Set Of Blades Research Articles

Dynamic coupling vibration of rotating shaft–disc–blade system — Modeling, mechanism analysis and numerical study

This study aims at revealing the coupling vibration mechanism of RSDB system. First, a comprehensive coupling dynamic model of RSDB system including the shaft bending, shaft torsion, blade bending, and blade radial deformation is formulated based on continuum beam theory and Lagrange equation. The validity of the proposed dynamic model is verified through a comparison with FEM and experimental results. Second, the general coupling mechanism of RSDB system is theoretically interpreted based on the proposed analytical coupling vibration model, which indicates that the blade vibration and shaft vibration, especially the shaft torsion vibration and blade bending vibration, may affects each other significantly. At last, the steady-state coupling vibration responses and the effects of structure parameters on the coupling vibration of RSDB system are comparatively investigated through numerical investigations. The comparative results suggest that the blade setting angle, blade–blade coupling stiffness, and the disc location on shaft will greatly affect the coupling vibrations. It worth more attention that the general coupling vibration mechanism obtained by analytical analysis and the results obtained by numerical study can be cross-verified by each other.

Optimizing Power Reclamation of Micro Hydro Turbines in WWTPs Aeration Basins

Abstract This study investigates the optimum operating conditions and design configurations that can optimize the power reclaimed by small hydro turbines derived by the rising water-bubble current. The rising current is generated by the compressed air introduced by the diffusers at the bottom of aeration basins of Wastewater Treatment Plants (WWTPs). While optimizing the power production, the standard oxygen transfer efficiency (SOTE) is monitored since it is a significant parameter that cannot be sacrificed in the operation of WWTPs. Using one set of turbine blades, it was found out that the highest velocity is obtained in the upper half of the water column (70% - 80%). In contrast, the lowest velocities were obtained just above the air diffuser and at the water surface. Testing started with using a single turbine (ST) to determine the location of the optimum power reclaimed at each tested airflow (1.18, 1.42, 1.65, and 1.89 L/s). Then using double turbine (DT) and triple turbine (TT) to compare their performance to the ST’s maximum power increased power reclamation. The maximum percentage of increase in power reclamation for DT is 19.59%, while it is 20.24% in the case of TT. At a commonly used airflow in WWTPs (1.42 L/s), the optimum configurations of DTs and TTs were selected to investigate the effect of having the proposed setup on the SOTE. For membrane diffusers, DTs and TTs limited the dispersion of the air bubbles in the tank, therefore, reducing the SOTE (8.3% for DT and 3.7% for the TT). The ceramic and sharp-nub diffusers were also tested versus rubber membrane ones to determine the effect of using the ceramic and sharp-nub diffusers on the power reclamation and SOTE. Ceramic diffusers neither achieve higher power reclamation than the membrane nor increases the SOTE. In contrast, sharp-nub diffusers increase the SOTE for all configurations compared to membranes, but this came into account of power reclamation, where sharp-nub diffusers cause a DT and a TT to produce less power than ST does.

The Parametric Modeling and Two-Objective Optimal Design of a Downwind Blade

To cope with the future challenges to the blade that will be introduced by the development of extreme-scale wind turbines, this study focuses on the optimization design of the aerodynamic shape of a downwind bladeviathe inverse design method. Moreover, the genetic algorithm is used to optimize the chord, twist angle, and pre-bending parameters of the blade to maximize the energy production of the rotor and minimize the flapping bending moment of the blade root. By taking a 5-MW wind turbine as the optimization object, the two-objective optimization design of the downwind blade is carried out, and Pareto optimal solutions in line with the expectations are obtained. After analyzing four representatives of the Pareto optimal solutions, while a more ideal solution is found to sacrifice 9.41% of the energy production of the rotor, the flapping bending moment of the blade root is reduced by 42.92%, thereby achieving the lightweight optimization design of an extreme-scale wind turbine blade. Furthermore, based on the selected four sets of blades, the influence mechanisms of the chord, twist angle, and pre-bending on the optimization goal are analyzed, and it is found that the pre-bending parameter has the greatest influence on the two optimization goals.

Threshold damage-based fatigue life prediction of turbine blades under combined high and low cycle fatigue

Life prediction based on the damage mechanics of aero-engine turbine blades is crucial for performing their strength design and ensuring the operational reliability under combined high and low cycle fatigue (CCF) loadings. In view of this, a simple and efficient life prediction method is developed to consider the interaction of high cycle fatigue (HCF) and low cycle fatigue (LCF) without any additional material constants, and as a basis of that a new nonlinear damage accumulation model is proposed by introducing threshold damage of the component related to material type and current HCF damage. In order to validate the presented methodology, model predictions were compared with the experimental data sets of turbine blades and its alloy materials. The predicted results indicate that the simple life prediction model is capable of estimating the fatigue life quickly with an acceptable accuracy in contrast to other four existing ones. Moreover, the threshold damage-based method provides the higher prediction accuracy than others due to improved HCF damage determined by the damage threshold.

Requirements for a digital twin of the bulldozer work tool

The paper presents a brief description of the bulldozer as a widely used machine for earthworks. The method for determining resistive forces to digging is analyzed based on the theory of layer-by-layer excavation works. The relationship for determining the area of the longitudinal section of the dragging prism is presented, and on its basis the productivity is further calculated. The characteristics of forces resistive to digging are constructed with the accepted parameters of the blade and soil for different angles of blade setting. The criterion for determining the efficiency of earthmoving operations is presented, which was developed on the basis of unit costs. It is stated that excavation works are performed effectively at a certain angle of blade setting. Requirements for a digital twin of the bulldozer work tool, which is designed to improve the efficiency of its operation, have been developed.

Torque and Power Testing of the Pelton Turbine

Energy sources that can be renewed in Indonesia according to Asean energy sources, one of which is microhydro that uses water as a source of energy from a turbine. The potential energy of water is converted into kinetic energy in the nozzles. The water coming out of the nozzle that has a high speed hits the turbine blade. After hitting the blade direction the flow velocity changes so that the momentum changes (impulses) so that the turbine wheel will rotate. Pelton Turbines are impulse turbines which consist of a set of road blades that are rotated by a jet of water sprayed from one or more devices called nozzles. Pelton Turbine is one of the most efficient and suitable types of water turbines used for high head and small flow discharge. Pelton turbines have several advantages including turbine efficiency which is relatively stable at various changes in flow discharge. The purpose of this writing is to find out and provide insight into the torque and power of the Pelton turbine and the effect on the valve openings that are varied.

Quieter and Greener rotorcraft: concurrent aerodynamic and acoustic optimization

Within the DLR project VicToria an aerodynamic and aero-acoustic optimization of helicopter rotor blades is performed. During the optimization, three independent flight conditions are considered: hover, cruise and descent flight. The first two flight conditions drive the power requirements of the helicopter rotor, while the descent flight is the loudest flight condition for current helicopter generations. To drive down the required power and the emitted noise, a multi-objective design approach coupled with surrogate models is utilized to find a Pareto optimal set of rotors. This approach allows to identify the trade-offs to be made when laying emphasis on either goal function. The underlying CFD simulations utilize fourth-order accurate spatial schemes to capture the vortex dominated flow of helicopter rotor blades. The paper presents the validation of the setups, the optimization results and the off-design analysis of a chosen set of blades from the Pareto front. The conclusion is that the utilization of the Pareto front approach is necessary to find good rotor designs, while the utilization of high-order methods allows for efficient CFD setups.

Surrogate based optimization of a Bi-Directional impulse turbine for OWC-WEC: Effect of guide vane lean and stagger angle for pseudo-sinusoidal wave conditions

An oscillating water column (OWC) wave energy device can use a bidirectional flow impulse turbine for energy extraction. The airflow velocity profiles during inhalation and exhalation of the OWC are asymmetric, and the flowrate at exhalation is higher. Hence, this article presents an optimized turbine to work for asymmetrical airflow conditions. The rotor blade setting angle (γ) was made asymmetric with a non-zero setting angle, and the guide vane shape was optimized. The unsteady Reynolds-averaged Navier-Stokes equations (URANS) were solved to get the objective function values for the Latin hypercube sampling (LHS) generated design space. A pseudo-sinusoidal velocity profile replicating the flow inside the OWC device was used for the transient simulations. A weighted average surrogate model generated the initial population for a hybrid genetic algorithm to produce optimum designs. The effect of turbine induced damping and starting characteristics were analyzed under irregular flow conditions obtained from the Pierson–Moskowitz wave spectrum. The optimized turbine resulted in better starting and running characteristics. Also, the mean efficiency of the optimized turbine was increased relatively by 9.5%.

Slit-Type Cavities for Cyclotron Resonance Masers Operating at TM Modes

We present a theory of cavities with longitudinal slits which allow the external Q-factor of modes to be evaluated. We also propose a cavity design with a regular section made of a set of metallic blades separated by slits. 3-D-PIC simulation of a V-band gyrotron operating at the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12, 1</sub> mode with an output of about 0.5 GW is carried out.

Experimental and numerical investigation on the influence of the diffuser blade setting angle on the performance of centrifugal compressor

Setting angle of the front blade row of tandem cascade diffuser was investigated experimentally to understand its influence on the performance of centrifugal compressor. Three diffusers with different setting angles were tested. The change of front blade setting angle mainly alters. The angle of attack (AOA) on the leading edge of front blades, which affects the surge point of the compressor. The throat area of the blade row is also modified, which affect the chock point of the compressor. With the increase of setting angle, performance curves of centrifugal compressor move to large flow rate side, the operation range is increased at the same time. In addition, numerical simulation was used to investigate the flow details on the passage of diffuser blades. Overall, the setting angle of front blade row has a significant influence of the performance of centrifugal compressor.

Design and Construction of Bamboo Stripping machine for Bamboo Basketry

Handicraft of bamboo weaving has been a tradition that has been inherited for a long time, by using bamboo strips to weave into shapes to make tools and appliances. The bamboo strips are from dividing the longitudinal bamboo trunks into thin strips. In which most farmers will make the strips by hand by using a big knife or sharp objects. As a result, it takes a long time to prepare the bamboo strips to be used in the weaving work. There is also a risk of accidents from the use of sharp objects, including the size of the bamboo strips that is not the same size. This research aims to design and construct bamboo strips by dividing the research into 2 steps: 1) designing and constructing bamboo strips and 2) testing the operation of the stripping machine. The designed machine can be easily moved because it is a small and lightweight machine which is designed using a single-phase electric motor with a voltage of 220 volts, 250 watts, etc. Power to drive the roller through the transmission belt to convey bamboo parts through two 7-degree sets of blades with sharp angles that are placed horizontally. The first blade acts to separate the bamboo parts with the bamboo strips and the second blade acts to sharpen the bamboo strips. The results of the working test of the stripping machine by adjusting the blade angle at 1 and the level into 4 values that are 3, 4, 5, and 6 degrees, it was found that the machine was able to produce bamboo strips in size 1.47, 1.20, 1.97 and 2.27 mm, respectively. The size of the punching line is suitable for weaving containers such as round bamboo basket, wicker basket, and bamboo basket, etc.

Modal parameter determination and chatter prediction for blade whirling: a comparative study based on symmetric and asymmetric FRF

Whirling has been adopted for the cost-effective machining of blade-shape components in addition to traditional end milling and flank milling processes. To satisfy the requirements of rotary forming in the blade whirling process, the workpiece must be clamped at both ends in suspension and rotated slowly during machining, which complicates the dynamics. This study aims to identify the dynamic characteristics within the blade whirling operation and present strategies for stability prediction. In this study, the dynamic characteristics of a whirling system are modeled by assuming symmetric and asymmetric parameters. Theoretical prediction frequency response function (FRF) results are compared with experimental results. Moreover, semi-discretization stability lobe diagrams (SLDs) obtained using the dynamic parameters of these models are investigated experimentally. The results show that the asymmetric model is more suitable for describing the whirling system, whereas the symmetric model presents limitations associated with the frequency range and location of measuring points. Finally, a set of airfoil propeller blade whirling operations is conducted to verify the prediction accuracy.

A Novel Direct Active and Reactive Power Control Method Using Fuzzy Super Twisting Algorithms and Modified Space Vector Modulation Technique for an Asynchronous Generator-based Dual-rotor Wind Powers

This work presents a novel direct active and reactive powers command (DARPC) scheme based on fuzzy super twisting algorithms (FSTAs) of an asynchronous generator (ASG) integrated into dual-rotor wind power (DRWP) systems. The DRWP has two sets of blades. So it is more efficient for collecting power from wind in comparison to a traditional wind turbine. The scientific works indicate that a DRWP could extract additional 20-30% power compared to a traditional wind turbine. The conventional DARPC control scheme using the conventional integral-proportional (PI) regulators (DARPC-PI) has considerable reactive and active power oscillations. In order to guarantee an effective DARPC technique for the ASG-based DRWP system and minimize these oscillations, FSTAs are used in this work. Both DARPC strategies are presented and simulated from two tests using Matlab software. Simulation results showed the effectiveness of the designed DARPC control technique especially on the quality of the provided active and reactive power comparatively to the traditional DARPC control scheme with PI controllers.

Strength analysis of the conceptual model of a main rotor blade spar with actuators

This paper concerns the conceptual design of a main rotor blade spar with actuators. A three-dimensional model of a main rotor blade is based on the preliminary geometric blade setting angle to increase the aerodynamic performance caused by different linear velocities of individual cross-sections. A modification of the blade setting angle results in a change of the angle of attack and influences the value of the lifting force in a given blade cross-section. The geometric setting angle was applied in designing both the main rotor blade spars and the blade. The overall dimensions of the blade depended on the available surface of the outmost blade airfoils. The important element of the designed spars was a cut in the form of a notch enabling the upper and lower crossbars of the designed spar to move during the operation of actuators. The FEM analysis was carried out on the parts of the designed blade spars. Three types of materials were compared in the finite element analysis. The internal stresses and displacements of the outmost edges of the crossbars were analyzed. The Catia V5 software was used for the designing work. The sections of the spars were analyzed using the Finite Element Method. The Pre/Post module of NX 12 was used for the FEM analysis. The displacement results were analyzed, which allowed us to determine their twist angle.

Numerical and Experimental Investigations on Inflow Loss in the Energy Recovery Turbines with Back-Curved and Front-Curved Impeller Based on the Entropy Generation Theory

Pump as turbine (PAT) is one of the economical and effective energy recovery devices in small hydropower stations. A back-curved PAT and a front-curved PAT were designed, and performance characteristics were studied, the accuracy of the numerical calculation was verified by comparing with the experimental results. The entropy generation theory was used to compare performance and energy loss of PATs. The results show that the high efficiency range of front-curved PAT is significantly wider than that of back-curved PAT. Under part-load condition (0.8Qd), design flow condition (1.0Qd) and over-load condition (1.2Qd), the efficiency of the front-curved PAT is 0.6%, 5.9% and 7.9% higher than that of the back-curved PAT, respectively. The energy loss in the PAT impeller mainly comes from the turbulent entropy generation rate which is mainly concentrated on the blade leading edge and trailing edge. Flow separation and flow shock caused by the mismatch between the relative flow angle and the blade setting angle are the main mechanisms of energy loss in impeller. In addition, the loss caused by the wall friction in the front-curved impeller is less than that in the back-curved impeller. Therefore, the entropy generation theory can provide guidance for the performance optimization of PAT.

Optimal design and setting of rotary strip-tiller blades to intensify dry season cropping in Asian wet clay soil conditions

Fine-textured clayey soils dominate Asian rice fields that are kept either fallow or cultivated with non-rice crops after harvest of monsoon rice. Use of seeding machinery compatible with the principles of conservation agriculture on such soils, however, has not been promising. Under these conditions – which predominate the population and poverty dense areas of coastal South Asia – such machinery fails to open a furrow or throws excessive soil out of the tilled furrow during strip-till seeding. This results in a poor seed coverage at planting jeopardizing crop establishment. In response, this soil bin study investigated strip-tillage blade designs and settings to optimize rotary strip-till system for wet clay soil conditions common in South Asian rice fields. Three designs of C type rotary blade (conventional, medium and straight) and two blade settings (four and six blades per row; 50 and 100 mm cutting widths) were tested at three blade operating depths (50, 75, and 100 mm) using a tillage test rig and a soil bin, and a high-speed camera to understand the processes of soil cutting, throwing, backfilling, and creation of furrow seedbed. The soil bin soil consisted of a wet sandy-clay-loam soil with a moisture content of 28.2% (85% of field capacity) and was compacted to the bulk density of 1440 kg m−3. Using the test rig, rotary speed of the blades was maintained at 480 rpm and forward speed at 0.4 m s−1. At four blades per row setting, all blades created high amounts of optimum clods (1–20 mm size). The conventional and medium blades threw too much soil out of the strip-tilled furrow while the straight blade created adequate backfill at 75 and 100 mm operating depths. At 6 blades per row setting, all blades produced high amounts of backfill at any depths, but the straight blade also produced the highest amounts of optimum clods and a uniform furrow. Considering machine and energy costs, blade performance, and the necessity of minimizing soil disturbance in strip-tillage, our study indicates that the use of straight blades (four blades per row) operated at a depth of 75 or 100 mm are more ideal. These specifications are likely to enhance strip-tillage stand establishment in fine-textured soils with high moisture contents, though further work is needed under actual field conditions to confirm suitability of the proposed strip-till system for crop establishment in currently fallowed as well as the intensively cropped lands of Asia.

Free vibration responses of 3D braided rotating cylindrical shells based on third-order shear deformation

3D braided composite has achieved attractiveness over the laminated composite due it some unique properties such as higher impact resistance, fatigue strength, stiffness in the thickness direction, anti-delamination capability, etc. In this study, the equivalent material properties of the composites are computed using bridging models base on a volume averaging method (VAM). Four steps 1 × 1 braided technique are introduced to manufacture the 3D braided rotating cylindrical shells panels. A third-order shear deformation (TSDT) with twelve degrees of freedom per node is used in the present eight nodded isoparametric 3D-finite element formulation (FEM). This theory has more capability compared to the other shell theories to predict the accurate results of the 3D braided shell. The generalized dynamic equilibrium equation of the present models is derived from Lagrange’s equation of motion. For moderate rotational speeds, the Coriolis effect is neglected. The correctness of the present finite element code is investigated by verifying with the existing results. The modals result of the rotating cylindrical shells (CYS) is computed at a different braided angle, braided volume fraction, aspect ratio, thickness ratio, curvature ratio, twist angle, blade setting angle, pre-cone angle, and rotational speeds, etc.

“Fast Track” Analysis of Small Wind Turbine Blade Performance

Small wind turbines (SWTs) can be significantly sensitive to variances in the blade geometry shape when their operation in relatively low ranges of Reynolds numbers is considered. An SWT case study, where an existing wind turbine prototype was equipped with a redesigned blade set, to increase its aerodynamic efficiency, is presented. The geometry modification process was targeted at maximizing the turbine power coefficient in the presumed point of low Reynolds operation. The applied design and analysis methods included practical implementation of previously established “Fast Track” procedure for wind turbine development. A newly prepared blade geometry and a reference blade set were examined numerically and experimentally. Selected design and assessment processes were supposed to be low resource demanding, making them possibly highly applicable in renewable energy industry. Therefore, the numerical analysis of both geometries was based on BEM (blade element momentum theory) equations. The research was expanded by model validation in small-scale wind tunnel tests to provide detailed information on BEM data reliability in comparison to the results of the experiment. The small-scale analysis, performed in Reynolds numbers below 100,000, provided information sufficient for evaluation of the redesigned blade. Implementation of the geometry obtained throughout the proposed procedure increased the rotor’s maximum power coefficient by 10%.

Wave-to-Wire Model of an Oscillating-Water-Column Wave Energy Converter and Its Application to Mediterranean Energy Hot-Spots

Oscillating water column (OWC) systems are among the most credited solutions for an effective conversion of the notable energy potential conveyed by sea waves. Despite a renewed interest, however, they are often still at a demonstration phase and additional research is required to reach industrial maturity. Within this framework, this study provides a wave-to-wire model for OWC systems based on an impulse air turbine. The model performs a comprehensive simulation of the system to estimate the attendant electric energy production for a specific sea state, based on analytical models of the primary (fixed chamber) and secondary (air turbine) converters coupled with the tertiary converter (electric generator). A rigid piston model is proposed to solve the hydrodynamics, thermodynamics, and hydrodynamics of the chamber, in a coupled fashion with the impulse turbine aerodynamics. This is solved with a novel method by considering the cascades as sets of blades, each one consisting of a finite number of airfoils stacked in the radial direction. The model was applied for two Mediterranean sites located in Tuscany and Sardinia (Italy), which were selected to define the optimal geometry of the turbine for a specified chamber. For each system, the developed analytical wave-to-wire model was applied to calculate the performance parameters and the annual energy production in environmental conditions typical of the Mediterranean Sea. The selected impulse turbines are able to convert 13.69 and 39.36 MWh/year, with an efficiency of 4.95% and 4.76%, respectively, thus proving the interesting prospects of the technology.

Design and Simulation of a Novel Planetary Gear Mixer for Dry Particle Materials

Background: Mixer with excellent performance is the essential premise for high-quality mixture production to ensure uniformity. In the fields of food, pharmacy, powder metallurgy and machinery industry, materials mixing is an indispensable process. At present, the mixing efficiency and performance of the traditional mixer are very low, which has its own limitations, and it is difficult to ensure the quality of the mixture, which seriously affects the safety and reliability of the mixture products such as synthetic drugs, chemical reagents, cement, synthetic fiber, etc. Objective: In order to improve the mixing performance by improving the mixing uniformity, volume utilization, reducing the mixing time and mixing blind area, a novel planetary gear mixer for dry particle materials is designed. Its blades can rotate and the angle of attack can be changed at any time, which realizes the multi-degree of freedom movement of the blades. Methods: Firstly, the shortcomings of three kinds of traditional mixers are compared and analyzed, a novel planetary gear mixer for dry particle is proposed and its structural characteristics are described. Then, the transmission system and blade parameters of the mixer are designed and calculated, and the blade parameters of the mixers are optimized based on ADAMS and EDEM. Finally, the comparative simulation experiment between planetary gear mixers and SHR-10A mixers is carried out. The experiment is used to inquiry on the mixing performance of the new planetary gear mixer. Results: The complementary cycloid was the ideal mixing trajectory of the blade. The most distinctive feature of this motion is that the attack angle of the blade can change in all directions. When the blade parameter p = 11, the Lacey index rises the fastest and the mixing degree is the largest, which indicates that the optimal mathematical model of the blade is ‘y2= 22x’. The comparison with SHR-10A mixer showed that spatial distribution of multi-degree of freedom blades in the new planetary gear mixer has strong dispersion effects on particles and better mixing performance. Conclusion: The planetary gear mixer for dry particle materials is a new type of mixer, which is composed of two sets of blades whose attack angle can be changed at any time. Convection and shear mixing dominate its mixing space, which is conducive to its rapid and full mixing, improving the mixing performance. The dry particle planetary gear mixer for dry particle materials has great developmental value and wide engineering application prospect. In this article, various patents have been discussed.