Numerical Simulation of the Characteristics of Heavy Particles in Bar-Plate DC Positive Corona Discharge Based on a Hybrid Model

An improved, multicomponent, and 2-D hybrid model is presented in detail for the simulation of bar-plate dc corona discharge in dry air (O
₂
:N
₂
=1:4). The model is based on plasma hydrodynamics, and chemical models in which 12 species (e, O, O
₂
, O
₃
, O
₂
⁺
, O
₄
⁺
, O
₂
^-
, O
^-
, N
₂
, N
₂
⁺
, N
₄
⁺
, and N
₂
O
₂
⁺
) and 32 collision reactions between such species are considered. In addition, the photoionization and secondary electron emission effects are also incorporated within the model. The simulation is established with a bar-plate electrode configuration with an interelectrode gap of 5.0 mm, where the positive dc voltage applied to the bar is 3.0 kV, the pressure in air discharge is fixed at 1.0 atm, and the gas temperature is assumed to be a constant (300 K). Using individual discharge current waveform and V-I curve, the effectiveness of this developed model is validated by experimental results. With this hybrid model, electric field distribution and net space charge distribution at four representative time points during a pulse are discussed. Moreover, the composition and distribution of particles are analyzed emphatically. The obtained results show that, among all reactions, the reaction rate of R
₁
, which is the collision reaction between electron and N
₂
is maximal, whereas the N
₂
⁺
density is significantly less than O
₄
⁺
and O
₂
⁺
. O
₂
^-
has the largest number of negative ions and thus restrains the electron collision process significantly. In addition to N
₂
and O
₂
, O is the major neutral particle, but owing to the small quantity of neutral particles, the effect is relatively weak. The obtained results will provide valuable insights into the physical mechanism of positive corona discharge in air.