FLOW FIELD AND HEAT TRANSFER IN SUPERSONIC AIR PLASMA JETS: EXPERIMENT ON RF-PLASMATRON AND CFD MODELING
The results of experimental and numerical study of the flow field and heat transfer in under-expanded air plasma jets in the wide domain of the characteristic parameters are presented. The experiments have been performed by the 100-kW RF-plasmatron equiped with a 80-mm diameter plasma torch and the sonic nozzles with the exit sections of 30 and 40 mm diameter. The digital photographs of the flow patterns for different location of the 20-mm diametr cylindrical water-cooled model with a flat nose in under-expanded air plasma jets are done. The stagnation point heat flux to a cold copper surface and stagnation pressure along jet axis are measured for different values of the air mass flow rate through the plasma torch, energy input in plasma, diameter of the sonic nozzle exit and ground pressure in the test chamber. For the RF-plasmatron test conditions the numerical computations of the flow field of 11-species chemically reacting partially ionized air mixture in the plasma torch and under-expanded jets over the cylindrical test model. Numerical technique is based on the complex of the computer codes for the numerical solution of the Navier-Stokes equations for the azimuthally swirling flow and special code-generators wich interact with tha data bases for the thermodynamic and transport properties of the specific gas components. The one-temperature (<i>T </i>= <i>T</i><sub><i>V</i></sub><i> </i>= <i>T</i><sub><i>e</i></sub><i></i>) chemically nonequilibrium model and three-temperature (<i>T </i>≠ <i>T</i><sub><i>V</i></sub><i> </i>≠ <i>T</i><sub><i>e</i></sub><i></i>) chemically and thermally nonequilibrium models have been used. Detailed comparison and an analysis of the experimental data and numerical results for the flow patterns around the cylindrical model with a flat nose, distributions of the stagnation point heat flux and pressure along the air jet axis are curried out. In the first supersonic barrel the data of the stagnation point heat flux to cold copper surface and stagnation pressure are found to be in good agreement with the numerical results obtained using both thermally equilibrium and nonequilibrium thermochemical models. Some thermally nonequilibrium effects are observed in the numerical results for the flow field down stream of the first barrel. In this part of the flow the three-temperature model appeares to be in better agreement with the experimental data then the one-temperature model.