• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.185-192
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• 2010

Design of velocity-compounded turbine for 75ton class LRE turbopump application and pressure compounded turbine for 30ton class LRE turbopump has been performed. 1D calculation and CFD analysis were conducted in determining blade and flow passage shape of velocity compounded turbine iteratively. Finally, 23.1% improved specific power and 5% reduced weight turbine to the original design was developed. In case of pressure-compounded supersonic turbine design, rotational speed was increased by 50% and the effect of carryover ratio, 2nd nozzle installation angle, leakage flow of 2nd nozzle, and work sharing factor was studied. Final 1D design resulted 36% increased specific power and 51% reduced weight comparing to the original single-row impulse turbine. It is anticipated that nozzle flow path design will be very important for the accomplishment of expected performance of pressure-compounded turbine and nozzle shape optimization will be conducted through the CFD analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.11-18
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• 2021

Nano bubble water is used in various washing processes, including cleaning of solar panels, salt rejection of roads, and cleaning precision parts of machines. High cleaning efficiency and water conservation are obtained by applying nano bubbles during pretreatment of the marine waste cleaning system. This study compared the salt rejection of nano bubble water, and it was revealed that marine waste was produced by wood immersed in 200,000 mg/L NaCl solution. Using tap water and nano bubble water for washing, comparisons of the surface salt concentrations of wood were determined according to the nozzle, orifice diameter, pump speed and washing time. Decreased surface salt concentration was observed on the wood surface with increasing washing time. Water consumption was optimal between 5- and 10-seconds washing time. Increasing orifice diameter of the nozzle reduced the spraying pressure, with consequent increase in the wood surface salt concentration, thereby establishing the importance of orifice diameter of the nozzle. Compared to levels obtained with tap water, salt concentration of the wood surface after washing with nano bubble water was 2.2% lower with sector nozzle, and 30.9% lower with circular nozzle. In the washing experiment using nano bubble water, the salt concentration on the wood surface was about 9.5 mg/L lower when washed with sector nozzle than the circular nozzle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.19-22
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• 2003

Ejector-diffuser system is one of fluid machinery which can entrain the fluid in low pressure part and transport it to the higher pressure part. The conventional ejector-diffuser system has been pointed out that its overall efficiency is quite low compared with other fluid machinery since it is derived by only the pure shear stresses. In the present study, 4, 6, and 8 lobed petal nozzles with a design Mach number of 1.7 are adopted as a primary nozzle to improve the performance, and are compared with a conventional circular nozzle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.758-759
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• 2010

In this study, it was experimentally confirmed that the phenomenon of resonance effect of wave drag in two wavy walls. The channel had saw-tooth type of relief surfaces when supersonic gas flows into this channel. Experiment was carried out on the differential apparatus by conducting the comparative test of two nozzles (round sonic nozzle and two-dimensional nozzle with wavy walls). The two-dimensional nozzle was joined alternately with flat walls which had saw-tooth type of symmetrical and asymmetric reliefs. Two-dimensional nozzle was designed for the M=3 and profiled parabolic contour.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.265-277
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• 2003

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.207-215
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• 2020

Design of a shape transition nozzle is carried out as a part of building a lab-scale supersonic combustion experimental equipment. In order to connect directly the circular shaped vitiation air heater to the square shaped scramjet combustor, area change is evaluated by using the method of characteristics. Shape transition function is introduced to control the transition rate. Boundary layer correction was made through the three-dimensional computational fluid dynamics with the assessment on the several shape transition functions. The shape transition nozzle is proved minimizing the growth of boundary layer at the center of the rectangular nozzle surfaces that caused by the pressure gradient at the corners of the rectangular nozzle and the following recirculation regions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.779-787
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• 2013

The effects of various nozzle configurations on infrared signature are investigated for the purpose of analysing the infrared signature level of aircraft propulsion system. A virtual subsonic aircraft is selected and then a circular convergent nozzle, which meets the mission requirements, is designed. Convergent nozzles of different configurations are designed with different geometric profiles. Using a compressible Navier-Stokes-Fourier CFD code, an analysis of thermal flow field and nozzle surface temperature distribution is conducted. From the information of plume flow field and nozzle surface temperature distribution, IR signature of plume and nozzle surface is calculated through the narrow-band model and the RadThermIR code. Finally, qualitative information for IR signature reduction is obtained through the analysis of the effects of various nozzle configurations on IR signature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.828-835
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• 2019

An artificial rainfall system is used widely as a research tool for generating model experiment data. Artificial rainfall devices have been used in many studies, but studies of the rainfall distribution are not considered as important issues. To simulate various rainfall characteristics, it should be possible to simulate from low to high intensity, and the homogeneity of the rainfall distribution should be ensured. In this study, the maximum rainfall intensity was set to 130mm/hr and controlled by 10mm/hr. In addition, the aim was to secure a uniform coefficient value of 80% or more. To this end, rainfall tests were performed according to the nozzle type, diameter, position, and pump pressure. The rainfall test showed that the circular nozzle was suitable, and the nozzle size was 1.9mm and 1.4mm. The optimal pump pressure was found to be 3~6kg/㎠. The rainfall intensity tended to increase linearly with increasing pump pressure. Based on the rainfall test results, a rainfall control manual was produced with variables, such as pump pressure, nozzle type, and number of nozzles. As a result of rainfall verification, rainfall intensity showed a 3.1% error with a uniformity coefficient of 86%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.04a
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• pp.63-72
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• 1997

본 논문은 분사제트 주위에 형성되는 와류를 조절하여 제트를 제어하기 위하여 유동가시화, 속도분포 및 난류성분을 측정하는 실험을 수행하였다. 와류를 조절하기 위한 방법으로 제트노즐 주위에 환형관을 설치하여 환형관으로부터 2차제트를 분사 또는 흡입함으로써 제트주위에 형성되는 전단류를 변화시켰다. 2차제트 분사시 주제트 주위에 형성되는 와류의 발달을 억제함으로써 제트 포텐셜코어의 길이가 아주 길어지는 제트유동을 얻을 수 있었다. 환형관으로부터 주제트주위의 유체를 흡입하는 경우 제트주위의 전단류가 흡입비 R=1.3∼l.65에서 대류불안정성에서 절대불안정성으로 바뀜으로써 형성된 와류가 하류에서 제트중심부까지 발전, 결합되는 것을 방지하여 더 긴포텐셜코어와 중심에서 낮은 난류강도를 얻었다. 위의 결과는 환형관 주위에 부착한 깃의 높이 변화에 따라서 변화하였는데, 이것은 깃이 환형관을 통한 흡입유동의 유로역할을 함으로써 제트밖으로부터 흡입되는 것을 방지할 수 있었다. 분사제트 벡터링을 위하여 제트노즐 주위의 환형관을 이등분하여 한쪽으로만 제트주위의 유동을 흡입함으로써 제트주위에 다른 전단류를 형성함과 동시에 Coanda효과를 이용하여 분사제트를 편향시켰다. 편향되는 정도 및 난류성분은 홉입속도 비에 따라서 크게 바뀌었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.983-991
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• 2009

The heat transfer phenomenon was investigated in this study when a circular water jet with low velocity flows to the downward facing heated circular plate and against the direction of gravity. Data are presented for jet flow rate between 0.23 and 2.3 l/min, jet fluid temperature of 24$^{\circ}C$, heat fluxes between 345 and 687 W/m$^2$, H/D=1, 2 and 3 with a single round jet diameter 2mm. The effects of heat flux, jet velocity and H/D on the local heat transfer are investigated in for the various regions of jet impingement. The local heat transfer distributions are analyzed based on the visualization of jet flow field. Data from experimental results are correlated by expressions of the form Nu=0.01$Re^{0.58}{\cdot}Pr^{0.4}$.