Turbofan Engine Fan Axis Angle for Compact Packaging
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Solution Overview
Problem
Conventional gas turbine engines face performance issues due to the use of bypass air or compressor offtakes as cooling mediums, leading to reduced specific thrust and increased specific fuel consumption, as well as reduced surge margin.
Innovation Solution
A turbofan gas turbine engine design with a specific fan axis angle and electric machine sizing that allows for a more compact engine configuration, incorporating a first electric machine positioned downstream of the fan assembly and connected to the turbine module, and a heat exchanger module positioned in the inlet duct to enhance packaging and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bypass air or compressor offtake is used as cooling medium in heat exchanger, then cooling function is provided, but specific thrust is reduced and specific fuel consumption increases
Solution Approach 1:
The patent extracts the cooling function from the main engine airflow path by using a separate air intake system. The heat exchanger receives cooling air from an independent source rather than diverting air from the compressor or bypass duct, thus separating the cooling need from the propulsive airflow path and avoiding thrust penalties.
Solution Approach 2:
The heat exchanger is designed to serve multiple functions: it provides cooling for engine components while simultaneously heating the incoming air from the separate intake. This dual function allows the system to manage thermal loads efficiently without compromising engine performance or requiring additional cooling resources.
2Temperature
If bypass air or compressor offtake is used as cooling medium, then cooling is achieved, but surge margin is reduced
Solution Approach 1:
The cooling air supply is extracted from the engine's main airflow path and replaced with an independent intake system. This separation ensures that the compressor and bypass airflow remain undisturbed, maintaining proper airflow dynamics and surge margin while still providing adequate cooling through the heat exchanger.
3Power
If conventional turbofan engine configuration is used, then engine performance is maintained, but engine length is excessive for packaging
Solution Approach 1:
The patent introduces a specific fan axis angle (α) between 11° and 20° relative to the engine centerline, creating a three-dimensional geometric configuration that optimizes space utilization. This angular arrangement allows the fan assembly to be positioned more compactly along the engine axis while maintaining the necessary outer diameter and airflow characteristics, thereby reducing overall engine length without sacrificing performance.
Solution Approach 2:
The patent modifies the geometric parameters of the engine configuration by defining a specific range for the fan axis angle (11°-20°). This parameter change enables a compact packaging arrangement that reduces engine length while preserving the aerodynamic and performance characteristics of conventional turbofan engines.
Data Source
AI summary
An aircraft turbofan gas turbine engine includes a fan assembly, a compressor module, and a turbine module. An electric machine is positioned downstream of the fan assembly and is connected to the turbine module. The fan assembly includes a highest pressure fan stage having a plurality of fan blades defining a fan diameter. The turbine module includes a lowest pressure turbine stage having a row of rotor blades. The gas turbine engine has a fan tip axis that joins a radially outer tip of the leading edge of one of the plurality of fan blades of the highest pressure fan stage, and the radially outer tip of the trailing edge of one of the rotor blades of the lowest pressure turbine stage. The fan tip axis lies in a longitudinal plane which contains a centreline of the gas turbine engine. The fan axis angle is between 11 and 20 degrees.