Search Results (37)

The main distributing valve (MDV) plays a core role in hydraulic amplification and precise control within the hydro-turbine governing system, and its spool position dynamics directly affect the regulation quality and stability of the hydro-turbine generator unit. However, developing a high-fidelity dynamic model of the MDV remains challenging, as existing methods typically rely on linearization assumptions and fail to fully account for system uncertainties, resulting in limited accuracy and poor cross-condition stability. To address this issue, this paper proposes a mechanistic–data-driven hybrid modeling method. Firstly, a modular modeling strategy is adopted to accurately construct a nonlinear mechanism-based model (MBM) that conforms to the actual industrial system. Secondly, to address the unknown dynamics not captured by the MBM, a Bayesian optimization-enhanced Light Gradient Boosting Machine (BO-LightGBM) model is developed. Then, a cascade–additive architecture is employed to achieve effective integration of the two. Finally, verification experiments are conducted under various dynamic processes based on the actual operating data of the governor. The results show that the proposed hybrid model significantly outperforms the other five comparison models in terms of accuracy and stability while retaining physical interpretability. This provides a more practically valuable solution for the dynamic modeling and simulation of hydroturbine actuators. Full article

The development and function of the heart are governed by a highly coordinated network of regulatory mechanisms, among which miRNAs play a central role. These small, non-coding molecules modulate gene expression predominantly through mRNA degradation. This narrative review aims to summarize current knowledge about biogenesis, its impact on heart development and function, and its clinical implications in pediatric cardiology. We discuss how specific miRNAs contribute to shaping the normal heart and influencing the pathogenesis of congenital malformations. Furthermore, we review disease-specific miRNA signatures identified in the most common congenital heart defects and some acquired diseases, including hypoplastic left heart syndrome (HLHS), tetralogy of Fallot (TOF), bicuspid aortic valve (BAV), septation defects, cardiomyopathies, arrhythmias, and myocarditis. Many studies indicate that circulating and tissue miRNAs can become non-invasive biomarkers for early diagnosis and disease monitoring. Experimental data suggest their potential use in treatment despite many delivery and safety challenges. However, further research is necessary to fully exploit the potential of miRNAs and effectively translate these findings into clinical practice in pediatric cardiology. Full article

Flow field design in proton exchange membrane fuel cells (PEMFCs) is a critical issue, as it plays an important role in governing reactant transport dynamics and cell performance. In this work, numerical studies of a single Tesla-valve flow field were conducted. The influence of loop radius, channel angle, and channel height on the performance of PEMFCs were fully explored. Then, aiming to maximize the output current density, this study optimized the Tesla-valve flow field configuration through a framework that integrates Gaussian process modeling with a Genetic Algorithm (GA). The approach efficiently identifies the optimal geometric parameters, highlighting effective synergy between the surrogate model and intelligent evolutionary optimization for enhanced performance. Simulation results show that the current density at 0.4 V and the highest power density have been improved by more than 10% compared to the baseline design for both forward and reverse flow. The optimized Tesla valve design has been compared with conventional parallel and serpentine flow fields of the same flow area. Results show that, despite the larger pressure drop for the single channel case—which is due to the insufficient length of the serpentine channel—the Tesla-valve flow field demonstrated superior performance in other metrics, including current and power density, under both flow directions. Full article

To gain deeper insights into the influence of pipe parameters on water hammer properties and achieve the accurate simulation of the hydraulic transient process in pipeline systems, the Finite Volume Method (FVM) is adopted. The solution scheme, incorporating a second-order MUSCL-type reconstruction, is derived, and the numerical solution process is detailed. For enhanced accuracy, the unsteady friction term is included in the numerical solution of the governing water hammer equations. The method is validated through a comparison with experimental data and the verification of mesh and Courant number independence, confirming both its efficiency and accuracy. The calculation error of the peak water head is less than 5%. Finally, an engineering case is studied to investigate valve arrangement and operation. Optimization yields the optimal valve position and operating parameters. This analysis provides valuable reference for pipeline system design. Full article

The water hammer phenomenon, characterized by transient pressure surges due to rapid fluid deceleration in pipelines, poses significant risks to hydraulic systems. Valve closure time is a critical parameter influencing pressure magnitude, necessitating precise calibration to ensure system safety. While numerical methods like the MacCormack scheme provide accurate solutions, their computational intensity limits practical applications. This study addresses this limitation by proposing a machine learning (ML) framework employing a multilayer perceptron (MLP) artificial neural network (ANN) to predict optimal pressure values—defined as the lowest maximum pressure obtained for several closure laws at a given closure time—corresponding to specific valve closure times. The ANN was trained on 637 simulations generated via the MacCormack method, which solves the hyperbolic partial differential equations governing transient flow in a reservoir-pipeline-valve (RPV) system. Performance evaluation metrics demonstrate the ANN’s exceptional robustness and accuracy, achieving a root mean square error (RMSE) of 0.068, Nash-Sutcliffe efficiency (NSE) of 0.99, and a correlation coefficient (R) of 0.99, with a maximum relative error below 1%. The results highlight the ANN’s superior predictive accuracy and flexibility in capturing complex transient flow dynamics, outperforming conventional numerical methods. Notably, the ANN reduced computational time from days for iterative simulations to mere seconds, enabling rapid prediction of pressure-time curves critical for real-time decision-making. This framework offers a computationally efficient and reliable alternative for optimizing valve closure strategies, mitigating water hammer risks, and enhancing pipeline safety. By bridging numerical rigor with machine learning, this work enhances hydraulic infrastructure resilience across industrial and urban networks. Full article

This paper examines the dual impact of trapped air on fluid transients in pressurised conduits, highlighting both its beneficial and detrimental impacts. This research analyses transient pressures caused by rapid valve closure in pipelines that contain air pockets and small bubbles dispersed within the liquid phase, by a hydraulic jump occurring at the downstream edge of the pockets. Experiments and numerical simulations were conducted with the valve positioned at the ends of the test section on both the inflow and outflow sides. A numerical model utilising the four-point centred scheme and method of characteristics was developed to resolve the governing equations of two-phase flow and was experimentally validated. The results indicate that entrapped air significantly influences hydraulic transients. When the valve is positioned downstream, air pockets and bubbles reduce pressure transients, illustrating a favourable effect. Conversely, when the valve is positioned upstream, adverse pressure transients occur, highlighting a detrimental impact. These outcomes underscore the importance of considering trapped air in pipeline systems, as its existence can either mitigate or exacerbate transient pressures depending on the configuration of the pipeline. The research highlights the significance of considering entrapped air in the design and evaluation of pressurised conduits to improve performance and prevent adverse effects. Full article

Several car manufacturers have encountered corrosion in certain mechanical components caused by chlorine in fuel. The current regulations governing the quality of fuel allowed for trade are briefly described. Next, this paper analyzes the possible origin of chlorine in damaged components. In particular, the phenomenon of corrosion found in EGR valves and EGR coolers is analyzed. The analyses conducted to determine the nature of the corrosion and its origin are illustrated. Finally, the effects of the phenomenon on engine operation are analyzed, depending on the type of damaged component. Full article

This study investigates the transient flow dynamics and pressure interactions within Tesla valve configurations through comprehensive CFD simulations. Tesla valves offer efficient passive fluid control without the need for external power, making them favorable in various applications. Previous observations indicated that Tesla valves effectively reduce the amplitude of pressure transients, prolonging their duration and distributing energy over an extended timeframe. While suggesting a potential role for Tesla valves as pressure dampers during transient events, the specific mechanisms behind this behavior remain unexplored. This research focuses on elucidating the internal dynamics of Tesla valves during transient events, aiming to unravel the processes responsible for the observed attenuation in pressure transients. This study reveals the emergence of “pressure pockets” within Tesla valves, deviating from conventional uniform pressure fronts. These pockets manifest as discrete chambers with varying lengths and volumes, contributing to the non-uniform propagation of pressure throughout the system. This investigation employs advanced CFD simulations as a crucial tool to unravel the governing dynamics of transient flow within Tesla valve configurations. By elucidating underlying fluid dynamics, this study lays the groundwork for future Tesla valve design optimization, holding potential implications for applications where the control of transient flow events is crucial. Full article

Cavitation is a phase-change phenomenon from the liquid to the gas phase due to an increased flow velocity. As it causes severe erosion and noise, it is harmful to hydraulic machinery such as pumps, valves, and screw propellers. However, it can be utilized for water treatment, in chemical reactors, and as a mechanical surface treatment, as radicals and impacts at the point of cavitation bubble collapse can be utilized. Mechanical surface treatment using cavitation impacts is called “cavitation peening”. Cavitation peening causes less pollution because it uses water to treat the mechanical surface. In addition, cavitation peening improves on traditional methods in terms of fatigue strength and the working life of parts in the automobile, aerospace, and medical fields. As cavitation bubbles are utilized in cavitation peening, the study of cavitation bubbles has significant value in improving this new technique. To achieve this, many numerical analyses combined with field experiments have been carried out to measure the stress caused by bubble collapse and rebound, especially when collapse occurs near a solid boundary. Understanding the mechanics of bubble collapse can help to avoid unnecessary surface damage, enabling more accurate surface preparation, and improving the stability of cavitation peening. The present study introduces three cavitation bubble types: single, cloud, and vortex cavitation bubbles. In addition, the critical parameters, governing equations, and high-speed camera images of these three cavitation bubble types are introduced to support a broader understanding of the collapse mechanism and characteristics of cavitation bubbles. Then, the results of the numerical and experimental analyses of non-spherical cavitation bubbles are summarized. Full article

Gas explosion accidents can easily lead to large-scale casualties and economic losses, significantly impeding the urban development. The purpose of this study was to comprehensively review and investigate a significant gas fuel explosion accident in Yinchuan City, China, and to conduct an in-depth discussion on process traceability, failure risk, hazard prevention, and urban development related to the accident. The research found that the accidental failure of double-valve liquefied petroleum gas cylinders and human error were identified as the direct causes of gas leakage. The numerical results indicated that the progression of the accident disaster was chaotic and highly destructive. The maximum explosion overpressure of 92 kPa resulted in severe shock-wave damage to personnel, leading to the complete destruction and collapse of the 0.2 m thick solid brick wall and obstructing the stairway for escape. The rapid change in temperature and oxygen levels caused by the explosion led to the risk of burns and asphyxiation for personnel at the scene. By utilizing the system safety theory, a gas leakage accident control structure system was developed. This system comprised four key levels: the local government, gas management department, gas company, and individual user. The tragedy of 31 deaths was ultimately caused by a serious lack of safety constraints on the behavior of the lower level by the higher level. The research conclusions are of great significance for preventing clean fuel explosion accidents and ensuring sustainable urban development, especially in the face of the negative impact of accidents. Full article

Water leakages are assessed with an extended period simulation (traditional analysis) in water distribution networks. However, when rapid manoeuvres regulate valves, the conventional analysis proves unsuitable for representing the water volume of leaks. Under these circumstances, the Rigid Water Column Model can be utilised to accurately compute the quantity of water volume leaks. This method has been applied to single and parallel pipelines to predict water leakages, considering the opening and closure manoeuvres of regulating valves. This research develops governing equations using the Rigid Column Model to predict water volume leaks in a general scheme of series pipelines, accounting for the opening and closure manoeuvres in regulating valves. The practical application involves two branches of a series pipeline with internal pipe diameters of 0.45 and 0.25 m and pipe lengths of 1200 and 1400 m, respectively. The results of this practical application demonstrate the accuracy of the Rigid Column Model and its relevance in real-world scenarios. For instance, the model shows that traditional analysis can overestimate water volume leaks by approximately 72% when a closure manoeuvre regulates valves for 200 s and by about 28% for 30 s, highlighting the need for a more accurate method. Full article

Water distribution systems (WDSs) are essential elements for the prosperity and development of societies around the globe. However, over time, the pipeline network starts to age and deteriorate, which results in an increasing rate of breaks and water loss due to leakages. Many countries have started government-funded plans to upgrade and rehabilitate their WDS network components to overcome these challenges. This study proposes an optimization framework that addresses these issues and offers potential benefits. It aims to achieve the optimal upgrading strategies considering network operation (hydraulic) performance and upgrading cost, including investment and non-revenue water costs. The upgrade of the WDS network in the model consists of replacing pipes and controlling the pressure-reducing valve (PRV) settings to reduce leakages. The proposed framework is demonstrated using a small-sized benchmark WDS. The study’s outcomes provide the utilities’ operators and municipalities’ decision-makers with a guiding tool to choose the optimal upgrading strategy for their WDS networks at the lowest cost and optimum operation performance. The methodology involves simulating various leakage scenarios and applying optimization techniques to find the best combination of pipe replacements and PRV settings. This approach ensures a balance between minimizing leakage rates and controlling upgrading costs. The framework achieved a reduction of leakage up to 20% from the original leakage with a 70% probability for the tested benchmark network. The optimization framework can also offer a range of upgrading strategies, with a trade-off between the WDS network leakage reduction and the required cost of the upgrading strategy. Full article

Dimensionless governing equations of unsteady flow and solutions for the pipeline systems having a surge tank were developed. Frequency domain pressure response expressions for two widely used water supply systems were analyzed in dimensionless frequency and time domains. One is the simple reservoir pipeline surge tank valve system and the other is the pipeline system with pump and check valve protected by surge tank. Two different dimensionless expressions for the surge tank were developed and the performance of two expressions was compared. The frequency response pattern of impedance at the downstream valve indicated that the system resonance was determined by the lengths of the main pipeline and the connector and the locations of the surge tank and check valve for the protection of the pumping station. The difference between the simple pipeline system and that of a pump with a check valve was expressed in terms of the phase difference in frequency response distribution. The integrated pressure response for the protected pipeline section was evaluated considering the impact of surge protection in the frequency domain. A better understanding of system behavior can be obtained in terms of specific component isolation both in the frequency and time domain pressure responses. The driven responses in the frequency and time domain can be an important basis for optimum design and operation conditions of water supply systems in dimensionless space. Full article

Pollutants in exhaust gases and the high fuel consumption of internal combustion engines remain key issues in the automotive industry despite the emergence of electric vehicles. Engine overheating is a major cause of these problems. Traditionally, engine overheating was solved using electric pumps and cooling fans with electrically operated thermostats. This method can be applied using active cooling systems that are currently available on the market. However, the performance of this method is undermined by its delayed response time to activate the main valve of the thermostat and the dependence of the coolant flow direction control on the engine. This study proposes a novel active engine cooling system incorporating a shape memory alloy-based thermostat. After discussing the operating principles, the governing equations of motion were formulated and analyzed using COMSOL Multiphysics and MATLAB. The results show that the proposed method improved the response time required to change the coolant flow direction and led to a coolant temperature difference of 4.90 °C at 90 °C cooling conditions. This result indicates that the proposed system can be applied to existing internal combustion engines to enhance their performance in terms of reduced pollution and fuel consumption. Full article

The purpose of this study is to provide an overview of the development of the modern low-speed marine two-stroke diesel engine from the point of view of the technical water cooling plant, taking into account and starting from the market requirements for power and speed, with information and design options relevant to the entire shipping industry. Thus, through the ideas of this project, we analyze notions and relevant aspects of systems related to marine slow turning engines, including the basic thermodynamic structure of the technical water system designed for a marine engine. This study also presents the design criteria that define the size and design concept of the engine structure components, with a focus on the technical water cooling installation. The concepts for the main engine hot parts served by the technical water cooling installation play a vital role in the marine technical water generator. The choices the engine designer must make regarding basic auxiliary systems, such as fuel injection and exhaust valve actuation, are important factors to keep in mind when installing a technical water generator onboard a ship. The automation and control systems that govern the modern electronic engine, which drive the supply pump of the technical water cooling system can provide a simplified view of the engine development process. In order to point out the contributions of this study, it is important to focus on the calculations used to determine the main parameters of a technical water generator especially designed for a midsized container ship. Full article