• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1449-1457
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• 2009

Combustion instability is a major issue in design of co-generation gas turbine combustors for efficient operation with low emissions. Combustion instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to develop a technique to predict self-excited combustion instability of co-generation gas turbine combustors, a new stability analysis method based on the transfer matrix method is developed. The method views the combustion system as a one-dimensional acoustic system with a side branch and describes the heat source as the input to the system. This approach makes it possible to use not only the advantages of the transfer matrix method but also well established classic control theories. The approach is applied to a simple co-generation gas turbine combustion system, which shows the validity and effectiveness of the approach.

• Journal of the Korean Society of Combustion
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• v.21 no.4
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• pp.6-15
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• 2016

The oxygen fuel MILD (Moderate or Intense Low-oxygen Dilution) combustion has been considered as one of the promising combustion technology for flame stability, high thermal efficiency, low emissions and improved productivity. In this paper, the effect of oxygen and fuel injection condition on formation of MILD combustion was analyzed using lab scale oxygen fuel MILD combustion furnace. The results show that the flame mode was changed from a diffusion flame mode to a split flame mode via a MILD combustion flame mode with increasing the oxygen flow rate. A high degree of temperature uniformity was achieved using optimized combination of fuel and oxygen injection configuration without the need for external oxygen preheating. In particular, the MILD combustion flame was found to be very stable and constant flame temperature region at 7 KW heating rate and oxygen flow rate 75-80 l/min.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.306-311
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• 2013

Purpose: With the ever-rising energy prices, thermal energy heavily consuming facilities of the agricultural sector such as commercialized greenhouses and large-scale Rice Processing Complexes (RPCs) need to cut down their energy cost if they must run profitable businesses continually. One possible way to reduce their energy cost is to utilize combustible agricultural by-products or low-price oil instead of light oil as the fuel for their boiler systems. This study aims to analyze the heavy oil combustion characteristics of a newly developed hot water boiler system that can use both rice husk and heavy oil as its fuel convertibly. Methods: Heavy oil combustion experiments were conducted in this study employing four fuel feed rates (7.6, 8.5, 9.5, 11.4 $l/h$) at a combustion furnace vacuum pressure of 500 Pa and with four combustion furnace vacuum pressures (375, 500, 625, 750 Pa) at fuel feed rates of 9.5 and 11.4 $l/h$. Temperatures at five locations inside the combustion furnace and 20 additional locations throughout the whole hot water boiler system were measured to ascertain the combustion characteristics of the heavy oil. From the temperature measurement data, the thermal efficiency of the system was calculated. Flue gas smoke density and concentrations of air-polluting components in the flue gas were also measured by a gas analyzer. Results: As the fuel feed rate or combustion furnace vacuum pressure increased, the average temperature in the combustion furnace decreased but the thermal efficiency of the system showed no distinctive change. On the other hand, the thermal efficiency of the system was inversely proportionally to the vacuum level in the furnace. For all experimental conditions, the thermal efficiency remained in the range of 80.1-89.6%. The CO concentration in the flue gas was negligibly low. The NO and $SO_2$ concentration as well as the smoke density met the legal requirements. Conclusions: Considering the combustion temperature characteristics, thermal efficiency, and flue gas composition, the optimal combustion condition of the system seemed to be either the fuel feed rate of 9.5 $l/h$ with a combustion furnace vacuum pressure of 375 Pa or a fuel feed rate of 11.4 $l/h$ with a furnace vacuum pressure between 500 Pa and 625 Pa.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.460-468
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• 2021

This study investigated the enhanced combustion efficiency of an "air-cooled combustion system" with single F.D. fan, and performed a numerical analysis for the operation and design conditions to increase the combustion efficiency. The combustion efficiency in an actual combustor was compared before and after the structure modification. Numerical analysis for application of a single fan revealed the difficulty of forming a turbulence for circular combustion conditions. This is because the supply ratio of combustion air supplied into 2 flow paths becomes irregular in the combustion furnace due to a change in friction force and pressure in each flow path. Subsequently, two methods of supplying air into the combustion furnace were analyzed numerically to obtain the optimal combustion conditions of an air-cooled combustion system. The first method involved injecting the preheated combustion air after a 180~360 degree rotation from the outer wall, whereas in the second method, the combustion air was injected into the combustion furnace in a tangential direction after primary heat exchange outside the combustion furnace, by applying a rotatable vane structure in the combustion furnace. Results reveal that application of a single F.D. fan to the air injection into a rotatable combustion furnace is desirable for optimization of the combustion conditions for applying a duct structure having a dual cooling wall for the cooling of the outer wall of the combustion furnace, and for maintaining perfect mixing in the combustion furnace. We therefore confirmed enhanced combustion efficiency by comparing the actual combustion efficiency before and after structure modification.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2366-2371
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• 2007

Spray combustion characteristics of a conducting fuel electrospray have been studied for clean combustion technology. The multiplexing system which can retain the characteristics of the cone-jet mode is inevitable for the electrospray application. Charged micro droplets can be obtained in almost uniform size during operating the electrospray in the cone-jet mode. This experiment device set up the multiplexed grooved nozzle system with the extractor. Using the grooved nozzle, the stable cone-jet mode can be achieved at the each groove in the grooved mode. This electrospray system was applied to the diffusion combustion. It is the first step to discover the diffusion combustion characteristics of the electrospray. In case of the single grooved nozzle electrospray, the diffusion flames are occurred at each jet of grooved mode and they are quite stable. The exhaust gas analysis was indicated that there is the critical point which can make very stable diffusion combustion.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.225-230
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• 2004

Volatile organic compounds (VOCs) are low calorific value gases (LCVG) emitted from chemical processes such as painting booth, dye works and drying processes etc. Characteristics of VOCs are low calorific values less than 150 kcal/$m^3$, high activation energy for ignition and low energy output. These characteristics usually make combustion unstable and its treatment processes needs high-energy consumption, The cyclone combustion system is suitable for LCVG burning because it can recirculate energy through a high swirling flow to supply the activation energy for ignition, increases energy density to make a combustion temperature higher than usual swirl combustor and also increases mixing intensity, This research was conducted to develop optimized cyclone combustion system for thermal oxidation of VOCs. This research was executed to establish the effect of swirl number with respect to the combustion temperature and composition of exhausted gas in the specific combustor design.

• Journal of the Korean Society of Combustion
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• v.21 no.3
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• pp.24-31
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• 2016

In this paper we propose a new approach for an analysis and a prediction of combustion instability of lean premixed gas turbines. Our approach is based on the Nyquist stability criterion in control theory and a transfer function representation of a one-dimensional (1D) thermoacoustic system. A key advantage of the proposed approach is that one can systematically characterize the effects of various parameters of a combustor system on combustion instability. Our analysis method was applied to a real combustion system and the analysis results were consistent with experimental data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.12
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• pp.979-985
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• 2007

Spray combustion characteristics of the conducting fuel electrospray has been studied for clean combustion technology. The electrospraying multiplexed system which can maintain the characteristics of the cone-jet mode is able to obtain charged micro droplets with high flow rate. In addition, they have monodisperse distribution during operating the electrospray in the cone-jet mode. The multiplexed grooved nozzle system with the extractor was applied to this experimental device set up. The stable grooved mode can be generated by the grooved nozzle and this electrospray system was applied to the diffusion combustion. It is the first step to discover the diffusion combustion characteristics of the electrospray, In case of the single grooved nozzle electrospray the diffusion flames are occurred at each Jet of grooved mode and they are quite stable. The exhaust gas analysis was indicated that there is the critical point which can make very stable diffusion combustion

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1255-1265
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• 2001

A numerical study has been conducted to characterize the transient flow in a utility gas turbine burning natural gas. The solution domain encompasses the supply gas pressure regulator to the combustor of the gas turbine that employs multi-nozzle fuel injectors. Some results produced for verification in the present study agree suite well with the experimental ones. It is found that the total gas flow may decrease noticeably during its combustion mode change, which would be the reason of momentary combustion upset, when a reference case of opening ratios of control valves in the system is applied. Several parameters are then varied in order to make the total gas flow stable over that period of time. Results of this study may be useful to understand the unsteady behavior of combustion system burning natural gas.

• Journal of the Korean Society of Combustion
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• v.22 no.3
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• pp.8-16
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• 2017

MILD combustion was first developed to suppress thermal NOx formation in combustor for heating industrial furnaces. In this paper, the effect of co-flow MILD combustor geometry and operating conditions on the formation of MILD combustion was analyzed using 3 dimensional numerical simulation. The numerical simulations were carried out using ANSYS Fluent. The combustion and turbulence flow was modeled using the Eddy Dissipation Concept(EDC) model and realizable $k-{\varepsilon}$ model respectively. The results show that the high temperature region and average temperature decreased due to an increase in the air velocity and decrease the wall thickness of fuel nozzle. In particular, the MILD combustion flame was found to be stable with a combustion flame region at fuel velocity 10 m/s, air velocity 20 m/s, fuel nozzle thickness 1.0 mm, equivalence ratio 0.9, and outlet area ratio 40%.