Effect of Side Wall Expansion Angle on the Performance of a Dump Diffuser Model for a Combustor


Department of Mechanical Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah-711103, West Bengal, India


In the present article, numerical analysis has been performed on a dump diffuser model, to study the effect of sidewall expansion angle (SWA), on its performance aspects. SWA has been varied from 90° to 1° and performance has been evaluated in terms of major influencing aspects. It is observed that, at SWA of magnitudes greater than 11°, there is no significant change in the performance. But at SWA below 11°, significant changes, which enhance the performance are observed. It is noticed that at SWA in range, from 3.57° to 8°, higher static pressure recovery (almost from 25 to 33% of inlet dynamic pressure) happens in the dump and annular regions. SWA of magnitudes less than 11° have resulted in smaller, low dense and higher intense recirculation zones. At the SWA of 3.57°, static pressure recovered is maximum and total pressure lost is minimum. But that SWA causes too much delay in pressure stabilization on the liner wall. However, SWA of magnitudes less than 3.57° have resulted in comparatively poor performance. Eventually, sidewall angle in the range from 5° to 7° is found to be optimum as it yields higher static pressure recovery and low total pressure loss. This range also results in early stabilization of pressure both on the liner and casing walls.