• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.12
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• pp.1692-1698
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• 2002

A diesel engine has various merits such as high thermal-efficiency, superior fuel consumption and durability. Therefore the number of diesel engine in the world is increasing. As the seriousness of environmental pollution increases in the world, the method to reduce the noxious materials of $CO_2$, NOx and P.M. is very important subject to correspond to exhaust gas regulations. A new concept, so called premixed charge diesel combustion(PCCI), is focused among the various corresponding manners. In this study, we investigated the mixture formation within the cylinder with injection timing using GTT simulation code and also compared combustion characteristics of PCCI engine with that of commercial diesel engine. From this experiments, it could be found that homogeneous mixture formation was observed according to advance of injection timing and simultaneous reduction of NOx and Soot in injection timing of BTDC 60$^{\circ}$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.443-449
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• 2014

Thermoacoustic (TA) models have been widely used to predict combustion instability characteristics in a gas turbine lean premixed combustor. However, these techniques have shown some limitations in improving the model accuracy related to an over-simplification of the combustion system and flame geometry. Efforts were made in the current study to improve the limitations of the TA models. One strategy was to modify the actual flame location in the model, and another was to consider the heat release distribution through the flames. The modified TA model results show better accuracy in predicting the growth rate of instabilities compared with the previous results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.145-153
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• 1987

Stability limits of a double concentric jets flame and the structure of recirculation zone formed behind a thick burner rim were investigated. To control the flame stability, swirled secondary air flow ranging 0.13-0.71 of swirl number, and air, fuel, and mixture gas injection from an injection coaxial slit set on burner rim were examined. Flame stability limits, flame shapes, lengths of recirculation zone, temperature distributions, residence times, air ratios in the recirculation zone were measured. The following results were obtained. (1) Lean limits were considerably widened by a strong swirl because the recirculation zone was enlarged. (2) At fuel injection as well as mixture injection, lean limits were also extended. But, air injection had no effect on stability limits. (3) Injected gas seems to diffuse into the recirculation zone through its outer boundary surrounded the secondary air. Therefore, chemical structure in the recirculation zone with air injection coincides with that without injection. (4) Injection position had no effect on flame stability limits.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.274-280
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• 2005

Experimental investigations were carried out in an atmospheric pressure, optically accessible and laboratory-scale dump combustor. The objective of this study is to obtain the phase-resolved gas temperatures at different phases of the oscillating pressure cycle during unstable combustion. To see the effect of incomplete fuel-air mixing on phase-resolved temperature characteristics, CARS temperature measurements were performed. Results including phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs) were provided in this paper. It could be found that the profile of mean temperature showed the in-phase relationship with pressure cycle. Temperature PDFs give an insight on the flame behavior as well as NOx emission characteristics. These results would be expected to play an important role in better understanding of driving mechanisms and thermo-acoustic interactions.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.397-405
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• 2011

Hydrogen energy, as part of eco-friendly alternative energy, is made mostly through reforming of fossil fuels. The turbulent premixed combustion type of metal-fiber flat burner which is recently used in industry was tested in this paper. We measured the mean temperature distributions, CO, HC, $CO_2$ and $O_2$ concentrations to observe the flame structure and flame stability in some kind of experimental conditions. And also PIV and several flow analysis methods were compared to establish the numerical analysis model. The results of this paper will be the basis of the burner design of steam reformer.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.300-310
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• 1999

A constant-volume combustion chamber is developed to measure the burnt gas temperature over the wide ranges of equivalence ratio from 1.5 to 2.7 and pressure from 0.1 to 2.7 and pressure from 0.1 to 6 MPa by two-color method. The combustion temperature is also calculated by the conventional two-region model. The premixed fuel rich propane-oxygen-inert gas mixtures under high pressures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree intervals. The eight converging flames compress the end gases to high pressures. The transmissiv-ity in the chamber center during the final stage of combustion at the highest pressure is measured by in situ laser extinction method. Comparisons are made with the combustion temperatures between two-color method and two-region model. It is found that the burnt gas temperature mea-sured by two-color method is higher than that calculated by two-region model because of being the negative temperature gradient on the calculation and the temperature distribution of light path-length on the measurement and the burnt gas temperature for the turbulent combustion is higher than that of the laminar combustion under the same conditions because the heat loss for turbulent combustion is lower due to the shorter combustion period.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.68-77
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• 2017

High-frequency combustion instability results from a feedback coupling between the unsteady heat release rate and the acoustic waves formed resonantly in the combustion chamber. It can be modeled as thermoacoustic problems with various degrees of the assumptions and simplifications. This paper presents numerical analysis of self-excited combustion instabilities in a variable-length lean-premixed combustor and designs of passive control devices such as baffle and acoustic resonators in a framework of 3-D FEM Helmholtz solver. Nonlinear behaviors such as steep-fronted shock waves and a finite amplitude limit cycle are also investigated with a compressible flow simulation technique.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.181-186
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• 2004

Catalytic combustion is one of the suitable methods which is applicable to micro heat source due to high energy density and no flame quenching. And hydrogen can be oxidized at room temperature with platinum catalyst. So hydrogen-fueled micro catalytic combustor with platinum catalyst can be good and easy-handling heat source for another micro devices. In this work we focused on general catalytic combustion characteristics of hydrogen-air premixed gas in 10mm scale catalytic combustor for the further application to micro scale. Platinum was coated on dense ceramic monolith which can be installed in simple-structured catalytic combustor. We investigated the effect of flow rate, heat loss and platinum percentage in catalyst-coated monolith on catalytic combustion performance by temperature distribution in the combustor. By those results we confirmed catalytic reactivity and estimated reaction area. And we simulated micro scale catalytic reaction by sliced monolith. The results of this work will be important design factors for micro scale catalytic combustor.

• Journal of the Korean Society of Combustion
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• v.10 no.3
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• pp.17-24
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• 2005

A sub-millimeter scale catalytic combustor with a simple plate-shaped combustion chamber was fabricated. A porous ceramics support coated with platinum catalyst was placed in the chamber. The combustor has a gallium arsenide window on the top that is transparent to infrared ray. The temperature distribution in the combustion chamber was measured using infrared thermal imager while hydrogen-air premixture is steadily supplied to the combustor. The area where the catalytic reaction took place broaden for higher flow rate and lower equivalence ratio made activated area in the combustion chamber broaden. The amount of coated platinum catalyst did not affect the reaction. Stop of reaction, which is similar to flame quenching of conventional combustion, was investigated. Large content of heat generation and broad activated area are essential criteria to prevent stop of reaction that has a bad effect on the combustor performance.

• 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.