• Transactions of the Korean Society of Mechanical Engineers B
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• 제25권10호
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• pp.1303-1310
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• 2001

In order to be applicable to the combustion modelling of stratified charged combustion like that of - lean burn and GDI engine, the correlations of laminar burring velocities fur several hydrocarbon fuels and methanol are needed over a wide range of equivalence ratio, pressure and temperature. In this study, these correlations are modeled in the 1311owing form based on the experimental and Muller\`s modeling results for several fuels, where $\alpha$, ξ, and ξ are functions of pressure and temperature, $S_{L}$ =$\alpha$ exp[-ξ($\Phi$-$\Phi$$_{m}$)$^{2}$ -exp {-ζ($\Phi$-$\Phi$$_{m}$)}-ζ($\Phi$-$\Phi$$_{m}$)]. By using the results calculated by PREMIX code with Sloane\`s detailed chemical reaction mechanism for propane, it is verified that the coefficients of the abode modeling can be determined by considering laminar burning velocity data only in a range of equivalence ratio less than $\Phi$$_{m}$. Therefore, Muller\`s modeling results can be adopted leer modeling of the pressure and temperature dependency. Compared with the results of the existing Keck'and Gulder's models, those of the present one showed the good agreement of the recent experimental data, especially in the range of lean and rich sides.s.des.s.

• Proceedings of the Korean Ceranic Society Conference
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.53.2-53
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• 2003

• Journal of the Korean Society of Combustion
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• 제13권1호
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• pp.17-22
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• 2008

A partly implicit/quasi-explicit method is introduced for the solution of detailed chemical kinetics with stiff source terms based on the standard fourth-order Runge-Kutta scheme. Present method solves implicitly only the stiff reaction rate equations, whereas the others explicitly. The stiff equations are selected based on the survey of the chemical Jaconian matrix and its Eigenvalues. As an application of the present method constant pressure combustion was analyzed by a detailed mechanism of hydrogen-air combustion with NOx chemistry. The sensitivity analysis reveals that only the 4 species in NOx chemistry has strong stiffness and should be solved implicitly among the 13 species. The implicit solution of the 4 species successfully predicts the entire process with same accuracy and efficiency at half the price.

• Journal of the Korean Society of Combustion
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• 제17권4호
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• pp.44-50
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• 2012

The present study was conducted to investigate the flame instability(evaluated by Markstein length and cellular instability) and laminar burning velocity in a constant volume combustion chamber at room temperature and elevated pressure up to 0.3 MPa to suggest the possibility of utilizing mixtures of syngas added DME-air premixed flames in internal combustion engines. The experimentally measured laminar burning velocities were compared to predictions calculated the PREMIX code with Zhao reaction mechanism. Discussions were made on effects of syngas addition into DME-Air premixed flames through evaluating laminar burning velocity, Markstein length, and cellular instability. Particular concerns are focused on cellular instability caused by hydrodynamic instability and diffusive-thermal instability.

• Journal of the Korean Society of Propulsion Engineers
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• 제4권2호
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• pp.12-20
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• 2000

The numerical analysis, including chemical reaction of an entire ramjet engine is studied to understand the ignition transient mechanism and the dynamic characteristics of the Integrated Rocket Ramjet System comprehensively. Details of how a subsonic combustion environment is established from the supersonic ram air after removal of the inlet port cover, are examined during the ignition transient. Various physical processes are investigated systemically, including ignition, flame propagation, flame dynamics, and vorticity evolution.

• Journal of the Korean Society of Combustion
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• 제4권1호
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• pp.27-38
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• 1999

We constructed a wire-cylinder type pulsed corona discharge system for $NO_x$ removal, which was operated in room temperature. A emission spectrometer was built with a boxcar averager and monochrometer equipped with photo-multiplier tube detector. The sensitivity of the emission spectrometer was greatly improved by synchronizing the emission spectrometer with pulsed corona discharge system using a triggered spark-gap switch. $N_2$ spectrum($c^3{\Pi}_u{\rightarrow}X^1{\Sigma}_g{^+}$) was measured in the range of 300 - 450 nm and oxidizing OH radical emission($A^2{\Sigma}^+{\rightarrow}X^2{\Pi}$) was measured in case $N_2$ was supplied with water bubbling. As wet gas composition of inlet $N_2$ supplied in the discharge system increased, the intensity of OH emission was increased and saturated at wet gas composition 50%. We also investigated additive effect of $C_2H_4,\;H_2O,\;H_2O_2$ on the intensity of OR emission and $NO/NO_2/NO_x$ reduction and analysed the related reaction mechanism in corona discharge process. $H_2O_2$ additive increased the intensity of OH emission and $NO/NO_x$ reduction.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.49-56
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• 2003

Mathematical formulation of the zone conditional two-fluid model is established to consider flame-generated turbulence in premixed turbulent combustion. The conditional statistics of major flow variables are investigated to understand the mechanism of flame generated turbulence. The flow field in burned zone shows substantially increased turbulent kinetic energy, which is highly anisotropic due to reaction kinematics across thin flamelets. The transverse component of rms velocities in burned zone become larger than axial component in the core of turbulent flame brush. The major source or sink terms of turbulent kinetic energy are the interfacial transfer by the mean reaction rate and the work terms by fluctuating pressure and velocity on a flame surface.

• Transactions of the Korean Society of Automotive Engineers
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• 제6권4호
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• pp.166-177
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• 1998

Combustion characteristics of natural gas premixed flames is studied experimently and numerically by adopting a counterflow as a flamelet model in turbulent flames. Flame speeds are measured by employing LDV, and the results show that flame speed increases linearly with strain rate, which agrees well with numerical results. Parametric dependences of extinction strain rates are studied numerically with detailed kinetic mechanism to show that the addition of ethand to a methane premixed flame makes the flame more resistant to strain rate. The effect of pressure on the extinction strain rate is that the extinction strain rate increases up to 10 atm and them decreases, which is explained by competition of chain branching H+O2=OH+O and recombination reaction H+O2+M=HO2+M. Detailed mechanism having seventy-four step is systematically reduced to a nine-step and a five-step thermal NOx chemistry is reduced to two-step. Comparison between the results of the detailed and the reduced mechanisms demonstrates that the reduced mechanism successfully describes the essential features of natural gas premixed flames including extinction strain rate and NOx production.

• Journal of the Korean Society of Combustion
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• 제4권2호
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• pp.63-74
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• 1999

The effects of EGR and premixedness on NO formation have been numerically investigated. The flame structure is classified into three categories; premixed flame($=1)$, rich/lean premixed flame(${\alpha}=0.6$ and 0.8) and diffusion flame(${\alpha}=0$). NO formation/destruction mechanisms are assorted to thermal, reburn and Fenimore mechanisms. The temperature of unburned gas is arranged to 298 and 500 K to have access to the condition in a real internal combustion engine. The results show that all three NO formation/destruction reaction rates in the fuel rich flame zone could be decreased by EGR for rich/lean premixed flames, while those in the fuel lean flame zone are not significantly changed. Near the stagnation plane, however, only the thermal NO reaction rate is decreased. The contribution of reburn and Fenimore mechanisms for the net NO production becomes less significant as the premixedness of a flame increases. The larger amount of NO reduction with EGR is expected under the higher temperature and/or higher fuel/air premixedness conditions due to the increased contribution of the thermal mechanism. The role of Fenimore and reburn mechanisms could be important for rich premixed and diffusion flames; therefore, the effect of EGR on NO reduction could vary with fuel/air premixedness. The premixedness of a partially premixed flame changes the flame structure and could affect the NO production characteristics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.233-239
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• 2003

The present study has numerically investigated the combustion processes in the solid propellant rocket engine. The two step global reaction model for condensed phase and five step global reaction mechanism for gas phase are adopted to predict the detailed flame structure near double-base solid propellant surface. The turbulence-chemistry interaction is represented by the PaSR(Partially Stirred Reactor) model. To reduce the uncertainties for convective heat transfer near solid fuel surface having strong blowing effect, the Low Reynolds number k-$\varepsilon$ turbulent model is employed. Based on numerical results, the detailed discussion has been made for the turbulent combustion processes and transient behavior of pressure and temperature fields in the solid propellant rocket engine.