Strength Of Blades Research Articles

Design and computational fluid dynamics analysis of the last stage of innovative gas-steam turbine

Research regarding blade design and analysis of flow has been attracting interest for over a century. Meanwhile new concepts and design approaches were created and improved. Advancements in information technologies allowed to introduce computational fluid dynamics and computational flow mechanics. Currently a combination of mentioned methods is used for the design of turbine blades. These methods enabled us to improve flow efficiency and strength of turbine blades. This paper relates to a new type turbine which is in the phase of theoretical analysis, because the working fluid is a mixture of steam and gas generated in a wet combustion chamber. The main aim of this paper is to design and analyze the flow characteristics of the last stage of gas-steam turbine. When creating the spatial model, the atlas of profiles of reaction turbine steps was used. Results of computational fluid dynamics simulations of twisting of the last stage are presented. Blades geometry and the computational mesh are also presented. Velocity vectors, for selected dividing sections that the velocity along the pitch diameter varies greatly. The blade has the shape of its cross-section similar to action type blades near the root and to reaction type blades near the tip. Velocity fields and pressure fields show the flow characteristics of the last stage of gas-steam turbine. The net efficiency of the cycle is equal to 52.61%.

Experimental and numerical failure analysis of horizontal axis water turbine carbon fiber-reinforced composite blade

High-performance composites are used in many applications due to their design flexibility, corrosion resistance, high strength-to-weight ratio, and many other excellent mechanical properties. In this study, the location and magnitude of failure initiation in horizontal axis water turbine carbon fiber reinforced polymer (CFRP) blades with different lay-up orientations were investigated. Unidirectional [0°]4 and cross-ply [0°/90°]S layups were selected to study the effect of the buildup direction on the failure of the composite water turbine blades. A finite element analysis (FEA) model was generated to examine the stresses along blade span under both flexural and hydrodynamic loads. Flexural destructive tests were conducted to validate the results obtained from the numerical simulations. In addition, a blade element momentum theory model was created to calculate the hydrodynamic forces acting along the span to determine the maximum loading radial location, which was used for the fixture design and FEA simulation input. Both unidirectional and cross-ply composite blades were tested for failure. There was a general agreement between the experiments and simulations, which validated the results. Moreover, FEA simulations were performed to apply the load to the samples with different pitch angles (−10°, −5°, 0°, 5°, and 10°). Even though the unidirectional CFRP composite blades showed higher strength at 0° pitch angle than the cross-ply blades, the strength of the unidirectional blade dropped significantly when the load was applied with different pitch angles other than 0°, while the strength of the cross-ply blades was less responsive to this pitch angle variation.

Structural Design and Stress Analysis of a Helical Vertical Axis Wind Turbine Blade

In this study, a Computational Fluid Dynamics (CFD) model is designed to investigate the structural analysis of a helical Vertical Axis Wind Turbine (VAWT) blade which is using National Advisory Committee for Aeronautics (NACA) 0018 airfoil and numerical calculations are conducted by using Comsol Multiphysics. The main objective of this study is to determine that the strength of the turbine blade against bending caused by increased wind speeds is sufficient for the selected turbine blade material. This paper presents also an investigation of the effects of different wind speeds on the structure of a helical VAWT blade that is fixed to the support arm which is attached to the VAWT’s main shaft. In this study, a turbine blade which is placed in an air flow field is subjected to approaching strong wind with different velocities. The model solves for the flow around the blade and the structural displacement due to the fluid load. This investigation consists of two main parts: Solving for the fluid flow around the turbine blade with a free stream velocities of 1, 3, 5, 7, and 9 m/s, and Studying the deformation of the turbine blade caused by the fluid load. The risk of failure according to the von Mises criterion for the ductile materials such as aluminum is also investigated.

Prediction of high-cycle fatigue strength in a Ti-17 alloy blade after foreign object damage

Foreign object damage (FOD) tests and high-cycle fatigue (HCF) tests were carried out for Ti-17 titanium alloy simulation blades. The results showed that damage notches could be divided into semicircular and deflection types. The HCF strength of deflection-type specimens was lower than that of semicircular-type specimens. FOD and fatigue properties were characterized by scanning electron microscopy. The extrusion zone of deflection notches was inclined, reducing the fatigue strength compared with semicircular notches. A back-propagation neural network-based method for predicting the HCF strength of FOD simulation blades was developed, for which the prediction error was small.

СВОБОДНЫЕ КОЛЕБАНИЯ ЛОПАТОК ОСЕВОГО КОМПРЕССОРА ГАЗОТУРБИННОГО ДВИГАТЕЛЯ

The required level of reliability of modern gas turbine engines cannot be achieved without ensuring the vibrational strength of the compressor blades. One of the tasks of ensuring vibrational strength is to determine the frequency spectrum of free vibrations, as well as the arising forms of vibrations. Moreover, the most reliable results are achieved by combining experimental and theoretical research methods. Experimental studies of the free vibrations of the blades were carried out by the time-dependent holographic interferometry method. A description of the experimental stand is given, the features of using optical equipment and processing units are indicated. The implemented algorithm for conducting experimental studies is described, the features of the digitization of optical signals implemented in the developed software are indicated, the mathematical equations used in the implementation of this software are presented, and some emerging experimental forms are illustrated. To verify the experimental data based on the finite element method, an updated mathematical model of the free vibrations of compressor blades has been developed. The characteristics of the finite element from which the mathematical model is formed, the basic equations used in the simulation of free vibrations are given. As an object of study, we considered a compressor blade 54 mm high and 37 mm long chord with a peripheral section twist angle of 17°, the considered blade is made of a titanium alloy. For this blade, some waveforms were obtained, the location of the nodal lines was shown, and data obtained experimentally and analytically were compared. An analysis was made of the frequency spectrum of the natural oscillations of the compressor blades, which showed that the difference between the vibration frequencies obtained by experimental and numerical methods for the same modes does not exceed 5 %.

Improving wind turbine blade based on multi-objective particle swarm optimization

This paper studies a new method for optimizing the design of wind turbine blades. Compared with the existing blade design methods, the proposed method not only considers the structural strength and stiffness of the blade but also considers the noise and power generation efficiency of the blade. The method utilizes a multi-objective particle swarm optimization method and the finite volume method in combination to meet the strength and stiffness requirements of the wind turbine blade, improve its aerodynamic performance and reduce its noise. In the study, the geometries of the blade used by a 2 MW wind turbine are taken as the initial parameters of the target blade and MATLAB and ANSYS are employed to perform the optimization and finite element analysis based performance calculations. Then an intelligent optimization algorithm was developed for achieving a quiet and efficient wind turbine blade. In such a multi-objective optimization algorithm, both structural strength, stiffness, noise reduction, and aerodynamic performance of the blade are taken as objective functions. The simulation results have shown that through optimization, the blade noise was reduced by 3.1 dB and the power coefficient was increased by 6.9%. Moreover, it is found that the blade’s structural strength and stiffness are also improved after optimization. This implies that the proposed algorithm is also helpful to further reduce the manufacturing materials and costs of wind turbine blades.

Measuring-Diagnostic System for Monitoring and Evaluating the Operational Reliability of Rotor Blades for Aircraft Gas Turbine Engines by Acoustic Emission Method

Diagnostics of the rotor blades of aircraft gas turbine engines at pre-operational stage and later on during repairs is carried out by instrumental methods of non-destructive testing. The requirements for increasing operational reliability and safety of flights require a search for new solutions in assessing the strength of rotor blades at an early stage of damage development. For these purposes, one of the perspective directions is the development of acoustic emission methods. This article represents an experimental setup and a measuring-diagnostic system for assessing the operational reliability of rotor blades by the acoustic emission method. It also discusses the results of testing.

A method for evaluating the edge strength of soil-cutting parts of forestry machines

One of the main factors that determine the resistance of blade working bodies against damage under dynamic loads is their resistance to plastic crumpling, brittle or fatigue failure. Hard alloys that strengthen the blades of tillage parts are more brittle materials than steel, so the blunting of their edges is caused by the formation of cracks, their gradual growth or microchipping, even from a possible single impact of a solid inclusion in the soil. In addition to the usual brittle fracture of hard alloys, fatigue failure occurs under cyclic impact conditions. (Research purpose) The research purpose is in identifying the pattern of destruction of the blade edge of soil-cutting parts of forestry machines and theoretically justifying the algorithm for assessing the strength to determine the rational thickness of the wear-resistant coating during hardening. (Materials and methods) The article presents the main regularities of the influence of material properties and geometric parameters of the blade on the radius of rounding. (Results and discussion) The process of breaking the edge of the blade of hardened working bodies of forestry machines has been studied. The claim that the blunting of the blades is mainly due to its destruction and not to wear has been proved. The article presents a method for evaluating the strength of bimetallic blades of soil-cutting parts of forestry machines. It was found that the blunting of the blade occurs as a result of edge destruction in the process of multiple impacts of solid soil inclusions along the edge of the blade. (Conclusions) The article shows that the destruction of the edge of the blade leads to blunting of soil-cutting parts, which affects their performance. It was found that the sharpness of a self-sharpening hardened blade is determined by the thickness of the reinforcing layer and its ability to resist destruction under impact.

Technique for Evaluating the Strength of Composite Blades

The paper presents a technique for designing and investigating the strength of a composite blade on an example of a mine ore ventilation fan, considering aerodynamic loads acting on a blade airfoil surface. The technique is based on the use of the finite element method in a combination with the theory of multilayer shells to determine the dynamics and strength of the composite airfoil, as well as the methods of the computational fluid dynamics, namely the Reynolds equations, for modeling an air movement in a fan passage to determine aerodynamic loads. A static strength estimation is based on an application of the Hashin strength criterion. An analysis of the results of strength calculations considering aerodynamic forces indicates a necessity of accounting them for thin-walled composite elements. A possibility of varying a thickness of the shell and taking it into account using the presented method allows to achieve an optimal ratio of strength and weight indices. A buckling analysis of the composite shell under an action of complex loading, based on methods of the linear stability theory, as well as calculations of natural frequencies and natural frequencies with regard to a prestressed state from an action of static loads, completes the technique. The results of the research allow to conclude on an applicability of the presented methodology for analyzing the strength of composite blades and an efficiency of the proposed design of the airfoil, as well as a possibility of its use to create real rotary machines.

Mechanical Analysis of a Scraping Method to Remove Attached Barnacles

In order to clean the marine fouling attached to marine steel piles, a scraping method is proposed in this paper. Barnacles were used to represent a typical object needing removal, in order to estimate the maximum force required in the equipment designed for use in this method. On the basis of the orthogonal cutting theory and the peel zone method, a scraping method and its cutting force model are proposed in this paper for the surface cleaning of marine steel piles. The finite element method was used to verify the analytical model errors. The comparison showed that the relative errors of the cutting force are less than 10%. Our model can be used for cutting force estimation in cleaning equipment design. Our analysis shows that the blade rake angle has a large effect on the cutting force and that the optimum blade rake angle design is a compromise between blade strength and cutting force. We conclude that increasing the blade rake angle can reduce the cutting force in this scraping process; a medium blade rake angle [30°, 60°] is recommended, considering both cutting force and blade strength.

Hydrodynamic characteristics of bio-inspired marine propeller with various blade sections

ABSTRACT Not only economic pressures but also environmental demands and regulatory requirements bring a great interest in improving marine propeller efficiency. The design of a bio-inspired marine propeller with various blade sections is a novel field of investigation in marine hydrodynamics. The difference between the conventional propeller and bio-inspired propellers is the profile of the blade section, and the other geometric characteristics of bio-inspired propellers are the same as those of conventional propeller. In this present investigation, the geometrical features of the seagull, merganser, teal and owl wings are applied to the blade sections of marine propellers for study. The hydrodynamic characteristics, pressure distribution, tip vortex and blade strength are investigated. The numerical results indicate that the thrust and torque coefficients of the four bio-inspired propellers are almost higher than those of conventional propeller under the condition of constant advance coefficient. The bio-inspired propellers can improve the efficiency of the marine propeller. In addition, a smaller pressure difference is produced by the bio-inspired propellers in the vicinity of the leading edge, and therefore the strength of tip vortex is weakened.

Assessment of Blade Strength for Small Wind Turbine Applications

Small Wind Turbines (SWTs) are an increasingly developing Renewable Energy Source, thanks to the gradual popularisation of the prosumer energy generation approach. This, however, requires maximum safety of the machine, working next to households. Reliability is also necessary from the financial point of view, as SWTs should withstand 20 - 30 years of operation without any serious failure to ensure investment profitability. The weakest SWT element is arguably its most exposed one - the rotor - hence the important role played by the blade strength tests. The experimental analysis becomes preferable with increasing popularity of new materials (composites) and production techniques (additive manufacturing). This paper sets out to develop a test stand for static strength examination of 3D-printed SWT blades. This kind of objects is often considered as more vulnerable to structural failures than those created via machining techniques, due to their anisotropic structure, so ensuring structural integrity is crucial for safety reasons.

Evaluation of the wear resistance and strength of the ice hockey shoes blades and the sticks

Evaluation of the wear resistance and strength of the ice hockey shoes blades and the sticks

The effect of silica/polyurethane waterborne dispersion on the perforating features of impregnated polypropylene-based fabric

In an attempt to improve the puncturing behavior of a commercial technical textile, this study investigated the effects of fabric impregnation with waterborne polyurethane dispersions (WPUDs). The infusing solutions were prepared by mixing a commercially available WPUD with other components, such as water, hydrophilic and hydrophobic silica (SiO2) nanoparticles, and a crosslinker. Quasi-static perforation tests were performed on a dynamometer machine equipped with a spherical spike and pointed blade as piercing probes. The results showed that the polyurethane impregnation augmented the puncture performances of the treated textiles. Then, further improvements in the spike and blade strength of the impregnated fabrics were obtained by adding hydrophilic silica nanoparticles and crosslinker into WPUDs, respectively. No effect of silica functionalization (hydrophilic or hydrophobic) has been verified on the mechanical features of the respective treated samples for the tested filler contents of 3% and 5% in wt. The best fabric features (blade strength increase of +63% and puncture strength increase of +71% compared to the neat material) were obtained by combining the two additives, nano SiO2 and crosslinker, into the polyurethane. The performances of these last systems were also superior to those obtained by doubling the amount of polymeric dispersion applied to the neat materials. The discussion of the results was supported by electron scanning microscopy, infrared spectroscopy, and further measurements of the cutting resistance. Finally, the mass per unit area of the substrate for the impregnated samples was measured in order to assess weight gain due to treatment.

Effect of Stiffener Size on Ultimate Strength of GFRP Blade Stiffened Composite Plates

The ultimate strength of blade stiffened composite plates with various sizes of the stiffener is studied numerically using ANSYS software. The GFRP stiffened composite plates were modeled in ANSYS as SHELL elements with orthotropic properties. The finite element model of the GFRP stiffened composite plates was analysed to obtain deflection, axial deformation and stress contours and the ultimate load values. The obtained results of the finite element model were validated with that of available experimental data. The validated finite element model was used to study the effect of stiffener size. The stiffener size was varied from 10mm to 100mm. It was observed that smaller size of stiffeners were ineffective in stiffening the plate. The optimum size of stiffener was found to be 50mm to 75 mm. .

Design of Gas Pressure Insurance for a Rocket Bomb Fuze

The insurance mechanism has an important significance for the safety of the fuze design, and the choice of environmental forces is a difficult point to non-rotating or low-rotating rocket bomb fuze. By studying the characteristics of rocket launching process and using gas pressure of rocket launch, this paper has designed a gas pressure insurance mechanism for fuze, then we use fluent fluid simulation software and SolidWorks Simulation module to calculate the force of push rod and the strength of shear blade. The results show that the design of gas pressure insurance mechanism is reasonable.

Design and optimization of novel dehumidification strategies based on modified nucleation model in three-dimensional cascade

To decrease the wetness loss and increase the efficiency in nuclear plant steam turbine, several novel dehumidification strategies are presented in this paper and the dehumidification effect is tested. The modified nucleation model is built firstly, and the accuracy of the modified nucleation model combined with several droplet growth models is investigated and discussed. Secondly, the non-equilibrium condensation (NQC) characteristics in Dykas cascade are studied, the relationship among the parameters is obtained. Secondly, five novel dehumidification strategies are presented, and the dehumidification effect is evaluated. With the passage layer increasing, the ability of the wetness loss reduction is gradually enhanced. When the passage layer increases to 5, the wetness loss is reduced to 1.15 kJ/kg, but which is at the cost of reducing the blade strength. And the LNB_LNE_LWC is the best choice by balancing the dehumidification effect and the blade strength, succeeding in reducing the wetness loss to 1.42 kJ/kg. At last, the NQC characteristics in three-dimensional cascade are investigated numerically, the structure dehumidification effect with different passage layers is evaluated in detail. The results in this paper can give a scientific basis and reference for the design and optimization of the dehumidification strategy in nuclear plant steam turbine.

Structural collapse characteristics of a 48.8 m wind turbine blade under ultimate bending loading

To further study the structural failure mechanism and response characteristics of large wind turbine blades under extreme conditions, a full-scale 48.8 m blade collapse test was carried out. The strong coupling action of different damage modes are descripted by the gradual collapse process recorded by cameras. The damage behavior of suction side and pressure side, and interior and skin behavior of test blade are analysed. The test shows that the buckling of the suction side spar cap at about 21 m and cracks of the root shear web are the essential factor leading to the catastrophic failure of the entire blade, the test result is consistent with the finite element analysis. The load-deformation curve of the suction side spar cap, the deflection curves at 24 m, 36 m and tip, and the strains curves along the blade span are plotted to perform the data analysis. The critical load of 78% and deflection behavior in collapse process are determined by data analysis. The research results have great significance for improving the ultimate strength of entire blade, and provide a theoretical basis for the structural improvement of the weak points of blade.

Design of Composite Gyrocopter Main Rotor Blade Involving Rib and Spar Elements

Abstract Gyrocopter or gyroplane is a type of rotorcraft that uses an unpowered main rotor in free autorotation to develop lift. Gyrocopter rotor blades have smaller cord length and longer span compared to helicopters blades. National Advisory Committee for Aeronautics (NACA) 8-H-12 gyrocopter rotor blade profile, unsymmetrical airfoil sections were used for this research. An attempt has been made in this work to investigate the effect of ribs and spar elements in response to applied load. Three possible modeling alternatives were studied to predict the actual induced stress and deformation of the blade: Model I is by considering the blade shell part only, Model II is blade shell with 25 numbers of ribs and without the spar element and Model III is blade shell with 25 numbers of ribs and with spar element. The rotor blade was sized based on single seat open frame and high-wind-start gyrocopter. Structural static analysis has been carried out to evaluate the strength of composite rotor blade using ANSYS Workbench 15. The results show that among these three proposed models; Model III had registered minimum Von Mises stress and deformation. Also the result reveals that by considering ribs and spar element during analysis of gyrocopter blade is crucial because, it will help to know the actual induced stress and deformation. The predicted value of induced stress and deformation is closer to the actual values will help the designer not to overdesign the parts. Consequently, the main drawbacks related to overdesign increase in weight and cost will be minimized; thereby the product operational efficiency will be improved.

Ocena niezawodności wytrzymałości zmęczeniowej łopatek turbowentylatora rozproszoną metodą powierzchni odpowiedzi z wykorzystaniem krigingu

Fatigue crack propagation affects the operational reliability of engine turbo-fan blades. In this article, we integrate a Kriging regression model and a distributed collaborative response surface method (DCRSM) for the reliability assessment of turbo-fan blades, considering the relevant uncertainty. Following a series of deterministic analyses, such as steady-state aerodynamic analysis, harmonic response analysis and Campbell diagram, and based on the assumption that vibration stress is mainly from aerodynamic load, the fatigue strength is calculated for turbo-fan blades under coupling aerodynamic forces, according to a modified Goodman curve of titanium-alloy. Giving consideration to the uncertainty of the resonance frequencies and material properties, the fatigue strength of the turbo-fan blade is evaluated, including probabilistic analysis and sensitivity analysis. In the case study analyzed, the conclusions are that the fatigue strength reliability reaches 96.808% with confidence level of 0.95 for the turbo-fan blade under the coupling aerodynamic forces, and the first three-order resonant frequencies are found to have important influence on the fatigue performance of turbo-fan blades.