Research On The Characteristics Of Heat Dissipation And Carbon Particle Flow In The Carbon Powder Collector For Hydro-generator

With the development of the hydropower industry,the power station pays more and more attention to the safety and stability of the generator set operation..The current collecting device is a key component of the hydro-generator to connect the excitation current into the rotor.During the process of conducting excitation current,the circular distributor ring and the carbon brush generate a large amount of heat and rub together generate a large number of fine carbon powder.However the overheating of the circular distributor ring causes the relevant insulation equipment in the device to rapidly age and fail,and the accumulation of a large amount of carbon powder in the current collecting device can lead slip ring positive and negative short-circuited and deflagration,which will seriously damage the safe operation of the generator set.In this paper,the internal flow,heat dissipation characteristics and particle trajectory of toner particles in the flow field are studied by means of finite element numerical simulation and experimental verification,taking the carbon powder collecting device as the research object.This paper provides some theoretical guidance for the improvement of the collecting current device and the optimization of the carbon powder collection device.In this thesis,a realizable k-ε turbulence model is used to simulate the fluid flow in a carbon powder collector,and the results are compared with those of an equal-scale experimental rig.Based on the VGS hydro-generator test unit of the left bank power station of the three Gorges Project,the heat source composition of the collector is determined in the process of the rated excitation,and the heat dissipation of the collector installed with the carbon powder collection device under the rated condition is further simulated.The results are in good agreement with the average temperature values on the collector surface of the test unit.Furthermore,when one and two dust-removing fans in the carbon powder collection unit are damaged,the heat dissipation characteristics of the collector under the rated condition of the excitation system of the VGS generator set are simulated.It is known that the generator set can still operate safely under these two conditions.Finally,after three months of trial operation,the collection of carbon powder is investigated,and the particle size distribution of dropped carbon powder is measured and analyzed by laser intensity analyzer.Based on this,the trajectories of the particles with particle sizes of 10μm,15μm,30μm,60μm and 100μm in the flow field are simulated.It is found that:(1)The main accumulated position of the carbon powder is the same as that of the observation,but only a very small amount of carbon powder particles are deposited on the lower edge of the dust collecting hood;(2)If the particle size is less than 30μm,it needs a longer time to get away from the influence of vortex flow,and there is only accumulated on the upper surface of the carbon brush at the lower collector ring;(3)60μm and 100μm carbon powder particles can be quickly sucked out by the dust removal fan or deposited on the upper surface of the carbon brush at the lower collector ring and the inlet section of the suction hose.