scholarly journals An Experimental Investigation of Thermal Effects in a Cavitating Inducer

2004 ◽  
Vol 126 (5) ◽  
pp. 716-723 ◽  
Author(s):  
Jean-Pierre Franc ◽  
Claude Rebattet ◽  
Alain Coulon
Keyword(s):  
Thermal Effects ◽  
Cavity Length ◽  
Cold Water ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Operating Conditions ◽  
Fluid Temperature ◽  
Two Phase ◽  
Thermodynamic Effect ◽  
Comparison Of Tests

The thermal effects which affect the development of leading edge cavitation in an inducer were investigated experimentally using refrigerant R114. For different operating conditions, the evolution of the cavity length with the cavitation parameter was determined from visualizations. The tests were conducted up to two-phase breeding. The comparison of tests in R114 and in cold water allowed us to estimate the amplitude of the thermodynamic effect. The results show that the B-factor depends primarily upon the degree of development of cavitation but not significantly upon other parameters such as the inducer rotation speed or the fluid temperature, at least in the present domain of investigation. These trends are qualitatively in agreement with the classical entrainment theory. In addition, pressure fluctuations spectra were determined in order to detect the onset of cavitation instabilities and particularly of alternate blade cavitation and rotating cavitation. If the onset of alternate blade cavitation appeared to be connected to a critical cavity length, the results are not so clear concerning the onset of rotating cavitation.

Thermodynamic Effect on a Cavitating Inducer—Part I: Geometrical Similarity of Leading Edge Cavities and Cavitation Instabilities

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Jean-Pierre Franc ◽  
Guillaume Boitel ◽  
Michel Riondet ◽  
Éric Janson ◽  
Pierre Ramina ◽  
...  
Keyword(s):  
Transit Time ◽  
Cavity Length ◽  
Cold Water ◽  
Rotation Speed ◽  
Leading Edge ◽  
Cavitation Number ◽  
Thermodynamic Effect ◽  
Cavity Closure ◽  
Cavity Development ◽  
Onset Of Cavitation

The thermodynamic effect on a cavitating inducer is investigated from joint experiments in cold water and Refrigerant 114. The analysis is focused on leading edge cavitation and cavitation instabilities, especially on alternate blade cavitation and supersynchronous rotating cavitation. The cavity length along cylindrical cuts at different radii between the hub and casing is analyzed with respect to the local cavitation number and angle of attack. The similarity in shape of the cavity closure line between water and R114 is examined and deviation caused by thermodynamic effect is clarified. The influence of rotation speed on cavity length is investigated in both fluids and analyzed on the basis of a comparison of characteristic times, namely, the transit time and a thermal time. Thermodynamic delay in the development of leading edge cavities is determined and temperature depressions within the cavities are estimated. Thresholds for the onset of cavitation instabilities are determined for both fluids. The occurrence of cavitation instabilities is discussed with respect to the extent of leading edge cavitation. The thermodynamic delay affecting the occurrence of cavitation instabilities is estimated and compared with the delay on cavity development.

scholarly journals Influence of Thermodynamic Effect on Blade Load in a Cavitating Inducer

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Kengo Kikuta ◽  
Noriyuki Shimiya ◽  
Tomoyuki Hashimoto ◽  
Mitsuru Shimagaki ◽  
Hideaki Nanri ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Pressure Rise ◽  
Cavitation Number ◽  
Design Parameters ◽  
Trailing Edge ◽  
Thermodynamic Effect ◽  
Blade Tip

Distribution of the blade load is one of the design parameters for a cavitating inducer. For experimental investigation of the thermodynamic effect on the blade load, we conducted experiments in both cold water and liquid nitrogen. The thermodynamic effect on cavitation notably appears in this cryogenic fluid although it can be disregarded in cold water. In these experiments, the pressure rise along the blade tip was measured. In water, the pressure increased almost linearly from the leading edge to the trailing edge at higher cavitation number. After that, with a decrease of cavitation number, pressure rise occurred only near the trailing edge. On the other hand, in liquid nitrogen, the pressure distribution was similar to that in water at a higher cavitation number, even if the cavitation number as a cavitation parameter decreased. Because the cavitation growth is suppressed by the thermodynamic effect, the distribution of the blade load does not change even at lower cavitation number. By contrast, the pressure distribution in liquid nitrogen has the same tendency as that in water if the cavity length at the blade tip is taken as a cavitation indication. From these results, it was found that the shift of the blade load to the trailing edge depended on the increase of cavity length, and that the distribution of blade load was indicated only by the cavity length independent of the thermodynamic effect.

CFD-Tools for Assessment of the Reactor Pressure Vessel Integrity in Pressure Thermal Shock Conditions: Thermal-Hydraulic Methods and Main Industrial Results on the French 900 MWe PWR RPV

2009 ◽  
Author(s):  
A. Martin ◽  
F. Lestang ◽  
S. Bellet ◽  
D. Guichard ◽  
C. Vit ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Pressure Vessel ◽  
Cold Water ◽  
Reactor Pressure Vessel ◽  
Fluid Temperature ◽  
Time Duration ◽  
Two Phase ◽  
Safety Margins ◽  
Reactor Pressure ◽  
Fast Fracture

For the Reactor Pressure Vessel (RPV) assessment and lifetime evaluation of the nuclear plants, French Utilities apply a series of calculations including thermal-hydraulic, thermo mechanical and fracture mechanics studies in order to study the Pressurized Thermal Shock (PTS) in the downcomer caused by the safety injection. Within the frame of the plant lifetime project, integrity assessments of the French 900 MWe (3-loops) series RPV have been performed. A gain for safety margins to fast fracture of the RPV can be found with a 3D modeling of thermal-hydraulics loads. From a physical phenomena point of view, the results of the system code analysis (CATHARE computation) of the PTS transient induce two kinds of scenarios: single phase and two-phase flows in the cold leg. In the case where the cold legs are partially filled with steam, it becomes a two-phase problem and new important effects occur. Thus, an advanced prediction of RPV thermal loading during these transients requires sophisticated two-phase, local scale, 3D codes. For that purpose, a program has been set up to extend the capabilities of the NEPTUNE_CFD two-phase solver which is the tool able to solve two-phase flow configuration. At the same time, a simplified approach has shown that for this kind of scenario where the cold leg is weakly uncovered, a free surface calculation (without phase change) was sufficient to respect the necessary criteria of safety. Considering the time duration of 3D computation and the large number of cases, EDF and AREVA-NP decided to share the effort. The two teams use the NEPTUNE_CFD code (coupled with the thermal solid SYRTHES code) for thermal-hydraulic computations. The thermo mechanical code used is CALORI. According to this approach and to reduce the CPU time, two computations have been performed for 2″ and 3″ Small Break Loss Of Coolant Accident (SBLOCA) on a one-third RPV model. Computations on a complete RPV model have been performed to demonstrate the relevance of the one-third RPV model. The studies have been performed by two independent teams from EDF and AREVA-NP. The investigated configuration corresponds to the injection of cold water in the RPV during a penalizing representation of a primary break transient and its impact on the solid part formed by cladding and base metal. Numerical results are given in terms of fluid temperature in the cold legs and in the downcomer. The obtained numerical description of the transient is used as boundary conditions for a full mechanical computation of the stresses. The results show that such a complete thermal-hydraulic and mechanical 3-dimensional analysis improves the evaluation of the consequences of the loading on the stress fields and eventually the margins to fast fracture of the RPV. The good agreement observed between a one-third RPV model and a complete RPV model results confirms the validity of the approach.

scholarly journals Temperature Compensation for Conductivity-Based Phase Fraction Measurements with Wire-Mesh Sensors in Gas-Liquid Flows of Dilute Aqueous Solutions

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7114
Author(s):  
Philipp Wiedemann ◽  
Felipe de Assis Dias ◽  
Eckhard Schleicher ◽  
Uwe Hampel
Keyword(s):  
Temperature Effects ◽  
Temperature Compensation ◽  
Phase Distribution ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Wire Mesh ◽  
Effect Of Temperature ◽  
Experimental Investigations ◽  
Fluid Temperature ◽  
Two Phase

Wire-mesh sensors are well-established scientific instruments for measuring the spatio-temporal phase distribution of two-phase flows based on different electrical conductivities of the phases. Presently, these instruments are also applied in industrial processes and need to cope with dynamic operating conditions increasingly. However, since the quantification of phase fractions is achieved by normalizing signals with respect to a separately recorded reference measurement, the results are sensitive to temperature differences in any application. Therefore, the present study aims at proposing a method to compensate temperature effects in the data processing procedure. Firstly, a general approach is theoretically derived from the underlying measurement principle and compensation procedures for the electrical conductivity from literature models. Additionally, a novel semi-empirical model is developed on the basis of electrochemical fundamentals. Experimental investigations are performed using a single-phase water loop with adjustable fluid temperature in order to verify the theoretical approach for wire-mesh sensor applications and to compare the different compensation models by means of real data. Finally, the preferred model is used to demonstrate the effect of temperature compensation with selected sets of experimental two-phase data from a previous study. The results are discussed in detail and show that temperature effects need to be handled carefully—not merely in industrial applications, but particularly in laboratory experiments.

Experimental and Numerical Investigation of the Unsteady Flow Field in a Vaned Diffuser of a High-Speed Centrifugal Compressor

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Klemens Vogel ◽  
Reza S. Abhari ◽  
Armin Zemp
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Fast Response ◽  
Operating Conditions ◽  
Wake Flow ◽  
Vaned Diffuser ◽  
Wide Range ◽  
The Impact

Vaned diffusers in centrifugal compressor stages are used to achieve higher stage pressure ratios, higher stage efficiencies, and more compact designs. The interaction of the stationary diffuser with the impeller can lead to resonant vibration with potentially devastating effects. This paper presents unsteady diffuser vane surface pressure measurements using in-house developed, flush mounted, fast response piezoresistive pressure transducers. The unsteady pressures were recorded for nine operating conditions, covering a wide range of the compressor map. Experimental work was complemented by 3D unsteady computational fluid dynamics (CFD) simulations using ansys cfx V12.1 to detail the unsteady diffuser aerodynamics. Pressure fluctuations of up to 34.4% of the inlet pressure were found. High pressure variations are present all along the vane and are not restricted to the leading edge region. Frequency analysis of the measured vane surface pressures show that reduced impeller loading, and the corresponding reduction of tip leakage fluid changes the characteristics of the fluctuations from a main blade count to a total blade count. The unsteady pressure fluctuations in the diffuser originate from three distinct locations. The impact of the jet-wake flow leaving the impeller results in high variation close to the leading edge. It was observed that CFD results overpredicted the amplitude of the pressure fluctuation on average by 62%.

Thermodynamic Effect on a Cavitating Inducer in Liquid Nitrogen

2006 ◽  
Vol 129 (3) ◽  
pp. 273-278 ◽  
Author(s):  
Yoshiki Yoshida ◽  
Kengo Kikuta ◽  
Satoshi Hasegawa ◽  
Mitsuru Shimagaki ◽  
Takashi Tokumasu
Keyword(s):  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Cavitation Number ◽  
Experimental Investigations ◽  
Thermodynamic Effect ◽  
Blade Tip ◽  
Cryogenic Flow ◽  
The Difference ◽  
Temperature Depression

For experimental investigations of the thermodynamic effect on a cavitating inducer, it is nesessary to observe the cavitation. However, visualizations of the cavitation are not so easy in cryogenic flow. For this reason, we estimated the cavity region in liquid nitrogen based on measurements of the pressure fluctuation near the blade tip. In the present study, we focused on the length of the tip cavitation as a cavitation indicator. Comparison of the tip cavity length in liquid nitrogen (80K) with that in cold water (296K) allowed us to estimate the strength of the thermodynamic effect. The degree of thermodynamic effect was found to increase with an increase of the cavity length. The temperature depression was estimated from the difference of the cavitation number of corresponding cavity condition (i.e., cavity length) between in liquid nitrogen and in cold water. The estimated temperature depression caused by vaporization increased rapidly when the cavity length extended over the throat. In addition, the estimated temperature inside the bubble nearly reached the temperature of the triple point when the pump performance deteriorated.

Startup and Shutdown Steam Generator Separator Piping Forces for a Coal-Fired Supercritical Power Plant

2012 ◽  
Author(s):  
Rajgopal Vijaykumar ◽  
Julie M. Jarvis ◽  
Allen T. Vieira ◽  
James Humphrey ◽  
Dong Zheng
Keyword(s):  
Control System ◽  
Steam Generator ◽  
Power Plants ◽  
Cold Water ◽  
Control Valve ◽  
Operating Conditions ◽  
Operating Characteristics ◽  
Two Phase ◽  
Wide Range ◽  
Valve Opening

Coal-fired supercritical power plants have steam generator liquid/vapor separator systems used during transition to/from “drum” mode and “once-through” mode, which undergo flow transients, involving control systems and valve openings, during startup and shutdown. These transients result in fluid acceleration which can produce significant reaction loads on piping systems (20 kips or higher). The evaluation of these loads is used to design piping supports and to assess possible control system and valving modifications. The computation of these transient loadings is challenging because the conditions in steam generator separator systems range from supercritical to subcritical, two phase, cold water or steam conditions occurring over a wide range of pressures and valve operating characteristics. A transient analysis of a typical separator-condensate line is performed using computer codes RELAP5/MOD3.2 and R5FORCE for the hydrodynamic forcetime history. A range of hydraulic loads associated with a range of operating conditions is provided in this paper using different boundary conditions for separator tank pressure, initial temperature of water in pipe lines, and control valve opening/closing times. These sensitivity runs show the benefit of plant control system changes to prevent the control valves opening above 1400 psia, increasing the control valve opening time to over one second, and the effects of keeping the separator-condensate line hot.

Experimental and Numerical Investigation of the Unsteady Flow Field in a Vaned Diffuser of a High-Speed Centrifugal Compressor

2014 ◽  
Author(s):  
Klemens Vogel ◽  
Reza S. Abhari ◽  
Armin Zemp
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Fast Response ◽  
Operating Conditions ◽  
Wake Flow ◽  
Vaned Diffuser ◽  
Wide Range ◽  
The Impact

Vaned diffusers in centrifugal compressor stages are used to achieve higher stage pressure ratios, higher stage efficiencies and more compact designs. The interaction of the stationary diffuser with the impeller can lead to resonant vibration with potentially devastating effects. This paper presents unsteady diffuser vane surface pressure measurements using in-house developed, flush mounted, fast response piezo-resistive pressure transducers. The unsteady pressures were recorded for 9 operating conditions, covering a wide range of the compressor map. Experimental work was complemented by 3D unsteady CFD simulations using ANSYS CFX V12.1 to detail the unsteady diffuser aerodynamics. Pressure fluctuations of up to 34.4% of the inlet pressure were found. High pressure variations are present all along the vane and are not restricted to the leading edge region. Frequency analysis of the measured vane surface pressures show that reduced impeller loading and the corresponding reduction of tip leakage fluid changes the characteristics of the fluctuations from a main blade count to a total blade count. The unsteady pressure fluctuations in the diffuser originate from three distinct locations. The impact of the jet wake flow leaving the impeller results in high variation close to the leading edge. It was observed that CFD results overpredicted the amplitude of the pressure fluctuation on average by 62%.

Influence of Rotational Speed on Thermodynamic Effect in a Cavitating Inducer

2009 ◽  
Author(s):  
Kengo Kikuta ◽  
Yoshiki Yoshida ◽  
Tomoyuki Hashimoto ◽  
Hideaki Nanri ◽  
Tsutomu Mizuno ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Rotational Speed ◽  
Cavity Length ◽  
Cold Water ◽  
Thermodynamic Effect ◽  
Suction Performance ◽  
Temperature Depression

To estimate the influence of velocity on the thermodynamic effect, we conducted experiments in which the inducer rotational speed was changed in liquid nitrogen. The experiments in liquid nitrogen and in cold water allowed us to estimate the amplitude of the thermodynamic effect. In the experiment with lower rotational speed, suction performance was improved. The cavity length at lower rotational speed was shorter than that at higher speed. Thus, we confirmed that the degree of the thermodynamic effect depends on the rotational speed as lower rotational speed suppresses cavity length. Temperature depression was estimated based on a comparison of cavity length in liquid nitrogen and that in water. We found that the degree of temperature depression became smaller when the rotational speed was lower.

scholarly journals LES-based simulation of the time-resolved flow for rotor-stator interactions in axial fan stages

2019 ◽  
Vol 29 (2) ◽  
pp. 657-681 ◽  
Author(s):  
Jesús Manuel Fernandez Oro ◽  
Andrés Meana-Fernández ◽  
Monica Galdo Vega ◽  
Bruno Pereiras ◽  
José González Pérez
Keyword(s):  
Large Scale ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Operating Conditions ◽  
Computational Domain ◽  
Axial Fan ◽  
Stagnation Region ◽  
Content Type ◽  
Rotor Stator Interaction ◽  
Turbulent Scales

Purpose The purpose of this paper is the development of a CFD methodology based on LES computations to analyze the rotor–stator interaction in an axial fan stage. Design/methodology/approach A wall-modeled large eddy simulation (WMLES) has been performed for a spanwise 3D extrusion of the central section of the fan stage. Computations were performed for three different operating conditions, from nominal (Q_N) to off-design (85 per cent Q_N and 70 per cent Q_N) working points. Circumferential periodic conditions were introduced to reduce the extent of the computational domain. The post-processing procedure enabled the segregation of unsteady deterministic features and turbulent scales. The simulations were experimentally validated using wake profiles and turbulent scales obtained from hot-wire measurements. Findings The transport of rotor wakes and both wake–vane and wake–wake interactions in the stator flow field have been analyzed. The description of flow separation, particularly at off-design conditions, is fully benefited from the LES performance. Rotor wakes impinging on the stator vanes generate a coherent large-scale vortex shedding at reduced frequencies. Large pressure fluctuations in the stagnation region on the leading edge of the vanes have been found. Research limitations/implications LES simulations have shown to be appropriate for the assessment of the design of an axial fan, especially for specific operating conditions for which a URANS model presents a lower performance for turbulence description. Originality/value This paper describes the development of an LES-based simulation to understand the flow mechanisms related to the rotor–stator interaction in axial fan stages.

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