采用重整化群(renormalization group,RNG)理论k-ε湍流模型以及流体体积(volume of fluid,VOF)函数气液两相流模型对有压管道局部高点滞留气团的排出进行数值模拟,计算出气泡开始出现破碎的临界流速v1、气泡开始有效破碎且小气泡被带...采用重整化群(renormalization group,RNG)理论k-ε湍流模型以及流体体积(volume of fluid,VOF)函数气液两相流模型对有压管道局部高点滞留气团的排出进行数值模拟,计算出气泡开始出现破碎的临界流速v1、气泡开始有效破碎且小气泡被带走的临界流速v2以及气泡被一次性带走的临界流速v3。此外,通过粒子图像测速(particle image velocimetry,PIV)系统测试了3种临界速度下的流场结构。研究表明:有压管道下降角度增大,3种临界流速均增大;随着滞留气团的体积变大,临界流速v1减小,而临界流速v2和v3均增大;在管道直径、下降角、气量均不变的情况下,临界流速v3比v2大2%~10%,但临界流速v1远小于v2。展开更多
The optimal operation of water distribution networks under local pipe failures, such as water main breaks, was proposed. Based on a hydraulic analysis and a simulation of water distribution networks, a macroscopic mod...The optimal operation of water distribution networks under local pipe failures, such as water main breaks, was proposed. Based on a hydraulic analysis and a simulation of water distribution networks, a macroscopic model for a network under a local pipe failure was established by the statistical regression. After the operation objectives under a local pipe failure were determined, the optimal operation model was developed and solved by the genetic algorithm. The program was developed and examined by a city distribution network. The optimal operation alternative shows that the electricity cost is saved approximately 11%, the income of the water corporation is increased approximately 5%, and the pressure in the water distribution network is distributed evenly to ensure the network safe operation. Therefore, the proposed method for optimal operation under local pipe failure is feasible and cost-effective.展开更多
Pencil hardness testing,electrochemical impedance spectroscopy,scanning electron microscopy,and scanning Kelvin probe microscopy were used to study the local corrosion characteristics of a graphene-oxide-modified inne...Pencil hardness testing,electrochemical impedance spectroscopy,scanning electron microscopy,and scanning Kelvin probe microscopy were used to study the local corrosion characteristics of a graphene-oxide-modified inner coating.The effect of chloride concentration on the corrosion of the damaged inner coating was studied.The effects of chloride ions on damaged internal coatings and graphene-oxide-modified internal coatings were investigated.It was proposed to add graphene oxide into the epoxy coating to effectively inhibit the metal corrosion at the breakage.Because of the existence of graphene oxide(GO),the modified coating had a better physical property and had the effective infiltration of H2O and Cl^- into the coating.The results showed that graphene oxide coatings can give X80 steel better corrosion resistance in sodium chloride solution.展开更多
In the design of Hydraulic Manifold Blocks (HMB), dynamic performance of inner pipeline networks usually should be evaluated. To meet the design requirements, dynamic characteristic simulation is often needed. Based o...In the design of Hydraulic Manifold Blocks (HMB), dynamic performance of inner pipeline networks usually should be evaluated. To meet the design requirements, dynamic characteristic simulation is often needed. Based on comprehensive study on the existing simulation methods, a new method combined of Power Bond Graph(PBG) and Computational Fluid Dynamic (CFD) is proposed. In this method, flow field of typical channels inside HMB is analyzed with CFD to obtain the local resistance coefficients. Then, with these coefficients, a new sectional lumped-parameter model including kinetic friction factor is developed using PBG. A typical HMB design example is given and the comparison between the simulation and the experimental results demonstrates the feasibility and effectiveness of the proposed method.展开更多
基金Project(50278062) supported by the National Natural Science Foundation of ChinaProject(003611611)supported by the Natural Science Foundation of Tianjin, China
文摘The optimal operation of water distribution networks under local pipe failures, such as water main breaks, was proposed. Based on a hydraulic analysis and a simulation of water distribution networks, a macroscopic model for a network under a local pipe failure was established by the statistical regression. After the operation objectives under a local pipe failure were determined, the optimal operation model was developed and solved by the genetic algorithm. The program was developed and examined by a city distribution network. The optimal operation alternative shows that the electricity cost is saved approximately 11%, the income of the water corporation is increased approximately 5%, and the pressure in the water distribution network is distributed evenly to ensure the network safe operation. Therefore, the proposed method for optimal operation under local pipe failure is feasible and cost-effective.
基金Project(51674212)supported by the National Natural Science Foundation of China。
文摘Pencil hardness testing,electrochemical impedance spectroscopy,scanning electron microscopy,and scanning Kelvin probe microscopy were used to study the local corrosion characteristics of a graphene-oxide-modified inner coating.The effect of chloride concentration on the corrosion of the damaged inner coating was studied.The effects of chloride ions on damaged internal coatings and graphene-oxide-modified internal coatings were investigated.It was proposed to add graphene oxide into the epoxy coating to effectively inhibit the metal corrosion at the breakage.Because of the existence of graphene oxide(GO),the modified coating had a better physical property and had the effective infiltration of H2O and Cl^- into the coating.The results showed that graphene oxide coatings can give X80 steel better corrosion resistance in sodium chloride solution.
基金National Natural Science Foundation of China (No.50375023)
文摘In the design of Hydraulic Manifold Blocks (HMB), dynamic performance of inner pipeline networks usually should be evaluated. To meet the design requirements, dynamic characteristic simulation is often needed. Based on comprehensive study on the existing simulation methods, a new method combined of Power Bond Graph(PBG) and Computational Fluid Dynamic (CFD) is proposed. In this method, flow field of typical channels inside HMB is analyzed with CFD to obtain the local resistance coefficients. Then, with these coefficients, a new sectional lumped-parameter model including kinetic friction factor is developed using PBG. A typical HMB design example is given and the comparison between the simulation and the experimental results demonstrates the feasibility and effectiveness of the proposed method.
