Experimental Analysis of Wetting Delay during Jet Impingement Quenching of High Temperature Brass Block

A model for the prediction of the wetting delay through jet impingement quenching of a high temperature brass block has been carried out in this study. The Liquids used for jet impingement on the brass surface are water and emulsion of cutting oil (used in machine shop) and water at a proportion of 1:20.The varying parameters used for the analysis are different velocities of jet (3m/s, 5m/s, 10m/s) and initial block temperature from 250< C to 450< C at an interval of 50< C. The wetting delay and wetting front propagation varied for different test conditions. When a liquid jet was impinged on the heated surface of the brass block, the jet remains stagnant up to a small region and the surface temperature decreases very slowly with time. After a certain interval, the surface temperature decreases at faster rate and the wetting front starts to move in the radial direction. The time that passes during the stagnant period of the wetting front is the wetting delay. The wetting delay in case of emulsion of cutting fluid is much higher as compared to water. The evidence was clear for wetting delay measurement for water from graphical analysis but for the emulsion it is not as evident as in many cases the temperature drops linearly with time and the wetting delay can’t be actuated exactly. The water wave front propagates throughout the surface but in case of the emulsion the wetting front does not even cover half of the total metal surface after a long interval of time. The effect of different experimental parameters on the wetting delay is also observed in the present study. The characteristics of the wetting delay are influenced by jet velocity and initial block temperature. For higher jet velocity and lower initial block temperature wetting delay decreases.