Variable-Pitch Blade Assembly with Inclined Rotation Axis
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Solution Overview
Problem
Turbomachine blades with variable geometric pitch face challenges in controlling drag and torque, especially during take-off, due to the high mass of counterweights required to counteract inertia, which also experience centrifugal loads, making them difficult to control and inefficient.
Innovation Solution
The blades are designed with a tilt component relative to the propeller plane, featuring a tangential and upstream/downstream inclination, with a fixed axis of rotation, incorporating a cardan joint and bellows or universal joint to adjust the blade pitch, reducing the need for heavy counterweights by optimizing the center of gravity and restoring moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If counterweights are added to return blades to flag position, then blade control and drag reduction are improved, but the mass of the blade assembly increases significantly
Solution Approach 1:
The patent applies counterweights integrated into the blade structure to automatically return blades to the flag position (perpendicular to propeller plane) during windmilling or engine failure. The counterweights are positioned to exploit centrifugal force, creating a restoring moment that rotates the blade to the desired orientation without active control systems.
Solution Approach 2:
The blade design incorporates predetermined geometric features including inclined rotation axes and specific center of gravity positions. These preliminary geometric configurations ensure that when the engine fails or during windmilling, the blades automatically assume the correct flag position through gravity and centrifugal force, without requiring real-time control intervention.
2Stability of the object's composition
If counterweights are added to counteract blade inertia, then blade stability is improved, but the centrifugal load on rotating structures increases
Solution Approach 1:
The patent distributes mass non-uniformly within the blade structure by positioning counterweights at specific locations along the blade span and integrating them into the blade anatomy rather than adding them as separate external components. This local quality optimization reduces the overall centrifugal load while maintaining the necessary restoring moment for stability.
Solution Approach 2:
The counterweights are integrated within the blade structure itself, nested into the blade anatomy rather than being external add-ons. This integration allows the counterweight mass to be part of the overall blade mass calculation, optimizing the distribution to reduce centrifugal loads on the hub and rotating structures while maintaining blade stability.
3Reliability
If heavy counterweights are used to control blade pitch, then blade return to flag position is ensured, but the overall device mass increases by approximately 100 kg per motor
Solution Approach 1:
The patent optimizes the mass, position, and distribution of counterweights to achieve the minimum necessary mass for reliable blade pitch control. By carefully calculating and positioning the center of gravity and counterweight locations, the design achieves dependable automatic blade return to flag position with significantly reduced counterweight mass compared to conventional designs.
Solution Approach 2:
Rather than using excessive counterweight mass to ensure blade control, the patent applies the minimum necessary counterweight mass achieved through optimized geometric positioning. The inclined rotation axes and specific center of gravity locations create mechanical advantage, allowing partial action (smaller counterweights) to achieve the same reliability as excessive action (larger counterweights) would provide in conventional designs.
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 design reduces drag and torque, allowing for more efficient operation by halving the mass of counterweights, improving mechanical and aerodynamic performance, and reducing lift and drag, while maintaining stability and acoustic conditions.
Implementation Method 1
the rotating structures of the propeller or blower are subjected to the centrifugal load of these counterweights
Implementation Method 2
the blades 2 tend, due to their inertia, to adopt a pitch of 0° relative to the plane of rotation of the propeller
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A variable-pitch vane comprising: - a plurality of propeller blades (2), each being of variable pitch according to a blade rotational axis (A1) and each having a root (201), - a plurality of rotor connecting shafts (6), each shaft having a foot (602) and a head (601), the root (201) of each blade being mounted on the head (601) of a rotor connecting shaft via a pivot (8) in such a way as to allow each blade (2) to rotate according to the blade rotational axis (A1), in which each blade (2) has a blade pitch, such that the blade rotational axis (A-i) of same is inclined relative to a radial axis (A2) passing through the foot (602) of the corresponding shaft.