Investigation of Pressure Losses and Flow Fluctuations in an Intercept Valve Assembly of an Intermediate-Pressure Turbine Part

2020 ◽  
Author(s):  
Vaclav Slama ◽  
Lukas Mrozek ◽  
Bartolomej Rudas ◽  
David Simurda ◽  
Jindrich Hala ◽  
...  
Keyword(s):  
Flow Separation ◽  
Pressure Loss ◽  
Pressure Fluctuations ◽  
Control Valve ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Pressure Losses ◽  
Flow Fluctuations ◽  
Valve Assembly ◽  
Valve Model

Abstract A new design of an intercept valve assembly of the intermediate-pressure turbine part of greater power output is investigated in terms of pressure losses and flow fluctuations by using measurement on an experimental valve model. In addition, numerical simulations are used to further clarify measured phenomena. For such valve assemblies, it is important to exactly predict pressure losses and avoid danger of vibrations, which are caused by undesirable flow fluctuations, in order to guarantee valve’s efficiency and operational reliability. For this type of valve, it is especially important for turbine operations in partial loads (off-design conditions). Measurements were carried out in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences (IT) in a modular aerodynamic tunnel. Numerical simulations were carried out in the Doosan Skoda Power Company (DSP) by using a package of ANSYS software tools. The experimental valve model is a scaled model of a real valve assembly. It consists of an inlet pipeline, a stop valve and a control valve including its diffuser and outlet pipeline. Measured regimes were defined by a mass flow rate and a control valve cone lift which can be precisely changed. In order to investigate pressure loses, total and static pressures at valve characteristic locations were measured by using Prandtl probes and wall static pressure taps. In order to measure pressure fluctuations, Kulite fast response pressure transducers were used. They were situated near the valve throat where the flow fluctuations, which are strongly related to a flow separation, are the most visible and influential. Measurement results are compared with numerical results and locations with a flow separation were found. In order to reduce this phenomenon, different valve seat angles were also tested. As a result, a valve design could be optimized and, for a pressure loss prediction, a pressure loss model for this new intercept valve assembly could be created. Therefore, pressure losses in similar valve assemblies can be predicted with required accuracy for each new turbine where modern intercept valves are used. This helps to increase steam turbine efficiency and reduce fuel consumption. Based on pressure fluctuations results, operating conditions at which dangerous flow instabilities occur were identified. It was concluded that there is an operating condition border where the flow field starts to be unstable. As a result, the areas of safe and dangerous operating conditions can be predicted so that the operational reliability of the valve can be guaranteed.

Experimental and Numerical Study on Pressure Losses and Flow Fluctuations in a High-Pressure Valve Assembly of Steam Turbine Governing System

2020 ◽  
Author(s):  
Vaclav Slama ◽  
Lukas Mrozek ◽  
Bartolomej Rudas ◽  
David Simurda ◽  
Jindrich Hala ◽  
...  
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Numerical Simulations ◽  
Pressure Loss ◽  
Operational Reliability ◽  
Operating Conditions ◽  
The Real ◽  
Pressure Losses ◽  
Flow Fluctuations ◽  
Valve Assembly

Abstract Aerodynamic measurements and numerical simulations carried out on a model of a high-pressure valve assembly used for nozzle governing of a turbine with 135MW output are described in this paper. Aim of the study is to investigate effects of control valve’s strainers on pressure losses and unsteadiness in the flow field. It is an important task since undesirable flow fluctuations can lead to operational reliability issues. Measurements were carried out in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences (IT) where an aerodynamic tunnel is installed. Numerical simulations were carried out in the Doosan Skoda Power (DSP) Company using ANSYS software tools. The experimental model consists of one of two identical parts of the real valve assembly. It means it consists of an inlet pipeline, a stop valve, a valve chamber with two independent control valves, its diffusers and outlet pipelines. The numerical model consists of both assembly parts and includes also an A-wheel control stage in order to simulate the real turbine operating points. The different lifts of the main cone in each control valve for its useful combinations were investigated. Results were evaluated on the model with control valve’s strainers, which were historically used in order to stabilize the flow, and without them. The results of the experimental measurement were compared with the numerical results in the form of pressure losses prediction. From measured pressure fluctuations, it was found out where and for which conditions a danger of flow instabilities occurs. It can be concluded that there is a border, in terms of operating conditions, where the flow field starts to be unstable and this border is different dependent of the fact whether the control valve’s strainers are used or not. Therefore, the areas of safe and danger operational reliability can be predicted. The influence of the control valve’s strainers on the maximal amplitude of periodic fluctuations appears only for the cases when valves are highly overloaded. For normal operating conditions, there is no difference. As a result, the control valve’s strainers do not have to be used in standard applications of valve assemblies. Furthermore, a loss model for valve pressure loss estimation could be updated. Therefore, a pressure loss should be predicted with a sufficient accuracy for each new turbine bid with similar valve assemblies.

scholarly journals Pressure losses and oscillations in a compact valve of a steam turbine

2021 ◽  
Vol 345 ◽  
pp. 00027
Author(s):  
Václav Sláma ◽  
David Šimurda ◽  
Lukáš Mrózek ◽  
Ladislav Tajč ◽  
Jindřich Hála ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Pressure Oscillation ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Steam Turbines ◽  
Valve Seat ◽  
Pressure Losses ◽  
Oscillation Analysis ◽  
Seat Angle ◽  
Wide Range

Characteristics of a new compact valve design for steam turbines are analysed by measuring pressure losses and oscillations on the valve model. It is the model of an intercept valve of the intermediate-pressure turbine part. This valve is relatively smaller hence cheaper than usual control and intercept valves. Besides, four different valve seat angles were tested in order to investigate the valve seat angle influence. In order to further clarify measured phenomena, the wide range of numerical simulations were also carried out. Measurements were performed in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences in an air test rig installed in a modular aerodynamic tunnel. Numerical simulations were performed in the Doosan Skoda Power Company using a package of ANSYS software tools. Measurement results are compared with numerical and generalized in the form of valve characteristics and pressure oscillation maps. As a result of the pressure loss analysis, pressure losses in similar valve assemblies can be predicted with required accuracy for each new turbine where modern compact valves are used. As a result of the pressure oscillation analysis, operating conditions at which dangerous flow instabilities can occur were identified. Thanks to this, the areas of safe and dangerous operating conditions can be predicted so that the operational reliability of the valve can be guaranteed.

Low Pressure Steam Turbine Exhaust Flow: Part 2 — Investigation of the Condenser Neck Flow Field and 1D Modelling

2016 ◽  
Author(s):  
Dirk Telschow ◽  
Peter Stein ◽  
Hartwig Wolf ◽  
Alessandro Sgambati
Keyword(s):  
Flow Field ◽  
Pressure Loss ◽  
Low Pressure ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Computational Time ◽  
Plant Design ◽  
Pressure Losses ◽  
Design Changes ◽  
1D Modelling

Since many years the diffuser and exhaust of low pressure (LP) turbines are in focus of turbine development and accordingly broadly discussed within the scientific community. The pressure recovery gained within the diffuser significantly contributes to the turbine performance and therefore care is taken in flow investigation as well as optimization within this part of the turbine. However, on a plant level the component following the LP turbine is the condenser, which is connected by the condenser neck. Typically the condenser neck is not designed to provide additional enthalpy recovery. For plant design reasons, often numerous built-ins like stiffening struts, extraction pipes, steam dump devices and others are placed into the neck. Here it is vital to keep the pressure losses low, in order not to deteriorate performance, previously gained within the diffuser. Each mbar of total pressure loss in a condenser can reduce the plant power output up to 0.1%. As discussed in the first publication (Part 1), 3D CFD enables a deep insight into the flow field, which is costly with respect to computational time and resources. But there are phases during project execution, when geometry and/or boundary conditions are not fixed and quick estimation of pressure loss and recovery in the condenser neck is needed for benchmark of designs or design changes (e.g. tender phase). Here 1D modelling approaches can help to close the gap. Analysis of available 1D correlation of flow around obstacles has shown that these need to be adapted to the flow conditions in a condenser neck of a steam, nuclear or combined-cycle power plant. Therefore, the fluid fields, calculated and discussed in the first publication (Part 1), were analyzed regarding pressure loss created by single obstacles and interaction of built-ins of different size, number and shape. Furthermore, a 1D velocity to be used for 1D calculation was derived from the 3D velocity field. In addition, vacuum-correction-curves were implemented to cover the range of possible operating conditions. This publication discusses the development of a 1D model for calculation of pressure loss in a condenser neck and the validity of such calculations against measurement and 3D CFD data.

scholarly journals Unsteady Flow Numerical Simulations on Internal Energy Dissipation for a Low-Head Centrifugal Pump at Part-Load Operating Conditions

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 2013 ◽  
Author(s):  
Xiaoran Zhao ◽  
Yongyao Luo ◽  
Zhengwei Wang ◽  
Yexiang Xiao ◽  
François Avellan
Keyword(s):  
Energy Dissipation ◽  
Internal Energy ◽  
Centrifugal Pump ◽  
Flow Separation ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Operating Condition ◽  
Part Load ◽  
Rotating Impeller ◽  
Low Head

Dredge pumps are usually operated at part-load conditions, in which the low-solidity centrifugal impeller could experience large internal energy dissipation, related to flow separation and vortices. In this study, SST k-ω and SAS-SST turbulence models were used, in steady and unsteady simulations, for a low-head centrifugal pump with a three-bladed impeller. The main focus of the present work was to investigate the internal energy dissipation in rotating an impeller at part-load operating conditions, related to flow separation and stall. The unsteady nature of these operating conditions was investigated. Performance experiments and transient wall pressure measurements were conducted for validation. A methodology for internal energy dissipation analysis has been proposed; and the unsteady pressure fluctuations were analyzed in the rotating impeller. The internal power losses in the volute and the impeller were mostly found in the centrifugal pump. The rotating stall phenomenon occurred with flow separation and detachment at the part-load operating condition, leading to a dissipation of the internal energy in the impeller. The rotating impeller experienced pressure fluctuations with low frequencies, at part-load operating conditions, while in the design operating condition only experienced rotating frequency.

scholarly journals Pressure Loss Reduction in an Innovative Directional Poppet Control Valve

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3149
Author(s):  
Grzegorz Filo ◽  
Edward Lisowski ◽  
Janusz Rajda
Keyword(s):  
Pressure Loss ◽  
Control Valve ◽  
The Body ◽  
Valve Body ◽  
Practical Applications ◽  
Pressure Losses ◽  
Flow Channels ◽  
Directional Control ◽  
Wide Range ◽  
Cfd Analyses

This article presents the results of computational fluid dynamics (CFD) analysis of an innovative directional control valve consisting of four poppet seat valves and two electromagnets enclosed inside a single body. The valve has a unique design, allowing the use of any poppet valve configuration. Both normally opened (NO) and normally closed (NC) seat valves can be applied. The combination of four universal valve seats and two electromagnets gives a wide range of flow path configurations. This significantly increases the possibility of practical applications. However, due to the significant miniaturization of the valve body and the requirement to obtain necessary connections between flow paths, multiple geometrically complex channels had to be made inside the body. Hence, the main purpose of work was to shape the geometry of the flow channels in such a way as to minimize pressure losses. During the CFD analyses velocity distribution in flow channels and pressure distribution on the walls were determined. The results were used to obtain pressure loss as a function of flow rate, which was then verified by means of laboratory experiments conducted on a test bench.

scholarly journals Numerical Delineation of 3D Unsteady Flow Fields in Side Channel Pumps for Engineering Processes

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1287 ◽  
Author(s):  
Fan Zhang ◽  
Ke Chen ◽  
Desmond Appiah ◽  
Bo Hu ◽  
Shouqi Yuan ◽  
...  
Keyword(s):  
Channel Flow ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Flow Fields ◽  
Operational Reliability ◽  
Side Channel ◽  
Velocity Fluctuations ◽  
Flow Passage ◽  
Flow Fluctuations ◽  
Noise Vibration

Side channel pumps are important machines for handling toxic, explosive or other dangerous liquids in various engineering processes. However, the operational reliability of these pumps is directly affected by the intensity of the pressure and velocity fluctuations, thus the flow fluctuations existing within the pump cannot be neglected because of their direct influence on the noise, vibration and harshness performance. Therefore, describing precisely the zones of highly unsteady and turbulent flow fields is a key research topic. Moreover, the size of the wrapping angle strongly affects the levels of pressure and velocity fluctuations, thus numerical calculations of the pressure and velocity fluctuation intensities in side channel pump models with different wrapping angles were conducted in this work. The results indicated that the pressure fluctuation coefficient increased gradually from the inflow to the outflow. At the interrupter, the flow experienced the most irregular flow patterns in the pump. The flow at the inflow region in both the impeller and side channel passage rendered weak pressure fluctuation intensities. All three pump cases operated with 24 blades but after one complete circulatory cycle, cases 1, 2 and 3 revealed 21, 20 and 19 regular pressure fluctuations respectively in the impeller flow passage. On the other hand, the side channel flow passage rather produced 24 regular pressure fluctuations. Furthermore, the main frequency harmonic excitations for all studied monitoring points in the impeller and side channel flow passages of the three pump cases occurred at 600 Hz (24 × fn), 1200 Hz (48 × fn), and 1800 Hz (72 × fn). For this reason, exchanged flow times between the impeller and side channel is mainly responsible for the pressure fluctuation which subsequently affects the noise and vibration generation in the side channel pump. Hence, the results could be used as a reference for Noise-Vibration-Harshness (NVH) study in turbomachinery especially modifying the side channel pump in order to improve the operational reliabilities for many engineering processes.

scholarly journals Hydraulic characteristic of selected installation valves installed on various pipes materials

2018 ◽  
Vol 59 ◽  
pp. 00023
Author(s):  
Krystyna Poręba ◽  
Weronika Kowalczyk ◽  
Marcin K. Widomski ◽  
Anna Musz-Pomorska
Keyword(s):  
Flow Rate ◽  
Pressure Loss ◽  
Water Flow Rate ◽  
Operating Conditions ◽  
Water Control ◽  
Mean Values ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Globe Valve

Presented studies covered determination of minor pressure losses and values of minor loss coefficients for two selected installation valves: water control globe valve and angle valve, both DN 15. The tested valves were installed on three pipes, including PP 20x3.4 mm, PEX-Al-PEX 16x2.0 mm and Cu 15x1.0 mm. In order to reflect the real operating conditions of the angle valve, the elastic PVC pipe was used. Our researches were performed on the laboratory installation, for the variable flow rate. The obtained results of laboratory studies showed the clear dependence between minor pressure loss and minor loss coefficients of studied valves, and water flow rate (Reynolds number), degree of valves’ closure and, in some cases, manner of valves installation and material of pipes. The greatest values of minor pressure loss coefficients, of mean values relevantly statistically grater, were determined for the tested valves installed on the PEX-Al-PEX pipeline.

Investigation of Pressure Losses and Flow Fluctuations in an Intercept Valve Assembly of an Intermediate-Pressure Turbine Part

2021 ◽  
Author(s):  
Vaclav Slama ◽  
Lukas Mrozek ◽  
Bartolomej Rudas ◽  
David Simurda ◽  
Jindrich Hala ◽  
...  
Keyword(s):  
Pressure Losses ◽  
Intermediate Pressure ◽  
Flow Fluctuations ◽  
Valve Assembly

Modeling of pressure losses on friction in three-layer laminar flows

2003 ◽  
Vol 3 ◽  
pp. 208-219
Author(s):  
A.M. Ilyasov
Keyword(s):  
Pressure Loss ◽  
Gas Flow ◽  
Mutual Influence ◽  
Fluid Model ◽  
Immiscible Liquid ◽  
Laminar Flows ◽  
Pressure Losses ◽  
Flow Parameters ◽  
Interphase Boundaries ◽  
Closing Relations

In this paper we propose a model for determining the pressure loss due to friction in each phase in a three-layer laminar steady flow of immiscible liquid and gas flow in a flat channel. This model generalizes an analogous problem for a two-layer laminar flow, proposed earlier. The relations obtained in the final form for the pressure loss due to friction in liquids can be used as closing relations for the three-fluid model. These equations take into account the influence of interphase boundaries and are an alternative to the approach used in foreign literature. In this approach, the wall and interphase voltages are approximated by the formulas for a single-phase flow and do not take into account the mutual influence of liquids on the loss of pressure on friction in phases. The distribution of flow parameters in these two models is compared.

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