Aerodynamic assessment of nozzle area variation by core fairing modulation

Sain, Chetan Kumar; Hoeschler, Klaus

doi:10.1007/s13272-017-0253-4

Cited by 3 publications

(1 citation statement)

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“…The variable-area nozzle has been so far mostly examined from the point of view of engine thermodynamic cycle, e.g., Giannakakis [2] and Kyritsis [9], its mechanical implementation with Sain [17], and fan aerodynamic performance by Kavvalos [7]. Kavvalos estimated that significant surge margin improvements by 20-25% can be realized with a nozzle opening by 20% from its nominal area (around 4-5% gain per 1% opening).…”

Section: State Of the Artmentioning

confidence: 99%

Acoustic preliminary design of a low-noise fan stage considering a variable-area nozzle and variable-pitch rotor blades

Moreau¹,

Schnell²,

Mennicken³

2023

CEAS Aeronaut J

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A low-noise low-pressure ultra-high-bypass-ratio fan stage to be implemented in the next generation of aircraft engines is described and evaluated acoustically with semi-empirical and analytical methods suited for preliminary design. As expected, good reduction potentials are observed for the jet noise and fan tonal noise components when the UHBR design is compared to current fans in service. However, concerns are identified for fan broadband noise, which are attributed to the off-design operation of the UHBR fan too close from its stability limit. By unloading the fan and thus reducing the size of the rotor wakes, the variable-area nozzle provides a substantial fan broadband noise reduction with a nozzle opened by around 15% from its design value. Alternatively, with the variable-pitch fan, closing the rotor blades by roughly 5° turns out to be an even more effective method to reduce fan noise, as the unloading mechanism is combined with a stronger tilting of the rotor wakes and a lower intra-stage flow Mach number. Opening the nozzle or closing the blades beyond the setting that provides the best fan efficiency is not recommended as the acoustic benefit progressively vanishes, whereas technical feasibility becomes more challenging. Finally, the presence of one of these systems may allow for the design of a low-solidity rotor, with a smaller contribution from the rotor wakes and thus a weaker fan noise emission.

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Section: State Of the Artmentioning

confidence: 99%