Challenges in Gas Turbine Combustor Operation
Gas Turbine combustor operation is limited by many factors such as flame stability, emissions limitations, and combustion dynamics. We are going to focus on flame stability in this short blog. During most of the life of a combustor it operates at a low fuel air ratio (lean). The flame could be attached (to a structure) or detached (stabilized by flow swirl/recirculation). As combustion is made leaner in the primary combustion zone, the flame can lose its stability, resulting in operability problems such as lean blowout (LBO) or flashback. The combustor manufacturer needs to identify the operational range accurately.
Engineering Solution
Numerous approaches are available to control flame stability is available. Most use:
1. a bluff body
2. a swirler
3. a pilot flame
4. counter fuel flow
5. active fuel-air ratio control
Computational Fluid Dynamics (CFD) methods are the most common physics based approaches to model the highly complex, reacting turbulent flow field present in Combustors. Manufacturers routinely use such simulations to predict combustion and pressure. The detailed flow, thermal and chemistry kinetics information in turn is used to improve component design for flame stability issues.
Ansys Solution Benefits
Several different physics contribute to flame stability such as vortex dynamics, mixing dynamics, flame kinematics, and chemical kinetics. Ansys Fluent offers industry validated and accurate models to capture all of these physics. Modeling effect of flame stretch rate and heat loss is crucial for the prediction of premixed flame dynamics. Better understanding of premixed flame dynamics helps achieve stable operation over full range of engine conditions even with fuel flexibility.
Fig. 1 Qualitative comparison of flame propagation using Fluent
Fig 2. Accurate prediction of lean blowout limit with strained FGM
Ozen Engineering Expertise
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Suggested blogs
- Ozen Engineering Inc. Blog: Gas Turbine Combustor: Heat Transfer and Life Prediction
- Ozen Engineering Inc. Blog: Gas Turbine Combustor: Emissions
- Ansys Blog: 5 best practices for gas turbine combustor meshing
