Horizontal Tailplane-Tip Mounted Tractor Propeller Interaction Effects

Advanced propeller propulsion systems potentially provide a significant reduction in fuel burn compared to traditional turbofans. An alternative to the conventional aft-fuselage mounted pusher layout is the horizontal tailplane-tip mounted tractor propeller concept. The aim of this thesis is an experimental investigation of the aeroacoustic and aerodynamic interaction effects of the tailplane-tip mounted tractor propeller configuration, including the effects of elevator deflections. The experimental study was conducted at TU Delft’s Low Speed Laboratory in the Vertical Tunnel and the Low Turbulence Tunnel with two different models. From the aeroacoustic study, it was concluded that the installation of the pylon behind the propeller affects both the directivity and the tonal levels of the propeller noise field, with the broadband acoustic levels remaining unchanged. It was determined that the overall sound pressure level (SPL) across the range of directivity angles considered is inversely proportional to the propeller-pylon spacing. For a spacing of 50% propeller diameter, the overall SPL was comparable to the case of the isolated propeller. A unique characteristic of installation of the pylon was the development of a trough in the directivity for an observer position in the pylon plane caused by the cancelling of the steady noise field by unsteady blade loading noise. This arises due to inflow distortion due to potential effects caused by the pylon. This unsteady blade loading is a function of the propeller-pylon spacing, and hence the levels in the trough decrease with decreasing propeller-pylon spacing. For directivity angels in the pylon plane, for spacing below 30% of the propeller diameter, the unsteady loading is further influenced by the elevator deflection and was the main mechanism of the interaction noise. For propeller-pylon spacing’s above 30% of the propeller diameter, the interaction of the slipstream (either the propeller noise field, or the slipstream impingement) with the elevator was determined to be the main interaction mechanism. From the PIV and performance evaluations, it was concluded that for the given propeller-pylon spacing (43% and 85% propeller diameter), there was indeed negligible upstream interaction effect due to the trailing pylon, including the case of the deflected elevator Pylon loads obtained from an external balance showed that for symmetric inflow conditions, operation of the thrusting propeller increased elevator effectiveness by 20% compared to the case with no propeller present. A numerical simulation using XROTOR was used for the validation of the test data and had a relative error of 3% with the experimentally evaluated propeller thrust for the lowest advance ratio. A slipstream propagation model based on the computed propeller induced velocities showed acceptable trends when compared to the experimentally determined induced propeller velocity profiles. However, the numerical model overpredicts the velocity profile in the tip region, owing to the tool’s limitation in predicting stall at the blade tip. A VLM based numerical analysis which included the effects of the propeller slipstream, was able to predict the pylon lift to within 3% of the lift computed from the surface pressure measurements, but failed in the prediction of the drag of the model.

Subject

propeller
propulsion integration
vortex interactions
aeroacoustics

To reference this document use:

http://resolver.tudelft.nl/uuid:e7e16208-8b9a-457e-9bdc-87e65e4c9135

Part of collection

Student theses

Document type

master thesis

Rights

Files

PDF

AshwinCandade_MSc_Thesis_Report.pdf

49.52 MB

Close viewer