Turbine Operating Conditions Research Articles

Prediction of hydroelectric turbine runner strain signal via cyclostationary decomposition and kriging interpolation

Strain measurements by gauges can play an important role in analyzing the fatigue damage of the hydroelectric turbine runner. However, these measurements cannot cover every steady-state operating condition due to the experimental limitations. Thus, the aim of this research is to predict the strain signal on runner over every possible steady operating condition using available experimental measurements. The strain signal measured during steady state involves several components (such as periodicity, vortex rope component and stochastic components) which can generate difficulties during the prediction. This paper proposes a solution to predict the runner strain signals by independently interpolating each physical phenomenon over different turbine operating conditions. These components are extracted using cyclostationary decomposition operators. A case study is performed on a Francis hydroelectric turbine to verify the interpolation performance. The proposed methodology can contribute to the fatigue assessment and help to reduce the requirements of infield measurements.

Health Monitoring and Diagnosis System for a Small H-Type Darrieus Vertical-Axis Wind Turbine

As the wind power market grows rapidly, the importance of technology for real-time monitoring and diagnosis of wind turbines is increasing. However, most of the developed technologies and research mainly focus on large horizontal-axis wind turbines, and research conducted on small- and medium-sized wind turbines is rare. In this study, a novel low-cost and real-time health monitoring and diagnosis system for the small H-type Darrieus vertical axis wind turbine is proposed. Turbine operating conditions were classified into parked/idle and power production. In the case of the power production condition, abnormality diagnosis was performed using key monitoring parameters, including vibration, fundamental frequency, the bending stress of the tower and generator vibration. The turbine abnormalities were diagnosed in two stages by applying the alert and alarm limits, determined by referring to international standards and material properties and the long-term measurement data together.

Comparative analysis and forecasting of isentropic efficiency of gas turbine compressor with ARIMA, VAR, NARNN and ANFIS approaches

It is extremely important to monitor the status of gas turbine to ensure its safe and reliable operation. In this work, the variation trend of isentropic efficiency of compressor is analysed based on the measured data of F-class heavy-duty gas turbine in practical industrial application. The actual measured data of F-class heavy-duty gas turbine includes the data under start-stop and unstable working conditions, which cannot be directly used for calculation and analysis. To solve this problem, the data selection rules are designed and determined according to the operating conditions of gas turbine to select the data under effective working state. The isentropic efficiency of compressor is calculated based on the selected data. Then the forecasting effects of four forecasting methods on the variation trend of isentropic efficiency of compressor are studied. Four indexes, namely, symmetric mean absolute percentage error (SMAPE), mean absolute percentage error (MAPE), root mean square error (RMSE), and similarity (SIM) values are utilized to evaluate the forecasting accuracy. The research results indicate that the Adaptive Neuro-Fuzzy Inference System (ANFIS) method has better forecasting effect than Autoregressive Integrated Moving Average (ARIMA), Vector Autoregression (VAR) and Nonlinear Autoregression Neural Network (NARNN) for this F-class heavy-duty gas turbine. Through the ANFIS method, the SIM up to 96.77%, the SMAPE and MAPE are less than 0.1, and the RMSE is only 0.1157. Therefore, the ANFIS method is suitable for forecasting the isentropic efficiency of this F-class heavy-duty gas turbine compressor.

Comparison of Two Power Converter Topologies in Wind Turbine System

The article presents comprehensive results of research on two representative topologies of converters used in the path of processing energy generated in a wind turbine and transmitted to the grid. The topology T1 uses a two-level transistor-controlled rectifier as a converter from the generator side, while the T2 topology uses DC/DC boost converter. In both topologies, a three-level back-to-back converter with a line filter L was used as a grid converter. The conclusions indicate the tendency of changes in power losses depending on the aforementioned parameters and can be used at the stage of deciding on the choice of topology, operating parameters or selection of control methods depending on the specific operating conditions of the wind turbine.

A study of the dependence between fuel consumption of a heat gas turbine and variation of heat loading of regional consumers having various climatic conditions taking into account determination of structural characteristics of heat exchanging equipment for grid water heating

The aim was to optimize the dependence between fuel consumption and heat loading of regional consumers varied due to climatic conditions, taking into account the determination of structural characteristics of heat exchanging equipment for grid water heating in a heat gas turbine. A heat gas turbine comprising two fuel combustion chambers, a waste-heat boiler and a contact heat exchanger to heat makeup grid water was investigated. Scheme and parametric optimization studies were carried out using a mathematic model of a gas turbine created using a software and hardware system developed at the Department of Heat Power Systems of the Melentiev Energy Systems Institute, Siberian Branch of the Russian Academy of Sciences. Th turbine operating conditions differing in heat loads in four suggested operating regions were studied. It was found that an increase in fuel consumption in the second combustion chamber was 29%– 84% compared to that in the first combustion chamber. This rise was recorded when the turbine heat loading was increasing in the considered regions. Data analysis of the scheme and parametric optimization studies showed that, for operating conditions with a higher heat loading, it seems reasonable to ensure the maximum possible heating of makeup grid water as the loading rises. It is also recommended to slightly increase the heat surface area of the makeup grid water heater whose structural materials are less expensive than in a waste-heat boiler. It was shown that the suggested technical solution slightly increases specific capital investments while fully providing electrical and heat power to consumers. The obtained results can be used to select optimal technical solutions ensuring competitiveness in the operation of a heat gas turbine in regions with various climatic characteristics.

Frequency Scan–Based Mitigation Approach of Subsynchronous Control Interaction in Type-3 Wind Turbines

Integration of wind energy resources into the grid creates several challenges for power system dynamics. More specifically, Type-3 wind turbines are susceptible to subsynchronous control interactions (SSCIs) when they become radially connected to a series-compensated transmission line. SSCIs can cause disruptions in power generation and can result in significant damage to wind farm (WF) components and equipment. This paper proposes an approach to mitigate SSCIs using an online frequency scan, with optimized phase angles of voltage harmonic injection to maintain steady-state operation, to modify the controllers or the operating conditions of the wind turbine. The proposed strategy is simulated in PSCAD/EMTDC software on the IEEE second benchmark model for subsynchronous resonance. Simulation results demonstrate the effectiveness of this strategy by ensuring oscillations do not grow.

Enhancing Thermal Properties of Steam Turbine Blades by Coating with Nanomaterials

Heat resistant coatings are considered for the external surface Low-Pressure Steam Turbines (LPST). 410 stainless steel covered with nano heat resistant coatings consists of a heat resistant connecting layer enhanced by nanoparticles. A commercial paint was modified by using 20%wt of (titanium dioxide (TiO2) - aluminum oxide (Al2O3)) with different concentrations range (25,50,75wt% of TiO2) layers. These nano-coatings paints were airbrushed onto the surface of specimens of steam turbine blades. The test rig and experimental apparatus have been fabricated and collected to accomplish the thermal tests. The samples were subjected to heat resistance and a temperature test approximately similar to the steam turbine's operation condition temperature. The test results are used to choose the nano-coating layer with a concentration that ensures a composition's highest protective properties. The test sample with concentration (paint-(75% Al2O3+25% TiO2)) showed the highest thermal properties compares with the other cases.

Machine Learning-Based Tools for Wind Turbine Acoustic Monitoring

The identification and separation of sound sources has always been a difficult problem for acoustic technicians to tackle. This is due to the considerable complexity of a sound that is made up of many contributions at different frequencies. Each sound has a specific frequency spectrum, but when many sounds overlap it becomes difficult to discriminate between the different contributions. In this case, it can be extremely useful to have a tool that is capable of identifying the operating conditions of an acoustic source. In this study, measurements were made of the noise emitted by a wind turbine in the vicinity of a sensitive receptor. To identify the operating conditions of the wind turbine, average spectral levels in one-third octave bands were used. A model based on a support vector machine (SVM) was developed for the detection of the operating conditions of the wind turbine; then a model based on an artificial neural network was used to compare the performance of both models. The high precision returned by the simulation models supports the adoption of these tools as a support for the acoustic characterization of noise in environments close to wind turbines.

Experimental and numerical analysis of Pitting Corrosion in CUSTOM 450 Stainless Steel

The present study aimed at the propagation of the pit in CUSTOM 450 Stainless Steel blades after the initiation stage. The depth of pits was measured by Eddy Current and the relationship between pitting corrosion time and pit depth was determined based on simulation and compared to the experimental results. Moreover, the electrolyte potential and the local strain distribution around the pit were displayed at different potentials and times. The pit growth increased rapidly for a certain period and then declined. For stressed and stress-free samples, the local strain distribution and pit depth growth were compared at 350 mVSCE potential. Based on the results, the presence of stress in the specimens accelerated the pitting corrosion growth in CUSTOM 450 stainless steel. To calculate the stresses on the blade surface, the model of the blade was constructed and two adjacent pits were created at the location of the fractured surface. The results show that the pits are turned into stress cracks after about 4 months corresponding to the result of the other references. To make a connection between accelerated pitting corrosion tests and the operating conditions of the gas turbine, the comparison of pitting time (simulation) was made for the stressed sample at 350 mVSCE potential and sample with real operating conditions.350 mVSCE potential and sample with real operating conditions.

Prediction of power generation of two 30 kW Horizontal Axis Wind Turbines with Gaussian model

In order to improve the total efficiency of power generation in a wind farm, this paper investigated the effect of different operating conditions of the upstream wind turbine on the power of the downstream wind turbine by Gaussian wake model. A three-bladed Horizontal Axis Wind Turbine with the generator capacity of 30 kW was used. Firstly, Gaussian model for evaluating the wake flow was developed, which fit well with experiment data. Then, the influence of the operating condition of the upstream turbine on the downstream turbine performance was estimated by calculating the energy amount resulted from the velocity deficit of the wake. Finally, the effect of the installation position of the downstream wind turbine was analyzed. In consequence, the total power coefficient Ptotal of the wind turbines was relatively higher when the upstream turbine was at tip speed ratio λ = 6.4 and pitch angle β = 2° among different test conditions. Meanwhile, the Ptotal showed the maximum value when the downstream turbine was installed at the streamwise location x/D = 2.0 and lateral offset location y/R = 1.5 when the inflow turbulence intensity is 0.22≤TIref ≤ 0.35. This paper provided a better guidance for optimizing the wind turbine layout and improving the total power output of the entire wind farm.

Vibration monitoring of wind turbine tower based on XGBoost

A tower vibration monitoring method based on XGBoost is proposed to predict the tower vibration trends under different operating conditions. Firstly, the wind turbine operating conditions are classified based on the Kmeans clustering algorithm. Secondly, the impact of state parameters of the wind turbine on the tower vibration is analyzed, and the tower vibration monitoring model is established based on XGBoost algorithm. Finally, the actual SCADA data of the wind farm is used to verify the proposed method. The results show that the vibration monitoring accuracy of tower is effectively improved by considering the operating conditions of the wind turbine.

Test-Rig Simulation on Hybrid Thermal Barrier Coating Assisted with Cooling Air System for Advanced Gas Turbine under Prolonged Exposures—A Review

Thermal barrier coating (TBC) and cooling air systems are among the technologies that have been introduced and applied in pursuing the extensive development of advanced gas turbine. TBC is used to protect the gas turbine components from the higher operating temperature of advanced gas turbine, whereas cooling air systems are applied to assist TBC in lowering the temperature exposure of protected surfaces. Generally, a gas turbine operates in three main operational modes, which are base load, peak load, and part peak load. TBC performance under these three operational modes has become essential to be studied, as it will provide the gas turbine owners not only with the behaviors and damage mechanism of TBC but also a TBC life prediction in a particular operating condition. For TBC under base load or so called steady-state condition, a number of studies have been reviewed and discussed. However, it has been found that most of the studies have been conducted without the assistance of a cooling air system, which does not simulate the TBC in advanced gas turbine completely. From this review, the studies on TBC-assisted cooling air system to simulate the advanced gas turbine operating conditions have also been summarized, which are limited to test rig simulations under thermal cyclic mode where thermal cyclic represents peak and part peak load conditions. The equipment used to simulate the gas turbine operating condition, test temperatures, and durations are parameters that have been taken into consideration under this review. Finally, a test rig that is capable of simulating both TBC and cooling air effects at a high operating temperature of advanced gas turbines for prolonged exposure under steady-state condition has been proposed to be developed.

Special cases in fatigue analysis of wind turbines

The turbine industry demands a reliable design with affordable cost. As technological advances begin to support turbines of huge sizes, and the increasing importance of wind turbines from day to day make design safety conditions more important. Wind turbines are exposed to environmental conditions that can affect their installation, durability, and operation. International Electrotechnical Commission (IEC) 61400-1 design load cases consist of analyses involving wind turbine operating conditions. This design load cases (DLC) is important for determining fatigue loads (i.e., forces and moments) that occur as a result of expected conditions throughout the life of the machine. With the help of FAST (Fatigue, Aerodynamics, Structures, and Turbulence), an open source software, the NREL 5MW land base wind turbine model was used. IEC 61400-1 wind turbine design standard procedures assessed turbine behavior and fatigue damage to the tower base of dynamic loads in different design conditions. Real characteristic wind speed distribution and multi-directional effect specific to the site were taken into consideration. The effect of these conditions on the economic service life of the turbine has been studied.

Experimental Study of Transient Flow Regimes in a Model Hydroturbine Draft Tube

Swirling flow with the formation of a precessing vortex core (PVC) in the draft tube model of a hydroturbine was studied. Experiments were performed on an aerodynamic setup under transient operating conditions of the hydroturbine. The turbine operating conditions were varied by continuously changing the flow rate at a constant runner speed. The transition from the partial load regime, when a precessing vortex core is formed, to the best efficiency point without a core is considered. Applied to this task, a comparison of the windowed Fourier transform with wavelet analysis is given. The dependence of the PVC lifetime in the transient regime correlates with the transient time. It is shown that the velocity profiles and the spectrum of pressure pulsations in transient regimes change quasistatically between part-load operation and the best efficiency point of the turbine. The phase-averaged velocity distributions in the transient regimes show that a transient regime is a sequence of quasisteady regimes.

Hydrodynamics and wake flow analysis of a Π-type vertical axis twin-rotor tidal current turbine in surge motion

For a floating tidal current turbine power station, the motion response of the floating carrier would affect the hydrodynamic performance of the tidal current turbine. To study the turbine loads and power output characteristics of the proposed twin-rotor turbine in moving condition, the hydrodynamic performance of a vertical axis twin-rotor turbine in surge motion is thoroughly discussed in this manuscript. Based on the moving mesh and sliding mesh technique, the rotary motion and surge motion of the turbine are combined to simulate the turbine operation conditions in waves and currents. The twin-rotor turbine working at different surge frequencies, surge amplitudes, and tip speed ratios is simulated and the simulation results are compared with the fixed turbine in an uniform flow. The change characteristics of thrust force, lateral force, and flow field are analyzed. The results show that the twin-rotor can improve the power output efficiency better than a stand-alone turbine. Surge frequency and surge amplitude have very little influence on the average power output of the turbine. The fluctuation amplitude of the thrust and lateral forces of a twin-rotor turbine is larger than the stand-alone turbine, while the fluctuation amplitude of thrust and lateral forces increase with surge amplitude and frequency. Spectra of turbine loads and power output show that surge and rotation frequencies have different impacts on the dynamics and performances of the turbine. The research results can provide a reference for the development of floating tidal current power stations in the future.

Wake and Performance Predictions of Two- and Three-Bladed Wind Turbines Based on the Actuator Line Model1

Abstract This paper challenges the standard wind turbine design numerically assessing the wake and aerodynamic performance of two- and three-bladed wind turbine models implementing downwind and upwind rotor configurations, respectively. The simulations are conducted using the actuator line model (ALM) coupled with a three-dimensional Navier Stokes solver implementing the k−ω shear stress transport turbulence model. The sensitivity of the ALM to multiple simulation parameters is analyzed in detail and numerical results are compared against experimental data. These analyses highlight the most suitable Gaussian radius at the rotor to be equal to twice the chord length at 95% of the blade for a tip-speed ratio (TSR) of ten, while the Gaussian radius at the tower and the number of actuator points have a low incidence on the flow field computations overall. The numerical axial velocity profiles show better agreement upstream than downstream the rotor, while the discrepancies are not consistent through all the assessed operating conditions, thus highlighting that the ALM parameters are also dependent on the wind turbine's operating conditions rather than being merely geometric parameters. Particularly, for the upwind three-bladed wind turbine model, the accuracy of the total thrust computations improves as the TSR increases, while the least accurate wake predictions are found for its design TSR. Finally, when comparing both turbine models, an accurate representation of the downwind configuration is observed as well as realistic power extraction estimates. Indeed, the results confirm that rotors with fewer blades are more suitable to operate at high TSRs.

On the Evaluation of Mesh Resolution for Large-Eddy Simulation of Internal Flows Using Openfoam

The central aim of this paper is to use OpenFOAM for the assessment of mesh resolution requirements for large-eddy simulation (LES) of flows similar to the ones which occur inside the draft-tube of hydraulic turbines at off-design operating conditions. The importance of this study is related to the fact that hydraulic turbines often need to be operated over an extended range of operating conditions, which makes the investigation of fluctuating stresses crucial. Scale-resolving simulation (SRS) approaches, such as LES and detached-eddy simulation (DES), have received more interests in the recent decade for understanding and mitigating unsteady operational behavior of hydro turbines. This interest is due to their ability to resolve a larger part of turbulent flows. However, verification studies in LES are very challenging, since errors in numerical discretization, but also subgrid-scale (SGS) models, are both influenced by grid resolution. A comprehensive examination of the literature shows that SRS for different operating conditions of hydraulic turbines is still quite limited and that there is no consensus on mesh resolution requirement for SRS studies. Therefore, the goal of this research is to develop a reliable framework for the validation and verification of SRS, especially LES, so that it can be applied for the investigation of flow phenomena inside hydraulic turbine draft-tube and runner at their off-design operating conditions. Two academic test cases are considered in this research, a turbulent channel flow and a case of sudden expansion. The sudden expansion test case resembles the flow inside the draft-tube of hydraulic turbines at part load. In this study, we concentrate on these academic test cases, but it is expected that hydraulic turbine flow simulations will eventually benefit from the results of the current research. The results show that two-point autocorrelation is more sensitive to mesh resolution than energy spectra. In addition, for the case of sudden expansion, the mesh resolution has a tremendous effect on the results, and, so far, we have not capture an asymptotic converging behavior in the results of Root Mean Square (RMS) of velocity fluctuations and two-point autocorrelation. This case, which represents complex flow behavior, needs further mesh resolution studies.

Modeling and Analysis of a Micro Gas Turbine Fuelled with Hydrogen and Natural Gas Blends

This study deals with implementing an analytical model to simulate the energy performance associated with a Micro Gas Turbine when H2NG (Hydrogen Enriched Natural Gas) blends are used as fuel. The experimental campaign validated the simulation results at the actual operating conditions of the Micro Gas Turbine. The experimental campaign for model validation has been carried out over the spring and summer periods. Additionally, the MGT performance has been detected when fuelled H2NG with hydrogen fraction ranges between 0% vol. to 10% vol., with a 2% vol. Step., according to the main findings, the fuel consumption is reduced significantly. Also, heat recovery and electrical reliability improve slightly even though environmental factors influence the system. A numerical model was developed with MATLAB-Simulink to model the operation of the MGT. Thus, the relative standard errors affecting the main output parameters have been determined.

Experimental research on flow field of high head pump turbine based on PIV test

Pump turbine operating conditions are complex, mainly covering turbine mode and pump mode. Pump turbines have various instability problems during operation, such as S-shaped, pump hump, pressure pulsation and cavitation. PIV (Particle Image Velocimetry) is a very effective test technique for the internal flow field observation of pump turbines. In this paper, the S-shaped, pump hump and pressure pulsation of the pump turbine are tested by PIV technology. The experimental observations show that the internal flow of the pump turbine is extremely complicated. For example, the full quadrant flow characteristics of the S-shaped working condition are observed. It is found that there is a phenomenon of single vortex and double vortex coexisting in the Vane-less area between guide vane and impeller blade of the pump turbine. Through the experimental research in this paper, it can provide useful help for understanding the vortex separation on different quadrant working conditions inside the pump turbine.

Faults Caused by Cavitation in Hydraulic Power Plants and Solution Methods

Hidrolik enerji, Dünya’ daki en zengin ve en kullanışlı yenilenebilir enerji kaynaklarından biridir. Bu nedenle enerjinin sürekli üretilebilmesi için hidrolik türbinler faydalı ömürlerini kısaltan ve yorgunluk hasarlarına neden olan başlatma ve durdurma gibi birden fazla geçici durumlara karşı optimum değerlerde en iyi verimlilik düzeyinde çalıştırılmalıdır. Optimal tasarım dışı kısmi yüklerde çalışan Francis türbinlerde akış düzensizliklerinden dolayı basınç değişimleri meydana gelir. Bu basınç değişimleri hidrolik, mekanik veya yapısal bir bileşenin doğal frekansı ile çakışması durumunda rezonans nedeniyle yüksek titreşimler oluşturarak türbinin dengesiz (balanslı) çalışmasına sebep olmaktadır. Bu çalışmada, Francis türbinin yüksek titreşimleri, türbin ayar kanadına montaj edilen kavitasyon sensörü aracılığıyla sürekli (online) titreşim izleme sistemi yardımıyla izlenerek dengesizlik durumunda çalışmasının kavitasyon titreşim etkileri ile dengesizlik giderildikten sonraki durumda kavitasyon titreşim etkileri incelenmiştir. Hidrolik türbinlerin farklı işletme şartlarında kavitasyon olayının sebep olduğu titreşim grafiksel olarak gösterilmiştir. Makalenin son kısmında verilen grafikte yatak arızası giderildikten sonra titreşim büyüklüğünün 2 mm s-1’den 0,5 mm s-1’ye düşürüldüğü görülmektedir. Bu durum hidrolik türbinlerin güvenli kavitasyon bölgesinde çalıştırılarak yüksek titreşim seviyelerinden kaçınmak için önemli bir sonuç oluşturmaktadır.