Numerical investigation on the unsteady characteristics of reactor coolant pumps with non-uniform inflow

Study on the complete rotational characteristic of coolant pump in the gas-liquid two-phase operating condition

Effects of rotating speed on the unsteady pressure pulsation of reactor coolant pumps with steam-generator simulator

Investigation of the flow characteristics in a main nuclear power plant pump with eccentric impeller

Vertical inline pump is a single-stage single-suction centrifugal pump with a bent pipe before the impeller, which is usually used where installation space is a constraint. In this paper, with three objective functions of efficiencies at 0.5 Qd, 1.0 Qd, and 1.5 Qd, a multi-objective optimization on the inlet pipe of a vertical inline pump was proposed based on genetic algorithm with artificial neural network (ANN). In order to describe the shape of inlet pipe, the fifth-order and third-order Bezier curves were adopted to fit the mid curve and the trend of parameters of cross sections, respectively. Considering the real installation and computation complexity, 11 variables were finally used in this optimization. Latin hypercube sampling (LHS) was adopted to generate 149 sample cases, which were solved by CFD code ANSYS cfx 18.0. The calculation results and design variables were utilized to train ANNs, and these surrogate models were solved for the optimum design using multi-objective genetic algorithm (MOGA). The results showed the following: (1) There was a great agreement between numerical results and experimental results; (2) The ANNs could accurately fit the objective functions and variables. The maximum deviations of efficiencies at 0.5 Qd, 1.0 Qd, and 1.5 Qd, between predicted values and computational values, were 1.94%, 2.35%, and 0.40%; (3) The shape of inlet pipe has great influence on the efficiency at part-load and design conditions while the influence is slight at overload condition; (4) Three optimized cases were selected and the maximum increase of the efficiency at 0.5 Qd, 1.0 Qd, and 1.5 Qd was 4.96%, 2.45, and 0.79%, respectively; and (5) The velocity distributions of outflow in the inlet pipe of the three optimized cases were more uniform than the original one.

Multi-Objective Shape Optimization on the Inlet Pipe of a Vertical Inline Pump

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. L18 (37) 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.

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

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

The two-way counter-rotation technology is mainly applied to the tidal power station. In this paper, the hydrodynamic optimization of the two-way counter-rotating axial-flow pump turbine is carried out. Under the premise of realizing the forward and reverse power generation and the forward and negative pumping basic function, it has important engineering significance and academic value for improving the pump turbine performance of various working conditions. The main contents are as follows: hydraulic design of "S"-shaped blade for the two-way counter-rotating axial-flow pump turbine is conducted, and the influence of the gap between different impeller stages on the performance is calculated and analyzed, and the variation law of head and efficiency of the pump turbine under different inter-stage clearances is obtained. And the influence of the inter-stage gap on the unit is summarized from the vorticity distribution and the axial section pressure cloud diagram analysis, and the range of the best inter-stage gap of the unit performance is determined.

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Hydraulic Optimization of Two-Way Counter-rotating Axial Flow Pump Turbine

In this paper, CFD approach was employed to analyse the inlet and outlet pressure pulsation characteristics of reactor coolant pumps with different inflows. The Reynolds- averaged Naiver-Stokes equations with the k- 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 channel head induces the inlet flow non-uniform, and the non-uniformity of the inflow induces the outlet flow of the pump with channel head different from that of the straight pipe. Meanwhile, the pressure pulsation signals are analysed using RMS, Standard Deviation and Peak-to-Peak Value method. At the points of the inlet and outlet, the pressure pulsation characteristics between the channel head and straight pipe are compared, and the difference is obviously. It is evident that the two different inflows of channel head and straight pipe have significant effect on the pump unsteady pressure pulsation. Finally, it is expected that the effects of non-uniform inflow on the pump performance and unsteady pressure pulsation are absolutely different from the uniform inflow. It is very important to provide accurate input conditions for the design and safety of the reactor.

https://iopscience.iop.org/article/10.1088/1755-1315/49/3/032011/pdf

Long Yun

Papers

Numerical investigation on the unsteady characteristics of reactor coolant pumps with non-uniform inflow

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

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

Hydraulic Optimization of Two-Way Counter-rotating Axial Flow Pump Turbine

The Effect of the Channel Head on the Unsteady Pressure Pulsation Characteristics at the Inlet and Outlet of Reactor Coolant Pumps