اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدImplementation of a cathode directed streamer model in Air under different voltage stresses
344
0
0.0
(
0
)
تأليف
F Boakye-Mensah
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
To find a viable alternative to SF6 with growing climate change regulations, proper evaluation of alternatives such as compressed air ought to be done. For medium voltage applications, the withstand voltage is used as the dimensioning criteria and this is dependent on the initiation and propagation of streamers which are precursors to electrical breakdown. For design optimization, a thorough understanding of the initiation and propagation mechanisms of such electrical discharges under different stresses, pressure etc. ought to be studied experimentally and numerically also via a predictive model. Most of the numerical studies have so far been done via homemade codes as streamer models are not readily available in commercial software because of the complexity and non-linearity of such computations. Recently, with the increased robustness of the plasma module of the commercial finite element software, COMSOL(tm) Multiphysics, streamer discharge models can be developed with reasonable accuracy. In this paper, an implementation and validation approach is presented for streamer evolution in air for different voltage stresses. Results of simulations for short gaps ($le$ 5 mm) under Standard Temperature and Pressure (STP) conditions have been presented, analyzed and compared with some classical papers to evaluate the suitability of such a model for further studies of non-thermal electrical discharges. Index Terms-medium voltage, streamer discharges, eco-friendly gas, numerical models.
قيم البحث
اقرأ أيضاً
This paper demonstrates and studies helium atmospheric pressure plasma jet comprised of series of repetitive streamer breakdowns, which is driven by a pure DC high voltage (auto-oscillations). Repetition frequency of the breakdowns is governed by the
geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV/cm. Repetition frequency of the streamer breakdowns excited using this principle can be simply tuned by reconfiguring the discharge electrode geometry. This custom-designed type of the helium plasma jet, which operates on the DC high voltage and is comprised of the series of the repetitive streamer breakdowns at frequency about 13 kHz, is demonstrated.
Self-organized patterns of cathode spots in glow discharges are computed in the cathode boundary layer geometry, which is the one employed in most of the experiments reported in the literature. The model comprises conservation and transport equations
of electrons and a single ion species, written in the drift-diffusion and local-field approximations, and Poissons equation. Multiple solutions existing for the same value of the discharge current and describing modes with different configurations of cathode spots are computed by means of a stationary solver. The computed solutions are compared to their counterparts for plane-parallel electrodes, and experiments. All of the computed spot patterns have been observed in the experiment.
This paper describes how to light several microdischarges in parallel without having to individually ballast each one. The V-I curve of a microhollow cathode discharge is characterized by a constant voltage in the normal glow regime because the plasm
a is able to spread over the cathode surface area to provide the additional secondary electrons needed. If one limits the cathode surface area, the V-I characteristic can be forced into an abnormal glow regime in which the operating voltage must increase with the current. It is then possible to light several microdischarges mounted in parallel without ballasting them individually.
A model is proposed that considers aging and rejuvenation in a soft glassy material as respectively a decrease and an increase in free energy. The aging term is weighted by inverse of characteristic relaxation time suggesting greater mobility of the
constituents induce faster aging in a material. A dependence of relaxation time on free energy is proposed, which under quiescent conditions, leads to power law dependence of relaxation time on waiting time as observed experimentally. The model considers two cases namely, a constant modulus when aging is entropy controlled and a time dependent modulus. In the former and the latter cases the model has respectively two and three experimentally measurable parameters that are physically meaningful. Overall the model predicts how material undergoes aging and approaches rejuvenated state under application of deformation field. Particularly model proposes distinction between various kinds of rheological effects for different combinations of parameters. Interestingly, when relaxation time evolves stronger than linear, the model predicts various features observed in soft glassy materials such as thixotropic and constant yield stress, thixotropic shear banding, and presence of residual stress and strain.
The power of microwave generation in a nonrelativistic electron beam with virtual cathode formed in a static retarding electric field (low-voltage vircator system) has been studied experimentally and by means of numerical simulation within the framew
ork of a one-dimensional theory. The limits of applicability of the one-dimensional theory have been experimentally determined.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
