A Novel Engineering Calculation Method for the Substation Grounding Potential Induced by Subway Stray Current Based on Monitoring Data of Track Electric Section

Author(s):  
Wang DongQing ◽  
Cao Nan ◽  
Meng Tao ◽  
Jianwei Zhang ◽  
Zhiwei Xue ◽  
...  
Author(s):  
J. S. Chin

A practical engineering calculation method has been formulated for commercial multicomponent fuel stagnant droplet evaporation with variable finite mass and thermal diffusivity. Instead of solving the transient liquid phase mass and heat transfer partial differential equation set, a totally different approach is used. With zero or infinite mass diffusion resistance in liquid phase, it is possible to obtain vapor pressure and vapor molecular mass based on the distillation curve of these turbine fuels. It is determined that Peclet number (Pef) is a suitable parameter to represent the mass diffusion resistance in liquid phase. The vapor pressure and vapor molecular mass at constant finite Pef is expressed as a function of finite Pef, vapor pressure, and molecular mass at zero Pef and infinite Pef. At any time step, with variable finite Pef, the above equation is still valid, and PFsPef=∞, PFsPef=0, MfvPef=∞, MfvPef=0 are calculated from PFsPef≡∞, PFsPef≡0, MfvPef≡∞, MfvPef≡0, thus PFs and Mfv can be determined in a global way which eventually is based on the distillation curve of fuel. The explicit solution of transient heat transfer equation is used to have droplet surface temperature and droplet average temperature as a function of surface Nusselt number and non-dimensional time. The effect of varying com position of multi-component fuel evaporation is taken into account by expressing the properties as a function of molecular mass, acentric factor, critical temperature, and critical pressure. A specific calculation method is developed for liquid fuel diffusion coefficient, also special care is taken to calculate the binary diffusion coefficient of fuel vapor-air in gaseous phase. The effect of Stefan flow and natural convection has been included. The predictions from the present evaporation model for different turbine fuels under very wide temperature ranges have been compared with experimental data with good agreement.


Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1091 ◽  
Author(s):  
Lejun Ma ◽  
Xingnan Zhang ◽  
Huan Wang ◽  
Changjun Qi

Water and flow reductions in the channels downstream of water storage and hydropower projects have significant impacts on aquatic ecosystems. Understanding and analyzing the ecosystem status is of great significance to facilitate the protection of riverine ecosystems. A database was established based on the 2000–2017 environmental impact assessment (EIA) reports on water storage and hydropower projects in China, and corresponding analysis software was built based on an ArcGIS spatial analysis platform. The projects in China are mainly found in the Yangtze and Pearl River basins and in south-western China. The hydropower projects have a larger influence than the water storage projects on the flow of downstream rivers sections, and most of the hydropower projects, especially the water diversion projects, cause flow reductions in the downstream rivers. An ecological flow management mechanism in China implemented in 2006 provided a promising method to alleviate river flow reductions. However, there is still only one kind of ecological flow calculation method and few ecological flow regulation measures in use. Based on the advantages and problems of the existing ecological flow management system, this paper proposes a management scheme based on a regional-engineering calculation method. The results can facilitate decision making in ecological flow management.


2012 ◽  
Vol 190-191 ◽  
pp. 936-939
Author(s):  
Chao Li ◽  
Yun Jiang Liu ◽  
Heng Yang Zhang ◽  
Xiao Peng Yang ◽  
Feng Wang

To grasp Complex characteristics of shortwave (HF) channel is the key and difficulty to research HF communication. On the premise of comprehending the ionosphere prediction method in the Asia Oceania region, HF frequency prediction method recommended by the International Telecommunication Union (ITU) is improved in this paper, and the engineering calculation method of predicting HF frequency in the Asia Oceania region is concluded and summarized. Comparing with the ITS (the Institute for Telecommunication Science) software’s predicting result, the method is improved to some extent in time availability and SNR in the receiving point.


2020 ◽  
Vol 1003 ◽  
pp. 92-97
Author(s):  
Wen Hao Liu ◽  
Rui Xiang Bai ◽  
Kang Su ◽  
Jian Chao Zou ◽  
Da Liu ◽  
...  

It is convenient for designers to get the buckling loads of sparse stiffened panels quickly by using engineering calculation method to analyze the stability of composite stiffened panels, but it is still unable to meet the accuracy requirements of analysis of dense stiffened panels. The buckling loads of stiffened panels are closely related to the buckling modes. Based on capturing and analyzing the Compressive Buckling waveforms of T-shaped densely stiffened panels, this paper presents a formula for calculating the buckling loads according to the geometric coefficients. The results are very similar to those of finite element simulation, and can be used to calculate the buckling loads of sparse and dense stiffened panels with different stiffeners.


2014 ◽  
Vol 1016 ◽  
pp. 423-428
Author(s):  
Hong Shi ◽  
Yan Long Jiang ◽  
Yin Peng ◽  
Yu Fei Cai

Based on the study of the duct leak detection system of commercial aircraft in existence, the insulation structure of high temperature pneumatic duct system of the aircraft is improved with multilayer insulation method and its engineering calculation method is derived. Also, the insulation experiment platform of the high temperature pneumatic duct system is built to verify the applicability and feasibility of the engineering calculation method. The research result shows that the results from the engineering calculation method is not fit the experimental data perfectly, the margin of error is 17 percentage. The main reason is that the diversion tunnels has a little effect on the temperature distribution and in these cases parameter modification method should be adopted in the engineering calculation method. These works would be helpful for the design and optimization of the high temperature pneumatic duct system.


2012 ◽  
Vol 229-231 ◽  
pp. 2025-2028
Author(s):  
Zheng Gong ◽  
Jing Jing Wang ◽  
Mao Fa Gong ◽  
Ning Liu ◽  
Ji He Yang

According to the internal physical structure of photovoltaic cell and output V-I characteristic, the paper construct a solar module simulating model by engineering calculation method under the Simulink environment. In the light of the limited parameters of photovoltaic cell (PV), the model can give the entire output characteristic curve under the different intensity illuminations and the various temperatures. At the final of the paper, MPPT to solar module adopted a special method is researched based on the Simulink.


2013 ◽  
Vol 712-715 ◽  
pp. 1589-1592
Author(s):  
Li Bing Lu ◽  
Meng Gao ◽  
Dong Li

For multi-storey buildings,different calculation methods of cold air infiltration heat consumption have great impact on heating heat load of rooms in winter. With taking different methods,the calculation results will vary widely when architectual desigh institutes calculate room heat load. This paper compared the gap method,the ventilation rate method and the percentage method for the certain rooms infiltration heat loss,trying to make that simple and in line with the actual engineering calculation method.


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