Velocity field measurements in a swirled gas flow by thermal imaging technique

Carrying out fundamental experimental study of flow structure and heat and mass transfer in strongly swirled chemically reacting and inertial single-phase and two-phase flows under essentially 3D conditions is quite a difficult problem due to a lack of velocity field measurements by panoramic technique. Therefore, in the present work we propose newly developed thermal imaging technique, which is effected by injecting a hot air into the cold flow and registering temperature difference between the jets either on the metal walls of the working channel, or on the grids inside the flow by means of thermal imaging system. The proposed technique has been used to study a certain group of unexplored vortex flows in a confined spatial domain characterized by common features such as tangential injection of gas-dispersed media providing multifold circulation, as well as continuous longitudinal ejection of this media across the total breadth of a swirled flow after encountering with the inlet jets. At a response level of thermal imaging system of 0.1 C at the temperature 300 K, snapshot resolution rate of 100 /spl times/ 100, readout time of 1 sec and the temperature of "tinting" air of /spl sim/ 100 C, up to eight temperature graduations could be determined on the metal walls and grids of the model. These graduations conform to various velocities. Vortex cores, air ejection after crossing the inlet jets etc. could be observed as well. So far as literature analysis shows, the described thermal imaging technique has been employed for the first time to study aerodynamics of complex spatial flows.