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In order to meet the requirement of coal mine flooding emergency rescue, a high-power, high-head, and small-volume high-speed wet submersible pump has been designed. This article provides comparison and analysis for nine combination cases of different matching laws between the impeller blade number Z 1 ( Z 1 = 5, 6, 7) and the diffuser vane blade number Z 2 ( Z 2 = 8, 9, 10). The comparison of the pump performance and inner flow characters, such as the head, efficiency, radial force, and pressure pulsation coefficient, at different blade number matching of impeller and diffuser has been studied by the computational fluid dynamics software CFX. These are solved through the three-dimensional unsteady Reynolds-averaged Navier–Stokes equations with the shear-stress transport k–ω turbulence model. Furthermore, the computational fluid dynamics method is validated by experimental data collected in the laboratory. The results show that the combination of blade number of impeller and diffuser vane has a significant effect on the behavior. The steady analysis of combinations indicates that an increased efficiency occurs along with the reduced blade number. From the unsteady perspective, the 7+8 ( Z 1 = 7, Z 2 = 8) case has the lowest fluctuation and relatively small radial force. In conclusion, the above results can provide reference for choosing blade numbers matching law between impeller and diffuser vane of the high-speed rescue pump.

Two cleaning methods for multilayer dielectric pulse compression gratings (MDG) were studied. The first method is SPM (Sulfuric-Peroxide Mixtures, 98wt%H2SO4+30wt%H2O2) + megasonic, and the second method is Oxygen plasma + HPM (Hydrochloric/Peroxide Mixture, 37wt%HCl+30wt%H2O2+DIH2O) + megasonic. To compare the cleaning effectiveness, the element content of sample surface, diffraction efficiency, surface roughness, temperature rising and laser damage induced threshold (LIDT) were measured. The 1-on-1 LIDT of samples cleaned by the first and the second methods are 7.55 and 5.32 J/cm(2) respectively, with 1064 nm laser pulse (12 ns, s-polarized) at incidence angle of 70 degrees. In addition, the sample cleaned by the second method has lower surface contamination content, but the sample cleaned by the first method has better performance in diffraction efficiency, surface roughness and temperature rising. By further analyzing, we find that element Fe brought by oxygen plasma cleaning process in the second method is the factor that affects the damage performance and temperature rising. Therefore, the cleaning method based on the first one, the SPM + megasonic is better for improving the laser damage performance of MDG.

One of the limitations of using the pump-as-turbine (PAT) technique is its relatively narrow high-efficiency operating range. When the system pressure head or flow rate decreases, trimming the impeller or replacing the impeller with one of a smaller size is an easy and convenient approach. Therefore, research on the impeller diameter in terms of its influence on PAT is useful. To perform research on how the impeller diameter influences PAT, experimental research was first performed on a single-stage centrifugal PAT with three impellers of different diameters. Experimental results show that PAT flow versus head curve is lessened; its flow versus efficiency and flow versus power curves increased after the best-efficiency point in accordance with increasing impeller diameter. The PAT flow rate, required pressure head, generated shaft power, and efficiency at the best-efficiency point increased in accordance with increasing impeller diameter. Numerical simulation and analysis of the PAT with the three...

In order to investigate the effect of sampling frequency and time on pressure fluctuations, the three-dimensional unsteady numerical simulations were conducted in a circulating water pump. Through comparison of turbulence models with hydraulic performance experiment, SST k-ω model was confirmed to study the rational determination of sampling frequency and time better. The Fast Fourier Transform (FFT) technology was then adopted to process those fluctuating pressure signals obtained. On these bases, the characteristics of pressure fluctuations acting on the tongue were discussed. It is found that aliasing errors decrease at higher sampling frequency of 17 640 Hz, but not at a lower sampling frequency of 1 764 Hz. Correspondingly, an output frequency range ten-times wider is obtained at 17 640 Hz. Compared with 8R, when the sampling time is shorter, the amplitudes may be overvalued, and the frequencies and amplitudes of low-frequency fluctuations can not be well predicted. The frequencies at the tongue are in good agreement with the values calculated by formula and the frequency compositions less than the blade passing frequency are accurately predicted.

Insufficient understanding of the correlation between pump and pump as turbine (PAT) performance is a major problem encountered in the PAT selection and design. Therefore, establishment of accurate PAT performance prediction methods is necessary. In this paper, theoretical analysis of the relationship between pump and PAT performance was first performed. A theoretical method of predicting PAT performance is developed using theoretical analysis and empirical correlation. In the next step, computational fluid dynamics (CFD) was adopted in the direct and reverse modes performance prediction of a single stage centrifugal pump. To give a more accurate CFD result, all domains within the PAT control volume were modeled and hexahedral structured mesh was generated during CFD simulation. Complete performance curves of its pump and turbine modes were acquired. To verify the accuracy of theoretical and numerical prediction methods, the pump was manufactured and tested on a PAT open test rig. Results comparison and discussion of the theoretical, numerical and some other methods with experimental data were carried out. Eventually, relatively accurate theoretical and numerical PAT performance prediction methods were developed.

Pump manufactures normally do not provide performance curves of their pumps working as turbines, especially performance curves of trimmed impellers. Impeller trimming is necessary to adapt to a certain operating condition. Therefore, establishing the correlation of PAT’s performance curve and impeller trims is essential. In this paper, a laboratory model of a pump as turbine (PAT) open test rig was set up. Experimental research was carried out on a single stage centrifugal PAT, performance curves of original impeller, impeller after once and twice trims were acquired. Numerical simulation and analysis were performed on the PAT. The accuracy of CFD was validated through comparison between numerical and experimental data. As impeller diameter is cut down, its geometrical parameters of impeller diameter, blade wrap angle, impeller inlet width and blade inlet angle are changed. So, research on effects of the above four parameters to the performance influence of PAT were carried out using CFD. Through analysis of the predicted performance curves, the reasons for the variation of performance curves after impeller trimming were explored.

In order to balance axial forces on stamping-welding canned motor pump for safe and reliable operation, the type PBCY80-65-160 pump was selected as the computational model. Combined with various reasons why axial forces of the pump were generated, the theoretical calculation and methods of numerical simulation were chosen to analyze the size, directions and rules of axial force. At the same time, the distribution and trend of the axial force components of the impeller under different working conditions are studied whether there is the balance hole or not. The results show that, in the theoretical calculation and numerical simulation calculation, the gap and internal impact loss of the internal flow field of axial forces were neglected when the internal flow of the motor was seen as an ideal flow through the resistant elements. Hence, it could not fully represent the internal pressure distribution of the pump, which caused the calculated data a little larger than simulated data. Also, the method of combining the balance hole and impeller rear seal ring could effectively balance the axial force and extend the service life of stamping-welding canned motor pump.