• International Journal of Fluid Machinery and Systems
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• 제1권1호
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• pp.64-75
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• 2008

During an experimental investigation on a 3-bladed and a 4-bladed axial inducer, a severe surge instability was observed in a range of cavitation number where the blade passage is choked and the inducer head is decreased from noncavitating value. The surge was stronger for the 4-bladed inducer as compared with a 3-bladed inducer with the same inlet and outlet blade angles. For the 4-bladed inducer, the head decreases suddenly as the cavitation number is decreased. The surge was observed after the sudden drop of head. This head drop was found to be associated with a rapid extension of tip cavity into the blade passage. The cause of surge is attributed to the decrease of the negative slope of the head-flow rate performance curve due to choke. Assuming that the difference between the 3 and 4-bladed inducers is caused by the difference of the blockage effects of the blade, a test was carried out by thickening the blades of the 3-bladed inducer. However, opposite to the expectations, the head drop became smoother and the instability disappeared on the thickened blade inducer. Examination of the pressure distribution on both inducers could not explain the difference. It was pointed out that two-dimensional cavitating flow analyses predict smaller breakdown cavitation number at higher flow rates, if the incidence angle is smaller than half of the blade angle. This causes the positive slope of the performance curve and suggests that the choked surge as observed in the present study might occur in more general cases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.631-636
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• 2001

The internal flow in the rocket pump inducer of LE-7 engine for H-II rocket was predicted at design and off-design flow rates using CFD code, CFX- Tascflow. In this numerical study, the performance curve of inducer coressponding to flow rates variation and the internal flow in the front of blade leading edge show good agreement between the calculations and the measurements. Backflow is appeared at suction side of leadinge edge tip, and this region is extended to upstream as flowrate decrease. Because of backflow, pressure loss coressponding to meridinal coordinate occupy 50% from inlet domain to leading edge. By this phenomena, pressure loss in front of blade leading edge take a great effect to inducer performance.

• 한국유체기계학회 논문집
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• 제15권1호
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• pp.41-45
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• 2012

The effects of inducer tip clearance on the suction performance of a pump for turbopumps are investigated. Experiments for the pump with inducer tip clearances of 1.8% and 1.4% of blade height were performed. The experimental results showed that the suction performance of the pump increased as the tip clearance decreased. It seems that the suction performance of the pump becomes better with smaller tip clearances because the strength of the inducer backflow becomes weak with the decreased tip clearance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.619-624
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• 2001

A performance test facility for turbopump inducer cavitation was developed and the inducer cavitation performance tests were performed. Major components of the performance test facility are driving unit, test section, piping, water tank, and data acquisition and control system. The maximum of testing capability of this facility are as follows: flow rate - 30kg/s; pressure - 13 bar; rotational speed 10,000rpm. This cavitation test facility is characterized by the booster pump installed at the outlet of the pump that extends the flow rate range, and by the pressure control system that makes the line pressure down to vapor pressure. The vacuum pump is used for removing the dissolved air in the water as well as the line pressure. Performance tests were carried out and preliminary data of test model inducer were obtained. The cavitation performance test and cavitation bubble flow visualization were also made. This facility is originally designed for turbopump inducer performance test and cavitation test. However it can be applied to the pump impeller performance test in the future with little modification.

• International Journal of Fluid Machinery and Systems
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• 제3권1호
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• pp.50-57
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• 2010

The attachment of inducer in front of main impeller is a powerful method to improve cavitation performance. Cavitation surge oscillation, however, often occurs at partial flow rate and extremely low suction pressure. As the cavitation surge oscillation with low frequency of about 10 Hz occurs in a close relation between the inlet backflow cavitation and the growth of blade cavity into the throat section of blade passage, one method of installing an axi-asymmetrical plate upstream of inducer has been proposed to suppress the oscillation. The inlet flow distortion due to the axi-asymmetrical plate makes different elongations of cavities on all blades, which prevent the flow from becoming simultaneously unstable at all throat sections. In the present study, changes of the suppression effects with the axial distance between the inducer inlet and the plate and the changes with the blockage ratios of plate area to the cross-sectional area of inducer inlet are investigated for helical inducers with tip blade angles of $8^{\circ}$ and $14^{\circ}$. Then a conceivable application will be proposed to suppress the cavitation surge oscillation by installing axi-asymmetrical inlet plate.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.439-448
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• 2009

Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the next blade. The first one was designed with extremely larger leading edge sweep, the second and third ones were designed with smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in higher flow rates more than 95% of design flow coefficient, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at higher flow rates, owing to the occurrence of the cavity first in the blade passage and its extension upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.625-630
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• 2001

The inducers in liquid-rocket engines are to increase the inlet pressure of the pump to avoid any malfunction due to cavitation. Inducers are typically designed to be operated with some amount of cavitation for the compactness of the turbopump system. Also, inducers are designed to produce low headrise to prevent the decrease of the overall pump efficiency due to the low efficiency of inducers. In the present paper, a computational study on the hydrodynamic behavior of the inducer for the rocket-engine turbopump are presented including the effect of the mass flow rate under the constant rotational speed. As the mass flow rate is decreased, the inducer showed better performance with strong back flows which may have deleterious effects upon the anti-cavitation ability. But the adopted inducer showed very low headrise with high volume flow rates, which may be caused by the small passage area near the trailing edge. The modified version of the present inducer is proposed and numerically evaluated, which in turn showed better results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.243-247
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• 2005

액체로켓엔진용 터보펌프에서 연료펌프에 대한 수력시험을 수행하였다. 작동유체는 상온의 물이며 펌프는 모터로 구동되고 상온의 물을 작동유체로 이용하였다. 인듀서가 펌프의 양정 및 효율에 미치는 영향은 작지만 펌프의 캐비테이션 성능에는 지대한 영향을 미치는 것을 실험으로 확인하였다. 또한 인듀서 단독의 성능을 살펴보기 위한 시험을 수행하였는데, 캐비테이션 시험 중 인듀서에서 $55\%$ 양정저하가 발생할 때 펌프에서 캐비테이션 임계점에 도달하는 것을 알 수 있었다.

• International Journal of Fluid Machinery and Systems
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• 제3권2호
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• pp.129-136
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• 2010

The attachment of inducer upstream of main impeller is an effective method to improve the suction performance of turbopump. However, various types of cavitation instabilities are known to occur even at the designed flow rate as well as in the partial flow rate region. The cavitation surge occurring at partial flow rates is known to be strongly associated with the inlet back flow. In the present study, in order to understand the detailed structure of internal flow of inducer, we firstly carried out the experimental and numerical studies of non-cavitating flow, focusing on the flow field near the inlet throat section and inside the blade passage of a two bladed inducer at a partial flow rate. The steady flow simulation with cavitation model was also made to investigate the difference of flow field between in the cavitating and no-cavitating conditions.

• 항공우주기술
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• 제3권2호
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• pp.72-80
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• 2004

터보펌프를 구성하는 부분 조합체 중의 하나인 산화제 펌프의 인듀서와 임펠러에 대해서 정적 구조해석을 수행하였다. 먼저 온도, 원심력 및 압력의 영향을 각각 독립적으로 파악한 후 조합된 하중이 작용하는 경우에 대해서 인듀서와 임펠러의 거동을 살펴보았다. 설계된 형상과 재질에 대해서 구조적으로 가장 큰 영향을 미치는 요소는 온도였으며, 모든 경우에 대해서 적절한 안전 여유를 갖는 것으로 예측되었다. 하지만 진동의 영향은 고려되지 않았기 때문에 회전부와 케이싱과의 간섭 여부를 정확히 파악하기 위해서는 추가적으로 진동 해석이 수행되어야 할 것이다.