FMI Co-simulation 1D-3D SIMSEN-CFX

Analytical study on water hammer pressure in pressurized conduits with a throttled surge chamber for slow closure

Acoustic resonance in a flow piping system may trigger an occupational or safety issue and can lead to equipment damage. Computational fluid dynamics (CFD) simulations are often used to predict such resonance phenomenon. However, this approach is generally time consuming and requires specialized training and expensive software. In addition, CFD is not viable for routine design purposes due to its computational expense. In this study, an alternative plane-wave based model for a hydraulic piping system is therefore developed using the transfer matrix method (TMM). Such a model can offer a fast yet reasonably accurate prediction for self-sustained pressure oscillation in a piping system. The advantage of the TMM is the simplicity with which the transfer matrix of a system can be generated from a combination of the TMs of its subsystems via matrix operations. The hydraulic piping system under study consists of a duct with constant cross-sectional area, diffuser, nozzle, bends, valves and orifice plate. The TM of each component is developed and compared to either CFD predictions or available experimental data, the TM of the complete system is derived. Design recommendations are made to reduce and/or avoid resonance in the piping system.

Numerical and experimental investigation of optimum surge tank forms in hydroelectric power plants

Based on actual hydraulic structure, the linear and nonlinear hydro power system model with surge tank was established for the first time. The simulation results of model demonstrate that the linear model with surge tank and that of individual penstock exists essential difference. The step response of individual penstock model is monotonic rising up to stable state, but that of model with surge tank is vibrating badly. The nonlinear model with surge tank is dynamic stable.

The importance of renewable energy sources for the electrical power supply has grown rapidly in the past decades. Their often unpredictable nature however poses a threat to the stability of the existing electric grid. Hydroelectric powerplants play an important role in regulating the integration of renewable energy sources into the network by supplying on-demand load balancing as well as primary and secondary power network control. Therefore, the operating ranges of hydraulic machines has to be continuously extended, which potentially produces undesirable flow phenomena involving cavitation. An example is the formation of a gaseous volume in the swirling flow leaving a Francis turbine runner at off-design operating conditions. At high load, this so called vortex rope is shaped axisymmetrically and may enter a self-excited oscillation, measurable through significant fluctuations of the pressure throughout the system and the mechanical torque transferred to the generator. The main objective of the present work is the identification of the physical mechanisms governing this self-sustained, unstable behavior by measurement. Furthermore, the key parameters of numerical approaches using one-dimensional hydroacoustic flowmodels or CFD require experimental validation. For this purpose, the measurements provide a comprehensive data base of various flow and system parameters at varying operating conditions. Two test cases are studied, a small scale hydraulic circuit with a micro-turbine as well as a reduced scale physical model of an existing Francis turbine. On the first test case, the study of the flow rate fluctuations up- and downstream of the oscillating vortex rope in the draft tube, together with the volume of the cavity, revealed the destabilizing effect of the flow swirl in the draft tube inlet. The second test case accurately simulates the behavior of an actual hydraulic power plant. Investigations range from a local study of the flow field in the draft tube cone bymeans of LDV, PIV, high speed visualization and wall pressure measurements to a global analysis, considering the response of the hydraulic and mechanical system to the excitation by the vortex rope oscillation. Among the main observations is a periodical variation of the flow swirl in the draft tube, synchronized with the pressure oscillations. This is likely to be caused by a cyclically appearing volume of cavitation on the runner blades, modifying the relative flow angle at the outlet. The interaction of the blade cavitation and the vortex rope oscillation via the flow swirl is found to play a crucial role in the occurrence of self-excited pressure oscillations in Francis turbines.

This paper presents an overview of the design and operation of an offshore hydraulic pumping system on Platform Eve when it was converted from a power-oil to a power-water system in 1983. Also described are some useful economic and operational data obtained from experience with hydraulic pumping systems over several years of operation.

The authors outline the development of an expert assistant for hydraulic power system simulation and design. The conventional static design/drafting procedure is integrated with dynamic system design. The expert assistant helps a designer use CAD software, size components, and produce simulations of the hydraulic system's dynamic responses. The functional description and configuration of the whole process is expertly assisted. The task requirements are outlined and the structure of the resulting expert system is described. >

Vibration analysis of a longitudinal polarized piezoelectric tubular energy harvester

An elbow-shaped surge tank is proposed to suppress the pressure pulsations. The transfer matrix method was developed and the mathematical model was established to predict the distribution of pressure pulsations in the piping system (on which a surge tank was already installed) with an elbow-shaped surge tank. Simulation work of the whole piping system was performed. The results show that the elbow-shaped surge tank has good performance to attenuate the pressure pulsations. The frequency analysis shows that the amplitude for the first pulsation frequency is attenuated to a low level. The impulse response was analyzed to examine the efficiency of suppressing pulsations by using the suppressor. The theoretical analysis showed that there exists the optimal suppression performance when setting the distance between the elbow-shaped surge tank and the existing one. Meanwhile, modifying the ratio of length to diameter with a fixed surge volume could also impact the pressure pulsations. The analysis results can be used as a reference in designing and installing the elbow-shaped surge tank.

Despite the accumulated vast theoretical and practical knowledge on the flood-related topics, the lack of precautions taken against the natural disasters keeps causing fatality and property damage. In this study, a recent flood event in a run-of-river-type hydroelectric power plant in Tavsanli District of Kutahya was analyzed and the main reasons for the occurred damage were investigated. First, a stochastic approach was followed to obtain the essential parameters used in the design procedures. In support of the whole investigation, numerical simulation of the river flow was performed to analyze the river flow behavior using computational fluid dynamics method. In addition, geographical information system was implemented to understand the site-specific topography and its influence. Different types of analyses and fieldwork were combined and used to help reveal the actual scenario and showed that a non-catastrophic natural event resulted in a costly damage due to a chain of wrong actions (misinterpretation of the functions of certain safety structures and lack of taking precautions at the hill slopes) in the local implementation of the project. The damage initially was believed to be due to the rise in the water level in the nearby river. It is believed the picture presented here will be useful in amending arrangements to avoid such damages in the future for a large number of comparable power plants in Turkey.

Fluid-Structure Coupling Effects on the Dynamic Response of Pump-Turbine Guide Vanes

In order to increase the installed capacity, the refurbishment of Gondo high-head power plant required a modification of the existing surge tank by installing a throttle at its entrance. In a previous study, the geometry of this throttle was optimized by physical modeling to achieve the target loss coefficients as identified by a transient 1D numerical analysis. This study complements previous analyses by means of 3D numerical modeling using the commercial software ANSYS-CFX 19 R1. Results show that: (i) a 3D computational fluid dynamics (CFD) model predicts sufficiently accurate local head loss coefficients that agree closely with the findings of the physical model; (ii) in contrast to a standard surge tank, the presence of an internal gallery in the surge tank proved to be of insignificant effect on a surge tank equipped with a throttle, as the variations in the section of the tank cause negligible local losses compared to the ones induced by the throttle; (iii) CFD investigations of transient flow regimes revealed that the head loss coefficient of the throttle only varies for flow ratios below 20% of the total flow in the system, without significantly affecting the conclusions of the 1D transient analysis with respect to minimum and maximum water level in the surge tank as well as pressure peaks below the surge tank. This study highlights the importance of examining the characteristics of a hydraulic system from a holistic approach involving hybrid modeling (1D, 3D numerical and physical) backed by calibration as well as validation with in-situ measurements. This results in a more rapid and economic design of throttled surge tanks that makes full use of the advantages associated with each modeling strategy.

This paper presents the hardware in the loop of control the position of electro hydraulic servo system based on Data Acquisition Card (NI-6014) and hybrid Model Predictive Controller (MPC). The realization of hybrid MPC depends on using Data Card and Matlab/ Simulink as the core of the control system. In addition, this paper discusses the using of Cuckoo Search Algorithm (CSA) for optimal tuning of the traditional controller parameters as a part of hybrid MPC controller. The experimental implementation of the studied system has been investigated using REXROTH components. The Electro Hydraulic Servo System mechanism (EHSS) plays an important role in industrial applications, especially in flight simulators, aircraft landing gear system, material testing machine and hydraulic press machines. The key reason of applying hydraulic systems on these applications is that it can give a high torque and high force. The theoretical and experimental results demonstrate that the values of performance criteria (settling, rise times and system overshoots) are the minimum in case of realization hybrid MPC position control over using traditional and MPC controllers. It also introduced that the integral time absolute error for various types of test signals (Multistep, sinusoidal and square signals) are a minimum values in case of using the proposed strategy in compared with the traditional and MPC controllers. In addition, hybrid MPC achieved the required physical limits of the actuator. As a general conclusion, one can conclude that the hybrid model predictive control has the priority of applying it in the field of electro hydraulic servo system due to the mentioned advantages.

Intelligent fault diagnosis systems of equipment are essential in industries, to prevent failures, reduce downtime and increase plant availability. In this context, this work proposes a methodology to develop diagnostic systems for detecting anomalies and identifying failures in the piping system due to malfunctioning pumps, such as cavitation. Relevant information is extracted based on motor electric current, available in PROFINET networks by smart relays, widely used in this type of application. A prototype of a hydraulic piping system was created for data collection and methodology validation. Machine learning tools for extracting and selecting features (such as standard deviation, entropy, harmonics, among others), and an SVM-based model for pattern recognition, are used to diagnose the status of the centrifugal pump. The results achieved were 88.7 % of accuracy for cavitation fault detection and 100.0% for dry running operation. Thus, the methodology is feasible and efficient, indicating an opportunity to improve the use of data available by smart relays in industrial network communication.

A hydraulic system does not only consist of pumps, motors, valves and hydraulic piping. This chapter deals with the parts in the hydraulic system that maintain the condition of the hydraulic fluid. A proper design for these sub systems is very important for the lifetime of the hydraulic system.