Propeller Drive Torsion Damping for Start-Up Resonance Control
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Solution Overview
Problem
Aircraft propeller drive systems experience stress, wear, noise, and vibration due to the varying speed of the crankshaft, leading to resonance issues during engine start-up, which can affect engine control and successful start-up.
Innovation Solution
Incorporating a torsion bar with a hydraulic damper system that provides varying degrees of damping to mitigate torsion angle variations, connected to a clutch for smooth torque transmission and reducing resonance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the propeller drive system is designed with high stiffness to avoid resonance during normal operation, then resonance is avoided during most operating conditions, but strong vibrations and crankshaft reverse rotation occur during engine start-up when passing through resonance frequency
Solution Approach 1:
The patent applies dynamic principles by making the torsional stiffness of the propeller drive system variable rather than fixed. The system is designed to have high stiffness during normal operation to avoid resonance, and low stiffness during start-up to pass through resonance frequencies smoothly. This is achieved through components that can adapt their mechanical properties based on operating conditions, allowing the system to transition between different stiffness states.
Solution Approach 2:
The patent changes the physical parameters of the propeller drive system, specifically the torsional stiffness parameter. By varying the stiffness parameter from high (during normal operation) to low (during start-up), the system can avoid resonance during cruising while safely passing through resonance frequencies during engine acceleration. This parameter change allows the natural frequency of the system to shift, preventing resonant conditions.
2Power
If the propeller drive system uses rigid connections between gears and shafts, then power transmission is efficient, but stress and wear of gears increase due to speed variations between crankshaft and propeller
Solution Approach 1:
The patent employs flexible elements in the form of torsion bars that act as elastic connections between the rigid gear components. These flexible elements allow relative motion and absorb speed variations between the crankshaft and propeller, preventing direct transmission of stress impulses to the gears while maintaining efficient power transmission. The flexible torsion bars accommodate the speed differences without causing excessive wear to the gear teeth.
Solution Approach 2:
The propeller drive system combines rigid components (gears, shafts) with flexible components (torsion bars) to create a composite structure. This composite approach allows the system to maintain the high efficiency of rigid power transmission while incorporating the shock-absorbing and stress-distributing properties of flexible elements, thereby protecting the gears from excessive stress and wear.
3Object-affected harmful factors
If the propeller drive system is designed with low stiffness to reduce vibrations during start-up, then resonance effects are minimized, but the system becomes more susceptible to resonance during normal operation
Solution Approach 1:
The patent implements a dynamic stiffness system that automatically adjusts its mechanical properties based on the operating regime. During engine start-up, the system presents low stiffness to allow smooth passage through resonance frequencies. During normal operation, the system transitions to high stiffness to maintain stability and avoid resonance. This dynamic adaptation is achieved through the interaction of elastic torsion bars with the rigid gear train, creating a system whose effective stiffness varies with operating conditions.
Solution Approach 2:
The patent applies preliminary anti-action by pre-designing the torsional flexibility of the drive system to counteract resonance effects before they occur during start-up. The elastic elements are configured to naturally reduce the system's stiffness at low speeds, preventing resonant vibrations from developing in the first place during engine acceleration, rather than attempting to correct them afterward.
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
The solution effectively dampens torque peaks and reduces resonance-related vibrations, ensuring stable engine operation and successful start-up by managing torsion angle changes and torque variations.
Implementation Method 1
a hydraulic damper operatively connected between the output shaft and the first end of the torsion bar to dampen at least some variations in torsion angle of the torsion bar
Implementation Method 2
a torsion bar having a first end and a second end opposite the first end, the first end adapted to be operatively connected to and driven by the engine about a torsion axis, the second end being rotatable relative to the first end about the torsion axis by a torsion angle
Data Source
AI summary
An aircraft propeller drive system for an aircraft is disclosed. The aircraft has a propeller driven by an intermittent combustion internal combustion engine via the propeller drive system. The propeller drive system has: a torsion bar having a first end and a second end opposite the first end, the first end being adapted to be operatively connected to and driven by the engine about a torsion axis, the second end being rotatable relative to the first end about the torsion axis by a torsion angle; an output shaft rotationally fixedly connected to and driven by the second end of the torsion bar, the output shaft being adapted for being connected to the propeller; and a hydraulic damper operatively connected between the output shaft and the first end of the torsion bar to dampen at least some variations in torsion angle of the torsion bar.