w. zhang

The flow field of a low specific speed centrifugal pump is investigated in the present work based on numerical simulation to establish the effect of circumferential positions of balance holes on cavitation behaviour and cavitation erosion of the centrifugal pump. The distribution of the pressure around balance holes is studied, the initiation and development of cavitation at different balance hole schemes are compared, and the distribution of cavitation erosion for the original pump and the ideal scheme is also predicted. The results show that when the NPSHa is high, there is low pressure zone in balance hole, which leads to cavitation in the pump. The cavitation performance of pump is improved by gradually moving balance holes away from blade suction surface, as this reduces low pressure zones around the balance hole and incipient cavitation. Under critical cavitation conditions, the cavitation shows a tendency to collapse as the angle (φ) of circumferential position of balance holes decreases, and the proportion of the higher vapor volume fraction in cavitation core zones also decreases. The cavitation erosion zones on blade surfaces are predicted by using the Erosive Power Method (EPM). The erosion impact of the original pump is more pronounced in the comparative results.

The risk of liquid agitation in pump-driven tanks within integrated tanks has significantly escalated due to the growing demands for tank integration in new-energy vehicles. In order to solve the problem of liquid sloshing in integrated tanks, this paper presents the design of a baffle structure aimed at reducing waves in integrated water tanks. The numerical simulation method of combining the level-set function with the volume of fluid (CLSVOF) has been employed, significantly enhancing the accuracy of numerical calculations related to a two-phase flow field inside an integrated tank. A comparison was made by analyzing different factors, notably baffle length (L), baffle depth (H), and baffle angle (θ), to investigate their influences in suppressing liquid agitation within the integrated water tank. Numerical computations were conducted utilizing design points acquired by the Latin hypercube sampling technique. The Kriging approximation modelling method was employed to hold down computing time. The Pareto solution was obtained by means of the non-dominated sorting genetic algorithm II, while the optimal solution set was evaluated and ranked using the multi-criteria decision-making algorithm (MCDM). The results show that increasing the baffle depth within a certain range can effectively suppress the wave height in the tank. When the baffle depth is increased to a certain value, the effect on wave-height suppression in the water tank is limited. When the baffle length and angle of the baffle exceed a certain value, it will also have the effect of suppressing the wave height in the tank. After comparing various factors of the baffle, it was ultimately found that the wave suppression effect is maximal when the length of the baffle is 13 millimeters, the depth of the baffle is 49 millimeters, and the angle of the baffle is -20 degrees. The main contribution of this study is the proposed wave-suppressing baffle structure, which provides new insights for the future structural design of integrated water tanks.

A numerical investigation of the particle deposition characteristics inside film holes and on the blade was conducted using an improved particle deposition model and dynamic grid updating. The computation model was numerically simulated using Reynolds-Averaged Navier-Stokes (RANS) equations with second-order spatial accuracy and the SST k-ω turbulence model, combined User Defined Function (UDF) in FLUENT 2021R1. The influence of the deposition morphology on film effectiveness was analyzed. The results revealed that a conical deposition in the exit region inside the film holes enhanced the separation of the coolant ejected from the film holes at a low coolant mass flux ratio (MFR). Increasing the MFR inhibited deposition, and the enhanced particle detachment significantly reduced particle deposition inside the film holes. Deposition downstream of the film holes significantly affected the cooling performance. Strip deposition on both sides of the region covered by the coolant limited the spanwise diffusion of the coolant. Compared to the non-deposition case, The surface-averaged film effectiveness was lower after deposition at MFRs of 0.1%-0.5% and slightly higher at MFRs of 0.6%. The most significant reduction in the surface-averaged film effectiveness after deposition was 34.9% at an MFR of 0.3%.

To determine whether and how cinobufagin regulates hepatocellular carcinoma (HCC) cell proliferation and radioresistance.

Radiosensitive (HepG2-NC) and radioresistant (HepG2-SR) HCC cells were treated with cinobufagin, X-ray ionizing radiation (IR) or a combination of cinobufagin and IR at different doses. Cell counting was performed using the Cell Counting Kit-8 assay. Key ferroptosis marker levels were determined using the indicated methods. RNA immunoprecipitation using an anti-m6A antibody followed by quantitative polymerase chain reaction was performed to determine the m6A levels in SLC7A11 mRNA.

Cinobufagin inhibited the proliferation of HepG2-NC and HepG2-SR cells. Exposure to X-rays decreased the HepG2-NC cell count in a time- and dose-dependent manner, but did not affect HepG2-SR cells. A low dose of cinobufagin did not change the cell count without IR exposure, but re-sensitized HepG2-SR cells to IR. The combination of low-dose cinobufagin and IR increased ferroptosis and decreased SLC7A11 expression levels. Mechanistically, the combination of a low dose of cinobufagin and IR decreased m6A levels in the 3' UTR of SLC7A11 in a METTL3-dependent manner.

A low dose of cinobufagin exerted synergistic effects with IR and re-sensitized radioresistant HCC cells to IR via a METTL3/m6A-dependent pathway.

The Reynolds number (Re) is an important parameter that can affect compressor performance. This study experimentally and numerically investigated the effect of Re variations on the efficiency and stall mechanisms for a three-stage axial flow compressor. In the experiment, the total pressure ratio, polytropic efficiency, and stalling mass flow rate were measured in a Re range varying from 1,100,000 to 55,000 to elucidate the Re effects. Unsteady three-dimensional numerical simulations were implemented to understand the stall mechanisms. The results indicate that the compressor efficiency and stall–pressure ratio begin to decrease remarkably as Re is reduced below a critical value, which is 220,000 in the case of the compressor studied. At a low Re, losses caused by the secondary flow near the hub and shroud increase remarkably, and the extended boundary layer separations at the blade suction surface further decrease the efficiency. The variation in Re changes the stall-initiated location. At higher Reynolds numbers, the interaction between the corner separation at the hub of stator 1 and the leakage flow through the blade tip gap induces a large vortex, which seriously blocks the blade passage. The blocking effect spreads to the aft stage and extends to higher spans, which results in the stall of the whole compressor. However, the blocking effect at the hub disappears at Re =55,000, and the interaction of the blade boundary layer separation near the shroud of rotor 1 and the tip leakage vortex causes a large blockage and then induces stall. The Re variation changes the radial flow transportation because of the varying effect on the aerodynamic performance of each blade element at different spans. This significantly influences the extent of the vortex near the end wall and ultimately changes the stall mechanisms.

For the purpose of automatic generation control (AGC), a portion of the propeller hydro-turbine units in China is adjusted to operate within a restricted range of 75%-85% load using computer-controlled AGC strategies. In engineering applications, it has been observed that when a propeller hydro-turbine unit operates under off-design conditions, a large-scale vortex rope would occur in the draft tube, leading to significant pressure fluctuations. Injecting air into the draft tube to reduce the amplitude of pressure fluctuations is a common practice, but its effectiveness has not been proven on propeller hydro-turbine units. In this study, a CFD model of a propeller hydro-turbine was established, and 15 cases with different guide vane openings (GVO, between 31° and 45°) under unsteady conditions were calculated and studied. Two air admission measures were introduced to suppress the vortex rope oscillation in the draft tube and to mitigate pressure fluctuations.  The reason for the additional energy loss due to air admission was then explained by the entropy production theory, and its value was quantified. This study points out that when injecting air, it is necessary to first consider whether the air will obstruct the flow in the draft tube. Finally, based on simulation and experimental data under various load conditions, pressure fluctuation analysis (based on fast Fourier transform, FFT) was conducted to assess the effectiveness of air admission measures. This study can provide an additional option for balancing unit efficiency and stability when scheduling units using an AGC strategy.

Ingestion and deposition of fine particles on the surface of the coolant passage degrade the blade’s cooling performance. This paper proposes a deposition model to investigate the complex deposition characteristics of fine particles during repeated collision, adhesion, rebound, and removal events in the small space inside a typical impingement-effusion structure with a double-wall blade. The results show that the particles rarely collide with the wall and escape directly from the film hole outlet when the particle diameters are smaller than 0.5 μm. Most particles with diameters of 0.5 to 1.0 μm are deposited after the first collision around the stagnation point in an area 0.35 times the pin-fin diameter. Some particles with diameters of 1.0 to 3.0 μm are deposited in the stagnation region, but most are deposited between the two pin fins and near the film hole after the second collision. Particles with diameters larger than 3.0 μm are mainly deposited on the region enclosed by the adjacent pin fins and film holes after multiple collisions, and the escape rate of particles is higher than 30%. The escape rates of particles with diameters of 0.5 to 1.0 μm and 1.0 to 3.0 μm have the same trends, exhibiting a decrease followed by an increase with the increasing particle diameter. The particles entering the impingement-effusion structure, especially those with diameters of 0.7 -0.8 μm and 1.4 -2.4 μm, are primarily deposited on the target surface, resulting in the cooling performance degradation of double-walled blade.

Multi-wing centrifugal fans are wildly used in the central air-conditioning. The influence of dimensionless clearance of the volute-tongue on aerodynamic performance and noise is studied by numerical simulation and experimental tests in this paper. The complicated internal flow related to unsteady flow in a centrifugal fan with multiple wings is investigated by numerical simulation. Besides, the influence of circumstance on the noise is analyzed. It is testified that the internal flow of centrifugal fans is ameliorated using appropriate volute tongue clearance. Reduced eddy current decreased the local-flow loss near the volute tongue and exit. The experimental results show that the static pressure of model △t/R2=0.12 rose to 7.5 Pa and the aerodynamics noise value reduced to 4 dB compared with that of a reference model. Meanwhile, an obvious reduction of aerodynamics noise by 3.74 dB is obtained for model △t/R2=0.12 installed in the air conditioning unit. The static pressure of centrifugal fan is significantly improved for the model with a cochlear tongue clearance ratio of △t/R2=0.12. It is further demonstrated that the proper dimensionless distance effectively suppresses the aerodynamic noise of forward multi-wing fans.

For diesel engines equipped with a combined spiral/tangential inlet, the main object of the valve structure and valve lift dissimilitude strategies is the valve, the changes of both will alter the motion state of the in-cylinder airflow, which has an important impact on the formation and combustion of the mixture. In order to investigate the flow performance of valve structure and valve lift dissimilitude, this paper used computational fluid dynamics (CFD) numerical simulation and multi-parameter regression methods to optimize the dual intake valve structure and obtained three valve structures with better intake performance first. Then, the optimized intake valve structure models were combined with the valve lift dissimilitude schemes to conduct steady-flow tests for the intake port. Through the reasonable combining of the two, the intake performance of the original engine was further improved. The results show that the valve structure has a relatively small influence on the intake mass, while it has a greater effect on the formation of the swirl in the cylinder, increasing the swirl ratio by 8.0%. The optimized valve structure model was combined with the valve lift dissimilitude scheme. It was found that the valve structure with optimal intake mass combined with the dissimilitude scheme of the largest valve lift of the spiral inlet could increase the flow coefficient by a maximum of 1.9%. The valve structure of the optimal swirl ratio combined with the dissimilitude scheme of the largest valve lift of the tangential inlet could increase the swirl ratio by a maximum of 9.7%. This study can guide diesel engines with combined intakes to increase the intake mass and improve the intake performance.

The steady and unsteady characteristics of the internal flow in a high-speed centrifugal blower are studied by computational fluid dynamics (CFD) approach at low flow rates. It is demonstrated that as the flow rate decreases, the separation of flow in the blade passage becomes serious, and separated vortexes always occur on the suction surface of the blade which gradually expand and block the passage. The stall cells move downstream and generate vortices at the exit of the passage, resulting serious loss to the performance of the blower. Q-criteria is used to analyze the flow field and explore the evolution of the vortex structure in the impeller. It is further found that strong pressure fluctuations are caused by the rotating stall in the impeller. At the stall conditions, the instability characteristics are particularly obvious. At flow rates of 0.65Qn and 0.47Qn, the pressure fluctuation in the blade passage is dominated by the blade passing frequency, while a lower frequency dominates at 0.26Qn. Moreover, the flow on the suction surface of impeller blades fluctuates substantially. The characteristics of steady flow and unsteady flow can clearly explain the internal flow of centrifugal blower for vacuum cleaners at low-flow conditions, which can be widely used in various engineering designs of vacuum cleaners.

This research was performed to analyze the relationship among the physical factors of cervical cancer patients and the V40-x (volume of the x receiving 40 Gy, x is replaced by bladder or rectum below). In addition, the methods to control the factors affecting these related physical parameters are comprehensively discussed so that the side effects of radiotherapy can be reduced.

Sixty cervical cancer patients treated with volume-modulated-arc therapy (VMAT) were selected. Related physical parameters of the planning target volume (PTV), rectum, and bladder were collected. The Spearman analysis method was used to discuss the relationship between the physical parameters and V40-x.

The parameter of Dmax-rectum (max dose of rectum) and Vbladder (volume of the bladder) were significantly negatively correlated with V40-rectum and V40-bladder, respectively. In addition, we found three dosimetric parameters and four parameters were significantly positively correlated with V40-rectum and V40-bladder. A reduction in V40-x of the organs at risk (OARs) was also displayed in the redesigned planning dose images and the dose-volume histograms (DVH).

It is recommended that patients maintain a filled bladder during localization and radiotherapy. It is also recommended that patients maintain an empty rectum during localization and radiotherapy to ensure the stability of the target. According to the correlation of the physical parameters obtained from the results, medical physics can reduce the V40-x more easily during planning design by specifically controlling some physical parameters, and this can reduce radiation toxicity more effectively.

This study describes the large eddy simulations of a centrifugal pump impeller considering a sinusoidal flow rate and a constant rotation speed. Five different oscillation amplitudes of flow rate (A = 0.1Qd, 0.15Qd, 0.2Qd, 0.25Qd, and 0.3Qd, Qd indicates the design flow rate) are selected to determine the influence of oscillation amplitude on the internal flow characteristics. The simulation results show that, with increasing oscillation amplitude, the alternating stall phenomenon weakens or even disappears during the dropping stage, whereas the opposite trend is observed during the rising stage. The total mean normal vorticity is insensitive to changes in the oscillation amplitude. Moreover, the difference in pressure fluctuations between adjacent passages decreases with increasing oscillation amplitude. The first and second dominant frequencies of the pressure fluctuations are mainly affected by the oscillation amplitude in the non-stall passage. The internal flow exhibits a clear hysteresis effect, and the lag time of the head increases with the oscillation amplitude. Additionally, the average head is approximately 2.38 m, regardless of the oscillation amplitude.

The present study aims to describe characteristics of cavitation during the startup process of a condensate pump. The pump is featured by an impeller equipped with five splitter blades. A computational fluid dynamics (CFD) work was conducted to plumb the evolution of cavitation in the pump. Effect of the volumetric flow rate on instantaneous cavitation patterns as the rotational speed of the pump increased was analyzed. The results show that high resistance to cavitation of the pump depends greatly on large area of the impeller eye, which is related to the deployment of the splitter blades. The splitter blades are insignificantly affected by cavitation. During the startup process, both the pump head and the pump efficiency vary drastically, which is insensitive to the flow rate. At a net positive suction head (NPSH) of 2.0 m, high flow rates are responsible for intensified cavitation. High volume fraction of cavitation arises near the inlet of long blades. As the rotational speed increases, the evolution of cavitation is featured by intermittency and diversified cavity patterns. Furthermore, the sum of the volume fraction of cavitation fluctuates with continuously increasing rotational speed.

Numerical simulation was used to investigate the effect of an inclined volute tongue on the complex flow characteristics and the aerodynamic performance of multi-blade centrifugal fans. We focused on the effects of the clearance, the inclination angle and the volute tongue’s on controlling the centrifugal fan’s internal flow characteristics and aerodynamic performance. The results showed that the volute tongue’s reasonable clearance ratio and the inclined volute tongue design were beneficial to improving the flow pattern around the volute tongue and volute outlet of the centrifugal fan, as well as reducing the local flow loss. It is of great significance to increase the centrifugal fan’s static pressure and related efficiency by increasing the radius and inclination angle of the volute tongue. Due to the reduced of vortex, the local flow loss was reduced. Numerical results indicated that model C’s static pressure rose to 12.5Pa, and the related static-pressure efficiency of to 3.8% compared with the reference geometry due to the reduced of flow loss.

Aiming at better controlling the ventilated supercavity flow for drag reduction, the experimental and numerical researches of supercavity by rear gas reflux are proposed in this paper. Several experiments with different test bodies have been carried out to study the formation and collapse conditions of jet-reflux supercavity. An open-circulation water tunnel for ultra-high-speed jet experiment and air jet system is employed to form jet-reflux supercavity around the bodies installed in the forward strut. The experiment results show that the supercavity can be maintained by the reflux of tail jet flow when an initial supercavity covering the jet outlet is formed. However, the supercavity will be destroyed when the jet intensity is further enhanced. Under the same jet coefficient, the scale of jet-reflux supercavity extends as the increase of the body length, while the critical jet coefficient for the collapse of the supercavity decreases as the increase of the body length. The multiphase flow model coupling the VOF model and the level-set method is applied to capture the air-water interface. Then, the flow field characteristics of the jet-reflux supercavity are analyzed and compared with the ventilated supercavity. The streamline inside the cavity presents considerable three-dimensional asymmetry inflating flow characteristics. The variation of the gas reflux coefficient along the axial direction is obtained, which indicates that a handful of reflux gas are required to sustain the head cavity. Therefore, the jet-reflux supercavity can be formed within a certain range of the tail jet intensity. Although jet intensities are not equal to each other, the scale of cavity head is roughly maintained under the same reflux coefficient. When the supercavity gets closed to the nozzle outlet, the maximum scale of cavity is decreased, which leads to a weaker reflux at the outlet. The cavity interface will be impinged by the high-speed gas and mixture liquid, which obviously causes deformation and final collapse. In order to improve the stability of the jet-reflux supercavity, it is necessary to use the gas re-directed structure to control the reflux.

To retrospectively evaluate whether quantitative information derived from spectral imaging can improve the differential diagnosis of pancreatic cystic masses including pancreatic solid pseudopapillary epithelial neoplasms (SPENs), mucin- producing cysts and pseudocysts.

From June 2015 to October 2017, 56 patients (22 pseudocysts, 18 mucin-producing cysts and 16 SPENs) who underwent spectral CT imaging were included in the study. Conventional characteristics and quantitative parameters were compared among the three groups. The receiver-operating characteristic curve was used to evaluate the diagnostic performance of parameters which had statistical significance among the three groups. Two radiologists diagnosed the pancreatic cystic masses blinded in consensus, without and with the information of the statistical analysis.

The conventional characteristics including age, contour, nodule and septum were the independent factors correlated with category. The quantitative parameters including effective-Z, slope of energy spectral curve (slope), iodine (water) concentration and calcium (water) concentration demonstrated significantly lower values in pseudocysts group when compared with mucin-producing cysts and SPENs groups. Slope in portal venous phase, threshold of less than 0.50, was the best discriminator between pseudocysts group and mucin-producing cysts group, with a sensitivity of 95.5%, and a specificity of 88.9%. The best quantitative parameter for differentiate SPENs from mucin-producing cysts was the iodine (water) concentration in portal venous phase. With the knowledge of statistical analysis, the accuracy of the two radiologists increased from 78.5% to 90.9%.

Multi-parametric analysis with the combination of quantitative parameters derived from CT spectral imaging could improve the diagnostic performance.

The design of intensity modulated radiation therapy (IMRT) plans is difficult and time-consuming. The retrieval of similar IMRT plans from the IMRT plan dataset can effectively improve the quality and efficiency of IMRT plans and automate the design of IMRT planning. However, the large IMRT plans datasets will bring inefficient retrieval result.

An intensity-modulated radiation therapy (IMRT) plan clustering method based on k-means algorithm and geometrical features is proposed to improve the retrieval efficiency from the IMRT plan dataset. The proposed method could benefit future automatic IMRT planning based on prior knowledge. In this study, a collection dataset including 100 cases of nasopharyngeal carcinoma IMRT plans was employed in the clustering experiment. The geometrical features of each cluster center were used to qualitatively predict the dosimetric characteristics of organs at risk (OARs) and compared with practical results.

Experimental results demonstrate that the tested dataset can be well clustered using the proposed method. The predicted dosimetric characteristics of OARs for each cluster agree well with their practical results, and the difficulty of IMRT planning for each cluster can be derived.

The proposed IMRT plan clustering method can bring great benefit to the new cases of IMRT planning.