An investigation of empirical formulation and design optimisation of co-flow fluidic thrust vectoring nozzles

摘要

The purpose of this paper is to design and develop an advanced co-flow fluidic nozzle, based on the Coanda effect concept, for multi-directional thrust vectoring of small jet engines. Recent progress on finding an optimal geometry with a fixed momentum ratio to achieve maximum thrust deflection angle is discussed here. The efficiency of the system is found to be a weakly nonlinear function of the secondary to primary flow momentum as well as three geometric parameters. A useful empirical formulation is derived for thrust vectoring angle, based on a series of tests carried out on different nozzles. An accurate computational fluid dynamics model is also developed and evaluated against the experimental data. Moreover, quasi-Newton optimisation algorithm is employed to find an optimal geometry with a constant relative jet momentum and a constant secondary slot size. In this technique, the optimal wall geometric parameters are calculated in the direction of the steepest gradient with the help of the numerical simulation model in every iteration step. Additionally, an optimised fluidic nozzle is constructed to experimentally verify the numerical results and the empirical equation.