Steam Turbine Blades Research Articles

Blade profile extraction and edge completion method based on structured light measurement point cloud

Blade characteristic parameters evaluation plays an important role in quality monitoring and processing. In this research, a new blade profile extraction and edge completion strategy is proposed to deal with structured light measurement steam turbine blade. To handle the point cloud discretization and local data missing, the blade cross-sectional profiles are extracted adaptively at different heights, providing accurate and non-redundant data. Using NURBS and circular curves, the missing edge completion combines actual measurement curve trends and blade design geometric constraints, achieving a higher success rate and accuracy. Compared with the Perproj method and Virtual Edge method, the profile extraction accuracy of the proposed method is improved by 65 % and 36 % respectively, and the whole process of a sampled blade with additional noise is simulated to verify the effectiveness. Finally, more than two hundred blades are verified on the structured light measurement system, and the average absolute error of all parameters is less than 0.120 mm, which meets the accuracy requirements of blade quality evaluation in engineering applications.

Optimization of operating conditions in the steam turbine blade cascade using the black-box method

Water droplets cause corrosion and erosion, condensation loss, and thermal efficiency reduction in low-pressure steam turbines. In this study, multi-objective optimization was carried out using the black-box method through the automatic linking of a genetic algorithm (GA) and a computational fluid dynamics (CFD) code to find the optimal values of two design variables (inlet stagnation temperature and cascade pressure ratio) to reduce wetness in the last stages of turbines. The wet steam flow numerical model was used to calculate the optimization parameters, including wetness fraction rate, mean droplet radius, erosion rate, condensation loss rate, kinetic energy rate, and mass flow rate. Examining the validation results showed a good agreement between the experimental data and the numerical outcomes. According to the optimization results, the inlet stagnation temperature and the cascade pressure ratio were proposed to be 388.67 (K) and 0.55 (−), respectively. In particular, the suggested optimal temperature and pressure ratio improved the liquid mass fraction and mean droplet radius by about 32% and 29%, respectively. Also, in the identified optimal operating state, the ratios of erosion, condensation loss, and kinetic energy fell by 76%, 32.7%, and 15.85%, respectively, while the mass flow rate ratio rose by 0.68%.

3D printing large metal steam turbine blades

ORNL researchers use wire arc additive manufacturing to produce large rotating components for the first time.

Reconditioning repair of steam turbine blades using additive technology

Reconditioning repair of steam turbine blades using additive technology

Enhancing low-pressure stage steam turbine using the TDLD criterion and the TOPSIS analysis

The liquid phase in the wet steam flow causes thermodynamics losses and affects steam turbine blade durability. The main objective of the present research is the design of the rotor stagger angle and different operating conditions in the low-pressure stage of the steam turbine. A two-phase Eulerian-Eulerian model and the SST k − ω model are used to simulate the viscous wet steam flow inside the steam turbine stage. Frozen rotor methodology is employed for modeling the stator-rotor interaction. The effects of different rotor stagger angles and different outlet pressure levels on the wet steam flow parameters are studied to introduce an improved case. The turbine stage efficiency, droplet average radius, liquid mass fraction, and degree of reaction (TDLD) are considered as design criteria. The search for the improved value of pressure ratio and rotor stagger angle is performed using the TDLD criterion by TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). The improved case is selected with a rotor stagger angle of 64 degrees and outlet pressure of 6.5 kPa, at which the turbine stage efficiency (TSE) is increased by 21.3% compared to [Formula: see text]. Also, the liquid mass fraction (LMF) and the degree of reaction (DOR) reduced by 39.53 and 26% relative to [Formula: see text], and [Formula: see text], respectively. In addition, droplet average radius (DAR) increases by 26.14% compared to [Formula: see text].

SEARCH ALGORITHM UNDER THE CONDITIONS OF SERIAL PRODUCTION OF STRUCTURE OPTIONS OF THE TECHNOLOGICAL PROCESS OF MACHINING ON A GIVEN SET OF TECHNOLOGICAL EQUIPMENT

The article describes the algorithm for the formation of a set of options for the structures of technological processes (TP) of metal cutting on a given set of technological equipment and the sequence of operations in mass production. Variants of technological processes are presented in the form of a graph-tree, taking into account the sequence of operations and the possibility of using the main technological equipment for this. The algorithm for generating TP options is designed to form the most rational combination of the sequence of technological operations and the equipment on which they are implemented in the system of simulation of the production process. As a criterion for selecting TP options, the total time for their implementation was used. The algorithm is built into the software of the simulation system for production systems "GPS". It is implemented in the environment of the Mathcad 15 package, and as an example of calculations, the formation of the organizational and technological structure of the section for machining turbine blades of steam turbines in PJSC "TURBOATOM" is presented.

Fatigue life prediction of mistuned steam turbine blades subjected to deviations in blade geometry

The blades of the steam turbine are subjected to bending of the steam flow, centrifugal loading, vibration response, and structural mistuning. These factors mentioned contribute significantly to the fatigue failure of steam turbine blades. Low pressure (LP) steam turbines experience premature blade and disk failures due to the stress concentrations in the root location of the blade of its bladed disk. This study of mistuned steam turbine blades subjected to variation in blade geometry will be of great significance to the electricity generation industry. A simplified, mistuned, scaled-down steam turbine bladed disk model was developed using ABAQUS finite element analysis (FEA) software. The acquisition of the vibration characteristics and steady-state stress response of the disk models was carried out through FEA. Such studies are very limited. Subsequently, numerical stress distributions were acquired and the model was subsequently exported to Fe-Safe software for fatigue life calculations based on centrifugal and harmonic sinusoidal pressure loading. Vibration characteristics and response of the variation of the geometric blade of the steam turbine were investigated. Natural FEA frequencies compared well with the published literature of real steam turbines, indicating the reliability of the developed FEA model. The study found that fatigue life is most sensitive to changes in blade length, followed by width and then thickness, in this order. Analytical life cycles and Fe-Safe software show a percentage difference of less than 4.86%. This concludes that the numerical methodology developed can be used for real-life mistuned steam turbine blades subjected to variations in blade geometry.

Validation of the impedance spectroscopy method (MSID2/3) for NDT and SHM research in the power industry

The article presents a method for diagnosing steel blades of a high pressure steam turbine by analyzing the frequency of the electrical and magnetic parameters of the material during its operation. The methodology is historically derived from the analysis of normalized impedance components for defect detection and material selection. It was developed by and his research team. The extended possibilities of diagnostic tests of Multipoint Impedance Spectroscopy (SID2/3) are described, including material degradation processes and not only con tinuity defects. The test results were compared with structural studies, scanning electron microscopy (SEM) and energy dispersive X ray spectrometry (EDS) and wavelength dispersive (WDS). Impedance spectroscopy takes a significant place in diagnostic tests (NDT and SHM) in domestic literature and, thanks to the author, also in foreign literature. The topic was also presented at the World NDT Congress in Munich in 2018 [23]. Articles on this topic can be found on the NDT.net website [24]. Impedance spectroscopy is the subjec t of two doctoral theses and the promotion of Doctors of Technical Sciences [27, 28]. The thematic area covered by this article is mainly aimed at comparing the results with several selected methods.

Numerical analysis of non-Fourier heat conduction dynamics in the composite layer

This paper presents the numerical analysis of non-Fourier heat conduction in thin composite layers under asymmetrical boundary conditions. In the thermal barriers such as steam and gas turbine blades, thin film coating are used to protect the blade from thermal damage. The coating on the blades are very short in length. Heat conduction across thin composite layer with short time is examined using a finite element approach. With this very small duration with the finite speed of the thermal wave, the Fourier mode of heat conduction is disappeared due to the infinite speed of the thermal wave assumption. Therefore, analyzing the non-Fourier heat conduction in thin layers is essential. The developed model is executed in Python using Newmark's scheme and the constant average acceleration method to predict the temperature variation and temperature contours. The present model is validated with an experimental and numerical solution with good agreement. Besides, the temperature distribution across the composite layer with the entire length of the substrate and the coating for different thermal conductivity values, thermal diffusivity, and relaxation time are examined. It is noted that when the dimensionless

Monitoring of numerical simulation of the process of surface hardening treatment of titanium alloys

The paper presents the results of monitoring numerical simulation of the process of surface hardening of titanium alloys VT20 and OT4 by electric spark alloying, which can be used in the design of technological processes for the manufacture of titanium blades of steam turbines. Visualization of the resulting model, carried out using the MatLab computer program, gives a visual representation of the process under study. A good agreement of experimental and calculated (simulated) data allows you to set the parameters of the technological processes of hardening of turbine blades according to the simulation data.

SEM and EDX analysis of erosion products formed on steam turbine blade

ABSTRACT Water droplet erosion (WDE), which is brought on by the high-energy impact of liquid water droplets, is a serious problem for steam turbine blades. Nevertheless, rather than addressing the WDE of actual steam turbine blades, the majority of the published research on this issue uses laboratory test rigs. In this study, scanning electron microscopy and energy-dispersive X-ray analysis are used to examine how the surface of low-pressure steam turbine blades that had been in service eroded over time. The results of this study provide valuable insights into the microstructural features and elemental composition of X20Cr13 steel in steam turbine blades, as well as the factors that can contribute to damage and failure.

Reducing the condensing flow effects on the steam turbine blades through modified design geometry

Nowadays, a large part of energy is provided by steam turbines; thus, increasing the efficiency and improving the steam turbines performance are of special importance. The presence of the liquid phase in the low-pressure stage of the steam turbine can cause energy loss, efficiency drop, and erosion/corrosion problems; therefore, one of the essential issues is to identify wet steam flow and try to reduce condensation loss. In order to decrease the liquid fraction, the drainage groove technique can be applied. The drainage groove sucks the water droplets from the turbine blade surface and drains them into the condenser. In this study, the effect of the drainage groove location on the surface of steam turbine blades has been investigated on the condensation, droplet radius, inlet mass flow, erosion rate, liquid drainage ratio, condensation losses, and total drainage ratio. For modeling the condensing flow, the Eulerian–Eulerian approach has been applied. The results show that the location of the drainage groove affects the groove performance and flow pattern in the turbine blade. In the selected drainage, the liquid drainage ratio, condensation losses, and erosion rate are reduced by 7.6%, 12%, and 88%, respectively, compared with the no-drainage groove case. Also, the total drainage ratio is 7.2% in the selected drainage. The outcomes of the present work have been a major step forward in the techniques having a great influence on the lifetime, repair and maintenance, and the output power of steam power generation facilities.

Effect of Laser Shock Peening on the Fatigue Life of 1Cr12Ni3Mo2VN Steel for Steam Turbine Blades

In the present study, laser shock peening (LSP) was employed to enhance the rotating bending fatigue life of 1Cr12Ni3Mo2VN martensitic stainless steel used in steam turbine blades, addressing the issue of insufficient fatigue performance in these components. The aim of this study was to investigate the effect of LSP on the microhardness, residual stress, and rotating bending fatigue life of 1Cr12Ni3Mo2VN steel samples. The microhardness of LSP-treated samples was increased by 10.5% (LSP-3J sample) and 15.3% (LSP-4J sample), respectively, compared to high-frequency hardening samples. The residual compressive stress of the LSP-4J sample was the largest, reaching −689 MPa, and the affected layer depth was about 800 μm. Fatigue tests showed that the number of cycles at the fracture point for the LSP-3J and LSP-4J samples increased by 163% and 233%, respectively. The fatigue fracture morphology of the four samples showed that the microhardness and residual compressive stress distribution introduced by LSP could effectively inhibit the initiation of surface cracks, slow down the crack growth rate, and improve the rotating bending fatigue life of 1Cr12Ni3Mo2VN.

Corrosion reduction in steam turbine blades using nano-composite coating

The current study aims to reduce the hot corrosion issues in steam turbines for Al-Mussaib thermal power stations. To gain the aim of the study, many experimental tests were conducted by taking a sample from an existing broken steam turbine blade to identify the alloy composition and preparing samples with exact composition by powder metallurgy method, then using the electro-deposition method to coat the prepared samples by three different coating composite materials consists of TiO2 in different ratios (5, 10 and 15) g/l and 5 g/l SiO2 added to Watt's solution. To verify the efficiency of coating, several tests were conducted (surface roughness, hardness, wear, and oxidation test). The obtained results indicated that increasing the Ni-5%SiO2-TiO2 (5, 10 and 15) g/l caused an increase in the coating thickness, which is compatible with increasing the surface roughness. Also, the sample hardness increased after coating, which returned to increasing TiO2 amount (5, 10 and 15) g/l. However, wear resistance for the samples after coating by selected coating composite and 10 g/l TiO2 amount records the highest reduction in the wear of the sample.

Prediction of fatigue life of mistuned steam turbine blades subjected to variations in blade geometry

There is a large number of power stations suffering from fatigue failures of the steam turbine blades. The steam turbine blades are also subjected to steam flow bending, centrifugal loading, vibration response, and structural mistuning. These mentioned factors significantly contribute to the fatigue failure of the steam turbine blades. Low-Pressure (LP) steam turbines experience premature blade and disk failures due to the stress concentrations at the blade root area of its bladed disk. Driven by the problems encountered by the steam power plant electricity generating utilities with regards to steam turbine blades fatigue failure, this study of the mistuned steam turbine blades subjected to variation in blade geometry will be of great significance to the electricity generation industry. A simplified, scaled-down mistuned steam turbine bladed disk model was developed using ABAQUS finite element analysis (FEA) software. Acquisition of the vibration characteristics and steady-state stress response of the disk models was performed through FEA. Thereafter, numerical stress distributions were acquired, and the model was subsequently exported to Fe-Safe software for fatigue life calculations based on centrifugal and harmonic sinusoidal pressure loading. The vibration characteristics and the response of the variation steam turbine geometric blade was conducted. The FEA natural frequencies compared well with published literature of the real steam turbines indicating reliability of the developed FEA model. The study found that the fatigue life is most sensitive to changes in blade length, followed by the width, and then the thickness, in this order. The analytical life cycles and Fe-Safe software shows the percentage difference of less than 4.86%. This concludes that the developed numerical methodology can be used for real-life mistuned steam turbine blades subjected to variations in blade geometry.

Optimization of inlet conditions of hot steam injection into the non-equilibrium condensing steam

Injecting hot steam into the cascade flow is one of the procedures for resisting losses and damages caused by condensation. In the current study, utilizing a 3D (three-dimensional) geometry for steam turbine blades, the hot steam has been injected into the steam cascade via the embedded channel. In the power plant industry, the hot steam injection process is done in two ways: constant pressure with a reservoir or constant mass flow rate utilizing a control valve. Therefore, considering these two methods and the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) optimization method, the best temperature for injecting hot steam into non-equilibrium steam in a constant steam turbine blade has been gained. At the optimal temperature of 540 K at the constant pressure mode, Er (erosion rate ratio) and Lr (condensation loss ratio) were obtained as 66.6% and 30.7%, respectively, and Kr (kinetic energy ratio) showed a 0.6% growth in the hot steam injection mode, in comparison with the original mode. In addition, the economic cost of hot steam injection was calculated as 0.457 ($/hour). By the TOPSIS optimization method, the optimal temperature of hot steam injection, utilizing the constant mass flow rate method, has been obtained as 460 K, and the Er, Lr, and Kr values were 31.2%, 66.1%, and 88.48%, respectively at the optimal temperature. Moreover, the economic cost was 0.43 ($/hour). It is easier to control the steam injection by the constant mass flow rate method utilizing a control valve; therefore, the 460 K temperature and constant mass flow rate method are introduced as the optimal method.

Failure investigations of last stage low-pressure steam turbine blade

Failure investigations of last stage low-pressure steam turbine blade

Failure Analysis of High-Pressure Turbine Blades in Steam Power Plants

This paper describes the failure of high-pressure steam turbine blades. During the Serious Inspection, it was discovered that the ninth-stage high-pressure turbine blade had failed. The causes of blade failure are examined via visual inspection and destructive testing. The failure mechanism of the blades was determined by conducting mechanical properties testing, metallographic inspection, and energy spectrum analysis. The mechanical properties of the leaf and root blade specimens were within the range of blade steel for steam turbines according to the Chinese National Standard (GB/T 8732-2004), but the chemical composition was not identical. This is consistent with the root blade fracture pattern where the hardness value plotted from the test results is the lowest at the root blade location, which is the primary cause of fissure propagation.

Study on Fracture Mechanism of Low-Pressure Blades of Steam Turbines in Power Plants

With the continuous improvement of steam turbine design technology and production level, steam turbine blade fracture accidents have dropped significantly, and blade fracture accidents are no longer the main reason for the forced shutdown of thermal power generation units. Due to the bad working conditions of turbine blades, blade designers still need help to accurately analyze their dynamic stress and evaluate their high cycle fatigue life. Up to now, blade fracture accidents still occur frequently. In this paper, a comprehensive analysis is made of the causes of the fracture of the low-pressure 16th stage blade of a 25 MW steam turbine in a thermal power plant. The fracture property of turbine moving blades is that small corrosion pits are formed first, and then the fatigue propagation fracture occurs. The main cause of corrosion is poor steam quality.

Analysis of degradation and damage processes of power components of steam turbines

The article is a review of the literature data related to the wear of steam turbine blades. The literature review have found that the main causes of blade damage are erosion, corrosion, and the occurrence of elevated temperatures inside the turbine, which cause, among other things, blade elongation, deformation, and cracks due to rapid temperature changes (thermal shock). A review of the literature has shown that blades are a subject to erosion resulting from operating conditions in which the blades strike water droplets formed from steam or from the injection of cooling condensate in the zone of the last stage of the low-pressure part of the turbine. Erosion occurs mainly at the inlet and outlet edges of the blades, causing imbalance (different blade wear in one rotor stage) in addition to reducing turbine efficiency. Erosion can also cause an increase in stresses that can lead to serious damage not only to the blades, but also to other turbine components. Steam turbine blades are also exposed to aggressive working environment (chlorides, sulfates, and alkali metal silicates from steam) as a result of which uniform and also pitting corrosion can occur on the blades. The article also analyses the effect of operating conditions on the damage that occurs, as well as the literature on predicting turbine blade life.Keywords: steam turbines, erosion, corrosion, wear, blade, surface top layer