• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.9
• /
• pp.2261-2270
• /
• 1995

Flow patterns were measured in an unshrouded centrifugal impeller. The flow rate in measurements was fixed at the value corresponding to a nearly zero incidence at the blade inlet. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes from the inlet to the outlet of the impeller rotating at 700rpm, which diameter is 0.39 meter, and the static pressures and the slip factor at the impeller outlet were calculated from the measured values. From the measured data, the primary/secondary flows, the leakage flows, the wake-jet flows, static pressure distribution on blade surfaces and the wake production mechanism in the impeller passage were investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.675-678
• /
• 2017

In the present, various methods have been employed to obtain the lesser thrust loss. Numerical simulations have been carried out for optimizing the thrust vector control system. Thrust vector control based on coflowing shear layer is an effective method to control the primary jet direction in the absence of moving parts. Thrust vector in symmetric nozzles is acquired by secondary flow injections that result to boundary layer separation. The pressure in secondary flow inlet was varied to check the deflection angle of jet flow.

• Journal of Engineering Education Research
• /
• v.27 no.4
• /
• pp.21-27
• /
• 2024

This study introduces a series of processes aimed at understanding the noise characteristics generated by jet engines and devising measures to mitigate them through interdisciplinary capstone design projects. During the project execution, educational methods were applied to foster 4Cs (creativity, communication, collaboration, critical thinking) competencies. Project objectives were set through team discussions, and individual team members were assigned primary roles to act as subgroup leaders. As a result, the project was executed as follows: combustion tests were conducted using an SR-30 turbojet engine to generate noise, and the locations and characteristics of the noise sources were identified using beamforming techniques and frequency analysis applied to a 30-microphone array. Additionally, chevron nozzles were designed and fabricated to confirm their noise reduction performance.

• Journal of Environmental Science International
• /
• v.32 no.8
• /
• pp.555-561
• /
• 2023

A study is to predict the effective pulsing distance following to the pulsing pressure, nozzle diameter, filtration velocity using numercial analysis techniques and use it as an efficient operation condition and economic data for on-line type pulse air jet bag filter. Filtration area 6 m² condition, calculate filter resistance coefficient for simulation through the primary experiments using coke dust. For CFD simulation, analysis pulsing characteristics about nozzle diameter, filtration velocity and pulsing pressure. The maximum pulsing length of on-line type pulse air jet bag filter, in 10mm nozzle, filtration velocity 1.5m/min and pulsing pressure 5 bar conditions, is 2,285 mm, maximum length is 76.2% of the total filter bag, which is sufficient to pulsing. In 12mm nozzle, pulsing pressure 5 bar and filtration area 1.22 m² conditions, the maximum pulsing length of on-line type pulse air jet bag filter is 1,744~2,952 mm, and the maximum length is 2,952 mm indicates pulsing air can be reached to the bottom of filter bag. When the nozzle diameter is increased 8mm to 10mm, maximum pulsing length is extended 40~47%, and increased 10mm to 12 mm, maximum pulsing length is extended 10~17%. For effective pulsing, over the 5bar of pulsing pressure and larger than 10 mm of nozzle diameter are required.

• Journal of Embryo Transfer
• /
• v.33 no.4
• /
• pp.343-348
• /
• 2018

Although the efforts to establish fish embryonic stem cells (ESCs) have been made for a long time, derivation of authentic ESCs that possess pluripotency is still difficult suggesting a need for the stepwise optimization of the methods to establish fish ESCs. Primary culture of the blastomeres from the embryos at blastula stage is a critical step for establishing continuous ESC lines. Here, we evaluated the effects of temperatures and basal media on primary culture of blastula embryo-derived blastomeres in marine medaka (Oryzias dancena). The blastomeres were isolated from the blastula embryos and cultured in various conditions designed by the combination of 4 temperatures including $28^{\circ}C$, $31^{\circ}C$, $34^{\circ}C$, and $37^{\circ}C$ and 2 basal media including Dulbecco's modified eagle's medium (DMEM) and Leibovitz's L-15 medium (L15). With the exception of a case cultured in L15 at $31^{\circ}C$, the rate of primary cell adherence reached 100% when the blastomeres were cultured over $31^{\circ}C$. The period for primary adherence was significantly shorter in the groups cultured in $34^{\circ}C$ and $37^{\circ}C$ than in the ones in $28^{\circ}C$ and $31^{\circ}C$. The proportion of subculture was significantly high in the group cultured in DMEM at $31^{\circ}C$ compared to the other groups. Collectively, we demonstrated that the culture in DMEM at $31^{\circ}C$ was effective to primary culture of the blastomeres derived from blastula embryos.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.705-708
• /
• 2011

Ejector system can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an design procedure on the configuration and operating condition of multi-ejector for the various high altitude simulation.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1637-1642
• /
• 2004

Experimental and computational studies were performed to investigate the effectiveness of a thrust vectoring method using a counterflow concept. A shadowgraph method was used to visualize the supersonic jet expanded from a two-dimensional convergent-divergent nozzle and deflected by a now suction. The primary nozzle pressure and suction nozzle pressure ratios are varied between 3.0 and 5.0, and between 0.2 and 1.0 respectively. The present experimental and computational results showed that, for a given primary nozzle pressure ratio, a decrease in the suction nozzle pressure ratio produced an increased thrust vector angle, and during the change processes of the suction pressure, a hysteresis effect of the thrust vectoring was found through the wall pressure distributions.

• Journal of the Korean Society of Visualization
• /
• v.21 no.2
• /
• pp.102-110
• /
• 2023

With the global shift from a carbon-based economy to a hydrogen-based economy, understanding the sloshing phenomenon and its impact on boil-off rate (BOR) in liquid hydrogen (LH2) tank trailers is crucial. Here, we analyze the primary breakup process under sloshing phenomena in a liquid fuel tank. We observe the growth of multiple holes on the sheet-like structures and the formation of ligament structures reminiscent of jet atomization. Through the extraction of three-dimensional liquid regions, we analyze the geometrical characteristics of these regions, enabling the classification of sheets, ligaments, and droplets. The present findings could contribute to understanding the breakup mechanism and hold potential for the development of strategies aimed at minimizing BOR.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.2 no.2
• /
• pp.83-87
• /
• 1998

To reduce the supersonic jet noise from the liquid rocket engine, water injetion silencers were designed and tested. Test variables were the mass flow rate of water jet, the length of primary pipe and the diameter of expansion pipe. Followings are the results of this study. 1. From the same mass flow rate of water, longer primary pipe was more effective to reduce the noise. 2. Noise level was significantly reduced with increasingly water flow rate. 3. The optimum water flow rate was 10～12 times of the propellant flow rate. 4. By installing expansion pipe, noise level was reduced approximately 30㏈ compared to without expansion pipe

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.9
• /
• pp.847-854
• /
• 2013

The objective of this study is to experimentally investigate the mixed flow and oxygen transfer characteristics of a horizontally injected aeration process using an annular nozzle ejector. The flow rate ratio, pressure ratio and ejector efficiency are calculated using the measured flow rate and pressure with the experimental parameters of the ejector pitch and primary flow rate. The visualization images of mixed flow issuing from the ejector are analyzed qualitatively, and the volumetric oxygen transfer coefficients are calculated using the measured dissolved oxygen concentration. The mixed flow behaves like a buoyancy jet or horizontal jet owing to the momentum of primary flow and air bubble size. The buoyancy force of the air bubble and the penetration of mixed flow are found to be important parameters for the oxygen transfer rate owing to the contact area and time of two phases.