CFD Simulations and Experiments of Flow Fluctuations Around a Steam Control Valve

2006 ◽  
Vol 129 (1) ◽  
pp. 48-54 ◽  
Author(s):  
Ryo Morita ◽  
Fumio Inada ◽  
Michitsugu Mori ◽  
Kenichi Tezuka ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Three Dimensional ◽  
Control Valve ◽  
Piping System ◽  
Cfd Simulations ◽  
Valve Body ◽  
Side Load ◽  
Flow Fluctuations ◽  
Partial Opening ◽  
Attached Flow ◽  
High Pressure Region

Under certain opening conditions (partial opening) of a steam control valve, the piping system in a power plant occasionally experiences large vibrations. To understand the valve instability that is responsible for such vibrations, detailed experiments and CFD calculations were performed. As a result of these investigations, it was found that under the middle-opening (partial opening) condition, a complex three-dimensional (3D) flow structure (valve-attached flow) sets up in the valve region leading to a high pressure region on a part of the valve body. As this region rotates circumferentially, it causes a cyclic asymmetric side load on the valve body, which is considered to be the cause of the vibrations.

Flow Induced Vibration of a Steam Control Valve in Middle-Opening Condition

2005 ◽  
Author(s):  
Ryo Morita ◽  
Fumio Inada ◽  
Michitsugu Mori ◽  
Kenichi Tezuka ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Pressure Fluctuation ◽  
3D Structure ◽  
Flow Characteristics ◽  
Control Valve ◽  
Piping System ◽  
Flow Induced Vibration ◽  
Valve Body ◽  
Weak Support ◽  
Side Load ◽  
Attached Flow

In some cases, a steam control valve in a power plant causes a large vibration of the piping system under partial valve opening. For rationalization of maintenance and management of a plant, it is favorable to optimize the valve geometry to prevent such vibration. However, it is difficult to understand the flow characteristics in detail only from experiments because the flow around a valve has a complex 3D structure and becomes supersonic (M>1). Therefore, it is useful to combine experiments and CFD (Computational Fluid Dynamics) for the clarification of the cause of vibration and optimization of valve geometry. In previous researches involving experiment and CFD calculation using “MATIS” code, we found that an asymmetric flow attached to the valve body (named “valve-attached flow”) occurs and pressure increases where the valve-attached flow collides with the flow from the opposite side under the middle opening condition. This high-pressure region rotates circumferentially (named “rotating pressure fluctuation”) and causes cyclic side load on the valve body. However, because we assumed the valve support is rigid, we cannot clarify the interaction between the rotating pressure fluctuation and the valve vibration when the valve stiffness is small. Thus, in this paper, we conducted flow-induced vibration experiments on a valve with a very weak support and investigated the characteristics of the vibration mode under the middle-opening condition. As a result, under the specific lift condition of the region where rotating pressure fluctuation occurs, lock-in phenomena between the rotating pressure fluctuation and the valve vibration occur and large-amplitude vibration can be seen.

Acoustic Fatigue of a Steam Dump Pipe System Excited by Valve Noise

2001 ◽  
Vol 123 (4) ◽  
pp. 461-468 ◽  
Author(s):  
Suzanne Michaud ◽  
Samir Ziada ◽  
Henri Pastorel
Keyword(s):  
Control Valve ◽  
Primary Source ◽  
Scale Model ◽  
Dynamic Strain ◽  
Small Scale ◽  
Piping System ◽  
Frequency Noise ◽  
Valve Body ◽  
Pipe System ◽  
Valve Stem

The steam dump system in Gentilly Nuclear Power Plant consists of four parallel steam pipes, each of which comprises a steam control valve. Two pipes of this system experienced high-cycle fatigue damage. In-situ vibration and dynamic strain measurements were therefore conducted to identify the cause of the damage and formulate suitable counter-measures. The test results pointed to the high-frequency noise of the valve as the primary source causing the fatigue failure. By means of small-scale model tests, using a compressed air network, a new valve stem was developed, which produces a substantially lower noise level than that generated by the original valve stem. Implementing this new stem in the plant, without any other modifications in the valve body or the piping system, significantly reduced the dynamic stresses of the piping, but increased the vibration level of the valve itself. An alternative valve stem, which is a simpler version of the new design, was therefore tested and found to reduce the pipe stresses sufficiently while not increasing the level of valve vibration.

Performance enhancement of Savonius wind turbine by blade shape and twisted angle modifications

2021 ◽  
pp. 095765092098794
Author(s):  
Ahmed M Nagib Elmekawy ◽  
Hassan A Hassan Saeed ◽  
Sadek Z Kassab
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Cfd Simulations ◽  
Sliding Mesh ◽  
Blade Shape ◽  
Rotor Shape ◽  
Twisting Angle

Three-dimensional CFD simulations are carried out to study the increase of power generated from Savonius vertical axis wind turbines by modifying the blade shape and blade angel of twist. Twisting angle of the classical blade are varied and several proposed novel blade shapes are introduced to enhance the performance of the wind turbine. CFD simulations have been performed using sliding mesh technique of ANSYS software. Four turbulence models; realizable k -[Formula: see text], standard k - [Formula: see text], SST transition and SST k -[Formula: see text] are utilized in the simulations. The blade twisting angle has been modified for the proposed dimensions and wind speed. The introduced novel blade increased the power generated compared to the classical shapes. The two proposed novel blades achieved better power coefficients. One of the proposed models achieved an increase of 31% and the other one achieved 32.2% when compared to the classical rotor shape. The optimum twist angel for the two proposed models achieved 5.66% and 5.69% when compared with zero angle of twist.

scholarly journals Radial Turbine Design for Solar Chimney Power Plants

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 674
Author(s):  
Paul Caicedo ◽  
David Wood ◽  
Craig Johansen
Keyword(s):  
Power Plants ◽  
Reference Frames ◽  
Three Dimensional ◽  
Discrete Ordinates ◽  
Large Area ◽  
Solar Chimney ◽  
Cfd Simulations ◽  
Radial Turbine ◽  
Design Changes ◽  
Turbine Design

Solar chimney power plants (SCPPs) collect air heated over a large area on the ground and exhaust it through a turbine or turbines located near the base of a tall chimney to produce renewable electricity. SCPP design in practice is likely to be specific to the site and of variable size, both of which require a purpose-built turbine. If SCPP turbines cannot be mass produced, unlike wind turbines, for example, they should be as cheap as possible to manufacture as their design changes. It is argued that a radial inflow turbine with blades made from metal sheets, or similar material, is likely to achieve this objective. This turbine type has not previously been considered for SCPPs. This article presents the design of a radial turbine to be placed hypothetically at the bottom of the Manzanares SCPP, the only large prototype to be built. Three-dimensional computational fluid dynamics (CFD) simulations were used to assess the turbine’s performance when installed in the SCPP. Multiple reference frames with the renormalization group k-ε turbulence model, and a discrete ordinates non-gray radiation model were used in the CFD simulations. Three radial turbines were designed and simulated. The largest power output was 77.7 kW at a shaft speed of 15 rpm for a solar radiation of 850 W/m2 which exceeds by more than 40 kW the original axial turbine used in Manzanares. Further, the efficiency of this turbine matches the highest efficiency of competing turbine designs in the literature.

scholarly journals Contribution of upper airway geometry to convective mixing

2008 ◽  
Vol 105 (6) ◽  
pp. 1733-1740 ◽  
Author(s):  
Santhosh T. Jayaraju ◽  
Manuel Paiva ◽  
Mark Brouns ◽  
Chris Lacor ◽  
Sylvia Verbanck
Keyword(s):  
Three Dimensional ◽  
Upper Airway ◽  
Axial Dispersion ◽  
Half Width ◽  
Experimental Results ◽  
Cfd Simulations ◽  
Flow Rates ◽  
Axial Dispersion Coefficient ◽  
Dispersive Effect ◽  
Flow Directions

We investigated the axial dispersive effect of the upper airway structure (comprising mouth cavity, oropharynx, and trachea) on a traversing aerosol bolus. This was done by means of aerosol bolus experiments on a hollow cast of a realistic upper airway model (UAM) and three-dimensional computational fluid dynamics (CFD) simulations in the same UAM geometry. The experiments showed that 50-ml boluses injected into the UAM dispersed to boluses with a half-width ranging from 80 to 90 ml at the UAM exit, across both flow rates (250, 500 ml/s) and both flow directions (inspiration, expiration). These experimental results imply that the net half-width induced by the UAM typically was 69 ml. Comparison of experimental bolus traces with a one-dimensional Gaussian-derived analytical solution resulted in an axial dispersion coefficient of 200–250 cm2/s, depending on whether the bolus peak and its half-width or the bolus tail needed to be fully accounted for. CFD simulations agreed well with experimental results for inspiratory boluses and were compatible with an axial dispersion of 200 cm2/s. However, for expiratory boluses the CFD simulations showed a very tight bolus peak followed by an elongated tail, in sharp contrast to the expiratory bolus experiments. This indicates that CFD methods that are widely used to predict the fate of aerosols in the human upper airway, where flow is transitional, need to be critically assessed, possibly via aerosol bolus simulations. We conclude that, with all its geometric complexity, the upper airway introduces a relatively mild dispersion on a traversing aerosol bolus for normal breathing flow rates in inspiratory and expiratory flow directions.

Numerical Simulation of Emergency Release of Liquid Petroleum Gas on a Car Gas Station

2021 ◽  
Vol 23 ◽  
pp. 65-77
Author(s):  
Zdzislaw Salamonowicz ◽  
Malgorzata Majder-Lopatka ◽  
Anna Dmochowska ◽  
Aleksandra Piechota-Polanczyk ◽  
Andrzej Polanczyk
Keyword(s):  
Liquid Surface ◽  
Atmospheric Stability ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Liquid Form ◽  
Cfd Simulations ◽  
Danger Zone ◽  
Liquid Petroleum Gas ◽  
Gas Station ◽  
Hazardous Zone

LPG storage tanks may be seriously threatened by a fire coming from nearby fuels or by leakage appearance. The aim of the study was to prepare a three-dimensional model of LPG release on a car gas station under different environmental conditions. CFD simulations of liquid and gas phase release from a tank localized on a car gas station was performed. First, ALOHA software was applied to determine mass flow rate, while Ansys software was used to determine the shape and size of hazardous zone. To reflect real condition atmospheric stability classes were applied. It was observed that for classes A-D the hazardous zone was decreasing. While, for E and F class the range was increased. It was noticed that the location of the leakage affects the extent of the danger zone. For the leaking below the liquid surface analyzed LPG has liquid form. While, for the leaking above the liquid surface analyzed LPG has gas form. Furthermore, for liquid leakage the largest hazard zone of release was observed.

Experimental Investigation of Vibrational and Acoustic Phenomena for Detecting the Stall and Surge of a Multistage Compressor

2017 ◽  
Author(s):  
Enrico Munari ◽  
Gianluca D’Elia ◽  
Mirko Morini ◽  
Emiliano Mucchi ◽  
Michele Pinelli ◽  
...  
Keyword(s):  
Acoustic Analysis ◽  
Broad Band ◽  
Control Valve ◽  
Piping System ◽  
Range Limit ◽  
Analysis Technique ◽  
Engineering Department ◽  
Multistage Compressor ◽  
Turboshaft Engine ◽  
Behavior Characteristics

Nowadays, the operative range limit of compressors is still a key aspect of the research into turbomachinery. In particular, the study of the mass flow rate lower limit represents a significant factor in order to predict and avoid the inception of critical working conditions and instabilities such as stall and surge. The importance of predicting and preventing these dangerous phenomena is vital since they lead to a loss of performance and severe damage to the compression system and the compressor components. The identification of the typical precursors of these two types of compressor unstable behaviors can imply many advantages, in both stationary and aeronautic applications, such as i) avoiding the loss of production (in industry) and efficiency of systems and ii) reducing the cost of maintenance and repairing. Many approaches can be adopted to achieve this target, but one of the most fascinating is the vibro-acoustic analysis of the compressor response during operation. At the Engineering Department of the University of Ferrara, a test bench, dedicated to the study of the performance of an aeronautic turboshaft engine multistage compressor, has been equipped with a high frequency data acquisition system. A set of triaxle accelerometers and microphones, suitable for capturing broad-band vibration and acoustic phenomena, were installed in strategic positions along the compressor and the test rig. Tests were carried out at different rotational speeds, and with two different piping system layouts, by varying the discharge volume and the position of the electric control valve. Moreover, two different methodologies were adopted to lead the compressor towards instability. This experimental campaign allowed the inception of compressor stall and surge phenomena and the acquisition of a great amount of vibro-acoustic data which were firstly processed through an innovative data analysis technique, and then correlated to the thermodynamic data recorded. Subsequently, the precursor signals of stall and surge were detected and identified demonstrating the reliability of the methodology used for the study of compressor instability. The results of this paper can provide a significant contribution to the knowledge of the inception mechanisms of these instabilities. In particular, the experimental data can offer a valid support to the improvement of surge and stall avoidance (or control) techniques since it presents an alternative way of analyzing and detecting unstable compressor behavior characteristics by means of non-intrusive measurements.

Effect of Temperature Nonuniformity on Heat Transfer in an Unshrouded Transonic HP Turbine: An Experimental and Computational Investigation

2010 ◽  
Author(s):  
Imran Qureshi ◽  
Andy D. Smith ◽  
Kam S. Chana ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Test Facility ◽  
Effect Of Temperature ◽  
Inlet Temperature ◽  
Experimental Measurements ◽  
Turbine Stage ◽  
Cfd Simulations ◽  
Turbine Inlet

Detailed experimental measurements have been performed to understand the effects of turbine inlet temperature distortion (hot-streaks) on the heat transfer and aerodynamic characteristics of a full-scale unshrouded high pressure turbine stage at flow conditions that are representative of those found in a modern gas turbine engine. To investigate hot-streak migration, the experimental measurements are complemented by three-dimensional steady and unsteady CFD simulations of the turbine stage. This paper presents the time-averaged measurements and computational predictions of rotor blade surface and rotor casing heat transfer. Experimental measurements obtained with and without inlet temperature distortion are compared. Time-mean experimental measurements of rotor casing static pressure are also presented. CFD simulations have been conducted using the Rolls-Royce code Hydra, and are compared to the experimental results. The test turbine was the unshrouded MT1 turbine, installed in the Turbine Test Facility (previously called Isentropic Light Piston Facility) at QinetiQ, Farnborough UK. This is a short duration transonic facility, which simulates engine representative M, Re, Tu, N/T and Tg /Tw at the turbine inlet. The facility has recently been upgraded to incorporate an advanced second-generation temperature distortion generator, capable of simulating well-defined, aggressive temperature distortion both in the radial and circumferential directions, at the turbine inlet.

scholarly journals Transient Three-Dimensional Side-Load Analysis of Out-of-Round Film-Cooled Nozzles

2011 ◽  
Vol 27 (4) ◽  
pp. 899-907 ◽  
Author(s):  
Ten-See Wang ◽  
Jeff Lin ◽  
Joe Ruf ◽  
Mike Guidos
Keyword(s):  
Three Dimensional ◽  
Side Load ◽  
Load Analysis
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