Multi-Spool Gas Turbine Reverse Flow Architecture
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Solution Overview
Problem
Multi-spool gas turbine engines with asymmetrically mounted accessory gear boxes increase engine diameter and impact aerodynamic efficiency due to the extension of the tower shaft through the gaspath.
Innovation Solution
A reverse flow gas turbine engine design with independently rotatable low pressure and high pressure spools, where the LP spool drives the LP compressor and HP spool drives the HP compressor, with an accessory gear box connected to the HP spool and a gear train coupling the LP shaft to the LP compressor, minimizing the engine envelope and eliminating the need for a tower shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an accessory gear box is asymmetrically mounted on the radially outer surface of the engine case with a tower shaft extending through the gaspath, then the accessory gear box can be driven by the HP spool, but the engine diameter increases and aerodynamic efficiency is impacted
Solution Approach 1:
The invention extracts the tower shaft and its extension through the gaspath from the engine architecture. Instead, the accessory gear box is driven directly by the HP spool through a compact drivetrain arrangement that eliminates the need for a long tower shaft extending radially outward, thereby reducing the engine envelope diameter while maintaining accessory drive capability
Solution Approach 2:
The invention repositions the accessory gear box and its drive mechanism from a radial arrangement (requiring tower shaft extension) to an axial arrangement within the engine core. The AGB is positioned to be driven by the HP spool through axial or compact radial connections that do not extend the engine envelope, effectively moving the problem from radial dimension to axial dimension where space is better utilized
2Ease of operation
If a tower shaft is extended through the gaspath to drive the accessory gear box, then the accessory gear box can be mounted on the radially outer surface, but aerodynamic efficiency is impacted
Solution Approach 1:
The invention removes the tower shaft from the gaspath entirely. The accessory gear box is driven by the HP spool through a compact drivetrain that does not require shaft extension through the gaspath, thereby eliminating the aerodynamic interference and energy loss associated with the tower shaft presence in the airflow path
Solution Approach 2:
The invention introduces a compact intermediate drivetrain mechanism (gears, shafts, and bearings positioned within the engine core) that mediates between the HP spool and the accessory gear box. This intermediary system transfers power without requiring a long tower shaft extension, thus maintaining accessibility while avoiding aerodynamic penalties
3Area of stationary object
If the LP compressor is positioned with the gear train on the AGB facing side, then the engine envelope is minimized, but the gear train must be compactly arranged
Solution Approach 1:
The invention nests the gear train components within the LP compressor assembly and AGB housing structure. The gear train is arranged in a compact, space-efficient configuration that utilizes the available volume between the LP compressor and AGB, effectively nesting multiple functional elements within a constrained radial envelope to minimize overall engine diameter
4Adaptability or versatility
If the LP spool and HP spool are independently rotatable, then flexible power distribution is achieved, but the shafting and bearing system becomes more complex
Solution Approach 1:
The invention segments the engine into two independently rotatable spool systems (LP spool and HP spool), each with its own shaft and bearing supports. This segmentation allows flexible power distribution where the HP spool can drive both the HP compressor and the accessory gear box, while the LP spool drives the LP compressor and power output, with each spool optimized for its specific rotational speed and torque requirements
Data Source
AI summary
A multi-spool gas turbine engine comprises a low pressure (LP) spool and a high pressure (HP) spool independently rotatable about a central axis. The LP pressure spool has an LP compressor and an LP turbine. The HP spool has an HP turbine and an HP compressor. An accessory gear box (AGB) is drivingly connected to the HP spool. The LP compressor is disposed axially between the HP compressor and the AGB. A gear train drivingly couples the LP compressor to the LP turbine. The gear train is integrated to the AGB.