• Journal of the Korean Society of Combustion
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• v.2 no.1
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• pp.17-27
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• 1997

It is well known that NOx formation has a strong dependence on the maximum temperature and correspondingly with the maximum chamber pressure of a closed combustion system. However, in a case of impinging-jet-flame (IJF hereafter) combustion with opposed dual pre-chambers, low $NO_x$ formation with high pressure could be achieved, but its mechanism has not been clearly understood so far. In this study, a three-dimensional analysis is adopted to resolve time-variant local properties that might indicate the mechanism of IJF combustion. Numerical results are verified by comparing them with experiments. The IJF combustion in a vessel with no pre-chamber, with single pre-chamber, and with dual pre-chambers is studied. The orifice diameter and the volumetric ratio of pre-chamber are used as geometric parameters. The effects of main-chamber ignition delay time and combustion time of main-chamber, orifice exit velocity, orifice exit temperature, turbulent kinetic energy of main-chamber and spatial distribution of temperature in the latter stage of combustion are investigated. A longer main-chamber ignition delay and a shorter main-chamber combustion time suppress the formation of high temperature region with respect to mean temperature, which consequently results in less NO production.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.46-53
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• 2017

This paper deals with an acoustic model for a lean premixed gas turbine combustor composed of three stages: premixing chamber, nozzle and flame tube. Our model is given as an acoustic transfer function whose input is a heat release rate perturbation and output is a velocity perturbation at a flame location. We have shown that the resonance frequencies are functions of three round-trip frequencies of acoustic wave in each stage, and area ratios between stages. By analyzing poles of the acoustic transfer function, we could characterize resonant frequencies and their dependency on various system parameters of a combustor. It was found that our analytic findings match with existing numerical and experimental results in literature.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.764-769
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• 2001

Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutant emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle. Basically, a mixed flow of gas and particle in coal nozzle is required to have appropriate injection and concentration distribution at exit to achieve flame stability and low pollutant, but it is very difficult to obtain that without help of a coal separating device within nozzle. In this study, each distribution of air and coal flow rate is measured for the coal nozzle with coal separator developed by us. The coal concentration at exit is various according to inlet swirl values and positions of coal separator. Also pressure drop is measured for various operating conditions of this nozzle. From these results, we can find the separation characteristic of new developed coal separator, and select proper operation range of coal nozzle. When this coal nozzle is applied to actual plant, these investigations will be very useful to confirm the shape of coal separator to have efficient particle injection.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.1
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• pp.26-33
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• 2007

The intake swirl motion, as one of dominant effects for an engine combustion. is very effective for turbulence enhancement during the compression process in the cylinder of 2-valve engine. Because the combustion flame speed is determined by the turbulence that is mainly generated from the mean flow of the charge air motion in intake port system. This paper describes the experimental results of swirl flow and combustion characteristics by using the oil spot method and back-scattering Laser Doppler velocimeter (LDV) in 2-valve single cylinder transparent LPG engine using the liquid phase LPG injection. For this. various intake port configurations were developed by using the flow box system and swirl ratios for different intake port configurations were determined by impulse swirl meter in a steady flow rig test. And the effects of intake swirl ratio on combustion characteristics in an LPG engine were analyzed with some analysis parameters that is swirl ratio. mean flow coefficient, swirl mean velocity fuel conversion efficiency. combustion duration and cyclic variations of indicated mean effective pressure(IMEP). As these research results, we found that the intake port configuration with swirl ratio of 2.0 that has a reasonable lean combustion stability is very suitable to an $11{\ell}$ heavy-duty LPG engine with liquid phase fuel injection system. It also has a better mean flow coefficient of 0.34 to develope a stable flame kernel and to produce high performance. This research expects to clarify major factor that effects on the design of intake port efficiently with the optimized swirl ratio for the heavy duty LPG engine.

• Fire Science and Engineering
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• v.30 no.6
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• pp.92-98
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• 2016

This study evaluated thermal image real-time estimation and fire alarm using by a CCD camera, which has been a seamless feature-point analysis method, according to the angle and position and image fusion by a vector coordinate point set-up of equal shape. The system has higher accuracy, fixing data value of temperature sensing and fire image of 0~255, and sensor output-value of 0~5,000. The operation time of a flame specimen within 500 m, 1000 m, and 1500 m from the test report specimen took 7 s, 26 s, and 62 s, respectively, and image creation was proven. A diagnosis of fire accident was designated to 3 steps: Caution/Alarm/Fire. Therefore, a series of process and the transmission of SNS were identified. A light bulb and fluorescent bulb were also tested for a false alarm test, but no false alarm occurred. The possibility that an unwanted alarm will be reduced was verified through a forecast of the fire progress or real-time estimation of a thermal image by the change in the image of a time-based flame and an analysis of the diffusion velocity.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.2
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• pp.102-106
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• 2016

An experimental study on the flow characteristics under various laminar coflow diffusion flames was conducted with a particular focus on the buoyancy force exerted from gaseous hydrocarbon fuels. Methane ($CH_4$), ethylene ($C_2H_4$), and n-butane ($C_4H_{10}$) were used as the fuels. A coflow burner and the Schlieren imaging technique were used to observe the flow field of each fuel near the nozzle exit as well as the flow characteristics in the flames. The results show that a vortex with a density heavier than air appeared in n-butane near the nozzle exit with a strong negative buoyancy on the fuel steam. As the Reynolds number increased through the control of the fuel velocity of the n-butane flame, the vortices were greater and the vortex tips were moved up from the nozzle exit. In addition, the heated nozzle affected the flow fields of the fuel steam near the nozzle exit.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.17-22
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• 2017

An experimental study has been conducted to elucidate the effect of AC electric field on behaviors of laminar lifted flame in nitrogen-diluted methane coflow-jets. Our concerns are focued on the regime to show a decrease in liftoff height, $H_L$ with increasing nozzle exit velocity, $U_O$ (hereafter, $decreasing-H_L$). The $H_L$ with $U_O$ near flame extinction were measured by varying the applied AC voltage, $V_{AC}$ and frequency, $f_{AC}$ in a single electrode configuration. The behavior of $H_L$ with a functional dependency of $V_{AC}$ and $f_{AC}$ was categorized into two regime : (I) $H_L$ decreased for nozzle diameter, D = 1.0 mm, and (II) $H_L$ increased in the increase of $f_{AC}$ for a fixed $V_{AC}$ in a D = 4.0, 8.4 mm. The lifted flames in $decreasing-H_L$ region was unstable in high voltage regimes while the $H_L$ showed a decreasing tendency with $U_O$ except them. Such behaviors in $H_L$ were also characterized by functional dependencies of related physical parameters such as $V_{AC}$, $f_{AC}$, $U_O$, fuel mole fraction ($X_{F.O}$) and D.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.67-74
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• 2013

A jet in a crossflow (JICF) has been extensively studied because of its wide applications in technological systems, including fuel injection into a ram-combustor. However, in the case of insufficient mixing performance of the liquid jet into the crossflow, the flame in a ram-combustor is unstable. In this study, the nonuniform flame and combustion instabilities due to lack of mixing performance were experimentally investigated. By performing correlations to predict the penetration height and break-up point, the spray and mixing characteristics of JICF have been studied. In particular, the improved correlations of penetration height are proposed in two distinctive domains depending on the X/d location of the crossflow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.51-57
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• 2013

This study aims to experimentally investigate the combustion characteristics of a lean premixed swirl-stabilized burner with dual-stage fuel injection arrays. The results show that a variation in the fuel distribution to fuel stages 1 (upstream) and 2 (downstream) produces a noticeable change in the NOx and CO emissions. Reducing the confined ratio, defined as the ratio of the nozzle exit diameter to the liner diameter, may reduce NOx and CO emissions owing to reduced combustion loading and longer residence time, respectively. A nozzle exit velocity of 30 m/s shows the optimum characteristics in terms of NOx and CO emissions and flame stability: increasing or decreasing the nozzle exit velocity leads to a degradation in emissions or flame stability, respectively.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.7-14
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• 2011

Using 20 L spherical explosion vessel and differential scanning calorimeter (DSC), an experimental investigation was carried on explosion characteristics and thermal decomposition of some reactive organic dust. As the result, the minimum explosion concentration of Benzoyl peroxide (BPO), Phthalic anhydride (PA) and 1-Hydroxybenzotriazol (HBT) exist between 10 and 15 g/$m^3$, which indicates that their explosion sensitivity are high. The maximum Kst values of HBT, PA and 97 % BPO are 251, 146 and 80 [$bar{\cdot}m/s$], respectively and the explosion severity of HBT is the explosion class of St-2. The flame velocity was also calculated from the combustion time of dust and flame arrival time to estimate the flame propagation characteristics in a closed vessel. The decomposition temperature and heat of decomposition reaction for 97 % BPO and HBT are $107^{\circ}C$ (1025 J/g), $214^{\circ}C$ (1666 J/g), respectively and it was found that these low decomposition temperature and high released heat affect the explosion characteristics.