Session: 01-04 Inlets, Ducts & BLI

Paper Number: 80894

80894 - Inlet Flow Distortion Dependencies for Tail Mounted Ducted Fans on Hybrid-Electric Commuter Aircraft 

The aviation sector has taken major leaps to increase the efficiency of aircraft and meet the global environmental goals in terms of emissions and noise. Towards this direction, the Boundary Layer Ingestion (BLI) concept is seen as a technology that may bring efficiency gains. On one hand, it allows for the re-energization of the low-momentum thin air flowing over the aircraft’s fuselage and, on the other hand, it can provide decoupled operation from the main wing engines and allow for use in specific mission segments. The latter holds true if combined with hybrid propulsion architectures and a suitable power management strategy.

A part of the aviation sector that is gradually gaining ground belongs to the short-haul commuter sector.  With this in mind, a preliminary analysis, using CFD, was carried out to investigate the influence of the fuselage transition and axial offset on the inlet distortion and performance of a tail mounted fan for a typical short-haul commuter aircraft.  For this study, the fan was modelled using a simple momentum source term based on a constant assumed pressure ratio of 1.2 across the fan.

For the configurations considered it was predicted that varying the angle of the fuselage transition did not have a significant impact on the radial distortion for a typical fan mounted at the centreline of the fuselage.  The wake behind the fuselage was predicted to increase in size as the slope of the fuselage was increased however the positive suction from the fan was sufficient for the flow to fully recover before the fan duct inlet.

Nevertheless, it was predicted that offsetting the fan from the fuselage centreline produced a much more significant increase in distortion in the circumferential direction.  The propulsive power of the fan was predicted to increase slightly with increasing offset mainly due to the side of the fan which was less obstructed by the fuselage.  However, the wake on the opposite side was predicted to increase significantly persisting almost to the inlet of the fan duct.  A vortex formed upstream of the fan which increased in strength with increasing offset.  This vortex helped a little to offset the increase in circumferential distortion by re-energizing the flow in the wake of the fuselage.  This caused the circumferential distortion to remain roughly constant between offsets of 25% and 50% of the fuselage radius.  It is likely though that this vortex will deteriorate the performance of the fan. 

Presenting Author: E. Geoffrey Engelbrecht Limmat Scientific AG

Presenting Author Biography: Ph.D. in premixed combustion modelling for gas turbine engines carried out under the supervision of Professor J.B. Moss at Cranfield University for Rolls-Royce Aeroengines.<br/><br/>More than 25 years of experience as an aerothermal engineer. 11 years working in the combustor department of ALSTOM&#39;s large gas turbine division. 5 of those years as the Principal Engineer for Aerodynamics/CFD. 14 years working as a consulting engineer supporting a wide variety of projects regarding gas turbine combustors, oil, gas, coal and biomass furnace burners, steam turbines, turbo expanders for heat pumps, condensers, hydro generators, etc.

Authors:

E. Geoffrey Engelbrecht Limmat Scientific AG
Vasilis G. Gkoutzamanis Aristotle University of Thessaloniki
Christos P. Nasoulis Aristotle University of Thessaloniki
Anestis I. Kalfas Aristotle University of Thessaloniki