Revisiting Froude’s Theory for Hovering Shrouded Rotor

Jardin, Thierry; Grondin, Gilles; Gressier, Jérémie; Huo, Chao; Doué, Nicolas; Barènes, Roger

doi:10.2514/1.j053507

Cited by 5 publications

(5 citation statements)

References 16 publications

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“…This allows the shroud to produce all or more than the whole shroud thrust, according to the theoretical studies. 13 A larger inlet radius, which corresponds to a larger low-pressure region, can hence produces more thrust under the same mass flow. However, the difference on two inlets is small when the divergent nozzle is used.…”

Section: Effects Of Two Key Shroud Geometric Parametersmentioning

confidence: 99%

“…In order to avoid the external influence on the tests, it should keep no obstruction at least 10 times the rotor diameter in the upstream and downstream main frame. The metal frame which supports two rotors and shroud was designed wider than the flow-tube absorbed into the shroud according to the theoretical analysis in Jardin et al, 13 so that the effect from the frame to the air flow is minimized and can hence be ignored. The propulsion model components including the shroud and double rotor are hanged by three mechanical swingarms, which are connected to three mechanical parallelogram constructions, respectively, at the top.…”

Section: Introductionmentioning

confidence: 99%

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

Huo

Liu

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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This paper aims to design a novel experimental platform with multiple testing possibilities on different individual performance parameters and different rotary propulsion systems. Three mechanic swingarms were constructed to separately and simultaneously test the rotor(s) and shroud, so that the interactions among different components can be involved. Based on it, measurements on the total thrust, torque, and power were conducted to evaluate the system global performance and the effects of key design parameters. The test results indicate that the performance parameters such as total thrust, torque, power, and power loading of the shrouded double rotor (SDR) are asymmetric between the current system and the one with switched rotational speed. Compared with free rotors, the shroud presence can increase the total thrust by 61.2% and power loading by 60%; the combination of divergent nozzle and, relatively, great inlet can improve the system performance, but it is limited by the flow separation; the system behaves insensitively to the rotor locations and rotor number. The location at the upstream cylindrical section is recommended; the optimal performance usually occurs under the condition of the upstream rotational speed lower than the downstream one. All revealed phenomena and the effectively designed test platform give the technique references for the shrouded system design and optimization.

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Section: Effects Of Two Key Shroud Geometric Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Huo

Liu

2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…However, at the geometric inlet, the flow accelerates near the leading edge due to the shroud lip curvature and therefore is not uniform. Different definitions of the inlet geometric parameters were discussed in Jardin et al, 13 which proposed a homokinetic normal inlet surface model to ensure the uniform flow features at the inlet boundary. Therefore, in this work, a semispherical geometry which is big enough with a radius of 2.5 times rotor radius Rr was introduced on the top of the shroud geometric inlet.…”

Section: Computational Field and Boundary Conditionsmentioning

confidence: 99%

“…11 However, operating in a low Reynolds number, such configuration still has many aerodynamic problems such as the transition from laminar flow to the turbulent flow at the inlet, which can aggravate the unsteady features of the flow. 12,13 Meanwhile, due to the configuration, the interactions among different components result in a very complex flow. Therefore, in order to reveal the potential aerodynamics and flow features, computations become necessary as a supplementary approach to current experiments.…”

Section: Introductionmentioning

confidence: 99%

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

Huo

Sun

2019

International Journal of Micro Air Vehicles

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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.

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“…Until recently the first two theories were more often employed in practical calculation. 14,15 This is primarily due to the mathematical complexity of the vortex theory. Most of today's propellers were designed depending on the principle of independence of blade elements.…”

Section: Modeling Framework Of the Aerodynamic Model Fundamentals Andmentioning

confidence: 99%

Aerodynamic model of propeller–wing interaction for distributed propeller aircraft concept

Bohari

Borlon

Bronz

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part G:

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The present investigation addresses two key issues in aerodynamic performance of a propeller–wing configuration, namely linear and nonlinear predictions with low-order numerical models. The developed aerodynamic model is targeted to be used in the preliminary aircraft design loop. First, the combination of selected propeller model, i.e. blade element theory with the wing model, i.e. lifting line theory and vortex lattice method is considered for linear aerodynamic model. Second, for the nonlinear prediction, a modified vortex lattice method is paired with the two-dimensional viscous effect of the airfoils to simplify and reduce the computational time. These models are implemented and validated with existing experimental data to predict the differences in lift and drag distribution. Overall, the predicted results show agreement with low percentage of error compared with the experimental data for various thrust coefficients and produced induced drag distribution that behaves as expected.

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Revisiting Froude’s Theory for Hovering Shrouded Rotor

Cited by 5 publications

References 16 publications

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

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

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

Aerodynamic model of propeller–wing interaction for distributed propeller aircraft concept

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