The periodic radial miniature jet injections are achieved with a rapid-response servo-valve. The spatio-temporal primary jet structures are investigated through phase-locked 2C-PIV (2 Component Particle Image Velocimetry) and stereoscopic-PIV. It is found that intense ring-like vortices are produced perfectly in phase with the periodic miniature jet injections regardless of the valve-driven frequency f (v) examined. When the Strouhal number St(v), which is defined with f (v) , is larger than unity, the ring-like vortices are densely formed and thus methane/air mixing is prompted with low periodic fluctuation. The diameter of the vortices becomes small as St(v) is increased, so that the transport range of the inner methane and outer air fluids can be controlled by changing St(v). In addition, the evolution of counter-rotating vortex pair is also observed in the cross-sectional plane. These streamwise vortices are directly formed as a result of the radial miniature jet injection, which leads to entrainment of the ambient fluid near the primary jet shear layer, and they also contribute to the mixing enhancement. Moreover, it is demonstrated that coaxial jet flame characteristics such as carbon monoxide (CO) emission and flame holding can be drastically improved under different equivalence ratios by the present jet control scheme.

• 出版日期2016-12