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In order to solve the problem of motion interference when the wheeled pipe robot passes through the elbow and the dimension of the pipe diameter when the robot is running in the geometric irregular pipe, a kind of pipeline robot w...
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In order to solve the problem of motion interference when the wheeled pipe robot passes through the elbow and the dimension of the pipe diameter when the robot is running in the geometric irregular pipe, a kind of pipeline robot with autonomous differential characteristic and adaptive variable characteristic is designed. The robot is mainly composed of multi-axis differential mechanism, travel drive mechanism, pre-tightening mechanism and auxiliary support mechanism, and modular design of each part. According to the technical requirements and the force of the robot through the elbow, the structural design of the main transmission parts is carried out. The three-dimensional solid modeling and the dynamic analysis of the pipeline robot are carried out to verify that the mechanism can meet the requirements of the pipe robot. The results show that the pipeline robot can pass through the elbow without interference, and have a certain diameter of the adaptability and obstacle barrier capability.
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Under the influence of the skin effect and the electromagnetic coupling between multiple conductors inside the cable, the distribution parameters of the cable shows frequency variation and high non-linearity, which makes it more d...
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Under the influence of the skin effect and the electromagnetic coupling between multiple conductors inside the cable, the distribution parameters of the cable shows frequency variation and high non-linearity, which makes it more difficult to describe the broadband impedance. The current impedance model of direct drive permanent magnet synchronous generator does not consider the effects of submarine cables impedance. In this paper, we (1) establish the impedance model of grid side converter, (2) extract distribution parameters of cable based on the COMSOL-MATLAB co-simulation platform, and (3) analyze the influence of cable distribution parameters on wideband impedance characteristics of the wind power converter. The results show that the electromagnetic coupling between conductors mainly affects the cable distributed inductance and enhances the negative damping characteristics. After considering the distribution parameters, the submarine cable impedance presents multi-resonance characteristics. The longer the length is, the more obvious the multi-resonance characteristic will be, and the worse the broadband impedance characteristic of wind power converters connected to weak power grids will be.
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A distributed hydrological cycle model of irrigation district was developed based on the SWAT model (Soil and Water Assessment Tool) and the artificial-natural composite the hydrological cycle was considered. SWAT model was modifi...
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A distributed hydrological cycle model of irrigation district was developed based on the SWAT model (Soil and Water Assessment Tool) and the artificial-natural composite the hydrological cycle was considered. SWAT model was modified in the aspect of extraction of ditches, distributed subbasins and hydrologic response units, the calculation method of crop actual ET. The applicability of the model was validated in Fenhe irrigation district. The information on hydrology, weather and water use from 1996 to 2001 in the Fenhe irrigation district was used to simulate and analysis water balance. The sensitive parameters was estimated by Ens, RE and R2. The model was further validated with the monthly flow data from 2002 to 2006. The results showed that the simulated results of two monitoring points meet the estimated requirements. The RE value of the average annual runoff at Erba Station varied from -7.34% to 19.13% except a low RE value (-30.70%) in 2006. The RE of the average annual runoff at Yitang station was from -17.21% to 9.86% with an exceptional RE value (-21.13%) in 2003. From the monthly simulated results, the R2 of the monthly runoff at Erba and Yitang stations were 0.81 and 0.77, respectively. The Ens of monthly runoff were 0.72 and 0.65, respectively. Modified SWAT model was applicable for water balance simulation at Fenhe irrigation district.
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摘要 :
A distributed hydrological cycle model of irrigation district was developed based on the SWAT model (Soil and Water Assessment Tool) and the artificial-natural composite the hydrological cycle was considered. SWAT model was modifi...
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A distributed hydrological cycle model of irrigation district was developed based on the SWAT model (Soil and Water Assessment Tool) and the artificial-natural composite the hydrological cycle was considered. SWAT model was modified in the aspect of extraction of ditches, distributed subbasins and hydrologic response units, the calculation method of crop actual ET. The applicability of the model was validated in Fenhe irrigation district. The information on hydrology, weather and water use from 1996 to 2001 in the Fenhe irrigation district was used to simulate and analysis water balance. The sensitive parameters was estimated by Ens, RE and R2. The model was further validated with the monthly flow data from 2002 to 2006. The results showed that the simulated results of two monitoring points meet the estimated requirements. The RE value of the average annual runoff at Erba Station varied from -7.34% to 19.13% except a low RE value (-30.70%) in 2006. The RE of the average annual runoff at Yitang station was from -17.21% to 9.86% with an exceptional RE value (-21.13%) in 2003. From the monthly simulated results, the R2 of the monthly runoff at Erba and Yitang stations were 0.81 and 0.77, respectively. The Ens of monthly runoff were 0.72 and 0.65, respectively. Modified SWAT model was applicable for water balance simulation at Fenhe irrigation district.
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摘要 :
In order to enhance the performance of gas turbine and maintain the blade material endurance within operating temperature range, cooling channels are made within the blade to extract the heat from materials. However, nowadays hot ...
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In order to enhance the performance of gas turbine and maintain the blade material endurance within operating temperature range, cooling channels are made within the blade to extract the heat from materials. However, nowadays hot gas temperature has been substantially higher than allowed material temperature. Therefore, optimizing internal cooling schemes is necessary to get higher thermal efficiency and safe operation during life cycle in modern gas turbines. In this paper, the numerical simulation method is used for getting the internal cooling passage pressure coefficient and temperature distribution. 6 times amplification model which is turbine blade internal cooling channel has been studied. Hydraulic diameter of the channel inlet is 11. 2mm. The ratio of Radius gyration and channel inlet hydraulic diameter is 46. Realizable k-ε turbulence model with enhanced wall function is used. The simulation has been done at Rotation number Ro = 0. 0879 and Ro = 0. 0 with different Reynolds number from Re=5000 to 20000, and discharge ratio of each outlet is 27%49%24%. Compare and analyze the characteristics of flow and heat transfer when rotating and nonrotating. The results show that:l) the flow characteristics of rotating channel are different from characteristics of non-rotating channel due to the rotation-induced secondary flow which is produced by coriolis force, buoyancy force and centrifugal force. The pressure coefficients reduce 13. 5% under rotating condition. 2) Increase the Rotation number which lead to average Nu number increasing and flow resistance decreasing. However, the heat transfer characteristics of different side are difference. Coriolis force is the most intensive ingredient in heat transfer in rotation passage. The heat transfer on pressure-wall is enhanced by the radial outflow, but reduced on the suction-wall. The heat transfer on suction-wall is enhanced by the radial inflow, but reduced on the pressure-wall. 3) The average Nusselt number increases as increasing Reynolds number. The Nusselt number distribution on rotating ribbed channel surface is similar with non-rotation.
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摘要 :
In order to enhance the performance of gas turbine and maintain the blade material endurance within operating temperature range, cooling channels are made within the blade to extract the heat from materials. However, nowadays hot ...
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In order to enhance the performance of gas turbine and maintain the blade material endurance within operating temperature range, cooling channels are made within the blade to extract the heat from materials. However, nowadays hot gas temperature has been substantially higher than allowed material temperature. Therefore, optimizing internal cooling schemes is necessary to get higher thermal efficiency and safe operation during life cycle in modern gas turbines. In this paper, the numerical simulation method is used for getting the internal cooling passage pressure coefficient and temperature distribution. 6 times amplification model which is turbine blade internal cooling channel has been studied. Hydraulic diameter of the channel inlet is 11. 2mm. The ratio of Radius gyration and channel inlet hydraulic diameter is 46. Realizable k-ε turbulence model with enhanced wall function is used. The simulation has been done at Rotation number Ro = 0. 0879 and Ro = 0. 0 with different Reynolds number from Re=5000 to 20000, and discharge ratio of each outlet is 27%49%24%. Compare and analyze the characteristics of flow and heat transfer when rotating and nonrotating. The results show that:l) the flow characteristics of rotating channel are different from characteristics of non-rotating channel due to the rotation-induced secondary flow which is produced by coriolis force, buoyancy force and centrifugal force. The pressure coefficients reduce 13. 5% under rotating condition. 2) Increase the Rotation number which lead to average Nu number increasing and flow resistance decreasing. However, the heat transfer characteristics of different side are difference. Coriolis force is the most intensive ingredient in heat transfer in rotation passage. The heat transfer on pressure-wall is enhanced by the radial outflow, but reduced on the suction-wall. The heat transfer on suction-wall is enhanced by the radial inflow, but reduced on the pressure-wall. 3) The average Nusselt number increases as increasing Reynolds number. The Nusselt number distribution on rotating ribbed channel surface is similar with non-rotation.
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摘要 :
Increased turbine inlet temperature is a guarantee of high thermal efficiency of gas turbines. However, temperatures in the hot gas path far exceed allowable material temperatures of turbine blades. Therefore, the blades are usual...
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Increased turbine inlet temperature is a guarantee of high thermal efficiency of gas turbines. However, temperatures in the hot gas path far exceed allowable material temperatures of turbine blades. Therefore, the blades are usually cooled by using extracted compressor air to flow through internal serpentine cooling channels. In order to provide better prediction of the methods to simulate heat transfer and flow on the internal channel, this paper mainly takes numerical simulation to investigate six kinds of different turbulence models and two wall functions for S-bend duct with ribs. Six turbulence models are employed for the predictions of these strongly strained turbulent flows, namely k-epsilon model (k -ε), RNG k-epsilon model (RNG k -ε), SST model, BSL model, kOmega model (K -ε) and SSG Reynolds Stress model. Two wall functions are employed for the channel wall, which contain scalable wall functions and automatic wall functions. Wall functions are the most popular way to account for wall effects. In CFX, Scalable Wall Functions are used for all turbulence models based on the εequation. Fork-ε based models (including the SST model), an Automatic near-wall treatment method is applied. And then in order to compare this numerical simulation with experimental results, this paper has taken transient liquid crystal technique to investigate the heat transfer on the internal channels. The studied Reynolds numbers is 17625, and main flow temperature is 33OK. Both channel-1 and Channel-3 are trapezoidal shape, and channel2 is a rectangular channel, the airflow get into the entrance of the channel-1, and it outflow through the outlet-1, outlet-2 and Trailing edge's outlet-3, and outflow ratio is 1:2:1. The ribs have staggered arrangement in the pressure-surface and the suctionsurface, channel-1 and channel-2 are rectangular ribs, channel-3 is triangle ribs. Detailed comparison is made among the results from the models and available experimental data to test the ability of the models in predicting these fluid flow and wall heat transfer problems. The results show that: it is critical to properly use turbulence models for numerical simulation. Under the same boundary conditions, the different turbulence models can carry out the different calculation' s results, and the wall functions have an important effect on numerical simulations.
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摘要 :
Increased turbine inlet temperature is a guarantee of high thermal efficiency of gas turbines. However, temperatures in the hot gas path far exceed allowable material temperatures of turbine blades. Therefore, the blades are usual...
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Increased turbine inlet temperature is a guarantee of high thermal efficiency of gas turbines. However, temperatures in the hot gas path far exceed allowable material temperatures of turbine blades. Therefore, the blades are usually cooled by using extracted compressor air to flow through internal serpentine cooling channels. In order to provide better prediction of the methods to simulate heat transfer and flow on the internal channel, this paper mainly takes numerical simulation to investigate six kinds of different turbulence models and two wall functions for S-bend duct with ribs. Six turbulence models are employed for the predictions of these strongly strained turbulent flows, namely k-epsilon model (k -ε), RNG k-epsilon model (RNG k -ε), SST model, BSL model, kOmega model (K -ε) and SSG Reynolds Stress model. Two wall functions are employed for the channel wall, which contain scalable wall functions and automatic wall functions. Wall functions are the most popular way to account for wall effects. In CFX, Scalable Wall Functions are used for all turbulence models based on the εequation. Fork-ε based models (including the SST model), an Automatic near-wall treatment method is applied. And then in order to compare this numerical simulation with experimental results, this paper has taken transient liquid crystal technique to investigate the heat transfer on the internal channels. The studied Reynolds numbers is 17625, and main flow temperature is 33OK. Both channel-1 and Channel-3 are trapezoidal shape, and channel2 is a rectangular channel, the airflow get into the entrance of the channel-1, and it outflow through the outlet-1, outlet-2 and Trailing edge's outlet-3, and outflow ratio is 1:2:1. The ribs have staggered arrangement in the pressure-surface and the suctionsurface, channel-1 and channel-2 are rectangular ribs, channel-3 is triangle ribs. Detailed comparison is made among the results from the models and available experimental data to test the ability of the models in predicting these fluid flow and wall heat transfer problems. The results show that: it is critical to properly use turbulence models for numerical simulation. Under the same boundary conditions, the different turbulence models can carry out the different calculation' s results, and the wall functions have an important effect on numerical simulations.
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摘要 :
The development process of 268kW two-stroke integral gas engine-compressor is introduced. The influence of different ignition advanced angles and various volumes of gas scavenging chamber on the performance of power cylinder and t...
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The development process of 268kW two-stroke integral gas engine-compressor is introduced. The influence of different ignition advanced angles and various volumes of gas scavenging chamber on the performance of power cylinder and the working situation of the power cylinder (134KW) under different loads are emphatically analyzed. Moreover, the design characteristics, the improvement of main structure design, the performance measurement and the general situation of the reliability test are also presented.
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