Titanium Compressor Wheel Frequency Ratio Design
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Solution Overview
Problem
Current compressor wheels, particularly those made of aluminum, fail to withstand the stresses of high pressure ratios and high RPM, leading to unacceptably short operating life and high maintenance costs due to high cycle fatigue (HCF) and low cycle fatigue (LCF) failures, limiting their efficiency and aerodynamic performance.
Innovation Solution
A titanium compressor wheel design with a frequency ratio of natural frequency-to-maximum rotational speed less than 4.0, utilizing a titanium alloy with superior damping capacity, results in thinner blades and a less complex shape, enhancing aerodynamic efficiency and reducing the risk of HCF failure while maintaining operational life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If aluminum compressor wheels are used, then weight is reduced and cost is lower, but operating life is unacceptably short due to HCF and LCF failures
Solution Approach 1:
The patent changes the material parameter from aluminum to titanium alloy, which fundamentally alters the mechanical properties including strength, damping capacity, and fatigue resistance. This material substitution enables the compressor wheel to withstand high cycle fatigue and low cycle fatigue conditions that cause premature failure in aluminum wheels, thereby extending operating life and improving reliability.
Solution Approach 2:
The patent employs titanium alloy as a composite material solution that combines multiple desirable properties: high strength-to-weight ratio, superior damping capacity, and exceptional fatigue resistance. The specific titanium alloy composition is selected to optimize both the durability against HCF/LCF failures and the aerodynamic performance requirements of the compressor wheel.
2Reliability
If blade frequency ratio is increased to avoid HCF failure, then reliability improves, but aerodynamic efficiency decreases due to thicker blades
Solution Approach 1:
The patent changes the blade frequency ratio parameter from the conventional >4.0 to less than 4.0 by utilizing the superior damping capacity of titanium alloy. This parameter inversion is made possible because titanium's inherent damping properties provide HCF protection without requiring increased blade thickness, thereby maintaining optimal aerodynamic efficiency while achieving reliable HCF failure resistance.
Solution Approach 2:
The patent applies local quality optimization by using titanium alloy specifically in the blade regions where damping capacity is most critical for HCF resistance, while maintaining blade geometry optimized for aerodynamic efficiency. The material's localized damping properties protect against vibration-induced fatigue without requiring global blade thickening that would compromise airflow and efficiency.
3Strength
If titanium alloy is used, then strength and damping capacity improve, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the material parameter to titanium alloy, accepting the associated increases in manufacturing complexity and cost as necessary trade-offs for achieving the required strength and damping capacity. The design optimizes the blade geometry and frequency ratio to minimize material usage while maximizing the beneficial properties of titanium, thereby controlling manufacturing complexity.
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 titanium compressor wheel design achieves improved efficiency, longer operational life, and reduced maintenance costs by withstanding exacerbated HCF conditions, allowing for higher flows and efficiencies at the same speed, while also reducing heat load and backpressure on the engine.
Implementation Method 1
utilizing a titanium alloy with superior damping capacity
Data Source
AI summary
A compressor wheel (20) for an air boost device and a method for designing the wheel are provided. The compressor wheel (20) comprises a hub (24) and a plurality of blades (22, 23) connected to the hub (24). The plurality of blades (22, 23) have a ratio (f/N) of natural frequency to maximum rotational speed of less than 4.0 and are made from a titanium alloy. The plurality of blades (22, 23) can comprise a plurality of full blades (22) and a plurality of splitter blades (23).