• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.436-444
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• 1998

Applicability of the RNG k-$\varepsilon$ model to the analysis of unsteady axisymmetric turbulent flow of a reciprocating engine including port/valve assembly is studied numerically. The governing equations based on non-orthogonal including port/valve assembly is studied numerically. The governing equations based on a non-orthogonal coordinate formulation with Cartesian velocity components are used and discretised by the finite volume method with non-staggered variable arrangements. The predicted results using the RNG k-$\varepsilon$ model of the unsteady axisymmetric turbulent flow within a cylinder of reciprocating model engine including port/valve assembly are compared to these from the modified k-$\varepsilon$ model and experimental data. Using the RNG k-$\varepsilon$ model seems the have some potential for the simulations of the unsteady turbulent flow within a port/valve-cylinder assembly over the modified k-$\varepsilon$model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.395-408
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• 1987

Turbulent flows in an axisymmetric reciprocating engine are numerically simulated at it's suction and compression stage. Amounts of heat transfer through the wall of the cylinder are also estimated. k-.epsilon. turbulence model is adopted and the law of the wall is applied at grid-points near the wall. More than 40 * 40 grids are reguried to reasonably predict flows and the 3-level finite difference scheme for the time derivative term appears to be effective rather than the 2-level scheme. Calculated mean velocity distributions shows good agreements with an available experimental data. The program reasonably simulates flow patterns and pressures throughout the suction and the compression stages of the reciprocating engine. Predicted intensities of turbulence are still deviated from measured data. Further researches for turbulence modeling are expected.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.41-51
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• 2001

Combustion characteristics of a KSR-III liquid rocket engine with split-triplet (F-O-O-F) type injector elements are investigated numerically from the viewpoints of engine performance and combustion flowfield. To evaluate numerical analysis of liquid rocket engine with radial type injector arrangement, 2-D axisymmetric and 3-D calculations are carried out and the prediction of engine performance for design and off-design conditions is in a good agreement with hot-firing tests. According to 2-D axisymmetric and 3-D calculations, the prediction error is 3∼5 % from the standpoint of performance. Numerical results of combustion characteristics calculated through 3-D analysis agree well with hot-firing tests qualitatively at injector plate. Decreasing impinging angle and changing radial type injector arrangement to H type injector arrangement reduce effectively local high-temperature region. Also, it is examined that those affect the performance seriously. In conclusion, it is revealed that both injector arrangement and impinging angle are critical parameters to affect the performance and combustion characteristics of the liquid rocket engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.1
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• pp.10-16
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• 2000

Spatially resolved liquid volume fractions from a set of line-of-sight laser diffraction measurements for axisymmetric sprays generated from a pintle-type gasoline injector have been tomographically reconstructed by Abel transformation, Fourier transformation and onion peeling method. Spatially resolved liquid volume fractions classified into 32 size groups were translated characteristics of SI engine fuel sprays. These data were also obtained from the phase Doppler measurements for the same sprays. The comparison between laser deffraction measurements and transformation reconstructs more reasonable spatially resolved characteristics for axisymmetric sprays as well as for asymmetric sprays.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.3
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• pp.29-36
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• 1989

A multidimensional numerical simulation for flows in an engine with axisymmetric geometry was performed. Three kinds of differencing schemes, namely, skew upwind differencing scheme (SUDS), interpolated upwind differencing scheme (IUDS), upwind differencing scheme (UDS), are used in a comparative study. Simultaneously, the effects of the artificial dampings and the grids on numerical results are estimated. Compared with the measurements, the calculations with SUDS and proper artificial damping show very similar qualitative tendency with observed results. But there are some discrepancies due to numerical errors and unclear boundary conditions.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.97-98
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• 1996

Variability of active galactic nuclei is now a well-known phenomenon. This remains to be fully explained by a theoretical model of the central engine. Time scales of AGN variability seem to range continuously from hours up to months. The short time scale variability must be related to the phenomena on the event horizon of the black hole, while the long one to those in the accretion disk or surrounding matter. Based on the axisymmetric, nonstationary model of the central engine, we discuss theoretical considerations on the variability of active galactic nucleus.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.92-100
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• 2000

One method to analyse acoustic modes is proposed to predict the characteristics of acoustic instability in liquid rocket engine. It is based on the similarity between transverse acoustic modes and adopts two-dimensional axisymmetric geometry. Using this method, the first tangential mode in the prototype combustor can be analysed through the analysis of the first radial mode in the model combustor with doubled chamber diameter. Sample numerical calculation is demonstrated applying this method to sample rocket engine and thereby acoustic instabilities of the engine are investigated. The present results show a good agreement with the previous findings. The numerical analysis based on the proposed method is cost-effective and serves as the first approximation to the true solution.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1744-1759
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• 1992

A multidimensional simulation of turbulent flow and combustion with swirl in the cylinder of SI engine is implemented to clarify the effects of swirl. present simulation employs the ICED-ALE numerical technique, the skew-upwind difference scheme, a modified k_.epsilon. turbulence model, a combustion model of Arrhenius type and turbulence-mixing-control type. First, the calculations for swirling flow in an axisymmetric cylinder are carried out. The results are compared with the experimental data to validate the numerical analysis. Second, the calculations for intake, compression and combustion processes in an axisymmetric cylinder are performed. The effects of swirl on turbulent flow and combustion are examined through the parametric study of swirl number 0.0, 0.6, 1.2 and 2.4. As a result, it is numerically shown that the turbulent kinetic energy and the swirl velocity, which are produced during the intake process, affect the combustion process.

• Journal of the Korean Society of Combustion
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• v.19 no.2
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• pp.1-7
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• 2014

In this study, the variation of the flow field in Hydro-reactive engine combustor was numerically studied through 2-dimensional axisymmetric model with aluminum and heated water vapor. For calculating all velocity fields, compressible Navier-Stokes equation was used with Pre-conditioning. AUSM+up(p) method was used to exactly calculate mass flow in the control volume. As using SST model that is a turbulent model, the result had high accuracy for free stream and the flow near the wall. The effects of the temperature, variation of the flow field and distribution of chemical products on inject angle of heated water vapor were studied.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.179-189
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• 1997

Among aftertreatment devices which reduce exhaust gas of diesel engine, diesel oxidation catalyst(DOC) with high reduction efficiency for gaseous matter and particulate matter is now studied actively. In this study, a transient one-dimensional model developed to simulate the thermal and conversion characteristics of adiabatic monolithic converters operating under warm up conditions is presented. This model takes into account the gas solid heat and mass transfer, axial heat conduction, chemical reactions and the related heat release. The model has been used to analyze the transient response of an axisymmetric catalytic converter during a warm-up as a function of catalyst design parameters and operation conditions in order to observe their effects on the lightoff behaviour. The experimental test was carried out 2400 cc light diesel engine with DOC.