Jin-Sun Kim

Effect of Tip Clearance on the Cavitation Performance of a Turbopump Inducer

The characteristics of steady and unsteady cavitation in a two-bladed inducer for a turbopump are investigated. A helical inducer with inlet tip blade angle of 7.8 deg and a tip solidity of 2.7 is tested using water as a working fluid. To determine the effect of tip clearance on the inducer performance, a series of experiments is conducted at three different tip clearances. As the tip clearance increases, the inducer head decreases and the critical cavitation number increases. Unsteady pressure measurements at the inducer inlet indicate the existence of attached cavitation and cavitation surge, but no rotating cavitation in the test inducer. Attached cavitation and cavitation surge appear for all three cases of tip clearance. The cell number and propagation speed of the attached cavitation are determined through a cross-correlation analysis. In the case of attached cavitation, one cell rotates at the same speed as that of the inducer. In addition, the surge frequency decreases with a decrease in the cavitation number, and the ratio of surge frequency to inducer rotational frequency is found to range from 0.07 to 0.20.

Study on inducer and impeller of a centrifugal pump for a rocket engine turbopump

A hydraulic performance test is conducted for a fuel pump of a liquid rocket engine turbopump. The pump driven by an electric motor is tested in a water environment. Experimental results indicate that the inducer has a negligible effect on the head and efficiency of the pump but a significant effect on the cavitation performance. Additionally, an autonomous inducer test is carried out to investigate the effect of the inducer on the pump performance in more detail, and it is found out that the pump reaches a critical cavitation point when the inducer head is dropped by 55%. A reduction of required net positive suction head of the centrifugal pump by attachment of an inducer is also calculated considering the flow interference between the inducer and the centrifugal impeller, and it is found that the calculation shows a reasonable agreement with the test.

Effect of Inducer on Hydraulic Performance of a Turbopump

A hydraulic performance test is conducted for a fuel pump of a liquid rocket engine turbopump. The pump driven by an electric motor is tested in a water environment. Experimental results indicate that the inducer has a negligible effect on the head and efficiency of the pump but a significant effect on the cavitation performance. Additionally, an autonomous inducer test is carried out to investigate the effect of the inducer on the pump performance in more detail, and it is found out that the pump reaches a critical cavitation point when the inducer head is dropped by 55%. I. Introduction hereas the KSR-III rocket launched in 2002 employed a pressure-fed liquid rocket engine, current research and development efforts at the Korea Aerospace Research Institute (KARI) are direct to developing a turbopump demonstrator for application to a gas generator cycle liquid (LOX and kerosene) rocket engine with 30-ton thrust level. 1 An oxidizer pump, a fuel pump and a turbine are assembled in series on an axis constituting a turbopump. Each pump has a single stage centrifugal impeller with an inducer and the turbine is of a single stage impulse type. The LOX pump has an axial inlet while fuel pump has a radial inlet. This paper presents the test results for the fuel pump of which design requirements are shown in Table 1. Normally for each pump of a turbopump, an inducer is installed upstream of a main centrifugal impeller to improve the cavitation performance of the pump. Inducer design is focused on obtaining sufficient cavitation margin rather than high efficiency. As a consequence, an inducer has a low flow coefficient, a small inlet angle, a sharp leading edge, and so on. In this study, conventional hydraulic and cavitation performance tests are performed for a pump, and then a pump test without the inducer is performed to investigate the inducer effect. Moreover, an autonomous inducer test is carried out to validate the performance of the inducer itself.

Hydrodynamic Performance Test of a Turbopump Assembly

Abstract Hydrodynamic performance test of a turbopump for a liquid rocket engine is carried out. The turbopump is composed of an oxidizer pump, a fuel pump and a turbine, and the two pumps are driven by the turbine. In the test, water is used for the pumps as working media and air is used for the turbine. Performance parameters of pumps and a turbine are drawn, and a power balance between the pumps and the turbine are calculated. The calculation shows a good power balance, which implies that the pump component tests, the turbine component test and the assembly test are reliably performed. At the starting period of the test, pressure rise-flow rate curve of a pump gradually approaches the ideal curve which could be obtained by very slow starting. † 책임저자, 회원, 한국항공우주연구원 터보펌프팀 E-mail : sshong@kari.re.kr TEL : (042)860-2739 FAX : (042)860-2679 * 한국항공우주연구원 터보펌프팀 기호설명  : 터빈 단열 속도   : 유체의 정압 비열 FP : 연료펌프  : 비열비  : 터빈의 질량 유량 OP : 산화제펌프   : 터빈 입구 전압력   : 터빈 출구 압력

Cryogenic Performance Test of LOX Turbopump in Liquid Nitrogen

초록: 액체질소를작동유체로한극저온시험설비를이용하여산화제펌프의성능시험을수행하였다. 설계회전수의30~55%영역에서시험을수행하였으며, 그결과를작동유체로물을이용한상온수류시험의결과와비교/분석하였다. 수력성능에있어서는회전수에대한상사성을만족시킴으로써, 설계회전수인20000rpm에서의성능예측을가능하게했다. 펌프의극저온흡입성능에서는설계유량에서극저온임계캐비테이션수가0.012으로나타났으며, 상온수류시험의경우는0.024를보이면서, 모든시험회전수와시험유량영역에서수류시험의경우보다향상된결과를보였다. 이러한향상된극저온환경에서의흡입성능은극저온유체에서펌프의열역학적인효과로부터기인하는것으로판단된다.Abstract: Performance tests of a liquid-oxygen pump were carried out using liquid nitrogen (LN2) as a working fluidin a cryogenic turbopump test facility in Korea Aerospace Research Institute (KARI). The tests were performed at30-55% of the design rotational speed, and the results were compared with those from a water test. The experimentalresults confirmed the similarity of the hydraulic performance, which allows the prediction of the pump performance ata design rotational speed of 20,000 rpm. The overall cavitation performance of the pump in the cryogenic environmentwas better than that in the water environment for all ranges of flow rates and rotational speeds. Critical cavitationnumber at the design flow rate was determined as 0.012 from the cryogenic test, and as 0.024 from the water test.The improved cavitation performance is due to the thermodynamic effect in cryogenic fluids.

Transient Thermal and Structural Analysis of the Liquid Rocket Turbopump Turbine

A turbopump unit is a key component of the liquid rocket engine assembly. Generally operated by an impulse-type turbine with supersonic hot gas for a gas generator cycle engine, it pressurizes liquid oxygen and fuel to attain high specific impulse. The turbine is exposed to hot gas while rotating at a high speed and experiences severe thermal and mechanical loads during the operation. Its structural integrity must be assured through thermal and structural analyses of the turbine. To investigate non-steady heat transfer characteristics from the hot gas to the turbine blade, the heat transfer of supersonic hot gas flow to the complicated turbine blade geometry is solved through a three-dimensional CFD analysis. The distribution of gas temperature, pressure and velocity on the blade surface are obtained by the CFD analysis with appropriate convection heat transfer coefficients to be used for the structural analysis of the turbine rotor. The thermal stress due to material expansion and mechanical stress due to centrifugal loads are considered in the analysis. The three-dimensional transient stress distributions of the turbine blades, shroud, and disk are obtained by a finite element analysis. Finally, the overall results are examined to evaluate the strength safety of the turbine.Copyright

Cavitation Instabilities During the Development Testing of a Liquid Oxygen Pump

Inducers are critical to the minimization of the degradation of liquid oxygen pumps and the maximization of the thrust-to-weight ratio of liquid rocket engines, but create cavitation instabilities that have adverse effects on their reliabilities. To examine the cavitation instabilities that arose during the development testing of a liquid oxygen pump that uses water and liquid oxygen as its working media, accelerometers were employed instead of pressure transducers, which are complicated to install. The supersynchronous rotating cavitation and asymmetric cavitation of the pump were characterized by analyzing the signals from the accelerometers, and these results were found to be in good agreement with those of previous studies. Supersynchronous rotating cavitation was found to occur in the tests of both propellants, whereas asymmetric cavitation was found to be dominant in the liquid oxygen test.

Performance Test of a 75-tonf Rocket Engine Turbopump

ABSTRACT Performance tests of a 75-tonf liquid rocket engine turbopump were conducted. The performance of sub-components - two pumps and a turbine - and their power matching were measured and examined firstly near the design speed under the LN2 and kerosene enviro nment. In the real propellant - LOX and kerosene - environment tests, design and off-design performance of turbopump were fully verified in regime of the rocket engine operation. During the off-design performance tests, turbopump running time was set longer than the engine operating time to verify the pump operability and set the pump inlet pressure close to design NPSHr to investigate pump suctio n capability in parallel. It has been found that developed-turbopump satisfied all of the engine required performances.초 록 75톤급 액체로켓엔진용 터보펌프 개발 시제에 대한 조립체 성능시험이 터보펌프 실매질 시험설비에서 수행되었다. LN2와 케로신을 적용한 첫 시험에서는 터보펌프 구성품들의 조립체 상태에서의 수력/공력 성능 및 출력 매칭 점검이 설계회전수 근방에서 이루어 졌으며 LOX와 케로신을 적용한 실매질 시험에서는 터보펌프의 설계성능 및 엔진운용영역 탈설계 성능 검증이 이루어졌다. 탈설계시험의 경우, 내구성 검증을 위해 엔진의 운용시간을 초과하여 터보펌프가 운용되었으며 펌프입구압력을 설계 요구유효흡입양정(NPSHr)에 가깝게 설정하여 흡입성능 검증을 병행하였다. 개발된 75톤급 액체로켓용 터보펌프는 성능, 운용시간의 엔진 요구규격을 만족시키는 것으로 확인되었다.Key Words:Liquid Rocket Engine(액체로켓엔진), Turbopump(터보펌프), Performance Test(성능시험), Kerosene(케로신), LOX(액체산소)Received 2 December 2015 / Revised 29 February 2016 / Accepted 7 March 2016

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

Study on the Forward-sweep Inducer for Turbopumps

Computational and experimental studies on the forward-sweep inducer for the rocket-engine turbopump are presented in comparison with the conventional backward-sweep inducer. Computational results show that back flows at the inlet decrease in the case of forward-sweep inducers compared to the back-ward inducer. Moreover, the low pressure region at the back flow is decreased, which is presumed to improve the suction performance of the inducers. Experimental results show that the suction performance of the forward-sweep inducer is almost the same as that of the backward-sweep inducer although it has smaller inlet tip diameter and shorter length. The efficiency of the forward-type inducer is found better than that of the backward-sweep inducer due to the small size of back flows.