Abstract
The effects of H2 addition on a premixed methane-air flame was studied experimentally with a swirl-stabilized gas turbine model combustor. Experiments with 0%, 25%, and 50% H2 molar fraction in the fuel mixture were conducted under atmospheric pressure. The primary objectives are to study the impacts of H2 addition on flame lean blowout (LBO) limits, flame shapes and anchored locations, flow field characteristics, precessing vortex core (PVC) instability, as well as the CO emission performance. The flame LBO limits were identified by gradually reducing the equivalence ratio until the condition where the flame physically disappeared. The time-averaged CH chemiluminescence was used to reveal the characteristics of flame stabilization, e.g., flame structure and stabilized locations. In addition, the inverse Abel transform was applied to the time-averaged CH results so that the distribution of CH signal on the symmetric plane of the flame was obtained. The particle image velocimetry (PIV) was used to detect the characteristics of the flow field with a frequency of 2 kHz. The snapshot method of POD (proper orthogonal decomposition) and fast Fourier transform (FFT) were adopted to capture the most prominent coherent structures in the turbulent flow field. CO emission was monitored with an exhaust probe that was installed close to the combustor exit. The experimental results indicated that the H2 addition extended the flame LBO limits and the operation range of low CO emission. The influence of H2 addition on the flame shape, location, and flow field was observed. With the assistance of POD and FFT, the combustion suppression impacts on PVC was found.
Highlights
Modern gas turbines are preferred to operate at the lean premixed condition in order to control exhaust emissions, which can be harmful to the environment and human health [1,2]
Swirl flow is commonly utilized in gas turbine combustors for the flame stabilization, which is very important for the design of the gas turbine combustion system
The lean blowout (LBO) limit is defined as the equivalence ratio where the flame physically disappeared
Summary
Modern gas turbines are preferred to operate at the lean premixed condition in order to control exhaust emissions, which can be harmful to the environment and human health [1,2]. In order to overcome these negative effects, many investigations were attempted and the use of hydrogen and hydrogen blended fuels was identified as a considerable promise for a stable operation of gas turbine combustor under lean premixed conditions [4,5,6]. The H2 addition influence on the turbulent flame burning velocity of different fuels was investigated in many studies [7,8,9,10,11,12]. The enhanced reactivity was reported to increase the intensity of interactions between flame-vortex in turbulent flows [13].
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