• International Journal of Automotive Technology
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• 제7권2호
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• pp.129-137
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• 2006

The representative interactive flamelet(RIF) concept has been applied to numerically simulate the combustion processes and pollutant formation in the HSDI diesel engine. In order to account for the spatial inhomogeneity of the scalar dissipation rate, the eulerian particle flamelet model using the multiple flamelets has been employed. The vaporization effects on turbulence-chemistry interaction are included in the present RIF procedure. the results of numerical modeling using the rif concept are compared with experimental data and with numerical results of the widely-used ad-hoc combustion model. Numerical results indicate that the rif approach including the vaporization effect on turbulent spray combustion process successfully predicts the ignition delay characteristics as well as the pollutant formation in the HSDI diesel engines.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.267-268
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• 2015

The multi-environment probability density function model has been applied to simulate the turbulent $CH_4/H_2$ flames under MILD conditions. The direct quadrature method of moments (DQMOM) has been adopted to solve the transport PDF equation due to its computational efficiency and robustness. The IEM model represents the micromixing process. The numerical results obtained in this study are precisely compared with experimental data in terms of unconditional means and conditional means for scalar field including temperature and species mass fraction.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.327-330
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• 2006

기저연소과정이 포함된 젯추진을 고려한 기저유출 탄의 기저저항특성 조사를 위해 전산모사를 수행했다. 전반적인 유체역학과정은 2방정식의 $k-\omega$ SST난류 모델을 포함하고 반응유동을 위해 나비아-스토크방정식으로 모델화 되었다. 연소과정은 부분적으로 연소된 BBU (base-bleed unit) 출구조건을 갖는 유한속도반응으로 모델화 했다. 기저저항과 로켓플륨이 있는 기저유동의 상호작용에 대해 본 전산유체 해석기 능력을 보여주므로, 본 연구는 복합추진탄의 유체역학적 그리고 연소과정에 대한 이해를 준다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.349-352
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• 2008

This study has numerically modeled the combustion processes of the turbulent swirling premixed lifted syngas flames in the low-swirl burner (LSB). In these turbulent swirling premixed flames, the four tangentially-injected air jets induce the turbulent swirling flow which plays the crucial role of stabilizing the turbulent lifted flames. In the present approach, the turbulence-chemistry interaction is represented by the level-set based flamelet model. Numerical results indicate clearly that the present level-set based flamelet approach has realistically simulated the structure and stabilization mechanism of the turbulent swirling premixed lifted flames in the low-swirl burner. Computations are made for the wide range of the syngas chemical composition and the dilution level at two pressure conditions (1.0, 5.0 bar). Numerical results indicate that the lifted height in the LSB is increased by decreasing the H2 percentage and increasing the dilution level at the given equivalence ratio. It is also found that the flashback is occurred for the hydrogen composition higher than 80% at the equivalence ratio, 0.8. However, at the syngas composition range in the IGCC system, the stable lean-premixed lifted flames are formed at the low-swirl burner.

• 한국연소학회지
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• 제12권3호
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• pp.8-15
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• 2007

This study has numerically modelled the combustion processes of the turbulent swirling premixed lifted flames in the low-swirl burner (LSB). In these turbulent swirling premixed flames, the four tangentially-injected air jets induce the turbulent swirling flow which plays the crucial role to stabilize the turbulent lifted flame. In the present approach, the turbulence-chemistry interaction is represented by the level-set based flamelet model.. Two-dimensional and three-dimensional computations are made for the various swirl numbers and nozzle length. In terms of the centerline velocity profiles and flame liftoff heights, numerical results are compared with experimental data The three-dimensional approach yields the much better conformity with agreements with measurements without any analytic assumptions on the inlet swirl profiles, compared to the two-dimensional approach. Numerical clearly results indicate that the present level-set based flamelet approach has realistically simulated the. structure and stabilization mechanism of the turbulent swirling stoichiometric and lean-premixed lifted flames in the low-swirl burner.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.455-458
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• 2006

This study has numerically modelled the combustion processes of the turbulent swirling premixed lifted flames in the low-swirl burner (LSB). In these turbulent swirling premixed flames, the four tangentially- injected air jets induce the turbulent swirling flow which plays the crucial role to stabilize the turbulent lifted flame. In the present approach, the turbulence-chemistry interaction is represented by the level-set based flame let model. Two-dimensional and three-dimensional computations are made for the various swirl numbers and nozzle length. In terms of the centerline velocity profiles and flame liftoff heights, numerical results are compared with experimental data The three-dimensional approach yields the much better conformity with agreements with measurements without any analytic assumptions on the inlet swirl profiles, compared to the two-dimensional approach. Numerical clearly results indicate that the present level-set based flamelet approach has realistically simulated the structure and stabilization mechanism of the turbulent swirling stoichiometric and lean-premixed lifted flames in the low-swirl burner.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.233-239
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• 2003

본 연구는 고체 추진제 로켓 엔진의 연소과정을 수치적으로 해석하였다. 고체 추진제로는 double-base propellant를 이용하였으며 고체상에서는 2개의 포괄적인 반응식을 기체상에서는 5개의 포괄적인 반응식을 이용하였고 난류와 화학반응의 상호작용 PaSR(Partially Stirred Reactor)모델을 사용하였다. 고체 연료 벽면에서의 분출 효과로 야기되는 대류열전달의 불확실성을 줄이기 위하여 낮은 레이놀즈 수 k-$\varepsilon$난류모델을 적용하였다. 계산된 수치결과를 토대로 고체 추진제 로켓 엔진의 난류연소 과정 및 온도장과 압력장의 비정상 특성에 대하여 상세히 기술하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.31-34
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• 2012

케로신을 연료로 하는 동축 스월 분사기에 대해 정상 상태 및 비정상 상태의 연소 해석을 수행하였다. 난류연소 모델로 화학평형 상태로 가정하는 Non-premixed equilibrium 모델을 이용하였고, 고압의 조건에서 실제유체의 거동을 다룰 수 있도록 상태방정식으로 SRK(Soave-Redlich-Kwong) 상태방정식을 적용하였다. 해석을 통해 온도분포, OH 질량분율 등 정상 상태의 계산 결과와 시간 평균된 비정상 상태의 계산 결과를 비교하였고, 이들 간의 화염 구조가 서로 상이함을 확인할 수 있었다.

• 대한기계학회논문집B
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• 제41권8호
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• pp.553-561
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• 2017

본 연구에서는 산업용 가열 설비에 대한 연소 유동장과 복합 열전달 해석을 위하여 오픈소스 기반의 3차원 해석 시스템을 구축하고 실제 운전 중인 재가열로에 대한 해석을 통해 유용성을 확인하였다. 효율적인 가열로 전용 해석 체계를 위하여 오픈소스 OpenFOAM 라이브러리를 적용함으로써 다양한 해석 기능들을 추가로 개발할 수 있는 확장성과 상용 프로그램 도입에 비하여 경제성 측면에서도 장점들을 가지고 있다. 개발된 프로그램을 활용하여 실제 연속 아연 도금 강판 생산 공정 내의 수평형 소둔로에 대한 해석을 수행하였다. 해석 결과로부터 대상 가열 설비의 가열 성능은 고온 연소 기체에 의한 대류 보다는 복사 열전달 효과가 지배적이며, 이송되는 강판 표면으로 유입되는 복사 열전달량은 총 열전달량의 76% 수준으로 분석되었다. 현 가열로 전용 해석 시스템은 핵심적인 가열 설비 해석 기능을 포함하고 있지만, 다양한 연소 조건에 적용 가능한 난류 연소 모델과 가열로 벽면 열경계에 대한 추가적인 연구가 필요함을 확인하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.91-93
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• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.