The present work focuses on the fast prediction of the interaction noise (IN) components of a Contra Rotating Open Rotor (CROR) engine at take-off. The flow field past the CROR is computed using a steady RANS approach coupled with the concept of mixing plane between the rotors to remove the flow unsteadiness due to the propeller interaction. The effects of such interaction are then recovered applying the analytical model of Jaron et al. (2014), balanced with data extracted from the RANS solution, to extrapolate the information about the wake of the front rotor and the potential flow fields through the mixing plane. This RANS-informed approximation allows recovering the unsteadiness of the flow-blades interaction in terms of unsteady blade response. The tonal noise at the blade passing frequency and the interaction noise are then estimated using the analytical frequency domain model proposed by Hanson (1985). The present method for the fast prediction of CROR noise has been validated by comparison with the results of URANS simulations and noise measurements. CROR geometry UDF F7/A7 with both 8 × 8 and 11 × 9 blade counts has been considered. The flow velocity profiles extrapolated through the mixing plane agree well with the URANS results, except in the vicinity of the blade tip, where the analytical extrapolation method is not able to deal properly with the strongly 3D tip vortex flow. The comparison of the predicted interaction noise with acoustic measurements shows that the present fast RANS-informed approach is capable of estimating the directivity of the CROR noise with reasonable accuracy.
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<div class="section abstract"><div class="htmlview paragraph">This paper focuses on the design of the thermoelectric ice protection system (IPS) for the engine air intake of the Next Generation Civil Tiltrotor (NGCTR), a demonstrator under development in Leonardo Helicopters. A specific IPS design strategy for the novel intake configuration is proposed. The main constraint which driven the design strategy is a maximum power of 10.6 kW available for the full intake IPS system. The IPS was designed for safe aircraft operations within the Appendix-C icing envelope. The numerical approach adopted to perform the design and the resulting IPS concept are presented. Calculations of the required IPS heat fluxes revealed that maintaining running wet conditions on the entire intake surface is not feasible due to the limitation to the maximum IPS power demand. Therefore, a de-icing IPS design strategy is proposed. The anti-icing mode is adopted only on the lip region to avoid formation of ice caps whereas de-icing zones are defined within the intake duct. The de-icing zones cover the main impingement areas, and their splitting and power densities were designed to keep the instantaneous IPS power below the specified limit. The performances of the proposed IPS design were evaluated by means of ice accretion simulations. The effects of runback water were considered, and the de-icing effects were modelled by assuming that ice is perfectly shed by the de-icing zones. Computations of the residual ice accreted on the unprotected intake area demonstrated that the IPS drastically reduce the ice accretion and effectively protect the NGCTR engine air intake.</div></div>
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