Blade System Research Articles

Simulation study of crack parameters’ effects on the vibration characteristics of a bladed disk system

As a key component of the turbo machine rotor in harsh operating conditions, high cycle fatigue failure and even cracks are common in bladed disks. In this paper, modal analysis was carried out for a single cracked bladed disk system, the effects of crack depth, crack height and rotating speed on its vibration characteristics were studied by the method of both numerical simulation and orthogonal test, and the effects of crack distribution on the vibration characteristics of multi-crack bladed disk systems were also studied. Finally, some conclusions have been drawn, they provide a fundamental understanding of blade health monitoring and fault prediction, and are important to improve the reliability and safety of turbine operation.

A Modular Modeling Method of Mistuned Blisk Based on State-Space Theory with Fitting Aerodynamic Excitation

In order to improve the solution efficiency of vibration characteristics for the mistuned blisk, a modular method combined with state-space method based on lumped-parametric model is developed for the first attempt, which provides a general modeling framework which can be employed to conveniently construct the lumped-parametric models of bladed disk systems with multiple mistuning and variable blade number. It is noteworthy that a pressure fit in the axial-span-pressure space is performed to obtain the continuous equations of aerodynamic forces according to the aerodynamic loads acting on the blade surface. The function of traveling wake excitation is established by considering the rotational velocity. Subsequently, 1N-degree-of-freedom (1N-DOF) and 2N-DOF lumped-parametirc models are respectively used to construct the mistuned blisk. A modular solution method of multiple mistuned lumped-parametirc model is derived from the controllable canonical form and minimum realisation, which reveals that the minimum dimension of the state space is two times of its DOF. The correctness of the present method is varified by several comparisions. Vibration localization is found in the transient response and steady-state response of the blisk. The effects of the mistuning on the blades and the disk are discussed, respectively.

Experimental and Computational Study of a Rotating Bladed Disk with Under-Platform Dampers

There has been an extensive amount of work developing reduced-order models (ROMs) for bladed disks using single-sector models and a cyclic analysis. Several ROMs currently exist to accurately model a bladed disk with under-platform dampers. To better predict the complex nonlinear response of a system with under-platform dampers, this work demonstrates how two linear models can determine bounds for the nonlinear response. The two cases explored are where the under-platform damper is completely stuck and also where the damper slides without friction. This work utilizes the component mode mistuning method to model small mistuning and a parametric ROM method to capture changes in properties due to rotational speed effects. Previously, these ROM methodologies have modeled freestanding bladed disk systems. To evaluate the ROM in predicting the bounds, blade tip amplitudes from the models are compared with high-speed rotating experiments conducted in a large, evacuated vacuum tank. The experimental data were collected during testing using strain gauges and laser blade tip timing probes. The blade amplitudes of the tip timing data, strain gauge data, and computational simulations are compared to determine the effectiveness of the simplified linear analysis in bounding the nonlinear response of the physical system.

Study on rubbing characteristics of blade-casing model considering transverse cracks

The study focuses on the nonlinear vibration response of a blade system with cracks subjected to coupled rub-impact failure. Initially, the cracked blade system is mathematically modeled based on the Lagrangian theorem, and its motion is derived using Hamilton's principle. Secondly, a revised rubbing model is proposed with consideration of varying depths and locations of the cracks. Subsequently, the influences of parameters related to crack failure and rub-impact are comprehensively investigated. Finally, a novel crack influence index is also proposed to study the impact of resonance effect on crack failure. Different dynamic characteristics, along with the resonance coupling effect, were compared to demonstrate the working mechanism. The results indicate that severe rubbing occurred as the crack depth increased and the crack position decreased. The impact of crack depth on rubbing deformation than that of crack location. In addition, larger cracking depths and smaller cracking locations result in larger cracking influence coefficients, while the resonance effect disrupts this influence law in some cases.

Цилиндрический завихритель потока с удлиненной хордой лопастей

Introduction. Development of vortex apparatuses — devices for swirling flows of liquids and gases — remains an urgent scientific and engineering task. The design of counter vortex damper flow swirling apparatus at the idle water outlet of Belorechenskaya hydroelectric power plant (HPP) is considered. The purpose of the study is to develop an effective counter vortex damper of excess kinetic energy of water flow. Materials and methods. Analytical methods of classical hydro-mechanics are used. The conceptual basis of the research is the fundamental equality of the geometric characteristic of the vortex apparatus by Abramovich (the Abramovich number) to the Chigier-Beer swirl number. Results. It has been found that geometrical characteristic of the cylindrical vane swirler does not depend on radius of exit edges of blades which swirl the flow, but depends on the angle of bevel of blades at this radius. It allows, according to fundamental equality of Abramovich and Chigier-Beer numbers, either to shift the blades along the swirl chamber radius or to perform them with elongated chord, leaving the hydraulic characteristics of the swirl apparatus and swirled flow unchanged, preserving the bevel angle. Lengthening the chord of the vortex apparatus blades increases the reliability and quality of formation of the swirling flow. It has been proved on the base of differential equation describing the flow lines in the cylindrical swirl chamber that chord of a swirl apparatus prolonged blade flowing smoothly around the flow should have a shape of a logarithmic spiral. It is shown that the vortex apparatus made in the form of a vane system of logarithmic spirals forms a flow with potential rotation superimposed on the potential flow. Conclusions. The design of counter vortex damper of flow energy at the outlet of Belorechenskaya HPP with a system of blades in the form of logarithmic spirals has been analyzed. It is offered to recommend the considered design as a typical one for hydraulic units of medium head.

AN INNOVATIVE APPROACH TO THE DEVELOPMENT OF NEW SCHEMES OF HORIZONTAL DIRECT-FLOW HYDRAULIC TURBINES

The impact of the rapid development of renewable energy sources and the reduction of electricity production by traditional generating capacities on the change in the development trend in world energy is analyzed. This led to a sharp change in the priorities of the national energy policy of Ukraine with an increase in the capacities of renewable energy sources, which in 2035 should be 25 billion kWh of generating capacity against 2,8 billion kWh in 2018. It is shown that such trends require the growth of balancing highly maneuverable capacities in hydropower to regulate load schedules and ensure stability and reliable operation of combined power systems. Under such trends, Ukraine is transitioning to a new innovative model of the operation of the electric power industry in the conditions of the gradual creation of a full-fledged energy market and the planned integration of the energy system of Ukraine with the European energy system (ENNSO-E). It is claimed that the problem of covering peak loads becomes acute in the modern conditions of power system operation. This makes it necessary to pay more attention to the operation of maneuverable hydropower equipment in order to optimize the distribution of loads to consumers. It is proposed to solve these problems comprehensively, both by developing new blade systems and water passages of traditional type hydroturbines, and by improving the working process due to innovative constructive solutions for the layout of hydropower equipment for new hydropower facilities. Potetenko O. V. (Professor of the Department of Hydraulic Machines named after G. F. Proskura, NTU "KhPI") founded a scientific direction in which for 10 years the tasks of introducing high-speed bladed hydraulic turbines at high heads in the development of new design schemes in hydropower were developed and researched. Dozens of patents for inventions and utility models are the results of this. Further development of innovative schemes of horizontal capsule hydraulic units, which is related to the features of the working process, is aimed to achieve high average operating efficiency while simultaneously expanding operation and reliability areas of the proposed design schemes.

Design and Development of an Engine-Operated Weeding Machine for Wheat Farm

Weeds constitute a serious problem to wheat crops and cause a great loss to the yield. Manual weeding is labor-intensive and time-consuming. Chemical weed control has a negative impact on both the environment and humans. To overcome these problems, an engine-operated weeder was designed and developed at Asella Agricultural Engineering Research Center (AAERC). The developed weeder was designed on the basis of agronomic and machine parameters. The developed prototype weeder consists of the mainframe, weeder blade, ground wheel, and power transmission system. The rated engine speed of 2800 rpm was reduced to 46 rpm of the ground wheels by using bevel gear, chain, and sprocket mechanism in three stages. The overall dimension of prototype weeder was 1650 mm in length, 800 mm in width and 1050 mm in height. The total production cost of the engine-operated weeder was 11,409.92 ETB. This paper is focused on machine design analysis and fabrication of prototype. Performance evaluation of propototype would be addressed in the next coming paper.

Computational Fluid Dynamics Modeling Analysis of a Martian Rotorcraft With Individual Blade Control

Abstract Computational fluid dynamics (CFD) analysis was conducted on a proposed blade root-actuated individual blade control (IBC) system for future Martian rotorcraft. IBC offers many potential benefits to rotary-winged exploration of Mars, including precision control of rotor blade forces. This study seeks to provide an estimate of rotor blade force and system power as a basis for concept feasibility analysis and experimental prototyping. ansys fluent was used to compute blade pitching moment, lift, and drag under various feathering waveforms, amplitudes, biases, and frequencies. It is determined that the rapid feathering characteristic of IBC has a non-negligible impact on blade forces. It is also found that actuators with power ratings on the order of 101 W are likely sufficient for blade actuation on Martian rotorcraft.

Prediction of energy and cavitation characteristics of high specific speed Francis hydraulic turbines

BACKGROUND: Cavitation is a phenomenon that occurs in vane hydraulic machines: pumps, hydraulic turbines, when the pressure in a certain area of the flow reaches the level of saturated steam pressure. Its occurrence depends on the design and mode of operation of the hydraulic turbine. In order to design a hydraulic turbine with high cavitation qualities, it is necessary to be able to reliably predict this phenomenon.
 AIMS: The article describes approaches to modeling the operation of Francis hydraulic turbines based on the ANSYS software package.
 METHODS: Using quasi-3D methods was modeled turbine blade system with 75 meters head. Hydrodynamic computation carried out in single-phase and two-phase formulations using the ANSYS CFX package.
 RESULTS: The design of a flow path Francis turbine 3D solid model with a specific speed coefficient ns =283 has been completed. The flow part of the hydraulic turbine includes a spiral case, a stator, a guide vane, an impeller and a draft tube. Computational modeling of the flow of a single-phase viscous fluid in a hydraulic turbine in different modes was carried out to construct a universal characteristic. The optimal efficiency is found and the flow characteristics are calculated. The losses in the elements of the flow part of the hydroturbine under various operating modes are determined, the zone of optimal operation is found. The cavitation flow is calculated using a two-phase flow model (water-steam). For both sides of the impeller blade, a pressure distribution was obtained, which can be used to judge the possibility of cavitation in areas where the pressure of the water column is less than the vaporization pressure. The value of the critical cavitation coefficient for the three most unfavorable modes was determined, and the dependence of the efficiency on the cavitation coefficient was constructed. The area occupied by steam on the blade during cavitation flow is visualized, its area is determined relative to the surface area of the blade.
 CONCLUSIONS: The designed hydraulic turbine has good energy and cavitation qualities, confirmed by the calculation. This version of the hydroturbine can be used as the initial one with further optimization of the blade system and elements of the flow path, to improve the energy and cavitation qualities.

Design and Development of an Engine-Operated Weeding Machine for Wheat Farm

Weeds constitute a serious problem to wheat crops and cause a great loss to the yield. Manual weeding is labor-intensive and time-consuming. Chemical weed control has a negative impact on both the environment and humans. To overcome these problems, an engine-operated weeder was designed and developed at Asella Agricultural Engineering Research Center (AAERC). The developed weeder was designed on the basis of agronomic and machine parameters. The developed prototype weeder consists of the mainframe, weeder blade, ground wheel, and power transmission system. The rated engine speed of 2800 rpm was reduced to 46 rpm of the ground wheels by using bevel gear, chain, and sprocket mechanism in three stages. The overall dimension of prototype weeder was 1650 mm in length, 800 mm in width and 1050 mm in height. The total production cost of the engine-operated weeder was 11,409.92 ETB. This paper is focused on machine design analysis and fabrication of prototype. Performance evaluation of prototype would be addressed in the next coming paper. Keywords: Design analysis, develop, wheat, weeds, weed control, weeding machine DOI: 10.7176/ISDE/13-1-01 Publication date: March 31 st 2023

Pengaruh besar sudut potong mata pisau tipe flate terhadap hasil cacahan plastik pada mesin pencacah

Given that plastic is typically only used once, increasing levels of plastic waste in TPA make it difficult for Indonesia and even the rest of the world to solve the problem of plastic trash (final disposal sites). Performing a field investigation and literature review comes first. Making a blade model that is distinct from the previous one involves using the findings of the field survey and the literature study. According to the examination of the most recent blades, which have angles of 30° and 60°, the blade system models can be compared and it can be shown that the results of the number of capacities and the results of the size of the pieces are issued. Waste materials that are cut into plastic bottles, PET or PETE bottle caps, and LDPE (low density polyethylene) plastic bags. The findings for a blade with a 30° angle are 1.8 kg/hour for plastic bottles, 0.780 kg/hour for bottle caps, and nil capacity for plastic bags since the bag is wrapped around the blade. Due to the angle's lack of sharpness or tendency to be moreblunt, this blade tends to only clamp a large amount of plastic. While the 60° blade angle produces 0.200 kg/hour of plastic bags, 1.5 kg/hour of plastic bottles, and 1.3 kg/hour of bottle caps. Since the 60° angle blade has a better sharp angle for slicing or breaking plastic waste into smaller bits, it can be seen that it produces the highest capacitance

Semi-analytical modeling and experimental verification of a flexible varying section disk–blades system with elastic supports

A semi-analytical model of a flexible varying section disk–blades (FVSDBs) system with elastic supports is proposed, where the spin softening, centrifugal stiffening, and Coriolis force effects of the system are considered. Timoshenko beams with a stagger angle are used to simulate blades, and a varying section wheel based on plate theory is used to construct the disk. Hamilton’s principle and Galerkin method are utilized to derive the differential governing equations of the FVSDBs system. The proposed semi-analytical model accounts for the lateral vibration of the disk, and the longitudinal and lateral vibration of the blades. Besides, the validity of the proposed model has been verified by comparing the natural frequencies, mode shapes, and vibration responses obtained from the proposed model, finite element model (FEM), and experiment. The results indicate that the proposed semi-analytical model has high precision and computational efficiency, which can provide an alternative scheme for predicting the vibration characteristics of varying section disk–blades and overcoming the high computational cost of finite element models.

Axial-Flow Pump with Enhanced Cavitation Erosion Resistance

Axial-flow pumps, in addition to providing high anti-cavitation properties, must have high anti-erosion properties to ensure the required lifetime of the pump. Erosion damage of surfaces occurs when the net positive suction head (NPSH) significantly exceeds its critical value. The object of the study in this article is the axial-flow pump with a specific speed of 600 in two alternatives: № 1 and № 2. By analysis of the flow in the impeller blade systems, the ratio value between the NPSH, which ensures the absence of erosion, and the NPSH3, at which pump operational failure occurs, was determined. Impeller variant № 1 did not provide the required ratio. Impeller variant № 2 had higher cavitation qualities, and the required ratio was achieved for it. Energy, cavitation, and erosion characteristics of the axial-flow pump with impeller № 2 in rotational frequency n = 2000 rpm were investigated. Easily breakable paint coatings were used for the accelerated study of cavitation erosion. The experiment was carried out at three different flow rates and confirmed the assumptions made—the pump with impeller № 2 was not affected by cavitation erosion at the optimum flow rate. Patterns of erosion zones were accompanied by calculations of vapor zones in the impeller. At flow rates less than the optimum, cavitation disruptions occurred and appeared behind the vapor region. As a result, the condition of ensuring erosion-free flow in the impeller of an axial pump with a specific speed of 600 was obtained, ensuring the ratio NPSH/NPSH3 > 2.5. Recommendations on designing of erosion-free flow part of the axial pump impeller were also obtained.

Influences of blade crack on the coupling characteristics in a bladed disk with elastic support

In aero-engines, the blades are exposed to severe environments and subjected to complex conditions, which can cause damage and cracks. Existing analytical models focus primarily on the blade crack in a single blade. Even in the cracked-bladed disk system, most theoretical models are based on the rigid disk assumption, and few studies pay attention to the boundary conditions of the disk. A new model is proposed in this paper to compensate for deficiencies in existing theoretical models. The flexible disk and blade are deduced based on Kirchhoff plate and Timoshenko beam theories. The crack-caused stiffness loss is calculated through the released strain energy. In addition, the elastic support on the disk's inner edge is simulated by the linear spring stiffness and torsional stiffness. The accuracy of the developed model is verified by comparing it with the finite element method and experimental test. After that, the influences of the crack depth and crack location on the coupling characteristics of the system are systematically investigated. The results indicate that blade crack mainly affects the blade-predominated modes, leading to the mistuned disk mode shapes, which are symmetrically distributed along the line between the cracked blade and the disk center. Moreover, as the blade crack becomes severe or approaches the blade root, the first natural frequency of the paired orthogonal modes decreases; the first mode shape of the paired tuned high nodal diameter degenerates into mistuned low nodal diameter; the new coupling characteristics between the mistuned disk and elastic support become more stronger. The proposed methodology can serve as a theoretical basis for diagnosing faults and monitoring safety in the bladed disk coupling system.

CONSTRUCTION AND PERFORMANCE EVALUATION OF TWO STAGED THREE BLADED SAVONIUS VERTICAL AXIS WIND ENERGY CONVERSION SYSTEM

This study is intended to increase the rotor performance of the Savonius wind rotor, by increasing the numbers of blades of the already existing two blades Savonius vertical axis wind turbines (VAWTs) to three which was designed to increase the Savonius wind rotor performance. Two stage three bladed wind turbine system has been designed and constructed. The system was made up of six split drums which were welded together to form a concave shape to capture wind from all directions, with a shaft to pass through the midst of the welded drums which was then mounted on a tower of about 15 m high, which in turn will cause the rotor to rotate. This was then connected to a 12 V Generator. The wind turbine converts the kinetic energy available in the wind to produce electricity, using the Generator with output power of 60 W. The results obtained showed that the system was able to accept wind from any direction and commenced rotation as soon as the wind speed of 3.3 m/s (cut in) was available at the site. The minimum and maximum power outputs of 5.14 W and 13.34 W, corresponding to wind speeds of 7.2 m/s and 9.4.5 m/s were recorded respectively. Similarly, for a rotation per minute of 811 rpm a voltage of 7.14 V was generated. Hence for a two stages three blades Savonius the performance was 12.2 %, as against a single stage two blades Savonius whose performance was 7%, a deviation of 5.2 %.

Методика проектирования и оптимизации лопастной системы радиально-осевой гидротурбины

A technique for designing the blade systems of Francis turbine is proposed. Starting with the determination the main parameters of the turbine components, where it is compatible with the operation of a hydraulic turbine at a given head. Also, the diameter of the impeller required to generate the nominal power. Then, using the realizing of the quasi-three-dimensional approach, the shape of the blade is obtained as a first approximation for a given blade, a series of calculations of three-dimensional single-phase and twophase viscous flow is performed to determine the efficiency of the turbine at different operating modes, the cavitation properties of the turbine, respectively. The critical cavitation coefficient is determined for three operating points of hydraulic turbines. Using Multi-objective Genetic Algorithm (MOGA), the optimization of energy and cavitation properties is carried out for three operations pointes. The mathematical model is based on the Latin hypercube method. As a result of the optimization, a significant improvement in the efficiency of the hydraulic turbine has been obtained, especially at partial loads.

Effect of the Blade-Coating Conditions on the Electrical and Optical Properties of Transparent Ag Nanowire Electrodes.

Optimizing the coating conditions for a doctor blading system is important when seeking to improve the performance of Ag nanowire electrodes. In this study, the effect of the blading height and speed on the optical and electrical properties of Ag nanowire electrodes was investigated. Ag nanowires were first spread on a PET substrate using a doctor blade with differing heights at a fixed blading speed. An increase in the blading height resulted in the degradation of the optical transmittance and stronger haze due to the higher probability of Ag nanowire agglomeration arising from the greater wet thickness. When the blading speed was varied, the optical transmittance and haze were unaffected up until 20 mm/s, followed by minor degradation of the optical properties at blading speeds over 25 mm/s. The higher speeds hindered the spread of the Ag nanowire solution, which also increased the probability of Ag nanowire agglomeration. However, this degradation was less serious compared to that observed with a change in the blading height. Therefore, optimizing the blading height was confirmed to be the priority for the production of high-performance transparent Ag nanowire electrodes. Our study thus provides practical guidance for the fabrication of Ag nanowire electrodes using doctor blading systems.

Effect of 3D Shape of Pump-Turbine Runner Blade on Flow Characteristics in Turbine Mode

The effect of blade spatial profiling with the help of tangential blade lean of Francis pump-turbine runner with heads up to 200 m on the flow structure and energy characteristics was numerically investigated. A flow part model of Francis pump-turbine of the Dniester pumped storage plant was adopted as original version. Two new blade systems were designed, which differed from the original version by mutual position of cross-sections in tangential direction: with positive and negative lean, while the shape of the cross-sections themselves remained unchanged. Modeling of the viscous incompressible flow in calculation domain, which contains one channel of the guide vane and the runner, for three variants of flow parts, was performed using the IPMFlow software based on numerical integration of the Reynolds equations with an additional term containing artificial compressibility. To take into account the turbulent effects, the SST differential two-parameter turbulence model of Menter is applied. Numerical integration of the equations is carried out using an implicit quasi-monotonic Godunov scheme of second order accuracy in space and time. The study was carried out for models with runner diameter of 350 mm in a wide range of guide vane openings at reduced rotation frequencies corresponding to the minimal, design and maximal heads of the station. A comparison of pressure fields and velocity vectors in the runners, pressure graphs on runner blades, distribution of velocity components at inlet to a draft tube, and efficiency of three variants of flow parts are presented. It was concluded that calculation domain with the new RK5217M2 runner with negative tangential lean has the best characteristics. An experimental study of three runners on a hydrodynamic stand are planned

A novel mathematical model for the design of the resonance mechanism of an intentional mistuning bladed disk system

Abstract. Bladed disk systems with advanced functions are widely used in turbo-machineries. However, there are always deviations in physical dynamic properties between blades and blades due to the tolerance and wear in operation. The deviations will lead to vibration localization, which will result in high cycle fatigue and accelerate the damage of the bladed disk system. Therefore, many intentional mistuning patterns are proposed to overcome this larger local vibration. Previous studies show that intentional mistuning patterns can be used to reduce the vibration localization of the bladed disk. However, the determination of the resonance mechanism of the intentional mistuning bladed disk system is still an unsolved issue. In this paper, a novel mathematical model of resonance of an intentional mistuning bladed disk system is established. Mistuning of blades and energy resonance are included in this theoretical model. The method of the mechanical power of the rotating blade for one cycle is applied to obtain the resonance condition. By using this theoretical model, the resonance mechanism of an intentional mistuning bladed disk is demonstrated. The results suggest that the ideal results can be obtained by adjusting the intentional mistuning parameter. This paper will guide the design of the dynamic characteristics of the intentional mistuning bladed disk.

The Numerical and Experimental Evaluation of a Coupled Blade Dynamic Limit Response With Friction Contacts

Abstract Increasing demand for turbine power and efficiency requires larger and higher loaded turbine blades, which in turn requires the consideration of aeromechanical interactions. Whilst CFD tools can reliably predict stability using aerodynamic damping as an indicator, the component of mechanical damping also needs consideration. An understanding of the mechanical damping in the system becomes key to a robust blade design. Mechanical damping for such a part comes predominantly from friction occurring at the coupling contact faces. It is well established and published that such contact forces are nonlinear in relation to the relative movement at the contact interface. Moreover, contact area, the rigidity in the contact, friction coefficient, and normal contact force must also be considered and included as parameters that influence the result. Consequently, the level of system damping is not a constant and depends highly on the system response itself, as well as the other aforementioned parameters. In the case of self-excited vibrations such as flutter, the evaluation of the damped limit response is a part of the blade design process. A tool has been developed to numerically simulate contact friction forces with the intention of parametrically evaluating the limit response and relating this to the mechanical integrity of the part. This paper presents the modeling of a coupled blade system with friction contact forces, results coming from this evaluation, and a comparison with test data.