Compra, almacenamiento y manipulación de materias primas

In this section, the hover performance of the TILTAERO blades is investigated. In the frame of TILTAERO, ADYN, and DART European projects, the TILTAERO blades were manufactured by the Netherlands Aerospace Centre (NLR), and tested in the 8×6m open test section of the DNW-LLF wind tunnel. The radius of the TILTAERO rotor was R = 1.48 m, and the reference chord of the blade, taken equal to the mean aerodynamic chord, was cref = 0.209 m. This leads to a high rotor solidity, along with the small aspect ratio blades. Unlike the XV-15 rectangular planform, the TILTAERO’s planform includes a swept-back tip, which is also tapered by 21.53%. The fact that the TILTAERO blade has a more modern tip-shape design that the XV-15 blade along with the recent wind tunnel campaign suggested it should be included here for further validation of the HMB method.

Table 12 summarises the employed conditions and the computations performed in heli- copter configuration. The tip Mach number was set to 0.63, and seven blade collective angles were considered. The Reynolds number, based on the reference blade chord and the tip speed

Vtip = 214.38 m/s, was 3.07· 106. All flow solutions were computed by solving the RANS

equations, coupled with Menter’s k-ω SST turbulence model [50]. The flow equations were integrated with the implicit dual-time stepping method of HMB, where 75,000 iterations were necessary to drop the residual by 6 orders of magnitude.

Table 12: Flow conditions for the TILTAERO tiltrotor blade.

Parameter Value

Blade-tip Mach number (Mtip) 0.63

Reynolds number (Re) 3.07· 106

Blade pitch angle (θ75) 5◦, 7◦, 9◦, 11◦

13◦, 15◦, 17◦

The predicted rotor figure of merit obtained with HMB3, is compared with experimental data from the DNW wind tunnel and simulations performed by Beaumier [11] with the elsA CFD solver (Figure 21). Momentum-based estimates of the figure of merit are also included, with and induced power factor kiof 1.2 and overall profile drag coefficient CD0of 0.01. At

low and medium thrust, elsA results show good agreement with the experimental data, while the FoM is slightly under-predicted by HMB3. At high thrust (CT/σ ≥ 0.11), however,

the drop of FoM is very well predicted by HMB3. The results in this section help quantify differences between high-fidelity methods due to differences in mesh sizes, turbulence modes, and numerical schemes employed.

F o M 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 DNW Wind Tunnel Momentum, =1.2 plus =0.01 CFD, elsA (Beaumier 2008) CFD, HMB3 C T/ k_i C_DO

Figure 21: Comparison of the predicted figure of merit by elsA [11] and HMB3 CFD solvers, with the available experimental data at the DNW wind tunnel [11].

5.0 CONCLUSIONS

This paper demonstrated the capability of HMB3 to accurately predict tiltrotor flows. The ERICA model, the full-scale XV-15 and TILTAERO tiltrotor blades were considered for val- idation. The main conclusions are:

• For the ERICA model, the overall effect of the blades on the fuselage was well captured. It was found that the fuselage pressure was easier to predict than rotor loads.

• The method was able to capture the performance in the different modes; hover and pro- peller.

• Good agreement was found for the TILTAERO loads, where the drop of FoM at high thrust was well predicted.

• Measurements of surface blade data for tiltrotor blades are needed.

Part II presents aerodynamic optimisation of tiltrotor blades with high-fidelity computa- tional fluid dynamics.

6.0 ACKNOWLEDGMENTS

The use of the cluster Chadwick of the University of Liverpool is gratefully acknowledged. Some results were obtained using the EPSRC funded ARCHIE-WeSt High Performance Com- puter (www.archie-west.ac.uk), EPSRC grant no. EP/K000586/1. Part of this work is

funded under the HiperTilt Project of the UK Technology Strategy Board (TSB) and Leonardo Helicopters under Contract Nr. 101370. The authors would like to acknowledge the use of the NICETRIP experimental data and model geometry.

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