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Effect of Slot-guidance and Slot-area on Air Entrainment in a Conical Ejector Diffuser for Infrared Suppression
Author(s): Lakhvinder Singh, Sidh Nath Singh, Sawan Sinha
Keywords: Mass entrainment, Slot openings, Heat signatures, Static pressure recovery, Numerical study.
A numerical study has been carried out on a new design of ejector diffuser (infrared suppression device). New design conceptualizes exploiting the shape of the slot openings. A circular arc is provided to guide the entrained fluid at the slot openings. Performance of guided-slot ejector diffuser (GED) has been compared with conventional (non-guided-slot) ejector diffuser (NGED) in terms of local and cumulative mass entrainment ratios, temperature distribution and static pressure recovery. Three slot-area variations are studied, namely (i) increasing slot-area ranging 1≤A0≤2.02, (A0 is area of the 1st slot) (ii) constant slot-area A0=1 and (iii) decreasing slot-area ranging 0.49≤ A0≤1. Simulations have been carried out at fixed Reynolds number Re=20000. It is observed that GED has higher cumulative mass entrainment ratio than NGED. GED forms cold annulus region below ejector diffuser wall from 1st slot onwards which results in lower wall temperatures. Higher mass entrainment rate and lower wall temperatures make GED a better infrared suppression device but static pressure recovery is better in NGED compared to GED. Slot-area study reveals that the increasing slot-area for GED and NGED is superior then constant and decreasing slot-area configurations.