Set Of Blades Research Articles

Experimental Study on a Model of a Commercial Windpumping Rotor

This paper describes the experimental determination of performance and torque characteristics of the Jober commercial low-solidity, fast-running wind rotor for direct driven wind-pumping applications. A scale model of the Jober wind rotor is tested at different blade setting angles to determine the best configuration. The optimal configuration lies within a range of blade pitch angles between 45° and 30°. The performance of the rotor is also compared to a newly designed, more aerodynamic rotor based on the theory of wind rotors. It is shown that an aerodynamic design for the rotor can be used in water pumping applications, which shows improved performance when compared to the original commercial design. The overall wind-to-water conversion efficiency is analyzed theoretically and the results show that there is a substantial improvement in the newly designed rotor configuration as compared to the actual configuration of the Jober windpump.

Effect of circular keratotomy on keratoconus

Circular keratotomy was performed in 3 eyes of 3 patients with keratoconus before planned lamellar keratoplasty. After peribulbar anesthesia, a circular 400 microm cut centered on the geometrical corneal center was made using a Hessburg-Barron 7.0 mm trephine (Altomed). The circular cut was deepened with a guarded diamond blade set at 90% of the thinnest point in the circumference and closed with a single 10-0 nylon running suture. Videokeratography revealed increased astigmatism and increased central curvature in all eyes. In 1 patient, a 0.2 improvement in best spectacle-corrected visual acuity (BSCVA) was noted, associated with overall corneal steepening. In the other 2 patients, refraction, BSCVA, and corneal profile worsened, requiring lamellar keratoplasty. Circular keratotomy increased corneal curvature and worsened keratoconus and is therefore not recommended.

Blades condition monitoring using shaft torsional vibration signals

PurposeThe purpose of this paper is to validate mathematically the feasibility of extracting the rotating blades vibration condition from the shaft torsional vibration measurement.Design/methodology/approachA mathematical model is developed and simulated for extracting rotating blades vibration signatures from the shaft torsional vibration signals. The model simulates n‐blades attached to a rigid disk at setting angles and the shaft drives the disk is flexible in torsion. The model is developed using the multi‐body dynamics approach in conjunction with the Lagrangian dynamics. A three‐blade rotor system example is simulated for blades free and forced vibration under stationary and rotating conditions. Frequency spectrums for the shaft torsional and blades bending vibration are represented and studied for analysis verification purposes.FindingsThe torsional vibration frequency spectrums showed blades free and forced vibration signatures. The blade setting angle is shown to reduce the sensitivity of torsional vibration signal to blades vibration signatures as it increases. The torsional vibration signals captured the variation in blades properties and produced broadband frequency components for mistuned system. The shaft torsional rigidity is shown to reduce the sensitivity of torsional vibration signal to blades vibration if increased to extremely high values (approaching rigid shaft). The rotor inertia is shown to have less effect on the torsional vibration signals sensitivity. The method of torsional vibration as a tool for rotating blades vibration measurement, based on the proposed mathematical model and its simulation, is feasible.Practical implicationsThere is a growing need for reliable predictive maintenance programs that in turn requires continuous development in methods for machinery health monitoring through vibration data collection and analysis. Turbo machinery and bladed assemblies like fans, marine propellers and wind turbine systems usually suffer from the problem of blades high vibration that is difficult to measure. The proposed new method for blades vibration measurement depends on the shaft torsional vibration signals and can be used also for verifying the signals from other types of bearings sensors for possible blades vibration condition monitoring.Originality/valueThis paper presents a unique mathematical model and simulation results for the rotating blades vibration monitoring. The developed model can be simulated for studying coupled blades vibration problems in the design stage as well as for condition monitoring in maintenance applications.

Model and Stability Analysis of a Flexible Bladed Rotor

This paper presents a fully bladed flexible rotor and outlines the associated stability analysis. From an energetic approach based on the complete energies and potentials for Euler-Bernoulli beams, a system of equations is derived, in the rotational frame, for the rotor. This later one is made of a hollow shaft modelled by an Euler-Bernoulli beam supported by a set of bearings. It is connected to a rigid disk having a rotational inertia. A full set of flexible blades is also modelled by Euler-Bernoulli beams clamped in the disk. The flexural vibrations of the blades as well as those of the shaft are considered. The evolution of the eigenvalues of this rotor, in the corotational frame, is studied. A stability detection method, bringing coalescence and loci separation phenomena to the fore, in case of an asymmetric rotor, is undertaken in order to determine a parametric domain where turbomachinery cannot encounter damage. Finally, extensive parametric studies including the length and the stagger angle of the blades as well as their flexibility are presented in order to obtain robust criteria for stable and unstable areas prediction.

2526 クロスフロー型風車における翼枚数および翼取付角が出力特性に及ぼす影響(S47-4 自然の流体エネルギー利用技衛(風車2),S47 自然の流体エネルギー利用技術)

A cross-flow wind turbine is driven by mainly drag force on its blades. For the performance of a cross-flow wind turbine, the number of blades and blade setting angle are important design parameters. So, we studied influences of these factors on the performance of the wind turbine by changing the number of blades and blade setting angle variously. 6, 8, 10, 12 and 16 blades of 5 cases for the number of blades and 30, 45, 60 and 90 degree of 4 cases for the blade setting angle were tested. 12 blade case and 45 degree blade setting angle case showed the almost highest performance coefficient and stable performance characteristic.

“Buzz-saw” noise: A comparison of measurement with prediction

Accurate prediction of “buzz-saw” noise in a turbofan inlet duct necessitates consideration of nonlinear acoustics, modelling a complete fan blade set, modelling an acoustic liner, and calculations at high frequencies. A recent series of papers has described new work concerning the application of one-dimensional propagation models to the prediction of buzz-saw noise. A numerical model, termed the frequency domain numerical solution or FDNS, has been developed. It can be used to calculate the nonlinear propagation of the rotor-alone pressure field in either a rigid or acoustically-lined inlet duct. From this the in-duct noise level of the buzz-saw tones can be determined. In previous work, validation of this method by comparison with in-duct noise measurements has been limited to rigid inlet ducts, because of the lack of availability of suitable measurements from lined ducts. In this article new measurements of buzz-saw noise in an acoustically-lined inlet duct are utilized. A comparison of measurements of buzz-saw noise in a lined inlet duct, and noise predictions from numerical simulations by the FDNS is presented. The detailed measurements reveal the effect of an acoustic liner on buzz-saw noise. The suitability of the numerical model to be used to provide realistic noise predictions for supersonic ducted fans is also examined.

Numerical Investigation of the Effects of the Clearance Gap Between the Inducer and Impeller of an Axial Blood Pump

A series of numerical models are generated to investigate the flow characteristics and performance of an axial blood pump. The pump model includes a straightener, an inducer-impeller, and diffuser. Numerical studies of the effects of angular alignment of the inducer and impeller blades and the axial clearance gap between the inducer and impeller are presented in this article. The pump characteristics derived from numerical simulation are validated with experimental data. Numerically simulated results showed a sinusoidal variation in the pressure generated across the pump with changes in angular alignment between the inducer and impeller. This is attributed to additional losses when flow is forced or diverted from the trailing edge of the inducer to either the pressure or suction side of the impeller blade when the alignment between the two sets of blades is not optimal. The pressure generated is a maximum when the impeller blades are at 0 or 30 degrees with respect to the inducer. The effect of rotating the impeller with respect to the inducer causes the sinusoidal pressure variation. In addition, it was observed that when the clearance gap between the inducer and impeller is reduced to 1 mm, the pressure generated is a minimum when compared to the other models. This is attributed to the interference between the inducer and impeller when the gap separating them is too small. The location of the maximum pressure on the pressure side of the impeller blade shifts upstream while its magnitude decreases for small clearance gap between the inducer and the impeller. There was no flow separation in the inducer while small regions of backflow are observed at the impeller trailing edge. Recommendations for future modifications and improvements to the pump design and model simulation are also given.

R&D on the power conversion system for gas turbine high temperature reactors

JAERI is conducting R&D on the power conversion system of the GTHTR300 plant, in parallel with plant design work. The design of the power conversion system is based on a regenerative, non-intercooled, closed Brayton cycle with helium gas as the working fluid. A single-shaft, axial-flow turbo-compressor and a directly coupled electric generator run on magnetic bearings. Major R&D issues for the power conversion system are aerodynamic performance of the helium gas compressor, high load capacity magnetic bearings and performance of magnetic bearing supported rotor, and operability and controllability of the closed-cycle gas turbine system. Three test plans were set up to address theses issues, aiming at verifying the design of the GTHTR300 power conversion system and establishing key technologies of a closed-cycle helium gas turbine system. The compressor aerodynamic performance test is aiming at verifying the aerodynamic performance and design method of the helium compressor. A 1/3-scale, four-stage compressor test model and a helium gas loop were designed and fabricated. The model was designed to simulate the repeating stage flow, and at the same time have satisfactorily high machining precision, Reynolds number and measurement accuracy. The helium gas operating pressure is varied to investigate the effects of the Reynolds number on the efficiency and surge margin. Two sets of blades were fabricated to evaluate the effects of the end-wall over-camber angle. Test results will provide the basis for further improvement in the GTHTR300 compressor design. The magnetic bearing development test is aiming at developing the technology of the magnetic bearing supported rotor system. The test rig composed of 1/3-scale turbo-compressor and generator rotor models that are connected together by a flexible coupling. Each rotor models are supported by two radial magnetic bearings with a high load capacity that is about 1/10 of the GTHTR300 design. The rotor models were designed so that both the critical speeds and vibration modes are matched to those of the actual rotors. A 1/3-scale test model of a turbo-machine rotor system and magnetic bearings were designed and fabrication of the test model was started. Testing of magnetic bearing performance, unbalance response, stability, and auxiliary bearing reliability will be carried out together with development of advanced control method in the program. The test will validate the design methods of the rotor system and magnetic bearing control system. The test will verify the rotor design of GTHTR300 and the results will identify technical issues in scaling up of magnetic bearings. The gas-turbine system operation and control test is aiming to demonstrate operability and controllability of the closed-cycle gas-turbine system. Preliminary design was made for the test facility that is an integrated scaled model of the GTHTR300 power conversion system. Pressurized helium gas at around 1 MPa is used as the working fluid, and an electric heater simulates the reactor. Planned test modes are normal operation, start-up, shutdown, load change, loss of load, and emergency shutdown. Specifications of the system operation and control were defined to fulfill the test requirements. The test will verify the design of the GTHTR300 control system and establish the operation and control method. Development and verification of a plant dynamics analysis code will be made based on the test results. Major components of the facility, such as a turbine, a heater, a recuperator, and a pre-cooler, were designed to meet the specifications. Preliminary transient analyses were made for the test facility design. It was confirmed from the results of the analyses that the test facility can be operated to meet the requirements of the test plan and controlled satisfactorily. A revision of the design is underway for purposes of the reduction in the power demands and the improvement in the control system. These scaled tests will surely validate the GTHTR300 power conversion system design and the results will be incorporated in the design in the upgrading stage. The R&D program as a whole will well demonstrate the technical feasibility of the high-efficiency gas-turbine system for high-temperature gas-cooled reactor plants.

A simple quantitative method for evaluation of angiogenesis activity.

Angiogenesis plays a major role in many physiological and pathological processes. Pathological development of diseased conditions like growth and metastasis of solid tumors and psoriasis is associated with angiogenesis. Assays developed, thus far, for evaluation of angiogenesis activity are qualitative or semiquantitative. In vivo angiogenesis assays are more physiologically relevant than in vitro models and, however, time-consuming, labor-intensive, and expensive. The ex vivo rat aorta tube formation model has been demonstrated to correlate well to the physiological conditions. The present study established a reproducible and quantitative assay for evaluating angiogenesis with rat aorta ring cultures. Rat thoracic aortas were harvested, cross-sectioned into rings of 1-mm thickness using a set of aligned blades, and cultured in a three-dimensional extracellular matrix. Endothelial cells outgrow consistently from the aorta rings cultured in endothelial cell growth medium. Angiogenic activity was quantified by a colorimetric 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2H-tetrazolium/phenazine methosulfate method. The colorimetric assay was reproducible, and its results were compared in parallel with that of the imaging analysis method. IC(50) values of several known antiangiogenics, SU5416, suramin, paclitaxel, and 2-methoxyestradiol, were determined and were comparable to those obtained using the imaging analysis method. We have established a simple, reproducible, and quantitative assay for evaluation of angiogenesis activity with the cultured rat aorta ring, which can be used to screen for angiogenics and angiostatics.

Rotor Configuration Effects on the Performance of a HAWT With Tip-Mounted Mie-Type Vanes

In this paper, the relationships between the power augmentation of a HAWT due to Mie-type tip vane application and other factors influencing the efficiency of a wind turbine such as the blade aspect ratio, number of blades, blade pitch angle and Reynolds number are investigated. Experiments were carried out in a wind tunnel with an open, 3.6 m diameter, test section. Rotor models included two- and three-blade upwind turbines with four sets of blades with different aspect ratios. With the rotor blades tested, a maximum power augmentation of about 14.5% was achieved due to Mie vane application. The relationships between power augmentation due to the Mie vane and the above factors are investigated. It is found that the application of a tip-mounted Mie vane results in a larger increase in maximum power coefficient for rotors with smaller aspect ratios and for lower wind speeds. Surface oil film and surface tuft visualization methods were used to detect the flow patterns at the blade tip. Addition of the Mie vanes causes significant changes in flow behavior near the blade tip, resulting in additional blade lift.

Solidity and Blade Number Effects on a Fixed Pitch, 50 W Horizontal Axis Wind Turbine

Experimental studies were conducted on a modified Rutland 500 horizontal axis wind turbine to evaluate numerical implications of solidity and blade number on the aerodynamic performance. Wind tunnel data were acquired on the turbine with flat-plate, constant-chord blade sets and optimum-designed blade sets to compare with theoretical trends, which had indicated that increased solidity and blade number more than conventional 3-bladed designs, would yield larger power coefficients, CP. The data for the flat plate blades demonstrated power coefficient improvements as the range of solidities was increased from 7% to 27%, but did not indicate performance gains for increased blade numbers. It was also observed that larger pitch angles decreased the optimum tip speed ratio range significantly with a small (5% or less) change in maximum CP. The optimum-design 3-bladed rotors produced an increased experimental CP as solidity increased, with reduced tip speed ratio, at the optimum operating point. As blade number was increased at a constant solidity of 10% from 3 to 12 blades, aerodynamic efficiency and power sharply decreased, contrary to the numerical predictions and the flat plate experimental results. Low Reynolds numbers and wind tunnel blockage effects limit these conclusions and a full scale prototype rotor is being constructed to examine the results of the numerical and experimental studies using a side-by-side comparison with a commercially available wind turbine at the Clarkson University wind-turbine test site.

Optimization of the Length of the Mist-eliminator Blades for Small Size Water Powered Scrubber

ABSTRACT The dust control in anthracite mines in Korea has been important in preventing pneumoconiosis, commonly known as the black lung disease among miners. Portable water-powered scrubber is one of the most effective devices used for dust collection in underground mines or tunnels in Korea. However, there is insufficient information about the design of mist eliminator blades or their performance under different operating conditions of a small size scrubber. In this study, we investigated the possibility of reducing the size of the present water-powered scrubber and the detailed performances of different types of mist-eliminator blades under various working conditions. A full-scale apparatus has been constructed to study the performance of each bend on the mist-eliminator blades. A special gravity-settling chamber and seventeen sets of mist-eliminator blades have been designed and constructed in the laboratory. The results show that the length of the mist-eliminator blades chamber can be reduced by using mist eliminator blades with 42° deflection angle, eight bends, and bend length of 3 cm. Blades having these specifications were the most effective in achieving high dust and coal collection efficiencies within a small distance along the mist eliminator blades. Based on these results, the length of the water powered scrubber can be reduced to 95 cm without significantly decreasing the dust and water collection efficiencies.

A modified Wells turbine for wave energy conversion

The method of wave energy conversion utilises an oscillating water column (OWC). The OWC converts wave energy into low-pressure pneumatic energy in the form of bi-directional airflow. Wells turbine with its zero blade pitch setting has been used to convert this pneumatic power into uni-directional mechanical shaft power. Measurements in OWC based wave energy plants in India and Japan show that the airflow velocity is not equal in both directions. The velocity is more when the airflows out to the atmosphere (exhalation) than in the reverse direction. It may be advantageous to set the rotor blade pitch asymmetrically at a positive pitch so as to achieve a higher mean efficiency in a wave cycle. Towards this objective, performance characteristics of a turbine with different blade setting angles in steady flow were found by experimentation. Quasi-steady analysis was then used to predict the mean efficiency for a certain variation of air velocity with time. This variation with time was taken as pseudo-sinusoidal wherein the positive part of the cycle was taken as a half sine-wave whose amplitude is greater than that of the negative half sine-wave. Such a variation is representative of what happens in reality. For exhalation velocity amplitude to inhalation velocity ratios 0.8 and 0.6, a rotor blade setting angle of 2° was found to be optimum.

Influence of blade-to-blade dissimilarity on alleviation of helicopter blade-vortex interactions

This paper numerically examines possible alleviation of parallel blade-vortex interaction (BVI), experienced by helicopters in low-speed descent, through the introduction of blade-to-blade dissimilarity. A four-bladed rotor with two sets of opposite blades is considered, and the radius of one set is reduced to 80% of the baseline radius. A free-wake analysis is developed for calculating the distorted wake geometry for such a rotor with dissimilar blades. Results indicate that with dissimilarity in blade length, the parallel BVI appear to be weaker due to factors such as increased miss-distance and increased angle (less parallel); so that the blade loading is generally less impulsive in nature. Increased miss-distances for the dissimilar rotor were attributed to the significantly different coning angle of the short and long blades, causing the tip vortices to be released from two different planes. The vortices from the longer blade are released higher, and tend to sail above the shorter blades with a low coning angle, and vice-versa. The acoustic code WOPWOP was used to calculate the BVI sound pressure level in a plane below the rotor disk. For the low-speed descent (severe BVI) flight condition examined, it was found that the peak BVI noise level was reduced by 4dB.

NON-LINEAR FREE VIBRATIONS OF A ROTATING FLEXIBLE ARM

The non-linear, moderately large amplitude flexural free vibrations of an arm clamped with a setting angle to a rigid rotating hub are studied. The shear deformation and rotary inertia effects are assumed to be negligible, but account is taken of axial inertia, non-linear curvature and the inextensibility condition. The Lagrangian approach in conjunction with the assumed modes method, assuming constant hub rotation speed, is used in a consistent manner to obtain the third order non-linear uni-modal temporal problem. Because of the strength of the non-linearities in the temporal problem, which includes elastic and inertial geometric stiffening as well as inertial softening terms, a time transformation method is employed to obtain an approximate solution to the frequency–amplitude relation of arm free oscillation. Results in non-dimensional form are presented graphically, for the effect of hub rotation speed, blade setting angle, and hub radius on the variation of the natural frequency with vibration amplitude.

Perfluorocarbon-mediated aeration applied to recombinant protein production by virus-infected insect cells

Perfluorocarbon (PFC) was used as an oxygen carrier in the cultures of insect cells and virus-infected insect cells. The cell suspensions were placed on a planar layer of PFC, which was re-oxygenated in an outer aeration unit and continuously recirculated, and were agitated by two sets of impeller blades, lower one of which was set in such a way that the ridge of the blade touched the PFC layer. The maximum cell density attained in the PFC-mediated aeration culture was higher than that in surface aeration culture. On viral infection, a recombinant protein yield was significantly high in the PFC-mediated aeration culture as compared with that in the surface aeration culture, though the production was largely decreased by setting apart the lower set of the blade from the PFC–medium interface. These results showed that the PFC-mediated aeration would be a useful technique for insect cell/baculovirus expression system. Overall mass-transfer coefficient K L for oxygen was examined in both the PFC-mediated aeration and surface aeration systems, by using a flask whose dimensions were identical to those of spinner flasks used for the cultures. The K L value in the PFC-mediated system was 2.60×10 −3 cm s −1 , 1.6 times higher than that in the surface aeration system, when impeller blades were positioned at PFC–medium and medium–air interfaces, respectively. However, the K L values in both the PFC-mediated and surface aeration systems were decreased and their differences were brought so close, as the blade was set apart from the interfaces. DO behavior in the cultures was well explained by the model calculation using the determined K L values and oxygen-consumption rates of viable cells. This calculation further suggested that crucial DO, under which recombinant protein productions were unsuccessful, was 0.24–0.5 ppm (3–7%) in the insect cell/baculovirus expression system.

An experimental investigation into the effect of rotor blade sweep on the performance of the variable-pitch Wells turbine

The paper describes an experimental investigation into the effect of rotor blade sweep on the performance of the variable-pitch Wells turbine. The blades tested included two sets of eight symmetrical constant chord NACA 0015 blades (one set had 30° backward sweep, while the other was unswept), two rotor solidities and blade pitch angles of 0° and 20°. The aim of the present experiments was to investigate and compare the aerodynamic performance of the backward swept and unswept blades for different rotor solidities and pitch angles. The measurements covered flowrate, pressure drop, torque and rotor speed. Traversing work with the aid of a directional total static pressure probe yielded more detailed information on the performance of each set of rotor blades. Experimental results have shown that the swept back design of the blades produces a positive value of efficiency and torque over a much wider operating range than the standard unswept NACA 0015 blades, but at the expense of peak efficiency.

A Fiber-Optic Tip-Shroud Deflection Measurement System

A Dutch utility faced the fact that a second stage set of turbine blades of a gas turbine had to be replaced long before the estimated lifetime as a result of tip shroud deflection. This deflection caused the risk of loss of support between the individual tip shroud segments. The goal of this paper is to find the cause of the problem, to see how it increases with time, and to take appropriate action to prevent the problem from occurring again. A fiber-optic tip-shroud deflection monitor has been developed and tested on a gas turbine to study this phenomenon in real time. The optical system is based on astigmatism to derive distance information from the measured optical signals. Characteristic features from the system are the good spatial resolution of about 1 mm, the distance resolution of about 0.1 mm and the distance from the probe tip to the target of about 20 mm. These specifications are difficult to achieve with, for example, capacitive sensors. The probe tip can with stand temperatures of about 500°C. The system can be calibrated in situ, given a stable operation of the gas turbine. This is accomplished by stepping the probe tip over some distance and recording the signals corresponding to a certain point on the tip shroud. The instrument has been used to monitor the tip-shroud deflection in a gas turbine at various loads and over a time span of several months. The results indicate that the deflection can be divided in a part depending on the load and a part that is a permanent deflection. Based on the results, it can be judged whether blades need to be rejected because of a too large deflection.

Important Scaling Parameters for Testing Model-Scale Helicopter Rotors

An investigation into the effects of aerodynamic and aeroelastic scaling parameters on model scale helicopter rotors has been conducted in the NASA Langley Transonic Dynamics Tunnel. The effect of varying Reynolds number, blade Lock number, and structural elasticity on rotor performance has been studied and the performance results are discussed herin for two different rotor blade sets at two rotor advance rations. One set of rotor blades were rigid and the other set of blades were dynamically scaled to be representative of a main rotor design for a utility class helicopter. The investigation was conducted in forward flight at rotor advance ratios of 0.15 and 0.35. Additionally, the rotors were tested over a range of nominal test medium densities from 0.00382 slugs/ft\super{3} to 0.009 slugs/ft\super{3}. This reange of densities permits the acquisition of data for several Reynolds and Lock nuymber combinations.

Two-Phase Flow Measurements and Combustion Tests of Burner with Continuously Variable Concentration of Coal Dust

Problems commonly occur when the coal type and/or the load are changed in utility boilers. To solve these problems, a new pulverized coal burner, namely, a burner with continuously variable concentrations of coal dust by using a set of blades, is developed in this study. Gas−solid two-phase flow downstream of the burner was measured by three-dimensional particle dynamics anemometer (3D PDA). The results show that the particle concentration biased degree of the burner can be continuously adjusted between 1 and 3 by changing the angle between the blades and the primary air flow, over a range of 0−20°. The turbulence characteristics in this range promote ignition and combustion of the pulverized coal. The results of combustion tests in a single burner furnace adopting the new burner verify that the temperature in both the near burner region and the furnace can be raised, which leads to better ignition and combustion characteristics of the pulverized coal than with an ordinary burner.