Loading [MathJax]/jax/output/CommonHTML/jax.js
  • Title/Summary/Keyword: Droplet Model

Search Result 341, Processing Time 0.033 seconds

Numerical Studies on Vaporization Characterization and Combustion Processes in High-Pressure Fuel Sprays (고압 상태에서의 연료 분무의 증발 및 연소 특성 해석)

  • Moon, Y.W.;Kim, Y.M.;Kim, S.W.;Kim, J.Y.;Yoon, I.Y.
    • Journal of ILASS-Korea
    • /
    • v.3 no.3
    • /
    • pp.49-59
    • /
    • 1998
  • The vaporization characteristics and spray combustion processes in the high-pressure environment are numerically investigated. This study employ the high-pressure vaporization model together with the state-of-art spray submodels. The present high-pressure vaporization model can account for transient liquid heating, circulation effect inside the droplet forced convection, Stefan flow effect, real gas effect and ambient gas solubility in the liquid droplets. Computations are carried out for the evaporating sprays, the evaporating and burning sprays, and the spray combustion processes of the turbocharged diesel engine. Numerical results indicate that the high-pressure effects are quite crucial for simulating the spray combustion processes including vaporization, spray dynamics, combustion, and pollutant formation.

  • PDF

Numerical Simulation on the Performance of Axial Vane Type Gas-Liquid Separator with Different Guide Vane Structure

  • Yang, Fan;Liu, Ailan;Guo, Xueyan
    • International Journal of Fluid Machinery and Systems
    • /
    • v.10 no.1
    • /
    • pp.86-98
    • /
    • 2017
  • In order to obtain high efficiency and low resistance droplet separation apparatus, axial vane type gas-liquid separators with different guide vanes were designed, and the RNG kε model as well as discrete phase model (DPM) were used to investigate the flow pattern inside the separators. It was shown that the tangential velocity distribution under different guide vanes have Rankine vortex characteristics, pressure distribution exhibits a high similarity which value becomes big as the increase of the blade outlet angle and the decrease of the guide vane numbers. The increase of the guide vane numbers and the decrease of the blade outlet angle could make separation improve significantly. The separation efficiency is almost 100% when the droplet diameter is bigger than 40μm.

임계 혼합 용액에서의 DC Kerr 효과

  • 강동철;이재형;장준성
    • Proceedings of the Optical Society of Korea Conference
    • /
    • 1988.06a
    • /
    • pp.82-85
    • /
    • 1988
  • 임계 연계용액에서의 DC Kerr 효과를 측정하고 임계온도 근처에서 Kerr상수가 발산하는 등의 임계 현상이 나타남을 관측하고 임계지수를 측정한다. 이로부터 현상학적 모델인 방울모델(droplet model) 의 타당성을 조사한다.

  • PDF

NUMERICAL STUDY ON THE OPTIMAL DESIGN OF SPRAY SYSTEM IN PACKED BED SCRUBBER (충진층식 스크러버의 스프레이 시스템 최적 설계에 대한 수치해석적 연구)

  • Ko, S.W.;Ro, K.C.;Ryou, H.S.
    • Journal of computational fluids engineering
    • /
    • v.12 no.1
    • /
    • pp.28-34
    • /
    • 2007
  • This study evaluates the performance of the packed bed scrubber and proposes the optimization of spray system for improvements of collection efficiency. The packed bed scrubber is used primarily in the semiconductor manufacturing process. The mean diameter of entering solid particles in scrubber is the submicron. The impaction between water droplets and solid particles is an important factor in removing the solid particles. Thus, the coverage area of spray system influences on the collection efficiency. The collection efficiency of a single droplet is calculated through the mathematical model and numerical calculations are performed for coverage area for each nozzle type (Droplet diameters: 500, 319.5, 289.5μm) and injected directions (0, 15, 30). In case of nozzle type 3, the collection efficiency of a single droplet is highest but the collection efficiency of spray system has lowest value because the ratio of flow rate between the gas and water is below 0.1. The results show the coverage area ratio is about 85% in the case of nozzle type 3 and downward sirection 15. It was shown that a coverage area increase by two times than an existing spray system. In simulation of demister, collection efficiency by demister is predicted about 80% and the pressure drop in demister is below 3.5 Pa.

A Study on the Flow Characteristics of Gasoline Spray across the Suction Air Stream (흡입공기분류를 가로지르는 가솔린 분무의 유동 특성 연구)

  • 김원태;강신재;노병준
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.7 no.9
    • /
    • pp.63-74
    • /
    • 1999
  • When a fuel was injected with opening the intake valve of a port fuel injection engine, the spray atomization and flow characteristics in the intake port have a strong influence on the mixture formation of a combustion chamber. Thus , this study was to clarify the spray flow characteristics of the air-assist gasoline spray with fine dropkets across the suction air stream in model intake port. For the simulated opening intake valve in port, suction air stream was varied to 10m/s ∼30m/s. And fuel pressur ewas fixed to 300kPa, but air assist pressure was varied to 0∼25kPa for a vairable spray conditions. Spray flow trajectory was investigated by means of laser sheet visualization and the measurements of droplet sizes and velocities were made by PDPA system. Measured droplets within the spray flow field were subdivided into five size groups and then, the flow characteristics of droplet size groups were investigated to the spray across a suction air stream.

  • PDF

Unstructured Finite-Volume Analysis of Vaporization Characteristics of Fuel Droplets in Laminar Flow Field (비정렬 유한체적법을 이용한 유동장 내의 연료액적 증발 특성 해석)

  • Kim, T.J.;Kim, Y.M.;Sohn, J.L.
    • Journal of ILASS-Korea
    • /
    • v.5 no.1
    • /
    • pp.13-22
    • /
    • 2000
  • The present study has numerically analyzed the vaporization characteristics of fuel droplets in the high temperature convective flow field. The axisymmetric governing equations for mass, momentum, energy, and species are solved by an iterative and implicite unstructured finite-volume method. The moving boundary due to vaporization is handled by the deformable unstructured grid technique. The pressure-velocity coupling in the density-variable flows is treated by the SIMPLEC algorithm. In terms of the matrix solver, Bi-CGSTAB is employed for the numerically efficient and stable convergence. The n-decane is used as a liquid fuel and the initial droplet temperature is 300K. Computations are performed for the nonevaporating and evaporating droplets with the relative interphase velocity(25m/s). The unsteady vaporization process has been simulated up to the nondimensional time, 25. Numerical results indicate that the mathematical model developed in this study succesfully simulates the main features of the droplet vaporization process in the convective environment.

  • PDF

Analysis of Heat Transfer Performance of Oxi-nitriding Surface during Droplet Evaporation (산질화 표면에서의 액적 증발 열전달 성능 분석)

  • Kim, Dae Yun;Lee, Seong Hyuk
    • Journal of ILASS-Korea
    • /
    • v.24 no.4
    • /
    • pp.203-208
    • /
    • 2019
  • In general, the oxi-nitriding method is well known as such a surface treatment way for substantial enhancement in corrosion resistance, even comparable to that of titanium. However, there are still lacks of information on thermal performance of the oxi-nitriding surface being of additional compound layers on the base substrate. Above all, the quantitative measurement of its thermal performance still was not evaluated yet. Thus, the present study experimentally measures the thermal resistance of the oxi-nitriding surface during droplet evaporation and then estimates heat transfer performance with the use of the onedimensional heat transfer model in vertical direction. From the experimental results, it is found that the total evaporation time slightly increased with the thermal resistance caused by the oxi-nitriding layer, showing a maximum difference of approximately 20% with that of the bare surface. Although the heat transfer performance of oxi-nitriding surface became slightly lower than that of the bare surface, the oxi-nitriding surface exhibits much better heat transfer performance compared to titanium.

A Numerical Analysis on the Characteristics of Spray by Swirl Injector in Gas Turbine Combustor (가스터빈연소기에서 스월 인젝터의 분무특성에 관한 연구)

  • 이성혁;유홍선;이인섭;홍성국
    • Journal of the Korean Society of Safety
    • /
    • v.15 no.3
    • /
    • pp.30-39
    • /
    • 2000
  • The present paper deals with the numerical simulation for the spray characteristics with swirling turbulent flows and dilution flows from swirl injectors in a simplified can type of gas turbine combustor. The main objective is to investigate the characteristics of swirling turbulent flows with dilution flows and to provide the qualitative results for the spray characteristics such as the droplet distribution and Sauter Mean Diameter(SMD). The gas-phase equations based on Eulerian approach were discretized by Finite Volume Method, together with SIMPLE algorithm and the Reynolds -Stress-Model. The liquid-phase equations based on Lagrangian method were used to predict the droplet behavior. The results of preliminary test are generally in good agreement with experimental data, and show that the anisotropy exists in the primary zone due to swirl velocity and injected air from primary injector, and then gradually decays due to turbulent mixing and consequently near-isotropy occurs in the region between primary and dilution zones. For the spray characteristics, it is indicated that the swirling flows of primary jet region increase the droplet atomization. In addition, it is showed that the swirling flows at the inlet region lead the air-fuel mixture to be distributed near the igniter and can significantly affect the spray behavior in the primary jet region.

  • PDF

Computations of Droplet Impingement on Airfoils in Two-Phase Flow

  • Kim, Sang-Dug;Song, Dong-Joo
    • Journal of Mechanical Science and Technology
    • /
    • v.19 no.12
    • /
    • pp.2312-2320
    • /
    • 2005
  • The aerodynamic effects of leading-edge accretion can raise important safety concerns since the formulation of ice causes severe degradation in aerodynamic performance as compared with the clean airfoil. The objective of this study is to develop a numerical simulation strategy for predicting the particle trajectory around an MS-0317 airfoil in the test section of the NASA Glenn Icing Research Tunnel and to investigate the impingement characteristics of droplets on the airfoil surface. In particular, predictions of the mean velocity and turbulence diffusion using turbulent flow solver and Continuous Random Walk method were desired throughout this flow domain in order to investigate droplet dispersion. The collection efficiency distributions over the airfoil surface in simulations with different numbers of droplets, various integration time-steps and particle sizes were compared with experimental data. The large droplet impingement data indicated the trends in impingement characteristics with respect to particle size ; the maximum collection efficiency located at the upper surface near the leading edge, and the maximum value and total collection efficiency were increased as the particle size was increased. The extent of the area impinged on by particles also increased with the increment of the particle size, which is similar as compared with experimental data.

Study on Ammonia Uniformity and DeNOx Analysis in the Urea-SCR System for Construction Machinery (건설기계용 Urea-SCR 시스템의 촉매전단에서 암모니아 균질도 해석 및 DeNOx 성능에 관한 연구)

  • Kim, Donghwan;Park, Junkyu;Kang, Joung-ho;Moon, Seonjoon;Park, Sungwook
    • Journal of ILASS-Korea
    • /
    • v.24 no.2
    • /
    • pp.51-57
    • /
    • 2019
  • In this study, the spray atomization characteristics of urea injector used in SCR system for construction machinery was analyzed, and the uniformity index at the front of mixer and NOx conversion efficiency were evaluated through numerical analysis. Spray visualization and droplet size/velocity measurement were performed and the measured results were used to verify the spray analysis model to calculate the uniformity index in the exhaust gas after-treatment system. For the flow analysis, STAR-CCM, a three-dimensional CFD, was used and the uniformity index of the SCR system at the front of the mixer was calculated using the droplet dissociation model and the wall collision model. Finally, the DeNOx performance for the average condition of the NRTC driving mode was calculated to understand the NOx conversion efficiency reflecting the exhaust gas temperature. The simulation results show that the uniformity index at the front of mixer was calculated as 0.862 and DeNOx efficiency was 75.9%.