Rotor Concept Research Articles

Dynamics of a pneumatic artificial muscle actuation system driving a trailing edge flap

This study presents a time domain dynamic model of an antagonistic pneumatic artificial muscle (PAM) driven trailing edge flap (TEF) system for next generation active helicopter rotors. Active rotor concepts are currently being widely researched in the rotorcraft community as a means to provide a significant leap forward in performance through primary aircraft control, vibration mitigation and noise reduction. Recent work has shown PAMs to be a promising candidate for active rotor actuation due to their combination of high force, large stroke, light weight, and suitable bandwidth. When arranged into biologically inspired agonist/antagonist muscle pairs they can produce bidirectional torques for effectively driving a TEF. However, there are no analytical dynamic models in the literature that can accurately capture the behavior of such systems across the broad range of frequencies required for this demanding application. This work combines mechanical, pneumatic, and aerodynamic component models into a global flap system model developed for the Bell 407 rotor system. This model can accurately predict pressure, force, and flap angle response to pneumatic control valve inputs over a range of operating frequencies from 7 to 35 Hz (1/rev to 5/rev for the Bell 407) and operating pressures from 30 to 90 psi.

Investigation of Wind Turbine Rotor Concepts for Offshore Wind Farms

Current plans in offshore wind energy developments call for further reduction of cost of energy. In order to contribute to this goal, several wind turbine rotor concepts have been investigated. Assuming the future offshore wind turbines will operate only in the offshore wind farms, the rotor concepts are not only evaluated for their stand-alone performances and their potential in reducing the loads, but also for their performance in an offshore wind farm. In order to do that, the 10MW reference wind turbine designed in Innwind.EU project is chosen as baseline. Several rotor parameters have been modified and their influences are investigated for offshore wind turbine design purposes. This investigation is carried out as a conceptual parametrical study. All concepts are evaluated numerically with BOT (Blade optimisation tool) software in wind turbine level and with Farmflow software in wind farm level for two wind farm layouts. At the end, all these concepts are compared with each other in terms of their advantages and disadvantages.

Synchronous High-Speed Reluctance Machine With Novel Rotor Construction

A new mechanically robust construction for an ultrahigh-speed synchronous reluctance rotor is presented. The two-pole rotor design incorporates soft magnetic flux guides inside nonmagnetic matrix material. Two prototypes based on the concept were constructed and tested. This paper describes the electromagnetic and mechanical design principles of the novel rotor concept.

Design and Performance of a Quad-Shrouded Rotor Micro Air Vehicle

This paper describes the experimental investigation of a quad-shrouded rotor micro air vehicle and focuses on the hover performance improvements over a conventional unshrouded micro quad rotor. The effects of number of rotor blades, blade root pitch angle, and shroud diffuser length on aerodynamic performance were studied. The rotor diameter was 6.6 cm, it had a tip of 20,000, and the gross weight of the vehicle was 90 g, with a shroud weight fraction of 13%. With the optimized design, the power loading of the quad-shrouded rotor was about 15% greater than the unshrouded configuration. To completely evaluate the configuration, the performance of the vehicle in edgewise flow was investigated. The drag and pitching moment for the shrouded rotor was about 2.5 times greater than the unshrouded vehicle. However, control-moment measurements suggested that the edgewise gust tolerance was at least . The vehicle prototype was also successfully flight tested in hover using onboard feedback regulation. Based on these studies, the shrouded rotor concept appears feasible in improving performance of a conventional micro quad rotor even at and can be easily retrofitted into existing configurations.

Micro Rotor Enhanced Block Cipher Designed For Eight Bits Micro-Controllers (MREBC)

The sensor network is a wireless network environment that consists of the many sensors of lightweight and low-power. Authentication between nodes is very vital for network reliability and the integrity of information collected by these nodes. Therefore, encryption algorithm for the implementation of reliable sensor network environments is required to the applicable sensor network. This paper gives a new proposed cryptosystem (MREBC) that is designed for 8 bits microcontroller systems. MREBC uses the concept of rotor enhanced block cipher which was initially proposed by the author in [NRSC 2002] on the first version of REBC. MREBC uses rotors to achieve two basic cryptographic operations; permutation, and substitution. Round key is generated using rotor too, which is used to achieve ciphertext key dependency. Rotors implemented using 8 bits successive affine transformation, which achieves memoryless, normalized ciphertext statistics, and small processing speed trend. The strength of this system is compared with the RIJNDAEL (AES) cipher. MREBC cipher gives excellent results from security characteristics and statistical point of view of. communication efficiency of MREBC is compared with AES through measuring performance by plaintext size, and cost of operation per hop according to the network scale. Arduino microcontroller board is used to implement both MREBC, and AES in order to compare the performance of algorithms. Authors suggests to use MREBC to implement a reliable sensor network environments.

Turbulent Flow Characteristics and Dynamics Response of a Vertical-Axis Spiral Rotor

The concept of a vertical-axis spiral wind rotor is proposed and implemented in the interest of adapting it to air flows from all directions and improving the rotor’s performance. A comparative study is performed between the proposed rotor and conventional Savonius rotor. Turbulent flow features near the rotor blades are simulated with Spalart-Allmaras turbulence model. The torque coefficient of the proposed rotor is satisfactory in terms of its magnitude and variation through the rotational cycle. Along the height of the rotor, distinct spatial turbulent flow patterns vary with the upstream air velocity. Subsequent experiments involving a disk generator gives an in-depth understanding of the dynamic response of the proposed rotor under different operation conditions. The optimal tip-speed ratio of the spiral rotor is 0.4–0.5, as is shown in both simulation and experiment. Under normal and relative-motion flow conditions, and within the range of upstream air velocity from 1 to 12 m/s, the output voltage of the generator was monitored and statistically analyzed. It was found that normal air velocity fluctuations lead to a non-synchronous correspondence between upstream air velocity and output voltage. In contrast, the spiral rotor’s performance when operating from the back of a moving truck was significantly different to its performance under the natural conditions.

Review of experimental investigations into the design, performance and optimization of the Savonius rotor

The Savonius rotor is a drag-based vertical axis wind turbine and is used as an alternative source in small-scale energy generation. Design simplicity, low-cost, easy installation, good starting ability, relatively low operating speed and independent to wind directions are the main advantages of this rotor. However, because of its low efficiency and high negative torque produced by the returning blade, this rotor concept rarely gained popularity. Over the last few decades, although a number of investigations around the world have reported performance gains of the Savonius rotor, the available technical design is still not able to fulfill the demand of efficient small-scale wind energy converter at low wind speeds. Until now, various design changes have been proposed to meet a growth in power output through optimization of influencing variables like aspect ratio, overlap ratio, blade material, and so forth. Investigations have also been carried out by installing additional devices like curtain design, deflector plate, nozzle and ducts, multi-staging, guide-box tunnel and windshields. Installation of these devices considerably reduced the negative torque as well as improved the starting performance of the rotor. As a result, the power output of the rotor is also improved. Several researchers have reported increased power coefficients for various rotor designs based on their different testing parameters. Power coefficients for the conventional Savonius rotors have been mostly reported in the range of 0.12–0.18 and by optimizing its design, it can reach as high as 0.38. This article attempts to discuss the various influencing parameters as well as the augmentation techniques. This would offer an overall idea on the progress that has taken place to improve the design and performance of the Savonius rotor.

A 64 Bits Rotor Enhanced Block Cipher (Rebc3)

This paper gives a new proposed c ryptosystem (REBC3) that is designed to take advantages of the new generation of 64bits microprocessors whi ch commercially known as x64systems. The old version REBC2 , which was published in Africon 2007. REBC2 was basically developed for the 32bits microp rocessors which is commercially known as x86 systems. REBC3 like REBC2 use the concept of rotor enhanced block cipher which was initially proposed by the author in [NRSC 2002] on the first version of REBC. REBC2 used the same concept from a another point of view, which is using rotors to achieve two basic cryptographic operations; permutation, and substitution. Round key is generated using rotor too, which is used to achieve ciphertext key dependency. To enhance non -linearity and to resist linear cryptanalysis, REBC3 has a variable block, and key lengths. Each round has its own block length which depends on round the key and round key length. Dependency is based upon the previous round generated key. Rotors implemented using successive affine transformation . The 32 bits version was proposed in KAMFEE cipher, then the 64bits version was proposed in KAMFEE -X64 cipher. This achieved memory -less, normalized ciphertext statistics, and small processing speed trend. The strength of this system is compared with the REBC2 and RIJNDAEL (AES) ciphers.REBC3 cipher gives excellent results from security characteristics and statistical point of view of. So authors suggests to use REBC3 in the area of banking and electronic fund transfer.

Numerical Investigations of Unsteady Flow in a Centrifugal Pump with a Vaned Diffuser

Computational fluid dynamics (CFD) analyses were made to study the unsteady three-dimensional turbulence in the ERCOFTAC centrifugal pump test case. The simulations were carried out using the OpenFOAM Open Source CFD software. The test case consists of an unshrouded centrifugal impeller with seven blades and a radial vaned diffuser with 12 vanes. A large number of measurements are available in the radial gap between the impeller and the diffuse, making this case ideal for validating numerical methods. Results of steady and unsteady calculations of the flow in the pump are compared with the experimental ones, and four different turbulent models are analyzed. The steady simulation uses the frozen rotor concept, while the unsteady simulation uses a fully resolved sliding grid approach. The comparisons show that the unsteady numerical results accurately predict the unsteadiness of the flow, demonstrating the validity and applicability of that methodology for unsteady incompressible turbomachinery flow computations. The steady approach is less accurate, with an unphysical advection of the impeller wakes, but accurate enough for a crude approximation. The different turbulence models predict the flow at the same level of accuracy, with slightly different results.

Smart dynamic rotor control using active flaps on a small‐scale wind turbine: aeroelastic modeling and comparison with wind tunnel measurements

ABSTRACTIn this paper, the proof of concept of a smart rotor is illustrated by aeroelastic simulations on a small‐scale rotor and comparison with wind tunnel experiments. The application of advanced feedback controllers using actively deformed flaps in the wind tunnel measurements is shown to alleviate dynamic loads leading to considerable fatigue load reduction. The numerical method for aeroelastically simulating such an experiment is described, together with the process of verifying the methods for accurate prediction of the load reduction potential of such concepts. The small‐scale rotor is simulated using the aeroelastic tool, load predictions are compared with the wind tunnel measurements, and similar control concepts are compared and evaluated in the numerical environment. Conclusions regarding evaluation of the performance of smart rotor concepts for wind turbines are drawn from this threefold research investigation (simulation, experiment and comparison). Copyright © 2012 John Wiley & Sons, Ltd.

Far-Field Sound Radiation Due to an Installed Open Rotor

Future single rotation propeller and contra-rotating advanced open rotor concepts promise a significant fuel efficiency advantage over current generation turbofan engines. The development of rotors which produce a minimum level of noise is a critical technical issue which needs to be resolved in order for these concepts to become viable aircraft propulsors. Noise and emissions are subject to stringent legislative requirements, thus accurate models are required in order to predict the noise radiated from aircraft engines. In this article, the development of a theoretical model to predict noise levels of an installed open rotor is reported. First a canonical problem is examined: how to predict the pressure field produced by a rotating ring of point sources adjacent to a rigid cylinder. Analytic expressions for the far-field pressure from a rotating ring of single-frequency monopole and dipole point sources, located near an infinitely long rigid cylinder, immersed in a constant axial mean flow, are explicitly formulated. Illustrative results show how the far-field pressure is affected by varying the source rotational direction, source location and source radius. Next the solution of the canonical problem is utilized to formulate a more advanced model to predict the noise due to an installed open rotor. In this model, the rotor noise sources are represented by a distribution of rotating sources. The adjacent aircraft fuselage is modeled by the rigid cylinder, and the effect of the fuselage boundary layer and other steady distortions are neglected. Also neglected is the scattering from other surfaces such as the pylon, wing and centerbody. This distributed source model can be used to calculate the effect of scattering of open rotor noise by an adjacent cylindrical fuselage. The model can be used to calculate both rotor-alone tones and tones produced by periodic unsteady loading on the rotor blades. Practical examples are provided which show how the effect of blade rotational direction and propeller location relative to the fuselage affect the sound produced by the interaction of a pylon wake with a rotor in a pusher configuration.

Design, Propulsive Force Prediction and Test of a Electromagnetic Drive Mechanism of a New Concept of Micro Flapping Wing Rotor

To further increase the lift and rotate speed of a micro flapping wing rotor, a electromagnetic mechanism is designed to achieved high amplitude and small friction. Then average propulsive force using Theodorsen’s theory is simulated to confirm the parameter affect. In the end, the relationship of average lift, average propulsive force, rotate speed are shown in the experiment and test results represent that this mechanism has much better performance than PZT one.

Design, Lift Prediction and Test of a PZT Drive Mechanism of a New Concept of Micro Flapping Wing Rotor

To reduce the complexity involved in achieving the intricate motion and hence complexity mechanism, a new concept of Micro Flapping wing Rotor is firstly proposed to achieve active flapping and passive rotary motion. Secondly, aerodynamic analysis is made to understand schematic principles of this MFWR. Thirdly, parametric study (flapping amplitude, flapping frequency and initial angle of attack) using Theodorsen’s theory for lift prediction makes a significantly role for aerodynamic characteristics. At last, the prototype of a piezoelectric drive mechanism is designed and tested to compare the experimental data with theoretical values. The comparison shows that the lift prediction is closer to the experimental results.

Low Frequency Noise from Wind Turbines Mechanisms of Generation and its Modelling

The objective of the present paper is to present an overview of LFN characteristics of modern MW turbines based on numerical simulations. Typical sizes of modern turbines are from 1–3 MW nominal generator power and a rotor diameter ranging from 80–100 m but larger prototypes up to 5 MW and with a rotor diameter of 126 m have now been installed. The numerical investigations comprise the common upwind rotor concept but also the turbines with a downwind rotor are considered. The reason to include the downwind rotor concept is that this turbine design has some advantages which could lead to future competitive designs compared with the upwind threebladed rotor. The simulation package comprises an aeroelastic time simulation code HAWC2 and an acoustic low frequency noise (LFN) prediction model. Computed time traces of rotor thrust and rotor torque from the aeroelastic model are input to the acoustic model which computes the sound pressure level (SPL) at a specified distance from the turbine. The influences on LFN on a number of turbine design parameters are investigated and the position of the rotor relative to the tower (upwind or downwind rotor) is found to be the most important design parameter. For an upwind rotor the LFN levels are so low that it should not cause annoyance of neighbouring people. Important turbine design parameters with strong influence on LFN are the blade tip speed and the distance between rotor and tower.

Design of a scaled wind turbine with a smart rotor for dynamic load control experiments

AbstractThe ever increasing size of wind turbines poses a number of design issues for the industry, like increasing component mass and fatigue loads. An interesting concept for reducing fatigue loads is the implementation of spanwise distributed devices to control the aerodynamic loading along the span of the blade, thus mitigating fluctuations in loading and adding damping to the blade modes. This is usually referred to as the smart rotor concept. In the design of such a rotor, as compared to a traditional one, the integration of sensors and actuators poses additional design challenges. In the research discussed in this paper, a scaled smart rotor was designed and constructed to study its fatigue load reduction potential. A 1.8 m diameter rotor was manufactured and equipped with trailing‐edge flaps. The flaps were based on piezo electric Thunder actuators that allow for high‐frequent actuation. The dynamic strain behaviour of the blade was analysed for optimal placement of the sensors. Several sensors that record the strains and accelerations at different locations along the blade were implemented, but the controller was based on a piezo electric strain sensor. The rotor blades were mounted on a small turbine in the Delft University's Open Jet Facility wind tunnel and a mathematical state space model was obtained by using dedicated system identification techniques. Single‐Input Single‐Output, Multi‐Input Multi‐Output ℋ︁∞ feedback and feedforward controllers were designed, each focusing on different parts of the load spectrum. The rotor was tested at 0 and 5° yaw angles, with and without load control. A significant reduction of the dynamic loads was attained. Copyright © 2010 John Wiley & Sons, Ltd.

Performance of a Cycloidal Rotor Concept for Micro Air Vehicle Applications

Performance of a Cycloidal Rotor Concept for Micro Air Vehicle Applications

Identification and optimal control methodology for an active twist rotor

AbstractONERA — French Aerospace Lab — developed an innovative rotor concept, featuring two independent piezo-electric actuators embedded within each blade. This patented concept allows a dynamic modification of the blade twist during a rotor revolution. The main goal is to reduce drastically the vibrations transmitted to the helicopter mast and structure, thus reducing simultaneously the fatigue and maintenance needs of the structural elements in the long term, as well as the discomfort felt by pilot and passengers. In order to ensure the stabilization of the rotor, as well as the effective decrease of rotor vibrations, a closed-loop control scheme is currently developed and simulated by ONERA Systems Control and Flight Mechanics Department (ONERA/DCSD). An adaptive, Kalman-filter based, estimation of the open-loop transfer is made, then a linear quadratic optimal control gain is calculated in order to ensure the convergence towards the objective values. During the initial part of the project, this control law is simulated through a coupling with a rotor calculation code, and the numerical results show an effective reduction of the various vibration components. After these validation steps, the control law has been implemented in a real-time environment and will be used for the wind-tunnel test phase of the active rotor.

Updating and Optimization of a Coning Rotor Concept

The work detailed in this paper is focused on updating and refining a coning rotor wind turbine concept. The coning rotor combines the load shedding properties of flapping hinges with gross change in rotor area, via large coning angles, to affect increased energy capture at nominally constant system cost. Previous studies have indicated that the large cost of energy reductions is possible, compared to the state-of-the-art machines then, particularly for abundant but presently uneconomic low-wind sites. Almost ten years later, the fundamentals of the design remain sound, but bear reevaluation relative to current machines, both exploiting modern power electronics and control technology. The coning rotor was never optimized in its own right, so an integrated design tool suitable for human and computer refinement of the design has been developed. Incorporated into the tool is a corrected blade element momentum method that more properly accounts for coned rotor aerodynamics. A discussion of the development of coning rotors is presented, along with a comparison to present operational strategies. Results obtained for nondimensionalized rotors and specific machine optimization studies are presented, followed by a discussion of further issues to be addressed.

Optimal location of centre of gravity for swashplateless helicopter UAV and MAV

PurposeTo investigate the use of centre of gravity location on reducing cyclic pitch control for helicopter UAV's (unmanned air vehicles) and MAV's (micro air vehicles). Low cyclic pitch is a necessity to implement the swashplateless rotor concept using trailing edge flaps or active twist using current generation low authority piezoceramic actuators.Design/methodology/approachAn aeroelastic analysis of the helicopter rotor with elastic blades is used to perform parametric and sensitivity studies of the effects of longitudinal and lateral center of gravity (cg) movements on the main rotor cyclic pitch. An optimization approach is then used to find cg locations which reduce the cyclic pitch at a given forward speed.FindingsIt is found that the longitudinal cyclic pitch and lateral cyclic pitch can be driven to zero at a given forward speed by shifting the cg forward and to the port side, respectively. There also exist pairs of numbers for the longitudinal and lateral cg locations which drive both the cyclic pitch components to zero at a given forward speed. Based on these results, a compromise optimal cg location is obtained such that the cyclic pitch is bounded within ±5° for a BO105 helicopter rotor.Originality/valueThe reduction in the cyclic pitch due to helicopter cg location is found to significantly reduce the maximum magnitudes of the control angles in flight, facilitating the swashplateless rotor concept. In addition, the existence of cg locations which drive the cyclic pitches to zero allows for the use of active cg movement as a way to replace the cyclic pitch control for helicopter MAV's.

Induced shear actuation of helicopter rotor blade for active twist control

Induced shear based mechanism is used for attaining active twist in a soft-inplane hingeless rotor with a two-cell thin-walled airfoil section. The rotor properties dynamically represent a real rotor. A closed loop controller is developed to obtain the optimum voltage required to be given to the rotor blade for obtaining twist using strain rate feedback. Nonlinear relationship between piezoelectric shear coefficient and applied electric field is included in the controller design. Optimal placement of actuators lead to an overall vibration reduction of about 65%. Since thin-walled structures such as rotor blades are highly flexible and have strong aeroelastic effects, these effects on the loads and stability are thoroughly studied to evaluate the feasibility of the active twist rotor concept. No aeroelastic instabilities are found to occur due to active twist.