STEADY SIGNLE AND TWO-PHASE FLOW RANS SIMULATION OF PRESSURE SWIRL NOZZLE

( Foad Vashahi ),( Shahnaz Rezaei ),( Jeekeun Lee ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

A combined experimental and CFD study on a high pressure swirl nozzle with agricultural application is presented. The swirling flow is generated with the assist of inner vanes at injection pressure of 15 bar. The spray pattern is captured with high speed camera FastCam Photron SA-X2 and then is correlated with the flow swirl number measured from CFD code Star ccm+ version 11.04. In this particular nozzle, the volume of swirl chamber is adjustable to the end of changing spray pattern from hollow cone at minimum volume and full cone at its maximum. The formation of air core at the discharge orifice of pressure swirl nozzles is widely accepted. Its existence results in formation of hollow cone spray with a fine atomization. Thus, it is essential to apply two-phase flow scheme to simulate the nozzle behavior. However, these schemes are expensive and require heavy computational time. Also, simulation of single phase is by far easier to converge than that of two-phase flow. Thus, single and two-phase flow steady RANS simulations were performed and the results are compared to give insight to whether a single phase simulation suffices the required accuracy. Two-phase flow simulations were perfumed applying VOF scheme and results were validated via the experimentally achieved spray angle. The internal structure is then elaborated in single and two-phase flow and data were compared. In general, the negative volume of axial velocity developed inside the swirling chamber played an important role to achieve a wider hollow cone or narrower full cone spray pattern. In addition, the swirl decay was identified as the main parameter affecting the spray angle. Comparison of two types of simulations also revealed deficiencies in applying single phase condition.

이류체 노즐을 이용한 FPD 세정시스템 및 공정 개발

김민수,김향란,김현태,박진구,Kim, Min-Su,Kim, Hyang-Ran,Kim, Hyun-Tae,Park, Jin-Goo 한국재료학회 2014 한국재료학회지 Vol.24 No.8

As the fabrication technology used in FPDs(flat-panel displays) advances, the size of these panels is increasing and the pattern size is decreasing to the um range. Accordingly, a cleaning process during the FPD fabrication process is becoming more important to prevent yield reductions. The purpose of this study is to develop a FPD cleaning system and a cleaning process using a two-phase flow. The FPD cleaning system consists of two parts, one being a cleaning part which includes a two-phase flow nozzle, and the other being a drying part which includes an air-knife and a halogen lamp. To evaluate the particle removal efficiency by means of two-phase flow cleaning, silica particles $1.5{\mu}m$ in size were contaminated onto a six-inch silicon wafer and a four-inch glass wafer. We conducted cleaning processes under various conditions, i.e., DI water and nitrogen gas at different pressures, using a two-phase-flow nozzle with a gap distance between the nozzle and the substrate. The drying efficiency was also tested using the air-knife with a change in the gap distance between the air-knife and the substrate to remove the DI water which remained on the substrate after the two-phase-flow cleaning process. We obtained high efficiency in terms of particle removal as well as good drying efficiency through the optimized conditions of the two-phase-flow cleaning and air-knife processes.

예조건화 HLLC 기법을 이용한 저 마하수 축소-확대 노즐의 준 1차원 이상유동 해석

염금수(G.S. Yeom) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.1

In this paper, quasi-one-dimensional two-phase flows through converging-diverging nozzles are simulated using a preconditioned HLLC method applied to a compressible two-pressure, one-velocity two-phase flow model. An efficient method estimating a reference Mach number used in the preconditioned scheme has been newly proposed. The developed code has been validated by the benchmark problems of a single-phase liquid water flow and a two-phase water-air flow through a linear nozzle. The computed results are good agreement with the previous one. It is noted that the present computations for the volume fraction profile show somewhat more accurate results than the previous one. The developed code can be used for solving the cavitation problem in water flows through nozzles and hydrofoils.

과수원 내 다목적 살포에 적합한 이류체 노즐 개발에 관한 연구

한광호(Kwang Ho Han),강태경(Tae Gyoung Kang),이동인(Dong In Lee),이철희(Chul-Hee Lee) 유공압건설기계학회 2020 드라이브·컨트롤 Vol.17 No.4

In orchard or crop-growing environments, pesticides are sprayed using various nozzles to prevent pests and improve productivity. Nozzles currently in use are restricted for use in multi-purpose environments, thus, it is necessary to develop new nozzles. In this study, new two-phase nozzles are proposed to improve the performance of the nozzle (flow rate, spray angle, spray particle size). The performance of the two-phase nozzles are predicted through the CFD analysis and the performance of the nozzles is compared with the experiment. The experimental results showed that the proposed two-phase nozzles are available at relatively low operating pressure condition and are capable of extensive spray particle size control. Thus, the proposed nozzles are expected to be available in various orchard environments.

An Analytical Study on the Gas-Solid Two Phase Flows

JianGuo Sun,Heuy Dong Kim 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.5

This paper addresses an analytical study on the gas-solid two phase flows in a nozzle. The primary purpose is to get recognition into the gas-solid suspension flows and to investigate the particle motion and its influence on the gas flow field. The present study is the primal step to comprehend the gas-solid suspension flow in the convergent-divergent nozzle. This paper try to made a development of an analytical model to study the back pressure ratio, particles loading and the particle diameter effect on gas-solid suspension flow. Mathematical model of gas-solid two phase flow was developed based on the single phase flow models to solve the quasi-one-dimensional mass, momentum equations to calculate the steady pressure field. The influence of particles loading and particle diameter is analyzed. The results obtained show that the suspension flow of smaller diameter particles has almost same trend as that of single phase flow using ideal gas as working fluid. And the presence of particles will weaken the strength of the shock wave; the bigger particle will have larger slip velocity with gas flow. The thrust coefficient is found to be higher for larger particles/gas loading or back pressure ratio, but it also depends on the ambient pressure.

2 상 유동 및 물질전달 특성에 미치는 오리피스 노즐형상과 소요동력의 영향

양희천(Hei Cheon Yang) 대한기계학회 2016 大韓機械學會論文集B Vol.40 No.4

호기성 수처리 과정의 폭기에 소요되는 에너지의 이용효율을 높이기 위해서는 물질전달 특성뿐만 아니라 소요동력에 대한 연구가 필요하다. 본 논문은 수직 2 상 유동 및 물질전달 특성에 미치는 오리피스 노즐형상과 소요동력의 영향에 대한 실험적 연구를 목적으로 한다. 측정 변수들을 이용하여 유량비, 소요동력, 물질전달 계수 그리고 물질전달 효율을 산출하였다. 소요동력이 커지면 물질전달 계수는 증가하는 반면에 유량비와 물질전달 효율은 감소하였다. 무차원 면적비가 작은 오리피스 노즐의 유량비, 물질전달 계수 및 효율이 높게 나타났다. 물질전달 특성에 미치는 유량비, 소요동력 그리고 프라우드 수의영향을 평가하기 위한 실험식을 제시하였다. It is necessary to investigate the input power as well as the mass transfer characteristics of the aeration process in order to improve the energy efficiency of an aerobic water treatment. The objective of this study is to experimentally investigate the effect of orifice nozzle design and input power on the flow and mass transfer characteristics of a vertical two-phase flow. The mass ratio, input power, volumetric mass transfer coefficient, and mass transfer efficiency were calculated using the measured data. It was found that as the input power increases the volumetric mass transfer coefficient increases, while the mass ratio and mass transfer efficiency decrease. The mass ratio, volumetric mass transfer coefficient, and mass transfer efficiency were higher for the orifice configuration with a smaller orifice nozzle area ratio. An empirical correlation was proposed to estimate the effect of mass ratio, input power, and Froude number on the volumetric mass transfer coefficient.

Study of divergence angle influence for sonic nozzle in non-equilibrium condensation

Balasubramanian Dhandapani,이장창 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6

The condensation happens generally in a nozzle during expansion of compressed steam from convergent to the divergent part of the nozzle. The divergence angle is the angle measured from the throat of the nozzle to the outlet. In this paper, the outlet is kept constant and the throat diameter is varied. In turn, the divergence angle of the sonic nozzle is altered. The effect of divergence angle on condensation phenomena is investigated with wet steam in a sonic nozzle. For analyzing the wet steam properties, the non-equilibrium condensation model is used. This model is the classical nucleation theory coupled with the droplet growth rate equation. The base nozzle is designed with the throat diameter of 4.5 mm and other dimensions are calculated according to ASME nozzle formulas. Furthermore, the chosen divergence angles are 3°, 4.2°, and 6° for which the throat diameters are 4.5 mm, 3 mm, and 1.5 mm, respectively. As the divergence angle is gradually increased, the position of maximum Mach number of the flow moves upstream, the static temperature of the flow near the throat reaches the lower value, and the droplet nucleation rate is increased. The condensation shock gets gradually stronger with decreasing the divergence angle.

자흡식 벤츄리 노즐에서의 물-공기 이상유동의 특성에 대한 실험적 연구

배현우,유인수,성재용,이명호 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.6

Self-entrainment of air occurs when water is supplied through a venturi nozzle with an air hole in its throat. To study the characteristics of air entrainment, the air flow rates and air volume ratio were measured. The flow inside the nozzle was visualized for various diverging angles and water flow rates. The results shows that air entrainment increases with the water flow rate; however, the air volume ratio remains almost constant. Furthermore, air entrainment is the highest at a diverging angle of 40°. As the water flows downstream, an annular, two-phase flow starts to form in the diverging section, changing the flow pattern to a churn flow. This sudden expansion in the diverging section induces a vortex separation that blocks the pathway of air entrainment when air bubbles are present in the vortex.

A numerical study of two-phase transonic steam flow through convergence-divergence nozzles with different rates of expansion

Mehrzad Shams,Behnam Nikkhahi,Masoud Ziabasharhagh 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.6

During transonic flow of steam in divergence nozzles, flow first supercools and then nucleates to become two-phase droplet flow. This phenomenon especially occurs in the last stages of steam turbines and affects performance. In this research, a numerical scheme for two-phase flow in nozzle passages is developed. An Eulerian-Eulerian reference frame is used for both phases. The shear stress transport turbulence model is used to model the Reynolds stresses appearing in the averaged Navier-Stokes equations. The homogeneous nucleation model is applied for the mass transfer in the transonic conditions. In this paper three nozzles with different rate of expansion are employed to be under study. Overall pressure ratio (static to total pressure) and droplet size are compared with the experimental data and good agreements are observed.

Flow structure characteristics through the AI nozzle with varying design parameters

Milad Khaleghi Kasbi,Reza Alidoost Dafsari,Seung-Hwa Yu,Jeekeun Lee 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

Agricultural nozzles such as air-induction nozzles are designed with the purpose of minimizing spray drift and controlling flow behavior such as spray angle and droplet size. To examine unsteady flow behavior inside an AI nozzle, experimental data and numerical analysis are merged in this paper. The mixture approach and the k- RNG turbulent model is used to clarify the effect of geometrical parameter on the flow structure inside the AI nozzle. It has been investigated that the behavior and size of the vortices decreased and became increasingly unstable as the size of the mixing chamber decreased.