Optimizing the Aerodynamics of Bluff Bodies Applying the Adjoint Method

Abstract

Nowadays, afterburner is considered a fundamental component of aircraft turbine engines, which results in increased engine thrust. Flame stability is an essential condition for proper functioning of the afterburner. Given that the afterburner activation leads to increased fuel consumption and a rise in aircraft temperature, its usage is limited to brief and specific periods such as during aircraft takeoff, specialized maneuvers, and instances requiring maximum aircraft speed. The engine's performance can be divided into two modes: with afterburner on and off. The presence of bluff bodies ensures flame stability in afterburner-on mode, whereas in afterburner-off mode, bluff bodies contribute to increased pressure loss. Optimizing the geometry of bluff bodies can reduce drag and consequently decrease pressure loss in afterburner-off mode. The adjoint method based on gradient optimization method has garnered increased focus due to its remarkable efficiency in determining the sensitivity of objective with respect to geometric parameters. In this study, the geometry of a bluff body in afterburner unit of a turbine engine is optimized to reduce drag. Initially, to validate the simulation, the bluff body is simulated in both afterburner-on and off modes, ensuring the reliability of simulation method. Subsequently, bluff body’s geometry is optimized to reduce drag. produced drag by flame holder and recirculation zones behind it are evaluated as two important factors in assessing the performance of flame holder in both reacting and non-reacting modes. The results indicate that in the optimized geometry, drag is reduced by 27%, and combustion efficiency is increased by nearly 3%.