Soon-Sam Hong

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.

Effects of Floating-Ring Seal Clearance on the Pump Performance for Turbopumps

Pumps for a turbopumpgenerally operate under high rotational speeds and large-head-rise conditions. Therefore, reliability is a prime design requirement. Floating-ring seals are frequently employed in a turbopump because of robustness despite relatively high leakage losses. A number of studies have been performed on the floating-ring seal itself, but the effects of the floating-ring seal on the performance of the whole pump are not widely studied, in spite of their importance. The effects of floating-ring seal clearance on the hydraulic and suction performances of a pumpare investigated byboth experimental and computationalmethods in the present study.The experimental results showed that the head rise and the efficiency increased as the floating-ring seal clearance decreased. The results also showed that the leakageflow injected into the inducer inlet enhanced the suction performance of the pumpbydiminishing the size of the backflows. The strength of the backflow becomes weak as the injected leakage flow at the inducer inlet prevents the flow from prerotation.

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.

Study on the Hydraulic Performance of a Turbopump Inducer

The present study focuses on the flow analysis of a turbopump inducer by performing both numerical and experimental methods to provide designers with valuable information. Global performance data (head and efficiency), and detail flow fields (outlet flow angles, pressures and velocity vectors) are measured and compared with the computational data. Generally a good agreement is obtained between both results. But some discrepancies are observed due to complex flows such as backflows at the inlet, etc. The visualization of the backflow at the inducer inlet is also conducted for the validation showing that the prediction overestimates the size of the backflow. And it is shown that the slight modification of the trailing edge shape of the inducer can affect the performance of the inducer.Copyright

Effect of Solidity on the Performance of Turbopump Inducer

The hydraulic and suction performance of an inducer varies sensitively with the inducer geometry and this paper deals with solidity as the inducer geometry parameter. The typical performance characteristics of a basic inducer was investigated and tests with another three inducers of which the solidity is different from each other were performed, so the effect of solidity on the inducer performance was experimentally investigated. For a fixed flow coefficient, required NPSH of the inducer did not follow the conventional similarity rule, so this paper suggested another empirical formula. The hydraulic and suction performance was measured at four cases of the tip solidity ranged from 1.32 to 2.76. As long as the tip solidity had the value above 1.84, the hydraulic and suction performance of the inducer increased with decrease in the tip solidity. With further decrease in the tip solidity up to 1.32, however, inducer head decreased and the suction performance dropped sharply.

Numerical Study on the Hydrodynamic Performance Prediction of a Turbopump Inducer

In the present paper, computational studies on the hydrodynamic behavior of the inducer for the rocket-engine turbopump are presented including the effect of the mass flow rate. As the mass flow rate is increased, the inducer showed better performance with weak back flows which may have deleterious effects upon the anti-cavitation ability. But the adopted inducer showed low head rise with high volume flow rates, which may be caused by the small passage area near the trailing edge. The static pressure distributions at the shroud surface are compared with experimental results showing very good agreements except near the leading edge where strong back flows are present. The overall performance of the inducer such as, efficiency, head rise is also compared with experiments. The computational results are generally in good agreements with experimental ones near the design point, but two results show discrepancy at the high flow rate.冗⨀

Effect of Tip Clearance on the Flow and Performance of a Centrifugal Compressor

To see the tip clearance effect on a centrifugal compressor, time-resolved flow measurements were carried out at the discharge of a centrifugal compressor impeller, which is 30 deg back swept from radial and operated at the blade tip speed of 260 m/s. Tested were six cases of tip clearance ratio ranged from 0.06 to 0.21. A fast response aerodynamic probe equipped with a single pressure sensor was used for the flow measurements. From the distribution of time-resolved relative velocity, the jet-wake structure was observed. The wake downstream of the splitter blade was located in the shroud-suction corner, but that downstream of the full blade was in the mid-shroud. By increasing the tip clearance, the wake region was increased and the deficit of the relative total pressure governed the wake region, therefore, the loss was enlarged.Copyright

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.

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.

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