LAUSR

Abstract An experimental study was carried out on a laboratory-scale louvered conical infrared suppression (IRS) device to predict the air entrainment into it. A comparison has been made between the louvered conical, conical and the cylindrical IRS device based on the air entrainment ratio with increasing geometric ratio. A numerical study on the flow domain was also performed by solving the continuity and Navier-Stokes equations using the k-epsilon turbulence model. The air entrainment was compared with the experimental data and a good match was found. The results showed that the louvered conical IRS device outperforms the other two IRS devices significantly when the geometric ratio exceeds a value of 1.4. The mass entrainment of the ambient air was maximum when four louvered funnels at optimum overlap were used. Increasing or decreasing the number of funnels from this value lowers the air entrainment. In the analysis, it was also found that the nozzle protrusion adversely affects the air entrainment and hence for getting the highest entrainment, the nozzle was flush with the lower opening of the bottom most funnel. The funnel overlap also acts as an important parameter as far as the rate of air entrainment is concerned. The air entrainment through the IRS device was found to be maximum when the non-dimensional funnel overlap height ( H o v e r l a p / D n z ) was kept at 8. The mass entrainment rate was found to increase linearly with the nozzle exit Reynolds number in the range of parameters for which the study was undertaken.