Transition Section: The Key Bridge Connecting the Combustion Chamber and the Turbine

The transition section is a critical component in gas turbines, serving as the key bridge between the combustion chamber and the turbine. Typically designed as a gradually expanding duct, its cross-sectional area increases progressively from the compressor to the combustion chamber. This design reduces the high-velocity, high-pressure airflow from the compressor, allowing for better fuel-air mixing and stable combustion within the combustion chamber. The length of the transition section varies based on the overall design and performance requirements of the gas turbine, with a focus on ensuring uniform airflow transition and minimizing pressure losses.

Material and Manufacturing

Due to the extreme operating conditions, the transition section must withstand high temperatures and pressures, particularly at the combustion chamber outlet, where it is exposed to the scouring effects of high-temperature combustion gases. As a result, it is typically constructed from high-temperature-resistant alloys, such as nickel-based superalloys. Advanced manufacturing techniques, including precision casting, are employed to ensure smooth internal surfaces, reducing airflow friction and enhancing efficiency. Additionally, some transition sections incorporate internal cooling channels to introduce cooling air, lowering component temperatures and ensuring structural integrity and stable performance in high-temperature environments.

Functional Role

1. From Compressor to Combustion Chamber:
   The transition section adjusts the airflow velocity and pressure. The high-velocity airflow from the compressor is slowed down to meet the combustion chamber’s requirement for lower-speed airflow, ensuring optimal fuel-air mixing and stable combustion.
2. From Combustion Chamber to Turbine:
   The transition section ensures the uniform distribution of high-temperature, high-speed gases into the turbine, enabling efficient energy extraction. Uniform airflow is critical to prevent issues such as incomplete combustion, localized overheating, or uneven stress on turbine blades.

Design Importance

The design of the transition section is crucial for maintaining uniform airflow distribution, which directly impacts the performance and reliability of the gas turbine. Special internal features, such as guide vanes and gradual wall shapes, help guide airflow evenly, improving combustion efficiency and turbine performance.

Impact on Turbine Performance

The transition section between the combustion chamber and the turbine significantly influences turbine performance. Non-uniform gas flow can lead to uneven thermal and mechanical stresses on turbine blades, reducing efficiency and potentially causing blade damage. Additionally, pressure losses in the transition section can affect the gas pressure at the turbine inlet, impacting the turbine’s ability to extract energy effectively.