scholarly journals Fast–slow dynamic behaviors of a hydraulic generating system with multi-timescales

2019 ◽  
Vol 25 (23-24) ◽  
pp. 2863-2874 ◽  
Author(s):  
Jingjing Zhang ◽  
Diyi Chen ◽  
Hao Zhang ◽  
Beibei Xu ◽  
Huanhuan Li ◽  
...  
Keyword(s):  
Dynamic Behavior ◽  
Transfer Functions ◽  
Stable Operation ◽  
Nonlinear Phenomena ◽  
Electrical Load ◽  
Surge Tank ◽  
Slow Dynamic ◽  
Dynamic Behaviors ◽  
Modeling Process ◽  
Generating System

Hydraulic generating systems are widely modeled in the literature for investigating their stability properties by means of transfer functions representing the dynamic behavior of the reservoir, penstock, surge tank, hydro-turbine, and the generator. Traditionally, in these models the electrical load is assumed constant to simplify the modeling process. This assumption can hide interesting dynamic behaviors caused by fluctuation of the load as actually occurred. Hence, in this study, the electrical load characterized with periodic excitation is introduced into a hydraulic generating system and the responses of the system show a novel dynamic behavior called the fast–slow dynamic phenomenon. To reveal the nature of this phenomenon, the effects of the three parameters (i.e., differential adjustment coefficient, amplitude, and frequency) on the dynamic behaviors of the hydraulic generating system are investigated, and the corresponding change rules are presented. The results show that the intensity of the fast–slow dynamic behaviors varies with the change of each parameter, which provides reference for the quantification of the hydraulic generating system parameters. More importantly, these results not only present rich nonlinear phenomena induced by multi-timescales, but also provide some theoretical bases for maintaining the safe and stable operation of a hydropower station.

Modeling for Dynamic Topology of Equipment Support Information Network with Certain Equipment Materials

2012 ◽  
Vol 485 ◽  
pp. 417-420
Author(s):  
Xiao Sun ◽  
Bin Liu ◽  
Gui Qi Wang ◽  
Qi Gen Zhong
Keyword(s):  
Dynamic Behavior ◽  
Dynamic Network ◽  
Information Network ◽  
Dynamic Behaviors ◽  
Dynamic Topology ◽  
Behavior Function ◽  
Modern Warfare ◽  
Behavior Models ◽  
Support Information

The importance of the equipment support had been recognized in the modern warfare and the dynamic network is an important characteristic of equipment support. Firstly, the dynamic reasons of the equipment support information network were analyzed. Then the dynamic behavior models were built and all dynamic behaviors were sorted generalized to four kinds of models. Meanwhile, a simulation instance was given, which had shown the dynamic behavior function had eye-catching effect to network statistics parameters changed, and the dynamic behavior importance for the equipment support information network was validated.

Modeling the Work of a Torque Converter during the Getaway Process of a Vehicle

2016 ◽  
Vol 823 ◽  
pp. 253-258
Author(s):  
Constantin Ovidiu Ilie ◽  
Octavian Alexa ◽  
Ion Lespezeanu ◽  
Marin Marinescu ◽  
Dănuț Grosu
Keyword(s):  
Simulation Model ◽  
Dynamic Behavior ◽  
Torque Converter ◽  
Virtual Simulation ◽  
Virtual Model ◽  
Performance Parameters ◽  
Transient Regimes ◽  
Modeling Process ◽  
Time Histories ◽  
Angular Velocities

The paper aims at issuing of a virtual simulation model that would be able to assess the actual working modes of a torque converter, both hydraulically and mechanically. To estimating the dynamic behavior we used the assessing equations of the converter’s performance coefficients. The rotational inertial phenomena due to the transient regimes during the getaway phase are also considered. The modeling process assumed the use of the pre-defined structures of the Simulink-Matlab and Simscape-Matlab modules. The virtual model of the torque converter was fed with the experimentally determined, performance parameters as input. The input also consisted of the inertia moments of the converter’s components. Eventually, by interrogating the simulation model, we’ve got and plotted the time histories of the converter’s impeller and turbine angular velocities during the vehicle’s getaway process.

scholarly journals Nonlinear Model and Dynamic Behavior of Photovoltaic Grid-Connected Inverter

2020 ◽  
Vol 10 (6) ◽  
pp. 2120 ◽  
Author(s):  
Zhi-Xian Liao ◽  
Dan Luo ◽  
Xiao-Shu Luo ◽  
Hai-Sheng Li ◽  
Qin-Qin Xiang ◽  
...  
Keyword(s):  
Bifurcation Diagram ◽  
Dynamic Behavior ◽  
Nonlinear Model ◽  
Nonlinear Dynamic ◽  
Optimization Design ◽  
Stable Operation ◽  
Control Parameters ◽  
Nonlinear Dynamic Behavior ◽  
Predictive Controller ◽  
Grid Connected Inverter

A photovoltaic grid-connected inverter is a strongly nonlinear system. A model predictive control method can improve control accuracy and dynamic performance. Methods to accurately model and optimize control parameters are key to ensuring the stable operation of a photovoltaic grid-connected inverter. Based on the nonlinear characteristics of photovoltaic arrays and switching devices, we established a nonlinear model of photovoltaic grid-connected inverters using the state space method and solved its model predictive controller. Then, using the phase diagram, folded diagram, and bifurcation diagram methods, we studied the nonlinear dynamic behavior under the influence of control parameters on both fast and slow scales. Finally, we investigated the methods of parameter selection based on the characteristics of nonlinear dynamic behavior. Our research shows that the predictive controller parameters are closely related to the bifurcation and chaos behaviors of the grid-connected photovoltaic inverter. The three-dimensional bifurcation diagram can be used to observe the periodic motion region of the control parameters. After selecting the optimization target, the bifurcation diagram can be used to guide the selection of control parameters for inverter design. The research results can be used to guide the modeling, stability analysis, and optimization design of photovoltaic grid-connected inverters.

On the Interaction of Swirling Flames in a Lean Premixed Combustor

2019 ◽  
Author(s):  
Gopakumar Ramachandran ◽  
Ankit Kumar Dutta ◽  
Harish Durairaj ◽  
Swetaprovo Chaudhuri
Keyword(s):  
Gas Turbine ◽  
Transfer Functions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Stable Operation ◽  
Flame Surface ◽  
Large Radius ◽  
Power Cost ◽  
Thermoacoustic Instability ◽  
Swirling Flames ◽  
Interaction Regions

Abstract Premixed or partially premixed swirling flames are widely used in gas turbine applications because of their compactness, high ignition efficiency, low NOx emissions and flame stability. A typical annular combustor consists of about eighteen to twenty-two swirling flames which interact (directly or indirectly) with their immediate neighbors even during stable operation. These interactions significantly alter the flow and flame topologies thereby bringing in some discrepancies between the single nozzle (SN) and multi nozzle (MN), ignition, emission, pattern factor and Flame Transfer Functions (FTF) characteristics. For example, in MN configurations, application of a model based on SN FTF data could lead to erroneous conclusions. Due to the complexities involved in this problem in terms of size, thermal power, cost, optical accessibility etc., a limited amount of experimental studies has been reported, that too on scaled down models with reduced number of nozzles. Here, we present a detailed experimental study on the behavior of three interacting swirl premixed flames, arranged in-line in an optically accessible hollow cuboid test section, which closely resembles a three-cup sector of an annular gas turbine combustor with very large radius. Multiple configurations with various combinations of swirl levels between the adjacent nozzles and the associated flame and flow topologies have been studied. Spatio-temporal information of the heat release rate obtained from OH* chemiluminescence imaging was used along with the acoustic pressure signatures to compute the Rayleigh index so as to identify the regions within the flame that pumps energy into the self-excited thermoacoustic instability modes. It was found that the structure of the flame-flame interaction regions plays a dominant role in the resulting thermoacoustic instability. To resolve the flow and reactive species field distributions in the interacting flames, two-dimensional, three component Stereoscopic Particle Image Velocimetry (SPIV) and Planar Laser Induced Fluorescence (PLIF) of hydroxyl radical was applied to all the test conditions. Significant differences in the flow structures among the different configurations were observed. Simultaneous OH-PLIF and SPIV techniques were also utilized to track the flame front, from which the curvature and stretch rates were computed. Flame surface density which is defined as the mean surface area of the reaction zone per unit volume is also computed for all the test cases. These measurements and analyses elucidate the structure of the interaction regions, their unique characteristics and possible role in thermoacoustic instability.

Optimal Solving of the Contradictory Problem between Hydraulic Cylinder's Precision and Stability with Extenics Theory

2013 ◽  
Vol 436 ◽  
pp. 518-530 ◽  
Author(s):  
Adrian Olaru
Keyword(s):  
Dynamic Behavior ◽  
Transfer Functions ◽  
Optimal Solution ◽  
Hydraulic Cylinder ◽  
Gradient Force ◽  
Maximal Acceleration ◽  
Flow Loss ◽  
On Line ◽  
Optimal Values ◽  
Optimal Area

In the optimisation stage of the systems one of the more important step is the optimisation of the dynamic behavior of all elements of the system, with priority the elements what have the slow frequency, like motors. The paper try to show how will be possible to optimise very easily the dynamic behavior of elements and systems, using LabVIEW propre instrumentation, the transfer functions theory and the Extenics Theory to solve the contradictory problems. By appling the virtual LabVIEW instrumentation will be possible to choose on-line the optimal values for each constructive and functional parameters of the elements and the systems to obtain one good dynamic answer: maximal acceleration without vibration, minimum answer time and maximal precision. In the paper was defined the optimal area of the precision-stability by imposed the breaking frequency from the Bode characteristics to optain the desired acceleration time. The paper shown the desired constraints and by using the Extenics theory was possible to choose the optimal solution of the precision-stability contradictory problem. In the research were used some different virtual LabVIEW instruments, to simulate the dynamic behavior of the cylinder when the active area, flow loss gradient, force gradient were changed in his desired physical field. By using the assisted research and the Extenics theory was possible to find the optimal values for the dynamic parameters and to be sure that working point will be inside of the desirable field of the hydraulic cylinder precision-stability.

scholarly journals The Dynamic Analysis of Two-Rotor Three-Bearing System

2015 ◽  
Vol 2015 ◽  
pp. 1-15
Author(s):  
Jianfei Yao ◽  
Jinji Gao ◽  
Ya Zhang ◽  
Weimin Wang
Keyword(s):  
Dynamic Behavior ◽  
Critical Speed ◽  
Amplitude Spectrum ◽  
Element Model ◽  
Nonlinear Phenomena ◽  
Motion Patterns ◽  
Unbalance Response ◽  
Mass Eccentricity ◽  
Coupling Stiffness ◽  
Bearing System

A finite element model considering the shear effect and gyroscopic effect is developed to study the linear and nonlinear dynamic behavior of two-rotor three-bearing system named N+1 configuration with rub-impact in this paper. The influence of rotational speed, eccentric condition, and the stiffness of coupling on the dynamic behavior of N+1 configuration and the propagation of motion are discussed in detail. The linear rotordynamic analysis included an evaluation of rotor critical speed and unbalance response. The results show that the critical speed and unbalance response of rotors are sensitive to coupling stiffness in N+1 configuration. In the nonlinear analysis, bifurcation diagram, shaft-center trajectory, amplitude spectrum, and Poincaré map are used to analyze the dynamic behavior of the system. The results of the research transpire that these parameters have the great effects on the dynamic behavior of the system. The response of the system with rub-impact shows abundant nonlinear phenomena. The system will exhibit synchronous periodic motion, multiperiodic motion, quasiperiodic motion, and chaotic motion patterns under rotor-stator rub interaction conditions. The dynamic response is more complicated for flexible coupling and two mass eccentricities than that of system with rigid coupling and one mass eccentricity.

Research and Analysis of Dynamic Behaviour in the Mathematical Models of the 6-Axle Locomotive

2011 ◽  
Vol 105-107 ◽  
pp. 541-544
Author(s):  
Van Tham Mai ◽  
Shi Jing Wu ◽  
Xiao Sun Wang ◽  
Jie Chen ◽  
S. A. K. S. Jafri
Keyword(s):  
Differential Equations ◽  
Mathematical Models ◽  
Dynamic Behavior ◽  
Dynamic Behaviour ◽  
Computer Software ◽  
Rolling Contact ◽  
Rolling Stock ◽  
Vertical Movements ◽  
Dynamic Behaviors ◽  
Second Order Differential Equations

With the aiming of mathematically modeling dynamic behavior in latitudinal and vertical movements of the 6-axle locomotive, this paper introduces the Kalker’s Wheel-Rail Rolling Contact Theories and their implementation in multibody codes. This paper also highlights methodology for solving inhomogeneous linear second-order differential equations with MATLAB computer software aided. The calculation has reported that the dynamic behaviors of Diesel-Electric 6-axle locomotive are significantly demonstrated. The calculation has reported that the dynamic behaviors of Diesel-Electric 6-axle locomotive are significantly demonstrated the requirements on Rolling stock Dynamic behaviors of Vietnam Railways.

Dynamic Analysis of Hydro-Turbine Governing System with Multistochastic Factors

2019 ◽  
Vol 14 (11) ◽  
Author(s):  
Jianling Li ◽  
Diyi Chen ◽  
Hao Zhang ◽  
Jing Liu
Keyword(s):  
Global Optimum ◽  
Stable Operation ◽  
Engineering System ◽  
Surge Tank ◽  
Negative Effects ◽  
Hydro Turbine ◽  
Governing System ◽  
Stochastic Characteristics ◽  
Stochastic Factor ◽  
The Stability

Abstract This paper explores the stability of a hydro-turbine governing system (HTGS) under simultaneous effects of multistochastic factors. Specifically, three different sets of stochastic factors are introduced into the governing system, and the corresponding mathematical model with multistochastic factors is proposed. Then, seven cases are performed to reveal the dynamic characteristics of the governing system, including the excitations of only single stochastic factor, two stochastic factors, and three stochastic factors with different combinations of stochastic parameters. The results show some interesting phenomena. First, the stability of the system is weakened by introducing stochastic variables ω2 and ω3 into the inlet pressure of hydro-turbine (h2) and the bottom pressure of the surge tank (h3) separately, or both. Second, the negative effects of the stochastic characteristics of h2 and h3 on the governing system are reduced by introducing the stochastic variable (ω1) into the hydro-turbine flow (q1), on the basis of fully considering the influence of the stochastic characteristics of h2 and h3. Third, stochastic factors are generally considered to be unfavorable, but it may help the system to reach a global optimum status under certain conditions, which break through the habit of empirical thinking. Finally, this work not only provides a new insight for stochastic phenomena existing in engineering system, but also lays a theoretical basis for the safe and stable operation of the hydropower stations.

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