Geared Turbine Front Section With Transitional Compressor Inlet
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Solution Overview
Problem
Turbofan engine manufacturers seek improvements in thermal, transfer, and propulsive efficiencies, particularly in the design of the front section to enhance airflow efficiency into the compressor section.
Innovation Solution
The design includes a fan section with a fan hub supporting a limited number of fan blades, a transitional entrance passage with specific diameter ratios, and a geared architecture to rotate the fan hub at a lower speed than the turbine section, optimizing airflow and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a speed reduction device such as an epicyclical gear assembly is utilized to drive the fan section at a different speed than the turbine section, then propulsive efficiency is increased, but the complexity of the front section architecture increases and influences airflow paths
Solution Approach 1:
The front section is segmented into distinct functional zones: fan section, transitional entrance passage, and compressor section. This segmentation allows independent optimization of each zone while managing the complexity introduced by the gear assembly.
Solution Approach 2:
A transitional entrance passage is introduced as an intermediary component between the fan section and compressor section. This passage mediates the airflow disruption caused by the gear assembly, smoothing flow paths and reducing the negative impact on compressor inlet conditions.
2Volume of moving object
If the hub diameter to tip diameter ratio is optimized for compactness, then engine size is reduced, but airflow efficiency into the compressor section may be compromised
Solution Approach 1:
The patent optimizes the hub diameter to tip diameter ratio within a specific range (0.24-0.36) to achieve compactness while maintaining airflow efficiency. This parameter optimization allows the engine to achieve high power density without sacrificing compressor inlet flow quality.
Solution Approach 2:
The transitional entrance passage introduces dimensional transitions in the airflow path, accommodating the compact hub design while preserving airflow efficiency through carefully designed passage geometry that manages flow acceleration and direction.
3Area of stationary object
If the hub diameter to inlet diameter ratio is increased for compact design, then engine footprint is reduced, but airflow uniformity into the compressor may deteriorate
Solution Approach 1:
The transitional entrance passage serves as an intermediary that reconciles the conflict between compact dimensions and airflow uniformity. The passage geometry is designed to accelerate and straighten flow while maintaining uniformity despite the constrained hub-to-inlet diameter ratio (0.65-0.95).
Solution Approach 2:
Different regions of the transitional entrance passage are designed with locally optimized characteristics to manage airflow uniformly. The passage geometry varies along its length to progressively condition the flow, ensuring uniform inlet conditions to the compressor despite the compact overall dimensions.
Data Source
AI summary
A gas turbine engine includes a propulsor section including a propulsor hub, the hub including a hub diameter supporting a plurality of propulsor blades, a compressor section including a first compressor and a second compressor aft of the first compressor relative to an engine longitudinal axis, and a turbine section including a first turbine and a second turbine. A geared architecture that interconnects the first turbine and the propulsor hub such that the fan hub is rotatable at a lower relative speed than the first turbine. A compressor inlet passage is disposed annularly about the geared architecture.