Hyun Duck Kwak

Rotordynamic Analysis of a Turbopump with the Casing Structural Flexibility

A critical speed analysis is performed for a 30-ton thrust demonstrator turbopump considering the casing structural flexibility. A full three-dimensional finite-element method including rotor and casing is used to predict rotordynamic behavior. The rotor-alone model and the rotor-casing-coupled model with fixed-fixed and free-free boundary conditions are calculated to investigate the effects of the casing structural flexibility. The stiffness of ball bearings is applied as unloaded and loaded values to consider rotor operating conditions in a vacuum and real engine, respectively. From the results of the numerical analyses, it is found that the effect of the casing structural flexibility reduces the critical speeds of the turbopump. Especially, the loaded rotor condition with higher bearing stiffness is affected dramatically more than the unloaded rotor condition with lower bearing stiffness.

Water Tests of Fuel Pump for 75-ton Class Liquid Rocket Engine

A series of water tests of a fuel pump for liquid rocket engines are performed at a room temperature. According to the test results, the head coefficient of the pump follows the conventional similarity rule - unlike this, the pump shows better efficiency with higher rotational speed. Also, it is found that the pressure at the rear bearing outlet is higher than expected because the inlet of bypass pipe line is narrow. Furthermore, the cavitation performance of the fuel pump is found to be sufficient for the engine operation and is better at the lower flow ratio and higher rotational speed.

Performance Test of a 7 tonf Liquid Rocket Engine Turbopump

ABSTRACT Performance tests of a turbopump for the developing 7-tonf li quid rocket engine were conducted. The performance of turbopump components and their power matchin g were measured and examined firstly under the LN2 and water environment.. In the real prope llant(LOX and kerosene) environment tests, design and off-design performances of turbopump were ful ly verified. During the off-design tests, turbopump running time was set the same as engine operat ing time and pump inlet pressure were set lower than nominal operating value in order to investigate pump suction capability. It have been verified that subject turbopump satisfies required performance - flow rate, head, suction performance and operational time - in the operating regime of d eveloping liquid rocket engine.초 록 7톤급 액체로켓엔진용 터보펌프 개발 시제에 대한 조립체 성능시험이 수행되었다. LN2와 물이 적용된 상사매질 조립체 시험을 통해 터보펌프 단품 간 출력 매칭 및 조립체 레벨에서의 수력/공력 성능 검증이 선행되었으며 LOX와 케로신의 실제 운용 환경의 실매질 시험에서는 터보펌프의 설계점, 탈설계점 성능 검증시험이 이루어졌다. 탈설계시험은 엔진의 운용시간을 적용하여 이루어졌으며 펌프의 흡입성능 검증을 병행하였다. 개발된 7톤급 액체로켓용 터보펌프는 엔진운용영역에서 유량, 양정, 흡입 성능, 그리고 운용시간의 요구규격을 만족시키는 것으로 확인되었다.Key Words:Liquid Rocket Engine(액체로켓엔진), Turbopump(터보펌프), Performance Test(성능시험), Kerosene(케로신), LOX(액체산소)Received 27 December 2014 / Revised 8 March 2015 / Accepted 13 March 2015

Critical Speed Analysis of a 75 Ton Class Liquid Rocket Engine Turbopump due to Load Characteristics

․ Hyun D. Kwak* ․ Soon-Sam Hong* ․ Jinhan Kim**ABSTRACT Critical speed of high thrust liquid rocket engine turbopump is obtained through a rotordynamic analysis and a unloaded turbopump test is peformed for validation of the numerical model. The first critical speed predicted by the numerical analysis is correlated well with the test result for the bearing unloaded rotor condition only considering mass unbalance load. Using the previous rotordynamic model, critical speed variation is estimated as a function of v aried bearing stiffness due to pump and turbine radial loads with relative angle difference. From the numerical analysis, it is found that the relative angle difference of pump and turbine radial loads greatly affects the critical speed. However, additional axial load reduces the effect derived from the relat ive angle difference of radial loads.초 록 고추력 액체 로켓 엔진용 터보펌프의 무부하 회전 시험을 통하여 얻어진 임계속도를 회전체동역학 해석으로부터 예측된 임계속도와 상호 비교하여 해석 모델의 타당성을 검토하였다. 질량 불평형 하중만을 고려한 베어링 무부하 하중조건에서 해석으로부터 얻어지는 1차 임계속도의 예측치는 시험에서 얻어진 결과와 잘 일치하였다. 상기 회전체동역학 모델을 이용하여 유동해석 및 성능시험 결과를 바탕으로 얻어진 펌프와 터빈의 반경하중으로부터, 반경하중 상대 각도에 따른 베어링 강성 변화를 고려하여 임계속도 변화를 예측하였다. 수치해석 결과 펌프와 터빈의 반경하중 상대 각도는 임계속도에 지대한 영향을 미치고 있는 것으로 나타났다. 반면 추가로 축하중이 부과되는 경우 반경하중의 상대 각도에 대한 영향은 감소하는 것으로 나타났다.Key Words: Liquid Rocket Engine(액체로켓엔진), Turbopump(터보펌프), Rotordynamics(회전체동역학), Bearing(베어링), Critical Speed(임계속도)

Investigation on the rotordynamic characteristics of the turbopump with the casing structural flexibility

A critical speed analysis is performed for a 30 ton thrust demonstrator turbopump considering the casing structural flexibility. A full three-dimensional finite element method including rotor and casing is used to predict rotordynamic behavior. Rotor alone model and rotor-casing coupled model with fixed-fixed and free-free boundary conditions are calculated to investigate the effects of the casing structural flexibility. The stiffness of ball bearings are applied as unloaded and loaded values to consider rotor operating conditions in vacuum and real engine respectively. From the results of the numerical analyses, it is found that the effect of the casing structural flexibility reduces the critical speeds of the turbopump. Especially, the loaded rotor condition with higher bearing stiffness is affected dramatically rather than the unloaded rotor condition with lower bearing stiffness.