Three-Stream Turbofan Fan Sizing for Packaging and Thermal Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional turbofan engines face challenges in packaging, weight, and thermal management due to the need for large fans to maximize thrust, leading to inefficiencies and increased thermal demands.
Innovation Solution
A three-stream turbofan engine design incorporating a primary and secondary fan, with the secondary fan providing airflow to a third stream, allowing for reduced primary fan thrust and improved propulsive efficiency through a specific relationship between the radius ratio of the fans and the percentage of thrust generated by the third stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a large fan is used to maximize thrust in conventional turbofan engines, then thrust is improved, but packaging and weight concerns worsen
Solution Approach 1:
The invention divides the single fan thrust generation function into multiple streams: a primary fan and a secondary fan (third stream). The primary fan generates the majority of thrust while the secondary fan provides additional thrust, allowing the primary fan to be smaller than a conventional single-fan design while maintaining total thrust output.
2Force
If a large fan is used to maximize thrust in conventional turbofan engines, then thrust is improved, but packaging concerns worsen
Solution Approach 1:
The invention divides the single fan thrust generation function into multiple streams: a primary fan and a secondary fan (third stream). The primary fan generates the majority of thrust while the secondary fan provides additional thrust, allowing the primary fan to be smaller than a conventional single-fan design while maintaining total thrust output.
3Force
If a large fan is used to maximize thrust in conventional turbofan engines, then thrust is improved, but thermal management efficiency worsens
Solution Approach 1:
The invention divides the single fan thrust generation function into multiple streams: a primary fan and a secondary fan (third stream). The primary fan generates the majority of thrust while the secondary fan provides additional thrust, allowing the primary fan to be smaller than a conventional single-fan design while maintaining total thrust output.
Solution Approach 2:
The third stream from the secondary fan is positioned to provide localized cooling in high-thermal-load areas of the engine. This targeted thermal management allows efficient heat dissipation without requiring the entire engine to be oversized for thermal reasons.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A gas turbine engine defining a centerline and a circumferential direction, the gas turbine engine including: a turbomachine comprising a compressor section, a combustion section, and a turbine section arranged in serial flow order, the turbomachine defining a working gas flowpath and a fan duct flowpath; a primary fan driven by the turbomachine defining a primary fan tip radius R1 and a primary fan hub radius R2; a secondary fan located downstream of the primary fan and driven by the turbomachine, at least a portion of an airflow from the primary fan configured to bypass the secondary fan, the secondary fan defining a secondary fan tip radius R3 and a secondary fan hub radius R4, wherein the secondary fan is configured to provide a fan duct airflow through the fan duct flowpath during operation to generate a fan duct thrust, wherein the fan duct thrust is equal to %Fn3S of a total engine thrust during operation of the gas turbine engine at a rated speed during standard day operating conditions; wherein a ratio of R1 to R3 equals EFP1−RqRSec.−Fan21−RqRPrim.−Fan21%Fn3s−1; wherein EFP is between 1.5 and 11, wherein RqRPrim.-Fan is a ratio of R1 to R2, and wherein RqRSec.-Fan is a ratio of R3 to R4.