Tiltrotor Spinner Cutout Alignment for Drag Reduction
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Solution Overview
Problem
Current spinner configurations on tiltrotor aircraft experience significant drag due to freestream airflow entering rotor blade cutouts, leading to ram, momentum, and profile drag, with existing solutions adding weight, cost, and complexity.
Innovation Solution
The design features an elongated spinner with rotor blade cutouts oriented parallel to freestream airflow at the cylindrical aft portion, reducing airflow into the inner chamber and using diverter brows to divert airflow away from cutouts, thereby minimizing drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rotor blade cutouts are formed in conventional spinner configurations, then rotor blades can flap and move in various directions, but freestream airflow enters the inner chamber through cutouts creating ram drag, momentum drag, and profile drag
Solution Approach 1:
The spinner is elongated in the longitudinal dimension, with cutouts positioned at the rear portion rather than distributed throughout. This dimensional repositioning aligns cutouts with the airflow direction, allowing blades to flap while minimizing airflow entry into the inner chamber, thus reducing drag while preserving blade movement capability
Solution Approach 2:
The spinner geometry is optimized locally at the cutout region by positioning them at the rear portion of the elongated spinner. This local repositioning ensures that the cutouts are aligned with freestream airflow, reducing the harmful effect of airflow entry while maintaining the necessary blade articulation space
2Stress or pressure
If current spinner shapes are used, then air pressure is at a maximum near the cutouts, but this leads to high air velocity and increased dynamic pressure near cutouts, further increasing drag
Solution Approach 1:
By elongating the spinner in the longitudinal dimension and positioning cutouts at the rear, the design changes the pressure distribution pattern along the airflow path. The elongated shape allows pressure to dissipate before reaching the cutouts, reducing peak dynamic pressure and velocity effects that would otherwise increase drag
3Object-affected harmful factors
If previous techniques for reducing cutout-induced drag, such as sliding seals, are used, then drag is reduced, but reliability and maintenance are compromised and weight, cost and complexity increase
Solution Approach 1:
The invention extracts and eliminates the need for complex sealing mechanisms like sliding seals by using a simpler geometric solution - an elongated spinner with rear-positioned cutouts aligned with airflow. This removes unnecessary components while maintaining drag reduction, thereby simplifying the design and improving reliability
Solution Approach 2:
The design replaces complex, maintenance-intensive sealing systems with a simple, robust geometric configuration that is inherently easier to manufacture and maintain. The elongated spinner with aligned cutouts provides a durable, low-complexity solution that avoids the reliability issues of mechanical seals
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 drag by aligning rotor blade cutouts with airflow, shielding shanks from freestream airflow, and optimizing airflow pressure, resulting in lower air velocity and pressure adjacent to cutouts without increasing weight or complexity.
Implementation Method 1
The rotor blade cutouts are formed at the substantially cylindrical aft portion of the spinner to reduce the freestream airflow into the inner chamber via the rotor blade cutouts during forward flight
Implementation Method 2
thereby reducing drag experienced by the tiltrotor aircraft
Implementation Method 3
using diverter brows to divert airflow away from cutouts
Implementation Method 4
optimizing airflow pressure, resulting in lower air velocity and pressure adjacent to cutouts
Data Source
AI summary
A proprotor assembly for a tiltrotor aircraft having a forward flight mode. The proprotor assembly includes a spinner subjected to freestream airflow during forward flight. The spinner is elongated to form a tapered leading portion and a substantially cylindrical aft portion. The spinner forms a plurality of rotor blade cutouts exposing an inner chamber. The proprotor assembly includes a plurality of proprotor blade assemblies protruding radially from the spinner through the rotor blade cutouts. The rotor blade cutouts are formed at the substantially cylindrical aft portion of the spinner to reduce the freestream airflow into the inner chamber via the rotor blade cutouts during forward flight, thereby reducing drag experienced by the tiltrotor aircraft.