Experiment and simulation of electron density distribution in discharge plasma at hypersonic speed

Pulsed discharge can generate high density and high dynamic plasma, which has promising application prospects in the field of stealth technology for high-speed aircraft. To study the evolution process of pulsed discharge plasma jet in a hypersonic flow field, the pulsed discharge experiment was performed in a hypersonic wind tunnel with 8 M in this paper. The plasma evolution process and electron density were measured by a high-speed schlieren device and spectrum acquisition system. A shock wave appeared after the blast wave generated by the discharge interacted with the external flow field. In the region below the shock wave, the plasma jet flowed downstream and produced a plasma layer. The electron density of the jet increases with the injected energy, and the peak density reaches 5.28 × 1015 cm−3. Due to the limitations of experimental measurements, based on the Navier–Stokes equations and the air dissociation and ionization model, including 11 components and 20 chemical reactions, a simulation for the experimental process was performed. At the injected energy of 495 and 880 mJ, the difference between the simulated electron density and the experimental value is 16.09% and 15.34%, respectively. The thickness of the plasma layer initially increases and then decreases over time, with higher injected energy leading to a thicker layer. Specifically, when 880 mJ of energy is injected, the plasma layer can reach a maximum thickness of 6.69 cm. The collision frequency fluctuates around 1 GHz, and the collision frequency at the upper edge of the plasma layer is large.