Multi-objective CFD-based design method for axial compressors

Sammanfattning: Economic aspects such as reducing specific fuel consumption and ever growing environmental requirements on emissions and perceived noise levels are the major incentives in the pursuit to improve aircraft engines. The overall efficiency of the engine is a combination of propulsive efficiency and thermal efficiency. A new, promising engine concept with very high propulsive efficiency is the so-called Open Rotor. In order to facilitate high thermal efficiency, the core of the engine must be designed with a high turbine inlet temperature as well as a high overall pressure ratio in combination with being light and compact. For the low-pressure compression system, the desire to reduce weight leads to a reduction of the number of stages. This must be realized by a combination of high transonic rotor speeds and high stage loadings in order to maintain the required pressure ratio. However, this becomes a tough design challenge aerodynamically as it will be more difficult to design the compressor with respect to high efficiency and sufficient stability along the entire operating line. This thesis presents a new design methodology, accounting for both efficiency and stability. The optimal set of solutions in the multi-objective space is explored with help of CFD computations integrated with an optimization framework that consists of a meta-model assisted genetic algorithm. In order to utilize the design process for industrial applications, the reductions in total design time and computational resources are also addressed. The validity of the analysis method developed is assessed by means of experimental data obtained from three transonic, highly loaded compressor cases including a rotor in isolation, a rotor-stator configuration and a three stage compressor.