Comparison between a Conventional and a New IRS Device in Terms of Air Entrainment: An Experimental and Numerical Analysis

• Published in: Journal of ship research Vol. 64; no. 4; pp. 357 - 371
• Main Authors: Ganguly, Viplove Ranjan, Dash, Sukanta K.
• Format: Journal Article
• Language: English
• Published: SNAME 01.12.2020; The Society of Naval Architects and Marine Engineers
• ISSN: 0022-4502; 1542-0604
• DOI: 10.5957/JOSR.06190034

An experimental study was conducted on a laboratory-scale new infrared suppression (IRS) device to assess the mass entrainment of ambient air into it under various operating conditions. A numerical analysis was also undertaken to assess the mass entrainment rate against pertinent input parameters independently. The numerical results were validated against the experimental data to ensure the reliability of the numerical analysis of the new IRS device at real scales. The numerical method solves the three-dimensional, incompressible Navier-Stokes equations; the mass continuity equation; and the two-equation-based eddy viscosity model for the turbulent k-epsilon equations in the flow field. Numerical assessment of the air entrainment was performed for the conventional and the newly proposed IRS devices. A number of experiments on the new IRS device were carried out under various operating conditions. From the numerical study, it was observed that the conventional IRS device performs better than the new IRS device up to a geometric ratio of 1.4 (which is the ratio of diameters of the successive funnels used in an IRS device). Beyond the geometric ratio of 1.4, the newly proposed IRS device outperforms the conventional one significantly. For the new IRS device, the maximum mass entrainment was found to occur when four funnels were used and the nozzle was kept in flush condition with the lower opening of the bottom-most funnel. Mass entrainment increases with the nozzle-exit Reynolds number for the range of values considered in the study.