Study On Oil Storage And Drainage Performance Of Cylindrical Accident Oil Pool Based On Mixture Model

In the world,due to technical and historical reasons,excessive transformer accidents have caused huge casualties and economic losses to the society.Transformer accidents have occurred from time to time,and the state has increasingly stricter requirements for the disposal of transformer waste oil.As the last "protective door" of the substation,the accident oil pool has not been able to attract sufficient attention from relevant designers at home and abroad due to its low utilization rate.The paper takes the cylindrical accident oil pool of a 500 kV substation in Wuhan City,Hubei Province as the research object,and studies the oil storage and drainage capacity of the accident oil pool.Based on the detailed investigation of the accident oil pool treatment system,the geometric model of the accident oil pool was simplified and analyzed.Then the corresponding geometric model was established by Gambit software and a set of network was tested.The division method of the grid.Then according to the physical properties of the simulated objects(oil phase and water phase),the RNG k-ε turbulence model and the Mixture multiphase flow model and other boundary conditions are reasonably selected.Finally,the unsteady SIMPLEC algorithm and the second-order upwind style are selected by Fluent software to solve the simulation.Firstly,the influence of the accident oil droplet size on the oil storage and drainage of the accident oil pool was studied,and the particle size of the oil droplet used in the subsequent simulation was determined.Then the variation law of velocity field and concentration field in the accident oil pool under typical working conditions is analyzed,and the influences of inlet flow,temperature and water depth on the oil storage and drainage effect of the accident oil pool are analyzed.On the basis of the original accident oil pool,the structural transformation plan of the accident oil pool is proposed,and the most reasonable transformation plan is selected to carry out the physical physics experiment to verify the rationality and accuracy of the transformation plan.The main research results of the thesis are as follows:(1)The oil droplet size has an important effect on the oil storage and drainage effect of the accident oil pool.When the average droplet size increases from 100μm to 1000μm,the over-standard time increases from 713 s to 1186 s,an increase of 66.44%.At the same time,the results show that the oil pool can only separate oil droplets larger than 100μm by gravity.(2)Under typical working conditions,when the discharge time is 1186 s,the accident oil content at the exit reaches 10mg/L,which exceeds the first-level standard in the comprehensive wastewater discharge standard(GB8978-96).When the accident oil discharge is completed.The accident oil content at the exit reached 26.3mg/L,which has not exceeded the third-level standard in the comprehensive wastewater discharge standard(GB8978-96).It shows that under typical working conditions,the accident oil pool can function as oil storage and drainage.(3)The higher the temperature in the tank of the accident oil pool,the higher the separation efficiency of oil and water,and the better the oil storage and drainage effect.In the range of 5 °C-20 °C,the change of temperature has a greater influence on the maximum allowable oil leakage,while in the range of 20 °C-35 °C,the change of temperature has less influence on the maximum allowable oil leakage.When it is greater than 35 °C,the change of temperature has a tendency to increase the allowable maximum oil leakage.(4)The depth of water in the pool is not the main factor affecting the oil storage effect of the accident oil pool.However,in actual application,it is necessary to regularly check the water accumulation in the accident oil pool.When the water in the accident oil pool is too small,the water should be injected to the specified value in time to ensure that the accident oil pool is in normal working condition.(5)In the case of heavy rain,when the original accident oil pool was at 1093 s,the oil content at the exit exceeded 10 mg/L,and reached 30 mg/L at 1105 s.When the accident oil is completely discharged,the maximum oil content at the outlet is 150g/L,which far exceeds the third-level standard in the comprehensive wastewater discharge standard(GB8978-96),indicating that the accident oil pool cannot store all accident oil in the event of heavy rain..(6)Different outlets and inlet locations have little effect on the overall oil storage and drainage effect of the accident oil pool.Therefore,for the cylindrical accident oil pool,the arrangement of the oil inlet and the water outlet can give priority to the overall planning of the substation.Under the premise of meeting the planning,the angle between the outlet and the mouth should be made as large as possible.(7)Extending the drain port downwards can improve the effect of oil storage and drainage in the accident oil pool.This scheme requires earthwork construction and is recommended for use in the design of new accident oil pools.The program is difficult to retrofit the built accident oil pool and has poor economics.(8)After adding the baffle,the oil storage and drainage effect of the accident oil pool has been significantly improved.In the case of heavy rain,the maximum oil content at the exit is reduced from the original 150g/L to 205mg/L.The experimental results show that the rationality of the optimization scheme of adding baffles also proves the accuracy of the simulation method.