Blade Rotational Speed Research Articles

Applying multiple tuned mass dampers to control structural loads of bottom-fixed offshore wind turbines with inclusion of soil-structure interaction

Using structural control methods to suppress structural loads of offshore wind turbines is an economical and feasible solution. Note that the dynamic responses of offshore wind turbines are generally analyzed under the parked condition, and the blades are usually modeled with a lumped mass. Actually, the geometrical properties and rotational speed of blades can significantly affect the wind turbine performances. Therefore, these simplifications may result in inaccurate evaluation for the wind turbine dynamic responses, and then further influence the evaluation of the load mitigation effect of a control system. Moreover, the vibration behaviors and structural responses of the wind turbine can be influenced by soil-structure interaction. In this work, the structural responses of a bottom-fixed offshore wind turbine that suffers combined wind and wave excitations are explored. The blade model is explicitly established and soil-structure interaction is also taken into account. The dynamic responses of the wind turbine as well as the vibration mitigation effects of a single tuned mass damper (STMD) and a multiple TMDs (MTMD) system are examined. Furthermore, the sensitivity analysis for the TMD tuning frequency and the robustness of the MTMD system are investigated under the assumption that some TMDs in MTMD do not work properly.

Acoustic distribution study inside centrifugal pump impeller under different blade outlet angles using the Powell vortex sound theory

The acoustic distribution characteristics inside centrifugal pump impeller under different blade outlet angles are explored based on the Powell vortex sound theory. It is shown that the increase in the blade outlet angle narrows the fluctuation ranges of the acoustic source and acoustic pressure perturbation at the impeller outlet far away from the tongue, while extends those near the tongue. The total acoustic source intensity and total acoustic pressure level at the impeller outlet far away from the tongue decrease by 1.23% and 1.17%, respectively, while those near the tongue increase by 0.64% and 0.94% when the angle increases from 15° to 35°, respectively. Additionally, under different blade outlet angles, the total acoustic source intensity and total acoustic pressure level on the streamline far away from the tongue increase rapidly first, then increase slowly from inlet to outlet of the impeller. On the streamline near the tongue, a mutation of total acoustic source intensity and total acoustic pressure level appears near the impeller outlet, and the mutation range moves towards the middle section of the impeller with increasing blade outlet angle and rotational speed. In addition, the A-weighted average acoustic source intensity level and A-weighted average acoustic pressure level increase by 0.4% and 1.22% when the angle increases from 15° to 35°, respectively. The study reveals the rotor–stator interaction intensity evolution characteristics, and provides a reference for the optimization design of centrifugal pumps.

Experimental Study of Flow Inside a Centrifugal Fan Using Magnetic Resonance Velocimetry

Abstract Three-dimensional (3D), three-component time-averaged velocity fields have been measured within a low-speed centrifugal fan with forward curved (FC) blades. The model investigated is representative of fans commonly used in automotive applications. The flow was analyzed at two Reynolds numbers for the same ratio of blade rotational speed to outlet flow velocity. The flow patterns inside the volute were found to have weak sensitivity to Reynolds number. A pair of counter-rotating vortices evolves circumferentially within the volute with positive and negative helicity in the upper and lower regions, respectively. Measurements have been further extended to capture phase-resolved flow features by synchronizing the data acquisition with the blade passing frequency. The mean flow field through each blade passage is presented including the jet-wake structure extending from the blade and the separation zone on the suction side of the blade leading edge.

MODIFIKASI DESAIN TRAKTOR TANGAN “TEMBESI” (STUDI KASUS DI PERKEBUNAN “TEMBESI”)

"Tembesi" hand tractor is a tool in the field of agriculture that is used to loosen the soil that is driven by gasoline fuel motor with a driving motor power of 6.5 Hp. From the results of the previous design testing (Rev_00) found a problem, where the tractor is difficult to move and when the rotating blade is then given a load the blade stops rotating. This study aims to improve the design of the "Tembesi" hand tractor which is focused on reducing the number of blade turns to increase the moment value and repair the part of the tractor wheel.From the design modification results, the blade rotation speed is modified from 1333 rpm to 450 rpm. From the plan moment value 6,925 kg.mm, the force produced by the "Tembesi" hand tractor blade is 387,79 Newton. Wheel modification is carried out using a 12-inch diameter (304.8 mm) rubber tire wheel.

Design of a disk-swing driven piezoelectric energy harvester for slow rotary system application

This paper presents mathematical modelling of an energy harvester that converts slow mechanical rotation into piezoelectric vibration using a small disk and a pair of magnets, for large-scale machinery monitoring applications such as wind turbine blades. The harvester consists of a piezoelectric cantilevered beam, a gravity-induced disk, and magnets attached to both the beam and the disk. The energy method is used to derive the three coupled equations that describe the motion of the disk, the vibration of the beam, and the harvester voltage output. The equations are solved using ODE45 in MATLAB software and verified by the corresponding experimental study. The result shows varied energy harvesting performance by blade rotational speed. At low blade speed, the harvester generates power by regularized magnetic excitation per blade revolution. At high blade speed, however, the disk behavior becomes chaotic to increase excitation force and power generation. The results show that the model can quantify power as a function of blade speed, and the proposed harvester can generate a considerable amount of power for self-sustainable sensing and monitoring of wind turbine blades.

Prediction of mechanical stresses of single rotor blade of low pressure of Nasiriya power plant steam turbine

In this paper, two types of stresses acting on the single rotor blade of low pressure steam turbine for Nasiriya power plant were studied. The first type of stresses was the stresses due to pressure force on the single rotor blade, while the second type of stresses are the centrifugal stresses. The stresses due the pressure force were studied in this paper at three loads (70, 140, 210 MW), while the pressures acting on the first rotor blade of steam turbine were 512, 3311.7, 6496.8 Pa respectively . In addition , the blade was fixed at the root and free at the end, while the rotational speed of blade was 341 rad/sec was applied as rotational load. The results showed that the rotational load has the greatest effect on the blade. Also the stresses due to rotational load are higher than stresses due to steam pressure at the three loads.

Optimisation and analysis of efficiency for contra-rotating propellers for high-altitude airships

ABSTRACTAn improved variational optimization approach is established to optimize and analyse the propulsion efficiency of the high-altitude contra-rotating propellers for high-altitude airships based on the Vortex Lattice Lifting Line Method. The optimum radial circulation distribution, chord and pitch distribution are optimized under the maximum lift-to-drag ratio of aerofoils. To consider the effects of the actual Reynolds number and the Mach number of each aerofoil section, aerodynamics such as lift coefficient, drag coefficient and lift-to-ratio are obtained by interpolating a CFD database, which is established by numerical simulations under different Reynolds number, Mach number and angles-of-attack. The improved method is verified by validation cases on a high-altitude CRP using the three-dimensional steady Reynolds-averaged Navier-Stokes solver and moving reference frames technique. The optimization results of thrust, torque and efficiency for both the individual front/rear propeller and CRP are shown to agree reasonably well with the CFD results. Using the improved approach, the influence of blade numbers, diameter, rotation speeds, axial distance and torque ratio on the optimum efficiency of CRPs is illustrated in detail by conducting parametric studies.

Influence of blade rotation on the lightning stroke characteristic of a wind turbine

AbstractThe blades of a wind turbine rotate during normal operation. To investigate the influence of blade rotation on the lightning‐attracting ability of a wind turbine, a discharge test platform is designed for scaled wind turbines. The 50% impulse voltages and flash probabilities of the scaled wind turbines with gap distances of 1 to 8 m in the static and rotary conditions are determined by using the discharge test and selective discharge test. The discharge test for a single wind turbine with a gap of 1 to 2 m indicates that the breakdown voltages of the gap between the scaled turbine and electrodes increases with an increase in the blade rotation speed. However, the discharge test with a gap distance of 4 to 8 m indicates that the breakdown voltage of the fan decreases with an increase in the blade rotation speed. The test results of the scaled dual wind turbines experiment have the same rules. To explain this phenomenon, the influence of wind speed on the space‐charge distribution and electrical field intensity of corona discharge is simulated in the background of a target thundercloud. The rotation of the fan reduces the space‐charge density near the area of the blade tip, which leads to an increase in the field strength near the blade tip of the wind turbine and a decrease in the field strength away from the blade tip. This influence varies in short and long air gap, resulting in opposite relationships between discharge voltage and distance from the tip of the turbine. The results can provide a reference for the lightning protection of wind turbines.

ВЛИЯНИЕ ЧАСТОТЫ ВРАЩЕНИЯ МЕШАЛКИ И ДЛИНЫ ЕЕ ЛОПАТОК НА КАЧЕСТВО СМЕСИ

The aim of the study is the quality improvement of the feed mixture prepared and substantiation of the design and technological parameters of blade mixer batch- operated. The task is to set the functional dependence between the prepared mixtures quality and the empirical ratio of the intensity of mixing, taking into account the blades length in regard to values of the rotation frequency and the length of the blade of the batch-operated mixer, as well as the definition of rational length of the mixer blades. Improving the quality of mixture requires both the adding of all nec-essary nutrients and feed components into the volume of prepared portion of the mixture as stipulated by the recipe for mixture, and smooth distribution of components throughout the volume of ready feed. Smooth distribution of the mixture components is related to the design and operation of the mixer. Blade mixer batch- operated is one of the effective types of existing mixers, mixing the ingredients of feed with good quality. The article presents the result oriented design scheme of the blade mixer. Positive functions of the mixture quality and the empirical coefficient of mixing intensity included in their composition are assessed taking into account the length of the blades, depending on the rotation speed and frequency of the mixer. The graphic results of experimental studies taking into account the influence of the blade length and the speed of the mixer on the quality of the prepared mixture are given. The increase of blade length and rotation speed improves the quality of the mixture. Recommended blade length is 75...80 mm. With frequency of rotation increase and the length of the blades the total value of the empirical coeffi-cient of the intensity of mixing, depending on the effect of the length of the blades decreases at a slower pace. This is typical of the obtained hyperbolic dependence.

Experimental investigation of tip-leakage flow in an axial flow fan at various flow rates

We investigate the evolution of tip-leakage vortex (TLV) in a low-pressure axial flow fan using digital particle image velocimetry. The blade rotational speed is fixed at 1000 rpm, and the Reynolds number is 547000 based on the blade tip radius and tip velocity. The evolution of TLV in downstream is highly influenced by the incoming flow rate. The TLV breakup occurs for the peak efficiency and stall conditions and sometimes for a higher flow rate, but does not occur for the highest flow rate considered. Thus, the migration speed of the TLV for the peak efficiency condition is faster due to the TLV breakup than those for higher flow rates. The scatter plot of the TLV center location indicates that the TLV wanders around its mean location and the region swept by the wandering motion increases as the TLV migrates downstream. High turbulent kinetic energy exists at the phase-averaged TLV center and its upstream location, respectively, owing to the wandering motion and the interaction between the TLV and main axial flow.

Performance Evaluation of a Maize Stalk Chopping Device Based on Field Tests

HighlightsThe performance of the stalk chopping device is investigated based on field test.The painting method is used to distinguish the different sections of stalks chopped. The broken types of maize stalks are obtained after the stalks being harvested.The percentage of stalk broken is highest of 61.9% at the mid-lower section of maize Xianda 205 stalk. ABSTRACT.Maize stalk is a considerable biomass resource in China. The degree to which stalks are chopped has a substantial impact on subsequent operations in the field. Field tests were conducted to investigate the effects of chopping on different sections of the stalks for different maize varieties, working speeds of the combine harvester and moisture contents of the stalks. Prior to the tests, the stalks were divided into four sections from bottom to top and painted with four colors to identify the different sections of the stalks being chopped. The results showed that the percentage of the qualified length of stalk chopped (PQLSC) gradually decreased and the percentage of the stalk broken (PSB) initially increased and then decreased from the lower to the upper sections of maize stalk under the same rotational speed of blades. When the moisture content of the stalk was held constant, a larger stalk diameter resulted in a higher PQLSC and PSB. The PQLSC was lowest (30.2%) for the lower section of the stalk, and the PSB was highest (48.3%) when the working speed of the harvester was 1.0 m s-1. The PQLSC was highest (37.4%) and the PSB was lowest (40.9%) when the working speed of the harvester was 1.5 m s-1. For the same section of the maize variety Xianda 205 stalks, an increased moisture content of the stalk resulted in a simultaneous increase in the PQLSC and the PSB. The PQLSC was lowest (27.4%) for the lower section of the stalks, and the PSB was highest (51.4%) when the rotational speed of the blades was 807 rpm. The PQLSC was highest (34.1%) for the lower sections of the stalks, and the PSB was lowest (44.8%) when the rotational speed of the blades was 915 rpm. This research provides a reference for the selection of a suitable working speed of the harvester and the rotational speed of the blades for a harvester, which can achieve the smallest particles. Keywords: Chopping, Device, Field test, Maize, Stalk.

Geometry shape selection of NACA airfoils for Mars rotorcraft

Mars rotorcraft, as an aerial auxiliary platform can assist Mars rover to complete exploration missions, is of great significance in the field of planetary exploration. The complex terrain on Mars limits the working range of the Mars rover, whereas a rotorcraft can acquire high detection speed and efficiency, even fixed-point sample using the ability of vertical takeoff and landing. Very little work has been done to analyze the Mars rotorcraft hovering process and there is also limited experimental data exist on the unique Mars flight conditions. A proper understanding of the hovering process is necessary to design a Mars rotorcraft and verify whether it is appropriate or not. In this work, a modified BEMT-CFD model is developed to analyze inflow distribution in the wingspan direction and to predict the aerodynamic performance of the rotor system. Based on the developed model, a suitable airfoil is selected and the operational parameters are investigated to design a suitable rotor configuration for the Mars rotorcraft. Hover experiments demonstrate that the modified model can effectively predict the rotor hover performance. Using the suitable blade pitch angle and rotational speed, the rotor can generate enough thrust to support a 500 g rotorcraft to fly in the simulated Mars environment.

Dynamic Study of a Rooftop Vertical Axis Wind Turbine Tower Based on an Automated Vibration Data Processing Algorithm

When constructed on tall building rooftops, the vertical axis wind turbine (VAWT) has the potential of power generation in highly urbanized areas. In this paper, the ambient dynamic responses of a rooftop VAWT were investigated. The dynamic analysis was based on ambient measurements of the structural vibration of the VAWT (including the supporting structure), which resides on the top of a 24-story building. To help process the ambient vibration data, an automated algorithm based on stochastic subspace identification (SSI) with a fast clustering procedure was developed. The algorithm was applied to the vibration data for mode identification, and the results indicate interesting modal responses that may be affected by the building vibration, which have significant implications for the condition monitoring strategy for the VAWT. The environmental effects on the ambient vibration data were also investigated. It was found that the blade rotation speed contributes the most to the vibration responses.

Reliability based multidisciplinary design optimization of cooling turbine blade considering uncertainty data statistics

Considering the coupling among aerodynamic, heat transfer and strength, a reliability based multidisciplinary design optimization method for cooling turbine blade is introduced. Multidisciplinary analysis of cooling turbine blade is carried out by sequential conjugated heat transfer analysis and strength analysis with temperature and pressure interpolation. Uncertainty data including the blade wall, rib thickness, elasticity Modulus and rotation speed is collected. Data statistics display the probability models of uncertainty data follow three-parameter Weibull distribution. The thickness of blade wall, thickness and height of ribs are chosen as design variables. Kriging surrogate model is introduced to reduce time-consuming multidisciplinary reliability analysis in RBMDO loop. The reliability based multidisciplinary design optimization of a cooling turbine blade is carried out. Optimization results shows that the RBMDO method proposed in this work improves the performance of cooling turbine blade availably.

Agitated thin-film drying of foods

Agitated thin-film drying (ATFD) has been proposed for efficient and mild drying of viscous liquid foods, pastes or pureed foods. We report a study on the influence of product and process parameters on ATFD. During ATFD of spinach leaf slurries, the wall temperature mainly affected the specific evaporation rate, while the absolute evaporation rate was proportional to the feed rate. The fact that blade rotation speed had limited effect on the drying rate suggested that the process is limited by heat transfer through the wall. ATFD is especially suited for slurries that show relatively limited sticky behavior during drying and liquid–solid phase transition with corresponding brittle viscoelastic behavior. This was demonstrated by drying juices from tomato and bell pepper, giving poor results, and by drying solutions from whey protein isolate (WPI) and sucrose, which could be successfully dried.

DESIGN of AUTOMATIC ORGANIC WASTE CRUSHER USING ARDUINO MICROCONTROLLER

Organic waste is the residual daily activities of humans or natural processes in the form of solid or semi-solid in the form of organic or inorganic substances that are biodegradable or unraveled which are considered useless and disposed of in the environment. This organic waste can be used as fertilizer for plants if processed properly, therefore this waste can be used as fertilizer processing by destroying, so this study aims to create a tool that can destroy waste so that it is easy to process using an Arduino microcontroller, the design is done ranging from hardware to software. The way the device works is to detect the material to be destroyed, then the system will be active, the tool is designed a choice of time for the material to be destroyed so that the appliance will automatically die when the time expires and the choice of blade rotation speed from maximum, medium to minimum. From the experiments carried out the tool was able to destroy the material until smooth. DOI : https://doi.org/10.26905/jeemecs.v1i2.2377

State-of-the-Art Finite Element Modeling of Rotorcraft Main Rotor Blade for Bird Strike Damage Analysis

This paper demonstrates the state-of-the-art composite modeling methodology to investigate the bird strike phenomenon using available numerical bird models through experimental tests and simulation tools. The present work is based on the application of nonlinear explicit finite element analysis to simulate the response of rotorcraft main rotor blade root end under high velocity impact load. The damage behavior of blade made of composites under soft body impact depends upon bird size, blade size, blade span-wise location of impact and bird orientation with respect to hitting location, blade rotational speed and rotorcraft cruise speed. Bird model is considered as hydrodynamic with length-to-diameter ratio of 2. A bird strike event is characterized by loads of high intensity and short duration. A transient explicit nonlinear finite element-based impact analysis using Autodyn has been carried out to predict bird strike resistance to withstand 1.0 kg bird at critical flight condition. Numerical analysis indicates that blades do not tear which agrees well with the physical test conducted.

Helicopter Main Rotor Blade Root End under High Velocity Bird Impact

A numerical simulation methodology has been successfully developed to model the bird strike on the innovative helicopter main rotor blade root end under high velocity bird impact. This paper demonstrates the state-of-the-art composite modelling methodology of main rotor blade and numerical bird models through experimental tests and simulation tools. The present work is based on the application of non-linear explicit finite element analysis to simulate the response of main rotor blade root end. The damage behavior under soft body impact depends upon bird size, blade size, blade span wise location of impact and bird orientation with respect to hitting location, blade rotational speed and rotorcraft cruise speed. Bird model is considered as hydrodynamic with length to diameter ratio of 2. A bird strike event is characterized by loads of high intensity and short duration. A transient explicit non-linear finite element based impact analysis using Autodyn has been carried out to predict bird strike resistance to withstand 1.0 kg bird at critical flight condition. The numerical simulation results are compared to experimental bird strike test data, leading to conclusions about the success of both the design concept and the simulation methodology. The comparison shows a very good agreement between experimental and simulated damage evolution during impact.

Using forward end-sweep to reduce transonic cantilevered stator losses to improve compressor performance

ABSTRACTThe complicated flows in a transonic cantilevered stator would cause serious aerodynamic losses and reducing these losses would contribute much to improving the overall aerodynamic performance of a compressor. The paper conducts an overview study of the potential aerodynamic losses in a transonic cantilevered stator and presents a systematic numerical study for the effects of forward end sweep on reducing aerodynamic losses. A 2-D stator blade is used to throw light upon the physical mechanism of the forward end sweep on reducing the losses. At the casing region, forward end sweep has led to a redistribution of the blade load along the chordwise direction, higher in the front part and lower in the rear part. This result leads to a lower pressure gradient from the 30% chord location to the trailing edge and can be beneficial for the reduction of the corner separation. At the hub region, on one aspect, forward end sweep reduces both the peak Mach number and the size of the high-Ma region of the blade suction surface, thus decreasing the shock loss near the hub. On the other aspect, it also reduces the peak load and the strength of the leakage vortex, therefore alleviating the flow blockages. Simultaneously, the forward end sweep is applied to a commercial and high-performance multistage compressor to further validate its feasibility. When the technique is applied to the transonic first four stator rows, an improvement of adiabatic efficiency is achieved by ∼ 0.85% and the compressor stable operating range is slightly increased. The results suggest that the forward end-swept transonic cantilevered stators have a significant potential for reducing the stator losses. They would provide guidelines to advance the cantilevered stator design and further improve the compressor aerodynamic performance.Abbreviations: h, stagnation enthalpy; , stagnation pressure; p, static pressure; U, blade rotational speed at tip; V, velocity; , non-dimensional wall distance; , total pressure loss coefficient; , flow coefficient (Vx/U); , stage load coefficient (Δh/U2); , adiabatic efficiency; , total pressure ratio; in, inlet; out, outlet; LE/TE, leading/trailing edge; PS/SS, pressure/suction surface

The lifting force relationship of a BLDC motor rotor system to the blade rotation speed

In developing the knowledge and information about the Quadcopter aircraft, the parameters related to aircraft lift capability factors; fly long; flying high; type of motor; the type of propeller; including the sensors and control systems used. To find out of the BLDC motor voltage source to the rotor angle velocity (ω) relationship; rotor speed to wind velocity through rotor (v); rotor speed to rotor lift (Ft); wind speed to rotor lift; push the following rotor (Ct).Test and measurement results data show that; the lift force generated with rotational speed relationship is not proportional Nonlinearity occurs when the rotor is released from the self and starts pulling the strain gauge when the rotation speed reaches around 65 rps. Once the rotation speed of the rotor is able to reach up to 1.5 Newton lift then the thrust rising trend increasing sharply to the increasing the speed of rotation of the rotor. A special rotor that has BLDC motor specifications such as; 1200 KV, 12 Volt and 30 Ampere; blade with a radius of r 0.12 m; at a temperature of about 27 oC; in the condition there are no other wind currents then obtained thrust (Ct) of 1.732.