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Bae, Jinhyun,Yoon, Jisu,Joo, Seongpil,Kim, Jeoungjin,Jeong, Chanyeong,Sohn, Chae Hoon,Borovik, Igor N.,Yoon, Youngbin The Korean Society for Aeronautical and Space Scie 2017 International Journal of Aeronautical and Space Sc Vol.18 No.4
In this study, the reflection coefficient (RC) and the flame transfer function (FTF) were measured by applying acoustic excitation to a duct-type model combustor and were used to predict the frequency of the combustion instability (CI). The RC is a value that varies with the excitation frequency and the geometry of the combustor as well as other factors. Therefore, in this study, an experimentally measured RC was used to improve the accuracy of prediction in the cases of 25% and 75% hydrogen in a mixture of hydrogen and methane as a fuel. When the measured RCs were used, an unstable condition was correctly predicted, which had not been predicted when the RCs had been assumed to be a certain value. The reason why the CI occurred at a specific frequency was also examined by comparing the peak of the FTF with the resonance frequency, which was calculated using Helmholtz's resonator analysis and a resonance frequency equation. As the CI occurred owing to the interaction between the perturbation in the rate of heat release and that in the pressure, the CI was frequent when the peak of the FTF was close to the resonance frequency such that constructive interference could occur.
Dynamic Characteristics of a Coaxial Jet–Swirl Injector with External Excitation
Jinhyun Bae,Taesung Kim,Seokgyu Jeong,Chanyeong Jeong,구자예,Youngbin Yoon 한국항공우주학회 2018 International Journal of Aeronautical and Space Sc Vol.19 No.4
Combustion instability is caused by the coupling of acoustics, hydrodynamics, and flame dynamics. Therefore, understanding the dynamic characteristics of the injector ejecting fuel and oxidizer into the combustion chamber is very important in understanding the combustion instability. This study measures the injector transfer function (ITF) to investigate the dynamics of a gas–gas coaxial jet–swirl injector capable of simulating a full-flow staged combustion cycle. The ITF peaks were generated at the frequency corresponding to the resonant frequency of the tube through which the excited fluid flows. The Kelvin–Helmholtz (K–H) instability was strong when the velocity difference between two flows (ΔV) was large; hence, the ITF was large. The K–H instability weakened and the ITF was small when ΔV ≈ 0, but the Holmboe instability corresponding to the second mode of the K–H instability occurred, such that the perturbation corresponding to twice the excitation frequency became bigger. The results of the dynamic characteristics of the gas–gas coaxial jet–swirl injector in this study will be helpful in understanding the injector dynamics and in solving the combustion instability, which applies to the full-flow staged combustion cycle.
Jinhyun Bae,Hyeontaek Jo,Youngbin Yoon 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11
This study analyzes the effect of changes in input parameters on the prediction results in combustion instability. First, applying the centroid location of the flame shows higher accuracy of instability prediction than assuming that the flame is formed immediately after the injector. Also, the acoustic boundary of the recess inlet does not significantly affect the overall prediction result, but the acoustic boundary at the nozzle throat has such an effect that the instability frequencies are predicted completely differently. The gain of the flame transfer function is closely related to the strength of combustion instability, but less related to the overall tendency of combustion instability occurrence. However, a change in the flame transfer function phase changes whether combustion instability occurs at a specific frequency. Therefore, it is confirmed that the phase is a more important parameter than the gain of the flame transfer function in predicting combustion instability.
저비용 우주 발사체 개발 동향 및 이를 위한 차세대 연료에 대한 고찰
배진현(Jinhyun Bae),구자예(Jaye Koo),윤영빈(Youngbin Yoon) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.10
인공위성의 경량화 및 소형화로 인하여 대형발사체보다는 발사 비용이 저렴한 저비용 발사체에 대한 관심이 증가되고 있다. 저비용 발사체의 비용 절감 중 가장 대표적인 방식이 발사체의 재사용이다. 저비용 발사체를 개발하고 있는 대부분의 기업들 역시 발사체 재사용 방식을 채택하고 있다. 이러한 재사용 목적과 더불어 친환경 우주 발사체에 대한 요구가 증가되면서 저비용 발사체에 사용되는 연료의 선택 역시 매우 중요해졌다. 친환경적이면서 발사체의 재사용이 가능하게 하는 연료 중 에너지 밀도 등 다른 요인을 고려했을 때 가장 적합한 것이 메탄이며, 메탄에 수소를 첨가하여 에너지 밀도를 높게 만든 HCNG(hydrogen-enriched compressed natural gas) 역시 적합하다고 판단되었다. 본 연구는 한국형 발사체 개발 이후 국내 우주 개발 방향 설정의 참고자료로써 전 세계 저비용 발사체 동향 및 로켓 연료의 특성에 대해 고찰하였다. Due to the weight reduction and miniaturization of satellites, there is a growing interest in low-cost launch vehicles, which are cheaper to launch than larger launch vehicles. One of the most cost-effective ways to reduce the cost of launch vehicles is the reuse of vehicles. Most companies that are developing low cost launch vehicles are also adopting a vehicles reuse approach. Along with this reuse purpose, the demand for environmentally friendly space launch vehicles has increased, so the choice of fuel used for low cost launch vehicles has also become very important. Methane and hydrogen-enriched compressed natural gas (HCNG), which makes more energy-efficient by adding hydrogen to methane, are considered to be the most suitable when considering other factors such as energy density among the fuels that are eco-friendly and capable of reusing the launch vehicles. This study investigated the trends of low-cost launch vehicle and rocket fuel in the world as a reference for setting up domestic space development after the development of Korea Space Launch Vehicle-II.