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발사체의 고도보정용 3D 프린팅 확장-굴절 노즐에 관한 실험적 연구
이기환,박상현,구자예,허환일 대한기계학회 2019 大韓機械學會論文集B Vol.43 No.12
An experimental study of an expansion-deflection (E-D) nozzle for a launch vehicle is conducted. The E-D nozzle is designed by selecting the pintle inflection angle as the main variable and is manufactured from a metal 3D printer using SLM process techniques. Visualization experiments and surface roughness measurements are performed to compare the characteristics of the E-D nozzle before and after the post-process. As a result, several oblique shockwaves are confirmed to have occurred due to the high surface roughness before the post-processing, which decreased after the post-processing. In addition, a thrust measurement experiment is performed to analyze the performance of the E-D nozzle, showing that the thrust of the E-D nozzle tends to increase as the pintle inflection angle increases. 발사체 고도보정용 확장-굴절 노즐의 실험 연구를 수행하였다. 확장-굴절 노즐은 핀틀 변곡 각도를 주요 변수로 선정하여 설계하였고, SLM 공정 기법을 사용하는 금속 3D 프린터로 제작하였다. 3D 프린터로 제작한 확장-굴절 노즐의 후처리 전/후에 나타나는 특성을 비교하기 위해 표면 조도 측정과 가시화 실험을 수행하였다. 측정 및 실험 결과, 후처리 전의 높은 표면 조도로 인해 다수의 경사충격파가 나타났고, 후처리 후에는 경사충격파가 감소한 것을 확인하였다. 또한 확장-굴절 노즐의 성능을 분석하기 위해 추력 측정 실험을 수행하였으며, 핀틀 변곡 각도가 높을수록 확장-굴절 노즐의 추력이 크게 나타나는 경향을 보였다.
듀얼 벨 노즐과 E-D 노즐을 결합한 한국형발사체의 비추력 증가
문태석(Taeseok Moon),허환일(Hwanil Huh) 한국추진공학회 2018 한국추진공학회지 Vol.22 No.1
A basic numerical analysis was performed to confirm the possibility of combining a dual bell nozzle and an Expansion-Deflection(E-D) nozzle. The dual bell nozzle was designed based on the first-stage nozzle of the Korean Space Launch Vehicle that is being developed, and the E-D nozzle concept was applied to the dual bell nozzle. The inlet condition was analyzed by applying eight types of frozen flow analysis, and k-ω SST was selected as the turbulence model. The number of optimal grids was obtained as 240,000 through the grid sensitivity analysis. As a result, it was confirmed that the transition altitude increased owing to over-expansion when the E-D nozzle concept was applied to the dual bell nozzle, and the specific impulse gain was obtained at high altitudes compared with the KSLV-II first-stage engine.