Rotational Speed Of Rotor Research Articles

Yaw Behavior of Horizontal-Axis Small Wind Turbines in an Urban Area

This paper reports the experimental study on passive yaw behavior of a horizontal axis small wind turbines. The yaw angle velocity in a small wind turbine is one of the significant design values and IEC61400-2 Ed.2 prescribes its maximum value should be less than 3 rad/s. However, in practice, in the case of small wind turbines with diameters under 2 m, the yaw angular velocity may exceed the limit of 3 rad/s. The authors conducted a theoretical evaluation as well as a wind tunnel test to examine the possible maximum yaw velocity. The model wind turbine has a diameter of 1 m, blade number of 5, solidity of 0.26 and 2 types of tail fins (large and small). For each tail fin size, the yaw behavior was studied for a range of rotational speeds and wind speeds. The results show that the yaw angular velocity becomes larger with increasing wind velocity and tail fin area. The larger the rotor rotational speed, the smaller the yaw angular velocity. Furthermore, a maximum yaw angular velocity of 3.84 rad/s was observed at a wind speed of 10 m/s, which exceeds the conventional design value of 3 rad/s.

Study on leakage flow characteristics of radial inflow turbines at rotor tip clearance

Tip clearance leakage flow in a radial inflow turbine rotor for microturbines under the stage environment is investigated using a three-dimensional viscous flow simulation. The results indicate that the scraping flow caused by relative motion between casing and rotor tip, and the pressure difference between pressure side and suction side at rotor tip, play important roles in tip clearance leakage flow. The more the rotor tip speed increases and tip clearance height decreases, the more the scraping effect acts. Though the leakage velocity of tip clearance at midsection and exducer regions changes less when the rotor rotational speed is changing, the distance between passage vortex and rotor suction side varies in evidence. Main leakage flow rate of tip clearance takes place at region of exducer tip and some seal configurations will be quite effective for cutting leakage flow if these configurations are arranged over midsection and exducer of the radial inflow rotor.

Contoured shaft and rotor dynamics

Abstract The dynamics of shaft–rotor systems, where the shaft profiles are contoured, are considered. Shafts with diameters which are functions of the shaft length are analysed. Procedures enabling the determination of the deflection, slope, bending moment and shear force at the extremities of the shaft are employed. Resonance, critical speed or whirling frequency conditions are computed using simple harmonic response methods. The response of the system for particular shaft–rotor dimensions and rotational speeds is determined, establishing the dynamic characteristics in the vicinity of the whirling speed. A cantilevered shaft–rotor system with an exponential – sinusoidal profile is investigated for purposes of illustration. The flexibility of the approach and the general applicability of the technique proposed is emphasised.

10.1007/s11498-008-2015-x

The dilute solutions of poly(vinylcaprolactam) and its fullerene C60 complex have been studied by high-velocity sedimentation, translational diffusion, viscometry, and static and dynamic light scattering. The experiments have been performed for the sample with M ≈ 2.7 × 105. In the absence of external action, supramolecular structures (clusters) whose size and molar mass are much higher than the corresponding characteristics of the polymer matrix appear in solutions of the poly(vinylcaprolactam)-C60 complex. When subject to a strong centrifugal force or an intense shear flow, the supramolecular structures are destroyed and the molecular characteristics of the complex correspond to those of poly(vinylcaprolactam) macromolecules. The dynamics of destruction of the cluster organization in aqueous solutions of fullerene-polymer complexes has been investigated by high-velocity sedimentation. As the angular speed of ultracentrifuge rotor rotation is decreased from 55000 to 10000 rpm, the sedimentation constant S 0 of the poly(vinylcaprolactam)-C60 complex increases by a factor of ∼4. This behavior reflects changes in the size and molar mass of clusters with the centrifugal force acting upon complex macromolecules.

Technical Note: Geometrical Analysis of the Effects of Rotary Tiller Blade Path on the Distribution of Soil Slice Size

The blades of a rotary tiller trace a trochoidal path in the soil during tillage. This path is affected by both rotational and forward speeds. The successive trochoidal paths of two blades cut the soil into slices. The size and shape of soil slices depends on the number of blades on one side of a flange, rotor radius, tractor forward speed, rotor rotational speed and blade geometry. Therefore, a better understanding of the factors affecting soil slice size will help us to appropriately operate rotary tillers. In the present study, rotary tiller blade paths were used to simulate distribution of the soil slice size. A program was written in the Lisp language for AutoCAD to draw blade paths based on the number of blades on one side of a flange, the rotor radius, tractor forward speed, and rotor rotational speed. Slice area on the drawn paths was calculated using the AREA command of AutoCAD. Data show that soil slice size increased as rotor radius and tractor forward speed increased and the number of blades on one side of a flange decreased. As the rotor rotational speed increased to 190 min-1, the volume of soil slice increased to a maximum. Then, as the speed increased further, the volume decreased. The number of cuts of a soil slice increased as the number of blades on one side of a flange, the rotor radius, and the rotor rotational speed increased. As the number of cuts of a slice increased, the size of each part decreased and soil fragmentation increased.

Characteristics of wind power on Savonius rotor using a guide-box tunnel

This study investigates to improve and adjust the output power of Savonius rotor under various wind power and suggests the method of prevention the rotor from strong wind disaster. In this study, as the appropriate device to achieve the purpose of it, a guide-box tunnel is employed. The guide-box tunnel is like a rectangular box as wind passage in which a test rotor is included. The area ratio between the inlet and exit of it is variable to adjust the inlet mass flow rate or input power. At first, the experiment was conducted to find the adequate configuration which would provide the best relative performance. The present experiment, however, does not include the test to retain the guide-box tunnel from the strong wind. The experiments include the static torque test of the fixed rotor at any phase angle and the dynamic torque test at rotation of them. Consequently, it was found that the maximum rotor rotational speed was achieved in the range of the guide-box area ratio between 0.3 and 0.7 and the value of the output power coefficient of the rotor with guide-box tunnel of the area ratio 0.43 increases about 1.5 times with three blades and 1.23 times with two blades greater than that without guide-box tunnel, respectively. It seemed that the performance of Savonius rotor within the guide-box tunnel is comparable enough with other methods for augmentation and control of the output.

Test unit for gas dynamic tests of low consumption stages of centrifugal compressors

An experimental test unit is created for studying low-consumption stages of centrifugal compressors with a rotor magnetic suspension system (MSS) and a torsional moment transducer. In addition, this unit makes it possible to perform MSS studies in the area of functional construction, analysis and synthesis of dynamic characteristics of the rotor-MSS system. The rotation speed of the model rotor is 1000–25000 rpm. In order to reduce the loss of power in bearings, a rotor magnetic suspension device is used, developed and manufactured in the V. B. Shnepp Turbocompressor Research Institute. The torsional moment transducer, installed in a coupling between the set-up gear and the bearing support, provides the possibility of measuring power in the impeller shaft with compression of the working gas.

Experimental heat transfer and flow analysis of a vented brake rotor

Brake rotors generate an opposing torque to a shaft, converting kinetic energy to heat thus necessitating heat transfer considerations. To better understand convection through the fins of a brake rotor, experimental and analytical methods were employed. The experimental approach involved two aspects, assessment of both heat transfer and fluid motion. A transient experiment was conducted to quantify the internal (fin) convection and external (rotor surface) convection terms for three nominal speeds. For the given experiment, conduction and radiation were determined to be negligible. Rotor rotational speeds of 342, 684, and 1025 [rpm] yielded fin convection heat transfer coefficients of 27.0, 52.7, 78.3 [W m −2 K −1], respectively, indicating a linear relationship. At the slowest speed, the internal convection represented 45.5% of the total heat transfer, increasing to 55.4% at 1025 [rpm]. Analytical solutions were evaluated where possible for the convective terms and found to be comparable to the experimental results. The flow aspect of the experiment involved the determination of the velocity field through the internal passages formed by the radial fins. Utilizing PIV (particle image velocimetry), the phase-averaged velocity field was determined. A number of detrimental flow patterns were observed, notably entrance effects and the presence of recirculation on the suction side of the fins.

Performance of VOC Abatement by Thermal Swing Honeycomb Rotor Adsorbers

Fine powder of hydrophobic high silica zeolite was solidified with silica sol in the void of a 0.2 mm thick ceramic fiber sheet fabricated into a honeycomb structure, typically with 3.2 mm pitch × 1.7 mm height. The honeycomb rotor of adsorbent was applied to the VOC abatement system operating with thermal swing adsorption. Dependence of the removal efficiency of VOC on various variables was investigated for a test honeycomb rotor of 300 mm in diameter. The following operating guide was recommended to reach high performance where more than 95% of VOC in the feed gas is removed: superficial velocity of feed air = 2−4 m/s, flow rate ratio of process to regeneration zone = 5−15, relative humidity < 80%, and regeneration air temperature = 180 °C with rotation speed optimized. The optimal rotation speed of the honeycomb rotor was investigated closely, and the result was interpreted in terms of the heat capacity ratio between the honeycomb rotor and the regeneration air stream.

Numerical and experimental study of a rotor–bearing–seal system

Abstract The non-linear dynamic behaviors of a rotor–bearing–seal coupled system are investigated. The influence of parameters, such as the rotation speed, seal clearance and eccentricity of rotor are analyzed by state trajectory, Poincare maps, frequency spectra and bifurcation diagrams. Various non-linear phenomena compressing periodic and quasi-periodic motion in the rotor–bearing–seal system are investigated. The comparison between the analytical results of the numerical and the experimental findings shows that the predictive results agree with the experimental results. It is indicated that this study may contribute to a further understanding of the non-linear dynamics of such a rotor–bearing–seal coupled system.

STUDY THE EFFECT OF QUADRATIC BLADE SHAPE ON THE VERTICAL AUTOROTATION PERFORMANCE OF A SMALL SCALE MODEL HELICOPTER

This paper presents the results of the numerical and experimental investigation of reducing the steady rate of descent of a typical small scale model helicopter. Power-off after hovering manoeuvre was picked for a case of study because of their critical induced velocity state. Contribution in every blade element in the effect of angle of attack, thrust and torque has been taken into consideration by blade element momentum theory for better results. In this analysis, test data of two types of blades with different driving region areas were obtained. The results of this study indicated that the expanding of the driving region area did reduce the steady rate of descent in vertical autorotation slightly but give lower rotor rotational speed compared to original shape blade. The study also had shown that zero collective pitch angle correction in the autorotation entry gives the best autorotation performance.

Suggestions for improving wind turbines power curves

The question is usually not whether a wind turbine can be designed to optimise the power production at the site, but rather whether an existing wind turbines with a certain rotor can be modified in order to improve the power production. In this paper the various methods for improving the wind turbines power output were investigated experimentally and theoretically. The effect of changing the rotational rotor speed on the power performance of Nordtank 300 kW stall-regulated, horizontal axis wind turbine was investigated experimentally. This was performed by changing the setting program for operating the wind turbine. The variation in the aerodynamic performance of the wind turbine rotor due to changing the pitch angle was investigated experimentally in Hurghada wind farm. The manufacture setting tip angle for Nordtank 300 kW wind turbine is (–1.8°). In this study, the angle was changed to two values (–2.8°) and (–0.8°). Also, to improve the blade performance of a wind turbine operating in low wind speed ranges; the vortex generators may be used. These vortex generators were placed over low-pressure surface of blade or tip blade part. In this study, two types of vortex generators, rectangle and triangle shapes were investigated.

Performance test and flow measurement of contra-rotating axial flow pump

An application of contra-rotating rotors has been proposed against a demand for developing higher specific speed axial flow pump. In the present paper, the advantage and disadvantage of using contra-rotating rotors are described in comparison with conventional type of rotor-stator, based on theoretical and experimental investigations. The advantages are as follows: (1) The pump is inherently designed as smaller sized and at lower rotational speed. (2) A stable head-characteristic curve for flow rate with negative slope appears. (3) As the rear rotor rotational speed is varied as independent control of front rotor, the wider range of high performance operation is obtained by rear rotor speed control in addition to front rotor speed control. The disadvantages are as follows: (1) The structure of double shaft system becomes complex. (2) The pump performance is inferior at over flow rate as the rear rotor loading is weakened. (3) The blade rows interaction from rear rotor to front rotor more strongly appears. Then the rear rotor design is a key to achieve higher pump performance. Some methods to overcome these disadvantages will be discussed in more details toward wider usage of contra-rotating axial flow pump in various industrial fields.

OS2-10 リボン型風車の性能評価(OS2 自然エネルギー,循環型社会における動力エネルギー技術)

The performance of the ribbon type wind turbine was investigated in wind tunnel experimentally. The test was performed with changing the rotational speed of rotor for several wind velocity. Moreover, the velocity field around rotor was measured by an laser Doppler velocity meter (LDV). The areas for velocity measurement are both circumference of maximum diameter of blades and around wind turbine. The flow was visualized by using the measured velocity. As a result of velocity measurement around maximum diameter, it turned out that vortex was observed in the point of maximum diameter of blades. Furthermore, the stream tube around ribbon type rotor is shown and the velocity distribution in the rotor wake is shown.

Wieloparametrowa analiza zelowania poli(chlorku winylu)

The results of plastometric tests of unplastified compound of suspension PVC were presented. It was found (Table 1) that characteristic values at plastograms, related to the compound gelation, depended simultaneously on temperature of the chamber wall (T, range investigated 160-200 °C) and on rotational speed of rotors (n, range investigated 5-40 min - 1 ). Dependence found was described with use of multifactorial models elaborated with a statistical method of linear or square regression. From the analysis of linear regression it results the greatest agreement of the model proposed with experimental data was found for the temperature of a compound at torque equilibrium state. What concerns square regression the better agreement between the model and experimental data has been found. The results of the tests are described the best way by the model describing dependence of work W B - X to reach the maximum torque as well as real temperature T E at torque equilibrium state on chamber temperature and rotational speed of rotors.

Side-Delivery Spreading of Manure

The optimum use of natural resources is even more vital in areas with limited possibilities for agricultural production. A better use of those resources yields improved production; however, improved production requires fertilization. Optimum coverage with stable manure on sloping terrain can be achieved by spreading in the direction perpendicular to the direction of travel of the spreader. A mathematical model and simulations were devised in order to serve as a basis for recognizing the key parameters of spreading. The rotor's rotational speed, the loading area for manure pieces onto the rotor, and the outlet area emerged as the most important parameters for this side-delivery spreader. A special spreading device was designed on the basis of the acquired data. It features greatly improved spreading properties and quality of spreading, together with considerably safer handling. The prototype was tested according to European Standard EN 13080.

油・水・ガス‐三相流における粘性効果と多相流量計への適用

Each flow rate of liquid-gas two-phase flows can be iteratively evaluated by measuring the pressure drop across an inline homogenizer for mixing the fluids and the rotation speed of a turbine rotor behind the homogenizer. JOGMEC has extended this idea to measure the oil, gas, and “water” flow rates simultaneously, and proposed a Multiphase Flow Meter (MPFM), which is composed of the homogenizer and a turbine meter with an inner assembly of twin rotors connected by a spring. However, the resultant volumetric flow ratio of water phase has a defect in accuracy. To improve the accuracy, the mechanisms of single-phase flow, gas-liquid two-phase flow, liquid-liquid two-phase flow and liquid-liquid-gas three-phase flow are investigated theoretically and experimentally. The results suggest that the proposed constructive formula may improve the accuracy of the measurements.

Gelation of suspension PVC with small amount of plasticizer compounds

Summary — The course of gelation of suspension PVC-S (K values 58, 61 or 67) plastified with small amounts (0.5—4 phr) of dioctyl phthalate (DOP) was investigated in Brabender plastometer chamber. Rotational speed of rotors was 28 min -1 . On the basis of torque changes and the measurements of real temperature of gelating compound versus process time the curves of torque change versus this temperature were prepared for various plasticizer contents. It was found the higher DOP content the lower temperature corresponding to maximum torque, characterizing the gelation process. The dependence of real temperature of a compound in equilibrium state (TE) on DOP content shows that gelation occurs when chamber temperature reaches 170 o C and plasticizer content is equal DOPmin = 2.5 phr. Effects of these parameters on the torque measured at equilibrium state are similar. Addition of 2.5 phr of DOP caused rapid increase in gelation degree (G) during processing of all the types of PVC tested, at temp. 175 o C.

Air/Water Two-Phase Flow Performance of Contra-Rotating Axial Flow Pump and Rotational Speed Control of Rear Rotor

An application of contra-rotating rotors, consisting of front and rear rotors rotating in the opposite direction each other, has been proposed against a demand for developing higher specific speed axial flow pump with more compact structure, higher efficiency and better cavitation performance. Air/water two-phase flow performance of contra-rotating pump has to be, also, investigated as axial flow pumps are used for standby operations of air-lock and air/water mixing discharge to prevent floods. In the present paper, experimental results on air/water two-phase flow performance of test pump of contra-rotating rotors (RR1 Type) are shown and compared with those of conventional axial flow pump, consisting of a front rotor and a rear stator. Effects of changes of rear rotor rotational speed, which is an advantage of contra-rotating axial flow pump, on two-phase flow performance of RR1 type are discussed. It is shown that air/water two-phase flow performance of contra-rotating axial flow pump is capable to be improved by this control procedure for rear rotor rotational speed.

An ultrasonic motor driven by the phase-velocity difference between two traveling waves

This paper presents a new ultrasonic motor in which the rotor rotation speed is locked by the phase-velocity difference between the two traveling waves propagating on the stator and the rotor. First, the unique construction to excite two traveling waves both in the stator and the rotor is described. Then, the operation principle of the present motor is revealed by our careful experiments. Dynamics of the two traveling waves are measured by an in-plane laser Doppler vibrometer under various conditions, as well as the motor performances. Our experiments show that the rotation speed of the motor is equal to the phase-velocity difference between the two traveling waves on the contact surfaces of rotor and stator. It is confirmed that the rotor rotates so as to cancel the phase-velocity difference between the traveling vibrations along the circumferences of the rotor and stator. If the load does not exceed the maximum torque that is determined by the vibration amplitude, the rotation speed is subject only to the phase-velocity difference.