Gas Turbine Compressor Arrangement with Gear-Driven Fan
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Solution Overview
Problem
In gas turbine engines, relative movement between compressor portions due to fan section movement decreases compression efficiency and complicates access to plumbing connections, particularly when the inlet case supports the compressor.
Innovation Solution
A gear arrangement driven by the low pressure turbine to drive the fan section, combined with a support member that restricts movement between the compressor case and inlet case, allowing the compressor case to be positioned axially further from the inlet case, simplifying access to plumbing connections and maintaining rotor alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inlet case supports the front portion of the compressor, then the compressor is supported during fan section movement, but relative movement between compressor portions varies rotor tip clearances and decreases compression efficiency
Solution Approach 1:
The compressor support function is segmented between the inlet case (supporting front portion) and the intermediate case structure (supporting rear portion). This segmentation allows the inlet case to be designed for easy plumbing access while the intermediate case provides stable support that maintains rotor tip clearances during fan section movement.
Solution Approach 2:
The intermediate case structure acts as an intermediary support element between the compressor and the engine structure. It provides a stable mounting point for the rear portion of the compressor, isolating the compressor from movements caused by fan section maneuvers and thereby maintaining consistent rotor tip clearances.
2Reliability
If the inlet case supports the front portion of the compressor, then the compressor is supported during fan section movement, but access to plumbing connections near the inlet case is complicated
Solution Approach 1:
The support function is segmented to the intermediate case structure, while the inlet case is segmented as a separate, accessible component. This allows the inlet case to be easily accessed for plumbing connections without compromising overall compressor support stability.
Solution Approach 2:
The support function is extracted from the inlet case and assigned to the intermediate case structure. This extraction allows the inlet case to be simplified and optimized for its primary function of guiding air and providing easy access to plumbing connections, while the intermediate case handles the support function.
3Adaptability or versatility
If a gear reduction is incorporated to drive the fan, then the low pressure turbine can drive both the low pressure compressor and the fan at different speeds, but the device complexity increases
Solution Approach 1:
The gear arrangement acts as an intermediary mechanism between the low pressure turbine and the fan. It enables independent speed control of the fan and low pressure compressor by providing a mechanical transmission path with a fixed gear ratio, allowing the fan to rotate at a different speed than the compressor while both are driven by the same turbine.
Data Source
AI summary
A gas turbine engine (90) includes a low pressure compressor section (18) and a high pressure compressor section (22). A low pressure turbine (34) drives the low pressure compressor section (18). A gear arrangement (62) is driven by the low pressure turbine (34) to in turn drive a fan section (14). A pressure ratio across the low pressure compressor section (18) is between about 4-8 and a pressure ratio across the high pressure compressor section (22) is between about 8-15. A compressor case (66) includes a front compressor case portion and a rear compressor case portion, with the rear compressor case portion being axially further from an inlet case (64) than the front compressor case portion. A support member (78) extends between the fan section (14) and the front compressor case portion.