A Comparative Analysis of the Air Entrainment through Different Infrared Suppression (IRS) Devices: A Numerical Investigation

Present investigation compares different infrared suppression (IRS) devices which are used in naval warships to cool the hot exhaust gases coming out of the gas turbine plant. These IRS devices work passively by mixing the hot exhaust gases coming out of the gas turbine plant with the cold ambient air which is entrained inside these devices on account of pressure difference. The IRS devices considered here are single-cylinder, multi-cylinder and multi-conical IRS device. The analysis of these IRS devices is based on data related to real scale gas turbine installations, which is typically seen in warships like LM 2500 gas turbine from GE. A numerical analysis of these IRS devices has been undertaken by solving the conservation equations of mass, momentum and energy in 3-D using the k-epsilon turbulence model. The comparison is made on the basis of equal volume. The maximum air entrainment is observed when four nozzles are used at the exit of each IRS device. The maximum air entrainment is achieved for the single-cylinder IRS device whereas the multi-cylinder IRS device gives the lowest possible IRS exit temperature. The air entrainment can be maximized by maintaining a higher Reynolds number at the nozzle exit along with a nozzle protruding height of about 0.2m.