Aerodynamic Characteristics of Helicopter with Ducted Fan Tail Rotor in Hover under Low-Speed Crosswind

Roh, Nahyeon; Oh, Se-Joon; Park, Donghun

doi:10.1155/2020/7059209

Cited by 11 publications

(9 citation statements)

References 19 publications

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“…The characterization of the MR wake using overset mesh technology is a time-consuming task due to the hole cutting process and data transfer between donor and acceptor cells at each time step [25,26]. The actuator disk approach has been used to perform successful rotor wake simulations in MR-fuselage [27,28], MR-TR [22], MR-tail boom [29], and MR-lateral rotor and wing [30,31] interaction calculations. Several researchers have demonstrated that one characteristic feature of the MR disc vortices wake is well-known coherent supervortices, as the blade tip vortices roll up in the downstream [32].…”

Section: Numerical Methodologymentioning

confidence: 99%

“…Given that the vertical fin has a limited lift in low flight speed conditions, the yaw stability could be mainly detected on the curve slope of the TR thrust versus the wind azimuth. The yaw stability characteristics that were detected with this scheme have been widely applied in previous wind tunnel [15] and numerical simulation [22,24] studies.…”

Section: Test Contentsmentioning

confidence: 99%

“…Although previous studies have characterized the TR performance associated with MR interference effects for various TR configurations restricted to a certain constant sideslip angle [16][17][18][19][20], literature on the yaw stability characteristic caused by the produced thrust of TR (i.e., the slope of TR thrust versus wind azimuth) in the presence of MR wake interference in a quartering wind region is limited. Studies [22,23] have examined the TR thrust variation in crosswind directions of 0°-360°at one fixed wind speed. However, the intervals of 30°wind azimuth applied in these studies are excessively large to derive the yaw stability detail and have limited the wind speed region.…”

Section: Introductionmentioning

confidence: 99%

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Main Rotor Wake Interference Effects on Tail Rotor Thrust in Crosswind

Wang

Huang

et al. 2021

International Journal of Aerospace Engineering

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Reverse pedal operational property in front crosswind flight condition is a potential hazard for accidents involving loss of tail rotor effectiveness (LTE), which is closely related to the main rotor (MR) wake interference on the tail rotor (TR). As understanding of this interaction is vital for the early warning strategy development, the MR wake influence effect on TR thrust and the effect of helicopter yaw stability are examined in this study. For this purpose, the comparison of TR thrust and flow field with wind azimuth and speed in front crosswind environment was performed by experiment and CFD simulation, respectively. Test campaign was performed at a 5.5 m × 4 m wind tunnel in the China Aerodynamics Research and Development Center using a high-position bottom-blade forward-rotating TR and a counterclockwise rotating MR to address the TR thrust under wind speeds of 8–22 m/s with 50°, 60°, and 70° wind azimuths. The influence of MR disc loading was also contrasted. CFD analysis was used to gain insight into the flow physics responsible for the interference effect. It was conducted with unsteady Reynolds-averaged Navier–Stokes simulations, where the MR using the actuator disk approach and the TR blade rotation was modeled via a sliding mesh method. Results indicated that the MR disc vortex has a remarkable interference effect on the TR aerodynamic performance characteristic and that the effect is sensitive to the wind speed, wind direction, and MR disc loading. The observed yaw instability is considered to be related to the lesser inflow introduced by the MR disc vortex due to the change in the relative position of the disc vortex filament and TR with the wind azimuth. The increase in TR thrust at moderate wind speeds is due to the increase in leading edge dynamic pressure caused by the opposite swirl direction of the disc vortex contrasted to the TR. The MR disc loading affects the TR thrust due to the change of disc vortex strength and position.

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Section: Numerical Methodologymentioning

confidence: 99%

Section: Test Contentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Main Rotor Wake Interference Effects on Tail Rotor Thrust in Crosswind

Wang

Huang

et al. 2021

International Journal of Aerospace Engineering

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“…They adopted CFD to calculate the flow field and tail rotor performance for both hover and lateral flight conditions. Many researchers are interested in the flow field and the location of the vortex core under different flight conditions [16][17][18]. The prediction method is the key factor for ducted rotor noise analysis.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic and Aeroacoustic Performance of Tail Rotor Investigation and Modification

Hao¹,

Jia²

2021

Preprint

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With the increasingly stringent airworthiness standards, the noise generated during the rotorcraft flight is gradually attracting people’s attention. It widely operated helicopters at low altitudes because of their maneuverability. The way to reduce the noise caused by the complex airflow of the helicopter rotor system has progressively become a hot topic for researchers. Using a hybrid acoustic analysis method, this paper investigates the improvement of the noise and thrust of the helicopter’s tail rotor through the tail rotor structural parameters. For the basic model, the turbulence simulation is performed using an incompressible detached eddy simulation (DES) method, and the Lighthill acoustic analog equation is calculated using the finite element method (FEM). We verified the accuracy of the method through wind tunnel tests. We chose a series of structural parameters for sound simulation and fluid simulation calculations. The results indicate that the modified tail rotor noise reduced by 16.5 dBA and the total thrust increased by 19.9% from the prototype model. This work can enhance the duct tail rotor design to improve aerodynamic and aeroacoustic performance.

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“…Considering the complex shafting structural designs of helicopters, any slight changes in the relative positions of shafting will lead to changes in the transmission characteristics of the entire transmission system, which will accelerate the wear of support bearings, shorten the service life of the bearings, and greatly impact the tooth surface friction at the gear meshing. As a result, vibration impacts will be produced which will negatively affect the performances of the transmission systems [11,12]. Due to the aforementioned tendencies, the transmission systems of helicopters may be subjected to additional excitation force, which will significantly reduce the working life of the transmission systems.…”

Section: Introductionsmentioning

confidence: 99%

An Analysis of the Gear Meshing Characteristics of the Main Planetary Gear Trains of Helicopters Undergoing Shafting Position Changes

Jiang

Dengrong

et al. 2021

International Journal of Aerospace Engineering

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The complex three-shaft three-reducer structural designs of helicopter transmission systems are prone to changes in the relative positions of shafting under the conditions of main rotor and tail rotor loads. These changes will affect the transmission characteristics of the entire transmission system. In this study, the planetary gear trains of helicopters were examined. Due to the fact that these structures are considered to be the most representative structures of the main reducers of helicopters, they were selected as the study objects for the purpose of examining the meshing characteristics of planetary gear trains when the relative positions of the shafting changed due to the position changes of the main rotor shafts under variable load conditions. It was found that by embedding the comprehensive time-varying meshing stiffness values of the main rotor shafts at different positions, a dynamic model of the relative position changes of the planetary gear trains could be established. Then, combined with the multibody dynamics software, the meshing characteristics of the sun gears, and the planetary gears, the planetary gears and the inner ring gears were simulated and analyzed under different inclinations and offsets of the shafting. The results obtained in this study revealed the following: (1) the average meshing force of the gears increased with the increases in the angle inclinations, and the meshing force between the sun gears and the planetary gears increased faster than the meshing force between the planetary gears and the inner ring gears. It was observed that during the changes in the shafting tilt positions, obvious side frequency signals had appeared around the peak of the meshing frequency in the spectrum. Then, with the continuous increases in the tilt position, the peak was gradually submerged; (2) the average meshing force of the gears increased with the increases in the offset, and the increasing trend of the meshing force between the sun gears and the planetary gears was similar to that observed between the planetary gears and the inner ring gears. It was found that when the shafting offset position changed, there were obvious first and second frequency doubling in the spectrum; (3) the mass center orbit radii of the sun gears increased with the increases in the shafting position changes, and the changes in the angular tilt position were found to have greater influencing effects on the mass center orbit radii of the sun gears than the changes in the offset positions. This study’s research findings will provide a theoretical basis for future operational status monitoring of the main transmission systems of helicopters and are of major significance for improvements in the operational stability of helicopter transmission systems, which will potentially ensure safe and efficient operations.

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Aerodynamic Characteristics of Helicopter with Ducted Fan Tail Rotor in Hover under Low-Speed Crosswind

Cited by 11 publications

References 19 publications

Main Rotor Wake Interference Effects on Tail Rotor Thrust in Crosswind

Main Rotor Wake Interference Effects on Tail Rotor Thrust in Crosswind

Aerodynamic and Aeroacoustic Performance of Tail Rotor Investigation and Modification

An Analysis of the Gear Meshing Characteristics of the Main Planetary Gear Trains of Helicopters Undergoing Shafting Position Changes

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