• Journal of Aerospace System Engineering
• /
• v.14 no.5
• /
• pp.100-106
• /
• 2020

Turbopumps for liquid rocket engines are exposed to various cavitation instabilities under their operating conditions. The instabilities affect the stability of the turbopumps. To make sure of the stability of the turbopump of KSLV-II, the present work examined the characteristics of the cavitation instabilities during the turbopump assembly test. In the test, the LOx pump was operated under super-synchronous rotating cavitation and attached to uneven cavitation. In the vibration analysis of the fuel pump, the characteristic frequency by the super-synchronous cavitation of the LOx pump was clearly shown.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.4
• /
• pp.61-67
• /
• 2018

High-frequency signals are analyzed at the inlet/outlet pipeline and pump casing during cavitation tests of the LOx pump for liquid rocket engines. Root-mean square values of all data are investigated with respect to cavitation number. The values of synchronous, harmonic, and cavitation instability frequencies are also calculated. Pressure pulsations of the inlet and outlet pipelines are affected by cavitation instabilities. The 3x component (i.e., the blade-passing frequency of the inducer) is predominant in the outlet pulsation sensor. This seems to be related to the fact that the number of impeller blades is a multiple of the number of the inducer blades. The cavitation instability is also measured at the accelerometer of the pump casing.

• Aerospace Engineering and Technology
• /
• v.8 no.1
• /
• pp.73-81
• /
• 2009

Casing leak tests using three kinds of static seals are performed by simulating test section for a 75 ton thrust class turbopump under ambient and cryogenic temperature environment. As results of application of Conical, PTFE, and C static seals to leak tests, even though they all work in normal temperature condition, only the PTFE and C static seals show good sealing performance in cryogenic condition. However, the Conical static seal fails because of the different thermal expansion rates due to the use of different materials in a LOX pump. It is found that unlike the PTFE and C static seals with sealing surfaces in axial direction, the sealing surface of the Conical static seal is in radial direction that may cause leak when the casings thermally shrink in radial direction. Especially, the C static seal reveals excellent sealing performance even for a used seal.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2005.11a
• /
• pp.375-383
• /
• 2005

The present paper describes the first development of a LOX/kerosene type turbopump in Korea. The liquid rocket engine, that the turbopump can be applied to, has a 30-ton(metric) level of vacuum thrust and employs a gas generator cycle. The turbopump consists of two single-stage centrifugal pumps, that is, LOX and kerosene pumps, and one single-stage impulse turbine. Inter-propellant seal(IPS) is located between the LOX pump and the kerosene pump to avoid any interaction between the propellants. A series of component and TPU(Turbopump Unit) test has been completed in the level of simulant propellants and ready for hot firing tests.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.93-100
• /
• 2020

The turbopump of the liquid rocket engine adapts an inducer to minimize the cavitation due to the variations of the propellants supply condition. However, the inducer introduces cavitation instabilities which are well-known problems in the engine development. In this paper, operational characteristics by the cavitation instabilities are analyzed and the reliability of the engine is checked when the first stage engine of the KSLV-II is tested at the low inlet pressure conditions. The characteristic frequencies representing the cavitation instabilities of the LOx pump are clearly found in various high frequency sensor signals around the entire engine in addition to the LOx and fuel pump.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.1099-1102
• /
• 2017

High frequency signals are analyzed which are measured at the inlet / outlet pipeline and pump casing during cavitation tests of the fuel pump for the liquid rocket engine. RMS values of each data are shown according to the cavitation number and compared with those of the LOx pump tests and the impact of the cavitation instability is also explored. Analogies about the cavitation number are confirmed between high frequency data of both pumps. In addition, the cavitation instability is found in all the signals and has an affect on the outlet pressure pulsation of the fuel pump.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.3
• /
• pp.25-37
• /
• 2005

For pump-fed rocket propulsion system, the temperature of LOX to be supplied to turbopump inlet should be satisfied with pump inlet temperature requirement during all operating stages, as excessive temperatures can result in cavitation due to reduction in NPSH, thus either damaging the pump or adversely affecting pump performance rise. So exact estimation of LOX temperature rise is absolutely needed for developing reliable propulsion system. This paper presents systematic analysis scheme for estimating inner process of cryogenic propellant tank which is needed for LOX temperature rise. And this paper presents LOX temperature rise and thermal stratification for all rocket operating stages including cooling, filling, waiting, pre-pressurization and firing, with the application of buoyancy driven boundary layer theory.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.61-68
• /
• 2020

7-tonf turbopump real-propellant tests in Naro Space Center were conducted and high-frequency signals from an accelerometer and pressure sensors installed on the casing and the inlet/outlet pipeline of LOX pump were analyzed to estimate the structural and hydrodynamic stabilities. Waterfalls, frequency spectrums and RMS(Root Mean Square) values of the measured signals were calculated and characteristic instability frequencies by the rotating cavitation and the rear floating ring seal(F.R.S) were investigated. Static pressures of the inlet/outlet pipeline and an acceleration of the pump casing are strongly affected on pressure fluctuation induced by the rear floating ring seal in the leakage path. Despite the acceleration RMS value seems totally small, the rotating-speed-related synchronous frequency affecting the shaft instability is distinctly observed in the frequency contour.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.05a
• /
• pp.47-53
• /
• 2010

A performance test of a 75 ton class turbopump inter propellant seal is conducted using water to evaluate leakage and endurance performance. Each fuel pump side part and oxidizer pump side part of a prototype inter propellant seal has been tested for verifying endurance performance during total accumulated test time 2,100 sec in water. The fuel pump side part with 1 stage carbon floating ring seal shows average leakage rate 13.7 gram/sec under average seal differential pressure 9.4 bar. On the other hand, the LOx pump side part with 2 stage carbon floating ring seal shows average leakage rate 7.3 gram/sec under average seal differential pressure 9.5 bar. After the endurance performance test, the inter propellant seal shows good physical condition. A cryogenic leakage performance test of the inter propellant seal will be performed using LN2 in the near future.

• Aerospace Engineering and Technology
• /
• v.4 no.1
• /
• pp.196-202
• /
• 2005

In cryogenic feeding system of turbo pump fed liquid-propulsion rocket, rise of cryogenic propellant temperature can bring into geysering in pipe or cavitation in turbo pump. In this paper, performance analysis of recirculation line which is one of the method to inhibit these phenomenon is carried out based on the configuration of KSLV-I 1st stage LOX feeding system, and parametric study to find design parameter. Diameter and re-entrance height, initial LOX temperature, ullage pressure, and natural convection heat transfer coefficient are varied to see the effects on performance. Additional He is injected into recirculation line to promote LOX recirculation. 1-dimensional analysis using network-solver, SINDA/FLUINT is carried out.