Electromagnetic Pulse (EMP) Shielding Effectiveness of Waveguide-Below- Cutoff (WBC) Arrays Installed in Generator Exhaust Chimney and its Effects on Gas Velocity

Abstract Characteristics of exhaust from chimney of electricity generator are analyzed based on CFD whenWaveguide-Below-Cutoff (WBC) array is installed in order to achieve the certain level ofelectromagnetic pulse (EMP) shielding. The main purpose is prediction of average and maximumvelocity of exhaust. The results reveal that: 1) When the specification of waveguide is given as 80-diameter, 400-length, and the gap of 20 mm, the shielding effectiveness (SE) is 140dB. The averageand maximum velocity of exhaust in the chimney with WBC Array can be represented as exponentialfunctions. 2) As the number of WBC increases, the velocity in the chimney dwindles. 3) Under thesituation that WBC with 80 mm diameter is located at intervals of 20 mm, the average velocity canbe approximated by 25.5344 × e (−0.0098× N WBC ) with input velocity of 15 m/s. In addition, the determinationcoefficient is 0.915, which is sufficiently high. Key words: EMP(전자기파), CFD(전산유체역학 ), Waveguide, WBC Array(도파관 배열), ShieldingEffectiveness(차폐효과),Emergency Generator(비상발전기)