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Effects of Angles of Attack and Throttling Conditions on Supersonic Inlet Buzz
NamKoung, Hyuck-Joon,Hong, Woo-Ram,Kim, Jung-Min,Yi, Jun-Sok,Kim, Chong-Am The Korean Society for Aeronautical and Space Scie 2012 International Journal of Aeronautical and Space Sc Vol.13 No.3
A series of numerical simulations are carried out to analyze a supersonic inlet buzz, which is an unsteady pressure oscillation phenomenon around a supersonic inlet. A simple but efficient geometry, experimentally adopted by Nagashima, is chosen for the analysis of unsteady flow physics. Among the two sets of simulations considered in this study, the effects of various throttling conditions are firstly examined. It is seen that the major physical characteristic of the inlet buzz can be obtained by inviscid computations only and the computed flow patterns inside and around the inlet are qualitatively consistent with the experimental observations. The dominant frequency of the inlet buzz increases as throttle area decreases, and the computed frequency is approximately 60Hz or 15% lower than the experimental data, but interestingly, this gap is constant for all the test cases and shock structures are similar. Secondly, inviscid calculations are performed to examine the effect regarding angle of attack. It is found that patterns of pressure oscillation histories and distortion due to asymmetric (or three-dimensional) shock structures are substantially affected by angle of attack. The dominant frequency of the inlet buzz, however, does not change noticeably even in regards to a wide range of angle of attacks.
연료전지 수소재순환 이젝터 시스템에 관한 수치해석적 연구
남궁혁준(NamKoung, Hyuck-Joon),문종훈(Moon, Jong-Hoon),장석영(Jang, Seock-Young),홍창욱(Hong, Chang-Oug),이경훈(Lee, Kyoung-Hoon) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.11
Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some sonic and subsonic ejectors with the function of changing nozzle position were manufactured precisely and tested for the comparison with the calculation results.
Study on the Modified Crocco"s Pseudo-Shock Model for Supersonic Propulsion Engine
Hyuck-Joon Namkoung(남궁혁준) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.5
A pseudo-shock model is proposed, the model makes possible to estimate the distribution of parameters during the transition of a supersonic flow to a subsonic one in the structure of a mathematical model of a supersonic propulsion system with deceleration zone. A numerical simulation of the gas-dynamic parameters in the channel of the pre-chamber diffuser (isolator) of a given geometry was performed. The numerical solution is obtained using the principle of minimum entropy production. Verification of the proposed model on the data obtained in the course of experimental tests of the combustor of a dual-mode ramjet (DMR) engine has been performed. The model is intended for parametric studies as part of mathematical models of DMR engine.
남궁혁준(HyuckJoon Namkoung),심창열(ChangYeul Shim),김선용(SunYong Kim),이민수(MinSoo Lee),박주현(JooHyon Park),김동환(DongHwan Kim) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5
초음속에서 극초음속 영역까지 광범위한 비행영역에서 작동 가능한 추진시스템으로 램제트와 스크램제트의 장점을 포함하는 복합사이클을 적용한 이중램제트에 대한 연구가 많은 선진국에 의해 수행되고 있다. 여기서 이중모드 램제트는 하나의 연소기 즉, 동일한 유동 경로상에서 아음속과 초음속 연소가 이루어져 램제트와 스크램제트 모드로 각각 작동되는 엔진이다. 본 연구에서는 이중모드 스크램제트 엔진의 비행마하수 3.5 ~ 6조건으로 설계된 지상시험모델에 대한 연소시험을 수행하였다. 특히 고도 27.6km 및 Mach 6조건에서의 연소시험 결과를 통해 이중모드램제트의 스크램제트 연소 현상을 확인하고 적용된 설계 방안 등에 대한 검증을 수행하였다. Recently many studies have been made for the development of propulsion system with wide range flight from supersonic to hypersonic. Dual Mode scramjet engine as a hybrid cycle with advantage of ramjet and scramjet has one combustor. It works under the ramjet mode (subsonic combustion) and scramjet mode (supersonic combustion) respectively. In this study, Experimental results of hot firing tests of dual scramjet engine designed on the condition of Mach 3.5~6 as a flight Mach number are discussed. The tests were carried out on a ground test bench under free stream condition of Mach 6 at 27.6km altitude. In the tests, the adopted design and technological solutions were verified and efficient operation of the dual mode ramjet engine with Kerosene combustion during 5 seconds was demonstrated.
Effects of Angles of Attack and Throttling Conditions on Supersonic Inlet Buzz
Hyuck-Joon Namkoung,Wooram Hong,Jung-Min Kim,JunSok Yi,Chongam Kim 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.3
A series of numerical simulations are carried out to analyze a supersonic inlet buzz, which is an unsteady pressure oscillation phenomenon around a supersonic inlet. A simple but efficient geometry, experimentally adopted by Nagashima, is chosen for the analysis of unsteady flow physics. Among the two sets of simulations considered in this study, the effects of various throttling conditions are firstly examined. It is seen that the major physical characteristic of the inlet buzz can be obtained by inviscid computations only and the computed flow patterns inside and around the inlet are qualitatively consistent with the experimental observations. The dominant frequency of the inlet buzz increases as throttle area decreases, and the computed frequency is approximately 60Hz or 15% lower than the experimental data, but interestingly, this gap is constant for all the test cases and shock structures are similar. Secondly, inviscid calculations are performed to examine the effect regarding angle of attack. It is found that patterns of pressure oscillation histories and distortion due to asymmetric (or three-dimensional) shock structures are substantially affected by angle of attack. The dominant frequency of the inlet buzz, however, does not change noticeably even in regards to a wide range of angle of attacks.