• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.119-126
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• 2004

In order to elucidate the modes of double-droplet combustion speed in premixed spray flame, the difference between flame propagation speed and droplet cluster disappearance speed are experimentally investigated using a premixed spray burner system, It was confirmed that flame speed concerned with premixed-mode combustion in the spray flame was approximately 2.0 m/s in average while mean disappearance speed of droplet clusters, which were dominated by diffusion-mode combustion in downstream of the flame, was evaluated as much as 0.45 m/s. It was clarified that both characteristics of premixed-mode and diffusion-mode combustion in spray flames are of much difference in nature, even though both speed, which are supposed to depend on local properties of the spray itself and flow conditions surrounding droplet clusters, are scattered in experiments.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.9-23
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• 1995

To analyze the spray and flame in D.I. diesel engine, the visualizing methods by schlieren photograph and diffused background illumination photograph with high speed camera are applied to optically accessible D.I.diesel engine. Wcaporating spray, spray droplets and brightness flame are taken with high speed camera by visuallizing method in accordance with various suction air temperature and injection time. The spray and flame image on the film was analyzed by image analyzer. The optically accessible D.I. diesel engine had the similar pressure characteristic to the real D.I. diesel engine. Experimental results showed that shadow areas of the evaporating spray were extended at higher suction air temperature, spray droplets had a max. Penetration length and their penetrating patterns were dependent on the surrounding gas temperature, and flame size after ignition was largely governed by the evaporated fuel quantity at ignition point and by the surrounding gas condition due to piston motion.

• Journal of ILASS-Korea
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• v.7 no.2
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• pp.1-6
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• 2002

It is necessary to develope a high frequency diode laser sensor system based on the absorption spectroscopy for the measurement of temperature of the spray flame. DFB diode laser operating near $2.0{\mu}m$ was used to scan over selected $H_2O$ transitions near $1.9{\mu}m\;and\;2.2{\mu}m$, respectively. The measurement sensitivity at wide range of sweep frequency was evaluated using multi-pass cell containing $CO_2$ gas. This diode laser absorption sensor with high temporal resolution up to 10kHz was applied to measure the gas temperature in the spray flame region of liquid-gas 2-phase counter flow flame. The successful demonstration of time series temperature measurement in the spray flame gives us motivation of trying to establish non-intrusive temperature measurement method in the practical spray flame.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.201-209
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• 1984

In order to examine the effect of initial spray condition on the spray combustion mode and flame characteristics, theoretical analysis was carried out to predict combustion mode and flame structure for various initial distribution of droplets in spray. A system of conservation equations of spray flame in two dimensional axisymmetric for two phase flow was solved by a discrete element method for n-Butylbenzen (C$_{10}$ $H_{14}$). As a results of present study, there are two principal group combustion modes that may occur independently for various initial group combustion numbers in a spray burner. These group combustion modes are termed as an external and internal group combustion mode. The critical group combustion number between the internal and external group combustion mode and the flame characteristics of those flame are also predicted. These results may be used as a basic data in the designing of new combustors as well as proper operating conditions for spray burners.s.

• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.2058-2065
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• 2004

A light collecting probe named Multi-color Integrated Cassegrain Receiving Optics (MICRO) is applied to spark-ignited spherical spray flames to obtain the flame propagation speed in freely falling droplet suspension produced by an ultrasonic atomizer. Two MICRO probes are used to monitor time-series signals of OH chemiluminescence from two different locations in the flame. By detecting the arrival time difference of the propagating flame front, the flame propagation speed is calculated with a two-point delay-time method. In addition, time-series images of OH chemiluminescence are simultaneously obtained by a high-speed digital CCD camera to ensure the validity of the two-point delay-time method by the MICRO system. Furthermore, the relationship between the spray properties measured by phase Doppler anemometer (PDA) and the flame propagation speed are discussed with three different experimental conditions by changing the fuel injection rate. It was confirmed that the two-point delay-time method with two MICRO probes is useful and convenient to obtain the flame propagation speed and that the flame propagation speed depends on the spray properties.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.20-25
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• 2004

In order to obtain the flame Propagation speed in freely falling droplet suspension Produced by an ultrasonic atomizer, a light collecting probe named Multi-color Integrated Cassegrain Receiving Optics (MICRO) is applied to spark-ignited spherical spray flames. Two MICRO probes are used to monitor time-series signals of OH chemilumine-scence from two different locations in the flame. The flame propagation speed is calculated by detecting the arrival time difference of the propagating flame front. In addition, time-series images of OH chemiluminescence are simultaneously obtained by a high-speed digital CCD camera to ensure the validity of the MICRO system. Furthermore, relationship between the spray properties measured by phase Doppler anemometer (PDA) and the flame propagation speed are discussed with k different experimental conditions by changing the fuel injection rate. It was confirmed that the MICRO probe system was very useful and convenient to obtain the flame propagation speed and that the flame propagation speed was different depending on the spray properties.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.509-510
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• 2006

Correlations between in-flight particle, splat and coating microstructure of thermally sprayed Ni20Cr were investigated. Flame spray and arc spray systems were employed for spraying Ni20Cr powder and Ni20Cr wire, respectively. The results showed that the arc spray process produced a broader size distribution for both in-flight particles and splats compared to flame process. Flower-like splat morphology was obtained from the arc spray whereas a pancake-like splat was obtained by flame spray. Ni20Cr coating sprayed by arc process had a denser microstructure, lower porosity and better adhesion at the interface.

• Journal of ILASS-Korea
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• v.18 no.4
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• pp.202-208
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• 2013

The present study aims to investigate the flow characteristics with respect to fuel type and equivalence ratio in the flame spray coating process. The flame spray flow is characterized by much complex phenomena including combustion, turbulent flows, and combined heat transfer. The present study numerically simulated the flam spray process and examined the gas dynamics involving combustion, gas temperature and velocity distributions in flame spray process by using commercial computational fluid dynamics (CFD) code of FLUENT (ver. 13.0). In particular, we studied the effect of fuel type and equivalence ratio on thermal and flow characteristics which could substantially affect the coating performance. From the results, it was found that the gas temperature distributions were varied with different fuels because of reaction times were different according to the fuel type. The equivalence ratio also could change the spatial flame distribution and the characteristics of coated layer on the substrate.

• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.128-140
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• 1996

To analyze a formation process of the soots in spray flame in the combustion chamber, an optically accessible DI Diesel engine was used for visualization. The images of the flames and soots were visualiaed with high speed camera by Schlieren method and Light extinction method. The spray flame and soot images on the films were analyzed at the various engine operating conditions. Soot distributed widely in spray flame and its concentration was about $100g/m^3$ at the position close by nozzle tip of spray flame region, however it decreased below $20g/m^3$ at the corner of combustion chamber due to soot oxidation.

• Journal of the Korean Society of Combustion
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• v.16 no.1
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• pp.58-65
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• 2011

Thermal spray technology has been used in many industrial application. Especially, thermal spray coating have been employed with the purposes of achieving better resistances in abrasion, heat and corrosion. In the previous studies on the thermal spray coating, thermal spray characteristics from the perspective of combustion engineering have not been investigated sufficiently, while the material characteristics of the coated substrates have been investigated widely. In this study, the effect of spray particles on the flame behavior was experimentally investigated. The amount of the injected particles was measured using the light scattering method and the temperature of the particles was estimated using a two-color method. Various flame-spray interactions were observed and it was found that the high temperature zone near the flame is elongated by particles density. Based on these results, the applicability of the light scattering method and the two-color method was discussed.