Numerical Investigation on the Vibration of Steam Turbine Inlet Valves and the Feedback to the Dynamic Flow Field

2015 ◽  
Author(s):  
Clemens Bernhard Domnick ◽  
Friedrich-Karl Benra ◽  
Dieter Brillert ◽  
Hans Josef Dohmen ◽  
Christian Musch
Keyword(s):  
Steam Turbine ◽  
Structural Dynamics ◽  
Fluid Dynamic ◽  
Dynamic Flow ◽  
Piston Rings ◽  
Time Step ◽  
Structural Dynamic ◽  
Turbine Inlet ◽  
Valve Stem ◽  
Highly Nonlinear

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate in throttled operation a huge amount of energy. Due to that, high dynamic forces occur in the valve which can cause undesired valve vibrations. In this paper, the structural dynamics of a valve are analysed. The dynamic steam forces obtained by previous computational fluid dynamic (CFD) calculations at different operating points are impressed on the structural dynamic finite element model (FEM) of the valve. Due to frictional forces at the piston rings and contact effects at the bushings of the valve plug and the valve stem the structural dynamic FEM is highly nonlinear and has to be solved in the time domain. Prior to the actual investigation grid and time step studies are carried out. Also the effect of the temperature distribution within the valve stem is discussed and the influence of the valve actuator on the vibrations is analysed. In the first step, the vibrations generated by the fluid forces are investigated. The effects of the piston rings on the structural dynamics are discussed. It is found, that the piston rings are able to reduce the vibration significantly by frictional damping. In the second step, the effect of the moving valve plug on the dynamic flow in the valve is analysed. The time dependent displacement of the valve is transferred to CFD calculations using deformable meshes. With this one way coupling method the response of the flow to the vibrations is analysed.

Nonlinear Numerical Prediction of Gas Foil Bearing Stability and Unbalanced Response

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Sébastien Le Lez ◽  
Mihaï Arghir ◽  
Jean Frêne
Keyword(s):  
Dry Friction ◽  
Stability Limit ◽  
Time Step ◽  
Structural Dynamic ◽  
Friction Forces ◽  
Foil Bearings ◽  
Mass Unbalance ◽  
Foil Bearing ◽  
Highly Nonlinear ◽  
The Stability

One of the main interests of gas foil bearings lies in their superior rotordynamic characteristics compared with conventional bearings. A numerical investigation on the stability limit and on the unbalanced response of foil bearings is presented in this paper. The main difficulty in modeling the dynamic behavior of such bearings comes from the dry friction that occurs within the foil structure. Indeed, dry friction is highly nonlinear and is strongly influenced by the dynamic amplitude of the pressure field. To deal with these nonlinearities, a structural dynamic model has been developed in a previous work. This model considers the entire corrugated foil and the interactions between the bumps by describing the foil bearing structure as a multiple degrees of freedom system. It allows the determination of the dynamic friction forces at the top and at the bottom of the bumps by simple integration of ordinary differential equations. The dynamic displacements of the entire corrugated sheet are then easily obtained at each time step. The coupling between this structural model and a gas bearing prediction code is presented in this paper and allows performing full nonlinear analyses of a complete foil bearing. The bearing stability is the first investigated problem. The results show that the structural deflection enhances the stability of compliant surface bearings compared with rigid ones. Moreover, when friction is introduced, a new level of stability is reached, revealing the importance of this dissipation mechanism. The second investigated problem is the unbalanced response of foil bearings. The shaft trajectories depict a nonlinear jump in the response of both rigid and foil bearings when the value of the unbalance increases. Again, it is evidenced that the foil bearing can support higher mass unbalance before this undesirable step occurs.

Investigation on Flow Induced Vibrations of a Steam Turbine Inlet Valve Considering Fluid Structure Interaction Effects

2016 ◽  
Author(s):  
Clemens Bernhard Domnick ◽  
Friedrich-Karl Benra ◽  
Dieter Brillert ◽  
Hans Josef Dohmen ◽  
Christian Musch
Keyword(s):  
Steam Turbine ◽  
Structural Dynamics ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Element Model ◽  
Feedback Mechanism ◽  
Steam Turbines ◽  
Turbine Inlet ◽  
Flow Induced Vibrations ◽  
The One

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate a huge amount of energy in throttled operation. The dissipation process generates strong pressure fluctuations resulting in high dynamic forces causing valve vibrations. A brief survey of the literature dealing with valve vibrations reveals that vibrational problems and damages mostly occur in throttled operation when high speed jets, shocks, and shear layers are present. As previous investigations reveal that a feedback mechanism between the dynamic flow field and the vibrating valve plug exists, the vibrations are investigated with two-way coupled simulations. The fluid dynamics are solved with a scale-adaptive approach to resolve the pressure fluctuations generated by the turbulent flow. The finite element model solving the structural dynamics considers both frictional effects at the valve packing and contact effects caused by the plug impacting on the valve bushing. As different flow topologies causing diverse dynamic loads exist, the fluid flow and the structural dynamics are simulated at different operating points. The simulations show that differences to the one-way coupled approach exist leading to a change of the vibrational behavior. The physics behind the feedback mechanisms causing this change are analyzed and conclusions regarding the accuracy of the one-way coupled approach are drawn.

Investigation on Flow-Induced Vibrations of a Steam Turbine Inlet Valve Considering Fluid–Structure Interaction Effects

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Clemens Bernhard Domnick ◽  
Friedrich-Karl Benra ◽  
Dieter Brillert ◽  
Hans Josef Dohmen ◽  
Christian Musch
Keyword(s):  
Steam Turbine ◽  
Structural Dynamics ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Element Model ◽  
Feedback Mechanism ◽  
Steam Turbines ◽  
Turbine Inlet ◽  
Flow Induced Vibrations ◽  
The One

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate a huge amount of energy in throttled operation. The dissipation process generates strong pressure fluctuations resulting in high dynamic forces causing valve vibrations. A brief survey of the literature dealing with valve vibrations reveals that the vibrational problems and damages mostly occur in throttled operation when high speed jets, shocks, and shear layers are present. As previous investigations reveal that a feedback mechanism between the dynamic flow field and the vibrating valve plug exists, the vibrations are investigated with two-way coupled simulations. The fluid dynamics are solved with a scale-adaptive approach to resolve the pressure fluctuations generated by the turbulent flow. The finite element model (FEM) solving the structural dynamics considers both frictional effects at the valve packing and contact effects caused by the plug impacting on the valve bushing. As different flow topologies causing diverse dynamic loads exist, the fluid flow and the structural dynamics are simulated at different operating points. The simulations show that differences to the one-way-coupled approach exist leading to a change of the vibrational behavior. The physics behind the feedback mechanisms causing this change are analyzed and conclusions regarding the accuracy of the one-way-coupled approach are drawn.

An Efficient Computing Explicit Method for Structural Dynamics

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Shuenn-Yih Chang
Keyword(s):  
Structural Dynamics ◽  
Unconditional Stability ◽  
Explicit Methods ◽  
Explicit Method ◽  
Implicit Methods ◽  
Time Step ◽  
Integration Algorithm ◽  
Structural Dynamic ◽  
Linear Elastic ◽  
Linearized Stability

An integration algorithm, which integrates the most important advantage of explicit methods of the explicitness of each time step and that of implicit methods of the possibility of unconditional stability, is presented herein. This algorithm is analytically shown to be unconditionally stable for any linear elastic and nonlinear systems except for the instantaneous stiffness hardening systems with the instantaneous degree of nonlinearity larger than 43 based on a linearized stability analysis. Hence, its stability property is better than the previously published algorithm (Chang, 2007, “Improved Explicit Method for Structural Dynamics,” J. Eng. Mech., 133(7), pp. 748–760), which is only conditionally stable for instantaneous stiffness hardening systems although it also possesses unconditional stability for linear elastic and any instantaneous stiffness softening systems. Due to the explicitness of each time step, the possibility of unconditional stability, and comparable accuracy, the proposed algorithm is very promising for a general structural dynamic problem, where only the low frequency responses are of interest since it consumes much less computational efforts when compared with explicit methods, such as the Newmark explicit method, and implicit methods, such as the constant average acceleration method.

Numerical Analysis of the Unsteady Loads on a Steam Turbine Double Seat Control Valve

2014 ◽  
Author(s):  
Cosimo Bianchini ◽  
Riccardo Da Soghe ◽  
Lorenzo Cosi ◽  
Enzo Imparato
Keyword(s):  
Steam Turbine ◽  
Large Scale ◽  
Fluid Dynamic ◽  
Control Valve ◽  
Operating Conditions ◽  
Computational Time ◽  
Time Step ◽  
Frequency Spectra ◽  
Choked Flow ◽  
Seat Control

The continuously growing request for high operational flexibility also for large scale steam turbine creates new challenges for control valve design. Such components, subjected to large static loads, may also experience strong vibrations due to unsteady turbulent fluctuations downstream the throttling section, which need to be confined sufficiently far from structural natural frequencies in the entire range of operating conditions. This work is focused on a computational analysis of the unsteady steam flow developing within a realistic double-seat control valve employed in industrial steam turbine. Actual operating conditions are considered both in terms of steam inflow pressure and temperature, flow rates and plug height. Three plug heights were considered: two corresponding to almost closed plug thus subjected to choked flow, and the third verified at 4 different steam rates. In order to capture the unsteady nature of the flow and verify the fluid-dynamic forcing frequency, the Scale Adaptive Simulation principle, as implemented in Ansys® CFX 14.5 code, has been employed. Computations were run with a computational time step of 10−4 s and an effective simulation window of 0.2 s for time averaged values and pressure time signals. The unsteady response is monitored analyzing the frequency spectra of both integral variables (i.e. forces and moment on plug) and punctual pressure oscillations. Analysis of results showed that it is possible to correlate the principal frequency and amplitude with the operating conditions. Strouhal number based on plug diameter and bulk flow velocity remains in fact constant independently on operating conditions.

Numerical study of fluid dynamic flow within an internal combustion engine cylinder

2017 ◽  
Author(s):  
Ana Marta Souza ◽  
Antônio César Valadares de Oliveira ◽  
Enrico Temporim Ribeiro ◽  
Francisco Souza ◽  
Marcelo Colombo Chiari
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Internal Combustion ◽  
Dynamic Flow ◽  
Engine Cylinder

NUMERICAL SOLUTIONS OF 2D AND 3D SLAMMING PROBLEMS

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
Q Yang ◽  
W Qiu
Keyword(s):  
Free Surface ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Type Equation ◽  
The Body ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Highly Nonlinear ◽  
2D And 3D

Slamming forces on 2D and 3D bodies have been computed based on a CIP method. The highly nonlinear water entry problem governed by the Navier-Stokes equations was solved by a CIP based finite difference method on a fixed Cartesian grid. In the computation, a compact upwind scheme was employed for the advection calculations and a pressure-based algorithm was applied to treat the multiple phases. The free surface and the body boundaries were captured using density functions. For the pressure calculation, a Poisson-type equation was solved at each time step by the conjugate gradient iterative method. Validation studies were carried out for 2D wedges with various deadrise angles ranging from 0 to 60 degrees at constant vertical velocity. In the cases of wedges with small deadrise angles, the compressibility of air between the bottom of the wedge and the free surface was modelled. Studies were also extended to 3D bodies, such as a sphere, a cylinder and a catamaran, entering calm water. Computed pressures, free surface elevations and hydrodynamic forces were compared with experimental data and the numerical solutions by other methods.

Internal leakage analysis and experiment in hydraulic control system of steam turbine inlet valve

2020 ◽  
pp. 095440892097311
Author(s):  
Ying Liu ◽  
Qimin Wang ◽  
Xiaoxiao Li ◽  
Liming Wang
Keyword(s):  
Control System ◽  
Steam Turbine ◽  
Simulation Software ◽  
Hydraulic Control ◽  
Inlet Valve ◽  
Proportional Valve ◽  
Hydraulic Simulation ◽  
Turbine Inlet ◽  
Control Switch ◽  
Hydraulic Control System

In this paper, the transformation of steam turbine regulating system from mechanical hydraulic regulation to electro-hydraulic regulation is realized. And the internal leakage mechanism of the hydraulic control switch valve and the electro-hydraulic proportional valve in the system is analyzed. With the use of hydraulic simulation software AMESim, the mathematical model of the electro-hydraulic control system after transforming is established. The parameters of the hydraulic control switch valve and the electro-hydraulic proportional valve in the hydraulic control system of steam turbine inlet valve are studied under different internal leakage locations and different leakage degree, such as piston regulating time, steady position of piston, oil pressure and leakage flow flux. The fault characteristic table of internal leakage is obtained. An experimental platform for simulating internal leakage is built. The experimental curves of several physical quantities under different internal leakage conditions are obtained. The experimental results prove that the internal leakage has a great impact on the performance of the electro-hydraulic control system. The results of internal leakage experiment are consistent with those of internal leakage simulation.

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