Ducted Spinner Cooling for Ducted Fan Engine Thrust Losses
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Solution Overview
Problem
Ducted fan aircraft face significant thrust losses and drag issues due to the proximity of the air-cooled engine to the fan rotor, where conventional cooling systems either result in separated airflow or increased weight with long crankshafts.
Innovation Solution
A ducted spinner system comprising a first nacelle surrounding the engine, a second concentric nacelle, and a duct formed between the first and second spinners, with airfoils penetrating through both, providing cooling airflow and structural support while optimizing airflow speed and pressure to minimize drag and thrust losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the engine is placed in close proximity to the fan rotor, then the aircraft achieves a compact design, but thrust losses and drag increase significantly
Solution Approach 1:
The rotor blades are segmented into two functional portions: a first portion (inner portion) located within the cooling duct that provides structural support and directs cooling airflow, and a second portion (outer portion) extending beyond the duct that generates thrust. This segmentation allows each portion to be optimized for its specific function while working together as an integrated system.
Solution Approach 2:
The first portion of the rotor blades serves multiple functions simultaneously: it provides structural support for the second portion, directs cooling airflow over the engine, and contributes to thrust generation. This multi-functionality resolves the contradiction by eliminating the need for separate structural and cooling components, maintaining compact design while preventing thrust losses.
2Temperature
If a long crankshaft is used to increase spacing between the fan and engine, then cooling airflow is improved, but system weight increases
Solution Approach 1:
Instead of increasing spacing in the axial dimension (which would require a long crankshaft and increase weight), the solution creates a radial dimension for cooling airflow by forming a duct between concentric nacelles. The rotor blades extend radially into this duct, providing cooling airflow in the radial direction while maintaining compact axial spacing.
3Volume of moving object
If a short duct is used between the fan and engine, then the design remains compact, but airflow separation occurs and drag increases
Solution Approach 1:
The rotor blades have different geometries and pitches in different radial zones. The first portion (within the duct) has optimized geometry for directing cooling airflow and minimizing separation, while the second portion (outside the duct) has geometry optimized for thrust generation. This local quality variation prevents airflow separation in the compact duct while maintaining overall compact design.
Data Source
AI summary
A system for cooling a ducted fan aircraft engine includes a first nacelle surrounding the engine and a second nacelle substantially concentrically surrounding the first nacelle. The system includes a first spinner coupled around a base of a rotor of the ducted fan and a second spinner substantially concentrically surrounding the first spinner and forming a duct between first and second spinners. The second spinner includes an opening to allow air to flow into the duct. The rotor includes a plurality of airfoils penetrating through the first and second spinners. Each of the airfoils includes a first portion located in the duct, and a second portion located between the second spinner and a fuselage of the ducted fan. The first portions of the airfoils provide cooling airflow over the engine and structural support for the second portions. The second portions of the airfoils provide thrust for the aircraft.