• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.3
• /
• pp.157-166
• /
• 2009

The pulverized coal combustion behavior in the coal fired utility boiler has been investigated with the CFD and process analysis techniques. The used commercial software were CFX and PROATES, and these were coupled each other to get more reliable boundary condition set-up, resulting in more reliable solution. For two cases which were the actual operation condition of A power plant, the calculated values from the coupled CFD and process analysis for thermal energy system were compared with the plant data, and the good agreements were obtained for Case 1 and 2. The calculated temperature distributions on the surface of heat exchangers were compared with the plant data for the steam temperatures across heat exchangers, and these explained the actual operating situation very well. The temperature deviation across the final superheater tube, which was believed to be the main cause of the frequent tube failure, were also explained very well with the calculated distributions of gas temperature and radiation on the plane of the final superheater.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.5
• /
• pp.750-756
• /
• 2002

The effect of equivalence ratio and velocity on the stability of flame in dump combustor was studied in an atmospheric pressure, laboratory scathe dump combustor operating natural gas. Traditionally, peak-to-peak pressure, fluctuation of the heat release rate and Rayleigh index were used to find and control the combustion instability. Cross correlation coefficients, Ci,j which is defined as the normalized value of the integration of the product of two of the mixer pressure, dump plane pressure and heat release rate, are introduced to see whether the flame is stable or not. Ci,j shows more sensitive to combustion status than Rayleigh index in steadily burning flame. Also, the result indicates that the amplitude of Ci,j between heat release and mixer pressure goes up before the flame at the rich de-stabilizing equivalence ratio near $\psi$=0.85. t means Ci:j at this case has a potential to detect the de-stablizing moment in prior to becoming unstable in dump combustor.

• Fire Science and Engineering
• /
• v.24 no.6
• /
• pp.120-125
• /
• 2010

Wood-Plastic Composites (WPCs) are one of spotlighting materials for the residential construction and the industry for furniture. At this study, the limiting oxygen index (LOI) was measured by ASTM D 2863 and the cone calorimeter test was done by ISO 5660-1 to find the combustion characteristics of WPCs. In addition, the identical test was implemented to compare the combustion characteristics between the red pine and the antiseptic wood. The result of LOI measurement showed that the LOI of WPCs was lower than that of red pine or antiseptic wood. The cone calorimeter test showed that the heat release rate (HRR) of WPCs was the highest and the Peak HRR as well as the average HRR and total heat release of WPCs was higher than those of red pine or antiseptized wood

• Journal of computational fluids engineering
• /
• v.14 no.1
• /
• pp.9-17
• /
• 2009

In this study we investigated the characteristics of fluid flow and heat transfer within a coolant passage in the cylinder head assembly of an internal combustion engine by using a commercial CFD code, CFX The complex coolant passage of the cylinder head assembly was modelled by suitable choice of a grid system and careful attention was paid in the construction of meshes near the walls where significant cooling occurs. To treat the simultaneous heating and cooling of the combustion walls we invented a methodology allowing a heat source within the solid wall and the convective cooling at the interface between the solid and the fluid. We managed to reproduce the experimental results by adjusting parameters appropriately. We have found that high temperature was concentrated at the surface of the cylinder jacket. It turned out that the effect of oil cooling from the piston head was unexpectedly significant. On the other hand the effect of cooling from the ambient air is almost negligible. The CFD method proposed in this study is believed to be useful in the early stage of the design of the engine-cooling system.

• Journal of the Korean Society for Heat Treatment
• /
• v.16 no.3
• /
• pp.148-158
• /
• 2003

In this study, a user oriented CFD program for optimum design of a regenerative combustion furnace, REBURN was developed. For user's convenience, user friendly Graphic User Interface was made and the renumbering interface program was developed in order to directly input any generated mesh system from ICEM CFD/FEA. Also an automatic processing system for switching mode was developed. The program was verified through compahng with commercial CFD code about regenerative combustion furnace. Then, numerical simulation of real walking beam furnace used in real industry was performed and the parametric analysis was studied about the arrangement mode. As a results, the uniform temperature was appeared in the cross mode.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.1
• /
• pp.17-23
• /
• 2002

In order to reduce exhaust emissions from diesel engine under wide operating range, an experimental study based on a new concept of combustion called HCDC(Homogeneous Charge Diesel Combustion) was conducted. In this concept, most of the fuel is supplied as premixed homogeneous charge and the rest is directly injected into a cylinder to ignite. In this study we compared combustion characteristics of an HCDC engine with those of conventional diesel engines. At high premixed fuel ratio and high load range, it was observed that premixed combustion heat release rate was low and diffusion combustion duration was shorten. from this experiment, it was found that NOx is reduced by the lower maximum temperature and soot is reduced by rapid combustion during diffusion combustion phase.

• Journal of the Korean Society of Combustion
• /
• v.4 no.1
• /
• pp.95-103
• /
• 1999

Experimental study on combustion characteristics of a regenerative combustor has performed. High-temperature air combustion in the regenerative combustor is obtained through heat recovery from exhaust gas flow by porous ceramic materials and through alternation of air flow direction through the combustor. Temperature field, CO and NOx emission with respect to the frequency of alternation are measured. It is found that at initial stage of the alternation, temperature of inlet section of main combustion chamber is increased sharply since both high temperature air preheated by the ceramics and prompt fuel injection results in rapid combustion. Following this initial stage, combustion temperature is reduced as the preheated air temperature is reduced. However peak temperature in the chamber and exhaust gas temperature are decreased as the alternation period is reduced, increased temperature of ceramic is observed. CO and NOx emission with respect to the alternation period is also examined. It is found that there exists a range of optimum alternating period for CO and NOx emission characteristics.

• 한국연소학회:학술대회논문집
• /
• 2000.05a
• /
• pp.67-75
• /
• 2000

Computational fluid dynamics(CFD) analysis of the thermal flow in a municipal solid waste(MSW) incinerator combustion chamber provides crucial insight on the incinerator performance. However, the combustion of the waste bed is typically treated as an arbitrarily selected profile of combustion gas. A strategy for simultaneous simulation of the waste bed combustion and the thermal flow fields in the furnace chamber was introduced to substitute the simple inlet condition. A waste bed combustion model was constructed to predict the progress of combustion in the bed and corresponding generation of the gas phase species, which assumes the moving bed as a packed bed of homogeneous fuel particles. When coupled with CFD, it provides boundary conditions such as gas temperature and species distribution over the grate, and receives radiative heat flux from CFD. The combined simulation successfully predicted the physical processes of the waste bed combustion and its interaction with the flow fields for various design and operating parameters, which was limited in the previous CFD simulations.

• 한국연소학회:학술대회논문집
• /
• 2012.11a
• /
• pp.59-60
• /
• 2012

This paper describes gas turbine combustion characteristics of synthetic gas which is mainly composed of hydrogen and carbon monoxide. The combustion characteristics such as combustion instability, NOx and CO emission, temperatures at turbine inlet, liner and dump plane, and flame structure were investigated when changing when changing $H_2:CO$ ratio, dilution ratio, and $CH_4:syngas$ ratio. From the results, quantitative relationships are derived between key aspects of combustion performance, notably NOx emission. It is concluded that NOx emission of syngas is strongly influenced by the diluent heat capacity and combustion instability. Moreover, NOx control method using diluents such as $N_2$, $CO_2$, steam is verified.

• Journal of the Korean Society of Combustion
• /
• v.15 no.2
• /
• pp.19-26
• /
• 2010

Combustion behavior of pulverized coal particles in a post-combustion gas reactor was investigated. Radiation emission from coal particles were analyzed by direct photograph and $CH^*$ radical chemiluminescence intensity. Coal particles were sampled during the combustion and were observed by scanning electron microscopy (SEM) and cross section micrograpy technique. Two coal types(one bituminous and one subbituminous coals typically used in the Korean power plants) were tested at typical combustion environment. Gas flow conditions were controlled to represent temperature and oxygen concentration. Experimental data were discussed along with conceptual descriptions of pulverized coal combustion, where particle heat-up, release and combustion of volatiles, and char combustion were sequentially progressed.