Tangential On-Board Injector Polygonal Inlet Design
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Solution Overview
Problem
Conventional manufacturing techniques for tangential on-board injectors (TOBIs) in gas turbine engines lead to airflow separation in cooling airflow passages, reducing the discharge coefficient (Cd) and engine efficiency, due to design constraints.
Innovation Solution
The use of additive manufacturing to create TOBI systems with polygonal inlet openings, such as triangular or pentagonal shapes, that gradually transition to a circular metering section, reducing flow separation and increasing the Cd, combined with subsequent machining to optimize the metering section for specific cooling requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional manufacturing techniques (drilled holes, cast shapes) are used to create cooling airflow passages in TOBIs, then the manufacturing process is simple and cost-effective, but airflow separation occurs in the passages which reduces the discharge coefficient and cooling efficiency
Solution Approach 1:
The invention changes the geometric parameters of the cooling airflow passages by transitioning from conventional circular cross-sections to polygonal cross-sections (triangular, square, rectangular, pentagonal, hexagonal, or other n-sided polygons). This parameter change in the passage geometry eliminates airflow separation and increases the discharge coefficient while maintaining manufacturability through additive manufacturing processes.
Solution Approach 2:
The invention replaces conventional mechanical manufacturing techniques (drilling, casting, reaming) with additive manufacturing technology. This substitution enables the creation of complex polygonal internal geometries that are impossible to achieve with traditional methods, thereby optimizing airflow patterns and discharge coefficients without increasing manufacturing complexity.
2Reliability
If the cooling airflow passages are designed to maximize discharge coefficient, then cooling efficiency improves, but the passages become more complex and difficult to manufacture using conventional techniques
Solution Approach 1:
The invention optimizes cooling efficiency by changing the cross-sectional geometry parameters from circular to polygonal shapes. The polygonal configuration with specific side numbers (3-6 or more) and optimized dimensions maximizes the discharge coefficient by preventing airflow separation, while additive manufacturing makes these complex geometries easy to produce.
Solution Approach 2:
The invention transitions from two-dimensional circular cross-sections to multi-dimensional polygonal cross-sections with varying numbers of sides. This dimensional complexity in the passage geometry allows for optimized airflow patterns and discharge coefficients that cannot be achieved with conventional circular passages, while additive manufacturing readily accommodates these complex three-dimensional geometries.
3Manufacturing precision
If polygonal inlet openings with gradual transition to circular metering section are used, then flow separation is reduced and discharge coefficient increases, but the manufacturing process becomes more complex requiring additive manufacturing and subsequent machining
Solution Approach 1:
The invention changes the geometric parameters of the inlet openings from conventional circular shapes to polygonal shapes with gradual transitions to circular metering sections. This parameter change optimizes flow patterns and discharge coefficients by eliminating abrupt transitions that cause flow separation, while the entire complex geometry is manufactured in one piece using additive manufacturing followed by precision machining of the metering section.
Solution Approach 2:
The invention segments the cooling airflow passage into distinct geometric zones: a polygonal inlet opening section for optimal flow entry, a gradual transition section for smooth geometry change, and a circular metering section for precise flow control. This segmentation allows each zone to be optimized for its specific function while being manufactured as an integrated component through additive manufacturing and selective machining.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances cooling efficiency by minimizing airflow separation and maximizing the discharge coefficient, leading to improved turbine cooling and operational performance.
Implementation Method 1
TOBIs have been prone to experience cooling airflow separation within the cooling airflow passages. Airflow separation (i.e., an airflow at the walls of the passages characterized by eddies and vortices, as compared to a smooth boundary layer) has been shown to significantly reduce the Cd value
Data Source
AI summary
Disclosed is a tangential on-board injector (TOBI) system that includes an annulus and a plurality of cooling airflow passages disposed about the annulus. Each cooling airflow passage of the plurality of cooling airflow passages includes an inlet opening having a polygonal inlet cross-section, the inlet opening having an inlet cross-sectional area. Each cooling airflow passage of the plurality of cooling airflow passages further includes an outlet opening having an outlet cross-section and an outlet cross-sectional area. The inlet cross-sectional area is greater in magnitude than the outlet cross-sectional area. Also disclosed are additive manufacturing methods for manufacturing the tangential on-board injector system and gas turbine engines that incorporate the tangential on-board injector system.