Aerodynamic testing of pulsed-jet actuation on a short-inlet UHBR engine nacelle

Abstract Innovative short-inlet nacelle designs and disruptive technologies are essential for minimizing the drag and weight penalties of high-bypass-ratio turbofan engines. Active flow control (AFC) can mitigate inlet separation under off-design conditions by using local air injection at the inlet lip. This work investigates wind tunnel testing of continuous and pulsed blowing on a generic short-inlet UHBR nacelle at high angles of incidence (AoIs). The model is designed as a flow-through nacelle and is tested at a free stream Mach number of 0.15. The Reynolds number associated with the nacelle length is $$2.4 \times 10^{6}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>2.4</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>6</mml:mn> </mml:msup> </mml:mrow> </mml:math> . Static pressure tabs on the model surface and a traversable total pressure rake serve to evaluate the performance of AFC. Both continuous and pulsed blowing could prevent inlet separation for AoIs of $$18^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>18</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> and $$22^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>22</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> , reducing spatial total pressure non-uniformity by up to 80%. Here, the AFC performance showed strong sensitivity to the jet velocity. A comparison of required momentum revealed that pulsed blowing consumes 20% less momentum input than continuous blowing for the same improvement level. For an AoI of $$26^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>26</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> , only continuous blowing at maximum momentum input could effectively mitigate inlet separation. This experimental study confirms the potential of AFC to improve inlet flow under off-design conditions.