Design Optimization of Dump Diffusers with NACA 66-021 Shaped Flame Tube

Abstract

Although the design and optimization of an aircraft engine have been advanced significantly over the last few decades, an aerodynamic shape optimization of dump diffuser is still an active research topic in the modern aircraft industry aiming for achieving more efficient combustion and the less total pressure losses. In our previous connected paper (AIAA 2019-4258) we reported that the dump diffuser facilitated by multiple-steps pre-diffuser cones, along with the aerodynamically-shaped adjustable flame tube that could improve the performance characteristics of aero gas turbine engines under a wide range of operating conditions. Herein, we attempted the aerodynamic design optimization of dump diffusers with NACA 66-021 shaped flame tube for improving the static pressure recovery. Numerical studies have been carried out using a validated 2D density-based steady viscous flow solver with the standard k-ε turbulence model. The code is verified and validated using the exact value of the boundary layer displacement thickness predicted at the Sanal flow choking condition. Parametric studies reveal that a dump diffuser with the NACA 66-021 airfoil-shaped flame tube has an improved static pressure recovery than the previously proposed NACA 0012 shaped flame tube. We observed that, in addition to the fluid dynamics and the geometric variables of a dump-diffuser, the thickness-to-chord ratio of the NACA airfoil-shaped flame tube is also having a bearing on the static pressure recovery. We concluded that the aerodynamics design optimization of dump diffusers with the NACA series airfoil-shaped flame tube is a meaningful objective for negating the large total pressure losses lucratively for an efficient combustion.