Abstract
ABSTRACTThe taper distribution along the span of a helicopter blade is defined using a novel method applied for the first time and considered as the main contribution of this work. This method uses cubic splines to generate modified blade shapes. The thrust and the torque values, computed by a 3-D Reynolds Average Navier Stokes solver, are used to train a Neural Networks based model. After that a constrained optimization is conducted based on this model for two different rotor speeds under hover condition. The optimization variables are the chord lengths at three different span locations: root, mid-span and tip. The optimization constraints are the torque or thrust values of the original blade and the practical limits for the chord lengths. Two optimum cases are investigated: maximum Figure of Merit with greater thrust and maximum Figure of Merit with less torque than the baseline. The major challenge of this work is to use the taper distribution as the only design parameter to obtain comparable results to other studies in literature in which more than one parameter is used. The results show that the Figure of Merit can improve by around 5% and the torque can be reduced by around 20%.
Highlights
One of the main challenging missions for the designers is to increase the helicopter rotor blade performance in hover condition
The performance of training is defined as the mean square error of the residual of Equation (4) and its convergence is shown in Figure 8 for the 1250 RPM rotor speed
The response surfaces of the figure of merit, thrust and torque values determined by using the trained Neural Netwroks (NN) model at 1250 and 1750 RPM speeds are given in Figures 9 and Increase in RPM Figure of Merit (FM) (%)
Summary
One of the main challenging missions for the designers is to increase the helicopter rotor blade performance in hover condition. The helicopter rotor flow is complicated due to vortical motions and instabilities. This means that more accurate analyses with high fidelity tools are required. Computational Fluid Dynamics (CFD) is a strong tool that is able to capture the complicated flow features of the helicopter flows. Renzoni et al (2000) have developed a three dimensional time-accurate Euler equations solver for overlapping structured grids to analyze the aerodynamics of rotor flow. Their method was successfully applied to different helicopter test cases
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