Originally Posted by
Blackout
Gas turbine blades of conventional rotorcraft turboshaft engines are optimized to operate at nearly a fixed speed and a fixed incidence angle. If the operating condition of the engine changes, then the flow through the turbine may need to be guided to a more optimum direction.
One way to do this is with variable turbine nozzle geometry. But this standard method has some disadvantages including increased weight and complexity, as well as a limited operating range since the nozzle vanes can only be turned to a certain point before severe flow incidence angles disrupt the rotating blades downstream.
That appears to draw directly enough from
Murugan, Muthuvel; Ghoshal, Anindya; Bravo, Luis; Xu, Fei; Hsu, Ming-Chen; and Bazilevs, Yuri, "
Articulating Axial-Flow Turbomachinery Rotor Blade For Enabling Variable Speed Gas Turbine Engine"
(2018). Mechanical Engineering Conference Presentations, Papers, and Proceedings. 195. to require a citation, no?