Three-Stream Gas Turbine Architecture for Fan Diameter Limits

The engine airflow is divided into three separate streams: a core stream through the combustor, a first bypass stream around the core, and a second bypass stream (third stream) further outward. This segmentation allows each stream to be optimized independently, enabling the outer bypass stream to contribute to propulsive efficiency without requiring a single oversized fan that would increase weight and packaging complexity.

The patent introduces a radial dimension to the bypass flow path by creating a second bypass stream that flows through an annular passage between the first bypass duct and the outer casing. This additional radial layering of airflow paths allows the engine to achieve high propulsive efficiency without increasing the overall engine diameter, thus avoiding packaging and weight penalties.

The engine employs a nested configuration where the core stream path is surrounded by the first bypass stream, which is in turn surrounded by the second bypass stream (third stream). The ducts and passages are arranged concentrically, with the inner components nested within outer components. This nesting allows multiple airflow paths to coexist within a compact radial envelope, maintaining high propulsive efficiency without increasing overall engine volume.

By adding a radial dimension to the bypass flow architecture with the annular second bypass passage, the engine achieves enhanced propulsive efficiency within the same axial and radial footprint. The third stream flows through the annular space between the first bypass duct and outer casing, utilizing otherwise wasted space and avoiding increases in engine volume.

The airflow is segmented into three distinct streams with separate ducts and passages: a core stream, a first bypass stream, and a second bypass stream (third stream). Each stream has its own dedicated flow path, allowing independent optimization of propulsive efficiency. The segmentation is achieved through carefully designed ducting that guides each stream through its own passage, maintaining clarity of function while improving performance.

The outer casing and structural components serve multiple functions: they contain the second bypass stream, provide structural support, and define the outer boundary of the engine. The annular passage for the third stream utilizes space between existing components, allowing the same structural elements to serve both structural and flow guidance functions, thereby limiting the increase in device complexity.