3.1 Hovering Experiment of 16H-1
The experiment was performed on the ground. The experimental model was similar to the VTDP of the 16H-1. The slide and rear views are displayed in Fig. 10 and Fig. 11, respectively. The detailed model dimensions are listed in Table 1.
Component
|
Parameter
|
Value
|
Duct
|
Inlet diameter
|
644 mm
|
Outlet diameter
|
618 mm
|
Length
|
232 mm
|
Propeller
|
Number of blades
|
6
|
Diameter
|
593 mm
|
Hub diameter
|
75 mm
|
Airfoil
|
ARAD
|
Installed angle of blade tip
|
10°
|
Horizontal vane
|
Chord
|
92 mm
|
Span
|
602 mm
|
Airfoil
|
NACA 0012
|
Vertical vane
|
Chord
|
185 mm
|
Span
|
493 mm / 600 mm / 493 mm
|
Airfoil
|
NACA 0012
|
The model was set on an experiment table, which contained a six-component balance system connected to the model. An electric motor was connected to the propeller by a transmission shaft. The propeller was driven by the electric motor with a power rating of 100 kW. Because the hovering state was of interest, there was no free stream. While testing, the rotation speeds of the propeller and deflection angles of the vanes were under control. The axial and lateral forces were measured by a balance system. The power of the VTDP was calculated using the electrical current and voltage measurements, and the calibration was carried out before the experiment. The purpose of the experiments was to provide data to compare with the numerical simulations to verify their reliability. After the simulations were complete, a comparison with the experiments was performed.
3.2 Numerical Simulation of 16H-1
The numerical simulation was performed using ANSYS CFX. The Reynolds-averaged Navier–Stokes (RANS) equations were solved. The general connection interface model was Frozen-Rotor. The advection schemes were high resolution, and the turbulence scheme was a first-order upwind scheme. The turbulence model was the shear-stress transport (SST), and the dimensionless wall spacing y+ < 1 for all the walls.
3.3 Comparison Between Experiment and Numerical Simulation for 16H-1
For both the experiments and numerical simulations, the deflection angle Φ of the vertical vanes was fixed at 20°, and the deflection angle of the horizontal vanes was kept at 0°. The rotation speed of the propeller was adjusted. The comparisons of the axial force, lateral force, and power of the 16H-1 from the experiments and the numerical simulation are shown below.
Fig. 13 displays the comparison of the axial force for different rotation speeds. The results from the first and second experiments, which are, respectively, labeled as “Experiment 1” and “Experiment 2” in the legend, were similar. The calculated axial force was underestimated by less than 10%. However, the trend was similar to
that of the experiment.
Fig. 14 shows the comparison of the lateral forces for different rotation speeds. The lateral force was slightly overestimated. Nevertheless, the overall trend was the same.
Fig. 15 shows a comparison of the power for different rotation speeds. The power curves for the two experiments and numerical calculations coincided.
These comparisons demonstrated that the numerical simulation has the potential to be used to estimate the VTDP, at least for the axial force, lateral force, and input power. Based on the comparison, the proposed simulation method can be used to further explore the different VTDP configurations.
3.4 Further Numerical Results for 16H-1
In the simulations discussed in the previous section, the deflection angle of the vertical vanes was fixed. In the simulations discussed in this section, the rotation speed was fixed at n = 6500 rpm, and the deflection angles were varied.
Fig. 16 displays the axial force or thrust at different deflection angles. The hollow markers represent the total axial force for the VTDP of the 16H-1, and the solid markers represent the axial force components from the propeller, duct, and vertical vanes. With an increase in the deflection angle, the thrust of the propeller increased, the drag of vertical vanes increased, and the thrust of duct increased. As a result, the whole thrust of the VTDP system decreased monotonically.
Fig. 17 shows the lateral force at different deflection angles. The total lateral forces of the system and the vanes increased first and then decreased. The maximum forces occurred near Φ = 40°. The lateral force of the duct decreased with the increase in Φ.
Fig. 18 shows the power variations at different deflection angles. The maximum consumed power occurred at the same deflection angle as that of the maximum lateral force in Fig. 17.