Session: 01-02 Inlet Distortion and Engine Operability I
Paper Number: 151359
Impact of Endwall Clearances on Off-Design Performance of Boundary Layer Ingesting Variable Pitch Fans
Aircraft propulsion research in recent years, driven by challenging emission targets, has focused on hybrid-electric propulsion systems. One particular area of research revolves around electrically powered boundary layer ingesting (BLI) aft-fans. A conventional electrically powered BLI fan designed for cruise faces challenging flow conditions at low speed, low altitude operating points requiring it to be operated at lower power settings, thereby underutilizing the performance capabilities of the electric motor. This circumstance can be mitigated by incorporating rotor blades with variable pitch which provides the added benefit of improving the stability margin of the operating point. Variable pitch fans require the provision of some geometric allowances which act as a driver of secondary flows. The rotor tip section must be contoured such that the nominal tip clearance is maintained across the range of pitch variability, leading to non-uniform gaps to the casing. Additionally, hub gaps should be implemented to prevent intersections with the hub upon restaggering the rotor. The amount of material to be removed from the blade hub and tip is dependent on the range of pitch variability desired. This paper investigates, numerically using 3D single passage RANS, the impact of hub and tip gaps on the aerodynamic performance of electrically powered BLI fans with variable pitch at low speed, low altitude conditions. Two blade pitch variability ranges of 10° and 14° were considered, which corresponds to an increase in maximum tip gap at design stagger by 23.7% of the nominal clearance. Evaluating speedlines corresponding to the aerodynamic design point (ADP) revealed little impact of the increased tip gap on overall stage performance. The similar investigation conducted for the takeoff operating point at a rotor pitch setting of 10° resulted in an additional stability margin of 6.8% for the less variable blade.
Presenting Author: John Paul Panuthara German Aerospace Center (DLR)
Presenting Author Biography: I am working as a scientific researcher at the German Aerospace Center (DLR) in the Institute of Propulsion Technology since November 2023 before which I completed my MSc. degree in Aerospace Engineering from TU Munich. I am pursuing a PhD in conjuction with variable pitch fans focussing on endwall flows. I am active in the fields of fan aerodynamics, secondary flows and numerical simulations.
Authors:
John Paul Panuthara German Aerospace Center (DLR)Maximilian Mennicken German Aerospace Center (DLR)
Rainer Schnell German Aerospace Center (DLR)
Nick Gottschalk TU Braunschweig
Sandra Kleemann Oswald Elektromotoren GmbH
Thomas Reis Oswald Elektromotoren GmbH
Jens Friedrichs TU Braunschweig
Florian Herbst German Aerospace Center (DLR)
Impact of Endwall Clearances on Off-Design Performance of Boundary Layer Ingesting Variable Pitch Fans
Paper Type
Technical Paper Publication