• 한국추진공학회지
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• 제18권1호
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• pp.73-84
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• 2014

본 논문에서는 화학발광 계측을 통한 연소화염의 당량비, 열방출율과 같은 물리량 판단에 대한 최신 연구결과를 정리 분석하였다. 현대의 연소장치는 연소의 동적 안정성 증대 및 공해물질 배출억제를 위해 세밀한 제어가 필요하다. 화학발광 세기 계측을 통한 물리량 파악은 그 적용에 있어서 많은 상대적 장점을 지니고 있다. 그러나 본 방법은 당량비, 연소압력, 입구온도, 난류세기, 연료 종류 등에 의해 많은 영향을 받는다. 연구결과를 종합하면, 메탄/공기 예혼합 화염에서 $CH^*/OH^*$가 연료 과농 조건을 제외하고 당량비와 밀접한 관계가 있다. 또한 넓은 공간에서 측정된 $OH^*$, $CH^*$ 신호는 전체 열방출율과 비례관계를 갖는 것으로 판단된다.

• Journal of applied mathematics & informatics
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• 제9권1호
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• pp.213-230
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• 2002

We deal with the approximate controllability for semilinear systems with time delay in a Hilbert space. First, we show the existence and uniqueness of solutions of the given systems with the mere general Lipschitz continuity of nonlinear operator f from $R\;\times\;V$ to H. Thereafter, it is shown that the equivalence between the reachable set of the semilinear system and that of its corresponding linear system. Finally, we make a practical application of the conditions to the system with only discrete delay.

• Journal of Mechanical Science and Technology
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• 제18권2호
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• pp.325-334
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• 2004

Computational experiments on fundamental un stretched laminar burning velocities and flame response to stretch (represented by the Markstein number) of hydrogen-air flames at high temperatures and pressures were conducted in order to understand the dynamics of the flames including hydrogen as an attractive energy carrier in conditions encountered in practical applications such as internal combustion engines. Outwardly propagating spherical premixed flames were considered for a fuel-equivalence ratio of 0.6, pressures of 5 to 50 atm, and temperatures of 298 to 1000 K. For these conditions, ratios of unstretched-to-stretched laminar burning velocities varied linearly with flame stretch (represented by the Karlovitz number), similar to the flames at normal temperature and normal to moderately elevated pressures, implying that the "local conditions" hypothesis can be extended to the practical conditions. Increasing temperatures tended to reduce tendencies toward preferential-diffusion instability behavior (increasing the Markstein number) whereas increasing pressures tended to increase tendencies toward preferential-diffusion instability behavior (decreasing the Markstein number).

• 대한기계학회논문집
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• 제11권5호
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• pp.846-855
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• 1987

본 연구에서는 실용적 설계및 이론해석에 필요한 동적 거동에 관한 현상규명 및 기초자료를 제공하기위해, 기하학적 형상변화에 따른 맥동연소의 안정성 및 흡입공 기량의 측정을 통한당량비의 범위를 관찰하고, 연소실과 배기관, 공기유입관, 연료노 즐실에서의 압력을 각각 동시측정해서 동적거동에 관해 고찰하고, 작동주파수에 관한 간단한 실험식의 확립과 추력성능에 관한 실험을 행했다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.453-458
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• 2000

The paper describes a study of the variation of the NO production emitted from turbulent propane flames established on a practical combustor where a primary and a secondary fuel lines are installed. The flowrate of the secondary fuel is pulsated or added in addition to that of the primary fuel which constrantly flows to the nozzle of the burner. Two modes depending on the positions of supplying the secondary fuel are performed; one is for its position to be placed at the center of the primary fuel tube and the other around the stabilization baffle. The mean concentrations of gas species, $O_2,\;Co\;CO_2,\;NO$, and HC(unburnt hydrocarbones) have been measured at the exit of the combustor. As equivalence ration $({\Phi})$ is increased the profile of the NO concentration on the latter mode rises slowly less than that on the former one. In the range of ${\Phi}=0.5$ to 0.54 the NO production is reduced by about 35% more on the latter mode than on the former one. The influence of pulsating the secondary fuel on the variation of the NO concentration doesn't appear at both modes.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.692-697
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• 1994

In the actual sound environmental systems, it seems to be essentially difficult to exactly evaluate a whole probability distribution form of its response fluctuation, owing to various types of natural, social and human factors. Up to now, we very often reported two kinds of unified probability density expressions in the standard expansion from of Hermite and Laguerre type orthonormal series to generally evaluate non-Gaussian, non-linear correlation and/or non-stationary properties of the fluctuation phenomenon. However, in the real sound environment, there still remain many actual problems on the necessity of improving the above two standard type probability expressions for practical use. In this paper, first, a central point is focused on how to find a new probabilistic theory of practically evaluating the variety and complexity of the actual random fluctuations, especially through introducing some equivalence transformation toward two standard probability density expressions mentioned above in the expansion from of Hermite and Laguerre type orthonormal series. Then, the effectiveness of the proposed theory has been confirmed experimentally too by applying it to the actual problems on the response probability evaluation of various sound insulation systems in an acoustic room.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 추계 학술발표회
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• pp.291-311
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• 2006

The acceleration of consolidation by stone columns was mostly analysed within the framework of a basic unit cell model (i.e. a cylindrical soil body around a column). A method of converting the axisymmetric unit cell into the equivalent plane-strain model would be required for two-dimensional numerical modelling of multi-column field applications. This paper proposes two practical simplified conversion methods to obtain the equivalent plane-strain model of the unit cell, and investigates their applicability to multi-column reinforced ground. In the first conversion method, the soil permeability is matched according to an analytical equation, whereas in the second method, the column width is matched based on the equivalence of column area. The validity of these methods is tested by comparison with the numerical results of unit-cell simulations and with the field data from an embankment case history. The results show that for the case of linear-elastic material modelling, both methods produce reasonably accurate long-term consolidation settlements, whereas for the case of elasto-plastic material modelling, the second method is preferable as the first one gives erroneously lower long-term settlements, where plastic yielding of stone column are ignored.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2000년도 추계 학술발표회 논문집
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• pp.237-242
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• 2000

This study was carried out to optimize burner of the condensing gas boiler which can save energy by utilizing the latent heat of combustion gas and reduce pollutants emission. Three reasonable distances between burner and heat exchanger were decided through the experiments of model flat burner. The optimum burner geometry was determined from flame stability, pollutant emission characteristics and applicability to practical boiler system. The boiler designed by this research reaches turn-down ratio 5:1 in the domain of equivalence ratio 0.68∼0.85 and thermal efficiency of 98%. Emission of NOx and CO concentration was under 35ppm and 104ppm.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.906-912
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• 2000

In this study, for the use of LFG, the burning velocities of LFG and LFG mixed fuels have been numerically analyzed. C3 reaction mechanism which consists of 92 species and 621 reaction was adopted in the calculation. The results show that the burning velocities of LFG and LFG mixed fuels are obtained as a function of $CH_4$ and LFG percentage at stoichiometric conditions. In addition, the correlations of burning velocities LFG and LFG mixed fuels were obtained over a wide range of the equivalence ratio. The comparison of burning velocity correlated from numerically calculated results with experimental ones shows good agreements. From these results, the suggested burning velocity correlations far LFG and LFG mixed fuels in this study can be applied to the practical utilization of LFG.

• 한국자동차공학회논문집
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• 제4권1호
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• pp.229-237
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• 1996

For the practical use of a fuel injection system using solenoid, some mechanical and electrical problems should be explicitly analyzed. In our study, we have investigated these problems experimentally and have improved such that a solenoid driving circuit is liable to establish a fast reponse and a precise control of injection quantity. This proposed fuel injecton system is capable to control equivalence ratio from low level to high level. Therefore, we expect that this proposed system should be applicable to an actual engine.