Abstract
ABSTRACTThe objective of this work is to computationally investigate the impact of an incidence-tolerant rotor blade concept on gas turbine engine performance under off-design conditions. When a gas turbine operates at an off-design condition such as hover flight or takeoff, large-scale flow separation can occur around turbine blades, which causes performance degradation, excessive noise, and critical loss of operability. To alleviate this shortcoming, a novel concept which articulates the rotating turbine blades simultaneous with the stator vanes is explored. We use a finite-element-based moving-domain computational fluid dynamics (CFD) framework to model a single high-pressure turbine stage. The rotor speeds investigated range from 100% down to 50% of the designed condition of 44,700 rpm. This study explores the limits of rotor blade articulation angles and determines the maximal performance benefits in terms of turbine output power and adiabatic efficiency. The results show articulating rotor blades can achieve an efficiency gain of 10% at off-design conditions thereby providing critical leap-ahead design capabilities for the U.S. Army Future Vertical Lift (FVL) program.
Highlights
The development of a gas turbine engine is considered mature, the ever-higher power and efficiency requirements needed to advance today’s propulsion systems call for innovation [1,2,3]
The variable speed power turbine (VSPT) can be applicable to the U.S Army Future Vertical Lift (FVL) effort, where it would be deployed to overcome the challenges associated with off-design operations
We investigate the articulation of rotor blades within a single high-pressure turbine stage that features similar dimensions and operating conditions to engines found in rotorcraft like Apache and Blackhawk
Summary
The development of a gas turbine engine is considered mature, the ever-higher power and efficiency requirements needed to advance today’s propulsion systems call for innovation [1,2,3]. One promising development to address this call is the variable speed power turbine (VSPT), which would be able to meet the requested power and efficiency levels in a wider range of operating conditions. A VSPT would be able to alter its operating speed without facing the substantial performance losses that today’s engines experience at off-design conditions [1, 4]. The cause of performance losses at off-design operation stems from the aerodynamic flow separation around the turbine blades. The VSPT can be applicable to the U.S Army Future Vertical Lift (FVL) effort, where it would be deployed to overcome the challenges associated with off-design operations
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