In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-b...In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-based alloy(typically pure lead or lead-bismuth eutectic(LBE))is used as the coolant.To clarify the pressure build-up characteristics under water-jet injection,this study conducted several experiments by injecting pressurized water into a molten LBE pool at Sun Yat-sen University.To obtain a further understanding,several new experimental parameters were adopted,including the melt temperature,water subcooling,injection pressure,injection duration,and nozzle diameter.Through detailed analyses,it was found that the pressure and temperature during the water-melt interaction exhibited a consistent variation trend with our previous water-droplet injection mode LBE experiment.Similarly,the existence of a steam explosion was confirmed,which typically results in a much stronger pressure build-up.For the non-explosion cases,increasing the injection pressure,melt-pool temperature,nozzle diameter,and water subcooling promoted pressure build-up in the melt pool.However,a limited enhancement effect was observed when increasing the injection duration,which may be owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steam cavity.Regardless of whether a steam explosion occurred,the calculated mechanical and kinetic energy conversion efficiencies of the melt were relatively small(not exceeding 4.1%and 0.7%,respectively).Moreover,the range of the conversion efficiency was similar to that of previous water-droplet experiments,although the upper limit of the jet mode was slightly lower.展开更多
In order to solve the deformation of the hydrostatic thrust bearing with multi-pad annular recess in the heavy computer numerical control （ CNC ） equipment, the simulation concerning pressure feld of hydrostatic thr...In order to solve the deformation of the hydrostatic thrust bearing with multi-pad annular recess in the heavy computer numerical control （ CNC ） equipment, the simulation concerning pressure feld of hydrostatic thrust bearing with multi-pad annular recesses was carded out. The finite volume method of computational fluid dynamics （ CFD ） was used to compute the three-dlmensional pressure field of gap fluid between the rotary worktable and the base. The influence of the rotational speed on the bearing pressure performance was studied based on CFD and lubrication theory, and the method revealed the pressure distribution law. The results qualitatively agree well with the experimental data. The results indicate that the oil cavity pressure decreases gradually with rotational speed enhancing. The reliability of a hydrostatic thrust bearing with malti-pad annular recess can be predicted through this method, and the optimal design of such products can be achieved, and the numerical simulation method can provide reasonable data for design, lubrication, experiment, and deformation computation of hydrostatic thrust bearing in the heavy CNC equipment.展开更多
A compact annular-radial-orifice flow magnetorheological(MR)valve was developed to investigate the effects of radial resistance gap on pressure drop.The fluid flow paths of this proposed MR valve consist of a single a...A compact annular-radial-orifice flow magnetorheological(MR)valve was developed to investigate the effects of radial resistance gap on pressure drop.The fluid flow paths of this proposed MR valve consist of a single annular flow channel,a single radial flow channel and an orifice flow channel through structure design.The finite element modelling and simulation analysis of the MR valve was carried out using ANSYS/Emag software to investigate the changes of the magnetic flux density and yield stress along the fluid flow paths under the four different radial resistance gaps.Moreover,the experimental tests were also conducted to evaluate the pressure drop,showing that the proposed MR valve has significantly improved its pressure drop at 0.5 mm width of the radial resistance gap when the annular resistance gap is fixed at 1 mm.展开更多
High pressure is an important development orientation in pneumatic field,since it can not only improve dynamic characteristics of pneumatic system but also decrease the size of components and mounting space.Due to the...High pressure is an important development orientation in pneumatic field,since it can not only improve dynamic characteristics of pneumatic system but also decrease the size of components and mounting space.Due to the advantages of high energy density and high instant expansibility,high pressure gas has been widely used in many applications.However,systematic researches are lacked especially in pressure characteristics which are very important in pneumatic system at present.In a high pressure pneumatic system,the pressure of a fixed cavity with annular clearance needs to be controlled within a wide range,so a single stage proportional slide valve is proposed to satisfy the requirements of high pressure and low flow rate.First,working principle and structure of the pressure assembly and the slide valve are introduced.Then mathematical model of the high pressure pneumatic system is built up;controllable pressure range is simulated,and influence of uncertain factors,such as fit clearance of the pressure valve and the cavity on controllable pressure,is discussed.Finally,a test bench of the pressure assembly is built up,and the controllable pressure and step response experiments are carried out.Both simulation and experimental results show that the designed slide valve can satisfy the requirements well.The proposed clearance presumption method based on simulation and experimental results is valuable for indirect measurement of processing tolerance.展开更多
The title problem is systematically analyzed by the differential quadrature (DQ) method. Estimates of the critical buckling loads are obtained for combinations of various boundary conditions, internal and/or external ...The title problem is systematically analyzed by the differential quadrature (DQ) method. Estimates of the critical buckling loads are obtained for combinations of various boundary conditions, internal and/or external Pressures, hole sizes,and rigidity ratios. A comparison is made with existing results for certain cases. Numerical investigation has been carried out with regard to the convergence of the solutions. It is found that accurate results are obtained with only nine or eleven grid points.展开更多
Background: There is no single noninvasive index that provides a direct measure of LV filling pressure. However, invasive measuring of LV end diastolic pressure (LVEDP) provides reliable assessment of LV diastolic dys...Background: There is no single noninvasive index that provides a direct measure of LV filling pressure. However, invasive measuring of LV end diastolic pressure (LVEDP) provides reliable assessment of LV diastolic dysfunction, but its invasive nature limits its use in daily practice. Accurate noninvasive assessment of LV diastolic dysfunction is highly desirable, and the relationship between the degree of LVEDP and acceleration of E’ wave obtained by tissue Doppler imaging (TDI) of mitral annulus is not clearly assessed;here in our study we aimed to assess the relation between the degree of LVEDP and the acceleration rate of E’ wave of mitral annular Doppler tissue. Patients and Methods: The study included 60 patients divided equally into 3 groups according to the degree of LVEDP, group I (Normal): ’ ratio and E’ wave acceleration rate. Coronary angiography and left sided heart catheterization and measuring LVEDP were performed for correlating E’ wave acceleration rate with invasively estimated LVEDP.?Results: There was significant progressive decrease in E’ acceleration rate (E’ Acc rate) with progressive increase in LVEDP from I to III (P 0.001), while there was significant progressive increase in E/E’ ratio with progressive increase in LVEDP from I to III (P 0.003). Peak E’ acceleration rate had a significant negative correlation with LVEDP in all three groups, with p value of 0.003, 0.044 and 0.021 respectively in group I, II & III. Regarding E/E’ ratio there was a significant positive correlation in predicting normal and elevated LVEDP with p value (0.001 and 0.006) respectively while there was a non-significant correlation between E/E’ and LVEDP within grey zone group. Conclusion: E’ acceleration rate could be used as a reliable index to assess LVEDP.展开更多
Surge pressure caused by pipe moving through the wellbore full of drilling.fluid is the main factor affecting wellbore stability,on which the additional mud density isdesigned.Thus if is desired to predict the surge p...Surge pressure caused by pipe moving through the wellbore full of drilling.fluid is the main factor affecting wellbore stability,on which the additional mud density isdesigned.Thus if is desired to predict the surge pressure with high accuracy.While this is closely,related with the selection of mud rheological models.Yield-Pseudoplastic model which has three parameters and is.famous for its higher accuracy has been used to describe the mud rheological properties in recent years.Based on this model the paper presents a new theoretical model for calculating surge pressure caused by mud viscosity during tripping or casing in a concentric annulus of directional wells under steady laminar situation.For convenience,the paper plots the distribution of the coefficients of surge pressure for different conditions.An example is given.These results provide the basis for controlling pressure surges and tripping velocity.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
The perturbation method is used to solve the control equations of a three-dimensional annular flow inside a small gap. The nonlinear equations are separated into zeroth-order and first-order perturbation equations. Th...The perturbation method is used to solve the control equations of a three-dimensional annular flow inside a small gap. The nonlinear equations are separated into zeroth-order and first-order perturbation equations. The velocity and pressure distributions are solved successively by different numerical methods with the zeroth-order and first-order equation. Agreement in results is found with the present method and software ANSYS-CFX, which illustrates the applicability of perturbation method in solving complicated flow field inside small gaps.展开更多
Transient change of the operating parameters has a serious influence on the stability of liquid annular seals.Take the liquid annular seals as a research object,a numerical method based on six-degree-of-freedom(6DOF)t...Transient change of the operating parameters has a serious influence on the stability of liquid annular seals.Take the liquid annular seals as a research object,a numerical method based on six-degree-of-freedom(6DOF)to analyze the dynamic response of liquid annular seals under gravity impact load.The variations of the force of liquid seal and pressure as well as the axis trajectory in time history are investigated.The influence of different sealing clearance,different liquid viscosity and different rotor speed is also studied.The results show that the maximum sealing pressure and sealing force of gravity direction will increase greatly in a very short time and then reduce rapidly.When sealing clearance increases,the displacement response amplitudes of axis trajectory,the maximum sealing force of gravity direction and maximum sealing pressure also increase.When liquid viscosity increases,the displacement response amplitudes of axis trajectory,the maximum sealing force of gravity direction and maximum sealing pressure decrease.We also found that different rotor speed has almost no influence on the maximum sealing force of gravity direction and maximum sealing pressure.展开更多
基金supported by Basic and Applied Basic research foundation of Guangdong province(Nos.2021A1515010343 and 2022A1515011582)the Science and Technology Program of Guangdong Province(Nos.2021A0505030026 and 2022A0505050029).
文摘In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-based alloy(typically pure lead or lead-bismuth eutectic(LBE))is used as the coolant.To clarify the pressure build-up characteristics under water-jet injection,this study conducted several experiments by injecting pressurized water into a molten LBE pool at Sun Yat-sen University.To obtain a further understanding,several new experimental parameters were adopted,including the melt temperature,water subcooling,injection pressure,injection duration,and nozzle diameter.Through detailed analyses,it was found that the pressure and temperature during the water-melt interaction exhibited a consistent variation trend with our previous water-droplet injection mode LBE experiment.Similarly,the existence of a steam explosion was confirmed,which typically results in a much stronger pressure build-up.For the non-explosion cases,increasing the injection pressure,melt-pool temperature,nozzle diameter,and water subcooling promoted pressure build-up in the melt pool.However,a limited enhancement effect was observed when increasing the injection duration,which may be owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steam cavity.Regardless of whether a steam explosion occurred,the calculated mechanical and kinetic energy conversion efficiencies of the melt were relatively small(not exceeding 4.1%and 0.7%,respectively).Moreover,the range of the conversion efficiency was similar to that of previous water-droplet experiments,although the upper limit of the jet mode was slightly lower.
基金National Natural Science Foundations of China(No.51075106,No.51005063,No.50975066)Technology Items of Heilongjiang Provincial Education Department,China(No.12511087,No.12521096,No.12511086,No.12511088,No.11551080,No.12521119)+1 种基金Projects of the Special Fund on the Science and Technology Innovation People of Harbin,China(No.2012RFQXG077)the 2012 National College of Innovative Pilot Project,China(No.201210214027)
文摘In order to solve the deformation of the hydrostatic thrust bearing with multi-pad annular recess in the heavy computer numerical control （ CNC ） equipment, the simulation concerning pressure feld of hydrostatic thrust bearing with multi-pad annular recesses was carded out. The finite volume method of computational fluid dynamics （ CFD ） was used to compute the three-dlmensional pressure field of gap fluid between the rotary worktable and the base. The influence of the rotational speed on the bearing pressure performance was studied based on CFD and lubrication theory, and the method revealed the pressure distribution law. The results qualitatively agree well with the experimental data. The results indicate that the oil cavity pressure decreases gradually with rotational speed enhancing. The reliability of a hydrostatic thrust bearing with malti-pad annular recess can be predicted through this method, and the optimal design of such products can be achieved, and the numerical simulation method can provide reasonable data for design, lubrication, experiment, and deformation computation of hydrostatic thrust bearing in the heavy CNC equipment.
基金Supported by the National Natural Science Foundation of China(51765016,51475165,11462004)the Jiangxi Provincial Foundation for Leaders of Academic and Disciplines in Science(20162BCB22019)5511 Science and Technology Innovation Talent Project of Jiangxi Province(20165BCB18011)
文摘A compact annular-radial-orifice flow magnetorheological(MR)valve was developed to investigate the effects of radial resistance gap on pressure drop.The fluid flow paths of this proposed MR valve consist of a single annular flow channel,a single radial flow channel and an orifice flow channel through structure design.The finite element modelling and simulation analysis of the MR valve was carried out using ANSYS/Emag software to investigate the changes of the magnetic flux density and yield stress along the fluid flow paths under the four different radial resistance gaps.Moreover,the experimental tests were also conducted to evaluate the pressure drop,showing that the proposed MR valve has significantly improved its pressure drop at 0.5 mm width of the radial resistance gap when the annular resistance gap is fixed at 1 mm.
基金supported by National Natural Science Foundation of China(Grant No.50575202)
文摘High pressure is an important development orientation in pneumatic field,since it can not only improve dynamic characteristics of pneumatic system but also decrease the size of components and mounting space.Due to the advantages of high energy density and high instant expansibility,high pressure gas has been widely used in many applications.However,systematic researches are lacked especially in pressure characteristics which are very important in pneumatic system at present.In a high pressure pneumatic system,the pressure of a fixed cavity with annular clearance needs to be controlled within a wide range,so a single stage proportional slide valve is proposed to satisfy the requirements of high pressure and low flow rate.First,working principle and structure of the pressure assembly and the slide valve are introduced.Then mathematical model of the high pressure pneumatic system is built up;controllable pressure range is simulated,and influence of uncertain factors,such as fit clearance of the pressure valve and the cavity on controllable pressure,is discussed.Finally,a test bench of the pressure assembly is built up,and the controllable pressure and step response experiments are carried out.Both simulation and experimental results show that the designed slide valve can satisfy the requirements well.The proposed clearance presumption method based on simulation and experimental results is valuable for indirect measurement of processing tolerance.
文摘The title problem is systematically analyzed by the differential quadrature (DQ) method. Estimates of the critical buckling loads are obtained for combinations of various boundary conditions, internal and/or external Pressures, hole sizes,and rigidity ratios. A comparison is made with existing results for certain cases. Numerical investigation has been carried out with regard to the convergence of the solutions. It is found that accurate results are obtained with only nine or eleven grid points.
文摘Background: There is no single noninvasive index that provides a direct measure of LV filling pressure. However, invasive measuring of LV end diastolic pressure (LVEDP) provides reliable assessment of LV diastolic dysfunction, but its invasive nature limits its use in daily practice. Accurate noninvasive assessment of LV diastolic dysfunction is highly desirable, and the relationship between the degree of LVEDP and acceleration of E’ wave obtained by tissue Doppler imaging (TDI) of mitral annulus is not clearly assessed;here in our study we aimed to assess the relation between the degree of LVEDP and the acceleration rate of E’ wave of mitral annular Doppler tissue. Patients and Methods: The study included 60 patients divided equally into 3 groups according to the degree of LVEDP, group I (Normal): ’ ratio and E’ wave acceleration rate. Coronary angiography and left sided heart catheterization and measuring LVEDP were performed for correlating E’ wave acceleration rate with invasively estimated LVEDP.?Results: There was significant progressive decrease in E’ acceleration rate (E’ Acc rate) with progressive increase in LVEDP from I to III (P 0.001), while there was significant progressive increase in E/E’ ratio with progressive increase in LVEDP from I to III (P 0.003). Peak E’ acceleration rate had a significant negative correlation with LVEDP in all three groups, with p value of 0.003, 0.044 and 0.021 respectively in group I, II & III. Regarding E/E’ ratio there was a significant positive correlation in predicting normal and elevated LVEDP with p value (0.001 and 0.006) respectively while there was a non-significant correlation between E/E’ and LVEDP within grey zone group. Conclusion: E’ acceleration rate could be used as a reliable index to assess LVEDP.
文摘Surge pressure caused by pipe moving through the wellbore full of drilling.fluid is the main factor affecting wellbore stability,on which the additional mud density isdesigned.Thus if is desired to predict the surge pressure with high accuracy.While this is closely,related with the selection of mud rheological models.Yield-Pseudoplastic model which has three parameters and is.famous for its higher accuracy has been used to describe the mud rheological properties in recent years.Based on this model the paper presents a new theoretical model for calculating surge pressure caused by mud viscosity during tripping or casing in a concentric annulus of directional wells under steady laminar situation.For convenience,the paper plots the distribution of the coefficients of surge pressure for different conditions.An example is given.These results provide the basis for controlling pressure surges and tripping velocity.
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.
文摘The perturbation method is used to solve the control equations of a three-dimensional annular flow inside a small gap. The nonlinear equations are separated into zeroth-order and first-order perturbation equations. The velocity and pressure distributions are solved successively by different numerical methods with the zeroth-order and first-order equation. Agreement in results is found with the present method and software ANSYS-CFX, which illustrates the applicability of perturbation method in solving complicated flow field inside small gaps.
基金Key projects of technological innovation and application development of Chongqing,China(Grant NO.cstc2018jszx-cyzd0729).
文摘Transient change of the operating parameters has a serious influence on the stability of liquid annular seals.Take the liquid annular seals as a research object,a numerical method based on six-degree-of-freedom(6DOF)to analyze the dynamic response of liquid annular seals under gravity impact load.The variations of the force of liquid seal and pressure as well as the axis trajectory in time history are investigated.The influence of different sealing clearance,different liquid viscosity and different rotor speed is also studied.The results show that the maximum sealing pressure and sealing force of gravity direction will increase greatly in a very short time and then reduce rapidly.When sealing clearance increases,the displacement response amplitudes of axis trajectory,the maximum sealing force of gravity direction and maximum sealing pressure also increase.When liquid viscosity increases,the displacement response amplitudes of axis trajectory,the maximum sealing force of gravity direction and maximum sealing pressure decrease.We also found that different rotor speed has almost no influence on the maximum sealing force of gravity direction and maximum sealing pressure.
