Impeller Blade Mistuning for Resonance Suppression
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Solution Overview
Problem
Existing impeller designs in turbomachinery face challenges in controlling resonance response amplification due to random mistuning, especially in wide operating ranges like aircraft engines, where the desired advantage of reduced vibration is not consistently achieved.
Innovation Solution
The impeller design incorporates a rotatable hub with blades arranged in an alternating pattern of first and second blades, each with distinct vibrational eigenvalues, ensuring a mistune distribution that avoids Fourier components with wave numbers twice the nodal diameter number, thereby suppressing resonance response amplification across notable rotational orders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If blades are designed with small thickness to reduce weight and increase efficiency, then weight reduction and efficiency improvement are achieved, but the risk of damage due to high cycle fatigue increases
Solution Approach 1:
The patent changes the vibrational eigenvalue parameter of specific blades (making them different from the common value) to alter the resonance response characteristics of the entire blade set, thereby reducing fatigue damage risk while maintaining thin blade design for weight reduction
2Object-affected harmful factors
If intentional mistuning is applied to reduce resonance response amplification, then vibration reduction is achieved in specific resonance conditions, but the effectiveness is limited to defined blade configurations and operating conditions
Solution Approach 1:
The patent applies local quality by assigning different vibrational eigenvalues to specific blades (first blades with first eigenvalue, second blades with second eigenvalue) rather than uniform mistuning, creating localized variations that collectively reduce resonance response across multiple operating conditions
Solution Approach 2:
The patent introduces asymmetry by deliberately creating non-uniform distribution of blade vibrational eigenvalues, where certain blades have different eigenvalues from others, breaking the symmetry of the tuned system to reduce resonance amplification across various rotational orders
3Object-affected harmful factors
If conventional intentional mistuning strategies are used to lower resonance amplification factor below 1.0, then response reduction is achieved at two nodal diameter mode and rotational secondary harmonic frequency, but unexpected response amplifications may occur due to harmonic resonance induced by stationary blades
Solution Approach 1:
The patent changes the vibrational eigenvalue parameter of specific blades to create a mistune distribution that addresses multiple resonance conditions simultaneously, including harmonic resonances induced by stationary blades, rather than optimizing for a single resonance condition
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 effectively suppresses the increase in resonance response amplification factor during harmonic resonance of notable rotational orders, regardless of the impeller's configuration or vibration modes, thereby enhancing durability and reducing vibration.
Implementation Method 1
the resonance response amplification factor (AF) of each blade may differ from one another
Implementation Method 2
blade vibration response and intentional mistuning are greatly dependent on the blade configuration and aerodynamic conditions during impeller operation
Data Source
AI summary
In an impeller comprising a rotatable hub and a plurality of blades provided circumferentially on the rotatable hub at regular intervals, the blades including first blades each having a first vibrational eigenvalue and second blades each having a second vibrational eigenvalue, the first blades and the second blades are circumferentially arranged with a predetermined regularity in a circumferential direction in an alternating manner and with a mistune distribution that does not include a mistune component having a wavenumber twice a number of nodal diameters computed fromH+ND=nN where H is a rotational order of resonance under harmonic forced vibration, ND is a nodal diameter number in a traveling wave mode, n is an integer and N is a number of the blades.