A Theoretical Model for Self-Excited Vibrations in Hydraulic Gates, Valves and Seals

1980 ◽  
Vol 102 (2) ◽  
pp. 146-151 ◽  
Author(s):  
D. S. Weaver ◽  
S. Ziada
Keyword(s):  
Theoretical Model ◽  
Discharge Coefficient ◽  
Nonlinear Differential Equations ◽  
Check Valve ◽  
Structural Stiffness ◽  
Fluid Inertia ◽  
Vibration Displacement ◽  
Runge Kutta Method ◽  
Flow Control Devices ◽  
Control Devices

A general theoretical model is presented for the jet flow mechanism of self-excited vibrations of flow control devices operating at small openings. The coupled nonlinear differential equations are solved numerically using the Runge-Kutta method. The vibration displacement and discharge characteristics are given for a variety of parameters such as structural stiffness, fluid inertia and discharge coefficient. The predictions are shown to agree reasonably well with the experimental observations of swing check valve vibrations.

Flow Induced Vibrations of a Hydraulic Valve and Their Elimination

1978 ◽  
Vol 100 (2) ◽  
pp. 239-245 ◽  
Author(s):  
D. S. Weaver ◽  
F. A. Adubi ◽  
N. Kouwen
Keyword(s):  
Check Valve ◽  
Rate Of Change ◽  
High Rate ◽  
Fluid Inertia ◽  
Dimensional Model ◽  
Flow Control Devices ◽  
Flow Induced Vibrations ◽  
Valve Opening ◽  
Control Devices ◽  
Hydraulic Valve

The flow induced vibrations of a check valve with a spring damper to prevent slamming have been studied experimentally. Both prototype and two-dimensional model experiments were conducted to develop an understanding of the mechanism of self-excitation. The phenomenon is shown to be caused by the high rate of change of discharge at small angles of valve opening and the hysteretic hydrodynamic loading resulting from fluid inertia. As the discharge-displacement characteristics of the valve are dependent on its geometry, modifications of this geometry were examined and one found which eliminated the vibrations entirely. The phenomenon studied is considered to be the same as that causing vibrations in numerous other flow control devices when operating at small openings.

scholarly journals New Insight on Liquid Steel Microalloying by Pulse-Step Method in Two-Strand Slab Tundish by Numerical Simulations

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 448
Author(s):  
Adam Cwudziński
Keyword(s):  
Liquid Steel ◽  
Mixing Time ◽  
Casting Process ◽  
Step Method ◽  
Flow Control Devices ◽  
Alloy Addition ◽  
Interesting Approach ◽  
Control Devices ◽  
Steel Flow ◽  
Alloy Concentration

Developing a technology for introducing alloy addition to liquid steel during the course of continuous casting process seems to be an interesting approach to enhancing the steelmaking process, especially as the effective introduction of micro-additives or non-metallic inclusion modifiers to the liquid steel is the key to the production of the highest-quality steel. This paper presents the results of investigation describing the process of liquid steel chemical homogenisation in the two-strand slab tundish. The alloy was fed to liquid steel by pulse-step method. Five tundish equipment variants with different flow control devices and alloy addition feeding positions were considered. The paper includes fields of liquid steel flow, alloy concentration vs. time curves, dimensionless mixing time, minimum time values and alloy concentration deviations at tundish outlets. The results pointed much more effectively with liquid steel mixing nickel than aluminium. For aluminium obtaining a 95% chemical homogenisation level requires three-fold more time. Moreover, it is definitely beneficial for chemical homogenisation to initiate the alloying process simultaneously in two sites. This procedure generates, among others, the least alloy deviation of concentration at tundish outlets.

scholarly journals Prediction of flow-control devices' noise with modified acoustic perturbation equations

2020 ◽  
Vol 22 (3) ◽  
pp. 619-627
Author(s):  
Luca Fenini ◽  
Stefano Malavasi
Keyword(s):  
Flow Control ◽  
Fluid Dynamic ◽  
International Standards ◽  
The Other ◽  
Computational Time ◽  
Noise Prediction ◽  
Acoustic Perturbation ◽  
Flow Control Devices ◽  
Control Devices ◽  
Perturbation Equations

Abstract Fluid-dynamic noise emissions produced by flow-control devices inside ducts are a concerning issue for valve manufacturers and pipeline management. This work proposes a modified formulation of Acoustic Perturbation Equations (APE) that is applicable to industrial frameworks where the interest is addressed to noise prediction according to international standards. This formulation is derived from a literature APE system removing two terms allowing for a computational time reduction of about 20%. The physical contribution of the removed terms is discussed according to the literature. The modified APE are applied to the prediction of the noise emitted by an orifice. The reliability of the new APE system is evaluated by comparing the Sound Pressure Level (SPL) and the acoustic pressure with the ones returned by LES and literature APE. The new formulation agrees with the other methods far from the orifice: moving over nine diameters downstream of the trailing edge, the SPL is in accordance with the other models. Since international standards characterize control devices with the noise measured 1 m downstream of them, the modified APE formulation provides reliable and faster noise prediction for those devices with outlet diameter, d, such that 9d < 1 m.

Transient Calculation of Electric Power Circuits with Special Reference to Magnetizing Nonlinearity

2016 ◽  
Vol 25 (06) ◽  
pp. 1650054
Author(s):  
Xiaoqin Zhang
Keyword(s):  
Electric Power ◽  
Nonlinear Differential Equations ◽  
Linear Part ◽  
Realistic Model ◽  
Power Circuit ◽  
Runge Kutta Method ◽  
Proposed Model ◽  
Power Circuits ◽  
Set Up ◽  
Reduced Scale

This paper proposes a realistic model of magnetizing branches for transient calculation of electric power circuits. The model represents the nonlinear relationship between flux linkage and exciting current of magnetizing branches with a major loop and a family of minor loop trajectories, which has the capability of simulating the multi-valued hysteresis behavior. By applying the proposed model to transient calculation, an efficient algorithm is developed for obtaining the transient responses in electric power circuits. In the algorithm, the electric power circuit is divided into the magnetizing branches and the remaining linear part. The nonlinear differential equations are set up for the magnetizing branches and solved by the semi-explicit Runge–Kutta method. The transient calculation for the remaining linear part is performed on the basis of the solution to the magnetizing branches. Then, a laboratory measurement is made with a reduced-scale experimental arrangement. The measured results are compared with the calculated ones and a reasonable agreement is shown between them.

The Application of Shape Memory Alloy as Vortex Generators and Flow Control Devices for Enhanced Convective Heat Transfer

2007 ◽  
Author(s):  
Mohd. S. Aris ◽  
Ieuan Owen ◽  
Chris. J. Sutcliffe
Keyword(s):  
Heat Transfer ◽  
Flow Control ◽  
Shape Memory ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Flow Control Devices ◽  
Control Devices

This paper is concerned with convective heat transfer enhancement of heated surfaces through the use of vortex generators and flow control devices. A preliminary proof-of-concept investigation has been carried out into the use of active vortex generators and flow control elements, both manufactured from Shape Memory Alloys (SMAs) which are activated at set temperatures. The vortex generators change their shape to intrude further into the flow at high temperature to enhance heat transfer, while they maintain a low profile at low temperatures to minimise flow pressure losses. One set of vortex generators was made from pre-alloyed powders of SMA material in an advanced rapid prototyping process known as Selective Laser Melting (SLM). Another set of devices was also made from commercially available flat annealed thin SMA sheets for comparison purposes. The flow control elements are devices that preferentially guide the flow to heated parts of a surface, again using temperature-activated SMAs. Promising results were obtained for both the vortex generator and flow control device when their temperatures were varied from 20° to 85°C. The vortex generators responded by increasing their angle of attack from 20° to 35° while the wavy flow control elements straightened out at higher temperatures. As the designs were two-way trained, they regain their initial position and shape at a lower temperature. The surface temperature of the heated plate on which the active devices were positioned reduced between 8 to 51%, indicating heat transfer enhancement due to the generated vortices and changes in air flow rates.

A Mathematical Model to Predict Solvent/Steam Flashing in Pure Solvent or Solvent/Steam Coinjection in Horizontal Producers

2021 ◽  
Author(s):  
Mazda Irani ◽  
Nasser Sabet ◽  
Farzad Bashtani ◽  
Kousha Gohari
Keyword(s):  
Flow Control ◽  
Latent Heat ◽  
Relative Permeability ◽  
Recovery Process ◽  
Liquid Pool ◽  
Solvent Injection ◽  
Recovery Processes ◽  
Flow Control Devices ◽  
Pure Solvent ◽  
Control Devices

Summary Although the steam assisted gravity drainage (SAGD) process is still the preferred thermal-recovery process method for Athabascan deposits in Alberta, Canada, the interest in solvent-based techniques is growing due to reduce greenhouse-gas (GHG) emissions and water treatment concerns. In SAGD process, the thermodynamic trapping or subcool trapping is quite efficient due to strongly dependency of bitumen viscosity to temperature. As Irani (2018) discussed subcool trapping for solvent applications such NsolvTM recovery process is inefficient due to week dependency of solvent viscosity to temperature. Other factor that effects the efficiency of the thermodynamic trapping is that the pure solvent injection recovery processes are operated at low pressure and it is not large temperature window for operators to apply large subcools. Such challenges make the pure solvent injection recovery processes a perfect case for deployment of Flow-Control-Devices (FCDs). FCDs have demonstrated significant potential for improving recovery in SAGD production wells. FCD experience in SAGD has been primarily positive and most producers performed better with FCDs. Application of FCDs are even more important in pure-solvent injection recovery processes due to large amount of solvent in the liquid pool and also low latent heat of solvent in comparison of water. With FCDs, the draw-down pressure is typically higher, resulting in flashing near the well bore, which is largely correlated to latent heat of the main fluid in the liquid pool. The flashing creates either steam or vapour breakthrough that causes the reduction in the relative permeability of the liquid phase. Such mobility reduction creates new equilibrium that stabilizes at lower rates. Such new equilibrium analysis is conducted by forcing a new temperature gradient to the model. Such condition creates an environment that leads into extensive solvent-breakthrough called solvent-coning in this study. The main output of such analysis is the produced solvent gas-fraction produced at the sand-face. The gas-fraction is an important input for the flow control devices (FCDs) especially at subcools close to the zero, as it controls its behavior. EoS model is also created and simplified to be possible to used in defining different equilibrium conditions. This type of analysis can help the operators evaluate the effectiveness of different type of FCDs, whether they are primarily momentum- or friction-style devices for application of the pure solvent injection recovery processes. This study is the first of its kind that couple the EoS and Darcy flow in the liquid pool. The model includes all the factors into a liquid-relative-permeability, and limitation of the liquid flow into producer is modeled by Darcy flow and reduction of such relative-permeability.

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