You are welkome , I will be happy if the info is of someone's help in generating some new ideas.
Since I spent one good portion of my life investigating bird's and insect's flight and this blade tips looks like gull wings I probably ( suppous) know how they work:) If they work as I suppouse they not only reduce the noise but also the induced drag which increase the efficiency as well. Probably this blade tips do not produce any lift but thrust because of the so called "Bell shaped lift distribution" ( instead of eleptical one as usually )where good part of the energy of the wing tip vortices is converted in thrust as on winglets on some modern planes wings. Planes with such twisted and bent wings ( to active bell shaped lift distribution) benefit also of proverse yaw effect ( instead of adverse yaw on the wings with eleptical lift distribution)so they no needs of verticall tail stabilizer/ rudder when you roll the plane it yaw naturally in the direction of rolling (not opposite as usually) that is why birds do not need any vertical tail surfaces as well.
The absence of vertical tail decrease the overal dragg and the weight of the plane so respectively increase efficiency .
Here is NASA research on the theme for who is interested in.https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003578.pdf
Briefly if you have such a blades tips you no need of duct !