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함희철(Heecheol Hahm),강윤구(Yoongoo Kang),서상규(Sangkyu Seo) 한국추진공학회 2017 한국추진공학회지 Vol.21 No.4
The ablation characteristics of graphite nozzle throat insert was analyzed for the use in solid rocket propulsion system. The propulsion system was composed of three types of conventional nozzles, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants were used in ten kinds of propulsion system that had different shapes with each other. Total forty eight tests were performed. From the results of the analysis, it was found that the ablation rate was increased for the higher average chamber pressure and the higher oxidizer mole fraction. A useful correlation for nozzle throat ablation rate was developed in terms of the chamber pressure, oxidizer mole fraction, and throat size. The calculated ablation rates from the correlation showed agreement within ± 0.10 mm/s with the experimentally determined values.
압력과 산화몰분율이 그라파이트 목삽입재의 삭마율에 미치는 영향
함희철(Heecheol Hahm),강윤구(Yoongoo Kang) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.1
The ablation characteristics of graphite nozzle throat insert is analyzed for the use in solid rocket propulsion system. The propulsion system is composed of three types of conventional nozzles, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants are used in the thirteen kinds of propulsion system that has different shapes of each other. Total thirty seven tests are performed. From the results of the analysis, it is found that the ablation rate is higher for the higher average chamber pressure and the higher concentration of oxidizing species in combustion gas.
함희철(Heecheol Hahm),강윤구(Yoongoo Kang) 한국추진공학회 2012 한국추진공학회지 Vol.16 No.2
The goal of heat transfer studies is the accurate prediction of temperature and heat flux distribution on material boundaries. To this purpose, general-purpose computational fluid dynamics(CFD) code is used : FLUENT. Mass fluxes and pressure ratio are calculated for two types of nozzle. The comparative studies reveal that the computational results are in agreement with the experimental data. Also, heat transfer coefficients from FLUENT for one type of nozzle are very similar and agree well with the experimental data in the diverging part of the nozzle, but the calculated results are large in the converging part. The heat transfer coefficients from Bartz equation are over-predicted. We can consider various reasons for these differences, i.e., laminarization by the highly accelerated flow in the nozzle, turbulent flow model and grid generation.
압력과 산화몰분율이 그라파이트 목삽입재의 삭마율에 미치는 영향
함희철(Heecheol Hahm),강윤구(Yoongoo Kang) 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.5
고체 로켓 추진기관의 노즐목 삽입재에 적용하는 그라파이트의 삭마율 특성을 분석하였다. 지상연소 시험은 3종류의 일반적인 노즐형태를 갖는 추진기관을 사용하여 수행하였다. 즉, De-Laval 형태, 토출관 형태, 내삽 형태이다. 13종류의 서로 다른 형상의 추진기관에 다양한 추진제를 적용하였고, 노즐목 위치에 흑연을 적용하여 총 31회의 연소시험을 수행하였다. 분석결과 그라파이트의 삭마율은 연소실 압력이 상승함에 따라, 산화몰분율이 증가함에 따라 증가함을 알 수 있다. A characteristics about ablation rate of graphite used as the nozzle throat insert of solid rocket propulsion system is analysed. The propulsion system is composed of three types of conventional nozzle, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants are used in the thirteen kinds of propulsion system that has different shape of each other. Total thirty one tests are performed. From the results of the analysis, we know that the ablation rate is higher for the higher chamber pressure and also higher for the higher concentration of oxidizing species in combustion gas.