Journal articles on the topic 'Rotor-blade system'
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1
Ngui, Wai Keng, M. Salman Leong, L. M. Hee, and Ahmed M. Abdelrhman. "Detection of Twisted Blade in Multi Stage Rotor System." Applied Mechanics and Materials 773-774 (July 2015): 144–48. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.144.
Abstract:
This paper studies the detection of twisted blade in a multi stages rotor system. Experimental study was undertaken to simulate twisted blade conditions in a three stages rotor system. The feasibility of vibration analysis as the technique to detect twisted blade based on the rotor operating frequency and its blade passing frequency was investigated in this study. Experimental results show that twisted blade can be easily detected by looking into the pattern of the vibration spectrum and its individual peaks.
2
Dalli, Uğbreve;ur, and Şcedilefaatdin Yüksel. "Identification of Flap Motion Parameters for Vibration Reduction in Helicopter Rotors with Multiple Active Trailing Edge Flaps." Shock and Vibration 18, no. 5 (2011): 727–45. http://dx.doi.org/10.1155/2011/675791.
Abstract:
An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.
3
Lee, Yu-Tai, and JinZhang Feng. "Potential and Viscous Interactions for a Multi-Blade-Row Compressor." Journal of Turbomachinery 126, no. 4 (October 1, 2004): 464–72. http://dx.doi.org/10.1115/1.1740778.
Abstract:
A computationally efficient time-accurate vortex method for unsteady incompressible flows through multiple blade row systems is presented. The method represents the boundary surfaces using vortex systems. A local coordinate system is assigned to each independently moving blade row. Blade shed vorticity is determined from two generating mechanisms and convected using the Euler equation. The first mechanism of vorticity generation is a potential mechanism from a nonlinear unsteady pressure-type Kutta condition applied at the blade trailing edges. The second mechanism is a viscous mechanism from a viscous wake vorticity (VWV) model implemented to simulate the viscous shear layers on the blade pressure and suction sides. Two different two-blade-row compressor systems, a rotor/stator (R/S) system and a stator/rotor (S/R) system, were used to investigate the interaction forces on each blade row. Computational results of the potential and viscous interaction forces are presented and compared to measurements. The comparison suggests that the viscous wake interaction accounts for 25–30% of the peak loading for an axial spacing of 10% chord length between the blade rows. The efficient computational method is particularly attractive for blade indexing study. Therefore a three-blade-row rotor/stator/rotor (R1/S/R2) compressor system is used to demonstrate the indexing calculations between the two rotor positions. Resultant forces on each blade row are presented for ten rotor indexing positions and three axial gap sizes for the gaps between R1 and S and between S and R2. The unsteady peak-to-peak force can reach 10–15% of inflow dynamic head for the gap spacing investigated. The minimum-to-maximum variation of the unsteady force can account for 40–50% of averaged unsteady force.
4
Lu, Zhenyong, Shun Zhong, Huizheng Chen, Yushu Chen, Jiajie Han, and Chao Wang. "Modeling and Dynamic Characteristics Analysis of Blade-Disk Dual-Rotor System." Complexity 2020 (January 25, 2020): 1–13. http://dx.doi.org/10.1155/2020/2493169.
Abstract:
In this paper, a simplified dynamic model of a dual-rotor system coupled with blade disk is built, and the effects of blade parameters of an aircraft engine on the dynamic characteristics of a dual-rotor system are studied. In the methodology, the blade is simplified as a cantilever structure, and the dynamical equations are obtained by the means of a finite element method. The amplitude-frequency response curves and orbits of shaft centre-vibration shape diagram are used to analyze the effects of blade parameters on dynamic characteristics of a dual-rotor system. The results indicate that the properties of the blades have huge impacts on the critical speed and other dynamic characteristics of the system. With an increase of the length of the blade, the second-order critical speed decreases obviously, but the first-order critical speed is almost invariant; this means that the blades attached on the low-pressure compressor do not affect the first-order critical speed of the dual-rotor system. Meanwhile, note that the high-pressure rotor and low-pressure turbine rotor can excite the first-order resonance of the dual-rotor system, while the low-pressure compressor rotor can only excite the second-order resonance, and then the dynamic model of this six-point support dual-rotor system can further be simplified as a relatively independent single-rotor system with one disk and a four-support dual-rotor system with dual disks.
5
Wang, Nanfei, Chao Liu, and Dongxiang Jiang. "Prediction of transient vibration response of dual-rotor-blade-casing system with blade off." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 14 (April 4, 2019): 5164–76. http://dx.doi.org/10.1177/0954410019839884.
Abstract:
Fan blade off occurring in a running rotor of the turbofan engine dual-rotor system will cause a sudden unbalance and inertia asymmetry, which results in large impact load and consequently induces the rubbing between blade and casing. In order to reveal the transient dynamic response characteristics of actual aero-engine when fan blade off event occurs, the dynamic model of dual-rotor-blade-casing system is developed, in which the distribution characteristics of the stiffness and mass, the load transfer, and the coupling effects of dual-rotor and casing are included. Considering several excitations caused by blade off, the physical process and mechanical characteristics of the fan blade off event are described qualitatively. Considering that only the casing acceleration signal can be used for condition monitoring in actual aero-engine, the transient response including rotor vibration displacement and casing vibration acceleration during the instantaneous status are obtained. Due to the time-varying and highly nonlinear characteristics of vibration responses, frequency slice wavelet transform is employed to isolate the vibration signal features. The results show that the impact load induced by the sudden imbalance causes significant increase of vibration amplitude. The rubbing action between blade and rotor will impose constraint effects on the rotor, which decreases the transient vibration amplitude. The inertia asymmetry has a big impact on the transient response. The vibration characteristics of casing acceleration under blade off are similar to those of rotor displacement, while casing acceleration response attenuates to stable value faster and is more sensitive to high-frequency components of vibration.
6
Lu, Xin, Jie Tang, and Liwen Wang. "Simulation and Experimental Study on Rotor System Dynamic Analysis with the Blade-Coating Rubbing Faults." Shock and Vibration 2021 (September 10, 2021): 1–15. http://dx.doi.org/10.1155/2021/2442760.
Abstract:
In the modern turbo-machinery, reducing the clearance between the blade tip and casing inner face is an effective method to improve the power performance, but the clearance reduction leads to increased risk of blade-casing rubbing. In this paper, a blade-coating rubbing force model which considered the abradable coating scraping is developed to simulate the rotor system dynamic characteristics at blade-casing rubbing faults with abradable coating. An experimental tester is established to simulate the rotor system blade-casing rubbing faults; the AlSi-ployphenyl ester abradable coating is prepared and introduced into the blade-casing experiment to verify the model. After the vibration and force analysis in simulation and experiment, the dynamic characteristics and the influence factors of blade-casing rubbing rotor system are studied.
7
Zalkind, Daniel S., Gavin K. Ananda, Mayank Chetan, Dana P. Martin, Christopher J. Bay, Kathryn E. Johnson, Eric Loth, D. Todd Griffith, Michael S. Selig, and Lucy Y. Pao. "System-level design studies for large rotors." Wind Energy Science 4, no. 4 (November 11, 2019): 595–618. http://dx.doi.org/10.5194/wes-4-595-2019.
Abstract:
Abstract. We examine the effect of rotor design choices on the power capture and structural loading of each major wind turbine component. A harmonic model for structural loading is derived from simulations using the National Renewable Energy Laboratory (NREL) aeroelastic code FAST to reduce computational expense while evaluating design trade-offs for rotors with radii greater than 100 m. Design studies are performed, which focus on blade aerodynamic and structural parameters as well as different hub configurations and nacelle placements atop the tower. The effects of tower design and closed-loop control are also analyzed. Design loads are calculated according to the IEC design standards and used to create a mapping from the harmonic model of the loads and quantify the uncertainty of the transformation. Our design studies highlight both industry trends and innovative designs: we progress from a conventional, upwind, three-bladed rotor to a rotor with longer, more slender blades that is downwind and two-bladed. For a 13 MW design, we show that increasing the blade length by 25 m, while decreasing the induction factor of the rotor, increases annual energy capture by 11 % while constraining peak blade loads. A downwind, two-bladed rotor design is analyzed, with a focus on its ability to reduce peak blade loads by 10 % per 5∘ of cone angle and also reduce total blade mass. However, when compared to conventional, three-bladed, upwind designs, the peak main-bearing load of the upscaled, downwind, two-bladed rotor is increased by 280 %. Optimized teeter configurations and individual pitch control can reduce non-rotating damage equivalent loads by 45 % and 22 %, respectively, compared with fixed-hub designs.
8
Christensen, René H., and Ilmar F. Santos. "Active Rotor-Blade Vibration Control Using Shaft-Based Electromagnetic Actuation." Journal of Engineering for Gas Turbines and Power 128, no. 3 (March 1, 2004): 644–52. http://dx.doi.org/10.1115/1.2056533.
Abstract:
In this paper the feasibility of actively suppressing rotor and blade vibration via shaft-based actuation is studied. A mathematical model is derived, taking into account the special dynamical characteristics of coupled rotor-blade systems, such as centrifugal stiffened blades and parametric vibration modes. An investigation of controllability and observability shows that if the blades are properly mistuned, it is possible to suppress shaft as well as blade vibration levels by using only shaft-based actuation and sensing; though, in tuned bladed systems, shaft as well as blade actuation and sensing are required. In order to cope with the time-variant dynamics of the coupled rotor-blade system, a periodic time-variant modal controller is designed, implemented, and experimentally tested. A test rig built by four flexible blades is specially designed for this purpose. The rig is equipped with six electromagnetic actuators and different types of sensors (eddy-current displacement transducers, acceleration transducers, and strain gages) with the aim of monitoring and controlling shaft and blade vibration levels. Two different actively controlled rotor-blade system configurations are considered in the present study: (i) a tuned bladed rotor, controlled with help of actuators attached to the rotating blades and shaft-based actuators; (ii) a deliberately mistuned bladed rotor controlled only via shaft-based actuation. Experimental tests are carried out for both configurations. Some experimental problems regarding control implementation are identified and discussed, especially when the controller order and the number of actuators in the centralized control scheme become too high; though, for the mistuned bladed rotor controlled by using only shaft-based actuation, the controller works well.
9
Abdelrhman, Ahmed M., M. Salman Leong, Yasin M. Hamdan, and Kar Hoou Hui. "Time Frequency Analysis for Blade Rub Detection in Multi Stage Rotor System." Applied Mechanics and Materials 773-774 (July 2015): 95–99. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.95.
Abstract:
Blade fault is one of the most causes of failure in turbo machinery. This paper discussed the time frequency analysis for blade rubbing detection from casing vibration signal. Feasibility of Short Time Fourier Transform (STFT), Wigner-Ville distribution (WVD) and Choi-Williams distribution (CWD) were examined for blade rub detection in a multi stage blade system through an experimental data. Analysis results of the experimental data showed that these time frequency analysis methods have some inevitable deficiencies in segregating the blade passing frequency (BPF) components of the three rotor stage signals. However, CWD demonstrated a better time-frequency resolution in analyzing the multi stage rotor system signal.
10
Qian, Xiaoru, Peigang Yan, Xiangfeng Wang, and Wanjin Han. "Numerical Analysis of Conjugated Heat Transfer and Thermal Stress Distributions in a High-Temperature Ni-Based Superalloy Turbine Rotor Blade." Energies 15, no. 14 (July 7, 2022): 4972. http://dx.doi.org/10.3390/en15144972.
Abstract:
This paper establishes a multidisciplinary method combining conjugate heat transfer (CHT) and thermal stress for a high-temperature Ni-based superalloy turbine rotor blade with integrated cooling structures. A conjugate calculation is performed to investigate the coolant flow characteristics, heat transfer, and thermal stress of the rotor blade under rotating and stationary conditions to understand the effects of rotation on the multidisciplinary design of the blade. Furthermore, the maximum resolved shear stress among the 30-slip systems and the corresponding dominant slip system are obtained to predict the deformation tendency of the blade by employing the crystal plasticity finite element method (CPFEM) and considering the specified anisotropic blade material (GTD-111). The results show that the forces of rotation, including centrifugal and Coriolis forces, and their induced buoyancy force, alter the coolant flow field and thus affect the rotor blade’s heat transfer distribution compared with the stationary condition. The maximum temperature and thermal stress of the rotor blade under rotating conditions are reduced by 5% and 21% compared with that under the stationary condition, respectively. Compared with the stationary condition, the temperature and thermal stress distribution on the blade under the rotating condition are more uniform, especially on the suction side. In addition, the blade root connecting with the hub, the film holes near the leading-edge region at the blade root, the mid-chord of the suction surface, and the grooved blade tip are easily damaged by the enormous resolved shear stress and the interface effect of different types of dominant slip system under the two conditions. In this work, it was feasible to use the cascade cooling effect test to analyze the dynamic test results for the rotor blade. Furthermore, the thermal stress analysis based on the CPFEM can provide a superior level of blade cooling design than CHT by considering the anisotropic material characteristics of a turbine blade.
11
Wang, Yu, Mao Sun, and Chao Yan. "Numerical simulation of hovering flow field and interference characteristics of rotor system." Journal of Physics: Conference Series 2235, no. 1 (May 1, 2022): 012002. http://dx.doi.org/10.1088/1742-6596/2235/1/012002.
Abstract:
Abstract In order to investigate the aerodynamic interference characteristics of tandem rotor, this paper simulates the hovering flow field of single rotor and tandem rotor based on the dynamic structure overset grid method and unsteady Navier-Stokes equations in computational fluid dynamics (CFD). In the study of hover state of single rotor with twist, the trajectory of the blade vortex and the change pattern are briefly analyzed. Subsequently, the flow field disturbance of tandem rotor, the vortex structure, the pull coefficient and the downwash flow are investigated. The results show that there is obvious blade vortex interference in the overlapping area of the tandem rotor, where the downwash flow reduces the effective angle of attack of the blade and thus has a significantly effect on the pull coefficient. The rotor is less disturbed when it is far from the overlapping area, and the tension coefficient does not change significantly. After integrating the pull coefficient of the upper and lower rotors in one cycle, it was found that the loss of pull coefficient of the two rotors reached 5.7% and 10.7% respectively, which proved that the aerodynamic interference between the tandem rotor in hovering condition had an important effect on the aerodynamic performance of the vehicle.
12
Villeneuve, Eric, Derek Harvey, David Zimcik, Roger Aubert, and Jean Perron. "Piezoelectric Deicing System for Rotorcraft." Journal of the American Helicopter Society 60, no. 4 (October 1, 2015): 1–12. http://dx.doi.org/10.4050/jahs.60.042001.
Abstract:
Deicing using piezoelectric actuators is considered as a potential solution to the development of low-energy ice protection systems for rotorcraft. This type of system activates resonant frequencies of a structure using piezoelectric actuators to generate sufficient stress to break the bond between the ice and the substrate. First, a numerical method was validated to assist the design of such systems. Numerical simulations were performed for the case of a flat plate and validated experimentally. The model was then used to study important design parameters such as actuator positioning and activation strategies, and it was concluded that positioning actuators at antinode locations, and activating them in phase with those antinodes to obtain maximum displacements for a given vibration mode. The findings were then used to apply piezoelectric deicing to structures more representative of a helicopter rotor blade. The method was implemented on a thinned Bell 206 main rotor blade and a Bell 206 tail rotor blade. Deicing performance was demonstrated in an icing wind tunnel. Power input to the actuators was below 19 kW/m2 (12 W/inch2) for all structures.
13
Augustyn, Marcin, and Filip Lisowski. "Experimental and Numerical Studies on a Single Coherent Blade of a Vertical Axis Carousel Wind Rotor." Energies 16, no. 14 (July 21, 2023): 5532. http://dx.doi.org/10.3390/en16145532.
Abstract:
This article presents the results of experimental and numerical studies on a single coherent rotor blade. The blade was designed for a vertical-axis wind turbine rotor with a self-adjusting system and planetary blade rotation. The experimental tests of the full-scale blade model were conducted in a wind tunnel. A computational fluid dynamics (CFD) analysis of the blade’s cross section was then carried out, including the boundary conditions corresponding to those adopted in the wind tunnel. The main objective of the study was to determine the aerodynamic forces and aerodynamic moment for the proposed single coherent cross-section of the blade for the carousel wind rotor. Based on the obtained results and under some additional assumptions, the driving torque of the wind rotor was determined. The obtained results indicated the possibility of using the proposed blade cross-section in the construction of a carousel wind rotor.
14
Giljarhus, Knut Erik Teigen, Alessandro Porcarelli, and Jørgen Apeland. "Investigation of Rotor Efficiency with Varying Rotor Pitch Angle for a Coaxial Drone." Drones 6, no. 4 (April 4, 2022): 91. http://dx.doi.org/10.3390/drones6040091.
Abstract:
Coaxial rotor systems are appealing for multirotor drones, as they increase thrust without increasing the vehicle’s footprint. However, the thrust of a coaxial rotor system is reduced compared to having the rotors in line. It is of interest to increase the efficiency of coaxial systems, both to extend mission time and to enable new mission capabilities. While some parameters of a coaxial system have been explored, such as the rotor-to-rotor distance, the influence of rotor pitch is less understood. This work investigates how adjusting the pitch of the lower rotor relative to that of the upper one impacts the overall efficiency of the system. A methodology based on blade element momentum theory is extended to coaxial rotor systems, and in addition blade-resolved simulations using computational fluid dynamics are performed. A coaxial rotor system for a medium-sized drone with a rotor diameter of 71.12 cm is used for the study. Experiments are performed using a thrust stand to validate the methods. The results show that there exists a peak in total rotor efficiency (thrust-to-power ratio), and that the efficiency can be increased by 2% to 5% by increasing the pitch of the lower rotor. The work contributes to furthering our understanding of coaxial rotor systems, and the results can potentially lead to more efficient drones with increased mission time.
15
Mohammed, Abdulbasit, Hirpa G. Lemu, and Belete Sirahbizu. "Determining Optimum Rotary Blade Design for Wind-Powered Water-Pumping Systems for Local Selected Sites." Strojniški vestnik – Journal of Mechanical Engineering 67, no. 5 (June 15, 2021): 214–22. http://dx.doi.org/10.5545/sv-jme.2021.7140.
Abstract:
The design of a windmill rotor is critical for harnessing wind energy. In this work, a study is conducted to optimize the design and performance of a rotor blade that is suitable for low wind conditions. The windmills’ rotor blades are aerodynamically designed based on the SG6043 airfoil and wind speed data at local selected sites. The aerodynamic profile of the rotor blade that can provide a maximum power coefficient, which is the relation between real rotor performance and the available wind energy on a given reference area, was calculated. Different parameters, such as blade shapes, chord distributions, tip speed ratio, geometries set angles, etc., were used to optimize the blade design with the objective of extracting maximum wind power for a water pumping system. Windmill rotor of 10.74 m, 7.34 m, and 6.34 m diameter with three blades were obtained for the selected sites at Abomsa, Metehara, and Ziway in south-east Ethiopia. During the rotary blades performance optimization, blade element momentum (BEM) theory and solving iteration by MATLAB® coding were used.
16
Mohammed, Abdulbasit, Hirpa G. Lemu, and Belete Sirahbizu. "Determining Optimum Rotary Blade Design for Wind-Powered Water-Pumping Systems for Local Selected Sites." Strojniški vestnik – Journal of Mechanical Engineering 67, no. 5 (May 26, 2021): 214–22. http://dx.doi.org/10.5545/sv-jme.2021.7104.
Abstract:
The design of a windmill rotor is critical for harnessing wind energy. In this work, a study is conducted to optimize the design and performance of a rotor blade that is suitable for low wind conditions. The windmills’ rotor blades are aerodynamically designed based on the SG6043 airfoil and wind speed data at local selected sites. The aerodynamic profile of the rotor blade that can provide a maximum power coefficient, which is the relation between real rotor performance and the available wind energy on a given reference area, was calculated. Different parameters, such as blade shapes, chord distributions, tip speed ratio, geometries set angles, etc., were used to optimize the blade design with the objective of extracting maximum wind power for a water pumping system. Windmill rotor of 10.74 m, 7.34 m, and 6.34 m diameter with three blades were obtained for the selected sites at Abomsa, Metehara, and Ziway in south-east Ethiopia. During the rotary blades performance optimization, blade element momentum (BEM) theory and solving iteration by MATLAB® coding were used.
17
Zuo, Chenglin, Chunhua Wei, Jun Ma, Tingrui Yue, Lei Liu, and Zheyu Shi. "Full-Field Displacement Measurements of Helicopter Rotor Blades Using Stereophotogrammetry." International Journal of Aerospace Engineering 2021 (January 8, 2021): 1–18. http://dx.doi.org/10.1155/2021/8811601.
Abstract:
This study presents a stereophotogrammetry approach to achieve full-field displacement measurements of helicopter rotor blades. The method is demonstrated in the wind tunnel test of a 2 m diameter rotor, conducted at the 5.5 m × 4 m Aeroacoustic Wind Tunnel of China Aerodynamics Research and Development Center (CARDC). By arranging the retroreflective targets on the special hat installed directly above the rotor hub, the dynamic motion of the rotor shaft was tracked accurately, and a unified coordinate system was established on the rotor. Therefore, three-dimensional coordinates of instantaneously measured targets attached on the blade could be transformed to the unified rotor coordinate system, thereby providing a basis for consistently calculating the blade displacements at different test conditions. Moreover, location deviations of the blade caused by the vibration of the measuring system or the rotor due to freestream and rotor rotation were also effectively corrected through coordinate transformation. Comparisons of experimental and simulation results for a range of hover and forward flight conditions show good magnitude and trend agreements.
18
Zuo, Chenglin, Chunhua Wei, Jun Ma, Tingrui Yue, Lei Liu, and Zheyu Shi. "Full-Field Displacement Measurements of Helicopter Rotor Blades Using Stereophotogrammetry." International Journal of Aerospace Engineering 2021 (January 8, 2021): 1–18. http://dx.doi.org/10.1155/2021/8811601.
Abstract:
This study presents a stereophotogrammetry approach to achieve full-field displacement measurements of helicopter rotor blades. The method is demonstrated in the wind tunnel test of a 2 m diameter rotor, conducted at the 5.5 m × 4 m Aeroacoustic Wind Tunnel of China Aerodynamics Research and Development Center (CARDC). By arranging the retroreflective targets on the special hat installed directly above the rotor hub, the dynamic motion of the rotor shaft was tracked accurately, and a unified coordinate system was established on the rotor. Therefore, three-dimensional coordinates of instantaneously measured targets attached on the blade could be transformed to the unified rotor coordinate system, thereby providing a basis for consistently calculating the blade displacements at different test conditions. Moreover, location deviations of the blade caused by the vibration of the measuring system or the rotor due to freestream and rotor rotation were also effectively corrected through coordinate transformation. Comparisons of experimental and simulation results for a range of hover and forward flight conditions show good magnitude and trend agreements.
19
Choy, F. K., J. Padovan, and C. Batur. "Rub Interactions of Flexible Casing Rotor Systems." Journal of Engineering for Gas Turbines and Power 111, no. 4 (October 1, 1989): 652–58. http://dx.doi.org/10.1115/1.3240308.
Abstract:
Rub interactions between a rotor assembly and its corresponding casing structure has long been one of the major causes for machine failure. Fracture/fatigue failures of turbine impeller blade components may even lead to catastrophic consequences. This paper presents a comprehensive analysis of a complex rotor-bearing-blade-casing system during component rub interactions. The modal method is used in this study. Orthonormal coupled rotor-casing modes are used to obtain accurate relative motion between rotor and casing. External base vibration input and the sudden increase of imbalance are used to simulate suddenly imposed adversed operating condition. Nonlinear turbine/impeller blade effects are included with the various stages of single/multiple blade participation. A variable integration time step procedure is introduced to insure both accuracy and efficiency in numerical solutions. The dynamic characteristics of the system are examined in both the time domain and the frequency domain using a numerical FFT procedure. Nonlinear bearing and seal forces are also included to enhance a better simulation of the operating system. Frequency components of the system spectral characteristics will be correlated with the localized rub excitations to enable rub signature analysis. A multibearing flexible casing rotor system will be used as an example. Conclusions will be drawn from the results of an extensive parametric study.
20
Wen, Chuanmei, Zhimin Zhu, Xuezhong Fu, Tianliang Long, and Bing Li. "Dynamic Analysis of a Bolted Joint Rotor-Bearing System with a Blade–Casing Rubbing Fault." Processes 11, no. 8 (August 7, 2023): 2379. http://dx.doi.org/10.3390/pr11082379.
Abstract:
Bolted joints are widely used in aeroengine rotor systems to connect multiple components into an integrated structure and provide sufficient stiffness. The mechanical properties of a bolted joint have a significant effect on rotor dynamics. For modern aeroengine designs, the blade-tip clearance is gradually reduced to improve efficiency, which may lead to rubbing damage and affect safe operation. The mechanical properties of a bolted joint change significantly during the blade–casing rubbing process and influence the dynamic properties of the rotor system. Based on the finite element (FE) modeling method, a 15-node bolted joint rotor system model is established in this paper, in which the bolted joint is represented by a 2-node joint element, and the blade–casing rubbing force is considered. The Newmark method is used to solve the motion equations. The dynamic model is validated by comparing the frequency response characteristics for different numbers of blades with the results provided in other published studies. Based on the established model, the effects of the rotational speed, number of blades, and rubbing stiffness on the dynamic responses, normal rubbing forces, and bending stiffness of the bolted joint are evaluated by numerical simulation. The results show that the response amplitude and bending stiffness of the bolted joint change significantly under blade–casing rubbing faults, and the mean value of the vibration response deviates significantly from 0 as the number of blades increases. Meanwhile, the amplitude of the frequency component fVC and the maximum value of the normal rubbing force also increase as the number of blades increases. The main contribution of this paper is the establishment of a new model for a bolted joint rotor system, considering the time-varying bending stiffness of the bolted joint and the blade–casing rub fault, comparing the simulation results to obtain some general results bridging the current research gap. Meanwhile, the numerical results in this paper can provide a cognitive basis for the blade–casing rubbing fault mechanism of a bolted joint rotor system under the influence of speed, number of blades, and rubbing stiffness. The nonlinear dynamic characteristics observed in the present paper can be applied to the blade–casing rubbing fault diagnosis of turbomachines.
21
Wu, Fei, Jie Wu, Mei Jin, Fang Wang, and Ping Lu. "Influence of Gas-Liquid Distribution Inducer on Mass Transfer Coefficient in Rotating Packed Bed." Advanced Materials Research 908 (March 2014): 277–81. http://dx.doi.org/10.4028/www.scientific.net/amr.908.277.
Abstract:
Based on acetone-H2O system, the influence of the gas-liquid distribution inducer on the mass transfer coefficient in the rotating packed bed with the stainless steel packing was investigated. Furthermore, the absorption performance was also obtained under the experimental condition of the rotational speed of 630 rpm, the gas flow rate of 2 m3/h and the liquid flow rate of 100 L/h in the rotating packed bed with different types and different installation ways of the distribution inducer. The experimental results showed that the volumetric mass transfer coefficient Kyα per unit contact length of gas-liquid was increased by 8.6% for the forward-curved fixed blade, by 19.8% for the backward-curved rotor blade and by 33.2% with the combination of the straight radial rotor blade and the backward-curved fixed blade, respectively. Furthermore, when the gas flow rate was 2.5 m3/h, Kyα per unit contact length of gas-liquid was increased by 2.9% for the forward-curved fixed blade, by 25.3% for the backward-curved rotor blade, by 42.7% for the combination of the straight radial rotor blade and the backward-curved fixed blade, respectively. The results indicated that the distribution inducer play an important role on the improvement of the mass transfer coefficient in acetone-H2O system.
22
Lim, Joon W., Chee Tung, and Yung H. Yu. "Prediction of Blade-Vortex Interaction Airloads With Higher-Harmonic Pitch Controls Using the 2GCHAS Comprehensive Code." Journal of Pressure Vessel Technology 123, no. 4 (June 19, 2001): 469–74. http://dx.doi.org/10.1115/1.1401025.
Abstract:
Analytically predicted results of blade-vortex interaction (BVI) airloads, using the second- generation comprehensive helicopter analysis system (2GCHAS), are presented with the experimental results obtained from the higher-harmonic-control aeroacoustic rotor test (HART) program using a 40-percent, Mach-scaled model of the hingeless BO-105 main rotor. Correlations include airloads, blade tip deflections, and tip vortex geometry. The effects on blade airload predictions are studied with higher-harmonic pitch controls (HHC). It was concluded that the blade torsional deflection and the wake system play a very important role in predicting BVI airloads.
23
Srinivasan, A. V., D. G. Cutts, H. T. Shu, D. L. Sharpe, and O. A. Bauchau. "Structural Dynamics of a Helicopter Rotor Blade System." Journal of the American Helicopter Society 35, no. 1 (January 1, 1990): 75–85. http://dx.doi.org/10.4050/jahs.35.75.
24
Abubakar Mas’ud, Abdullahi, Ahmad Jamal, Surajuddeen Adewusi, and Arunachalam Sundaram. "Rotating blade faults classification of a rotor-disk-blade system using artificial neural network." International Journal of Power Electronics and Drive Systems (IJPEDS) 12, no. 3 (September 1, 2021): 1900. http://dx.doi.org/10.11591/ijpeds.v12.i3.pp1900-1911.
Abstract:
<span lang="EN-US">In this paper, the artificial neural network (ANN) has been utilized for rotating machinery faults detection and classification. First, experiments were performed to measure the lateral vibration signals of laboratory test rigs for rotor-disk-blade when the blades are defective. A rotor-disk-blade system with 6 regular blades and 5 blades with various defects was constructed. Second, the ANN was applied to classify the different </span><em><span lang="EN-US">x</span></em><span lang="EN-US">- and </span><em><span lang="EN-US">y</span></em><span lang="EN-US">-axis lateral vibrations due to different blade faults. The results based on training and testing with different data samples of the fault types indicate that the ANN is robust and can effectively identify and distinguish different blade faults caused by lateral vibrations in a rotor. As compared to the literature, the present paper presents a novel work of identifying and classifying various rotating blade faults commonly encountered in rotating machines using ANN. Experimental data of lateral vibrations of the rotor-disk-blade system in both </span><em><span lang="EN-US">x</span></em><span lang="EN-US">- and </span><em><span lang="EN-US">y</span></em><span lang="EN-US">-directions are used for the training and testing of the network.</span>
25
Eggers,, A. J., R. Digumarthi, and K. Chaney. "Wind Shear and Turbulence Effects on Rotor Fatigue and Loads Control." Journal of Solar Energy Engineering 125, no. 4 (November 1, 2003): 402–9. http://dx.doi.org/10.1115/1.1629752.
Abstract:
The effects of wind shear and turbulence on rotor fatigue and loads control are explored for a large horizontal axis wind turbine in variable speed operation at wind speeds from 4 to 20 m/s. Two- and three-blade rigid rotors are considered over a range of wind shear exponents up to 1.25 and a range of turbulence intensities up to 17%. RMS blade root flatwise moments are predicted to be very substantially increased at higher wind shear, and resultant fatigue damage is increased by many orders of magnitude. Smaller but similar trends occur with increasing turbulence levels. In-plane fatigue damage is driven by 1P gravity loads and exacerbated by turbulence level at higher wind speeds. This damage is higher by one to two orders of magnitude at the roots of the three-blade rotor compared with the two-blade rotor. Individual blade pitch control of fluctuating flatwise moments markedly reduces flatwise fatigue damage due to this source, and, to a lesser degree, the in-plane damage due to turbulence. The same is true of fluctuating rotor torque moments driven by turbulence and transmitted to the drive train. Blade root moments out of the plane of rotation aggregate to create rotor pitching and yawing moments transmitted to the turbine structure through the drive train to the yaw drive system and the tower. These moments are predicted to be relatively insensitive to turbulence level and essentially proportional to the wind shear exponent for the two-blade rotor. Fluctuating moments are substantially reduced with individual blade pitch control, and addition of a teeter degree-of-freedom should further contribute to this end. Fluctuating pitching and yawing moments of the three-blade rotor are substantially less sensitive to wind shear, more sensitive to turbulence level, and substantially lower than those for the two-blade rotor. Mean rotor torque and, hence, power are essentially the same for both rotors, independent of wind shear, and are somewhat reduced with individual blade pitch control of fluctuating flatwise moments. The same is true of mean rotor thrust; however fluctuations in rotor thrust are substantially reduced with individual blade pitch control.
26
Rahmanto, Bayu, Ferry Setiawan, and Edi Sofyan. "Perancangan Aktivitas Pemeliharaan dengan Metode Reliability pada Sistem Main Rotor Blade Helikopter BELL 412EP Studi Kasus Penerbad Semarang." Journal of Applied Mechanical Engineering and Renewable Energy 2, no. 1 (February 28, 2022): 9–15. http://dx.doi.org/10.52158/jamere.v2i1.243.
Abstract:
BENGPUSPENERBAD is a central workshop specifically owned by the Indonesian Army in Semarang, where aircraft and helicopters are subject to preventive and corrective maintenance. During the period 2018-2020 the BELL 412 EP helicopters often experienced unscheduled maintenance which resulted in losses resulting in flight failure, this was due to a malfunction in the Main Rotor Blade system. The malfunction of the Main Rotor Blade system is dominated by the hub component, namely on the shaft associated with Crack, Noise and Burn damage, and blade components, namely Corrosions, Nicks, Scratches, Dents, Deformation Holes and Crack. Therefore, the aim of this study is to eliminate failure system and unscheduled maintenance.
To eliminate failure and unscheduled maintenance, the authors perform an analysis with the FMEA method and calculate using the distribution method, then design the appropriate activities on the system. The data used for analysis are qualitative and quantitative data, where the authors use data from Time To Failure (TTF) and Time To Repair (TTR).
According to calculations using the current distribution we found that the Main Rotor Blade system was on time during the 200 operational flight hours, for which the reliability figure was 0.70. Maintenance activities in accordance with the operational conditions of the main rotor blade operating system are preventive maintenance with activities for tool preparation, inspection or chek, dismantling and servicing, and finally installation and finishing activities.
27
Awal, Ziad Bin Abdul, and Mohd Shariff bin Ammoo. "A Case Study on the Air Flow Characteristics of the Hirobo-FALCON 505 Controllable Helicopter's Main Rotor Blade." Applied Mechanics and Materials 527 (February 2014): 39–42. http://dx.doi.org/10.4028/www.scientific.net/amm.527.39.
Abstract:
The aerodynamics of the helicopter rotor is one of the most elating and exigent tribulations faced by the aerodynamicists today. Study through flow visualization process plays a key role in understanding the airflow distinctiveness and vortex interaction of the helicopter main rotor blade. Inspecting and scrutinizing the effects of wake vortices during operation is a great challenge and imperative in designing effective rotor system. This study aimed to visualize the main rotor airflow pattern of the Hirobo-FALCON 505 controllable subscale helicopter and seek for the vortex flow at the blade tip. The experimental qualitative data is correlated with quantitative data to perform scrupulous study on the airflow behavior and characteristics along with its distinctiveness spawned by the main rotor blade. Simulation using design software is performed in analogous stipulations to endow with comparability between the flow visualization results. Throughout the blade span several dissimilar flow patterns have been identified. The main rotor hub has turbulent flow at its center due to low energy of air amassed in this region whereas in the middle portion of the rotor blade, the air encompasses high kinetic energy with a clear straight streamline pattern.
28
Sekula, Martin K., and Matthew L. Wilbur. "Analysis of a Multiflap Control System for a Swashplateless Rotor." Journal of the American Helicopter Society 57, no. 3 (July 1, 2012): 1–12. http://dx.doi.org/10.4050/jahs.57.032006.
Abstract:
An analytical study was conducted examining the feasibility of a swashplateless rotor controlled through two trailing-edge flaps (TEFs), where the cyclic and collective controls were provided by separate TEFs. This analysis included a parametric study examining the impact of various design parameters on TEF deflections. Blade pitch bearing stiffness; blade pitch index; and flap chord, span, location, and control function of the inboard and outboard flaps were systematically varied on a utility-class rotorcraft trimmed in steady level flight. Gradient-based optimizations minimizing flap deflections were performed to identify single- and two-TEF swashplateless rotor designs. Steady, forward flight analysis suggest that a two-TEF swashplateless rotor where the outboard flap provides cyclic control and inboard flap provides collective control can reduce TEF deflection requirements without a significant impact on power, compared to a single-TEF swashplateless rotor design.
29
Krott, Matthew J., Edward C. Smith, and Christopher D. Rahn. "Modeling and Testing of Fluidic Flexible Matrix Composite Lead–Lag Dampers." Journal of the American Helicopter Society 65, no. 1 (January 1, 2020): 1–10. http://dx.doi.org/10.4050/jahs.65.012012.
Abstract:
A new lead–lag damper concept using a fluidic flexible matrix composite (F2MC) tube is presented in this paper. A model is developed for an articulated rotor blade integrated with an F2MC damper consisting of an F2MC tube, an inertia track, an orifice, and a hydraulic accumulator. Benchtop tests using a 4.5-ft rotor blade demonstrate the performance of a smallscale F2MC damper. The blade–damper system model predictions are verified by comparing experimentally measured and model-predicted frequency response data. In benchtop tests, the model predicts blade damping ratios of up to 0.34 with the F2MC damper. A simplified articulated blade based on the UH-60 rotor is simulated to assess the feasibility of a full-scale F2MC damper. Simulation results predict that the damper can generate blade damping ratios of over 0.30 at low blade lag angles.
30
Weiss, Felix, and Christoph Kessler. "Load prediction of hingeless helicopter rotors including drivetrain dynamics." CEAS Aeronautical Journal 12, no. 2 (February 3, 2021): 215–31. http://dx.doi.org/10.1007/s13272-020-00483-6.
Abstract:
AbstractIn contrast to analyses with constrained hub speed, the present study includes the dynamic response of coupled rotor-drivetrain modes in the aeromechanic simulation of rotor blade loads. The structural model of the flexible Bo105 rotor-drivetrain system is coupled to aerodynamics modeled by an analytical formulation of unsteady blade element loads combined with a generalized dynamic wake or a free wake, respectively. For two flight states, i. e. cruise flight and large blade loading, a time-marching autopilot trim of the rotor-drivetrain system in wind tunnel configuration is performed. The simulation results are compared to those of a baseline case with constant rotor hub speed. The comparison reveals a major change in the blade passage frequency harmonics of the lead-lag loads. Beside the full drivetrain model, reduced models are shown to accurately represent the drivetrain influence on blade loads, if the eigenfrequency of the coupled second collective lead-lag/drivetrain mode is properly predicted. In a sensitivity analysis, this eigenfrequency is varied by stiffness modification of a reduced drivetrain model. The resulting changes in blade loads are correlated to this eigenfrequency, which serves as a simple though accurate classification of the drivetrain regarding its influence on vibratory blade loads. Finally, the potential to improve lead-lag load predictions by application of a drivetrain model is demonstrated through the comparison of simulated loads with measurements from a wind tunnel test.
31
Alam, M., and H. D. Nelson. "A Blade Loss Response Spectrum for Flexible Rotor Systems." Journal of Engineering for Gas Turbines and Power 107, no. 1 (January 1, 1985): 197–204. http://dx.doi.org/10.1115/1.3239683.
Abstract:
A shock spectrum procedure is developed to estimate the peak displacement response of linear flexible rotor-bearing systems subjected to a step change in unbalance (i.e., a blade loss). A progressive and a retrograde response spectrum are established. These blade loss response spectra are expressed in a unique non-dimensional form and are functions of the modal damping ratio and the ratio of rotor spin speed to modal damped whirl speed. Modal decomposition using complex modes is utilized to make use of the unique feature of the spectra for the calculation of the peak blade loss displacement response of the rotor system. The procedure is applied to three example systems using several modal superposition strategies. The results of each are compared to true peak displacements obtained by a separate transient response program.
32
Ignatkin, Yurii M., Pavel V. Makeev, and Alexander I. Shomov. "CALCULATED RESEARCH OF INFLUENCE OF HELICOPTER MAIN ROTORS GEOMETRY ON THE EFFICIENCY IN HOVER MODE BASED ON THE NONLINEAR VORTEX MODEL." Civil Aviation High TECHNOLOGIES 21, no. 6 (December 26, 2018): 43–53. http://dx.doi.org/10.26467/2079-0619-2018-21-6-43-53.
Abstract:
The efficiency of the helicopter main rotor in the hover mode is very important, because this mode essentially determines the performance characteristics of the helicopter. A feature of the helicopter rotor aerodynamics is a significant inductive blade influence that highly defines its aerodynamic characteristics. The problem of the influence of the blade twist and spatial geometric layout of the main rotor on its aerodynamic characteristics in the hover mode for a fixed value of the rotor solidity has been considered in this article. As a criterion of efficiency of the rotor in the hover mode relative efficiency (FoM – Figure of Merit) is used. The results are obtained by numerical simulation based on the nonlinear vortex blade model of the rotor, developed at the Helicopter Design Chair of the MAI. The model allows taking into account a complicated spatial shape of the free vortex path of the rotor blades that determines their inductive interaction. As the example of a four-blade main rotor with rectangular blades in plan, the influence of the value of the blades twist on the efficiency in the hover mode is studied. For different values of the rotor thrust, the values and ranges of the blade twist angles are determined, providing the maximum positive effect of the efficiency increase in hovering. For a fixed value of the blade twist, the rotor solidity, and the same operating conditions, the effect of various schemes and configurations of rotor on its efficiency in hover mode is studied. A single rotor with a different number of blades (from 2 to 6), an X-shaped rotor, coaxial rotor and rotor with crossed blades type "synchropter" are considered. The values of the efficiency increase in hovering depending on the rotor layout in comparison with the two-blade rotor are obtained. The comparative analysis of inductive velocities and streamlines for the "synchropter" rotor scheme, coaxial rotor scheme and its equivalent single rotor scheme is presented. The obtained results can be useful at the stage of preliminary design of vertically taking-off aircraft when selecting the parameters of their main rotor system.
33
Гребеников, А. Г., Ю. В. Дьяченко, В. В. Коллеров, В. Ю. Коцюба, И. В. Малков, В. А. Урбанович, and И. А. Воронько. "АНАЛІЗ КОНСТРУКТИВНО-ТЕХНОЛОГІЧНИХ ОСОБЛИВОСТЕЙ ЛОПАТЕЙ НЕСУЧИХ ГВИНТІВ ВАЖКИХ ТРАНСПОРТНИХ ВЕРТОЛЬОТІВ." Open Information and Computer Integrated Technologies, no. 93 (November 19, 2021): 59–103. http://dx.doi.org/10.32620/oikit.2021.93.04.
Abstract:
The analysis of the design and technological features of the rotor blades of heavy transport helicopters is carried out. The main performance characteristics of heavy helicopters are presented. General requirements to helicopter main rotor blades design and specifications for their production are formulated. The design and force diagram of heavy helicopter main rotor blades is considered. The features of structural materials for the main rotor blades of heavy transport helicopters are marked. The main rotor blades differ in their design due to different approaches to materials, manufacturing and layout of blade elements. The main rotor blades of an all-metal design, for design and technological reasons, are divided into two groups: a frame structure with a tubular steel spar and an aluminum extruded spar. As a result of a number of design and technological measures the service life of the main rotor blade of helicopter Mi-6 was brought from 50 hours to 1500 hours. The principal peculiarity of the steel tubular spar of the main rotor blade of the Mi-26 helicopter is the absence of the shaft lug. The features of mixed design main rotor blades are presented. The method of parametric modeling of helicopter main rotor blades is presented. The application of the three-dimensional parametric models of structural elements in practice of designing and construction enables to perform numerical calculations of aerodynamic and strength characteristics both of separate aggregates, units and details and of the helicopter as a whole by means of the finite element method. The method of parametric modeling of the main rotor blade of the transport helicopter with the computer system CATIA V5 is a modification of the method of integrated designing of the elements of aviation constructions. Parametric master geometry of the main rotor blade is a linear surface, created by basic profiles of the blade. On the basis of parametric master geometry a space distribution model is created that determines the position of axial planes of the power set of the blade for further creation of the blade detail models. Technological flowchart of main rotor blade manufacturing is presented, manufacturing and surface hardening technology of steel tubular spar is considered. The technology of manufacturing and molding the nose part of the blade of the main rotor mixed design. The technological features of slipway assembly-gluing of the main rotor blade are considered, the content of off-slipway work is given.These materials can be useful in theoretical and experimental studies to extend the service life of the rotor blades of Mi-26 helicopters, which are currently in operation in Ukraine.
34
Coton, F. N., R. A. McD Galbraith, T. Wang, and S. J. Newman. "A wind-tunnel based study of helicopter tail rotor blade vortex interaction." Aeronautical Journal 108, no. 1083 (May 2004): 237–44. http://dx.doi.org/10.1017/s0001924000005091.
Abstract:
AbstractThe interaction of a helicopter tail rotor blade with the tip vortex system from the main rotor is a significant source of noise and, in some flight states, can produce marked reductions in control effectiveness. This paper describes a series of wind-tunnel tests to simulate tail rotor blade vortex interaction with a view to providing data for the development and validation of numerical simulations of the phenomenon. In the experiments, which were carried out in the Argyll wind-tunnel of Glasgow University, a single-bladed rotor located in the tunnel’s contraction was used to generate the tip vortex which travelled downstream into the working section where it interacted with a model tail rotor. The tail rotor was instrumented with miniature pressure transducers that measured the aerodynamic response during the interaction. The results suggest that the rotor blade vortex interaction is similar in form to that measured at much higher spatial resolution on a fixed, non-rotating blade. The combination of the two datasets, therefore, provides a valuable resource for the development and validation of predictive schemes.
35
Mwanyika, Hegespo H., Yusufu AC Jande, and Thomas Kivevele. "Design and Performance Analysis of Composite Airfoil Wind Turbine Blade." Tanzania Journal of Science 47, no. 5 (December 1, 2021): 1701–15. http://dx.doi.org/10.4314/tjs.v47i5.18.
Abstract:
Abstract
Small horizontal axis wind turbine rotors with composite airfoil rotor blades were designed and investigated in the present study in order to improve its performance in low wind speed and low Reynolds number (Re) conditions for standalone system. The geometrical and aerodynamic nature of a single airfoil small horizontal axis wind turbine blade curtails efficient energy harnessing of the rotor blade. The use of composite airfoil rotor blade improves energy production but imposes uncertainty in determining an optimal design angle of attack and the off design aerodynamic behaviour of the rotor. This research investigated the effects of two airfoils used at different sections in a composite blade and determined the blade’s optimal design angle of attack for maximum power generation. The wind turbine rotor blades were designed using blade element momentum (BEM) method and modelled by SolidWorks software. The SG6042 and SG6043 airfoils were used for the composite airfoil blades. Five wind turbines were designed with rotor blades of design angles of attack from 3° to 7°. The five wind turbine blades were simulated in computational fluid dynamics to determine the optimal design angle of attack. The composite airfoil wind turbine blade showed improved performance, whereas, the wind power generated ranged from 4966 W to 5258 W and rotor power coefficients ranged from 0.443 to 0.457. The blade with design angle of attack of 6° showed highest performance.
Keywords: composite airfoil, lift-to-drag ratio, pressure coefficient, Reynolds number, design angle of attack.
36
Chiu, Yi-Jui, and Shyh-Chin Huang. "The Influence of a Mistuned Blade’s Staggle Angle on the Vibration and Stability of a Shaft-Disk-Blade Assembly." Shock and Vibration 15, no. 1 (2008): 3–17. http://dx.doi.org/10.1155/2008/714346.
Abstract:
The influence on coupling vibrations and stability among shaft-torsion, disk-transverse and blade-bending of a rotor system with a mistuned blade's staggle angle was investigated analytically. A shaft-disk-blade system has been found existing two types of coupling vibrations, disk-blade (DB), and blade-blade (BB) modes when the shaft was assumed rigid. If the shaft's torsional flexibility was taken into account, an additional type of coupling modes, shaft-disk-blade (SDB), appeared. When an angle-mistuned blade existed, the blades periodicity was destroyed and it was found to change not only the natural frequencies but also the types of modes. Due to blade's mistune, the shaft torsion had to participate to balance such that DB modes vanished and replaced by SDB modes. A mistuned staggle angle was numerically found to alter the natural frequencies in an almost linear trend. At last, the rotational effects were found to merge frequency loci and eventually reached an instability point. Very interestingly, a mistuned blade diminished the possible instability caused by blade-dominating modes, which existed in a perfect and periodic rotor. In words, the rotor might benefit from a mistuned blade from the stability viewpoint. The shaft-dominating mode, yet, was unaffected by the mistune and retained a possible instability.
37
Prasad, Damarla Kiran, Kavuluri Venkata Ramana, and Nalluri Mohan Rao. "Weight Function Approach for Semi Elliptical Crack at Blade Mounting Locations in Steam Turbine Rotor System." Periodica Polytechnica Mechanical Engineering 62, no. 3 (April 6, 2018): 203–8. http://dx.doi.org/10.3311/ppme.11604.
Abstract:
This paper presents analysis of stress intensity factors at blade mounting locations of steam turbine rotor system. General expressions for the stresses induced in a rotating disc are derived and these equations are applied to steam turbine rotor disc. It is observed that the radial stress increases instantly at blade mounting location which indicates the probability of crack initiation and growth. A semi elliptical crack is considered at that location and weight function approach is used to determine the stress intensity factors. The results are validated with the influence coefficient approach. The differences of present approach with influence coefficient approach are less than 3 %. Hence the present approach is suitable for determination of stress intensity factors in a semi elliptical crack at blade mounting locations of a steam turbine rotor disc.
38
Bauknecht, Andŕe, Xing Wang, Jan-Arun Faust, and Inderjit Chopra. "Wind Tunnel Test of a Rotorcraft with Lift Compounding." Journal of the American Helicopter Society 66, no. 1 (January 1, 2021): 1–16. http://dx.doi.org/10.4050/jahs.66.012002.
Abstract:
Rotorcraft flight speed is limited by compressibility effects on the advancing blade side and decreasing lift potential on the retreating blade side. It may thus be beneficial to employ a hingeless rotor to generate additional lift with the advancing blade and compensate the resulting rolling moment with a fixed wing on the retreating blade side. This concept is a form of "lift compounding" that appears to show enormous potential. The present paper presents results of a wind tunnel test with a slowed, hingeless rotor and single fixed wing on the retreating blade side. Based on rotor test stand data and flow field measurements, the impact of operational and rotor parameters on system performance and aerodynamics is examined, mutual interaction effects between rotor and fixed wing are analyzed, and dominant flow structures are characterized in the reverse flow region on the retreating blade side. Flow field analysis reveals a reverse flow entrance vortex that freely convects through the reverse flow region and rivals the blade tip vortices in strength. Contrary to previous beliefs, this vortex originates from upstream of the reverse flow region and only its detachment from the rotor blade is related to entering this region. The combination of finite rolling moment trim and aft shaft tilt significantly increases rotor lift coefficient and corresponding peak lift-to-drag ratio of the compound rotorcraft. Results are compared with predictions from a comprehensive rotor analysis that is expanded to cover the main effects of the added fixed wing and is able to reproduce general performance trends of the rotorcraft. The present study highlights that adding a single fixed wing and hingeless rotor to a high-speed rotorcraft could significantly improve its performance.
39
Roy, Arunabha M. "Finite Element Framework for Efficient Design of Three Dimensional Multicomponent Composite Helicopter Rotor Blade System." Eng 2, no. 1 (March 1, 2021): 69–79. http://dx.doi.org/10.3390/eng2010006.
Abstract:
In the present study, a three-dimensional finite element framework has been developed to model a full-scale multilaminate composite helicopter rotor blade. Tip deformation and stress behavior have been analyzed for external aerodynamic loading conditions and compared with the Abaqus FEA model. Furthermore, different parametric studies of geometric design parameters of composite laminates are studied in order to minimize tip deformation and maximize the overall efficiency of the helicopter blade. It is found that these parameters significantly influence the tip deformation characteristic and can be judiciously chosen for the efficient design of the rotor blade system.
40
Wang, Xing, Wen Li, Xuehui Zhang, Yangli Zhu, Wei Qin, and Haisheng Chen. "Flow characteristic of a multistage radial turbine for supercritical compressed air energy storage system." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 6 (December 15, 2017): 622–40. http://dx.doi.org/10.1177/0957650917743366.
Abstract:
Compressed air in supercritical compressed air energy storage system expand from supercritical to atmospheric conditions at lower inlet temperature (<500 K) to generate MW scale power. Therefore, a new multistage radial turbine is adopted and the flow characteristic is investigated by numerical simulation. Effects of ideal gas model and tip clearance on the performance and flow field of the multistage turbine are revealed. Results show that ideal gas model can reveal flow pattern under supercritical condition correctly while leading to obvious deviation of isentropic enthalpy drop, entropy, and inlet-to-exit total temperature ratio. Relative differences for mass flow and efficiency are less than 2%, while the relative differences for output power reaches to 9.36%. For shrouded rotor, mixing of working fluid near hub, blade suction surface, and shroud is the main influencing factor of the flow loss in the rotor. For unshrouded rotor, leakage vortex promote mixture of the fluid deriving from the hub, shroud, and suction surface, and causes much higher flow loss in the channel of rotor. The rotors, which have higher blade height variation rate, present higher efficiency reduction when the tip clearance height is increased, which is because the proportion of tip clearance in blade inlet height increases with the increase of average aspect ratio, resulting in the increase of leakage flow at the leading edge of rotor blade. The pressure fluctuation near the tip clearance and efficiency reduction is also increased. The present study provides a reference for further design and optimization of the multistage radial turbines in compressed air energy storage.
41
Cameron, Christopher, Jayant Sirohi, Joseph Schmaus, and Inderjit Chopra. "Performance and Loads of a Reduced-Scale Coaxial Counterrotating Rotor." Journal of the American Helicopter Society 64, no. 4 (October 1, 2019): 1–15. http://dx.doi.org/10.4050/jahs.64.042003.
Abstract:
The results of hover and wind tunnel tests of a reduced-scale, closely spaced, rigid, coaxial counterrotating rotor system are presented, along with results from a comprehensive analysis. The system features two-bladed upper and lower rotors, 2.03 m in diameter, with uniform section, untwisted rotor blades. Measurements include upper and lower rotor steady and vibratory hub loads, as well as control angles and control loads. Blade tip clearance was measured using an optical sensor. The rotor system was tested in hover and at advance ratios between 0.21 and 0.53, at collective pitches ranging from 2° to 10° achieving blade loadings in excess of 0.10. At each forward flight operating condition, sweeps of lift offset up to 20% were performed, while selected test conditions were repeated at different rotor speeds and interrotor index angles. Hover tests showed that aerodynamic interaction between upper and lower rotors decreased individual rotor performance compared to isolated rotors and induced a four-per-revolution vibratory load corresponding to the blade passage frequency. In forward flight, the rotor effective lift-to-drag ratio was found to increase with increasing advance ratio and lift offset, resulting in a 30% improvement at 20% lift offset and 0.5 advance ratio. The lower coaxial rotor was found to operate at higher lift-to-drag ratio than the upper rotor, in contrast to the behavior in hover. Lift offset resulted in a decrease in blade tip clearance with a corresponding increase in rotor side force. Vibratory loads increased with advance ratio, with the largest loads in the two- and four-per-revolution harmonics. Lift offset, in conjunction with interrotor index angle, is shown to modify vibratory forces and moments transmitted to the fixed frame, increasing some force components while decreasing others.
42
Chen, T. Y., C. W. Hung, and Y. T. Liao. "Experimental Study on Aerodynamics of Micro-Wind Turbines with Large-Tip non-Twisted Blades." Journal of Mechanics 29, no. 3 (May 14, 2013): N15—N20. http://dx.doi.org/10.1017/jmech.2013.35.
Abstract:
AbstractThis research experimentally investigates the rotor aerodynamics of horizontal-axis, micro-wind turbines. Specifically, the aerodynamic characteristics of large-tip, non-twisted blades are studied. The study is conducted in a wind tunnel system to obtain the relations between the power coefficient (CP) and tip speed ratio (TSR), the torque coefficient (CT) and TSR. Effects of rotor position inside a flanged diffuser, rotor solidity and blade number on rotor performance are investigated. The blade cross-section is NACA4415 airfoil. The pitch angle of the blades is fixed at 30°, and the chord length ratio between the blade root and tip (Cr / Ct) is fixed at 0.3. Results show that larger power output is obtained when the rotor placed closer to the diffuser inlet. The 60%-solidity rotor, in general, achieves better power and torque outputs among the test rotor solidities. The higher the blade number is, the larger the power output is, but the difference is small. Comparisons between the present and previous relatively short-tip blades (Cr / Ct = 0.5) show that the present blades have better power and torque outputs at lower rotor rotational speed. These results suggest that the large-tip blades are suitable for micro-wind turbine applications, and make rotor-generator matching more flexible.
43
El-Oun, Z. B., and J. M. Owen. "Preswirl Blade-Cooling Effectiveness in an Adiabatic Rotor–Stator System." Journal of Turbomachinery 111, no. 4 (October 1, 1989): 522–29. http://dx.doi.org/10.1115/1.3262303.
Abstract:
Blade-cooling air for a high-pressure turbine is often supplied from preswirl nozzles attached to a stationary casing. By swirling the cooling air in the direction of rotation of the turbine disk, the temperature of the air relative to the blades can be reduced. The question addressed in this paper is: Knowing the temperatures of the preswirl and disk-cooling flows, what is the temperature of the blade-cooling air? A simple theoretical model, based on the Reynolds analogy applied to an adiabatic rotor–stator system, is used to calculate the preswirl effectiveness (that is, the reduction in the temperature of the blade-cooling air as a result of preswirling the flow). A mixing model is used to account for the “contamination” of the blade coolant with disk-cooling air, and an approximate solution is used to estimate the effect of frictional heating on the disk-cooling air. Experiments were conducted in a rotor–stator rig that had preswirl nozzles in the stator and blade-cooling passages in the rotating disk. A radial outflow or inflow of disk-cooling air was also supplied, and measurements of the temperature difference between the preswirl and blade-cooling air were made for a range of flow rates and for rotational Reynolds numbers up to Reθ = 1.8 × 106. Considering the experimental errors in measuring the small temperature differences, good agreement between theory and experiment was achieved.
44
Ng, W. F., and A. H. Epstein. "Unsteady Losses in Transonic Compressors." Journal of Engineering for Gas Turbines and Power 107, no. 2 (April 1, 1985): 345–53. http://dx.doi.org/10.1115/1.3239727.
Abstract:
A newly developed probe has been used to measure the time-resolved total temperature and pressure in a transonic compressor. The investigation revealed the presence of large fluctuations in the blade-to-blade core flow occurring at a frequency of three to four times blade passing. These variations are not steady in the rotor relative frame and are thought to be caused by unsteadiness in the rotor shock system, driven perhaps by a shed vortex in the blade wake. The loss associated with this unsteadiness is calculated and the implications for stage performance are discussed.
45
Abdelrhman, Ahmed M., M. Salman Leong, Lim Meng Hee, and Wai Keng Ngui. "Application of Wavelet Analysis in Blade Faults Diagnosis for Multi-Stages Rotor System." Applied Mechanics and Materials 393 (September 2013): 959–64. http://dx.doi.org/10.4028/www.scientific.net/amm.393.959.
Abstract:
Blade fault is one of the most common faults in turbomachinery. In this article, a rotor system which consists of multiple stages of blades was developed. A variety of blade fault conditions were investigated and its vibration responses were measured. The feasibility of wavelet analysis for multi-stages blade fault diagnosis was tested using simulated signals as well as experimental data. The use of wavelet analysis as the tool to detect multi stages blade faults was studied. Some probable solutions to improve multi stages blade fault diagnosis by wavelet analysis were also suggested.
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Ma, Hui, Fanli Yin, Zhiyuan Wu, Xingyu Tai, and Bangchun Wen. "Nonlinear vibration response analysis of a rotor-blade system with blade-tip rubbing." Nonlinear Dynamics 84, no. 3 (December 29, 2015): 1225–58. http://dx.doi.org/10.1007/s11071-015-2564-5.
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Lee, Hwanhee, Ji-Seok Song, Seog-Ju Cha, and Sungsoo Na. "Dynamic response of coupled shaft torsion and blade bending in rotor blade system." Journal of Mechanical Science and Technology 27, no. 9 (September 2013): 2585–97. http://dx.doi.org/10.1007/s12206-013-0702-x.
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Mingfu, Liao, Song Mingbo, and Wang Siji. "Active Elastic Support/Dry Friction Damper with Piezoelectric Ceramic Actuator." Shock and Vibration 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/712426.
Abstract:
The basic operation principle of elastic support/dry friction damper in rotor system was introduced and the unbalance response of the rotor with elastic support/dry friction damper was analyzed theoretically. Based on the previous structure using an electromagnet as actuator, an active elastic support/dry friction damper using piezoelectric ceramic actuator was designed and its effectiveness of reducing rotor vibration when rotor traverses its critical speed and blade-out event happened was experimentally verified. The experimental results show that the active elastic support/dry friction damper with piezoelectric ceramic actuator can significantly reduce vibration in rotor system; the vibration amplitude of the rotor in critical speed region decreased more than 2 times, and the active damper can protect the rotor when a blade-out event happened, so the rotor can traverse the critical speed and shut down smoothly. In addition, the structure is much simpler than the previous, the weight was reduced by half and the power consumption was only 5 W.
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Kingan, Michael J., Riul Jung, and Ryan S. McKay. "Contra-rotating rotor noise reduction methods." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 6 (November 30, 2023): 2218–24. http://dx.doi.org/10.3397/in_2023_0327.
Abstract:
This paper describes an experimental and numerical investigation into the tones produced by a contra-rotating rotor system for use on small unmanned aerial vehicles. The effect of changing the blade shape and the diameter of the lower rotor is investigated and it is shown that different blade geometries can be used to significantly reduce tone noise levels. The numerical simulations are validated against the experimental measurements.
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Kumar, K. Ramesh, and M. Selvaraj. "Review on Energy Enhancement Techniques of Wind Turbine System." Advances in Science and Technology 106 (May 2021): 121–30. http://dx.doi.org/10.4028/www.scientific.net/ast.106.121.
Abstract:
Wind energy is the quickest growing sustainable energy resource in present energy crisis scenario. It has been considered as one of the most viable sources of environmental friendly energy. Starting investment cost of the wind turbine plant is exorbitant. Moreover, production cost of the wind turbine blade is about 20% of the wind turbine plant cost. It is fundamental to decrease the life-cycle cost of wind turbine plant by efficient utilization available wind speed. Optimized diffuser (Convergent divergent type and Convergent type) has been developed with highest possible pressure difference between inlet and exit of shroud, Area Ratio of inlet to exit section, wall length, incident angle and various flow qualities to enhance the available wind velocity considerably. The suitable tiny riblets on external layer of turbine blade have been introduced to lessen the skin friction drag force. Moreover, dual rotor blade with various rotor sizes for primary and secondary rotor, direction of rotor rotation, separation distance between them has been studied to augment wind turbine power generation and improvement in cut-in-speed. Moreover, comparative study will be conducted with standard (bare) wind turbine. Based on the above features, available wind speed increased significantly. In addition, various experiments and CFD analysis work still to be done to assess Diffuser based Wind Turbine model which is much closer to realistic product with available interaction. Due to the above additional features of the turbine system, the utilization of wind speed gets augmented with greater power production.