Numerical simulation of bubble separation length in a gas–liquid separator based on the Euler–Lagrange method

Tingting Zhang,Junlian Yin,Dezhong Wang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

In this study, the bubble separation behavior in a gas–liquid separator is numerically investigated on the basis of the Euler–Lagrange approach, in which the forces acting on bubbles in a swirling flow field are modeled to calculate the trajectories of the bubbles. By adopting this approach, the effects of five parameters, namely, back pressure, Reynolds number, bubble diameter, void fraction, and swirl number, on separation performance in terms of pressure loss, separation efficiency, separation length, and split ratio are computed and analyzed. On the basis of the analysis, correlations of separation length with the two main parameters are established, which can serve as a basis for the optimal design of separator.

The Effect of Different Inflows on the Unsteady Hydrodynamic Characteristics of a Mixed Flow Pump

Long Yun,Wang Dezhong,Yin Junlian,Cai Youlin,Feng Chao 한국유체기계학회 2017 International journal of fluid machinery and syste Vol.10 No.2

The problem of non-uniform inflow exists in many practical engineering applications, such as the elbow suction pipe of waterjet pump and, the channel head of steam generator which is directly connect with reactor coolant pump. Generally, pumps are identical designs and are selected based on performance under uniform inflow with the straight pipe, but actually non-uniform suction flow is induced by upstream equipment. In this paper, CFD approach was employed to analyze unsteady hydrodynamic characteristics of reactor coolant pumps with different inflows. The Reynolds-averaged Naiver-Stokes equations with the k-ε turbulence model were solved by the computational fluid dynamics software CFX to conduct the steady and unsteady numerical simulation. The numerical results of the straight pipe and channel head were validated with experimental data for the heads at different flow coefficients. In the nominal flow rate, the head of the pump with the channel head decreases by 1.19% when compared to the straight pipe. The complicated structure of channel head induces the inlet flow non-uniform. The non-uniformity of the inflow induces the difference of vorticity distribution at the outlet of the pump. The variation law of blade to blade velocity at different flow rate and the difference of blade to blade velocity with different inflow are researched. The effects of non-uniform inflow on radial forces are absolutely different from the uniform inflow. For the radial forces at the frequency fR, the corresponding amplitude of channel head are higher than the straight pipe at 1.0Фd and 1.2Фd flow rates, and the corresponding amplitude of channel head are lower than the straight pipe at 0.8Фd flow rates.

The Effect of Different Inflows on the Unsteady Hydrodynamic Characteristics of a Mixed Flow Pump

Yun, Long,Dezhong, Wang,Junlian, Yin,Youlin, Cai,Chao, Feng Korean Society for Fluid machinery 2017 International journal of fluid machinery and syste Vol.10 No.2

The problem of non-uniform inflow exists in many practical engineering applications, such as the elbow suction pipe of waterjet pump and, the channel head of steam generator which is directly connect with reactor coolant pump. Generally, pumps are identical designs and are selected based on performance under uniform inflow with the straight pipe, but actually non-uniform suction flow is induced by upstream equipment. In this paper, CFD approach was employed to analyze unsteady hydrodynamic characteristics of reactor coolant pumps with different inflows. The Reynolds-averaged Naiver-Stokes equations with the $k-{\varepsilon}$ turbulence model were solved by the computational fluid dynamics software CFX to conduct the steady and unsteady numerical simulation. The numerical results of the straight pipe and channel head were validated with experimental data for the heads at different flow coefficients. In the nominal flow rate, the head of the pump with the channel head decreases by 1.19% when compared to the straight pipe. The complicated structure of channel head induces the inlet flow non-uniform. The non-uniformity of the inflow induces the difference of vorticity distribution at the outlet of the pump. The variation law of blade to blade velocity at different flow rate and the difference of blade to blade velocity with different inflow are researched. The effects of non-uniform inflow on radial forces are absolutely different from the uniform inflow. For the radial forces at the frequency $f_R$, the corresponding amplitude of channel head are higher than the straight pipe at $1.0{\Phi}_d$ and $1.2{\Phi}_d$ flow rates, and the corresponding amplitude of channel head are lower than the straight pipe at $0.8{\Phi}_d$ flow rates.

Experimental and numerical investigation on the pressure pulsation in reactor coolant pumps under different inflow conditions

Huang Song,Song Yu,Yin Junlian,Xu Rui,Wang Dezhong 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.4

A reactor coolant pump (RCP) is essential for transporting coolant in the primary loop of pressurized water reactors. In the advanced passive reactor, the absence of a long pipeline between the steam generator and RCP serves as a transition section, resulting in a non-uniform flow field at the pump inlet. Therefore, the characteristics of the pump should be investigated under non-uniform flow to determine its influence on the pump. In this study, the pressure pulsation characteristics were examined in the time and frequency domains, and the sources of low-frequency and high-amplitude signals were analyzed using wavelet coherence analysis and numerical simulation. From computational fluid dynamics (CFD) results, non-uniform inflow has a great effect on the flow structures in the pump's inlet. The pressure pulsation in the pump at the rated flow increased by 78–128.7% under the non-uniform inflow condition in comparison with that observed under the uniform inflow condition. Furthermore, a low-frequency signal with a high amplitude was observed, whose energy increased significantly under non-uniform flow. The wavelet coherence and CFD analysis verified that the source of this signal was the low-frequency pulsating vortex under the steam generator.

Experiment and modeling of liquid-phase flow in a venturi tube using stereoscopic PIV

Song, Yuchen,Shentu, Yunqi,Qian, Yalan,Yin, Junlian,Wang, Dezhong Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.1

Venturi tube is based on turbulent flow, whereby the microbubbles can be generated by the turbulent fragmentation. This phenomenon is common in several venturi bubblers used by the nuclear, aerospace and chemical industries. The first objective of this paper is to study the liquid-phase velocity field experimentally and develop correlations for the turbulent quantities. The second objective is to research velocity field characteristics theoretically. Stereoscopic PIV measurements for the velocity field have been analyzed and utilized to develop the turbulent kinetic energy in the venturi tube. The tracking properties of the tracer particles have been verified enough for us to analyze the turbulence field. The turbulence kinetic energy has a bimodal distribution trend. Also, the results of turbulence intensity along the horizontal direction is gradually uniform along the downstream. Both the mean velocity and the fluctuation velocity are proportional to the Reynolds number. Besides, the distribution trend of the mean velocity and the velocity fluctuation can be determined by the geometric parameters of the venturi tube. An analytical function model for the flow field has been developed to obtain the approximate analytical solutions. Good agreement is observed between the model predictions and experimental data.

Numerical and experimental investigation on the diffuser optimization of a reactor coolant pump with orthogonal test approach

Long Yun,Zhu Rongsheng,Wang Dezhong,Yin Junlian,Li Tianbin 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.11

The diffuser of a reactor coolant pump was optimized using an orthogonal approach with numerical simulation to improve the pump hydraulic performance. Steady simulation was conducted by solving Reynolds-averaged Naiver-Stokes equations with the SST k-ω turbulence model using CFX code. The influence of the diffuser geometric parameters, namely, S, φ, α 4 , b 4 , δ 2 , R t and R 4 , on the pump performance were determined. L 18 (3 7 ) orthogonal table was chosen for the optimization process. Best indicators were determined, and range analysis of energy losses, head, and efficiency at the rated condition was performed. Optimal parameters of the diffuser were S = 490 mm, φ = 36°, α 4 = 30°, b 4 = 200 mm, δ 2 = 20 mm, R t = 5 mm and R 4 = 565 mm. The final design was experimentally tested. Simulation results showed more remarkable performance than the experimental result. However, the numerical predictions and experimental results were consistent, validating the design procedure. Loading of the impeller and diffuser blades was analyzed to investigate the direct impact on the hydrodynamic flow field. The head was 14.74 m, efficiency was 79.6 %, and efficiency of the prototype pump was 83.3 % when the model pump functioned at the rated conditions. Optimization results showed that efficiency and head were improved at the design condition.