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17 pages, 1355 KiB

Open AccessArticle

Lubrication Analysis of a Mechanical Seal Considering the Mixed Lubricant State of Gas and Liquid During External Power Shutdown of a Reactor Cooling Pump

by Youngjun Park, Gwanghee Hong, Sanghyun Jun, Jeongmook Choi, Taegyu Kim, Minsoo Kang and Gunhee Jang

Lubricants 2024, 12(12), 406; https://doi.org/10.3390/lubricants12120406 - 21 Nov 2024

Abstract

We proposed a method to calculate the pressure, opening force, and leakage rate in a mechanical seal under the mixed lubricant state of a gas and liquid for the mechanical seal in a reactor cooling pump (RCP) during external power loss. We calculated [...] Read more.

We proposed a method to calculate the pressure, opening force, and leakage rate in a mechanical seal under the mixed lubricant state of a gas and liquid for the mechanical seal in a reactor cooling pump (RCP) during external power loss. We calculated the pressure by solving the nonlinear finite element equation composed of the linear Reynolds equation of an incompressible liquid lubricant and the nonlinear Reynolds equation of a compressible gas lubricant using the Newton–Raphson method. In addition, we calculated the temperature distribution by solving the two-dimensional energy equation utilizing the finite element method. Additionally, we included the turbulence effect in the incompressible liquid lubricant and the turbulence and slip effects in the compressible gas lubricant. The accuracy of the developed program was validated by comparing the simulated opening force and leakage rate of both the mechanical seal with the liquid lubricant and the mechanical seal with the gas lubricant with prior research. Our analysis shows that in high-temperature environments, the increase in the gas region at the lubrication surface leads to a decrease in pressure and opening force and an increase in the leakage rate. Conversely, as the outer pressure increases, the gas region decreases, resulting in an increase in pressure, opening force, and leakage rate. Full article

7 pages, 2589 KiB

Open AccessArticle

Electromagnetic Modeling of Superconducting Bulks in Applied Time-Varying Magnetic Field

by Hocine Menana

Condens. Matter 2024, 9(4), 47; https://doi.org/10.3390/condmat9040047 - 9 Nov 2024

Viewed by 323

Abstract

An integrodifferential model formulated in terms of the electric vector potential is developed for the 3D numerical modeling of the electromagnetic field in superconducting bulks, for AC losses evaluation. The Newton Raphson method is applied to accelerate the convergence. The model is validated [...] Read more.

An integrodifferential model formulated in terms of the electric vector potential is developed for the 3D numerical modeling of the electromagnetic field in superconducting bulks, for AC losses evaluation. The Newton Raphson method is applied to accelerate the convergence. The model is validated on a benchmark. The comparison results show the accuracy of the model and its performances in terms of computation time compared to classical approaches. Full article

(This article belongs to the Special Issue Selected Papers from the International Conference on Quantum Materials and Technologies (ICQMT2024))

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22 pages, 1273 KiB

Open AccessArticle

Estimation of Lifetime Performance Index for Generalized Inverse Lindley Distribution Under Adaptive Progressive Type-II Censored Lifetime Test

by Shixiao Xiao, Xue Hu and Haiping Ren

Axioms 2024, 13(10), 727; https://doi.org/10.3390/axioms13100727 - 18 Oct 2024

Viewed by 519

Abstract

The lifetime performance index (LPI) is an important metric for evaluating product quality, and research on the statistical inference of the LPI is of great significance. This paper discusses both the classical and Bayesian estimations of the LPI under an adaptive progressive type-II [...] Read more.

The lifetime performance index (LPI) is an important metric for evaluating product quality, and research on the statistical inference of the LPI is of great significance. This paper discusses both the classical and Bayesian estimations of the LPI under an adaptive progressive type-II censored lifetime test, assuming that the product’s lifetime follows a generalized inverse Lindley distribution. At first, the maximum likelihood estimator of the LPI is derived, and the Newton–Raphson iterative method is adopted to solve the numerical solution due to the log-likelihood equations having no analytical solutions. If the exact distribution of the LPI is not available, then the asymptotic confidence interval and bootstrap confidence interval of the LPI are constructed. For the Bayesian estimation, the Bayesian estimators of the LPI are derived under three different loss functions. Due to the complex multiple integrals involved in these estimators, the MCMC method is used to draw samples and further construct the HPD credible interval of the LPI. Finally, Monte Carlo simulations are used to observe the performance of these estimators in terms of the average bias and mean squared error, and two practical examples are used to illustrate the application of the proposed estimation method. Full article

(This article belongs to the Special Issue Reliability and Risk of Complex Systems: Modelling, Analysis and Optimization)

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18 pages, 2623 KiB

Open AccessArticle

Design and Applicability of Two-Step Fractional Newton–Raphson Method

by Naseem Zulfiqar Ali, Awais Gul Khan, Muhammad Uzair Awan, Loredana Ciurdariu and Kamel Brahim

Fractal Fract. 2024, 8(10), 582; https://doi.org/10.3390/fractalfract8100582 - 2 Oct 2024

Viewed by 798

Abstract

Developing two-step fractional numerical methods for finding the solution of nonlinear equations is the main objective of this research article. In addition, we present a detailed study of convergence analysis for the methods that have been proposed. By comparing numerically, we can see [...] Read more.

Developing two-step fractional numerical methods for finding the solution of nonlinear equations is the main objective of this research article. In addition, we present a detailed study of convergence analysis for the methods that have been proposed. By comparing numerically, we can see that the proposed methods significantly improve convergence rate and accuracy. Additionally, we demonstrate how our main results can be applied to basins of attraction. Full article

(This article belongs to the Special Issue Fractional Systems, Integrals and Derivatives: Theory and Application)

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19 pages, 15139 KiB

Open AccessArticle

Ultra-Short-Term Photovoltaic Power Prediction by NRGA-BiLSTM Considering Seasonality and Periodicity of Data

by Hong Wu, Haipeng Liu, Huaiping Jin and Yanping He

Energies 2024, 17(18), 4739; https://doi.org/10.3390/en17184739 - 23 Sep 2024

Cited by 1 | Viewed by 851

Abstract

Photovoltaic (PV) power generation is highly stochastic and intermittent, which poses a challenge to the planning and operation of existing power systems. To enhance the accuracy of PV power prediction and ensure the safe operation of the power system, a novel approach based [...] Read more.

Photovoltaic (PV) power generation is highly stochastic and intermittent, which poses a challenge to the planning and operation of existing power systems. To enhance the accuracy of PV power prediction and ensure the safe operation of the power system, a novel approach based on seasonal division and a periodic attention mechanism (PAM) for PV power prediction is proposed. First, the dataset is divided into three components of trend, period, and residual under fuzzy c-means clustering (FCM) and the seasonal decomposition (SD) method according to four seasons. Three independent bidirectional long short-term memory (BiLTSM) networks are constructed for these subsequences. Then, the network is optimized using the improved Newton–Raphson genetic algorithm (NRGA), and the innovative PAM is added to focus on the periodic characteristics of the data. Finally, the results of each component are summarized to obtain the final prediction results. A case study of the Australian DKASC Alice Spring PV power plant dataset demonstrates the performance of the proposed approach. Compared with other paper models, the MAE, RMSE, and MAPE performance evaluation indexes show that the proposed approach has excellent performance in predicting output power accuracy and stability. Full article

(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)

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28 pages, 563 KiB

Open AccessArticle

Exploring a Dynamic Homotopy Technique to Enhance the Convergence of Classical Power Flow Iterative Solvers in Ill-Conditioned Power System Models

by Alisson Lima-Silva and Francisco Damasceno Freitas

Energies 2024, 17(18), 4642; https://doi.org/10.3390/en17184642 - 17 Sep 2024

Viewed by 626

Abstract

This paper presents a dynamic homotopy technique that can be used to calculate a preliminary result for a power flow problem (PFP). This result can then be used as an initial estimate to efficiently solve the PFP using either the classical Newton-Raphson (NR) [...] Read more.

This paper presents a dynamic homotopy technique that can be used to calculate a preliminary result for a power flow problem (PFP). This result can then be used as an initial estimate to efficiently solve the PFP using either the classical Newton-Raphson (NR) method or its fast decoupled version (FDXB) while still maintaining high accuracy. The preliminary stage for the dynamic homotopy problem is formulated and solved by employing integration techniques, where implicit and explicit schemes are studied. The dynamic problem assumes an initial condition that coincides with the initial estimate for a traditional iterative method such as NR. In this sense, the initial guess for the FPF is adequately set as a flat start, which is a starting for the case when this initialization is of difficult assignment for convergence. The static homotopy method requires a complete solution of a PFP per homotopy pathway point, while the dynamic homotopy is based on numerical integration methods. This approach can require only one LU factorization at each point of the pathway. Allocating these points properly helps avoid several PFP resolutions to build the pathway. The hybrid technique was evaluated for large-scale systems with poor conditioning, such as a 109,272-bus model and other test systems under stressed conditions. A scheme based on the implicit backward Euler scheme demonstrated the best performance among other numerical solvers studied. It provided reliable partial results for the dynamic homotopy problem, which proved to be suitable for achieving fast and highly accurate solutions using both the NR and FDXB solvers. Full article

(This article belongs to the Special Issue Modeling, Simulation and Optimization of Power System)

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Results determined by using only NR and a combination of dynamic homotopy, with <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>t</mi> <mo>=</mo> <mn>0.5</mn> </mrow> </semantics></math>, and the NR solver. Full article ">Figure 2
Integration solver performance when a smaller time-step <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>t</mi> <mo>=</mo> <mn>0.125</mn> </mrow> </semantics></math> was adopted after the step <math display="inline"><semantics> <mrow> <msub> <mi>t</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>0.01</mn> </mrow> </semantics></math>. Full article ">Figure 3
Plots indicating the evolution of the infinite norm of the PFP mismatches for three test systems when the NR solver is initialized by an explicit (FE or RK2) or implicit (BE) integration scheme, considering the homotopy pathway with five points, but only the instant <math display="inline"><semantics> <msub> <mi>t</mi> <mn>3</mn> </msub> </semantics></math> is changed. Full article ">Figure 4
Results for the evolution of states and decaying power mismatches for the <tt>case109272</tt>, when the BE solver is used for the dynamic homotopy process and the results are refined by the NR solver. Full article ">Figure 5
Evolution of the voltage magnitude and phase angle with the index k of a time instant <math display="inline"><semantics> <msub> <mi>t</mi> <mi>k</mi> </msub> </semantics></math> of the dynamic homotopy solver BE (dotted lines) or iterations for the NR solver (solid lines). Results are for the bus #6 of <tt>case109272</tt>, with different <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>t</mi> </mrow> </semantics></math>. Full article ">

31 pages, 18202 KiB

Open AccessArticle

MATLAB Application for Determination of 12 Combustion Products, Adiabatic Temperature and Laminar Burning Velocity: Development, Coding and Explanation

by Roberto Franco Cisneros and Freddy Jesus Rojas

Computation 2024, 12(9), 189; https://doi.org/10.3390/computation12090189 - 16 Sep 2024

Cited by 1 | Viewed by 653

Abstract

The determination of the characteristics and main combustion properties of fuels is necessary for post-implementation in different applications. Among the most important combustion properties of a fuel are the combustion products, flame temperature and laminar burning velocity. Therefore, this paper describes the step-by-step [...] Read more.

The determination of the characteristics and main combustion properties of fuels is necessary for post-implementation in different applications. Among the most important combustion properties of a fuel are the combustion products, flame temperature and laminar burning velocity. Therefore, this paper describes the step-by-step development and coding of a MATLAB application that can determine 12 combustion products, flame temperature and laminar burning velocity in order to understand the logic of calculus procedure, so any user would be able to make improvements of new functionalities (add more fuels, add more combustion products, etc.). The numerical procedure and methods (Gaussian elimination, Taylor Series and Newton–Raphson) parallel with their implementation as code lines for the development of the application are carried out using flow charts. In addition, simulations in Ansys Chemkin were performed and included in the application as part of the results comparison. It was found that: (1) The MATLAB Application codification and development were successfully explained in detail, (2) the functions and execution sequence are described by using flow charts and code extract, (3) the application is available to everyone for modifications, (4) the application can only be used for hydrocarbons fuels, (5) the application execution time registered was less than 8 s. Full article

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14 pages, 1181 KiB

Open AccessArticle

Prediction of Wind Turbine Gearbox Oil Temperature Based on Stochastic Differential Equation Modeling

by Hongsheng Su, Zonghao Ding and Xingsheng Wang

Mathematics 2024, 12(17), 2783; https://doi.org/10.3390/math12172783 - 9 Sep 2024

Viewed by 503

Abstract

Aiming at the problem of high failure rate and inconvenient maintenance of wind turbine gearboxes, this paper establishes a stochastic differential equation model that can be used to fit the change of gearbox oil temperature and adopts an iterative computational method and Markov-based [...] Read more.

Aiming at the problem of high failure rate and inconvenient maintenance of wind turbine gearboxes, this paper establishes a stochastic differential equation model that can be used to fit the change of gearbox oil temperature and adopts an iterative computational method and Markov-based modified optimization to fit the prediction sequence in order to realize the accurate prediction of gearbox oil temperature. The model divides the oil temperature change of the gearbox into two parts, internal aging and external random perturbation, adopts the approximation theorem to establish the internal aging model, and uses Brownian motion to simulate the external random perturbation. The model parameters were calculated by the Newton–Raphson iterative method based on the gearbox oil temperature monitoring data. Iterative calculations and Markov-based corrections were performed on the model prediction data. The gearbox oil temperature variations were simulated in MATLAB, and the fitting and testing errors were calculated before and after the iterations. By comparing the fitting and testing errors with the ordinary differential equations and the stochastic differential equations before iteration, the iterated model can better reflect the gear oil temperature trend and predict the oil temperature at a specific time. The accuracy of the iterated model in terms of fitting and prediction is important for the development of preventive maintenance. Full article

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14 pages, 3954 KiB

Open AccessArticle

Test Method for Single Satellite’s Inter-Satellite Link Pointing and Tracking via Ground Station

by Zhenqiang Hong, Xuxing Huang, Lifeng Yang, Zhiqiang Bian, Yong Yang and Shuang Li

Aerospace 2024, 11(9), 713; https://doi.org/10.3390/aerospace11090713 - 31 Aug 2024

Viewed by 682

Abstract

An inter-satellite link is a key technology that improves control accuracy, transmission efficiency, and autonomous capability of constellations. A satellite’s pointing and tracking abilities mainly determine the inter-satellite link’s performance, which should be validated through an in-orbit test. However, during the construction of [...] Read more.

An inter-satellite link is a key technology that improves control accuracy, transmission efficiency, and autonomous capability of constellations. A satellite’s pointing and tracking abilities mainly determine the inter-satellite link’s performance, which should be validated through an in-orbit test. However, during the construction of the constellation, the distribution of satellites does not satisfy the constraints of establishing the inter-satellite link. A test method for inter-satellite link pointing and tracking is developed with respect to a single satellite. A practical mission scenario for testing inter-satellite links’ performance is constructed. A virtual satellite is introduced as the target satellite to establish an inter-satellite link with the local satellite. The orbit of the virtual target satellite between two ground stations is characterized based on the Newton–Raphson method. By comparing the predicted and actual time differences between two ground stations receiving the signals from the local satellite, the inter-satellite link pointing and tracking abilities are evaluated independently. Numerical simulations verify the design of the virtual satellite. The single satellite test method for inter-satellite link pointing and tracking abilities is available. Full article

(This article belongs to the Special Issue Spacecraft Dynamics and Control (2nd Edition))

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18 pages, 12471 KiB

Open AccessArticle

Research on Prediction of Ash Content in Flotation-Recovered Clean Coal Based on NRBO-CNN-LSTM

by Yujiao Li, Haizeng Liu and Fucheng Lu

Minerals 2024, 14(9), 894; https://doi.org/10.3390/min14090894 - 30 Aug 2024

Viewed by 764

Abstract

Ash content is an important production indicator of flotation performance, reflecting the current operating conditions of the flotation system and the recovery rate of clean coal. It also holds significant importance for the intelligent control of flotation. In recent years, the development of [...] Read more.

Ash content is an important production indicator of flotation performance, reflecting the current operating conditions of the flotation system and the recovery rate of clean coal. It also holds significant importance for the intelligent control of flotation. In recent years, the development of machine vision and deep learning has made it possible to detect ash content in flotation-recovered clean coal. Therefore, a prediction method for ash content in flotation-recovered clean coal based on image processing of the surface characteristics of flotation froth is studied. A convolutional neural network –long short-term memory (CNN-LSTM) model optimized by Newton–Raphson is proposed for predicting the ash content of flotation froth. Initially, the collected flotation froth video is preprocessed to extract the feature dataset of flotation froth images. Subsequently, a hybrid CNN-LSTM network architecture is constructed. Convolutional neural networks are employed to extract image features, while long short-term memory networks capture time series information, enabling the prediction of ash content. Experimental results indicate that the prediction accuracy on the training set achieves an R value of 0.9958, mean squared error (MSE) of 0.0012, root mean square error (RMSE) of 0.0346, and mean absolute error (MAE) of 0.0251. On the test set, the prediction accuracy attains an R value of 0.9726, MSE of 0.0028, RMSE of 0.0530, and MAE of 0.0415. The proposed model effectively extracts flotation froth features and accurately predicts ash content. This study provides a new approach for the intelligent control of the flotation process and holds broad application prospects. Full article

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22 pages, 1772 KiB

Open AccessArticle

Optimal Searching-Based Reference Current Computation Algorithm for IPMSM Drives Considering Iron Loss

by Péter Stumpf and Tamás Tóth-Katona

Actuators 2024, 13(8), 321; https://doi.org/10.3390/act13080321 - 21 Aug 2024

Viewed by 636

Abstract

Interior permanent magnet synchronous machines (IPMSMs) are widely used as traction motors in the electric drive-train because of their high torque-per-ampere characteristics and potential for wide field weakening operation to expand the constant power range. The paper aims to introduce the most important [...] Read more.

Interior permanent magnet synchronous machines (IPMSMs) are widely used as traction motors in the electric drive-train because of their high torque-per-ampere characteristics and potential for wide field weakening operation to expand the constant power range. The paper aims to introduce the most important equations to calculate the operating trajectories of an IPMSM for optimal control. The main contribution is that the optimal operating trajectories are calculated by a feedforward, Newton–Raphson method-based searching algorithm that considers the iron loss resistance of IPMSMs. Steady-state calculations and dynamic simulation results prove the theoretical findings. Full article

(This article belongs to the Section High Torque/Power Density Actuators)

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14 pages, 368 KiB

Open AccessArticle

Fibonacci Wavelet Collocation Method for Solving Dengue Fever SIR Model

by Amit Kumar, Ayub Khan and Abdullah Abdullah

Mathematics 2024, 12(16), 2565; https://doi.org/10.3390/math12162565 - 20 Aug 2024

Viewed by 582

Abstract

The main focus in this manuscript is to find a numerical solution of a dengue fever disease model by using the Fibonacci wavelet method. The operational matrix of integration has been obtained using Fibonacci wavelets. The proposed method is called Fibonacci wavelet collocation [...] Read more.

The main focus in this manuscript is to find a numerical solution of a dengue fever disease model by using the Fibonacci wavelet method. The operational matrix of integration has been obtained using Fibonacci wavelets. The proposed method is called Fibonacci wavelet collocation method (FWCM). This biological model has been transformed into a system of nonlinear algebraic equations by using the Fibonacci wavelet collocation scheme. Afterward, this system has been solved by using the Newton–Raphson method. Finally, we provide evidence that our results are better than those obtained by various current approaches, both numerically and graphically, demonstrating the method’s accuracy and efficiency. Full article

(This article belongs to the Special Issue Advanced Numerical Methods for Differential Equations: Recent Developments, Analysis and Applications)

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Comparison of solution <math display="inline"><semantics> <mrow> <mi>S</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math> vs. t. Full article ">Figure 2
Comparison of solution <math display="inline"><semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math> vs. t. Full article ">Figure 3
Comparison of solution <math display="inline"><semantics> <mrow> <mi>R</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math> vs. t. Full article ">Figure 4
Comparison and error plots for <math display="inline"><semantics> <mrow> <mi>S</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math> vs. t. Full article ">Figure 5
Comparison and error plots for <math display="inline"><semantics> <mrow> <mi>I</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math> vs. t. Full article ">Figure 6
Comparison and error plots for <math display="inline"><semantics> <mrow> <mi>R</mi> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </semantics></math> vs. t. Full article ">

16 pages, 4713 KiB

Open AccessArticle

An Efficient Quadratic Programming Method for Kinematic Control of Redundant Manipulators under Joint Velocity Constraints

by Zongdao Li, Pengfei Wang, Wenlong Zhao, Tao Wu and Qingdu Li

Actuators 2024, 13(7), 273; https://doi.org/10.3390/act13070273 - 20 Jul 2024

Viewed by 1125

Abstract

This paper presents an efficient inverse kinematics solution for redundant robotic arms. The proposed method combines the principles of continuation methods, improves the instability of the computation time by increasing the convergence of the kinematics function, and improves the efficiency of traditional numerical [...] Read more.

This paper presents an efficient inverse kinematics solution for redundant robotic arms. The proposed method combines the principles of continuation methods, improves the instability of the computation time by increasing the convergence of the kinematics function, and improves the efficiency of traditional numerical methods. The effectiveness and efficient performance of the method are demonstrated through comparative experiments. The computational speed of the method is twice as fast as the Newton–Raphson method under joint limit constraints and equal solution accuracy. Full article

(This article belongs to the Section Actuators for Robotics)

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Comparisons of IK problems using Diana7. Full article ">Figure 2
Comparisons of IK problems using Kinova Gen3. Full article ">Figure 3
Comparisons of IK problems using X02. Full article ">Figure 4
Comparisons of IK problems using Kuka iiwa14. Full article ">Figure 5
Comparisons of IK problems using Franka Emika Panda. Full article ">Figure 6
Error convergence in iterations. CM1 and CM2 represent, respectively, the proposed method with different increments of the homotopy parameter <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Δ</mi> <mi>s</mi> </mrow> </semantics></math>. Full article ">Figure A1
Agile robot Diana7 with the home configuration (in millimeters). Full article ">Figure A2
X02 robot and its 7-DOF arms. Full article ">

18 pages, 3312 KiB

Open AccessArticle

A Novel Geothermal Wellbore Model Based on the Drift-Flux Approach

by Yin Yuan, Weiqing Li, Jiawen Zhang, Junkai Lei, Xianghong Xu and Lihan Bian

Energies 2024, 17(14), 3569; https://doi.org/10.3390/en17143569 - 20 Jul 2024

Cited by 1 | Viewed by 786

Abstract

Geothermal energy, being a clean energy source, has immense potential, and accurate wellbore modeling is crucial for optimizing the drilling process and ensuring safety. This paper presents a novel geothermal wellbore model based on the drift-flux approach, tested under three different temperature and [...] Read more.

Geothermal energy, being a clean energy source, has immense potential, and accurate wellbore modeling is crucial for optimizing the drilling process and ensuring safety. This paper presents a novel geothermal wellbore model based on the drift-flux approach, tested under three different temperature and pressure well conditions. The proposed model integrates the conservation equations of mass, momentum, and energy, incorporating the gas–liquid two-phase flow drift-flux model and heat transfer model. The key features include handling the heat transfer between the formation and the wellbore, addressing the slip relationship between the gas and liquid phases, and accounting for wellbore friction. The nonlinear equations are discretized using the finite difference method, and the highly nonlinear system is solved using the Newton–Raphson method. The numerical simulation, validation, and comparison with existing models demonstrate the enhanced accuracy of this model. In our tests, the model achieved a high accuracy in calculating the bottom-hole pressure and temperature, with mean relative errors (MREs) significantly lower than those of other models. For example, the MREs for the bottom-hole pressure and temperature of the Rongxi area well in Xiongan, calculated by this model, are 1.491% and 1.323%, respectively. These results offer valuable insights for optimizing drilling parameters and ensuring drilling safety. Comparisons indicate that this approach significantly outperforms others in capturing the complex dynamics of geothermal wellbores, making it a superior tool for geothermal energy development. Full article

(This article belongs to the Section H2: Geothermal)

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20 pages, 10916 KiB

Open AccessArticle

Transient Friction Analysis of Pressure Waves Propagating in Power-Law Non-Newtonian Fluids

by Hang Li, Chenliang Ruan, Yanlin Su, Peng Jia, Haojia Wen and Xiuxing Zhu

Appl. Sci. 2024, 14(14), 6331; https://doi.org/10.3390/app14146331 - 20 Jul 2024

Viewed by 579

Abstract

Modulated pressure waves propagating in the drilling fluids inside the drill string are a reliable real-time communication technology that transmit data from downhole to the surface during oil and gas drilling. In the analysis of pressure waves’ propagation characteristics, the modeling of transient [...] Read more.

Modulated pressure waves propagating in the drilling fluids inside the drill string are a reliable real-time communication technology that transmit data from downhole to the surface during oil and gas drilling. In the analysis of pressure waves’ propagation characteristics, the modeling of transient friction in non-Newtonian fluids remains a great challenge. This paper establishes a numerical model for transient pipe flow of power-law non-Newtonian fluids by using the weighted residual collocation method. Then, the Newton–Raphson method is applied to solve the nonlinear equations. The numerical method is validated by using the theoretical solution of Newtonian fluids and is proven to converge reliably with larger time steps. Finally, the influencing factors of the wall shear stress are analyzed using this numerical method. For shear-thinning fluids, the friction loss of periodic flow decreases with the increase in flow rate, which is opposite to the variation law of friction with the flow rate for stable pipe flow. Keeping the amplitude of pressure pulsation unchanged, an increase in frequency leads to a decrease in velocity fluctuations; therefore, the friction loss decreases with the increase in frequency. Full article

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