Professeur de et non chercheur, Je n＇ai pas de donner unpoint de l＇Histoire de la , mais nous avons la mission de servirde relais entre la recherche et la nation pour notre enseignement. Il nous revient le dif-f...Professeur de et non chercheur, Je n＇ai pas de donner unpoint de l＇Histoire de la , mais nous avons la mission de servirde relais entre la recherche et la nation pour notre enseignement. Il nous revient le dif-ficile travail de transposer vos recherches dans des simplifications non ,la de jeunes esprits, d＇une collective familiale,展开更多
Nous savons encore peu de choses sur la place qu＇ont les femmes dansla francaise, sur leur participation aux qui ont I＇ de la France dans la . Certes quelques noms de femmes qui ont un pendant la flottent dans...Nous savons encore peu de choses sur la place qu＇ont les femmes dansla francaise, sur leur participation aux qui ont I＇ de la France dans la . Certes quelques noms de femmes qui ont un pendant la flottent dans la commune: Marie-An-toinette, Manon Rolland, Charlotte Corday etc…En les prenant pour展开更多
The mutton industry plays a pivotal role in the animal husbandry industry of Xinjiang Uygur Autonomous Region.To better monitor the volatility movement and risk warning of mutton price,the fluctuation characteristics ...The mutton industry plays a pivotal role in the animal husbandry industry of Xinjiang Uygur Autonomous Region.To better monitor the volatility movement and risk warning of mutton price,the fluctuation characteristics of mutton prices and the future trend of prices are analyzed systematically.On the one hand,the Hodrick Prescott(HP)filter method is used to analyze the long-term trends and cyclical characteristics of mutton prices in Xinjiang and explored the spatial evolution characteristics of mutton price fluctuations in various regions of Xinjiang.On the other hand,the Threshold Auto-Regressive(TAR)model is used to analyze the linkage relationship between mutton prices and the prices of other livestock products.The empirical results show that 1)the overall volatility of mutton price in Xinjiang is high,showing a trend of rising first,then falling and then rising from the temporal perspective.2)At the regional level,the price in the south is higher than that of the north,showing a decreasing trend from south to north on the whole from the spatial viewpoint.3)From the linkage relationship perspective,mutton and beef are complementary in the short term,but they are substitutes each other in the long term.This paper explores the characteristics of mutton price fluctuations in Xinjiang from the single time series of mutton prices and the linkage with other livestock products,which provides a reliable basis for the monitoring and risk warning of mutton price fluctuation.展开更多
Achieving composition tunability and structure editability of nanoalloys with high level strain may be an efficient strategy to remarkably boost catalytic performance toward oxygen evolution reaction(OER)in acidic wat...Achieving composition tunability and structure editability of nanoalloys with high level strain may be an efficient strategy to remarkably boost catalytic performance toward oxygen evolution reaction(OER)in acidic water oxidation.Herein,lotus root-like RuIr alloys with native micro-strain were constructed by an epitaxial growth of Ru-richened hcp-(0001)branches on Ir-richened fcc-(111)seeds using a polyol thermal synthesis strategy.The resultant Ru_(60)Ir_(40) alloy shows an OER overpotential of 197 mV at 10 mA cm^(-2) and a Tafel slope of 46.59 mV dec^(-1),showing no obvious activity decay for 80 h continuous chronopotentiometry test in 0.5 M H_(2)SO_(4).The related characterizations including X-ray absorption fine structure(XAFS)spectroscopy and density functional theory(DFT)calculations show that that the remarkably improved activity of the lotus root-like alloy can be attributed to the(0001)facet-triggered strain,which can efficiently optimize the electronic band structure of the active metal and the weakening of the chemisorption of oxygen-containing substances to boost OER electrocatalysis.Therefore,this work provides a new strategy to designing a class of advanced electrocatalysts with high strain using diverse nanostructures as building materials for carbon-free clean energy conversion systems.展开更多
The security of use for Al-Li alloy will be greatly influenced by the damage degree of plastic deformation within i t at high temperature . Based on continuum damage mechanics theory, the damage e volution of Al-5.4...The security of use for Al-Li alloy will be greatly influenced by the damage degree of plastic deformation within i t at high temperature . Based on continuum damage mechanics theory, the damage e volution of Al-5.44Mg-2.15Li-0.12Zr alloy during plastic deforming at high te mperature is simulated by using the damage evolution model of high temperature p lastic deformation. The changing rule of its inner damage with deformation tempe rature, strain rate and strain is gained in this paper. The equation of damage e volution for high temperature plastic deformation is developed, providing an aca demic basis for the technology of plastic process of Al-Li alloys.展开更多
With extensively using of centrifugal pumps,noise generation in these pumps is increasingly receiving research attention in recent years.The noise sources in centrifugal pumps are mainly composed of mechanical noise a...With extensively using of centrifugal pumps,noise generation in these pumps is increasingly receiving research attention in recent years.The noise sources in centrifugal pumps are mainly composed of mechanical noise and flow-induced noise.And the study of flow-induced noise has become a hotspot and important domain in the field.The flow-induced noise closely related to the inner pressure pulses and vibration of volute in pumps,therefore,it is necessary to research the interaction and mechanism among them.To investigate the relationships,a test system is designed which includes a test loop and a measurement system.The hydrophones and pressure sensors are installed on the outlet of the pump and vibration acceleration sensors are disposed on the pump body.Via these instruments,the signals of noise,pressure pulses and vibration are collected and analyzed.The results show that the level of flow-induced noise becomes smaller as the flow increment during low flow rate operations,and it is steadily close to the design point,then it increases with the growing of flow rate in high flow rate conditions.Furthermore,there are some similar peak points in the power spectrum charts of noise,pressure pulses and vibration.The broadband noise at low flow rate is mostly focused on the region of 0-40 times shaft frequency,which is mostly made by rotating stall and vortex;while the noise at high flow rate conditions is focused on the region of 60-100 times shaft frequency,which may be mostly made by cavitations.The proposed research is of practical and academic significance to the study of noise reduction for centrifugal pumps.展开更多
The annular volute is typically used in a slurry pump to reduce the collisions between solid particles and the volute tongue and to achieve a better resistance to blocking. However, only limited studies regarding annu...The annular volute is typically used in a slurry pump to reduce the collisions between solid particles and the volute tongue and to achieve a better resistance to blocking. However, only limited studies regarding annular volutes are available, and there is no systematic design method for annular volutes. In this study, the influence of volute casing cross-sectional flow area on the hydraulic loss, pressure pulsations, and radial force under varying working conditions in a centrifugal ceramic pump are discussed in detail. Experimental tests were conducted to validate the numerical results. The results indicated that, when the volute casing flow area increases, the hydraulic performance decreases marginally under the rated working conditions, but increases at the o-design points, specifically under large flow condition. However, the volute casing with a larger flow area has a wider high-e ciency region. In addition, the increase in the volute casing flow area will decrease the pressure pulsations in the volute, regardless of the working condition, and decrease the radial force on the shaft, therefore, providing an improved pump operational stability. It is anticipated that this study will be of benefit during the design of annular volutes.展开更多
A volute is a curved funnel with cross-sectional area increasing towards the discharge port.The volute of a centrifugal pump is the casing hosting the fluid being pumped by the impeller.In Pump-as-turbine devices(PAT)...A volute is a curved funnel with cross-sectional area increasing towards the discharge port.The volute of a centrifugal pump is the casing hosting the fluid being pumped by the impeller.In Pump-as-turbine devices(PAT),vice versa the volute plays the role of energy conversion element.In the present analysis,this process is analyzed using CFD.The results show that in the contraction section of volute the conversion between dynamic pressure energy and static pressure energy essentially depends on the reduction of flow area,while in the spiral section,frictional losses also play a significant role.From the throat to the end of the volute,the flow decreases in a wave-like manner.展开更多
To study the unsteady flow and related energy conversion process in the volute of a pump-as-turbine(PAT)device,six different working conditions have been considered.Through numerical calculation,the spatio-temporal va...To study the unsteady flow and related energy conversion process in the volute of a pump-as-turbine(PAT)device,six different working conditions have been considered.Through numerical calculation,the spatio-temporal variation of static pressure,dynamic pressure,total pressure and turbulent energy dissipation have been determined in each section of the volute.It is concluded that the reduction of the total power of two adjacent sections of the PAT volute is equal to the sum of the power lost by the fluid while moving from one section to the other and the power output from the two adjacent sections.For a fixed flow rate,the percentage of static pressure energy at the outlet of the PAT is roughly similar to that of the corresponding volute section,and both show a gradually increasing trend.The turbulent dissipation rate on each section of the PAT volute displays a similar a spatio-temporal behavior for different flow rates.展开更多
A high speed and small mass-flow-rate centrifugal compressor with original and modified volute tongue shape was simulated by 3D viscous Navier-Stokes equations.A sharp and a round tongue of volute were modeled to comp...A high speed and small mass-flow-rate centrifugal compressor with original and modified volute tongue shape was simulated by 3D viscous Navier-Stokes equations.A sharp and a round tongue of volute were modeled to compare their pressure ratios and efficiency characteristics.The flow fields around volute tongues were investigated;the velocity and pressure distributions of volute inlet were studied by unsteady simulation.Static pressure fluctuation near volute tongue was monitored and transformed into amplitude spectrum to identify blade passing frequency influence.The results show that the tongue simplification can cause certain difference on pressure ratio and efficiency.The pressure and velocity distribution of volute inlet indicate obvious circumferential distortion due to volute tongue especially at low mass flow rate.In addition,the static pressure pulsation of volute inlet and the noise level in diffuser and volute increase significantly under low mass flow operating condition.展开更多
In order to reduce pressure pulsation of vortex pumps,the mantis shrimp was chosen as biological prototype and a bionic engineering model was developed from its abdominal segment grooves.Bionic mantis shrimp groove vo...In order to reduce pressure pulsation of vortex pumps,the mantis shrimp was chosen as biological prototype and a bionic engineering model was developed from its abdominal segment grooves.Bionic mantis shrimp groove volute vortex pump models with different numbers of grooves were developed,and numerical simulation methods were used to calculate the models to study the effects of the volute grooves on the pressure pulsation of a vortex pump.The results show that a bionic groove volute could effectively improve the pressure pulsation of a vortex pump outlet,and reduce the pressure pulsation around the pump’s tongue and other internal points.The pressure pulsation under different conditions is impacted by shaft frequency and blade frequency.The bionic groove structure has little effect on the external characteristics of the pump,but could improve the static pressure,velocity distribution,and vortex structure of the flow field.Additionally,pressure pulsation of the whole vortex pump is reduced.展开更多
As one of the core components of turbocharger or micro-turbine, radial turbine has the features of small size and high rotation speed. In order to explore the design method and flow mechanism of the turbine with a vol...As one of the core components of turbocharger or micro-turbine, radial turbine has the features of small size and high rotation speed. In order to explore the design method and flow mechanism of the turbine with a volute, a centimeter-scale radial turbine with a vaneless air-inlet volute was designed and simulated numerically to investigate the characteristics of the coupled flow field. The results show that the wheel efficiency of single passage computation without the volute is 80.1%. After accounting for the factors of the loss caused by the volute and the interaction between each passage, the performance is more accurate according to the whole flow passage computation with the volute. High load region gathers at the mid-span and the efficiency declines to 76.6%. The performance of the volute whose structure angle of the trapezoid section is equal to 70 degree is better. Unlike uniform inlet condition in single passage, more appropriate inlet flow for the impeller is provided by the rectification effect of the volute in full passage calculation. Flow parameters are distributed more evenly along the blade span and are generally consistent between each passage at the outlet of the turbine.展开更多
Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on ...Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump＇s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics（CFD） technology is presented. Five main volute geometrical parameters D3, A8, a0, j0 and Rt are selected and 25 different volute configurations are generated by using design of experiments（DOE） method. The 3D unsteady flow numerical simulations, which are based on the SST k-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parameters D3 and A8 are major influence factors on hydrodynamic characteristics of the pump, while a0, j0 and Rt are minor influence factors. The minimum contribution from both D3 and A8 is 58% on head, and maximum contribution from both D3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect to D3/D2 and A8/A（10）, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect to D3/D2. While for the other volute parameters a0, j0 and Rt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.展开更多
The exhaust volute is a device that can change the exhaust direction of the ship’s gas turbine to reduce the flow loss of the high-temperature and high-speed turbine exhaust gas in the box-type exhaust volute,thereby...The exhaust volute is a device that can change the exhaust direction of the ship’s gas turbine to reduce the flow loss of the high-temperature and high-speed turbine exhaust gas in the box-type exhaust volute,thereby improving its power output performance.This paper first investigates the internal flow field characteristics of the exhaust volute via numerical simulation and reveals the main source of the internal resistance loss of the volute.On the premise of not affecting the installation size of the volute and matching it with other components in the cabin,the design scheme of volute bottom shunt and volute chamfer are then optimized in accordance with the flow characteristics inside the volute.Numerical simulation results show that the partial flow structure at the bottom of the volute can effectively improve the low-velocity region and the vortex flow at the bottom of the volute,and the chamfered angle scheme can control the regular expansion and compression of the airflow.When the volute adopts the appropriate chamfer angle and the bottom split-flow structure,the total pressure loss can be reduced by 19.6%,and the static pressure recovery coefficient can be increased by 42.05%.展开更多
The volute tongue can split the gas in the multi-blade centrifugal fan to make the gas flow to the volute outlet as much as possible.However,the unsteady axial deflection of the gas in the impeller results in differen...The volute tongue can split the gas in the multi-blade centrifugal fan to make the gas flow to the volute outlet as much as possible.However,the unsteady axial deflection of the gas in the impeller results in different air flow angles at the outlet of the impeller at different blade heights.This seriously affects the flow near the volute tongue.The wave leading-edge structure of humpback whale flippers has a very high flow control effect under complex flow conditions.Therefore,the wave leading-edge structure is studied in this paper and applied to the optimization design of multi-blade centrifugal fan volute tongue.First,based on the wave leading-edge structure of humpback whale flippers,three-dimensional wave leading-edge airfoils with different wave direction angles are established to judge the adaptability of the new wave leading-edge structure under different attack angles.Then,aiming at the internal flow field and noise characteristics of multi-blade centrifugal fan,a bionic volute tongue optimization design method is proposed,and studied its influence on the internal flow field and noise characteristics of the fan.The results show that when the wave direction angle is 45°,the wave leading-edge structure can effectively suppress the generation of the leading-edge separation vortex and the shedding of the wake vortex,which is also helpful to reduce the noise.The bionic volute tongue with the wave leading-edge structure can adapt to the situation that the impeller outlet air flow angle is small.At the maximum volume flow rate operating point,the static pressure recovery coefficient of the bionic volute tongue fan is increased by about 5%compared to the original fan,the air volume is increased by 5.16%,and the noise is reduced by 0.6 dB.展开更多
Hydrocyclone is widely used in closed-circuit grinding process. However, in the first classification operation of coarse particles with high pulp density, the shortcomings of traditional cyclone are that the grinding ...Hydrocyclone is widely used in closed-circuit grinding process. However, in the first classification operation of coarse particles with high pulp density, the shortcomings of traditional cyclone are that the grinding cycle load is much high, the apex of cyclone is easily to be blocked and classification efficiency is less. Specifically, the problems of traditional cyclone used in grinding process are as follows： （1） Mill utilization factor is low and its handling capacity is small; （2） Coarse particles mixing in cyclone overflow affects the following separation process and fine particles mixing in underflow causes over-grinding, which affects the total recovery rate of valuable minerals; （3） High grinding cycle load leads to large amount of high-density slurry pumping, which causes high energy consumption and severe wear of cyclones, pipelines and pumps. The applications of new type pre-classification hydrocyclone with centrifugal volute in the first classification process of iron mine mill are introduced in the paper. Pulp particles fed in the centrifugal volute are arranged in advance, so that coarse particles can be far away from the overflow pipe, which can reduce the short circuit current to avoid coarse particles entering overflow and improve classification efficiency and accuracy of cyclone. The strong points of the new cyclone in the coarse classification operation are as follows： （1） Finer overflow and less fine particles mixing in underflow improves classification efficiency more than 10%; （2） Lower ball mill load cycle improves ball capacity more than 10%; （3） Grinding energy consumption reduces by more than 20% and cyclone feed pump reduces energy consumption by more than 12%. In short, new type pre-classification cyclone with centrifugal volute solves the problems of fine particles mixing in underflow, high grinding cycle load and less classification efficiency in the coarse classification operation. Therefore, it has broad application prospects in ferrous metal and non-ferrous metal ore dressing plant.展开更多
The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possibl...The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possible, in order to reduce the pressure loss, to avoid a decrease in the effective output power and an increase of the fuel consumption rate of the internal combustion engine which indicate the inefficiency of the entire power unit;On the other hand, it requires the size of the inlet volute to be as small as possible in order to save mounting space and production costs. The thesis builds the structure model and develops flow fields numerical simulation of several different sizes of the inlet volutes. Further, the unreasonable aerodynamic structure is improved according to the flow field characteristics and thereby, a better aerodynamic performance of the inlet volute is obtained.展开更多
The geometrical parameters of impeller or volute casing (including guide vane ofmultistage pump) have a great effect on pump characteristics, but ultimately. the pump characteris-tics are determined by the geometrical...The geometrical parameters of impeller or volute casing (including guide vane ofmultistage pump) have a great effect on pump characteristics, but ultimately. the pump characteris-tics are determined by the geometrical parameters of impeller and volute casing cooperatively. Inthis essay the effect of impeller and volute casing on pump characteristics will be studiedquantitatvely from the angle cf optimal matching of them.展开更多
Numerical simulation and 3-D periodic flow unsteadiness analysis for a centrifugal pump with volute are carried out in whole flow passage, including the impeller with twisted blades, the volute and the side chamber ch...Numerical simulation and 3-D periodic flow unsteadiness analysis for a centrifugal pump with volute are carried out in whole flow passage, including the impeller with twisted blades, the volute and the side chamber channels under a part-load condition. The pressure fluctuation intensity coefficient （PFIC） based on the standard deviation method, the time-averaged velocity unsteadiness intensity coefficient （VUIC） and the time-averaged turbulence intensity coefficient （TIC） are defined by averaging the results at each grid node for an entire impeller revolution period. Therefore, the strength distributions of the periodic flow unsteadiness based on the unsteady Reynolds-averaged Navier-Stokes （URANS） equations can be analyzed directly and in detail. It is shown that under the 0.6Qd~. condition, the pressure fluctuation intensity is larger near the blade pressure side than near the suction side, and a high fluctuation intensity can be observed at the beginning section of the spiral of the volute. The flow velocity unsteadiness intensity is larger near the blade suction side than near the pressure side. A strong turbulence intensity can be found near the blade suction side, the impeller shroud side as well as in the side chamber. The leakage flow has a significant effect on the inflow of the impeller, and can increase both the flow velocity unsteadiness intensity and the turbulence intensity near the wall. The accumulative flow unstea- diness results of an impeller revolution can be an important aspect to be considered in the centrifugal pump optimum design for obtaining a more stable inner flow of the pump and reducing the flow-induced vibration and noise in certain components.展开更多
文摘Professeur de et non chercheur, Je n＇ai pas de donner unpoint de l＇Histoire de la , mais nous avons la mission de servirde relais entre la recherche et la nation pour notre enseignement. Il nous revient le dif-ficile travail de transposer vos recherches dans des simplifications non ,la de jeunes esprits, d＇une collective familiale,
文摘Nous savons encore peu de choses sur la place qu＇ont les femmes dansla francaise, sur leur participation aux qui ont I＇ de la France dans la . Certes quelques noms de femmes qui ont un pendant la flottent dans la commune: Marie-An-toinette, Manon Rolland, Charlotte Corday etc…En les prenant pour
文摘The mutton industry plays a pivotal role in the animal husbandry industry of Xinjiang Uygur Autonomous Region.To better monitor the volatility movement and risk warning of mutton price,the fluctuation characteristics of mutton prices and the future trend of prices are analyzed systematically.On the one hand,the Hodrick Prescott(HP)filter method is used to analyze the long-term trends and cyclical characteristics of mutton prices in Xinjiang and explored the spatial evolution characteristics of mutton price fluctuations in various regions of Xinjiang.On the other hand,the Threshold Auto-Regressive(TAR)model is used to analyze the linkage relationship between mutton prices and the prices of other livestock products.The empirical results show that 1)the overall volatility of mutton price in Xinjiang is high,showing a trend of rising first,then falling and then rising from the temporal perspective.2)At the regional level,the price in the south is higher than that of the north,showing a decreasing trend from south to north on the whole from the spatial viewpoint.3)From the linkage relationship perspective,mutton and beef are complementary in the short term,but they are substitutes each other in the long term.This paper explores the characteristics of mutton price fluctuations in Xinjiang from the single time series of mutton prices and the linkage with other livestock products,which provides a reliable basis for the monitoring and risk warning of mutton price fluctuation.
基金supported by the National Natural Science Funds of China(Grant number 22278016)Science and technology planning project of Yunnan Precious Metals Laboratory(Grant number YPML-2023050204)。
文摘Achieving composition tunability and structure editability of nanoalloys with high level strain may be an efficient strategy to remarkably boost catalytic performance toward oxygen evolution reaction(OER)in acidic water oxidation.Herein,lotus root-like RuIr alloys with native micro-strain were constructed by an epitaxial growth of Ru-richened hcp-(0001)branches on Ir-richened fcc-(111)seeds using a polyol thermal synthesis strategy.The resultant Ru_(60)Ir_(40) alloy shows an OER overpotential of 197 mV at 10 mA cm^(-2) and a Tafel slope of 46.59 mV dec^(-1),showing no obvious activity decay for 80 h continuous chronopotentiometry test in 0.5 M H_(2)SO_(4).The related characterizations including X-ray absorption fine structure(XAFS)spectroscopy and density functional theory(DFT)calculations show that that the remarkably improved activity of the lotus root-like alloy can be attributed to the(0001)facet-triggered strain,which can efficiently optimize the electronic band structure of the active metal and the weakening of the chemisorption of oxygen-containing substances to boost OER electrocatalysis.Therefore,this work provides a new strategy to designing a class of advanced electrocatalysts with high strain using diverse nanostructures as building materials for carbon-free clean energy conversion systems.
文摘The security of use for Al-Li alloy will be greatly influenced by the damage degree of plastic deformation within i t at high temperature . Based on continuum damage mechanics theory, the damage e volution of Al-5.44Mg-2.15Li-0.12Zr alloy during plastic deforming at high te mperature is simulated by using the damage evolution model of high temperature p lastic deformation. The changing rule of its inner damage with deformation tempe rature, strain rate and strain is gained in this paper. The equation of damage e volution for high temperature plastic deformation is developed, providing an aca demic basis for the technology of plastic process of Al-Li alloys.
基金supported by National Outstanding Young Scientists Founds of China (Grant No. 50825902)National Natural Science Foundation of China (Grant No. 50979034)+2 种基金Jiangsu Provincial Innovative Scholars "Climbing" Project of China (Grant No. BK2009006)Jiangsu Provincial Natural Science Foundation of China (Grant No. BK2009218)Priority Academic Program Development of Jiangsu Higher Education Institutions of China
文摘With extensively using of centrifugal pumps,noise generation in these pumps is increasingly receiving research attention in recent years.The noise sources in centrifugal pumps are mainly composed of mechanical noise and flow-induced noise.And the study of flow-induced noise has become a hotspot and important domain in the field.The flow-induced noise closely related to the inner pressure pulses and vibration of volute in pumps,therefore,it is necessary to research the interaction and mechanism among them.To investigate the relationships,a test system is designed which includes a test loop and a measurement system.The hydrophones and pressure sensors are installed on the outlet of the pump and vibration acceleration sensors are disposed on the pump body.Via these instruments,the signals of noise,pressure pulses and vibration are collected and analyzed.The results show that the level of flow-induced noise becomes smaller as the flow increment during low flow rate operations,and it is steadily close to the design point,then it increases with the growing of flow rate in high flow rate conditions.Furthermore,there are some similar peak points in the power spectrum charts of noise,pressure pulses and vibration.The broadband noise at low flow rate is mostly focused on the region of 0-40 times shaft frequency,which is mostly made by rotating stall and vortex;while the noise at high flow rate conditions is focused on the region of 60-100 times shaft frequency,which may be mostly made by cavitations.The proposed research is of practical and academic significance to the study of noise reduction for centrifugal pumps.
基金Supported by National Natural Science Foundation of China(Grant No.51779107)Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20170548)+1 种基金Postdoctoral Science Foundation of China(Grant No.2017M611724)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The annular volute is typically used in a slurry pump to reduce the collisions between solid particles and the volute tongue and to achieve a better resistance to blocking. However, only limited studies regarding annular volutes are available, and there is no systematic design method for annular volutes. In this study, the influence of volute casing cross-sectional flow area on the hydraulic loss, pressure pulsations, and radial force under varying working conditions in a centrifugal ceramic pump are discussed in detail. Experimental tests were conducted to validate the numerical results. The results indicated that, when the volute casing flow area increases, the hydraulic performance decreases marginally under the rated working conditions, but increases at the o-design points, specifically under large flow condition. However, the volute casing with a larger flow area has a wider high-e ciency region. In addition, the increase in the volute casing flow area will decrease the pressure pulsations in the volute, regardless of the working condition, and decrease the radial force on the shaft, therefore, providing an improved pump operational stability. It is anticipated that this study will be of benefit during the design of annular volutes.
基金Gansu province science and Technology Fund of China[Grant Nos.20JR10RA174,20JR5RA447]Open Research Subject of Key Laboratory of Fluid and Power Machinery(Xihua University),Ministry of Education[Grant Nos.LTDL2020-007,szjj2019-016]Lanzhou University of Technology Hongliu Outstanding Young Teachers Program。
文摘A volute is a curved funnel with cross-sectional area increasing towards the discharge port.The volute of a centrifugal pump is the casing hosting the fluid being pumped by the impeller.In Pump-as-turbine devices(PAT),vice versa the volute plays the role of energy conversion element.In the present analysis,this process is analyzed using CFD.The results show that in the contraction section of volute the conversion between dynamic pressure energy and static pressure energy essentially depends on the reduction of flow area,while in the spiral section,frictional losses also play a significant role.From the throat to the end of the volute,the flow decreases in a wave-like manner.
基金This work was supported by Gansu Province Science and Technology Fund of China[Grant Nos.20JR10RA174,20JR5RA447,20JR10RA203]Higher Education Industry Support Plan Project of Gansu Province of China[Grant No.2020C-20]+1 种基金Research Subject of Key Laboratory of Fluid and Power Machinery(Xihua University),Ministry of Education[Grant Nos.LTDL2020-007,szjj2019-016]Lanzhou University of Technology Hongliu Outstanding Young Teachers’Program.
文摘To study the unsteady flow and related energy conversion process in the volute of a pump-as-turbine(PAT)device,six different working conditions have been considered.Through numerical calculation,the spatio-temporal variation of static pressure,dynamic pressure,total pressure and turbulent energy dissipation have been determined in each section of the volute.It is concluded that the reduction of the total power of two adjacent sections of the PAT volute is equal to the sum of the power lost by the fluid while moving from one section to the other and the power output from the two adjacent sections.For a fixed flow rate,the percentage of static pressure energy at the outlet of the PAT is roughly similar to that of the corresponding volute section,and both show a gradually increasing trend.The turbulent dissipation rate on each section of the PAT volute displays a similar a spatio-temporal behavior for different flow rates.
基金Supported by Chinese Specialized Research Fund for the Doctoral Program of Higher Education(20091101110014)the National Natural Science Foundation of China(51176013)
文摘A high speed and small mass-flow-rate centrifugal compressor with original and modified volute tongue shape was simulated by 3D viscous Navier-Stokes equations.A sharp and a round tongue of volute were modeled to compare their pressure ratios and efficiency characteristics.The flow fields around volute tongues were investigated;the velocity and pressure distributions of volute inlet were studied by unsteady simulation.Static pressure fluctuation near volute tongue was monitored and transformed into amplitude spectrum to identify blade passing frequency influence.The results show that the tongue simplification can cause certain difference on pressure ratio and efficiency.The pressure and velocity distribution of volute inlet indicate obvious circumferential distortion due to volute tongue especially at low mass flow rate.In addition,the static pressure pulsation of volute inlet and the noise level in diffuser and volute increase significantly under low mass flow operating condition.
基金Projects(51779226,51476144)supported by the National Natural Science Foundation of ChinaProject(2017C31025)supported by Zhejiang Province Department Public Welfare Industrial Projects,China+1 种基金Project(2016M601736)supported by Postdoctoral Science Foundation of ChinaProject(1601028C)supported by Postdoctoral Research Funding Plan in Jiangsu Province,China
文摘In order to reduce pressure pulsation of vortex pumps,the mantis shrimp was chosen as biological prototype and a bionic engineering model was developed from its abdominal segment grooves.Bionic mantis shrimp groove volute vortex pump models with different numbers of grooves were developed,and numerical simulation methods were used to calculate the models to study the effects of the volute grooves on the pressure pulsation of a vortex pump.The results show that a bionic groove volute could effectively improve the pressure pulsation of a vortex pump outlet,and reduce the pressure pulsation around the pump’s tongue and other internal points.The pressure pulsation under different conditions is impacted by shaft frequency and blade frequency.The bionic groove structure has little effect on the external characteristics of the pump,but could improve the static pressure,velocity distribution,and vortex structure of the flow field.Additionally,pressure pulsation of the whole vortex pump is reduced.
基金Supported by the Innovative Research Groups of the National Natural Science Foundation of China(No.51121004)the National Natural Science Foundation of China(No.50976026)
文摘As one of the core components of turbocharger or micro-turbine, radial turbine has the features of small size and high rotation speed. In order to explore the design method and flow mechanism of the turbine with a volute, a centimeter-scale radial turbine with a vaneless air-inlet volute was designed and simulated numerically to investigate the characteristics of the coupled flow field. The results show that the wheel efficiency of single passage computation without the volute is 80.1%. After accounting for the factors of the loss caused by the volute and the interaction between each passage, the performance is more accurate according to the whole flow passage computation with the volute. High load region gathers at the mid-span and the efficiency declines to 76.6%. The performance of the volute whose structure angle of the trapezoid section is equal to 70 degree is better. Unlike uniform inlet condition in single passage, more appropriate inlet flow for the impeller is provided by the rectification effect of the volute in full passage calculation. Flow parameters are distributed more evenly along the blade span and are generally consistent between each passage at the outlet of the turbine.
基金Supported by National Natural Science Foundation of China(Grant No.51239005)Zhejiang Provincial Natural Science Foundation of China(Grant Nos.LQ15E090004,LQ15E090005)Project of Zhejiang Education,China(Grant No.Y201432222)
文摘Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump＇s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics（CFD） technology is presented. Five main volute geometrical parameters D3, A8, a0, j0 and Rt are selected and 25 different volute configurations are generated by using design of experiments（DOE） method. The 3D unsteady flow numerical simulations, which are based on the SST k-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parameters D3 and A8 are major influence factors on hydrodynamic characteristics of the pump, while a0, j0 and Rt are minor influence factors. The minimum contribution from both D3 and A8 is 58% on head, and maximum contribution from both D3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect to D3/D2 and A8/A（10）, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect to D3/D2. While for the other volute parameters a0, j0 and Rt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.
基金Supported by the National Science and Technology Major Project(No.J2019-Ⅲ-0017).
文摘The exhaust volute is a device that can change the exhaust direction of the ship’s gas turbine to reduce the flow loss of the high-temperature and high-speed turbine exhaust gas in the box-type exhaust volute,thereby improving its power output performance.This paper first investigates the internal flow field characteristics of the exhaust volute via numerical simulation and reveals the main source of the internal resistance loss of the volute.On the premise of not affecting the installation size of the volute and matching it with other components in the cabin,the design scheme of volute bottom shunt and volute chamfer are then optimized in accordance with the flow characteristics inside the volute.Numerical simulation results show that the partial flow structure at the bottom of the volute can effectively improve the low-velocity region and the vortex flow at the bottom of the volute,and the chamfered angle scheme can control the regular expansion and compression of the airflow.When the volute adopts the appropriate chamfer angle and the bottom split-flow structure,the total pressure loss can be reduced by 19.6%,and the static pressure recovery coefficient can be increased by 42.05%.
基金supported by the National Natural Science Foundation of China(11872289)“Aviation Engines and Gas Turbines”National Science and Technology Major Project Funding(J2019-IV-005-0072).
文摘The volute tongue can split the gas in the multi-blade centrifugal fan to make the gas flow to the volute outlet as much as possible.However,the unsteady axial deflection of the gas in the impeller results in different air flow angles at the outlet of the impeller at different blade heights.This seriously affects the flow near the volute tongue.The wave leading-edge structure of humpback whale flippers has a very high flow control effect under complex flow conditions.Therefore,the wave leading-edge structure is studied in this paper and applied to the optimization design of multi-blade centrifugal fan volute tongue.First,based on the wave leading-edge structure of humpback whale flippers,three-dimensional wave leading-edge airfoils with different wave direction angles are established to judge the adaptability of the new wave leading-edge structure under different attack angles.Then,aiming at the internal flow field and noise characteristics of multi-blade centrifugal fan,a bionic volute tongue optimization design method is proposed,and studied its influence on the internal flow field and noise characteristics of the fan.The results show that when the wave direction angle is 45°,the wave leading-edge structure can effectively suppress the generation of the leading-edge separation vortex and the shedding of the wake vortex,which is also helpful to reduce the noise.The bionic volute tongue with the wave leading-edge structure can adapt to the situation that the impeller outlet air flow angle is small.At the maximum volume flow rate operating point,the static pressure recovery coefficient of the bionic volute tongue fan is increased by about 5%compared to the original fan,the air volume is increased by 5.16%,and the noise is reduced by 0.6 dB.
文摘Hydrocyclone is widely used in closed-circuit grinding process. However, in the first classification operation of coarse particles with high pulp density, the shortcomings of traditional cyclone are that the grinding cycle load is much high, the apex of cyclone is easily to be blocked and classification efficiency is less. Specifically, the problems of traditional cyclone used in grinding process are as follows： （1） Mill utilization factor is low and its handling capacity is small; （2） Coarse particles mixing in cyclone overflow affects the following separation process and fine particles mixing in underflow causes over-grinding, which affects the total recovery rate of valuable minerals; （3） High grinding cycle load leads to large amount of high-density slurry pumping, which causes high energy consumption and severe wear of cyclones, pipelines and pumps. The applications of new type pre-classification hydrocyclone with centrifugal volute in the first classification process of iron mine mill are introduced in the paper. Pulp particles fed in the centrifugal volute are arranged in advance, so that coarse particles can be far away from the overflow pipe, which can reduce the short circuit current to avoid coarse particles entering overflow and improve classification efficiency and accuracy of cyclone. The strong points of the new cyclone in the coarse classification operation are as follows： （1） Finer overflow and less fine particles mixing in underflow improves classification efficiency more than 10%; （2） Lower ball mill load cycle improves ball capacity more than 10%; （3） Grinding energy consumption reduces by more than 20% and cyclone feed pump reduces energy consumption by more than 12%. In short, new type pre-classification cyclone with centrifugal volute solves the problems of fine particles mixing in underflow, high grinding cycle load and less classification efficiency in the coarse classification operation. Therefore, it has broad application prospects in ferrous metal and non-ferrous metal ore dressing plant.
文摘The structural and aerodynamic performance of the air inlet volute has an important influence on the performance of the gas turbine. On one hand, it requires the airflow flowing through inlet volute as even as possible, in order to reduce the pressure loss, to avoid a decrease in the effective output power and an increase of the fuel consumption rate of the internal combustion engine which indicate the inefficiency of the entire power unit;On the other hand, it requires the size of the inlet volute to be as small as possible in order to save mounting space and production costs. The thesis builds the structure model and develops flow fields numerical simulation of several different sizes of the inlet volutes. Further, the unreasonable aerodynamic structure is improved according to the flow field characteristics and thereby, a better aerodynamic performance of the inlet volute is obtained.
文摘The geometrical parameters of impeller or volute casing (including guide vane ofmultistage pump) have a great effect on pump characteristics, but ultimately. the pump characteris-tics are determined by the geometrical parameters of impeller and volute casing cooperatively. Inthis essay the effect of impeller and volute casing on pump characteristics will be studiedquantitatvely from the angle cf optimal matching of them.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.51239005,51009072)the National Science and Technology Pillar Program of China(Grant No.2011BAF14B04)
文摘Numerical simulation and 3-D periodic flow unsteadiness analysis for a centrifugal pump with volute are carried out in whole flow passage, including the impeller with twisted blades, the volute and the side chamber channels under a part-load condition. The pressure fluctuation intensity coefficient （PFIC） based on the standard deviation method, the time-averaged velocity unsteadiness intensity coefficient （VUIC） and the time-averaged turbulence intensity coefficient （TIC） are defined by averaging the results at each grid node for an entire impeller revolution period. Therefore, the strength distributions of the periodic flow unsteadiness based on the unsteady Reynolds-averaged Navier-Stokes （URANS） equations can be analyzed directly and in detail. It is shown that under the 0.6Qd~. condition, the pressure fluctuation intensity is larger near the blade pressure side than near the suction side, and a high fluctuation intensity can be observed at the beginning section of the spiral of the volute. The flow velocity unsteadiness intensity is larger near the blade suction side than near the pressure side. A strong turbulence intensity can be found near the blade suction side, the impeller shroud side as well as in the side chamber. The leakage flow has a significant effect on the inflow of the impeller, and can increase both the flow velocity unsteadiness intensity and the turbulence intensity near the wall. The accumulative flow unstea- diness results of an impeller revolution can be an important aspect to be considered in the centrifugal pump optimum design for obtaining a more stable inner flow of the pump and reducing the flow-induced vibration and noise in certain components.
