Analysis of swirling recirculating reacting turbulent jets passing through diffusers

The present mathematical analysis has been undertaken to study the effect of swirl strength, angle of diffuser, secondary mass flow, and combustion on the strength and size of the recirculation zone inside a diffuser. The flow is considered swirling, three dimensional, incompressible, turbulent, axisymmetric, and steady. Two nondimensional mass and swirl parameters are used for characterising the flow at the inlet to the diffuser. The strength of recirculation is represented in terms of a wake depth parameter, which exceeds unity when recirculation sets in. The axial velocity distribution is represented by a single family of curves, and the tangential velocity by solid body rotation. Turbulence is characterised by a wake Reynolds number, while the effect of combustion is simulated by considering axial density gradients. A momentum integral technique has been used for simplifying the governing partial differential equations. Increases in both swirl strength and diffuser angle lead to an increase in the strength and size of the recirculation zone. Secondary mass flow through the walls of the diffuser and combustion reduce the strength and size of the reversal zone. Consideration of the simultaneous influence of combustion and mass addition shows that it does not correspond to the addition of effects produced by them independently. © 1978.