• Title/Summary/Keyword: Mixing characteristics

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Recess Effects on Spray Characteristics of Swirl Coaxial Injectors

  • Seol, J.H.;Han, P.G.;Jeong, W.H.;Yoon, Y.
    • International Journal of Aeronautical and Space Sciences
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    • v.4 no.1
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    • pp.26-33
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    • 2003
  • Recess is a geometrical configuration shape that the exit surface of an inner injector is located at a certain length inward from that of an outer injector. It is known to have the characteristics that it can augment mixing efficiency and flame stabilization through internal mixing of propellant in it. So, various experiments, such as backlit stroboscopic photography, phase Doppler particle analyzer(PDPA) and mechanical patternator, were performed at several recess lengths to grasp its effect on the spray characteristics of spray angle, breakup length, atomization and' mixing. Recess length was normalized to dimensionless recess number and two principal mechanisms of impingement and swirl recovery were introduced to explain its influence on the spray characteristics. The effect of recess on SMD doesn't appear significantly near the recess number where mixing efficiency attains to the maximum, whereas mass distribution and mixing efficiency are changed considerably. Thus, it can be inferred that a certain optimum recess number exists, where mixing efficiency becomes the maximum.

Case Studies of Penetration Characteristics of DCM Wall Using Spiral Mixing Blades in Soil Layers (특수교반날개를 사용한 DCM 공법의 지반 관입 특성에 대한 사례연구)

  • Jung, Doo-Hoi;Jeong, Gyung-Hwan;Yang, Tae-Seon
    • Journal of the Korean Geotechnical Society
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    • v.23 no.3
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    • pp.133-140
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    • 2007
  • DCM (Deep Cement Mixing Method) has been applied to build structures such as self-supported earth retaining walls. DCM columns should be penetrability into the stiff layer to assure the self-supporting ability. On the penetration increase of blade attached to the DCM mixing tools, a spiral mixing blade has been revised. Penetration characteristics of spiral blades in the stiff soil layer were evaluated through Gimhae and Incheon areas. The spiral mixing blades could penetrate into the stiff soil layers which have the N-value of greater than 30 although the penetration rate is somewhat slow. Penetration characteristics and economical efficiency should be discussed to determine the critical depth of the spiral mixing blade because the penetration efficiency can decrease in the stiff layer in this paper.

Genetic Algorithms for Tire Mixing Process Scheduling (타이어 정련 공정 스케줄링을 위한 유전자 알고리즘)

  • Ahn, Euikoog;Park, Sang Chul
    • Korean Journal of Computational Design and Engineering
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    • v.18 no.2
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    • pp.129-137
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    • 2013
  • This paper proposed the scheduling method for tire mixing processes using the genetic algorithm. The characteristics of tire mixing process have the manufacturing routing, operation machine and operation time by compound types. Therefore, the production scheduling has to consider characteristics of the tire mixing process. For the reflection of the characteristics, we reviewed tire mixing processes. Also, this paper introduces the genetic algorithm using the crossover and elitist preserving selection strategy. Fitness is measured by the makespan. The proposed genetic algorithm has been implemented and tested with two examples. Experimental results showed that the proposed algorithm is superior to conventional heuristic algorithm.

A Study on the Flow Characteristics of Mixer by Impeller Types (임펠러 형상에 따른 교반기의 유동특성에 관한 연구)

  • 양창조;최민선;이영호
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.7
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    • pp.899-905
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    • 2003
  • Mixers are used in several industrial applications where it is necessary to strongly mix reactants in a short period of time (eg. reaction injection molding, ceramics manufacturing, crystallization). However, despite their widespread use, mixing flow characteristics in these systems have not been rigorously investigated. Influence of blade shapes on the mixing time and the power consumption per unit volume in two kinds of impeller including the mixing effects are studied by PIV experiment. A series of the experiments were carried out to achieve a better mixing effect in simple baffle arrangement and tall vessel with modified impellers(two kinds of blades : pitched blade turbine and rushton turbine). Results show that periodic vortex from the mixing layer is predominant and related unsteady flow characteristics prevail over the entire region.

Mixing Characteristics of Multiple Injection in Supersonic Flow (초음속 유동장 내 연료 다중 분사의 혼합 특성)

  • Lee Jong-Hwan;Lee Sang-Hyeon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.53-56
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    • 2004
  • The mixing characteristics of a multiple transverse injection system in a scramjet combustor were studied with numerical methods. The distance among injectors on mixing characteristics were investigated. The three-dimensional Wavier-Stokes equations including k-w SST turbulence model were solved. It was shown that the mixing characteristics of a multiple transverse injection system were very different from those of a single and a dual injection system; the rear injection flow was strongly influenced by blocking effect due to the momentum flux of the front injection flow and thus had higher expansion and penetration than the front injection flow. The multiple injection system had higher mixing rate, higher penetration but had more losses of stagnation pressure than the single injection system.

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Effect of Swirling Flow by Normal Injection of Secondary Air on the Gas Residence Time and Mixing Characteristics in a Lab-Scale Cold Model Combustor

  • Shin, D.;Park, S.;Jeon, B.;Yu, T.;Hwang, J.
    • Journal of Mechanical Science and Technology
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    • v.20 no.12
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    • pp.2284-2291
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    • 2006
  • The present study investigates gas residence time and mixing characteristics for various swirl numbers generated by injection of secondary air into a lab-scale cylindrical combustor. Fine dust particles and butane gas were injected into the test chamber to study the gas residence time and mixing characteristics, respectively. The mixing characteristics were evaluated by standard deviation value of trace gas concentration at different measurement points. The measurement points were located 25 mm above the secondary air injection position. The trace gas concentration was detected by a gas analyzer. The gas residence time was estimated by measuring the temporal pressure difference across a filter media where the particles were captured. The swirl number of 20 for secondary air injection angle of 5$^{\circ}$ gave the best condition: long gas residence time and good mixing performance. Numerical calculations were also carried out to study the physical meanings of the experimental results, which showed good agreement with numerical results.

CFD ANALYSIS FOR THERMAL MIXING CHARACTERISTICS OF A FLOW MIXING HEADER ASSEMBLY OF SMART (SMART 유동혼합헤더집합체 열혼합 특성 해석)

  • Kim, Y.I.;Bae, Y.M.;Chung, Y.J.;Kim, K.K.
    • Journal of computational fluids engineering
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    • v.20 no.1
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    • pp.84-91
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    • 2015
  • SMART adopts, very unique facility, an FMHA to enhance the thermal and flow mixing capability in abnormal conditions of some steam generators or reactor coolant pumps. The FMHA is important for enhancing thermal mixing of the core inlet flow during a transient and even during accidents, and thus it is essential that the thermal mixing characteristics of flow of the FMHA be understood. Investigations for the mixing characteristics of the FMHA had been performed by using experimental and CFD methods in KAERI. In this study, the temperature distribution at the core inlet region is investigated for several abnormal conditions of steam generators using the commercial code, FLUENT 12. Simulations are carried out with two kinds of FMHA shapes, different mesh resolutions, turbulence models, and steam generator conditions. The CFD results show that the temperature deviation at the core inlet reduces greatly for all turbulence models and steam generator conditions tested here, and the effect of mesh refinement on the temperature distribution at the core inlet is negligible. Even though the uniformity of FMHA outlet hole flow increases the thermal mixing, the temperature deviation at the core inlet is within an acceptable range. We numerically confirmed that the FMHA applied in SMART has an excellent mixing capability and all simulation cases tested here satisfies the design requirement for FMHA thermal mixing capability.

Numerical Study for Mixing Characteristics of an Oscillating Micro-stirrer (미소진동교반기의 혼합특성에 대한 수치적 연구)

  • Kim, Yong-Dae;Maeng, Joo-Sung
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.309-312
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    • 2006
  • Effective mixing is an important problem in microfluidics for chemical and biomechanical applications. In this study, the influences of the Reynolds number and the oscillating frequency on mixing characteristics of micro-stirrer are studied in a microchannel with single stirrer. The influence of fluid inertial effects in an active mixer is first discussed. It is found that the stirring effects by stirrer oscillation are promptly attenuated at low Reynolds number, which makes greatly difficult the rapid mixing. As the inertial effects are increased, the chaotic advection is generated and then developed. The mixing phase is finally developed some mushroom shaped structure. And the mixing efficiency is also studied as a function of the oscillating frequency. We found that the mixing efficiency does not always increase with higher oscillating frequency of stirrer. Consequently, we found the functional relation between the optimal frequency of a stirrer and the Reynolds number.

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Effect of burnt gas mixing on the extinction of interacting flames premixed (기연가스의 혼합이 상호작용을 하는 예혼합화염의 소화특성에 미치는 영향에 관한 연구)

  • 임홍근;정석호
    • Journal of the korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.37-48
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    • 1989
  • The effects of burnt gas mixing, which can be caused by turbulent eddy mixing, on the interaction and extinction characteristics of premixed flames are analyzed using large activation energy asymptotics adopting counterflow as a model problem. The results show that the burnt gas mixing, preferential diffusion and heat loss affect the fuel consumption rate, flame temperature and the oxidizer concentration at the flame which influence the flame behavior and the extinction characteristics.

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Pressure Loss and Heat Transfer Characteristics of Heat Exchanger Using Static Mixing Technology (정적혼합기술 응용 열교환기의 압력손실 및 열전달 특성)

  • Park Sang-Kyoo;Yang Hei-Cheon;Jeon Jun-Chul
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.1
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    • pp.65-72
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    • 2006
  • Heat transfer augmentation in heat exchangers has received much attention in recent years, mainly due to energy efficiency and environmental considerations. Many active and Passive techniques are currently being employed in heat exchangers, with some inserts providing a cost-effective and efficient means of augmenting heat transfer. The Purpose of this paper is to determine the pressure loss and heat transfer characteristics of a heat exchanger using static mixing technology. Experimental measurements were taken on two set-ups: a single tube heat exchanger and a shell-tube heat exchanger with two static mixing inserts. It was concluded that the static mixing inserts resulted in an increase in the pressure loss and heat transfer characteristics as can be expected.