Performance Evaluation of Gear Pump by 2D Unsteady CFD Analysis

2013 ◽  
Author(s):  
K. Anil Kumar ◽  
N. Balamuralikrishnan
Keyword(s):  
Mass Flow ◽  
Transient Flow ◽  
Flow Analysis ◽  
Adverse Pressure Gradient ◽  
Implant Design ◽  
Gear Pump ◽  
Time Step ◽  
Design Synthesis ◽  
Angular Velocities ◽  
Rotation Motion

Gas Turbine development activities have been associated with development of different pumps and its allied subsystems used for fuel supply and lubrication oil supply at different engine operating condition. 2D transient flow analysis of a Dual pump has been carried out in an environment with an adverse pressure gradient to map important parameters like pressure, velocity, mass flow and effect of slip. Three achievable close tolerances were selected and carried out the analysis. Finally identified tolerance to be maintained during manufacturing based on the analysis. A moving dynamic mesh concept was adopted because of its capability to facilitate solving transient flow problem and motion of the domain boundaries. A simulated motion control was decided based on the time step, angular velocities of gears rotation motion and coded through a User defined function (UDF) to give angular momentum. Each analysis was carried out for 180 degree of rotation. The main parameter mass flow rate was monitored for different speed and outlet pressures. A validation experimental test was carried out at one rpm thus build up a confidence in implant design synthesis to meet challenges in future.

Three-Dimensional Unsteady Simulation in a Water Turbine

2013 ◽  
Vol 655-657 ◽  
pp. 227-230
Author(s):  
Ying Hu ◽  
Kun Wang
Keyword(s):  
Turbulent Flow ◽  
Transient Flow ◽  
Flow Analysis ◽  
Flow Fields ◽  
Francis Turbine ◽  
Optimum Operating ◽  
Time Step ◽  
Optimum Operating Condition ◽  
Water Turbine ◽  
Turbine Model

This paper introduces the 3D numerical simulation of unsteady turbulent flow in the entire flow passage of a water turbine model with CFD technology. A new and available method for the design of a Francis turbine has been explored. The boundary conditions have been implemented based on the 3D averaged N-S equations. The governing equations are discreted on space by the finite volume method and on time step by the finite difference method. The 3D unsteady turbulent flow in an entire Francis turbine model is calculated successfully using the CFX-TASCflow software and RNG k-εturbulence model. Transient flow fields are simulated in the spiral case, the distributor, the runner and the draft tube. It is presented in this paper that the computer simulation of the flow fields in components of the Francis turbine at the optimum operating condition. Meanwhile, the velocity and pressure at any points in the flow fields can be obtained so as to provide the great value on the performance prediction. According to the simulating results, the flow analysis and the design experience, the design of components in a Francis turbine model can be improved and optimized. In this way, designers may decrease numbers of test and shorten the period for a model. Therefore, the cost of research and produce can be reduced.

A Numerical Study of BWR Steam Separator

2002 ◽  
Author(s):  
Haruo Terasaka ◽  
Sensuke Shimizu
Keyword(s):  
Transient Flow ◽  
Numerical Study ◽  
Fluid Model ◽  
Flow Analysis ◽  
Phase Flow ◽  
Step Size ◽  
Time Step ◽  
Two Phase ◽  
Time Step Size ◽  
Steam Separator

An advanced numerical method based on two-fluid model of two-phase flow has been developed to simulate the swirling gas-liquid flow and the phase separation process in a Boiling Water Reactor separator. The goal is to correctly predict the performance of operating steam separator as well as new designs. The solution method present here is an extension of SIMPLEST scheme, a fully implicit scheme for single-phase flow analysis. It is robust and unconditionally stable, therefore enable us to use very large time step size. This feature is suitable for steady and/or slow transient flow analyses. Furthermore, it enhances numerical stability during rapid transient calculations. By employing this method, separator hydrodynamics around swirler were calculated.

A Numerical Simulation of Swirling Two-Phase Flow in BWR Steam-Water Separator and Its Optimization

2003 ◽  
Author(s):  
Haruo Terasaka ◽  
Sensuke Shimizu ◽  
Minoru Kawahara
Keyword(s):  
Transient Flow ◽  
Fluid Model ◽  
Flow Analysis ◽  
Phase Flow ◽  
Step Size ◽  
Time Step ◽  
Two Phase ◽  
Time Step Size ◽  
Fully Implicit ◽  
Water Separator

An advanced numerical method based on the two-fluid model has been developed. The solution method presented here is an extension of the SIMPLEST scheme, a fully implicit scheme for single-phase flow analysis. It is robust and unconditionally stable, and therefore it enables us to use a very large time step size. This feature is suitable for steady and/or slow transient flow analyses. Furthermore, it enhances numerical stability during rapid transient calculations. By using this method, swirling gas-liquid flow in a steam-water separator of Boiling Water Reactors (BWRs) was calculated and the hydrodynamics characteristics were investigated for optimization.

Nonisothermal Transient Flow in Natural Gas Pipeline

2008 ◽  
Vol 75 (3) ◽  
Author(s):  
M. Abbaspour ◽  
K. S. Chapman
Keyword(s):  
Gas Flow ◽  
Transient Flow ◽  
Flow Analysis ◽  
Compressibility Factor ◽  
Momentum Equation ◽  
Gas Pipeline ◽  
Time Step ◽  
Inertia Term ◽  
Fully Implicit ◽  
Energy Equations

The fully implicit finite-difference method is used to solve the continuity, momentum, and energy equations for flow within a gas pipeline. This methodology (1) incorporates the convective inertia term in the conservation of momentum equation, (2) treats the compressibility factor as a function of temperature and pressure, and (3) considers the friction factor as a function of the Reynolds number and pipe roughness. The fully implicit method representation of the equations offers the advantage of guaranteed stability for a large time step, which is very useful for gas pipeline industry. The results show that the effect of treating the gas in a nonisothermal manner is extremely necessary for pipeline flow calculation accuracies, especially for rapid transient process. It also indicates that the convective inertia term plays an important role in the gas flow analysis and cannot be neglected from the calculation.

Critical comparison of the different versions of the OpenFOAM on the simulation of spillway

2021 ◽  
pp. 44-57
Author(s):  
Абдикерим Ырысбаевич Курбаналиев ◽  
Бурулгул Рахманбердиевна Ойчуева ◽  
Анипа Ташбаевна Калмурзаева ◽  
Аманбек Жайнакович Жайнаков ◽  
Топчубай Чокоевич Култаев
Keyword(s):  
Mass Flow ◽  
Transient Flow ◽  
Time Derivative ◽  
Numerical Calculations ◽  
Local Dynamic ◽  
Time Step ◽  
Two Phase ◽  
Current Time ◽  
Previous Time ◽  
Previous Time Step

Приведены предварительные результаты численного моделирования двухфазного течения двух несжимаемых и несмешивающихся жидкостей через водослив трапециевидной формы. Целью работы была демонстрация возможностей решателя interFoam различных версий открытого пакета OpenFoam при моделировании рассматриваемого класса течений. Численные расчеты проведены с использованием входящего в состав OpenFoam руководства weirOverFlow. В пакете OpenFOAM6 коэффициент fvcDdtPhiCoeff для вычисления потоков массы на гранях ячеек изменен в целях улучшения устойчивости/точности и исключения осцилляций давления при высоких числах Куранта. Он вычисляется с использованием значений плотности и потока массы с предыдущего временн´ого шага. Результаты численных расчетов показывают, что такие изменения вызывают чрезмерно быстрый переход от нестационарного течения к стационарному. The results of numerical simulation for a two-phase flow of two incompressible and immiscible liquids through a trapezoidal spillway are presented. To simulate the free boundary, we used the method of fluid volume. The aim of the work was to demonstrate the capabilities of the various versions of interFoam solver of the OpenFOAM package for modelling the considered class of flows. Numerical calculations were performed using the OpenFOAM weirOverFlow tutorial. In order to improve the consistency, usability, flexibility and ease of modifying the interFoam solver, the existing interDyMFoam solver with the local dynamic mesh adaptation function was combined with the interFoam solver with a static computational mesh. In addition, in the OpenFOAM6 package, the fvcDdtPhiCoeff coefficient used for calculating the time derivative and taking into account the Rhie- Chow correction on the collocated grid for calculating mass fluxes on the cell faces was changed in order to improve stability/accuracy and eliminate pressure oscillations at high Courant numbers. The calculation of fvcDdtPhiCoeff coefficient in OpenFOAM5 requires the density value from the current time step along with the mass flow value from the previous time step, while in OpenFOAM6, both density and mass flow values are taken from the previous time step for calculation of the fvcDdtPhiCoeff coefficient. The results of numerical calculations of the OpenFOAM6 package show that such changes lead to an excessively fast transition of the transient flow to the stationary one in comparison with other versions of the OpenFOAM package.

A new dynamic mesh algorithm for studying the 3D transient flow field of tilting pad journal bearings

2016 ◽  
Vol 230 (12) ◽  
pp. 1470-1482 ◽  
Author(s):  
Mengxuan Li ◽  
Chaohua Gu ◽  
Xiaohong Pan ◽  
Shuiying Zheng ◽  
Qiang Li
Keyword(s):  
Flow Field ◽  
Equilibrium Position ◽  
Transient Flow ◽  
Journal Bearings ◽  
Dynamic Mesh ◽  
Static Equilibrium ◽  
Time Step ◽  
Tilting Pad ◽  
Grid Nodes ◽  
Tilting Pad Journal Bearings

A new dynamic mesh algorithm is developed in this paper to realize the three-dimensional (3D) computational fluid dynamics (CFD) method for studying the small clearance transient flow field of tilting pad journal bearings (TPJBs). It is based on a structured grid, ensuring that the total number and the topology relationship of the grid nodes remain unchanged during the dynamic mesh updating process. The displacements of the grid nodes can be precisely recalculated at every time step. The updated mesh maintains high quality and is suitable for transient calculation of large journal displacement in FLUENT. The calculation results, such as the static equilibrium position and the dynamic characteristic coefficients, are consistent with the two-dimensional (2D) solution of the Reynolds equation. Furthermore, in the process of transient analysis, under conditions in which the journal is away from the static equilibrium position, evident differences appear between linearized and transient oil film forces, indicating that the nonlinear transient calculation is more suitable for studying the rotor-bearing system.

Time suboptimal control of industrial manipulators along specified paths while keeping an end-effector orientation unchanged

Robotica ◽  
2003 ◽  
Vol 21 (2) ◽  
pp. 153-161 ◽  
Author(s):  
S. Kilicaslan ◽  
Y. Ercan
Keyword(s):  
Suboptimal Control ◽  
Time Step ◽  
End Effector ◽  
Industrial Manipulator ◽  
Industrial Manipulators ◽  
Angular Velocities ◽  
System Equations ◽  
Six Degree Of Freedom ◽  
Time Suboptimal Control

A method for the time suboptimal control of an industrial manipulator that moves along a specified path while keeping its end-effector orientation unchanged is proposed. Nonlinear system equations that describe the manipulator motion are linearized at each time step along the path. A method which gives control inputs (joint angular velocities) for time suboptimal control of the manipulator is developed. In the formulation, joint angular velocity and acceleration limitations are also taken into consideration. A six degree of freedom elbow type manipulator is used in a case study to verify the method developed.

Dynamic Optimization of an Evaporator by a Nonlinear Model Predictive Controller for Operation at Modular Micro Rectification

2009 ◽  
Author(s):  
Ralf Knauss ◽  
Lukas E. Wiesegger ◽  
Rolf Marr ◽  
Ju¨rgen J. Brandner
Keyword(s):  
Mass Flow ◽  
Dynamic Optimization ◽  
Nonlinear Model ◽  
Process Models ◽  
Maximum Efficiency ◽  
Local Optimum ◽  
Outlet Temperature ◽  
Time Step ◽  
Unit Operations ◽  
Vapor Fraction

Arranging micro-structured equipment to plants whole production processes can be realized with maximum efficiency in tightest space. Unit operations are thereby represented as individual functional modules in shape of micro devices. In a multi unit operation plant a correspondingly large number of manipulable variables have to be coordinated. Due to the design of micro-scaled devices plants form sophisticated systems, while for a fully optimized control still no common satisfying solutions exist. A system of modular, discontinuous phase contacting, micro rectification consists of unit operations heating, cooling, mixing and separating. Heat exchangers, mixers and cyclones for phase separation can be arranged to a counter-current rectification system with maximum mass-transfer efficiency every unit. Operating an electrical heated evaporator for modular rectification purposes a strong coupling of mass flow with the vapor fraction and the outlet temperature can be observed [4]. Operating at a predefined state for mass flow, temperature and vapor fraction may only be possible with difficulties using traditional methods of linear control technology. For dynamic optimization of the multivariable micro-structured evaporator principle of Nonlinear Model Predictive Control (NMPC) was generically formulated in C++ and implemented to LABVIEW 7. Every discrete time step an objective function is generated from nonlinear process models in the form of grouped NARX-polynomials. Optimal sequences of control actions for plant operation are evolved. The resulting constrained cost function is non-convex making detection of relative local optimum a difficult task. This obstacle can be gone around using heuristic optimization algorithm in combination with traditional techniques. Based on experimental results it was demonstrated that NMPC keeps the coupled variables mass flow and temperature energy saving with minimal control activity in the entire two-phase region on their set-points.

Autostoichiometric vapor deposition: Part I. Theory

1995 ◽  
Vol 10 (10) ◽  
pp. 2536-2541 ◽  
Author(s):  
Ren Xu
Keyword(s):  
Mass Flow ◽  
Vapor Deposition ◽  
Flow Analysis ◽  
Quantitative Measure ◽  
Low Pressure ◽  
Potential Candidate ◽  
Organic Complexes ◽  
Reaction Schemes

The possibility of an autostoichiometric vapor deposition is explored. Heterometal-organic complexes such as double alkoxides are potential candidate precursors for such deposition. Two reaction schemes, the hydrolysis-assisted pyrolysis and the hydrolysis-polycondensation of double alkoxides, are identified to be autostoichiometric reactions. A simple low-pressure apparatus is suggested for autostoichiometric vapor deposition. Mass-flow analysis allows for the identification of a nonstoichiometry factor K which can be used as a quantitative measure of the precursor's autostoichiometric capability.

scholarly journals Investigation of Air Pocket Behavior in Pipelines Using Rigid Column Model and Contributions of Time Integration Schemes

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 785
Author(s):  
Arman Rokhzadi ◽  
Musandji Fuamba
Keyword(s):  
Transient Flow ◽  
Time Integration ◽  
Driving Pressure ◽  
Implicit Time ◽  
Numerical Dissipation ◽  
Integration Scheme ◽  
Time Step ◽  
Column Model ◽  
Integration Schemes ◽  
Backward Euler

This paper studies the air pressurization problem caused by a partially pressurized transient flow in a reservoir-pipe system. The purpose of this study is to analyze the performance of the rigid column model in predicting the attenuation of the air pressure distribution. In this regard, an analytic formula for the amplitude and frequency will be derived, in which the influential parameters, particularly, the driving pressure and the air and water lengths, on the damping can be seen. The direct effect of the driving pressure and inverse effect of the product of the air and water lengths on the damping will be numerically examined. In addition, these numerical observations will be examined by solving different test cases and by comparing to available experimental data to show that the rigid column model is able to predict the damping. However, due to simplified assumptions associated with the rigid column model, the energy dissipation, as well as the damping, is underestimated. In this regard, using the backward Euler implicit time integration scheme, instead of the classical fourth order explicit Runge–Kutta scheme, will be proposed so that the numerical dissipation of the backward Euler implicit scheme represents the physical dissipation. In addition, a formula will be derived to calculate the appropriate time step size, by which the dissipation of the heat transfer can be compensated.

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