EXPERIMENTAL STUDY OF THE EFFECT OF THE NOZZLE-TO-PLATE SPACE ON THE FREE TURBULENT IMPINGING JET FLOW

Using the IFA-300 Hot Wire/Film Anemometer, the detailed measurementresults are obtained on the effect of the nozzle-to-plate space on thefree turbulent impinging jet flow field.The Reynolds number considered is 23000, and the space ofnozzle-to-plate is set as 2D(D is the diameter of the pipe), 4D,6D,8D above the impingementplate, respectively. It is shownthat the "damping"effect mainly exists in the zone of 0.5D from theimpingement wall. Under asmall nozzle-to-plate space, the radial velocity decreases more rapidlythan that under a largeone. And the velocity under the small space is somewhat smaller. In thearea r/D ≤1.5, the trend and the quantity of the turbulent kineticenergy of the small and large spaces are quite different. For the otherradial positions, the trend is the same though the quantity under alarger space is greater. It also shows that the flow structure isgreatly changed when the nozzle-to-plate space is around Z/D=6, whichis attributed to the effect of the potential core of the jet.Consequently, the turbulent kinetic energy keeps large atthe end of the potential core and in the area of several diametersdownstream of it.