• Journal of Mechanical Science and Technology
• /
• v.17 no.6
• /
• pp.906-913
• /
• 2003

Lean premixed combustion has been considered as one of the promising solutions for the reduction of NOx emissions from gas turbines. However, unstable combustion of lean premixed flow becomes a real challenge on the way to design a reliable, highly efficient dry low NOx gas turbine combustor. Contrary to a conventional diffusion type combustion system, characteristics of premixed combustion significantly depend on a premixing degree of combusting flow. Combustion behavior in terms of stability has been studied in a model gas turbine combustor burning natural gas and air. Incompleteness of premixing is identified as significant perturbation source for inducing unstable combustion. Application of a simple convection time lag theory can only predict instability modes but cannot determine whether instability occurs or not. Low frequency perturbations are observed at the onset of instability and believed to initiate the coupling between heat release rate and pressure fluctuations.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.2
• /
• pp.12-23
• /
• 2021

In this study, the combustion instability characteristics of low-swirl injector and high-swirl injector is compared by model gas turbine combustor. To compare of unstable behavior in high-swirl injector and low-swirl injector, we performed lots of measurement of combustion instability, with variable of equivalence ratio, combustor length and injector type. The results shown that longitudinal instability occur dominantly in model gas turbine combustor. In addition, it was found that high-swirl injector has more wide range of unstable regime than low-swirl injector. The blockage ratio what one of a parameter in low-swirl injector has not much effected in aspects of overall combustor behavior. Also, revealed that combustion instability occurred in the same combustor length has same properties, regardless of the injector type.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.1
• /
• pp.240-249
• /
• 1994

The basic experiments for designing the effective gas turbine combustor were performed. There are several factors that define the characteristics of gas turbine combustor. Among them, experiment was focused on swirl effects by three types of swirler with different swirl numbers(0.0, 0.38, and 0.62). Particularly, an interest was concentrated on primary zone where the flame characteristics of total combustor was dominated strongly and secondary zone where the remaining unburned gas was reacted again or cooling effect was done according to degree of swirl intensity. For this study, following measurements have been carried out, that is, time mean and fluctuating temperature, exhaust gas composition including NO concentration, and ion current. From this study, it was found that swirl intensity affects largely not only flame style but also emission formation, furthermore that it is important to select proper swirl intensity.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.279-282
• /
• 2002

Recently, gas turbines for power generation adopt multistage DLN(Dry Low NOx) type combustion, where diffusion combustion is applied at low load and, with increase in load, the combustion mode is changed to lean premixed combustion to reduce NOx emissive concentration. However, during the mode changeover from diffusion to premixed flame, unfavorable phenomena, such as flashback, high amplitude combustion oscillations, or thermal damage of combustor parts could frequently occur. In the present study, to apply for the analysis of such unfavorable phenomena, three-dimensional CFD investigations are carried out to compare the detailed flow characteristics and temperature distribution inside the gas turbine combustor before and after combustion mode changeover. The fuel considered here is pure methane gas. A standard $k-{\varepsilon}$ turbulence model with wall function and a P-N type radiation heat transfer model, have been utilized. To analyze the complex geometric effects of combustor parts on combustion characteristics, fuel nozzles, a swirl vane f3r fuel-air mixing, and cooling air holes on the combustor liner wall, are included in this simulation.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2946-2951
• /
• 2008

Combustion instability is a major issue in design of 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 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 the advantages of not only the transfer matrix method but also well-established classic control theories. The approach is applied to a simple gas turbine combustion system to demonstrate the validity and effectiveness of the approach.

• Journal of ILASS-Korea
• /
• v.28 no.3
• /
• pp.119-125
• /
• 2023

In this research, a network model was developed to predict combustion instability in an annular gas turbine combustor (GT24) for power generation. The model consisted of various acoustic elements such as several ducts and area changes which could represent a real combustor with a complex geometry, applied mass, momentum, and energy equations to each element. In addition, a one-dimensional network model through a cylindrical coordinate system has been proposed to predict various acoustic modes. As a result of the analysis, the key resonant frequencies such as longitudinal, circumferential, and complex modes were derived from the EV combustor of GT24, and the reliability of the current model was verified through comparison with the 3D Helmholtz solver.

• Journal of Ocean Engineering and Technology
• /
• v.14 no.3
• /
• pp.84-89
• /
• 2000

The purpose of this study is to investigate the combustion emission characteristics by the effect of secondary air injection and variation of the excess air ratio in combustion field of model gas turbine combustor. For this purpose, mean temperature, CO, $CO_2$, $O_2$ and HC concentrations were measured by changing excess air ratio and secondary air injection. As a result of this study, mean temperature was decreased and CO, HC emission increased by increasing the excess air ratio of secondary air. Therefore, this results showed the secondary air injection effected strongly on the flame structure and combustion emission characteristics.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2000.04a
• /
• pp.171-176
• /
• 2000

This purpose of this study is to investigate the combustion emission characteristics on the effect of secondary air injection in combustion field of model gas turbine combustor changing excess air ratio. For this purpose, meantemperature, CO, CO2, O2 and HC concentration were measured by changing excess air ratio and secondary air injection. As a result of this study, meantemperature, CO2 emission was decreased and CO emission increased by increasing the excess air ratio of secondary air. therefore, This paper showed the effect of Secondary air injection on flame structure, combustion emission characteristics.

• Advances in materials Research
• /
• v.8 no.2
• /
• pp.117-135
• /
• 2019

The lifetime of a gas turbine combustor is typically limited by the durability of its liner, the structure that encloses the high-temperature combustion products. The primary objective of the combustor thermal design process is to ensure that the liner temperatures do not exceed a maximum value set by material limits. Liner temperatures exceeding these limits hasten the onset of cracking which increase the frequency of unscheduled engine removals and cause the maintenance and repair costs of the engine to increase. Hot gas temperature prediction can be considered a preliminary step for combustor liner temperature prediction which can make a suitable view of combustion chamber conditions. In this study, the temperature distribution of ceramic panels for a V94.2 gas turbine combustor subjected to realistic operation conditions is presented using three-dimensional finite difference method. A simplified model of alumina ceramic is used to obtain the temperature distribution. The external thermal loads consist of convection and radiation heat transfers are considered that these loads are applied to flat segmented panel on hot side and forced convection cooling on the other side. First the temperatures of hot and cold sides of ceramic are calculated. Then, the thermal boundary conditions of all other ceramic sides are estimated by the field observations. Finally, the temperature distributions of ceramic panels for a V94.2 gas turbine combustor are computed by MATLAB software. The results show that the gas emissivity for diffusion mode is more than premix therefore the radiation heat flux and temperature will be more. The results of this work are validated by ANSYS and ABAQUS softwares. It is showed that there is a good agreement between all results.

• Journal of the Korean Society of Combustion
• /
• v.18 no.1
• /
• pp.1-6
• /
• 2013

Authors' previous works on thermoacoustic(TA) model development showed good results in predicting combustion instability characteristics in a gas turbine combustor. However, they also suggested there were some limitations in growth rate estimation, which might be related with over-simplification of flame structure. As a first trial for improving the model accuracy, the current paper introduces the modified TA model considering the actual flame location in the combustor. The combustor is divided into the unburned and the burned area before and after the flame location, and then acoustic equations are re-organized. The modified TA model results show a better accuracy in predicting the growth rate of instabilities comparing with the previous results. However, obtained results still overestimate the conditions where the combustor goes unstable. Further researches considering heat release distribution through flames are required.