Combustion Instability Characteristics Under Various Fuel and Air Flow Rates in a Partially Premixed Model Gas Turbine Combustor

2019 ◽  
Author(s):  
Sanghyeok Kwak ◽  
Seongpil Joo ◽  
Seongheon Kim ◽  
Jaehong Choi ◽  
Youngbin Yoon
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Combustion Instability ◽  
Rate Variation ◽  
Flow Rates ◽  
Exit Velocity ◽  
Longitudinal Modes ◽  
Partially Premixed ◽  
Instability Frequency ◽  
Flame Position

Abstract In this study, the combustion instability characteristics are experimentally investigated in a partially premixed gas turbine model combustor. The combustor is operated with methane and preheated air as the fuel and oxidizer, respectively, at atmospheric pressure. The experiment is carried out at various equivalence ratios and flow rates of fuel and air to investigate the effect on the combustion instability frequency transition. According to the experimental results, the transition of the combustion instability frequency to higher longitudinal mode occurs because of the flow rate variation. To explain the frequency shift phenomenon, the concept of convection time is introduced, which is mostly affected by the flame position and exit velocity of the fuel-air mixture. The flame positions are measured using OH planar laser-induced fluorescence (OH-PLIF), and the flow field information is obtained using particle image velocimetry to calculate the convection time. The measurement results show that the injection velocities of fuel and air are also important factors in determining the combustion instability frequency as well as the equivalence ratio, which is a crucial parameter of the flame position. As a result, it is found that the decrease in convection time owing to a closer distance from the dump plane to the flame and a faster exit velocity of the fuel-air mixture causes the combustion instability frequency mode shift. Additionally, the structural characteristics of the flame are analyzed using high-speed OH-PLIF measurement. The differences in the flame structure between the stable and unstable flames in the 2nd and 3rd longitudinal modes are analyzed. The change in the unburned mixture is mainly observed and the relationship between the dynamic pressure, heat release rate, and length of the unburned region is also analyzed.

The Effect of Fuel Composition on Combustion Instability Mode Occurrence in a Model Gas Turbine Combustor

2015 ◽  
Author(s):  
Jisu Yoon ◽  
Seongpil Joo ◽  
Min Chul Lee ◽  
Jeongjin Kim ◽  
Jaeyo Oh ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Alternative Fuels ◽  
Combustion Instability ◽  
Longitudinal Mode ◽  
Fuel Composition ◽  
Instability Mode ◽  
Gas Turbine Combustor ◽  
Global Issues ◽  
Model Gas Turbine Combustor ◽  
Instability Frequency

Recently, energy resource depletion and unstable energy prices have become global issues. Worldwide pressure to secure and make more gas and oil available to support global power needs has increased. To meet these needs, alternative fuels composed of various types of fuels have received attention, including biomass, dimethyl ether (DME), and low rank coal. For this reason, the fuel flexibility of the combustion system becomes more important. In this study, H2 and CH4 were selected as the main fuel composition variables and the OH-chemiluminescence measurement technique was also applied. This experimental study was conducted under equivalence ratio and fuel composition variations with a model gas turbine combustor to examine the relation between combustion instability and fuel composition. The combustion instability peak occurs in the H2/CH4 50:50 composed fuel and the combustion instability frequency shifted to higher harmonic of longitudinal mode based on the H2 concentration of the fuel. Based on instability mode and flame length calculation, the effect of the convection time during the instability frequency increasing phenomenon was found in a partially premixed gas turbine combustor. The time-lag analysis showed that the short convection time in a high H2 concentration fuel affects the feedback loop period reduction and, in these conditions, high harmonics of longitudinal mode instability occurs. This fundamental study on combustion instability frequency shifting characteristics was conducted for H2/CH4 composed fuel and the results contribute key information for the conceptual design of a fuel flexible gas turbine and its optimum operation conditions.

scholarly journals Combustion Instability Monitoring through Deep-Learning-Based Classification of Sequential High-Speed Flame Images

Electronics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 848 ◽  
Author(s):  
Ouk Choi ◽  
Jongwun Choi ◽  
Namkeun Kim ◽  
Min Chul Lee
Keyword(s):  
Deep Learning ◽  
Gas Turbine ◽  
High Speed ◽  
Combustion Instability ◽  
Stable Condition ◽  
Late Fusion ◽  
Backbone Network ◽  
Early Fusion ◽  
Network Layers ◽  
Promising Tool

In this study, novel deep learning models based on high-speed flame images are proposed to diagnose the combustion instability of a gas turbine. Two different network layers that can be combined with any existing backbone network are established—(1) An early-fusion layer that can learn to extract the power spectral density of subsequent image frames, which is time-invariant under certain conditions. (2) A late-fusion layer which combines the outputs of a backbone network at different time steps to predict the current combustion state. The performance of the proposed models is validated by the dataset of high speed flame images, which have been obtained in a gas turbine combustor during the transient process from stable condition to unstable condition and vice versa. Excellent performance is achieved for all test cases with high accuracy of 95.1–98.6% and a short processing time of 5.2–12.2 ms. Interestingly, simply increasing the number of input images is as competitive as combining the proposed early-fusion layer to a backbone network. In addition, using handcrafted weights for the late-fusion layer is shown to be more effective than using learned weights. From the results, the best combination is selected as the ResNet-18 model combined with our proposed fusion layers over 16 time-steps. The proposed deep learning method is proven as a potential tool for combustion instability identification and expected to be a promising tool for combustion instability prediction as well.

Investigation into the cause of high multi-mode combustion instability of H2/CO/CH4 syngas in a partially premixed gas turbine model combustor

2015 ◽  
Vol 35 (3) ◽  
pp. 3263-3271 ◽  
Author(s):  
Min Chul Lee ◽  
Jisu Yoon ◽  
Seongpil Joo ◽  
Jeongjin Kim ◽  
Jeongjae Hwang ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Combustion Instability ◽  
Partially Premixed ◽  
Multi Mode ◽  
Turbine Model

scholarly journals Wall Temperature Measurements in Gas Turbine Combustors With Thermographic Phosphors

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Patrick Nau ◽  
Zhiyao Yin ◽  
Oliver Lammel ◽  
Wolfgang Meier
Keyword(s):  
Gas Turbine ◽  
Wall Temperature ◽  
Gas Turbines ◽  
High Speed ◽  
Bluff Body ◽  
Temperature Measurements ◽  
Transient Temperature ◽  
High Time Resolution ◽  
Ceramic Surface ◽  
Precessing Vortex Core

Phosphor thermometry has been developed for wall temperature measurements in gas turbines and gas turbine model combustors. An array of phosphors has been examined in detail for spatially and temporally resolved surface temperature measurements. Two examples are provided, one at high pressure (8 bar) and high temperature and one at atmospheric pressure with high time resolution. To study the feasibility of this technique for full-scale gas turbine applications, a high momentum confined jet combustor at 8 bar was used. Successful measurements up to 1700 K on a ceramic surface are shown with good accuracy. In the same combustor, temperatures on the combustor quartz walls were measured, which can be used as boundary conditions for numerical simulations. An atmospheric swirl-stabilized flame was used to study transient temperature changes on the bluff body. For this purpose, a high-speed setup (1 kHz) was used to measure the wall temperatures at an operating condition where the flame switches between being attached (M-flame) and being lifted (V-flame) (bistable). The influence of a precessing vortex core (PVC) present during M-flame periods is identified on the bluff body tip, but not at positions further inside the nozzle.

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