Contra-rotating System Research Articles

Psychoacoustic modelling of rotor noise.

The aviation sector is rapidly evolving with more electric propulsion systems and a variety of new technologies of vertical take-off and landing manned and unmanned aerial vehicles. Community noise impact is one of the main barriers for the wider adoption of these new vehicles. Within the framework of a perception-driven engineering approach, this paper investigates the relationship between sound quality and first order physical parameters in rotor systems to aid design. Three case studies are considered: (i) contra-rotating versus single rotor systems, (ii) varying blade diameter and thrust in both contra-rotating and single rotor systems, and (iii) varying rotor-rotor axial spacing in contra-rotating systems. The outcomes of a listening experiment, where participants assessed a series of sound stimuli with varying design parameters, allow a better understanding of the annoyance induced by rotor noise. Further to this, a psychoacoustic annoyance model optimised for rotor noise has been formulated. The model includes a novel psychoacoustic function to account for the perceptual effect of impulsiveness. The significance of the proposed model lies in the quantification of the effects of psychoacoustic factors, such as loudness as the dominant factor, and also tonality, high frequency content, temporal fluctuations, and impulsiveness on rotor noise annoyance.

Enhancing the roll dynamics of an AUV by contra-rotating-propellers

ABSTRACT Roll control of the Autonomous Underwater Vehicles (AUVs) is a significant issue in the current field of research for many researchers in the subject of AUV control system designation. Especially at higher speeds, the roll angle generated by a single rotating propeller or other external disturbances can considerably influence the whole dynamics and therefore the operation of the vehicle. In this paper, the utilisation of a system of contra-rotating-propellers (CRP) to enhance the roll dynamics of an AUV is evaluated by developing a six-degrees-of-freedom (6DOF) dynamics and control systems’ simulator. The results show that: 1. The single propeller system can cause roll angle deflections affecting the heading angle and depth of AUV depending on the forward speed. 2. Using the contra-rotating system with a proper roll controller can enhance the roll dynamics of the vehicle, particularly for the real-time roll stabilisation and maneuvering goals.

THE EFFECT OF ROTOR DISC CLEARANCE ON THE LIFT PERFORMANCE OF CONTRA-ROTATING ROTOR BLADES

Contra-rotating rotor blade is a system that can deliver poised torque condition for any rotorcraft without the manifestation of tail rotor contrivance. This system not only aids to sustain the stability of the aircraft, but also surges the aircraft’s overall efficiency discrete to the conventional single rotor system. Contra-rotation system is capable of operating in reduced size and henceforth is effusively researched and applied to the unmanned micro aerial vehicle (MAV) technology. This study intended to reconnoiter the effect of varying the axial spacing between the forward rotor and the aft rotor of an archetypal contra-rotating rotor blade system. The quantitative data has espoused that the variation of axial spacing between the forward and aft rotor affected the total efficiency of the contra-rotating rotor blade system. Furthermore, at larger spacing, the effects were more substantial contributing adversely to the overall efficiency of the system.

An Overview of the Mechanics of Oscillating Mechanisms

This paper extends a previous study on the mechanics of oscillating mechanisms in which motion of an object is produced by attached rotating eccentric masses. In addition to the well known twin contra-rotating pair (Dean drive), the single eccentric mechanism is studied. In contrast to the contra-rotating systems where the initially still object moves along a vertical track, this study shows that in case of a single eccentric mass the track of the same object is extended in both the horizontal and vertical directions. In both configurations, the path is mainly influenced by the initial linear and angular momentum of the eccentrics. While contra-rotation requires a motor to ensure constant angular velocity, in single systems the latter event is conditionally achieved per se. In order to demonstrate the significance of the initial angular momentum in the motion of the object, the two types of eccentrics were applied for the conditions of the elementary Rutherford-Bohr’s model of a hydrogen atom and also of a virtual hydrogen molecule. It was found that, if intermolecular forces suddenly disappear at a specific synchronization, the virtual molecule or atom is predicted to reach the incredible altitude of 72km.

Performance of a Contrarotating Small Wind Energy Converter

Responding to more demand in coming years, the task of the small wind energy industry requires progress on several fronts—the public policy initiatives, technology development, and market growth. One important issue of the wind energy utilization is the conversion efficiency of the usable energy into productive power. Enhanced technologies such as contrarotating blades, gearbox and lubrication, airfoils, generators, and power electronics will lower cost and increase energy production. The purpose of this paper is, therefore, to reinforce the effectiveness of employing contrarotating system to enhance the performance of a small wind energy converter (SWEC). With this concept, the SWEC works more efficiently and therefore produces more energy in a unit turbine area. To verify the SWEC performance, a research model has been built and tested over a range of operating conditions. Wind tunnel tests were carried out to ascertain the overall performance of the contrarotating SWEC. Results are presented for cases of different wind speeds and Reynolds number. The results demonstrated a significant increase in wind energy conversion efficiency and capability of operation at lower wind speeds while keeping up performance compared to a single-rotor system of the same type.

G0800-1-5 模型実験によるアジマススラスタの操舵反力評価(動力エネルギーシステム部門一般講演(1))

Azimuth thruster is divided into two versions generally. Motors for thrust are installed on ship's hull, and propellers are driven by mechanical transmission gears in case of one version of azimuth thruster. This type of thruster has a perpendicular middle driving shat, the reaction torque acts on the pod because of the driving torque of the perpendicular middle driving shat. When the single perpendicular middle shat is modified to contra-rotating system and the driving torque of outer perpendicular middle shat is equal to that of inner perpendicular middle shat, it is possible to cancel the reaction torque acting on the pod and to prevent the interference between rotation of motor and gyration of pod in principle. We made experimental model of azimuth thruster, and measured reaction force in steering. The difference between modified model and conventional model was evaluated.

20502 操舵反力のないアジマススラスタの設計(一般講演 振動(2))

Azimuth thruster, a kind of marine vessels' thruster, is divided into two versions generally. Motors for thrust are installed on ship's hull, and propellers are driven by mechanical transmission gears in case of one version of azimuth thruster. This type of thruster has a perpendicular middle driving shat, the reaction torque acts on the pod because of the driving torque of the perpendicular middle driving shat. When the single perpendicular middle shat is modified to contra-rotating system and the driving torque of outer perpendicular middle shat is equal to that of inner perpendicular middle shat, it is possible to cancel the reaction torque acting on the pod and to prevent the interference between rotation of motor and gyration of pod in principle.

Propulsion Machinery Considerations for Contrarotating Propeller Systems

Contrarotating (CR) propellers offer one attractive solution to meeting the needs for higher power, more efficient ship propulsion. A planetary second-reduction gear system is proposed to provide the CR energy to a pair of propellers from a conventional turbine power source. The concentric line shafts, bearings, and lubrication system are discussed as vital components to a CR system. Some favorable full-scale operating experience has been obtained on all components except a high-power second-reduction planetary gear operating in the CR mode. The use of a CR propeller system should have a significant economic impact on the powering of ships.