Gas Turbine Accessory Gear Box Nesting
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Solution Overview
Problem
The increasing size of the fan case in turbofan engines due to higher bypass ratios leads to a larger outer diameter and frontal projected area of gas turbine engines, making it challenging to accommodate the accessory gear box and auxiliary compressor outside the fan case without increasing the engine's dimensions.
Innovation Solution
The accessory gear box and auxiliary compressor are positioned inside the inner cowl between the core casing and the inner peripheral surface of the bypass passage, allowing the auxiliary compressor to be driven by the accessory gear box and increase air pressure for the airframe, while maintaining a smaller outer diameter for the gas turbine engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the accessory gear box and auxiliary compressor are located outside the fan case, then the components are easily accessible for maintenance and installation, but the outer diameter of the entire gas turbine engine increases
Solution Approach 1:
The accessory gear box and auxiliary compressor are nested within the inner cowl structure, which itself is contained within the fan case. This nested arrangement allows the components to be protected and integrated within the existing engine envelope without increasing the overall outer diameter, while still maintaining accessibility through the cowl removal mechanism.
Solution Approach 2:
The patent utilizes the radial space within the fan case by introducing an inner cowl structure that creates a new dimensional space for housing the accessory gear box and auxiliary compressor. This inner cowl arrangement effectively uses the available radial dimension without increasing the external diameter of the engine.
2Productivity
If the fan size is increased to improve bypass ratio and fuel efficiency, then fuel efficiency is improved, but the outer diameter and frontal projected area of the gas turbine engine increase
Solution Approach 1:
The accessory gear box and auxiliary compressor are nested within the inner cowl structure, which itself is contained within the fan case. This nested arrangement allows the components to be protected and integrated within the existing engine envelope without increasing the overall outer diameter, while still maintaining accessibility through the cowl removal mechanism.
Solution Approach 2:
The inner cowl structure creates a localized space within the fan case specifically for housing the accessory gear box and auxiliary compressor. This local quality approach allows the fan to be optimized for bypass ratio while the inner cowl provides a dedicated space for components without affecting the overall engine diameter.
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 configuration reduces the overall diameter of the gas turbine engine by relocating the accessory gear box and auxiliary compressor inside the inner cowl, optimizing engine size and efficiency.
Implementation Method 1
an auxiliary compressor that is attached to the accessory gear box, is driven by power acquired from the accessory gear box, and increases pressure of compressed air extracted from the core engine
Data Source
AI summary
A core engine including a core casing covering a low-pressure rotary structure and a high-pressure rotary structure and includes a passage of air flowing through the low-pressure and the high-pressure rotary structures; a fan located in front of the core engine; an inner cowl serving as an inner peripheral surface of a bypass passage that extends through the fan and bypasses the core engine; an accessory gear box that extracts power from the low-pressure or the high-pressure rotary structure and supplies the power to accessories; an auxiliary compressor attached to the accessory gear box, is driven by power of the accessory gear box, and increases pressure of compressed air extracted from the core engine; and a compressed air pipe that extends through an inside of a strut connecting the core engine and an airframe and supplies the compressed air having an increased pressure by the auxiliary compressor to the airframe.