Numerical simulation of supersonic gas flow in a conical nozzle with local plasma heating and experimental results

The results of the main theoretical calculations and some experiments on local heating of the supersonic flow of gases by an external inductor with low-temperature plasma during the ionization of gases in a ceramic, conical nozzle, carried out by means of a powerful, high-frequency, electromagnetic field, are given. Numerical calculations are based on the provisions of electromagnetic field theory based on the equations of Maxwell, Navier - Stokes for gas dynamics, Saha - Eggert for ions and electrons, which make it possible to calculate the basic parameters of the inductor and the necessary specific power for heating supersonic, multicomponent, gas flows with low-temperature plasma. A model of vortexless (laminar), supersonic, stationary gas flow was used and mathematical modeling of its movement in a conical nozzle was carried out with the aim of possibly using the effect of additional heating of the gas flow with low-temperature plasma to increase the efficiency of the liquid rocket engine. It was found that in order to effectively heat the gas flow with low-temperature plasma in the design diameter, a conductivity of gases of at least σs ≥ 200 1/Ω·m is required for the initial temperature Ta = 2528 - 2674 оK and the frequency f = 27,12 MHz, which is not feasible even in the presence of a high concentration of impurities based on alkali metals. Therefore, a special device was developed - an ionizer for the combustion chamber. The use of an ionizer allows to achieve the specified conductivity for the pressure in the combustion chamber of 15 MPa (a link to the article is given in the list of references). Calculations indicate the possibility of effective heating with low-temperature plasma of the supersonic flow of gases in the initial volume of the conical nozzle, which is adjacent to the critical cross-section of the liquid rocket engine. This will allow in the future to significantly increase its specific impulse and thrust at the start, due to an increase in the flow rate of gases in the design section. It has also been determined that the parietal region of a conical nozzle has a significant temperature gradient in the radial direction, whereas along the symmetry axis of the conical nozzle, the temperature increase has a linear relationship. The results of numerical simulations are qualitatively consistent with the experiments conducted in a quartz reactor cooled by water, which made it possible to use a variety of gas and gas-liquid mixtures to select fuel with the optimal composition of components. Preliminary data obtained on a working stand with a thermal power of a quartz reactor not exceeding 4 kW are given.