BLADE PLANFORM OPTIMIZATION FOR A DUAL SPEED ROTOR CONCEPT

摘要

The paper illustrates the results of a multi-objective optimization activity performed on the blade planform shape of a medium-size helicopter in order to maximize the beneficial effects of a dual speed rotor technology and to provide a new baseline configuration for the possible application of active devices for the further improvements of the rotor performance. The optimization is performed with the aim to minimize the average total power and the average OASPL for four different flight conditions: a cruise flight and a max-speed level flight at full rotor speed and a 14.3° climb and a 6° descent flight at 90%RPM rotor speed. Additional flight conditions are tested after the optimization in order to further verify the benefits of the optimization. The planform shape is optimized by modifying the sectional chord lengths, the local sweep angles and the local twist angles of selected design points within given constraints. The commercial aeromechanics code FlightLab and the in-house aeroacoustic module OptydB_FRN have been selected as the best compromise between accuracy of the results and moderate CPU requirements. These tools, along with a planform modeller are arranged in an optimization workflow that was built by using the commercial simulation framework toolkit Optimus~® by Noesis. A genetic algorithm is used for the optimization phase. The built-up optimization procedure and the application of the described computational tools, with their respective peculiarities, advantages and limitations, demonstrate to be effective at producing reasonable performance improvements. The combined effects of rotor speed reduction and planform optimization produce power reductions ranging from 3.52%, in hover flight, to 5.96%, in fly-over flight, and noise reductions ranging from 1.88dB, in fly-over flight, to 3.40dB, in descent flight.