Moongeun Hong

Stability of a swirled liquid film entrained by a fast gas stream

We study the liquid flow inside a recessed gas-centered swirl coaxial injector, where a swirled liquid flowing against an outer wall is destabilized by a central fast gas stream. We present measurements of the liquid intact length inside the injector, as a function of swirl number and dynamic pressure ratio. We propose a simple model to account for the effect of these parameters. We next study the surface instability inside the injector: its frequency is measured for several swirl angles, and as a function of gas velocity. Results are first confronted to the predictions of an inviscid linear stability analysis including swirl, and second to the predictions of a viscous linear stability analysis where swirl is not included. The viscous analysis captures the experimental frequency.

Turbine Rotor-Pyrostarter Coupled Test for the Verification of Thermo-Structural Suitability of a Turbopump Turbine

ABSTRACT Turbine rotor-pyrostarter coupled test was performed for the verification of thermo-structural suitability of a turbopump turbine. Newly developed solid propellant and design concept were used in pyrostarter development. In case of turbine rotor, rotor config uration modification and post EDM machining process are adopted in rotor manufacturing respective ly for the thermal stress relief and the surface integrity improvement on the blade surfaces. In the tes t, combustion gas of pyrostarter was directly ejected from the nozzles and impinged on the stationar y turbine rotor specimen through the identically shaped flow passage of turbopump. Three kind of thermal load - design to extreme condition - test were performed and no damages were found on the turbine rotor specimens. 초 록 터보펌프 터빈로터의 열구조적 적합성 검증을 위한 터빈로터-파이로시동기 연계시험을 수행하였다. 새로운 추진제를 적용한 파이로시동기와 열응력 경감 설계 및 터빈 동익 표면 건전성 향상을 위한 후가공 공정이 적용된 터빈로터시편이 시험에 사용되었다. 시험은 75톤급 엔진시동을 위한 파이로 시동기의 연소가스를 터보펌프 터빈로터와 동일한 형상의 시편에 분사하는 방식으로 이루어졌다. 터빈에 가해지는 열 부하는 운용 설계점에서 극한 조건까지 세 종류로 구분하여 시험을 진행하였으며 모든 시험에서 터빈로터의 손상은 발견되지 않았다.Key Words: Turbopump(터보펌프), Turbine(터빈), Pyrostarter(파이로시동기), 연계시험(Coupled-test)Received 7 June 2013 / Revised 23 December 2013 / Accepted 2 J anuary 2014

Study for the Development of a Main Oxidizer Shut-off Valve for Liquid Rocket Engines

A main oxidizer shut-off valve (MOV) controls the supply of cryogenic liquid oxygen to the combustion chamber of liquid rocket engines by on/off operation s. The main subjects to be introduced are not only the valve transient response during valve on/off procedures but also the characteristics of pneumatic and seat/poppet parts as core technologies in the dev elopment of the MOV, which is expected to be adopted for the Korea Space Launch Vehicle II. It is shown that the analytical prediction of the transient valve travel is in good agreement with experimental results. Friction and elastic forces on the valve moving part are quantitatively evaluated by structural analysis.