Turbulent mixing enhancement with a 20° chute mixer

Abstract

Turbulent mixing enhancement of two confined, co-axial jets having a low annular to core area ratio of 0.26 is achieved with the help of a 20° chute mixer. Detailed measurements were performed in the flowfield of a chute and contours of mean velocity and streamwise and transverse turbulence intensities were plotted to gain a deeper insight into the mixing enhancement process. The results from this work will aid in designing the mixer for low bypass turbofan engines. Mean velocity and turbulence intensity distributions were also obtained downstream of the chute mixer. Total and static pressure measurements were made to study the total pressure loss and the static pressure variation due to mixing. The high velocity annular stream was found to quickly diffuse after entering through the chutes and mix with the core stream due to higher levels of turbulence generated in the mixing region. A strong transverse turbulence component immediately downstream of the chute exit enhanced the mixing of the penetrating stream with the core flow. With the aid of the chute mixer, nearly complete mixing is achieved over a length of 2.2 duct radii, suggesting feasibility of shortening the length of the turbofan engine mixing duct by more than 50%. However, a higher total pressure loss of about 1.71% is the penalty to be paid for the enhanced mixing of jets.