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유자원(Jawon Yoo),문근환(Keun Hwan moon),최주호(Joo Ho Choi),김진곤(Jin Kon Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Solid rocket motor (SRM) is used in the defense and aerospace industry, because it has several advantages such as simple structure and high thrust. Since the SRM is one-shot device which is impossible to control once ignited, there is high risk of loss of the entire rocket by the small change of operating conditions or parts defect. One of such causes is the debonding of case-propellant interface which results in failure of the mission. In this study, a method is proposed that can predict reliability against the debonding of SRM propellant which undergoes thermal cycles during the long term storage. In the method, limit state function consisting of load and capacity is first formulated, which are the viscoelastic stress induced by thermal cycle and the bonding strength that degrades over time. Strength degradation is measured under isothermal condition with different temperatures by intermittent test, from which an empirical model is established as a function of temperature and time. Miners rule is applied to predict the strength degradation under arbitrary thermal cycle, and the result is validated by the real degradation data. Debonding stress is calculated by viscoelastic Finite element analysis(FEA) of the case and propellant interface under the thermal cycle. Finally, reliability of SRM is calculated using the concept of instantaneous and progressive reliability.
김계환(Kyehwan Kim),유자원(Jawon Yoo),박종연(Jongyeon Park),한영진(Youngjin Han),문근환(Keunhwan Moon),김진곤(Jinkon Kim),문희장(Heejang Moon) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.5
본 연구는 하이브리드 추진 시스템의 추력제어를 위한 산화제 유량 제어 특성 연구를 수행하였다. 산화제 유량 제어를 위해 볼밸브와 스텝모터를 이용하여 유량 제어 시스템을 구축하였으며, 산화제는 기체 산소(GOX)를 이용하였다. 실험 결과 공급압력에 무관하게 볼밸브의 개방 각도에 따라 산화제 유량이 비교적 선형적으로 증가함을 확인하였으며 각각의 구간 내에서도 일정한 유량이 공급되는 것을 확인하였다. In this study, control of oxidizer mass flow rate and verification of control system were performed for hybrid rocket thrust control application. Oxidizer flow control system consists of ball valve and stepping motor where gaseous oxygen was used for oxidizer at feeding pressure of 10, 20 and 30 bar. According to experimental results, the oxidizer mass flow rate showed a relatively linear increment as ball valve open angle increases regardless of feeding pressure. In addition, the level of the oxidizer flow rate was kept almost constant at each sequence of flow control with ball valve during the 20 seconds of operation.