• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.391-398
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• 2008

LES analysis was conducted with in-house CFD code to investigate the turbulence evolution and interaction due to turbulence ring and splash plate in the gas generator. Though chemical reaction was not accounted for, the results can be useful in determining the turbulence characteristics generated by ring and plate. The calculation results show that the installation of turbulence ring can introduce additional turbulences and improve turbulent mixing in the downstream flow. However, the addition of splash plate in the downstream of TR brings totally different shape of perturbation energy and enstrophy distribution for turbulent mixing. This enhancement can be done by the formation of the intensively strong vorticity production and mixing behind the plate. Pressure drop was found to be a reasonable level of about 1% or less of initial pressure in all calculation cases. Also, calculation results revealed that the variation of TR shape and intrusion length did not change the characteristics of turbulent mixing in the chamber. Even though the effect of installation location of splash plate on the turbulent mixing is not investigated yet, calculation results conclude the addition of splash plate leads to the increase in turbulent mixing with an acceptable pressure drop.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1641-1647
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• 2006

Vibrational relaxation and competitive C-$H_{methyl}$ and C-$H_{ring}$ bond dissociations in vibrationally excited methylpyrazine in the collision with HF have been studied by use of classical trajectory procedures. The energy lost by the vibrationally excited methylpyrazine upon collision is not large and it increases slowly with increasing total vibrational energy content between 20,000 and 45,000 $cm^{-1}$. Above the energy content of 45,000 $cm^{-1}$, however, energy loss decreases. The temperature dependence of energy loss is negligible between 200 and 400 K, but above 45,000 $cm^{-1}$ the energy loss increases as the temperature is raised. Energy transfer to or from the excited methyl C-H bond occurs in strong collisions with HF, that is, relatively large amount of translational energy is transferred in a single step. On the other hand, energy transfer to the ring C-H bond occurs in a series of small steps. When the total energy content ET of methylpyrazine is sufficiently high, either or both C-H bonds can dissociate. The C-$H_{methyl}$ dissociation probability is higher than the C-$H_{ring}$ dissociation probability. The dissociation of the ring C-H bond is not the result of the direct intermolecular energy flow from the direct collision between the ring C-H and HF but the result of the intramolecular flow of energy from the methyl group to the ring C-H stretch.

• Tribology and Lubricants
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• v.40 no.2
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• pp.54-60
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• 2024

This study experimentally identifies the effects of end shape, clearance, total damper length, journal eccentricity ratio, oil supply pressure, and oil flow rate on the damping coefficient of a squeeze film damper (SFD) with piston ring seal ends and a central groove. The SFD is composed of a lubricating fluid flowing between the outer race of a rolling element bearing and cartridge, along with an anti-rotation pin to prevent the rotation of the outer race. The device provides additional viscous damping to a rotating system. Additionally, piston ring seals attached at both ends of the damper increase the damping coefficient of the rotating system by reducing oil leakage. Because these different design conditions affect the damping coefficient of an SFD, we perform experiments including different conditions. Tests show that the damping coefficient increases significantly in the SFD with piston ring seal ends compared with the SFD with open ends. The damping coefficient also increases with increasing total damper length and journal eccentricity ratio, and decreases with increasing clearance. Additionally, in contrast to the trend observed for the SFD with open ends, the damping coefficient for the SFD with piston ring seal ends increases with increasing supply pressure and flow rate as the frequency decreases but shows consistent results as the frequency increases.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.106-114
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• 2003

The pressure ripple in the delivery port is caused by flow ripple, which is induced by variation of pumping chamber volume. The other reason is the reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume, when the pumping chamber is connected with the outlet volume. In this study, a mathematical model is presented for analyzing discharge pressure ripple, which includes vane detachment, cam ring movement , and fluid inertia effects in V-groove in the side plate. From the analysis and experiment, it was found that V-groove on the side plate, coefficient of spring supporting the cam ring, and average discharge pressure are the main factors of discharge pressure ripple in variable displacement vane pump. The theoretical results, provided in this study, were well agreed with experimental results. The analytical model to estimate the magnitude of pressure ripple in this study is expected to be used f3r the optimal design of the variable displacement vane pump.

• Transactions of Materials Processing
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• v.1 no.1
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• pp.33-41
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• 1992

Sintered P/M connecting rod is forged to increase density and to satisfy dimensional specifications. Flow of the materials is different form that of wrought materials due to pores in the preform. The Mises yield function was modified to. include the first invariant of stress tensor, and the associated flow rule was derived by applying the normality rule to the yield function. Axisymmetric and plane-strain finite element analyes were carried out for the ring and beam portions of the connecting rod, respectively. The flow of the preform and density change of the analysis are presented in this paper. A load-stroke curve was also presented by superimposing analysis results for the ring and beam portions.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.63-70
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• 2001

This study is concerned with Finite Element Analysis on welded part of control link fur automobile. For analysis, control link was modeled into two parts, ring and rod. Heating condition, temperature distributions and fatigue fracture strength were analyzed using "HEAT III" and "NDURE" module of NISA II. Metal flow in the process of welding was simulat- ed by $DEFORM^{TM}2D$.The analyzed results were compared with experimental inspection. Quality of welded part was able to be improved by controlling metal flow in the process of welding by increase the friction constant of ring part. Heat transfer analysis and flow simulations were in good agreement wish welding experiments.

• The KSFM Journal of Fluid Machinery
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• v.10 no.6
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• pp.38-43
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• 2007

Pumps for a turbopump generally operate under high rotational speeds and large head rise conditions. Therefore, reliability is a prime design requirement. Floating-ring type seals are frequently employed in a turbopump because of robustness despite of low hydraulic efficiency. There are many researches on the floating-ring seal itself, but the effects of the floating ring seals on the performance of the whole pump are not widely studied in spite of their importance. In the present study, experimental and computational studies on the effects of the radial clearance of the floating ring seals on the performance of a pump were performed. The experimental results showed that the head rise and efficiency increased as the floating-ring seal clearance was decreased. The results also showed the possibility that the leakage flow which was injected to the inlet of the inducer could enhance the suction performance of the inducer by diminishing the size of the backflows.

• Tribology and Lubricants
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• v.22 no.2
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• pp.105-111
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• 2006

The floating ring seal which is used in the high pressure turbo pump is frequently used in the oxidizer pump and the fuel pump of the turbo pump of the liquid propulsion rocket, because it is able to minimize clearance to decrease the leakage flow rate. Compared with contact seal, the floating ring seal has advantage of minimizing clearance without rubbing phenomenon. But, the floating ring seal has a tendency to increase instability in operating condition in the high speed region. In this research, we devised floating ring seal which is inserted bump in the outer surface in order to improve the stability in the high speed region. Through this work, we expect to improve stability of floating ring seal with increasing the direct damping coefficient of seal and decreasing the eccentricity ratio.

• Tribology and Lubricants
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• v.36 no.5
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• pp.253-261
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• 2020

In this paper, we present an experimental investigation of the frequency characteristics and a visual inspection of an oxidizer pump with a modified rear-floating ring seal for a 7-tonf turbopump. An oxidizer pump typically operates at high rotational speeds and under cryogenic conditions. Despite its low hydraulic efficiency, the floating ring seal is frequently employed as a leakage control solution for turbomachinery because it effectively reduces abrasion by friction. When the oxidizer pump starts up, the floating ring moves excursively but locks up stably against the pump casing when the contact pressure increases. The compressive force on the floating ring depends on the hydrodynamic forces induced by the flow through the floating ring. This force is controlled by the nose position of the floating ring. Based on a validation test for a 7-tonf turbopump with two types of floating rings, we concluded that the floating ring with a small diameter nose can move easily with a low contact pressure in the cooling path. This leads to instability of the pressure fluctuation around the floating ring. In contrast, a floating ring with a large diameter nose has a high contact pressure and attaches strongly to the casing, which causes wear and frictional oxidation between the contact surfaces of the impeller and the floating ring.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.57-64
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• 2016

To understand a two-phase flow, a liquid film thickness is one of the important factors. A lot of researches have been performed to measure liquid film thickness with various approaches. Recently, an electrical conductance method which uses the conductivity of the liquid film has been widely applied on measuring the liquid film thickness. Though the electrical method has an advantage in high spatial resolution, as the conductivity of liquid can be affected by its temperature variation, the conventional electrical conductance methods have a limitation in being applied on varying temperature conditions where a heat transfer is involved. The purpose of this study is to develop a three-ring liquid film sensor that overcomes the limitation of the conventional method. The three-ring conductance method can measure the film thickness regardless of temperature variation by compensating the change of liquid conductivity. Considering its application on a wide range of conditions such as high temperature or curved surfaces, the sensor was fabricated on flexible printed circuit board (FPCB) in this study. This paper presents the concept of the measurement method, design procedure, prototype sensor fabrication and calibration results.