• Title/Summary/Keyword: Turbulent Flame Speed

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Numerical Simulation of Chemically Reacting Laminar and Thrbulent Flowfields Using Preconditioning Scheme (예조건화 기법을 이용한 층류 및 난류 화학반응 유동장 해석)

  • Kim Gyo-Soon;Choi Yun-Ho;Rhee Byung-Ohk;Song Bong-Ha
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.4 s.247
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    • pp.320-327
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    • 2006
  • The computations of chemically reacting laminar and turbulent flows are performed using the preconditioned Navier-Stokes solver coupled with turbulent transport and multi-species equations. A low-Reynolds number $k-\varepsilon$ turbulence model proposed by Chien is used. The presence of the turbulent kinetic energy tenn in the momentum equation can materially affect the overall stability of the fluids-turbulence system. Because of this coupling effect, a fully coupled formulation is desirable and this approach is taken in the present study. Choi and Merkle's preconditioning technique is used to overcome the convergence difficulties occurred at low speed flows. The numerical scheme used for the present study is based on the implicit upwind ADI algorithm and is validated through the comparisons of computational and experimental results for laminar methane-air diffusion flame and $ H_2/O_2$ reacting turbulent shear flow. Preconditioning formulation shows better convergence characteristics than that of non-preconditioned system by approximately five times as much.

A Study on Block from Spread of Fire of the Exteriors Installation Space (외장재 설치 공간의 화재확산 차단에 관한 연구)

  • Min, Se-Hong;Yun, Jung-Eun;Kim, Mi-Suk
    • Journal of the Korea Safety Management & Science
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    • v.14 no.2
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    • pp.83-89
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    • 2012
  • In this study, FDS fire simulation experiments and measured wind speed by applying the exterior installation portion for blocking the spread of the fire was investigated. As a result, aluminum composite panels installed in the lower and the upper part of the panel to remove all the lower side, and then the maximum wind speed 0.24 m/s and the upper side 0.58 m/s were measured. In the FDS, the measured wind speed difference air currents are approximately 3.7 times in 12 seconds, the occurrence of 17 seconds early moment wind 2.2 m/s was measured from. Before and after the fire occurred in early of the air velocity about 39 seconds was 3.5 times difference. Such air currents caused by the temperature of the building but also by the building height was found. Turbulent flame of fire by expanding the vertical extent of damage become greatly important factor. Therefore, through the exterior installation portion of the block that can delay the spread of fire is expected that this should be taken.

A study on the spray combustion characteristics in a cylinder of a D.I.diesel engine with the electronically controlled injector (전자제어식 직접분사 디젤 엔진 연소실내의 분무연소 특성에 관한 연구)

  • 정재우;김성중;이기형;선우명호
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.2
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    • pp.50-56
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    • 2000
  • It is well known that the combustion phenomenon of diesel engine is an unsteady turbulent diffusion combustion. Therefore, the combustion performance of diesel engine is related to a complex phenomenon which involves the various factors of combustion, such as a injection pressure, injection timing, injection rate, and operation conditions of engine. In this study, the spray and the flame development processes in a single cylinder D.I. diesel visualization engine which uses the electronically controlled injection system were visualized to interpret the complicated combustion phenomenon by using high speed CCD camera. In addition, the cylinder pressure and heat release rate were also obtained in order to analyze the diesel combustion characteristics under several engine conditions.

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Numerical Simulation for Model Gas Turbine Combustor (모형 가스터빈 연소기의 수치해석적 연구)

  • 김태한;최병륜
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.7
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    • pp.1789-1798
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    • 1994
  • This paper aimed for numerical simulation of complicated gas turbine combustor with swirler. For the convenience of numerical analysis, fuel nozzle and air linear hole areas of secondary and dilution zone, which are issued to jet stream, were simplified to equivalent areas of annular type. In other to solve these problems, imaginary source terms which are corresponded to supplied fuel amount were added to those of governing equation. Chemical equilibrium model of infinite reaction rate and $k-{\epsilon}-g$ model with the consideration of density fluctuation were applied. As the result, swirl intensity contributed to mixing of supplied fuel and air, and to speed up the flame velocity than no swirl condition. Temperature profiles were higher than experimental results at the upstream and lower at the downstream, but total energy balance was accomplished. As these properties showed the similar trend qualitatively, simplified simulation method was worth to apply to complicated combustor for predicting combustion characteristics.

A Unified 3D Numerical Analysis of a Model Scramjet Engine with a Cavity Flame-Holder and Two Intake Side Walls (공동형 보염기를 갖는 모델 스크램제트 엔진의 흡입구 측면효과를 고려한 3차원 통합 유동해석)

  • Yeom, Hyo-Won;Kim, Sung-Jin;Sung, Hong-Gye;Kang, Sang-Hoon;Yang, Soo-Suk
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.590-593
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    • 2009
  • To identify the detailed 3D flow characteristics of a model scramjet engine, a unified 3D numerical analysis was performed. The numerical domain of concern includes the entire flow path of the model scramjet engine extending from the intake to the nozzle exhaust. Turbulent models($k-{\omega}$ SST and low Reynolds number k-e with Sarkar model) were applied with comparison of experiment result. Intake side wall's effect on flow characteristics was analyzed in view points of flow quality at inlet duct and near the flame holder as well. The code is paralleled with multi-block feature using MPI(Massage Passing Interface) library to speed up the 3D calculation.

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An Experimental Study for the Effect of Intake Port Flows on the Tumble Generation and Breakdown in a Motored Engine (모터링엔진의 흡기포트 유동변화에 따른 텀블생성 및 소멸에 관한 실험적 연구)

  • 강건용;이진욱;정석용;백제현
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.4
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    • pp.912-919
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    • 1994
  • The engine combustion is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake stroke breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of this relationship is not well known. This paper describes the tumble flow measurements inside the cylinder of a 4-valve S.I. engine using laser Doppler velocimetry(LDV) under motoring(non-firing) conditions. This is conducted on an optically assesed single cylinder research engine under motored conditions at an engine speed of 1000rpm. Three different cylinder head intake port configurations are studied to develop a better understanding the tumble flow generation, development, and breakdown mechanisms.

Influence of Mixture Non-uniformity on Methane Explosion Characteristics in a Horizontal Duct (수평 배관의 메탄 폭발특성에 있어서 불균일성 혼합기의 영향)

  • Ou-Sup Han;Yi-Rac Choi;HyeongHk Kim;JinHo Lim
    • Korean Chemical Engineering Research
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    • v.62 no.1
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    • pp.27-35
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    • 2024
  • Fuel gases such as methane and propane are used in explosion hazardous area of domestic plants and can form non-uniform mixtures with the influence of process conditions due to leakage. The fire-explosion risk assessment using literature data measured under uniform mixtures, damage prediction can be obtained the different results from actual explosion accidents by gas leaks. An explosion characteristics such as explosion pressure and flame velocity of non-uniform gas mixtures with concentration change similar to that of facility leak were examined. The experiments were conducted in a closed 0.82 m long stainless steel duct with observation recorded by color high speed camera and piezo pressure sensor. Also we proposed the quantification method of non-uniform mixtures from a regression analysis model on the change of concentration difference with time in explosion duct. For the non-uniform condition of this study, the area of flame surface enlarged with increasing the concentration non-uniform in the flame propagation of methane and was similar to the wrinkled flame structure existing in a turbulent flame. The time to peak pressure of methane decreased as the non-uniform increased and the explosion pressure increased with increasing the non-uniform. The ranges of KG (Deflagration index) of methane with the concentration non-uniform were 1.30 to 1.58 [MPa·m/s] and the increase rate of KG was 17.7% in methane with changing from uniform to non-uniform.

A Study on Concurrent Fire Appearance through Openings (개구부를 통한 동시다발적인 화재성상에 관한 연구)

  • Min, Se-Hong;Lee, Jae-Moon
    • Fire Science and Engineering
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    • v.26 no.2
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    • pp.90-96
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    • 2012
  • Since vertical flame spread speed on exterior materials is much faster than horizontal fire, analysis of its fire characteristic is required. For the study of vertical fire pattern created by penetrating windows or openings from the exterior wall of buildings, the research is based on the fire simulation for an aluminum-complex-panel with which is commonly used as exterior materials and consists of polyethylene core material. As a result, the flame reaches the 2nd floor after 135 seconds in the early stage of fire, the 10the floor after 470 seconds and the 30th floor, the highest floor, after 711 seconds. The result shows that fire spread abruptly expands on upper floor due to stack effect of a turbulent flow or exterior materials. In consequence, we can confirm a serious problem that a conflagration of a building through an opening that is equipped with the exterior-materials spreads into interior of building at that same time.

The Effect of Intake Port Configurations on the Turbulence Characteristics During Compression Stroke in a Motored Engine (흡입포트형상에 따른 모터링엔진내 압축과정 난류특성 연구)

  • 강건용;이진욱;정석용;백제현
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.4
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    • pp.920-932
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    • 1994
  • The combustion phenomena of a reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. This paper describes cycle resolved LDV measurement of turbulent flow inside the cylinder of a 4-valve engine under motoring(non-firing) conditions, and studies the effect of intake port configurations on the turbulence characteristics using following parameters ; Eulerian temporal autocorrelation coefficient, turbulence energy spectral density function, Taylor micro time scale, integral time scale, and integral length scale.

The Behavior of Impinging Spray by Piston Cavity Geometry (PistonCavity 형상에 따른 충돌분류의 분무거동)

  • 이상석;김근민;김봉곤;정성식;하종률
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.3
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    • pp.211-219
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    • 1996
  • In a small high-speed D. I. diesel engine, the injected fuel spray into the atmosphere of the high temperature is burnt by go through the process of break up, atomization, evaporation and process of ignition. These process are important to decide the emission control and the rate of fuel consumption and out put of power. Especially, in the case of injected fuel spray impinging on the wall of piston cavity, the geometry of piston cavity gives great influence the ignitability of injected fuel and the flame structure. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, the spray was impinged on the wall of 3 types of piston cavity such as Dish, Toroidal, Re-entrant type, in order to analyze the combustion process of impinging spray precisely and systematically. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation σ(t) and variation factor(vf) was measured with the lapse of time.

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