Reduced pressure drop in the air inlet of a cruise missile using adjoint optimization

The air inlet is one of the main components of propulsion systems, whose main task is to supply the required airflow uniformly.This study aims to optimize an S-type inlet used in cruise missiles. The adjoint optimization tools available in fluent software are used for this purpose. In the first step, the method has been validated experimentally. The recovered pressure for the present study is 0.96 %, which has a good agreement with the results from the empirical method In the following, numerical modeling of the airflow is performed in the existing S-shaped duct. Then, using the numerical solution of the adjoint equations, the sensitivity of the cost function to the deformation of duct walls is calculated. According to geometric constraints, the purpose of optimization is to achieve a geometry that can minimize the total pressure drop by minimum geometry changes and provide the required mass flow rates. In the present work, by removing the flow separation region due to adjoint optimization, the total pressure drop has been reduced from 4.6 to 3 percent, and the mass flow rate has increased from 5.1 to 6.5 kg/s.