Accessory Gearbox Heat Exchanger Sizing for Compact Turbofans
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Solution Overview
Problem
Designing a compact and efficient heat exchanger system for turbofan engines that effectively processes the heat load generated by accessory gearboxes is challenging, as existing solutions often compromise on compactness, weight, and heat duty processing capabilities.
Innovation Solution
The development of a turbofan engine with heat exchangers that have a specific heat exchanger capacity range, which balances compactness, weight, and heat duty requirements by optimizing the heat transfer surface area density and heat conductance factor based on the engine's architectural and operational characteristics, including fan diameter, bypass ratio, and hydraulic pump power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If heat exchanger size is reduced to improve compactness, then device complexity is reduced, but heat duty processing capability deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the heat transfer surface area density (HTSADR) to specific ranges (4,000-13,000 m²/m³) and heat exchanger capacity (23.9-97.7) to achieve the optimal balance between compactness and heat duty processing capability. This quantitative parameter optimization allows the heat exchanger to be smaller while maintaining effective heat transfer performance.
2Productivity
If heat exchanger surface area is increased to improve heat duty processing, then heat transfer efficiency is improved, but device complexity and weight increase
Solution Approach 1:
The patent optimizes the heat transfer surface area density to specific ranges (4,000-13,000 m²/m³) to achieve effective heat duty processing without excessive surface area. This parameter optimization prevents overly complex structures while maintaining the necessary heat transfer capability.
3Weight of stationary object
If heat exchanger capacity is optimized for compactness, then weight is reduced, but heat conductance factor requirements become more stringent
Solution Approach 1:
The patent defines specific ranges for heat exchanger capacity (23.9-97.7) and heat transfer surface area density (4,000-13,000 m²/m³) that balance weight reduction with manufacturability. These optimized parameter ranges ensure that the heat conductance factor remains within achievable manufacturing tolerances while keeping the heat exchanger compact and lightweight.
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 results in optimally compact and effective heat exchangers that efficiently process the heat duty of the accessory gearbox, reducing the need for bulky designs and minimizing susceptibility to blocking or contamination, while facilitating easier manufacturing and improved engine performance.
Implementation Method 1
one or more heat exchangers tied to the accessory gearbox, the one or more heat exchangers having a heat exchanger capacity defined by a product raised to a half power, the product being determined by multiplying a resultant heat transfer surface area density associated with the one or more heat exchangers by a heat conductance factor
Implementation Method 2
a heat conductance factor that relates an accessory gearbox heat load associated with the accessory gearbox, a hydraulic pump power of a hydraulic pump mechanically coupled with the accessory gearbox, a fan diameter of a fan of the turbofan engine, and a bypass ratio of the turbofan engine
Data Source
AI summary
A turbofan engine having one or more heat exchangers tied to an accessory gearbox is provided. The accessory gearbox is mechanically coupled with a spool, and a hydraulic pump is mechanically coupled with the accessory gearbox. The one or more heat exchangers have a heat exchanger capacity defined by a product raised to a half power, the product being determined by multiplying a resultant heat transfer surface area density of the one or more heat exchangers by a heat conductance factor that relates an accessory gearbox heat load, a power of the hydraulic pump, a diameter of a fan, and a bypass ratio of the turbofan engine. The heat exchanger capacity is between 23.9 and 97.7 for a rotational speed of the spool between 7,500 and 35,000 revolutions per minute at one hundred percent capacity and a resultant heat transfer surface area density being between 4,000 m2/m3 and 13,000 m2/m3.