To analyze static pressure between back plate and cylinder in an A186 carding machine,a fluid model is established. The model takes into account static pressure of airflow near back plate with the numerical simulation...To analyze static pressure between back plate and cylinder in an A186 carding machine,a fluid model is established. The model takes into account static pressure of airflow near back plate with the numerical simulation method of Computational Fluid Dynamics (CFD) in FLUENT software. The result of the simulation in the model shows that static pressure in this area quickly increases to its maximum then rapidly decreases to a lower fixed value from inlet to outlet along a zone between back plate and cylinder. Both rotating speeds of the cylinder and the taker-in affect static pressure from the inlet to the outlet,of which the cylinder rotating speed has more influence than that of taker-in. Numerical simulations reveal that static pressure on surface of back plate are in good agreement with the former result of experimental analysis.展开更多
To explore the static pressure dynamic disaster mechanism of coal-and-gas outburst(CGO)fluid,the self-developed multifield coupling large-scale physical simulation test system of coal mine dynamic disaster was used to...To explore the static pressure dynamic disaster mechanism of coal-and-gas outburst(CGO)fluid,the self-developed multifield coupling large-scale physical simulation test system of coal mine dynamic disaster was used to carry out gas outburst and CGO physical simulation tests in straight,L-shaped and T-shaped roadways.The influence of roadway shape on the evolution of static pressure was explored,and the role of pulverized coal in the process of static pressure dynamic disaster was clarified.The results indicated that the static pressure showed a fluctuating downward trend during the outburst process.When gas outburst,the middle and front parts of the roadway in the straight section roadway were the most serious areas of static pressure disasters in the three shapes of roadways.The duration and range of high static pressure disaster in L-shaped roadway were larger than those in T-shaped and straight roadways in turn.When CGO,the most serious area of static pressure disaster in L-shaped and T-shaped roadways moved backward to the middle of the straight section roadway,and there was a rebound phenomenon in the process of static pressure fluctuation decline,which showed the pulse characteristics of CGO.During the outburst,the static pressure dynamic disaster hazard of L-shaped roadway was higher than that of T-shaped roadway,and the static pressure at the bifurcation structure decayed faster than that at the turning structure,which indicated that T-shaped roadway was more conducive to the release of static pressure in roadway,thus reduced the risk of static pressure disaster.When gas outburst,the static pressure attenuation of the fuid in the roadway before and after the turning and bifurcation structure was greater than that of CGO.The peak static pressure and impulse of the fluid during gas outburst were 2 times and 4-5 times that of CGO respectively.The presence of pulverized coal reduced the attenuation of static pressure and the hazard of dynamic disaster,prolonged the release time of energy,and led to the change of the maximum static pressure disaster area.展开更多
Static ice pressure affects safe operation of hydraulic structures. However, current detection methods are hindered by the following limitations： poor real-time performance and errors owing to the partial pressure of...Static ice pressure affects safe operation of hydraulic structures. However, current detection methods are hindered by the following limitations： poor real-time performance and errors owing to the partial pressure of the surrounding wall on traditional electrical resistance strain bellow pressure sensors. We developed a fiber optic sensor with a special pressure bellow to monitor the static ice pressure on hydraulic structures and used the sensor to measure static pressure in laboratory ice growth and melting tests from -30℃ to 5℃. The sensor resolution is 0.02 kPa and its sensitivity is 2.74 × 10-4/kPa. The experiments suggest that the static ice pressure peaks twice during ice growth and melting. The first peak appears when the ice temperature drops to -15℃ owing to the liquid water to solid ice transition. The second peak appears at 0℃ owing to the thermal expansion of the ice during ice melting. The novel fiber optic sensor exhibits stable performance, high resolution, and high sensitivity and it can be used to monitor the static ice pressure during ice growth and melting.展开更多
Non-axisymmetric endwall contouring has been proved to be an effective flow control technique in turbomachinery.Several different flow control mechanisms and qualitative design strategies have been proposed.The endwal...Non-axisymmetric endwall contouring has been proved to be an effective flow control technique in turbomachinery.Several different flow control mechanisms and qualitative design strategies have been proposed.The endwall contouring mechanism based on the flow governing equations is significant for exploring the quantitative design strategies of the nonaxisymmetric endwall contouring.In this paper,the static pressure redistribution mechanism of endwall contouring was explained based on the radial equilibrium equation.A quantified expression of the static pressure redistribution mechanism was proposed.Compressor cascades were simulated using an experimentally validated numerical method to validate the static pressure redistribution mechanism.A geometric parameter named meridional curvature(Cme)is defined to quantify the concave and convex features of the endwall.Results indicate that the contoured endwall changes the streamline curvature,inducing a centrifugal acceleration.Consequently,the radial pressure gradient is reformed to maintain the radial equilibrium.The convex endwall represented by positive Cme increases the radial pressure gradient,decreasing the endwall static pressure,while the concave endwall represented by negative Cme increases the endwall static pressure.The Cme helps to establish the quantified relation between the change in the endwall radial pressure gradient and the endwall geometry.Besides,there is a great correlation between the distributions of the Cme and the change in the endwall static pressure.It can be concluded that the parameter Cme can be considered as a significant parameter to parameterize the endwall surface and to explore the quantitative design strategies of the nonaxisymmetric endwall contouring.展开更多
Exact calculations of the static earth pressure from a thick alluvium require accurate/Co values. These calculations influence the sinking cost and the safety of the freezing method. The static earth pressure coeffici...Exact calculations of the static earth pressure from a thick alluvium require accurate/Co values. These calculations influence the sinking cost and the safety of the freezing method. The static earth pressure coefficient （K0） of thick and deep soil was analyzed using laboratory tests. The results show that the static earth pressure coefficient of thick and deep soils is nonlinear and different from that of superficial soils. The constant of superficial soils is usually invariant and the total stress or incremental stress definitions used in traditional geo-meehanics give the same value. The influence of load increments when calculating for superficial soil is ignored. The difference in values of K0 for thick alluvium defimed by the total stress or the incremental stress methods is over 10%. The effects of the thick alluvium on K0 should be considered during the design of frozen shaft projects. Such things as the frozen shaft thickness and the excavated section height should be chosen to assure the rationality of the design and to avoid potential faults and accidents.展开更多
The static earth pressure coefficient of soils is,approximately,considered to be a constant in the view of clas-sical soil mechanics. This is supported by many research results. The high pressure experimental research...The static earth pressure coefficient of soils is,approximately,considered to be a constant in the view of clas-sical soil mechanics. This is supported by many research results. The high pressure experimental research and analysis of remolding deep soil described herein indicate that the static earth pressure of thick overburden has a notable non lin-ear characteristic. It also appears larger than that of superficial soils. It is necessary for deep coal mine design and con-struction to consider this particularity of soil pressure so as to avoid engineering accidents and heavy loss of life and property.展开更多
This paper aims at analyzing material-induced lateral pressure of RC cylinder silo in both static and dynamic condition using the finite element method( FEM). In the finite element software ABAQUS,concrete material is...This paper aims at analyzing material-induced lateral pressure of RC cylinder silo in both static and dynamic condition using the finite element method( FEM). In the finite element software ABAQUS,concrete material is modeled by concrete damaged plasticity model,and stored materials in silo is modeled by the hypoplastic theory.In terms of numerical model,shell elements( S4R) and solid elements( C3D8) are applied for model silo wall and stored materials respectively. The interaction between silo wall and stored materials is simulated by Coulomb friction model and penalty contact constrain provided by ABAQUS.The numerical results are verified with the existing experimental data that are designed to ensure the validation of such numerical model using FEM and it obtains good agreements between numerical results and experimental data. Then the material parameters are analyzed in both static and dynamic condition.According to the analysis,it is clear that critical friction angle,initial void ratio and minimum void ratio have an obvious effect on static lateral pressure while all the material parameters affect dynamic lateral pressure at different levels. In addition,differences of silo wall between elastic and plastic state are analyzed in dynamic condition. The numerical results show that it contributes to increasing dynamic pressure when silo wall enters into the plastic state. Finally,this paper discusses the time-history lateral pressure at different heights along silo wall,and analytical results indicate that larger acceleration values play main roles in producing the maximum lateral pressure at higher part of the silo wall.展开更多
Based on the needs of society, more and more large bridge construction, to ensure its foundation is stable, safe use, some bridge design units began to consciously in the construction of the bridge static sounding tec...Based on the needs of society, more and more large bridge construction, to ensure its foundation is stable, safe use, some bridge design units began to consciously in the construction of the bridge static sounding technology introduction of pore pressure, it belongs to the soil in situ testing technology, it can synchronize measuring probe in penetration style by pore water, side wall and the cone tip resistance and pressure etc. In addition, the excess pore water pressure dissipation can be measured with high accuracy after penetration stop. Because the excess pore water pressure is a function of drainage, mechanical properties and soil type, this method can be used to further distinguish soil type, accurately divide soil layer, and finally analyze its own physical and mechanical properties. In this paper, a brief introduction of pore pressure static penetration, analysis of geological conditions of a bridge and corresponding test methods, arrangement and analysis of pore pressure static penetration test data and application of pore pressure static penetration results are discussed and analyzed.展开更多
Recently we are witnessing the boom of high-pressure science and technology from a small niche field to becoming a major dimension in physical sciences.One of the most important technological advances is the integrati...Recently we are witnessing the boom of high-pressure science and technology from a small niche field to becoming a major dimension in physical sciences.One of the most important technological advances is the integration of synchrotron nanotechnology with the minute samples at ultrahigh pressures.Applications of high pressure have greatly enhanced our understanding of the electronic,phonon,and doping effects on the newly emerged graphene and related 2D layered materials.High pressure has created exotic stoichiometry even in common Group 17,15,and 14 compounds and drastically altered the basic σ and π bonding of organic compounds.Differential pressure measurements enable us to study the rheology and flow of mantle minerals in solid state,thus quantitatively constraining the geodynamics.They also introduce a new approach to understand defect and plastic deformations of nano particles.These examples open new frontiers of high-pressure research.展开更多
Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length...Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length reduction of a bare S-shaped diffuser to an aggressive S-shaped diffuser would risk flow separation and performance reduction of the diffuser and the air intake of the GT.The objective of this research is to propose and assess fitted energy promoters(EPs)to enhance the S-shaped diffuser performance by controlling and modifying the flow in the high bending zone of the diffuser.After experimental assessment,the work has been extended to cover more cases by numerical investigations on bare,bare aggressive,and aggressive with energy promoters S-shaped diffusers.Three types of EPs,namely co-rotating low-profile,co-rotating streamline sheet,and trapezoidal submerged EPs were tested with various combinations over a range of Reynolds numbers from 40,000 to 75,000.The respective S-shaped diffusers were simulated by computational fluid dynamics(CFD)using ANSYS software adopting a steady,3D,standard k-εturbulence model to acquire the details of the flow structure,which cannot be visualized in the experiment.The diffuser performance has been evaluated by the performance indicators of static pressure recovery coefficient,total pressure loss coefficient,and distortion coefficient(DC(45°)).The enhancements in the static pressure recovery of the S-shaped aggressive diffuser with energy promoters are 19.5%,22.2%,and 24.5%with EPs at planes 3,4 and 5,respectively,compared to the aggressive bare diffuser.In addition,the installation of the EPs resulted in a DC(45°)reduction at the outlet plane of the diffuser of about 43%at Re=40,000.The enhancements in the performance parameters confirm that aggravating the internal flow eliminates the flow separation and enhances the GT intake efficiency.展开更多
This paper simulates the combustion system of a regular tankless gas water heater under different static pressure conditions.The simulation results are in accordance with the test results.It proves that the used physi...This paper simulates the combustion system of a regular tankless gas water heater under different static pressure conditions.The simulation results are in accordance with the test results.It proves that the used physical and mathematical models are reasonable.The results show that the flame height and the excess air ratios depend on the system pressure drop but not on the absolute pressure at the combustion chamber.The pressure drop and the amount of combustion air have an inverse relationship with CO generation,and they also impact on the temperature and velocity fields.To reduce CO emission,a stronger fan is needed to provide extra pressure head to ensure that enough combustion air is introduced into the system.This study provides a useful research tool to develop products through computational fluid dynamic analysis and laboratory testing.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
In application,lithium-ion cells undergo expansion during cycling.The mechanical behavior and the impact of external stress on lithium-ion battery are important in vehicle application.In this work,18 Ah high power com...In application,lithium-ion cells undergo expansion during cycling.The mechanical behavior and the impact of external stress on lithium-ion battery are important in vehicle application.In this work,18 Ah high power commercial cell with Li Ni_(0.5)Co_(0.2)Mn_(0.3)O_(2)/graphite electrode were adopted.A commercial compress machine was applied to monitor the mechanical characteristics under different stage of charge(SOC),lifetime and initial external force.The dynamic and steady force was obtained and the results show that the dynamic force increases as the SOC increasing,obviously.During the lifetime with high power driving mode,different external force is shown to have a great impact on the long-term cell performance,with higher stresses result in higher capacity decay rates and faster impedance increases.A proper initial external force(900 N)provides lower impedance increasing.Postmortem analysis of the cells with2000 N initial force suggests a close correlation between electrochemistry and mechanics in which higher initial force leads to higher direct current internal resistance(DCIR)increase rate.In addition,for the cell with higher external force,deformation of the cathode and thicker solid electrolyte interface(SEI)film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.In addition,for the cell with higher external force,deformation of the cathode and thicker SEI film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.展开更多
The 2-meter High-speed Free-jet Wind Tunnel(2 m HFWT)is China’s first large-scale open-jet trisonic wind tunnel.Compared to traditional closed high-speed wind tunnels,this wind tunnel is endowed with remarkable advan...The 2-meter High-speed Free-jet Wind Tunnel(2 m HFWT)is China’s first large-scale open-jet trisonic wind tunnel.Compared to traditional closed high-speed wind tunnels,this wind tunnel is endowed with remarkable advantages of ample test chamber space,less interference from the tunnel wall,flexible model support mode,and adjustable continuous variation of the Mach number.Nevertheless,its unique structure makes traditional wind tunnel control methods difficult to apply and brings significant challenges to wind tunnel flow field control.In this paper,a flow field control system is designed for the 2 m HFWT by comprehensively using advanced control technologies such as neural network,gain scheduling,feedforward control,and adaptive control.Through practical application tests,it is proved that the proposed control system successfully solves the problem of high-precision flow field control under continual depletion of storage tank pressure,and realizes distinctive functions of adaptive static pressure matching and continuously varying Mach number at supersonic speed.In addition,due to the application of workflow technology,the flow field control system can flexibly adapt to the implementation of tests of different types and operation conditions,thus fully satisfying the needs of conducting various conventional and special tests in the 2 m HFWT.展开更多
Numerical simulation are conducted to explore the characteristics of the axial inflow and related aerodynamic noise for a large-scale adjustable fan with the installation angle changing from−12°to 12°.In suc...Numerical simulation are conducted to explore the characteristics of the axial inflow and related aerodynamic noise for a large-scale adjustable fan with the installation angle changing from−12°to 12°.In such a range the maximum static(gauge)pressure at the inlet changes from−2280 Pa to 382 Pa,and the minimum static pressure decreases from−3389 Pa to−8000 Pa.As for the axial intermediate flow surface,one low pressure zone is located at the junction of the suction surface and the hub,another is located at the suction surface close to the casing position.At the outlet boundary,the low pressure is negative and decreases from−1716 Pa to−4589 Pa.The sound pressure level of the inlet and outlet noise tends to increase monotonously by 11.6 dB and 7.3 dB,respectively.The acoustic energy of discrete noise is always higher than that of broadband noise regardless of whether the inlet or outlet flow surfaces are considered.The acoustic energy ratio of discrete noise at the inlet tends to increase from 0.78 to 0.93,while at the outlet it first decreases from 0.79 to 0.73 and then increases to 0.84.展开更多
The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was u...The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.展开更多
The internal energy change of ideal gas does not depend on the volume and pressure. The internal energy change of real gas has not any relation with the volume and pressure, which had been proved. If the internal ener...The internal energy change of ideal gas does not depend on the volume and pressure. The internal energy change of real gas has not any relation with the volume and pressure, which had been proved. If the internal energy change had not any relation with the volume and pressure, we could confirm the first law of thermodynamics in theory. Simultaneously, the internal energy change is the state function that shall be able to be proved in theory. If the internal energy change depended on the volume and pressure, we could not prove that the internal energy change is the state function and the chemical thermodynamics theory is right. The extended or modified Bernoulli equation can be derived from the energy conservation law, and the internal energy change, heat, and friction are all considered in the derivation procedure. The extended Bernoulli equation could be applied to the flying aircraft and mechanical motion on the gravitational field, for instance, the rocket and airplane and so on. This paper also revises some wrong ideas, viewpoints, or concepts about the thermodynamics theory and Bernoulli equation.展开更多
The static pressure recovery of low-pressure exhaust hood is important for the overall effectiveness of steam turbines.The tubular and plate stiffeners inside the exhaust contribute to the structural safety of exhaust...The static pressure recovery of low-pressure exhaust hood is important for the overall effectiveness of steam turbines.The tubular and plate stiffeners inside the exhaust contribute to the structural safety of exhaust,which affect the aerodynamic performance.Given the complicated exhaust model coupled with the last stage of turbine,this paper intends to investigate the aerodynamic performance of exhaust hood with individual stiffeners using highfidelity numerical simulations in order to figure out the corresponding effects.The results show that(1)the types of stiffeners have different effects on the aerodynamic performance;and(2)different installation positions and types of plate stiffeners have different effects on aerodynamic performance.The above investigations highlight the future demand regarding reasonable layout and quantity of stiffeners to improve the aerodynamic performance of exhaust as well as maintaining the structural safety.展开更多
An abnormality tends to occur in the productivity indicative curves in the process of productivity test interpretation of multi-layer gas wells,resulting in the failure of solutions to their productivity equations and...An abnormality tends to occur in the productivity indicative curves in the process of productivity test interpretation of multi-layer gas wells,resulting in the failure of solutions to their productivity equations and absolute open flow rates.To figure out the reasons for such an abnormality,we established a full-hole calculation model considering the coupling of wellbore variable mass flows and reservoir seepages to calculate a gas production profile and wellbore pressure distribution of a multi-layer productive gas reservoir.Then,based on the analysis of the gas production profile and wellbore pressure distribution characteristics of gas wells at different gas production rates,the root cause for the abnormality in the productivity indicative curves of multi-layer gas wells was analyzed,and a corresponding correction method was proposed and validated based on some examples.And the following research results were obtained.First,there are two reasons for the abnormal productivity indicative curves of multi-layer gas wells.On the one hand,there is a variable mass pipe flow in the wellbore of multi-layer sections and a flowing pressure gradient decreases with the increase of well depth.And the flowing pressure in the middle of the reservoir which is converted based on the flowing pressure gradient above the pressure gauge is higher than the real value.On the other hand,the pressure in the multi-layer producing sections doesn't realize a balance after well shutdown for a short time,so the measured static pressure is greater than the one measured when the pressure of each layer gets balanced after well shutdown for a long time.Second,the flowing pressure obtained from the productivity test interpretation of multi-layer gas producer shall be converted based on the pressure measured by the pressure gauge within 200 m above the reservoir top and it is necessary to adopt the static pressure measured after the balance of wellbore pressure.Third,the reliability of the model,the rationality of the abnormality reason analysis and the validity of the correction method are verified based on calculation examples and cases.It is concluded that the research results provide a technical support for the productivity evaluation of multi-layer gas wells.展开更多
Aiming at the influence of blade pitch Angle on aerodynamic noise of wind turbines, the sound field and flow field distribution at 0˚, 5˚, 10˚ and 15˚ are calculated by numerical simulation. Then, through the distribu...Aiming at the influence of blade pitch Angle on aerodynamic noise of wind turbines, the sound field and flow field distribution at 0˚, 5˚, 10˚ and 15˚ are calculated by numerical simulation. Then, through the distribution of pressure field and velocity field calculated by flow field, the influence of different pitch angles on wind turbine blade aerodynamic noise and the reasons for its influence are analyzed. The results show that when the pitch Angle increases within 0˚ - 10˚, the aerodynamic noise pressure level of the blade decreases. However, the sound pressure level of aerodynamic noise increases in the range of 10˚ - 15˚. The changes of static pressure gradient and pressure pulsation on the blade surface make the aerodynamic noise change, and the changes of the two are positively correlated. At the same time, the fluid velocity and fluid motion state on the blade surface are closely related to the aerodynamic noise of the blade. The greater the fluid velocity, the more complex the fluid motion state and the greater the turbulent kinetic energy of the wind turbine blade, and the aerodynamic noise of the wind turbine blade will also increase.展开更多
基金Project of Liaoning Provincial Science and Technology Department, China(No.200322026)
文摘To analyze static pressure between back plate and cylinder in an A186 carding machine,a fluid model is established. The model takes into account static pressure of airflow near back plate with the numerical simulation method of Computational Fluid Dynamics (CFD) in FLUENT software. The result of the simulation in the model shows that static pressure in this area quickly increases to its maximum then rapidly decreases to a lower fixed value from inlet to outlet along a zone between back plate and cylinder. Both rotating speeds of the cylinder and the taker-in affect static pressure from the inlet to the outlet,of which the cylinder rotating speed has more influence than that of taker-in. Numerical simulations reveal that static pressure on surface of back plate are in good agreement with the former result of experimental analysis.
基金supported by the National Natural Science Foundation of China(51874055,52074047).
文摘To explore the static pressure dynamic disaster mechanism of coal-and-gas outburst(CGO)fluid,the self-developed multifield coupling large-scale physical simulation test system of coal mine dynamic disaster was used to carry out gas outburst and CGO physical simulation tests in straight,L-shaped and T-shaped roadways.The influence of roadway shape on the evolution of static pressure was explored,and the role of pulverized coal in the process of static pressure dynamic disaster was clarified.The results indicated that the static pressure showed a fluctuating downward trend during the outburst process.When gas outburst,the middle and front parts of the roadway in the straight section roadway were the most serious areas of static pressure disasters in the three shapes of roadways.The duration and range of high static pressure disaster in L-shaped roadway were larger than those in T-shaped and straight roadways in turn.When CGO,the most serious area of static pressure disaster in L-shaped and T-shaped roadways moved backward to the middle of the straight section roadway,and there was a rebound phenomenon in the process of static pressure fluctuation decline,which showed the pulse characteristics of CGO.During the outburst,the static pressure dynamic disaster hazard of L-shaped roadway was higher than that of T-shaped roadway,and the static pressure at the bifurcation structure decayed faster than that at the turning structure,which indicated that T-shaped roadway was more conducive to the release of static pressure in roadway,thus reduced the risk of static pressure disaster.When gas outburst,the static pressure attenuation of the fuid in the roadway before and after the turning and bifurcation structure was greater than that of CGO.The peak static pressure and impulse of the fluid during gas outburst were 2 times and 4-5 times that of CGO respectively.The presence of pulverized coal reduced the attenuation of static pressure and the hazard of dynamic disaster,prolonged the release time of energy,and led to the change of the maximum static pressure disaster area.
基金supported by the National Natural Science Foundation of China(No.51279122)the Graduate Innovation Foundation of Taiyuan University of Technology(No.2013A019)
文摘Static ice pressure affects safe operation of hydraulic structures. However, current detection methods are hindered by the following limitations： poor real-time performance and errors owing to the partial pressure of the surrounding wall on traditional electrical resistance strain bellow pressure sensors. We developed a fiber optic sensor with a special pressure bellow to monitor the static ice pressure on hydraulic structures and used the sensor to measure static pressure in laboratory ice growth and melting tests from -30℃ to 5℃. The sensor resolution is 0.02 kPa and its sensitivity is 2.74 × 10-4/kPa. The experiments suggest that the static ice pressure peaks twice during ice growth and melting. The first peak appears when the ice temperature drops to -15℃ owing to the liquid water to solid ice transition. The second peak appears at 0℃ owing to the thermal expansion of the ice during ice melting. The novel fiber optic sensor exhibits stable performance, high resolution, and high sensitivity and it can be used to monitor the static ice pressure during ice growth and melting.
基金This study was supported by the National Natural Science Foundation Project(52376021).
文摘Non-axisymmetric endwall contouring has been proved to be an effective flow control technique in turbomachinery.Several different flow control mechanisms and qualitative design strategies have been proposed.The endwall contouring mechanism based on the flow governing equations is significant for exploring the quantitative design strategies of the nonaxisymmetric endwall contouring.In this paper,the static pressure redistribution mechanism of endwall contouring was explained based on the radial equilibrium equation.A quantified expression of the static pressure redistribution mechanism was proposed.Compressor cascades were simulated using an experimentally validated numerical method to validate the static pressure redistribution mechanism.A geometric parameter named meridional curvature(Cme)is defined to quantify the concave and convex features of the endwall.Results indicate that the contoured endwall changes the streamline curvature,inducing a centrifugal acceleration.Consequently,the radial pressure gradient is reformed to maintain the radial equilibrium.The convex endwall represented by positive Cme increases the radial pressure gradient,decreasing the endwall static pressure,while the concave endwall represented by negative Cme increases the endwall static pressure.The Cme helps to establish the quantified relation between the change in the endwall radial pressure gradient and the endwall geometry.Besides,there is a great correlation between the distributions of the Cme and the change in the endwall static pressure.It can be concluded that the parameter Cme can be considered as a significant parameter to parameterize the endwall surface and to explore the quantitative design strategies of the nonaxisymmetric endwall contouring.
基金Project BK2007040 supported by the Provincial Natural Science Foundation of Jiangsu, China
文摘Exact calculations of the static earth pressure from a thick alluvium require accurate/Co values. These calculations influence the sinking cost and the safety of the freezing method. The static earth pressure coefficient （K0） of thick and deep soil was analyzed using laboratory tests. The results show that the static earth pressure coefficient of thick and deep soils is nonlinear and different from that of superficial soils. The constant of superficial soils is usually invariant and the total stress or incremental stress definitions used in traditional geo-meehanics give the same value. The influence of load increments when calculating for superficial soil is ignored. The difference in values of K0 for thick alluvium defimed by the total stress or the incremental stress methods is over 10%. The effects of the thick alluvium on K0 should be considered during the design of frozen shaft projects. Such things as the frozen shaft thickness and the excavated section height should be chosen to assure the rationality of the design and to avoid potential faults and accidents.
基金Project 50534040 supported by the National Natrual Science Foundation of China
文摘The static earth pressure coefficient of soils is,approximately,considered to be a constant in the view of clas-sical soil mechanics. This is supported by many research results. The high pressure experimental research and analysis of remolding deep soil described herein indicate that the static earth pressure of thick overburden has a notable non lin-ear characteristic. It also appears larger than that of superficial soils. It is necessary for deep coal mine design and con-struction to consider this particularity of soil pressure so as to avoid engineering accidents and heavy loss of life and property.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51478033,51179029)
文摘This paper aims at analyzing material-induced lateral pressure of RC cylinder silo in both static and dynamic condition using the finite element method( FEM). In the finite element software ABAQUS,concrete material is modeled by concrete damaged plasticity model,and stored materials in silo is modeled by the hypoplastic theory.In terms of numerical model,shell elements( S4R) and solid elements( C3D8) are applied for model silo wall and stored materials respectively. The interaction between silo wall and stored materials is simulated by Coulomb friction model and penalty contact constrain provided by ABAQUS.The numerical results are verified with the existing experimental data that are designed to ensure the validation of such numerical model using FEM and it obtains good agreements between numerical results and experimental data. Then the material parameters are analyzed in both static and dynamic condition.According to the analysis,it is clear that critical friction angle,initial void ratio and minimum void ratio have an obvious effect on static lateral pressure while all the material parameters affect dynamic lateral pressure at different levels. In addition,differences of silo wall between elastic and plastic state are analyzed in dynamic condition. The numerical results show that it contributes to increasing dynamic pressure when silo wall enters into the plastic state. Finally,this paper discusses the time-history lateral pressure at different heights along silo wall,and analytical results indicate that larger acceleration values play main roles in producing the maximum lateral pressure at higher part of the silo wall.
文摘Based on the needs of society, more and more large bridge construction, to ensure its foundation is stable, safe use, some bridge design units began to consciously in the construction of the bridge static sounding technology introduction of pore pressure, it belongs to the soil in situ testing technology, it can synchronize measuring probe in penetration style by pore water, side wall and the cone tip resistance and pressure etc. In addition, the excess pore water pressure dissipation can be measured with high accuracy after penetration stop. Because the excess pore water pressure is a function of drainage, mechanical properties and soil type, this method can be used to further distinguish soil type, accurately divide soil layer, and finally analyze its own physical and mechanical properties. In this paper, a brief introduction of pore pressure static penetration, analysis of geological conditions of a bridge and corresponding test methods, arrangement and analysis of pore pressure static penetration test data and application of pore pressure static penetration results are discussed and analyzed.
文摘Recently we are witnessing the boom of high-pressure science and technology from a small niche field to becoming a major dimension in physical sciences.One of the most important technological advances is the integration of synchrotron nanotechnology with the minute samples at ultrahigh pressures.Applications of high pressure have greatly enhanced our understanding of the electronic,phonon,and doping effects on the newly emerged graphene and related 2D layered materials.High pressure has created exotic stoichiometry even in common Group 17,15,and 14 compounds and drastically altered the basic σ and π bonding of organic compounds.Differential pressure measurements enable us to study the rheology and flow of mantle minerals in solid state,thus quantitatively constraining the geodynamics.They also introduce a new approach to understand defect and plastic deformations of nano particles.These examples open new frontiers of high-pressure research.
文摘Size reduction of the gas turbines(GT)by reducing the inlet S-shaped diffuser length increases the powerto-weight ratio.It improves the techno-economic features of the GT by lesser fuel consumption.However,this Length reduction of a bare S-shaped diffuser to an aggressive S-shaped diffuser would risk flow separation and performance reduction of the diffuser and the air intake of the GT.The objective of this research is to propose and assess fitted energy promoters(EPs)to enhance the S-shaped diffuser performance by controlling and modifying the flow in the high bending zone of the diffuser.After experimental assessment,the work has been extended to cover more cases by numerical investigations on bare,bare aggressive,and aggressive with energy promoters S-shaped diffusers.Three types of EPs,namely co-rotating low-profile,co-rotating streamline sheet,and trapezoidal submerged EPs were tested with various combinations over a range of Reynolds numbers from 40,000 to 75,000.The respective S-shaped diffusers were simulated by computational fluid dynamics(CFD)using ANSYS software adopting a steady,3D,standard k-εturbulence model to acquire the details of the flow structure,which cannot be visualized in the experiment.The diffuser performance has been evaluated by the performance indicators of static pressure recovery coefficient,total pressure loss coefficient,and distortion coefficient(DC(45°)).The enhancements in the static pressure recovery of the S-shaped aggressive diffuser with energy promoters are 19.5%,22.2%,and 24.5%with EPs at planes 3,4 and 5,respectively,compared to the aggressive bare diffuser.In addition,the installation of the EPs resulted in a DC(45°)reduction at the outlet plane of the diffuser of about 43%at Re=40,000.The enhancements in the performance parameters confirm that aggravating the internal flow eliminates the flow separation and enhances the GT intake efficiency.
文摘This paper simulates the combustion system of a regular tankless gas water heater under different static pressure conditions.The simulation results are in accordance with the test results.It proves that the used physical and mathematical models are reasonable.The results show that the flame height and the excess air ratios depend on the system pressure drop but not on the absolute pressure at the combustion chamber.The pressure drop and the amount of combustion air have an inverse relationship with CO generation,and they also impact on the temperature and velocity fields.To reduce CO emission,a stronger fan is needed to provide extra pressure head to ensure that enough combustion air is introduced into the system.This study provides a useful research tool to develop products through computational fluid dynamic analysis and laboratory testing.
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financially supported by the National Key Research&Development Program of China(2016YFB0100400)the National Natural Science Foundation of China(21875154 and 22179090)。
文摘In application,lithium-ion cells undergo expansion during cycling.The mechanical behavior and the impact of external stress on lithium-ion battery are important in vehicle application.In this work,18 Ah high power commercial cell with Li Ni_(0.5)Co_(0.2)Mn_(0.3)O_(2)/graphite electrode were adopted.A commercial compress machine was applied to monitor the mechanical characteristics under different stage of charge(SOC),lifetime and initial external force.The dynamic and steady force was obtained and the results show that the dynamic force increases as the SOC increasing,obviously.During the lifetime with high power driving mode,different external force is shown to have a great impact on the long-term cell performance,with higher stresses result in higher capacity decay rates and faster impedance increases.A proper initial external force(900 N)provides lower impedance increasing.Postmortem analysis of the cells with2000 N initial force suggests a close correlation between electrochemistry and mechanics in which higher initial force leads to higher direct current internal resistance(DCIR)increase rate.In addition,for the cell with higher external force,deformation of the cathode and thicker solid electrolyte interface(SEI)film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.In addition,for the cell with higher external force,deformation of the cathode and thicker SEI film on the surface of anode and separator are observed.Porosity reduction and closure was also verified after cycles which is an obstacle to the lithium ion transferring.The largest cause of the observed capacity decline was the loss of active lithium through autopsy analysis.
文摘The 2-meter High-speed Free-jet Wind Tunnel(2 m HFWT)is China’s first large-scale open-jet trisonic wind tunnel.Compared to traditional closed high-speed wind tunnels,this wind tunnel is endowed with remarkable advantages of ample test chamber space,less interference from the tunnel wall,flexible model support mode,and adjustable continuous variation of the Mach number.Nevertheless,its unique structure makes traditional wind tunnel control methods difficult to apply and brings significant challenges to wind tunnel flow field control.In this paper,a flow field control system is designed for the 2 m HFWT by comprehensively using advanced control technologies such as neural network,gain scheduling,feedforward control,and adaptive control.Through practical application tests,it is proved that the proposed control system successfully solves the problem of high-precision flow field control under continual depletion of storage tank pressure,and realizes distinctive functions of adaptive static pressure matching and continuously varying Mach number at supersonic speed.In addition,due to the application of workflow technology,the flow field control system can flexibly adapt to the implementation of tests of different types and operation conditions,thus fully satisfying the needs of conducting various conventional and special tests in the 2 m HFWT.
基金supported by Key Research and Development Project of Shandong Province[2019GSF109084]Young Scholars Program of Shandong University[2018WLJH73].
文摘Numerical simulation are conducted to explore the characteristics of the axial inflow and related aerodynamic noise for a large-scale adjustable fan with the installation angle changing from−12°to 12°.In such a range the maximum static(gauge)pressure at the inlet changes from−2280 Pa to 382 Pa,and the minimum static pressure decreases from−3389 Pa to−8000 Pa.As for the axial intermediate flow surface,one low pressure zone is located at the junction of the suction surface and the hub,another is located at the suction surface close to the casing position.At the outlet boundary,the low pressure is negative and decreases from−1716 Pa to−4589 Pa.The sound pressure level of the inlet and outlet noise tends to increase monotonously by 11.6 dB and 7.3 dB,respectively.The acoustic energy of discrete noise is always higher than that of broadband noise regardless of whether the inlet or outlet flow surfaces are considered.The acoustic energy ratio of discrete noise at the inlet tends to increase from 0.78 to 0.93,while at the outlet it first decreases from 0.79 to 0.73 and then increases to 0.84.
文摘The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.
文摘The internal energy change of ideal gas does not depend on the volume and pressure. The internal energy change of real gas has not any relation with the volume and pressure, which had been proved. If the internal energy change had not any relation with the volume and pressure, we could confirm the first law of thermodynamics in theory. Simultaneously, the internal energy change is the state function that shall be able to be proved in theory. If the internal energy change depended on the volume and pressure, we could not prove that the internal energy change is the state function and the chemical thermodynamics theory is right. The extended or modified Bernoulli equation can be derived from the energy conservation law, and the internal energy change, heat, and friction are all considered in the derivation procedure. The extended Bernoulli equation could be applied to the flying aircraft and mechanical motion on the gravitational field, for instance, the rocket and airplane and so on. This paper also revises some wrong ideas, viewpoints, or concepts about the thermodynamics theory and Bernoulli equation.
基金National Natural Science Foundation of China(52005074)Natural Science Foundation of Liaoning Province(2022-MS-135)。
文摘The static pressure recovery of low-pressure exhaust hood is important for the overall effectiveness of steam turbines.The tubular and plate stiffeners inside the exhaust contribute to the structural safety of exhaust,which affect the aerodynamic performance.Given the complicated exhaust model coupled with the last stage of turbine,this paper intends to investigate the aerodynamic performance of exhaust hood with individual stiffeners using highfidelity numerical simulations in order to figure out the corresponding effects.The results show that(1)the types of stiffeners have different effects on the aerodynamic performance;and(2)different installation positions and types of plate stiffeners have different effects on aerodynamic performance.The above investigations highlight the future demand regarding reasonable layout and quantity of stiffeners to improve the aerodynamic performance of exhaust as well as maintaining the structural safety.
文摘An abnormality tends to occur in the productivity indicative curves in the process of productivity test interpretation of multi-layer gas wells,resulting in the failure of solutions to their productivity equations and absolute open flow rates.To figure out the reasons for such an abnormality,we established a full-hole calculation model considering the coupling of wellbore variable mass flows and reservoir seepages to calculate a gas production profile and wellbore pressure distribution of a multi-layer productive gas reservoir.Then,based on the analysis of the gas production profile and wellbore pressure distribution characteristics of gas wells at different gas production rates,the root cause for the abnormality in the productivity indicative curves of multi-layer gas wells was analyzed,and a corresponding correction method was proposed and validated based on some examples.And the following research results were obtained.First,there are two reasons for the abnormal productivity indicative curves of multi-layer gas wells.On the one hand,there is a variable mass pipe flow in the wellbore of multi-layer sections and a flowing pressure gradient decreases with the increase of well depth.And the flowing pressure in the middle of the reservoir which is converted based on the flowing pressure gradient above the pressure gauge is higher than the real value.On the other hand,the pressure in the multi-layer producing sections doesn't realize a balance after well shutdown for a short time,so the measured static pressure is greater than the one measured when the pressure of each layer gets balanced after well shutdown for a long time.Second,the flowing pressure obtained from the productivity test interpretation of multi-layer gas producer shall be converted based on the pressure measured by the pressure gauge within 200 m above the reservoir top and it is necessary to adopt the static pressure measured after the balance of wellbore pressure.Third,the reliability of the model,the rationality of the abnormality reason analysis and the validity of the correction method are verified based on calculation examples and cases.It is concluded that the research results provide a technical support for the productivity evaluation of multi-layer gas wells.
文摘Aiming at the influence of blade pitch Angle on aerodynamic noise of wind turbines, the sound field and flow field distribution at 0˚, 5˚, 10˚ and 15˚ are calculated by numerical simulation. Then, through the distribution of pressure field and velocity field calculated by flow field, the influence of different pitch angles on wind turbine blade aerodynamic noise and the reasons for its influence are analyzed. The results show that when the pitch Angle increases within 0˚ - 10˚, the aerodynamic noise pressure level of the blade decreases. However, the sound pressure level of aerodynamic noise increases in the range of 10˚ - 15˚. The changes of static pressure gradient and pressure pulsation on the blade surface make the aerodynamic noise change, and the changes of the two are positively correlated. At the same time, the fluid velocity and fluid motion state on the blade surface are closely related to the aerodynamic noise of the blade. The greater the fluid velocity, the more complex the fluid motion state and the greater the turbulent kinetic energy of the wind turbine blade, and the aerodynamic noise of the wind turbine blade will also increase.
