Computational study on the aerodynamics of a long-shrouded contra-rotating rotor in hover

Abstract

This paper aims to investigate the aerodynamics including the global performance and flow characteristics of a longshrouded contra-rotating rotor by developing a full 3D RANS computation. Through validations by current experiments on the same shrouded contra-rotating rotor, the computation using sliding mesh method and the computational zone with an extended nozzle downstream flow field effectively works; the time-averaged solution of the unsteady computation reveals that more uniform flow presents after the downstream rotor, which implies that the rear rotor rotating at opposite direction greatly compensates and reduces the wake; the unsteady computations further explore the flow field throughout the whole system, along the span and around blade tips. Complex flow patterns including the vortices and their interactions are indicated around the blade roots and tips. For further identifying rotor configurations, the rotorrotor distance and switching two rotor speeds were studied. The computation reveals that setting the second rotor backwards decreases the wake scale but increases its intensity in the downstream nozzle zone. However, for the effect of switching speeds, computations cannot precisely solve the flow when the rear rotor under the windmill because of the upstream rotor rotating much faster than the other one. All the phenomena from computations well implement the experimental observations.

Performance evaluations of a shrouded contra-rotating rotor based on a novel-designed platform with multiple testing possibilities

“…All the experiments aimed to explore the global characteristics of the shrouded system compared with free rotors and finally to provide the design criteria to guide the design of the SDR. According to the 2D numerical simulation results and preliminary experimental explorations made by the author, 22 the shroud which has inlet K i equal to 1.7 and outlet K e equal to 1.23 was chosen. All the experiments were made in hover status.…”

“…Here, IRD 40 mm is the best performed locations for free rotors according to the previous studies. [22][23][24] It was hence chosen for comparison with shrouded system which has the best IRD 20.…”

Adaptive Variable-speed Control for Enhancing the Performance of a Mine Counter-rotating Fan System

“…Some studies showed that adaptively changing the load distribution by adjusting the impeller velocity of the rotor may effectively and optimally enhance the overall performance for all flow conditions. (29)(30)(31) Most of the previous studies on enhancing the performance of an MCRF system focused on passively adjusting suitable parameters to fit specific surging or designed working conditions. These methods have various limitations and fail under other undesigned working conditions.…”

Characterization of ducted contra-rotating propeller propulsions

“…The contra-rotating rotor system of 188 mm diameter with a relatively long shroud of the length of 1.17 rotor diameter was investigated by Huo et al 8 The static pressure distribution on the inner surface of the duct was measured and found to be lower in front of the upstream rotor in comparison with the open rotor. A suction peak on the leading edge of the duct contributes in a significant way into the increase in thrust of the ducted system.…”

“…Using ducted propellers in multicopter design implies a minimum shroud length for a given propeller diameter. Majority of studies of effects of shroud design parameters on the propulsive effectiveness were conducted for relatively long ducts (0.8-1.4 the propeller diameter [1][2][3][4][5]8 ). Both single propeller and two coaxial propeller systems were investigated, whereas studies on contra-rotating systems with very short ducts (of 0.17 the propeller diameter 6,7 ) showed only minor improvements in the propulsion performance.…”