scholarly journals Static Characteristics and Leakage Rates of Smooth Annular Seals Based on a New Solution Method for Gas-Liquid Two-Phase Conditions

2021 ◽  
Vol 9 (5) ◽  
pp. 523
Author(s):  
Chao Zhong ◽  
Lulu Zhai ◽  
Jia Guo ◽  
Baoling Cui ◽  
Guoyou Chen
Keyword(s):  
Solution Method ◽  
Volume Fraction ◽  
Bubble Radius ◽  
Maximum Error ◽  
Axial Position ◽  
Static Characteristics ◽  
Two Phase ◽  
Mixture Density ◽  
Gas Volume Fraction ◽  
Gas Volume

This paper proposes a new solution method for the leakage and static characteristics of smooth annular seal under a homogeneous gas-liquid two-phase flow based on a bulk-flow model. In this solution method, the Rayleigh–Plesset equation is introduced into the governing equations to describe the behavior of bubbles considering mixture compressibility. Detailed comparisons between Childs’ experimental leakage rates and predicted ones based on the proposed method are conducted, and the predicted results show good agreement with the experimental results, with a maximum error of 11.2%. Moreover, static characteristics of the seal, including leakage rates, gas volume fraction (GVF) distribution, pressure distribution, mixture density, and viscosity within the seals, are investigated based on the present method. The results show that as the inlet gas volume fraction increases from 0% to 10%, the local gas volume fraction of each axial position will increase, however, the seal leakage, mixture density, and mixture viscosity will decrease. Bubble radius has little effect on the leakage rates and the static characteristics of the seals. Additionally, comparisons between the characteristics of the model seals with different clearances show that the leakages of the seals with bigger clearance behave more sensitively to the inlet GVF changes.

scholarly journals Effect of Gas Volume Fraction on the Energy Loss Characteristics of Multiphase Pumps at Each Cavitation Stage

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2293
Author(s):  
Jianwei Shi ◽  
Sijia Tao ◽  
Guangtai Shi ◽  
Wenwu Song
Keyword(s):  
Energy Loss ◽  
Volume Fraction ◽  
Axial Flow ◽  
Two Phase ◽  
Multiphase Pump ◽  
Cavitation Phenomenon ◽  
Flow Loss ◽  
Gas Volume Fraction ◽  
Critical Cavitation ◽  
Gas Volume

In the process of conveying a medium, when the inlet pressure is low, the cavitation phenomenon easily occurs in the pump, especially in the gas–liquid two-phase working condition. The occurrence of the cavitation phenomenon has a great impact on the performance of the multiphase pump. In this paper, the SST (sheard stress transport) k-ω turbulence model and ZGB (Zwart–Gerber–Belamri) cavitation model were used to simulate the helical axial flow multiphase pump (hereinafter referred to as the multiphase pump), and the experimental verification was carried out. The effect of gas volume fraction (GVF) on the energy loss characteristics in each cavitation stage of the multiphase pump is analyzed in detail. The study shows that the critical cavitation coefficient of the multiphase pump gradually decreases with the increase in GVF, which depresses the evolution of cavitation, and the cavitation performance of the multiphase hump is improved. The ratio of total loss and friction loss to total flow loss in the impeller fluid domain gradually increases with the development of cavitation, and the pressurization performance of the multiphase pump gradually decreases with the development of cavitation. The results of the study can provide theoretical guidance for the improvement of the performance of the multiphase pump.

Numerical Study of Reactor Cooling Pumps Under Two-Phase Gas-Liquid Flow

2014 ◽  
Author(s):  
Peng Wang ◽  
Shouqi Yuan ◽  
Xiuli Wang ◽  
Guidong Li ◽  
Banglun Zhou ◽  
...  
Keyword(s):  
Computational Models ◽  
Volume Fraction ◽  
Numerical Study ◽  
Linear Increase ◽  
Suction Surface ◽  
Two Phase ◽  
Gas Volume Fraction ◽  
Head Pressure ◽  
Simulation Results ◽  
Gas Volume

In this paper, the unsteady pressure field and head-drop phenomenon caused by one of the most dangerous accidents in reactor plants known as Loss of Coolant Accident (LOCA) in its worse condition called small LOCA have been investigated numerically by computational fluid dynamics (CFD) in a nuclear reactor cooling pump. Five computational models with different blades had been calculated using Eulerian-Eulerian two fluid models using a multiphase approach. Simulation results show increasing gas volume fraction results in a sharp decline of the head pressure and pump efficiencies for each of 5 kinds of pumps modeled. This is especially evident for both the head pressure of impeller types C and impeller E. Here only have operating at half (58m and 54.9m)of the design condition when the gas volume fraction is 25%. The analysis of inner flow field of the five model pumps shown that the lower pressure area appeared at the inlet and outlet of the impeller as well as a small part distribution at the inlet of the diffuser, which is the main reason made the gas bubbles tend to concentrate at the impeller eye on the suction surface, the distribution of two phases appeared by non-linear increase and random located in whole passages. The experimental and simulation results are compared and are in good agreement with values obtained for the global performance at lower gas contents (below20%). When the gas contents increases to 25%, the bubbles occupy the passages, which effectively causes unsteady flow in the gas phase cannot be neglected for accurately predicting the inner flow of the pump. These results imply that this numerical method is suitable for the two-phase flow under certain gas contents (below 20%) in the reactor cooling pump.

Measurement of a Void Fraction in Bubbly Gas-Water Two Phase Flows Using Differential Pressure Technique

2012 ◽  
Vol 152-154 ◽  
pp. 1221-1226
Author(s):  
H.A.M. Hasan Abbas
Keyword(s):  
Experimental Study ◽  
Void Fraction ◽  
Volume Fraction ◽  
Differential Pressure ◽  
Flow Density ◽  
Two Phase Flows ◽  
Two Phase ◽  
Gas Volume Fraction ◽  
Fraction Measurement ◽  
Gas Volume

Multiphase flows, where two or even three fluids flow simultaneously in a pipe are becoming increasingly important in industry. In order to measure the flow rate of gas-water two phase flows accurately, the void fraction (gas volume fraction) in two phase flows must be precisely measured. The differential pressure technique has proven attractive in the measurement of volume fraction. This paper presents the theoretical and experimental study of the void fraction measurement in bubbly gas water two phase flows using differential pressure technique (the flow density meter).

Bubbly, Two-Phase Flow in the Anode Channel of a Passive, Tubular Direct Methanol Fuel Cell

2011 ◽  
Author(s):  
Hafez Bahrami ◽  
Amir Faghri
Keyword(s):  
Experimental Data ◽  
Direct Methanol Fuel Cell ◽  
Volume Fraction ◽  
Catalyst Layer ◽  
Two Phase ◽  
Direct Methanol ◽  
Cell Current ◽  
Gas Volume Fraction ◽  
Gas Volume ◽  
Methanol Fuel Cell

A numerical study is presented to investigate the turbulent, two-phase, steady state, isothermal, bubbly flow characteristic in the anode channel of a passive, tubular direct methanol fuel cell (DMFC) in order to accurately predict the gas volume fraction distribution along the channel. Accumulation of carbon dioxide gas bubbles at the channel’s wall hinders the diffusion of the fuel from the channel to the catalyst layer. The conservation governing equations of the mass and momentum for both the continuous (methanol and water solution) and dispersed (CO2 bubbles) phases in the bubbly regime are solved using the multi-fluid technique. Turbulence in the liquid phase is formulated by employing the classical, two-equation k–ε model. Due to the lack of experimental data regarding the gas volume fraction in the anode channel of DMFCs, the proposed model was initially applied to the bubble plum in a cylindrical liquid bath in which air is injected into the water from a nozzle located at the bottom-center of the bath. The results are compared with the existing experimental data in the literature for the gas volume fraction and the liquid velocity in the bath. Finally, the model is successfully extended to the anode channel of a tubular DMFC operating passively in the vertical orientation in which the CO2 gas bubbles are injected through the wall. The rate of gas injection depends on the cell current density which is assumed to be uniform along the anode catalyst layer and the channel’s wall. It is found that the gas volume fraction significantly changes along the channel from a large value at the bottom of the channel to a lower value at the top. The flow field inside the channel is also investigated for different cell current densities.

Experimental investigation on the performance of a side channel pump under gas–liquid two-phase flow operating condition

2017 ◽  
Vol 231 (7) ◽  
pp. 645-653 ◽  
Author(s):  
Fan Zhang ◽  
Martin Böhle ◽  
Shouqi Yuan
Keyword(s):  
Two Phase Flow ◽  
Volume Fraction ◽  
Low Flow ◽  
Side Channel ◽  
Phase Flow ◽  
Vane Pump ◽  
Two Phase ◽  
Operating Condition ◽  
Gas Volume Fraction ◽  
Gas Volume

Side channel pump is a kind of small volume vane pump with low flow rate but high head and most side channel pumps can transport gas–liquid two-phase flow. In order to investigate the performance of this type of pump depending on the blade suction angle under gas–liquid two-phase flow operating condition, an experimental study has been carried out. The head and efficiency curves, and the influence of blade suction angle changes on these curves for different inlet gas volume fraction states are analyzed in detail. Moreover, the gas transporting capability of the impeller with three different blade suction angles (10°, 20°, 30°) are also compared. The results show that the head and efficiency performances of the three impellers decrease a large value when the side channel pump operates with a little gas inside, and the operating range narrows as well. With the increasing of inlet gas volume fraction, the performance of the side channel pump worsens. The head and efficiency performances in the single-phase state improve by increasing the blade suction angle, but decrease by increasing the blade suction angle in the gas–liquid two-phase flow state. The maximum gas transporting capability of the impeller with a small blade suction angle is better than a large blade suction angle. Analysis on the measured data allows a better understanding of the effect of inlet gas quantity on the performance of the side channel pump with different blade suction angles, and it could supply the design reference for two-phase flow side channel pumps.

Investigation of the Self-Priming Process of Self-Priming Pump Under Gas-Liquid Two-Phase Condition

2014 ◽  
Author(s):  
Guidong Li ◽  
Yang Wang ◽  
Gang Yin ◽  
Yurui Cui ◽  
Qihong Liang
Keyword(s):  
Two Phase Flow ◽  
Volume Fraction ◽  
Guide Vane ◽  
The Self ◽  
Phase Flow ◽  
Two Phase ◽  
Pump Chamber ◽  
Priming Process ◽  
Gas Volume Fraction ◽  
Gas Volume

The self-priming process of self-priming pump is gas-liquid two-phase flow process with complex internal transient flow. The effect of gas-liquid mixing and separating performances will play a crucial role during self-priming process. In order to study the self-priming process and improve the self-priming performance, the model named JETST-100 was selected. Based on Eulerian-Eulerian multiphase flow model, transient numerical simulation of the gas-liquid mixing and separating phenomena on the pump chamber was carried out by using CFX software. The distributions of velocity vector, contours of gas volume fraction and liquid velocity of the pump or jet aerator, and the change of the gas volume fraction by monitoring points on the jet aerator were obtained. Test and simulation results show that the gas-liquid two-phase flow from the guide vane will form a larger velocity circulation, so that the gas-liquid separation is not sufficient. And the volume fraction of liquid inside pump chamber decrease with a large amount of water enters the outlet pipe. It is found that adding the baffle plate can prevent the generation of circulation on guide vane back, the gas-phase volume fraction of jet aerator inlet and nozzle outlet decreases, improve the self-priming performance of the pump.

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