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In order to study the influence of the circumferential position of the balance hole on the cavitation performance of the semiopen impeller centrifugal pump, a low specific speed semiopen impeller centrifugal pump is taken as the object, and 4 kinds of circumferential positions of balance holes are designed. The SST k-ω turbulence model and the Rayleigh–Plesset cavitation bubble dynamics equation are used to calculate the full flow field of the centrifugal pump. Research shows that, under cavitation conditions, as the circumferential position of the balance hole is farther away from the blade working surface, the cavitation performance of the pump is reduced, and the larger θ (the angle of the balance hole and the leading edge of the blade in the direction of rotation) is, the easier the jet cavitation occurs near the balance hole. On the other hand, with the development of cavitation, the axial force of the impeller has also changed greatly. In contrast, the farther the balance hole is arranged in the circumferential direction (i.e., the greater θ), the more limited is the ability of the balance hole to balance the axial force.

In this paper, the influence of the specific area of balancing hole on the cavitation performance of high-speed centrifugal pump is studied by numerical method. The results show that in the initial cavitation stage, with the increase of the specific area, the head and efficiency of the pump decreases, and the shaft power increases in a small range. The specific area of the balance hole can change the magnitude and direction of the rotor axial force. With the increase of the specific area, the anti-cavitation performance of the pump is weakened, especially when the specific area reaches a certain value, the vortex flow appears in the balance hole, which causes serious distortion of the flow condition at the inlet of the centrifugal impeller. Meanwhile, cavitation also occurs in the balance chamber and is mainly concentrated near the hub of the centrifugal impeller.

In order to study the influence of the circumferential placement position of the guide vane on the flow field and stress-strain of a nuclear reactor coolant pump, the CAP1400 nuclear reactor coolant pump is taken as the research object. Based on numerical calculation and test results, the influence of circumferential placement position of the guide vane on the performance of the nuclear reactor coolant pump and stress-strain of guide vanes are analyzed by the unidirectional fluid-solid coupling method. The results show that the physical model and calculation method used in the study can accurately reflect the influence of the circumferential placement position of the guide vane on the nuclear reactor coolant pump. In the design condition, guide vane position has a great influence on the nuclear reactor coolant pump efficiency value, suction surface of the guide vane blade, and the maximum equivalent stress on the hub. However, it has a weak effect on the head value, pressure surface of the guide vane blade, and the maximum equivalent stress on the shroud. When the center line of the outlet diffuser channel of the case is located at the center of the outlet of flow channel of the guide vane, it is an optimal guide vane circumferential placement position, which can reduce the hydraulic loss of half of the case. Finally, it is found that the high stress concentration area is at the intersection of the exit edge of the vane blade and the front and rear cover, and the exit edge of the guide vane blade and its intersection with the front cover are areas where the strength damage is most likely to occur. This study provides a reference for nuclear reactor coolant pump installation, shock absorption design, and structural optimization.

According to the design requirements of a booster centrifugal pump, the full three-dimensional numerical calculation of the model pump is carried out based on the RNG k-ɛ turbulence model and the Rayleigh–Plesset cavitation model to analyze the influence of the axial matching of the inducer and the suction chamber (i.e. the degree of the axial extension of the inducer into the suction chamber) on the cavitation performance of the centrifugal pump. Five sets of centrifugal pump design schemes were selected respectively with the ratio of the axial direction of the inducer into the suction chamber and the axial distance of the inducer hub were 0 (original scheme), 1.6%, 3.2%, 4.8%, and 6.4% to compare the distribution of axial static pressure of the inducer and the suction chamber, the variation of cavitation characteristics, head (energy of a fluid per unit weight obtained by working with a pump expressed in the form of height) and efficiency of the centrifugal pump, the distribution of bubbles in the inducer and the impeller, and the static pressure distribution law of the inducer in the runner. According to the results, what are illustrated are that the cavitation performance of the centrifugal pump can be improved by inserting the inducer into the suction chamber to a certain extent, and the cavitation performance is better with the increase of the axial indentation degree, but it tends to be stable after reaching a certain degree. At the same time, it was found that the vapor bubbles in the inducer and the impeller first appeared in the low pressure region at the inlet rim of the blade.

To suppress the cavitation instability caused by the leakage vortex at the tip clearance of the high-speed inducer, this study establishes a structure (i.e., annular groove) at the upstream boundary of the high-speed inducer that can absorb the leakage vortex, and 6 sets of design projects are determined, including the initial plan and the axial distance of 0 mm, 2.5 mm, 5 mm, 7.5 mm, and 10 mm, respectively. The effects of annular grooves on cavitation performance under different schemes are studied through a combination of experiment and numerical calculation. The results show that cavitation tends to occur at the position where the leading edge of the suction surface of the inducer intersects the shroud and the bubbles volume is distributed in gradient. Vortex belt is formed at the inlet of the inducer. The axial position of the annular groove relative to the inducer is an important parameter suppressing the occurrence of clearance leakage vortex cavitation, asymmetric vortex cavitation and rotating vortex cavitation. In the proper position, annular groove can significantly suppress the bubbles incipient and improve the cavitation performance of the inducer. It can improve the head of the centrifugal pump effectively under the condition of little effect on centrifugal pump efficiency. However, at other positions, the annular groove cannot improve the cavitation performance of the centrifugal pump, indicating the annular groove has an axial optimal position in inhibiting cavitation and improving cavitation performance of the inducer, at this time $${\mathrm{L}}_{1}=0$$ mm.

In order to study the effects of inlet sweepback angle on the cavitation performance of inducers based on the Reynolds N-S equation, RNG k-ε turbulent model, and Schnerr and Sauer cavitation model, a three-dimensional numerical calculation is employed to study the flow characteristics of a certain LNG pump. Laws of the variation of cavitation performance, head, and efficiency with the change of sweepback were studied. Numerical analysis of the eight inducer projects with a sweepback angle from 120° to 290° was carried out. The results show that the cavitation bubbles first appear at the suction surface near the inlet side. With the decrease of net positive suction head (NPSHa), the bubbles spread to the outlet side of the inducer and the pressure surface. Finally, they fill the entire channel. When the inducer sweepback angle increases from 120° to 270°, the NPSHr of the pump reduces gradually, that is to say that the anti-cavitation performance of the pump has been improved. However, the NPSHr of the pump increases gradually when the inducer sweepback angle increases from 270° to 290°. In other words, there is an optimal sweepback from 120° to 290°, and efficiency and head of pump tend to be stable near the optimal sweepback.

To study the effect of the dip angle of the inducer blade section in the meridian plane on the cavitation performance of the high-speed centrifugal pump, four schemes of the inducer have been considered only by changing the dip angle of the blade section in the meridian plane while keeping the other geometrical parameters unchanged. Based on the RNG k–ɛ turbulence model and Zwart-Gerber-Belamri cavitation model, three-dimensional numerical simulation of a high-speed centrifugal pump is carried out. The results show that the cavitation performance of high-speed centrifugal pump will be improved when the dip angle of the blade section in the meridian plane increases within a certain range, but the cavitation performance will deteriorate when the dip angle exceeds a certain extent. A moderate raise of the blade section dip angle will change the blade inlet angle and blade outlet angle of the shroud and hub of the inducer, improve the matching of the liquid flow angle with the blade inlet angle and restrain the cavitation at the blade leading edge. The change in the dip angle has a weak influence on the external performance of the high-speed centrifugal pump, indicating that there is almost no effect on the capacity of the inducer.

In order to study the relationship between the cavitation flow and energy conversion, based on the continuity equation, Renault N-S equation and RNG k-ε turbulence model, the whole flow field cavitation numerical simulation on unclear main pump model under design condition is carried out. Through the variation of pressure and velocity on the streamlines, combined with the basic equation of the pump, the dynamic and hydrostatic head of the nuclear main pump under different cavitation conditions are studied. The results show that the energy of fluid of nuclear main pump is provided by posterior segment of impeller, and the energy of the fluid decreases gradually from the shroud to the hub. Cavitation interferes with the flow of liquid in the impeller, which leads to the relative velocity increases and the pressure decreases in cavitation region, and the work capacity of blades is almost zero in bubble areas. At the same time, in non-cavitation region along with streamlines the dynamic head increases and the hydrostatic head decreases with the development of cavitation, and the decrease of the hydrostatic head is greater than the increase of the dynamic head, which results in the decrease of pump head and efficiency. In addition, in the cavitation region, with the development of cavitation, the sudden change of the dynamic and hydrostatic head increases, which increase the flow loss in the impeller and results in the decrease of pump head and efficiency moreover.

Based on the Reynolds-averaged Navier–Stokes equations of relative coordinates and the RNG k-ε turbulence model, using our SIMPLE algorithm, we performed numerical simulations for an AP1000 nuclear main pump model with water as the medium. By changing the size of the tongue blend in the annular casing, seven different schemes were designed. Three-dimensional numerical simulations were conducted for the flow within the pump under various settings, and the flow characteristics of the annular casing using different tongue blends were obtained. The results show that for different operating conditions, there is a specific tongue blend that optimizes pump performance. Based on the calculation results, a larger tongue blend leads to a larger flow rate. Off-design conditions caused flow instability, which in turn caused the tongue blend to have a certain impact on the performance of the impeller. However, the performance of the pump was not primarily affected by changes in the impeller performance, but was instead affected by the performance of the annular casing, which was itself affected by tongue blend. When changing the tongue blend, the change in static pressure and total pressure of the annular casing was larger under the condition of 0.6 Qd and was smaller under the conditions of 1.0 Qd and 1.4 Qd. The turbulent kinetic energy in the annular casing changed mainly in the tongue impact zone and outlet diffuser under the condition of 1.0 Qd; furthermore, the turbulent kinetic energy in the whole of the annular casing demonstrated significant changes under the conditions of 0.6 Qd and 1.4 Qd.