Investigation Of Comb-type Pulse Forming Line Based On Propylene Carbonate

Development of pulsed power technology is towards longer duration and more compact structures.High power pulse generator based on liquid dielectric pulse forming line is one of the important technical approaches in this field.The propylene carbonate pulse forming line(PFL)adopts high permittivity medium,which has advantages of high insulation strength and wide range of temperature adaptation.It can be used for pulse generator to obtain long pulse output and realize maintenance-free operation.The comb-type pulse forming line adopted a comb-type slow-wave structure,and by fully utilizing the internal space of the forming line,the pulse width is further lengthened,and the type of the slow-wave structure is widened.Hence,it is significant to study comb-type PFL based on propylene carbonate.In this thesis,focusing on the theoretical analysis of dispersion characteristic,numerical simulation of field-circuit and exploration research of application in pulsed power,it is systemically investigated for the comb-type PFL based on propylene carbonate.Research results set a solid foundation for the application of comb-type PFL and show a promising prospect for the future.Main contents are shown as follows.(1)Theoretical analysis of comb-type PFLUsing the spatial structure of the comb-type PFL,a method is proposed to calculate the electrical parameters of the comb-type forming line.And the calculated value is similar to the measured value.Considering the periodic structure of the comb-type forming line,it is converted into a LC equivalent circuit diagram.Based on the dispersion characteristics of the pulse forming network,the dispersion characteristics of the comb-type forming line is derived.Furthermore,the group velocity of the comb-type forming line is obtained.And the output pulse width of the comb-type forming line is also theoretically derived.(2)Numerical simulation of comb-type PFLSimulation was carried out on the comb-type forming line.Based on the calculated parameters,the electrical circuit is simulated.The output pulse width is obtained,which verifies the correctness of the theoretical derivation.The simulation on the radial line shows that the radial line can also lengthen the pulse duration,which is compared with comb-type forming line.(3)Application research of comb-type PFLThe comb-type PFL based on propylene carbonate is developed.The liquid dielectric was purified by ion exchange,and the resistivity was increased to 20 M?·cm or more.Considering the practical application of the pulse generator,the experimental study on the temperature adaptability of propylene carbonate showed that the breakdown field strength of propylene carbonate increased with the increase of temperature.The pulse generator based on comb-type PFL was developed.With a 40 cm diameter and a 70 cm length,the comb-type PFL can operate in the charging voltage of 850 kV,and its average energy storage density is about 20 J/L.Accordingly,the generator can generator the output pulse with voltage amplitude up to 500 kV,output power of about 20 GW,and duration(FWHM)of about 64 ns.Compared with the comb-type PFL based on propylene carbonate,propylene carbonate-based nano-fluid comb-type PFL has a 12% increase in dielectric strength and a 25% increase in maximum energy storage density.So,the nano-fluid comb-type PFL is more potential.