Elektrodinės sistemos

Abstract

One of the most important factors, which determines electrostatic filter efficiency, is created in its corona discharge field strengt pollutant particle charge and force, effected charging fraction depend on its size and distribution character. Transversal air stream moving direction in a one- stage electrostatic filter with spring collection electrodes, pollutant particle collection process is going on in an electrodes system “wire discharge electrode in spiral spring centre” corona discharge field. A precise solution of corona discharge equation for this three-dimensional electrode system does not exist. We can use approximate calculation methods. Most of them are based on an assumption, that during corona discharge field forces lines do not change, comparing them with an electrostatic field which was before the beginning of discharge. So electrostatic field distribution simulation can be analysed as the first corona discharge field calculation stage. The second objective of distribution calculation is theoretical assumption about of possible change of approximate calculations space electrode system “wire in spring” into a one-dimension system “wire in cylinder”, for which an analytical discharge field equation solution recand validity check were obtained (the field lines distortions near the spring surface, when a winding step is small, are not significant. Particle charging processes at the field edge are weaker). Numerical finite elements method for electrostatic field distribution calculation was used. Electrostatic field distribution is calculated by solving the Laplas equation. An investigated area is approximated with discrete finite elements totality. All calculations are carried out on an approximating area by a certain amount of chosen elements, accepting a certain error. We can decrease a calculation error (at a fixed amount of element’s) by using as few elements as possible in areas with the greatest gradient and increasing element dimensions, where the gradient is smallest. The task is solved by finite elements method, using quadrangular and triangular linear elements. The galorkin method was used for finite elements equations system solution. The geometric parameters of calculation area and electrostatic field potentials at its edges are presented in Fig. 1. Finite elements net for calculation area is showed in Fig. 2. Initial calculating results - potential distribution, are presented in Fig. 3. Specified potential change calculation area at the edges character, new finite elements net was formed. Field strength distribution calculation results are presented in Fig. 4. Checking spring windings step and spring wire diameter influence on field distribution, in the initial calculation area (fig.l) parameters were changed: the distance between the rings was increased from 10 to 20 mm and the ring wire diameter - from 3 to 7 mm. A new finite elements net was formed and potential meanings were calculated (fig. 5). In the second case we can register a more clear field distortion between the rings. The presented calculation examples show, that calculated geometric dimensions (fig. 1) in an electrode system “wire in spring”, when spring winding steps are small, electrostatic field potentials up to 500 - 600 V practically are not distorted, theirs bends for meanings 200 - 300 V are not significant and only 150 - 100 V and a smaller potential field interferes between windings. This weak edge field influence on particle collection is not decisive. A theoretical assumption about an electrode system “wire in spring” change into a system “wire in cylinder” in approximate calculations is well - grounded.