Hydraulic Characteristics of Liquid Film Generated by Slit Injector

이형원,Gijeong Jeong,Hyunchang Lee,윤영빈 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.2

Liquid film generated by a jet slit injector on a wall was analyzed experimentally. Liquid film characteristics were investigated by measuring the liquid film thickness distribution for various experimental conditions. At first, the distributions were qualitatively analyzed using backlight imaging. Furthermore, quantitative measurements were performed using a liquid film thickness sensor based on the electric conductance method, which was applied to the high-speed wire-mesh method. The injection angle (15, 30, 45 °), jet velocity (7, 10.5, 13.5 m/s), and injection distance (45, 55, 65 mm) were varied, and the responses of the liquid film were observed. Having increased the injection angle, the main stream thickness decreased and the position of the maximum film thickness moved upstream. A faster jet velocity corresponded to a wider liquid film area and larger perturbation of the liquid film. The injection distance did not affect the characteristics of the liquid film considerably. A hydraulic jump effect was also observed, and a large hydraulic jump affected the film thickness distribution of the main stream. The results of this study can be applied to the development of liquid rocket engines or thrusters using the film-cooling method.

충돌 액막 분석을 위한 전기전도 액막 두께 측정장치 최적설계

이형원 ( Hyeongwon Lee ),이현창 ( Hyunchang Lee ),김태성 ( Taesung Kim ),안규복 ( Kyubok Ahn ),윤영빈 ( Youngbin Yoon ) 한국센서학회 2018 센서학회지 Vol.27 No.6

To analyze the film cooling in a liquid rocket engine, it is necessary to understand the characteristics of the wall-impingement liquid film. We designed an optimal two-dimensional device for measuring the thickness of the liquid film thickness. This device quantitatively measures the liquid-film thickness distribution. In previous liquid-film thickness measuring devices, the liquid film was formed over the entire area of the sensor. However, its formation depended on injection conditions. To compensate for this, optimal resistors are selected. Additionally, saturation variations with partial saturation are analyzed. Furthermore, calibration using the enhanced plate method is conducted with improvements in spatial resolution. The device designed here can be used to analyze the properties of an impingement liquid film with a slit injector. This study can be used for film-cooling analysis in liquid rocket engines.

Emulsion-directed liquid/liquid interfacial fabrication of lanthanide ion-doped block copolymer composite thin films

Hong, Ming,Geng, Yuanyuan,Liu, Mei,Xu, Yuan,Lee, Yong-Ill,Hao, Jingcheng,Liu, Hong-Guo Elsevier 2015 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.438 No.-

<P><B>Abstract</B></P> <P>An emulsion-directed assembly and adsorption approach has been used to fabricate composite films of polystyrene-b-poly(acryl acid)-b-polystyrene (PS-b-PAA-b-PS) and Eu<SUP>3+</SUP> and La<SUP>3+</SUP> ions at the planar liquid/liquid interface of the polymer DMF/chloroform (1:1, v/v) mixed solution (lower phase) and aqueous solutions of the corresponding salts (upper phase). The lower phase gradually transformed to a water-in-oil (W/O) emulsion via spontaneous emulsification due to the “ouzo effect”. Polymer molecules and the metal ions assembled around emulsion droplets that adsorbed at the planar liquid/liquid interface at last, resulting in formation of composite films. The film morphologies and structures depend on Ln<SUP>3+</SUP> ions: polymer/Eu<SUP>3+</SUP> composite films were foam films composed of microcapsules ranging in size from several hundreds of nanometers to micrometers, while polymer/La<SUP>3+</SUP> composite films were composed of hollow spheres several tens of nanometers in size. Fourier transform infrared (FTIR) spectra revealed that the coordination modes of carboxyl groups to Eu<SUP>3+</SUP> and La<SUP>3+</SUP> were bridging bidentate and ionic, respectively, in the two types of composites. These results indicate that stable microcapsules can be fabricated around droplets for polymer/Eu<SUP>3+</SUP> systems, while microcapsules of polymer/La<SUP>3+</SUP> are unstable. This leads to different film morphologies and structures. Compositions of these films were characterized using energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, foam films of polymer/Eu<SUP>3+</SUP>/2,2′-bipyridine (bpy) were fabricated using this approach, and their photoluminescence properties were investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Composite films of block copolymer/Ln<SUP>3+</SUP> were fabricated at liquid/liquid interfaces. </LI> <LI> Eu<SUP>3+</SUP> and La<SUP>3+</SUP> have great effects on morphologies and microstructures of the films. </LI> <LI> Polymer/Eu<SUP>3+</SUP> and polymer/Eu<SUP>3+</SUP>/bpy films exhibit good luminescent properties. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

계면활성제의 농도가 유하액막의 열전달 특성에 미치는 영향에 관한 실험적 연구

김경희(Kyung Hee Kim),강병하(Byung Ha Kang),이대영(Dae-Young Lee) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.6

Falling liquid plays a role in a wide variety of naturally occurring phenomena as well as in the operation of industrial process equipment where heat and mass transfer take place. In such cases, it is required that the falling film should spread widely on the surface forming thin liquid film to enlarge contact surface. An addition of surface active agent to a falling liquid film affects the flow characteristics of the falling film. In this study the heat transfer characteristics for a falling liquid film has been investigated by an addition of the surface active agents. The falling liquid film was formed on a vertical flat plate. As the mass flow rate of liquid falling film is increased, the wetted area is a little increased while the heat transfer rate as well as heat transfer coefficient is significantly increased. It is also found that both wetted area and heat transfer rate is substantially increased while heat transfer coefficient is a little increased with an increase in the surfactant concentration at a given mass flow rate.

접촉각이 유하액막 특성에 미치는 영향에 관한 실험적 연구

김경희,강병하,이대영 대한설비공학회 2006 설비공학 논문집 Vol.18 No.11

Vertical falling liquid film is extensively used in heat and mass transfer processes of many applications, such as evaporative coolers, cooling towers, and absorption chillers. In such cases, it is required that the falling film spreads widely in the surface forming thin liquid film to enlarge contact surface. An addition of surface active agent to a falling liquid film or hydrophilic surface treatment affects the fluid physical properties of the film. Surfactant addition not only decreases contact angle between the liquid and solid surface but also changes the surface from hydrophobicity to hydrophilicity. In this study, the effects of contact angle on falling film characteristics over a vertical surface have been investigated experimentally. The contact angle is varied either by an addition of surfactant to the liquid or by hydrophilic surface treatment. It is found that the wetted area is increased and film thickness is decreased by the hydrophilic treatment as compared with those of other surfaces. With this hydrophilic treatment, the falling liquid film spreads out widely in the surface. As surfactant concentration is increased, wetted area is also increased and the film thickness is substantially decreased.

Atomization Improvement of a Liquid Jet with Wall Impingement and its Application to a Jet Engine Atomizer

Shiga, Seiichi The Institute for Liquid Atomization and Spray Sys 2006 한국액체미립화학회지 Vol.11 No.3

In the present study, capability of improving the liquid atomization of a high-speed liquid jet by using wall impingement is explored, and its application to a jet engine atomize. is demonstrated. Water is injected from a thin nozzle. The liquid jet impinges on a wall positioned close to the nozzle exit, forming a liquid film. The liquid film velocity and the SMD were measured with PDA and LDSA, respectively. It was shown that the SMD of the droplets was determined by the liquid film velocity and impingement angle, regardless of the injection pressure or impingement wall diameter. When the liquid film velocity was smaller than 300m/s, a smaller SMD was obtained, compared with a simple free jet. This wall impingement technique was applied to a conventional air-blasting nozzle for jet engines. A real-size air-blasting burner was installed in a test rig in which three thin holes were made to accommodate liquid injection toward the intermediate ring, as an impingement wall. The air velocity was varied from 41 to 92m/s, and the liquid injection pressure was varied from 0.5 to 7.5 MPa. Combining wall impinging pressure atomization with gas-blasting produces remarkable improvement in atomization, which is contributed by the droplets produced in the pressure atomization mode. Comparison with the previous formulation for conventional gas-blasting atomization is also made, and the effectiveness of utilizing pressure atomization with wall impingement is shown.

Atomization Improvement of a Liquid Jet with Wall Impingement and its Application to a Jet Engine Atomizer

( Seiichi Shiga ) 한국액체미립화학회 2005 한국액체미립화학회 학술강연회 논문집 Vol.2005 No.-

In the present study, capability of improving the liquid atomization of a high-speed liquid jet by using wall impingement is explored, and its application to a jet engine atomizer is demonstrated. Water is injected from a thin nozzle. The liquid jet impinges on a wall positioned close to the nozzle exit, forming a liquid film. The liquid film velocity and the SMD were measured with PDA and LDSA, respectively. It was shown that the SMD of the droplets was determined by the liquid film velocity and impingement angle, regardless of the injection pressure or impingement wall diameter. When the liquid film velocity was smaller than 300 m/s, a smaller SMD was obtained, compared with a simple free jet. This wall impingement technique was applied to a conventional air-blasting nozzle for jet engines. A real-size air-blasting burner was installed in a test rig in which three thin holes were made to accommodate liquid injection toward the intermediate ring, as an impingement wall. The air velocity was varied from 41 to 92m/s, and the liquid injection pressure was varied from 0.5 to 7.5MPa. Combining wall impinging pressure atomization with gas-blasting produces remarkable improvement in atomization, which is contributed by the droplets produced in the pressure atomization mode. Comparison with the previous formulation for conventional gas-blasting atomization is also made, and the effectiveness of utilizing pressure atomization with wall impingement is shown.

Grafoil foam 기판 위의 4He 필름

남상탁 한국물리학회 2019 New Physics: Sae Mulli Vol.69 No.11

Grafoil foam 기판 위에 흡착된 액체 4He 필름에서 온도와 필름의 두께에 따라 달라지는 제삼음파의속력에 대한 이론적인 식을 Rutledge 등의 유체역학적 방법을 사용하여 나타냈다. 그리고, Grafoil foam 기판 위에 흡착된 액체 4He 필름의 제삼음속, van der Waals 상수, 필름의 두께 등의 측정값들을 사용하여액체 4He 필름의 초유체 매개변수들 s/ 와 sd/T 를 계산하였다. Grafoil foam 기판 위에 흡착된 액체4He 필름의 s/ 와 sd/T 는 각각의 기판의 전이온도에서 필름의 두께와 상관없이 각각 0.215와 0.267 사이의 값과 3:46 10 9 g/cm2K와 4:32 10 9 g/cm2K 사이의 값으로 주어지고 제삼음속은 각각의기판의 전이온도에서 필름의 두께를 증가시키면 감소함을 볼 수 있었다. 우리는 Grafoil foam 기판 위에흡착된 액체 헬륨 필름의 두께와 전이온도에 따라 필름의 치유길이와 제삼음속을 나타내는 식 내에 있는보정인자의 값이 낮은 전이온도와 얇은 두께의 필름에서 음이거나 작지만 전이온도가 높고 필름의 두께가두꺼우면 상당히 커짐을 알 수 있었다. We present the third sound-speed of liquid 4He films on Grafoil foam substrates as functions of the temperature and the film depth, which we obtained by using the hydrodynamic method of Rutledge et al.. We also calculated the superfluid parameters s/ and sd/T of the liquid 4He films on Grafoil foam substrates by using the measured values of the third sound-speed, the van der Waals constant, and the thickness of the film. We found that the parameters of s/ and sd/T in liquid 4He film on each Grafoil foam substrate at its critical temperature were between 0.215 and 0.267 and between 3:46 10 9 g/cm2K and 4:32 10 9 g/cm2K which had nothing to do with the film’s thickness. The third sound-speed for the films on each substrate at its critical temperature was found to be decrease with increasing thickness of the film. Also, the value of the complementary factor in the equation representing the film coverage and the third sound-speed as functions of the thickness and critical temperature of liquid 4He films on Grafoil foam substrates seemed to be negative or small for a thin film at its low critical temperature, but it was likely to be much large, for a thick film at its high critical temperature.

Adhesion Characteristics of Fuel Spray Impinging on Flat Wall under High-Temperature and High-Pressure Ambient Condition

( Shintaro Uchitomi ),( Hongliang Luo ),( Keiya Nishida ),( Youichi Ogata ),( Wu Zhang ),( Tatsuya Fujikawa ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

The recent strict regulation of emission for internal combustion engines requires the reduction of pollutant emissions such as soot. The direct-injection spark-ignition (DISI) engine, which has been widely used for passenger cars, can improve thermal efficiency and reduce the emission of carbon dioxide. However, as fuel is injected directly into the cylinder, it is difficult to avoid the wall impingement of spray on the combustion chamber. And liquid films inevitably form on the piston and cylinder surfaces. These films are possible sources of unburnt hydrocarbons and soot emissions. In addition, liquid films have a significant influence on combustion efficiency. To improve the combustion performance of DISI engines, better understandings of the spray-wall interaction and liquid film formation processes are needed. This work investigated the wall impingement and liquid film formation by sprays injected from a mini-sac injector with a single-hole. The experiments were conducted in a constant-volume vessel under various ambient pressure and temperature. A quartz glass with rough surface was used as the flat wall. The refractive index matching (RIM) technique was applied to investigate the spatial distribution and formation process of liquid films. The results showed that the adhered liquid mass and spatial distribution of liquid films, liquid film formation process are affected by the ambient pressure and temperature. In particular, the effect of ambient temperature on liquid film formation is significant. The results of RIM method provided insights into the effects of ambient conditions on the wall impingement behavior and liquid film formation processes.

A numerical modeling for the steady-state performance of a micro heat pipe using thin liquid film theory

Jung, Eui Guk,Boo, Joon Hong Elsevier 2018 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.126 No.1

<P><B>Abstract</B></P> <P>A numerical analysis on heat and mass transfer in a micro heat pipe was performed in this work. Mass, energy, and momentum equations were applied to vapor and liquid phases under steady-state operation in the numerical model. As a result, the trends in mass flow, pressure distribution, and temperature distribution for the working fluid circulating inside the micro heat pipe were obtained for vapor and liquid, respectively. In particular, the vapor-liquid interface shape obtained with a thin liquid film through augmented Young-Laplace equation and areas for heat and mass transfer of liquid and vapor from the vapor-liquid interface thickness were predicted. These areas were applied to solution on the governing equations for vapor and liquid. The numerical model was validated by experimental results. The errors between the experimental and numerical results for the average temperature difference of the evaporator and condenser were found to be less than 1 °C. The errors for thermal resistance had maximum and minimum values of 15.2% and 3.8%, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A numerical analysis on heat and mass transfer in a micro heat pipe was performed. </LI> <LI> Governing equations were applied to both vapor and liquid phases in the model. </LI> <LI> The areas for heat and mass transfer were determined by the liquid-film thickness. </LI> <LI> Predicted results proved an improved accuracy, compared to the previous models. </LI> </UL> </P>