Discusses the significance of induction motor constant resistance (IM R) load on the lower part of the PV curve of a power system and determines the conditions for stable operation of IM R load using fuzzy techniques ...Discusses the significance of induction motor constant resistance (IM R) load on the lower part of the PV curve of a power system and determines the conditions for stable operation of IM R load using fuzzy techniques and load flow.展开更多
When the ship is sailing at sea,wave added resistance has great influence on the rapidity and economy of the ship.With the increasing pressure of energy and environmental protection,IMO has proposed the EEDI formula o...When the ship is sailing at sea,wave added resistance has great influence on the rapidity and economy of the ship.With the increasing pressure of energy and environmental protection,IMO has proposed the EEDI formula of the newly built ships,which restricts the energy consumption standard of civil ships more strictly.Therefore,a panel method based on three dimensional potential flow theory is proposed to study the problem of wave added resistance in this paper.Firstly,the method solves the motion responses of the ship in the time domain,and then calculates the wave added resistance of the ship by near-field pressure integration method.The wave added resistance of S175 container ship in head and oblique waves are calculated and compared with the experimental data,and the accuracy of the proposed method are verified.At last,the influence of Froude number and wave direction angle on wave added resistance is studied.The proposed method provides an approach of satisfactory accuracy and efficiency for the development of high-performance new ship forms,optimization of ship hull lines,comprehensive performance evaluation of ships and practical navigation guidance.展开更多
On the basis of a macro flow resistance method and the Darcy Theory,a mathematical model is elaborated to characterize the flow resistance of a bag filter serving a coal-fired power plant.The development of the theore...On the basis of a macro flow resistance method and the Darcy Theory,a mathematical model is elaborated to characterize the flow resistance of a bag filter serving a coal-fired power plant.The development of the theoretical model is supported through acquisition of relevant data obtained by scanning the micro structure of the bag filter by means of an electron microscope.The influence of the running time and boiler load on the flow resistance and the impact of the flow resistance on the efficiency of the induced draft fan are analyzed by comparing the results of on-site operation tests.We show that the initial operation time and the table operation time are linearly related to the flow resistance of the bag filter;with the increase of boiler load,the flow resistance of the bag filter rises approximately as a quadratic function;with the rise of resistance,the power consumption of the induced draft fan increases while the efficiency of the induced draft fan decreases.展开更多
The construction of an integrated numerical model is presented in this paper to deal with the interactions between vegetated surface and saturated subsurface flows. A numerical model is built by integrating the previo...The construction of an integrated numerical model is presented in this paper to deal with the interactions between vegetated surface and saturated subsurface flows. A numerical model is built by integrating the previously developed quasi-three-dimensional （Q3D） vegetated surface flow model with a two-dimensional （2D） saturated groundwater flow model. The vegetated surface flow model is constructed by coupling the explicit finite volume solution of 2D shallow water equations （SWEs） with the implicit finite difference solution of Navier-Stokes equations （NSEs） for vertical velocity distribution. The subsurface model is based on the explicit finite volume solution of 2D saturated groundwater flow equations （SGFEs）. The ground and vegetated surface water interaction is achieved by introducing source-sink terms into the continuity equations. Two solutions are tightly coupled in a single code. The integrated model is applied to four test cases, and the results are satisfactory.展开更多
Calculating the resistance of ventilation air-conditioning ducts under nonfully developed flow is a crucial problem that must be addressed. Based on the characteristics of the resistance in ventilation air-conditionin...Calculating the resistance of ventilation air-conditioning ducts under nonfully developed flow is a crucial problem that must be addressed. Based on the characteristics of the resistance in ventilation air-conditioning ducts, the truncation method-a computational method that is appropriate for nonfully developed flow boundary conditions-was proposed in this study. The resistance distributions in the upstream and downstream ducts from typical local components, including reducers, bends and tee ducts, were investigated. Using the resistance values of the local components under fully developed flow, the resistances that did not belong to nonfully developed flow were truncated and removed. Finally, the calculation steps of the proposed method were discussed, an engineering case study was presented, and the accuracy of the developed model was analyzed. The results showed that for the local components in the system (reducers, bends and tee ducts), their proportions of the total resistance exhibited similar trends under different width-to-height ratios. The resistance of these local components included upstream resistance, downstream resistance and their own resistance. The upstream resistance accounted for 2%–6% of the total resistance, whereas the downstream resistance of the reducers, bends and tee ducts accounted for 40%–60% of the total resistance. A functional relationship was established between the local resistance and cutoff distance of the reducers, bends and tee ducts. Hence, the truncation method can calculate the local resistance from the cutoff distance. Moreover, in the presented engineering case study, the error between the actual measured resistance values and those simulated with the truncation method was only 4.28%, which was far less than that of the results simulated with the traditional calculation methods (53.64%).展开更多
文摘Discusses the significance of induction motor constant resistance (IM R) load on the lower part of the PV curve of a power system and determines the conditions for stable operation of IM R load using fuzzy techniques and load flow.
基金the National Natural Science Foundation of China(Nos.51709246,52171280,51609220,U1806229)。
文摘When the ship is sailing at sea,wave added resistance has great influence on the rapidity and economy of the ship.With the increasing pressure of energy and environmental protection,IMO has proposed the EEDI formula of the newly built ships,which restricts the energy consumption standard of civil ships more strictly.Therefore,a panel method based on three dimensional potential flow theory is proposed to study the problem of wave added resistance in this paper.Firstly,the method solves the motion responses of the ship in the time domain,and then calculates the wave added resistance of the ship by near-field pressure integration method.The wave added resistance of S175 container ship in head and oblique waves are calculated and compared with the experimental data,and the accuracy of the proposed method are verified.At last,the influence of Froude number and wave direction angle on wave added resistance is studied.The proposed method provides an approach of satisfactory accuracy and efficiency for the development of high-performance new ship forms,optimization of ship hull lines,comprehensive performance evaluation of ships and practical navigation guidance.
文摘On the basis of a macro flow resistance method and the Darcy Theory,a mathematical model is elaborated to characterize the flow resistance of a bag filter serving a coal-fired power plant.The development of the theoretical model is supported through acquisition of relevant data obtained by scanning the micro structure of the bag filter by means of an electron microscope.The influence of the running time and boiler load on the flow resistance and the impact of the flow resistance on the efficiency of the induced draft fan are analyzed by comparing the results of on-site operation tests.We show that the initial operation time and the table operation time are linearly related to the flow resistance of the bag filter;with the increase of boiler load,the flow resistance of the bag filter rises approximately as a quadratic function;with the rise of resistance,the power consumption of the induced draft fan increases while the efficiency of the induced draft fan decreases.
文摘The construction of an integrated numerical model is presented in this paper to deal with the interactions between vegetated surface and saturated subsurface flows. A numerical model is built by integrating the previously developed quasi-three-dimensional （Q3D） vegetated surface flow model with a two-dimensional （2D） saturated groundwater flow model. The vegetated surface flow model is constructed by coupling the explicit finite volume solution of 2D shallow water equations （SWEs） with the implicit finite difference solution of Navier-Stokes equations （NSEs） for vertical velocity distribution. The subsurface model is based on the explicit finite volume solution of 2D saturated groundwater flow equations （SGFEs）. The ground and vegetated surface water interaction is achieved by introducing source-sink terms into the continuity equations. Two solutions are tightly coupled in a single code. The integrated model is applied to four test cases, and the results are satisfactory.
基金This research project was sponsored by the National Key R&D Program of China(No.2017YFC0702800)National Natural Science Foundation of China(No.51878533 and No.51508442)+1 种基金and Natural Science Foundation of Shaanxi Province(No.2019JM-233)Industrialization fund of Shaanxi Provincial Department of Education(No.19JC023).
文摘Calculating the resistance of ventilation air-conditioning ducts under nonfully developed flow is a crucial problem that must be addressed. Based on the characteristics of the resistance in ventilation air-conditioning ducts, the truncation method-a computational method that is appropriate for nonfully developed flow boundary conditions-was proposed in this study. The resistance distributions in the upstream and downstream ducts from typical local components, including reducers, bends and tee ducts, were investigated. Using the resistance values of the local components under fully developed flow, the resistances that did not belong to nonfully developed flow were truncated and removed. Finally, the calculation steps of the proposed method were discussed, an engineering case study was presented, and the accuracy of the developed model was analyzed. The results showed that for the local components in the system (reducers, bends and tee ducts), their proportions of the total resistance exhibited similar trends under different width-to-height ratios. The resistance of these local components included upstream resistance, downstream resistance and their own resistance. The upstream resistance accounted for 2%–6% of the total resistance, whereas the downstream resistance of the reducers, bends and tee ducts accounted for 40%–60% of the total resistance. A functional relationship was established between the local resistance and cutoff distance of the reducers, bends and tee ducts. Hence, the truncation method can calculate the local resistance from the cutoff distance. Moreover, in the presented engineering case study, the error between the actual measured resistance values and those simulated with the truncation method was only 4.28%, which was far less than that of the results simulated with the traditional calculation methods (53.64%).
