The effect of the geometry of the discharge channel in a high-frequency plasmatron on heat transfer in high-enthalpy subsonic air jets

An experimental study of the heat transfer in a $100$ kW high-frequency plasmatron was performed for three configurations of a discharge channel with a conical, water-cooled nozzle with exit diameters of $30$ mm, $40$ mm, or $50$ mm. The dynamic pressures and heat f luxes to a water-cooled copper model with a $20$-mm front flat face were measured in high-enthalpy subsonic air jets in a generator power range between $20$ and $75$ kW. The flow in the discharge channel and the subsonic dissociated air jet flow over the model were numerically studied under the experimental conditions in a high-frequency plasmatron with the Navier–Stokes and the Maxwell equations. Based on a comparison of the experimental and calculated data on heat transfer, the enthalpy at the outer edge of the boundary layer and velocity on the flow axis in front of the model were recovered. With the local heat-transfer simulation theory, the numerical results for a flow over the model were used to establish the correspondence between the parameters of the plasma flow in a high-frequency plasmatron and the conditions of the entry of a blunt-nosed body with a hypersonic velocity into the atmosphere; the altitude, velocity, and the radius of curvature of the body nose with respect to the operating conditions of a high-frequency generator were calculated.