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This study presents nozzle and cowl shape optimizations for turbofan separate-jet engines. The main objective of this work is to implement an optimization process including a detailed Computer-Aided Design (CAD) model and improve nozzles propulsive performance, taking into account the complete geometry of the aft-engine body. Integrating detailed CAD models in optimization workflows remains challenging, that is why an original approach is considered. This method uses expert knowledge to reduce dimensionality and enables to compute sensitivities with finite differences. The results illustrate the interest of this innovative industrial optimization approach for the design of turbofan nozzles.

Purpose This paper aims to describe the use of optimization approaches to increase the range of near-future howitzer ammunition. Design/methodology/approach The performance of a gliding projectile concept is assessed using an aeroballistic workflow, comprising aerodynamic characterization and flight trajectory computation. First, a single-objective optimization is run with genetic algorithms to find the maximal attainable range for this type of projectile. Then, a multi-objective formulation of the problem is proposed to consider the compromise between range and time of flight. Finally, the aerodynamic model used for the gliding ammunition is evaluated, in comparison with direct computational fluid dynamics (CFD) computations. Findings Applying single-objective range maximization results in a great improvement of the reachable distance of the projectile, at the expense of the flight duration. Therefore, a multi-objective optimization is implemented in a second time, to search sets of parameters resulting in an optimal compromise between fire range and flight time. The resulting Pareto front can be directly interpreted and has the advantage of being useful for tactical decisions. Research limitations/implications The main limitation of the work concerns the aerodynamic model of the gliding ammunition, which was initially proposed as an alternative to reduce significantly the computational cost of aerodynamic characterization and enable optimizations. When compared with direct CFD computations, this method appears to induce an overestimation of the range. This suggests future evolution to improve the accuracy of this approach. Originality/value To the best of the authors’ knowledge, this paper presents an original ammunition concept for howitzers, aiming at extending the range of fire by using lifting surfaces and guidance. In addition, optimization techniques are used to improve the range of such projectile configuration.