Soo Yong Lee

Experimental Study on Spray Characteristics of Gas-Centered Swirl Coaxial Injectors

Gas-centered swirl coaxial injectors have become an important subject of study for staged combustion rocket engines with hydrocarbon fuels. While these injectors are employed successfully in rocket engines, it is very rare to find the related research results as applicable to design data. An experimental study on spray characteristics of gas-centered swirl coaxial injectors has been performed. The effects of momentum flux ratio and recess length on the spray characteristics have been investigated by cold flow tests with a photographic technique. The liquid intact length L, which profoundly affects the global spray characteristics, decreases as the momentum flux ratio M increases. The critical momentum flux ratio Mc is introduced to identify the flow patterns as internal or external mixing in the injectors. Concerning the effect of the recess length lR, it is shown that the spray cone angle and the drop size decrease as lR increases.

Design of Cooling Channels of Preburners for Small Liquid Rocket Engines with Computational Flow and Heat Transfer Analysis

A series of computational analyses was performed to predict the cooling process by the cooling channel of preburners used for kerosene-liquid oxygen staged combustion cycle rocket engines. As an oxygen-rich combustion occurs in the kerosene fueled preburner, it is of great importance to control the wall temperature so that it does not exceed the critical temperature. However, since the heat transfer is proportional to the speed of fluid running inside the channel, the high heat transfer leads to a trade-off of pressure loss. For this reason, it is necessary to establish a certain criteria between the pressure loss and the heat transfer or the wall surface temperature. The design factors of the cooling channel were determined by the computational research, and a test model was manufactured. The test model was used for the hot fire tests to prove the function of the cooling mechanism, among other purposes.

Development of Ultra-Lean-Burn Preburners for Small Liquid Engines

Korea Aerospace Research Institute (KARI) is developing gas generator cycle kerosene engines and also researching technologies of staged combustion cycle LREs for the next generation engine development. As a first step to study the staged combustion cycle, an oxygen rich combustion preburner was developed. The preburner is characterized with ultra-lean burn and high combustion pressure of O/F 60 and 200 bar, respectively. The exhaust gas of the preburner is so similar to high temperature pure oxygen gas that it may burn any metal contacted if the temperature is not strictly controlled. Hot fire tests showed that the combustion pressure was stable and the exhaust temperature satisfied the requirements of the average value and the spatial dispersion. This article will introduce the preburner and show the results of the hot fire tests

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

A Study on the Temperature Distribution at the Exit of Oxygen Rich Preburners

A preburner is one of the key components for a staged combustion cycle engine fueled by kerosene and Lox. Since it has oxygen rich combustion inside, temperature control is very crucial. The temperature of the exhaust gas should be low enough not to burn turbine blade and yet high to keep the efficiency high. In addition temporal and spatial deviations also managed strictly. Conventionally, the required average and maximum temperature are determined by engine system and the preburner should be developed to meet the criteria. Currently being developed preburner has 50K spatial temperature deviation requirement. It was estimated by numerical simulations and proven by tests. The numerical analysis were done with both supercritical condition and normal conditions. The tests results showed that the temperature deviations were less than expected, and the results from the test and simulations were well agreed when the supercritical conditions were considered. Above all, since the gas temperature created by the preburner is very stable with minimum deviation, the preburner developed can be used to drive a turbine and for gas-liquid combustion chambers.

Numerical Analysis on Cooling Characteristics of Oxidizer-Rich Preburner

․ Seong-up Ha** ․ Soo Yong Lee**ABSTRACT The numerical analysis for the verification of preburners co oling characteristics applying to kerosene-LOx rocket engine has been fulfilled. The distribution of combustion gas properties in primary combustion zone was calculated by the mixture ratio bas ed on head injector arrangement, the properties of oxygen flowing in wall channels as coolant were applied under real-gas conditions, and multi-phase mixing model was employed to calculate the mixing p rocess of primary combustion zone with liquid oxygen which was used for wall cooling. The results of numerical analysis were compared with the experimental results, hence thermo-physical properties in cooling channels and a combustor could be quantitatively identified.초 록 케로신-액체산소 로켓 엔진에 적용되는 산화제 과잉 예연소기의 냉각 성능 확인을 위한 수치 해석을 수행하였다. 예연소기 1차 연소구역을 상사하기 위하여 분사기 배열에 따른 혼합비를 바탕으로 연소가스 물성치를 계산하였고, 냉각제로서 채널을 흐르는 산소의 물성치는 실제기체 조건에 대하여 적용하였으며, 1차 연소구역과 냉각제로 쓰인 액체산소의 혼합과정은 다상혼합모델을 적용하였다. 수치 해석으로 계산된 결과를 연소시험과 비교하였으며, 이를 통하여 재생냉각 채널과 연소실에서의 물성 등을 정량적으로 파악할 수 있었다.Key Words: Rocket Engine(로켓엔진), Kerosene(케로신), LOx(액체산소), Preburner(예연소기), Gas Generator(가스 발생기), Oxidizer-rich(산화제 과잉), Cooling(냉각), Mixture Model(혼합 모델)

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.

A Numerical Study on Combustion Characteristics of Coaxial-Jet Injectors Using Scaling Techniques in a Subscale Chamber

Numerical analyses are conducted with scaling techniques to predict combustion instability in actual fullscale combustion chamber of rocket engines. From the simulation with a subscale chamber, flame patterns are investigated as a function of the recess length and spreading angle of fuel jet is focused on. For stability rating, damping factors have been obtained as a function of hydraulic parameter and the data give us information on relatively stable and unstable zones. From the numerical results, the stable zone can be identified in a quantitative manner.