Dual Rotor Vibration Monitoring Phase Clocking
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Solution Overview
Problem
Conventional vibration monitoring methods in dual rotor gas turbine engines, such as the unducted fan (UDF) turbofan engine, struggle to distinguish the separate vibratory responses of counterrotating low pressure turbine (LPT) rotors operating at the same frequency, making it difficult to accurately balance the engines and prevent undesirable noise.
Innovation Solution
A new frequency analysis method involving the measurement of first and second total vibrations, relative phase clocking of the rotors, and subsequent resolution of unbalances at a common response frequency to determine corrective balance weights for each rotor, allowing for precise balancing of the dual rotor system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional vibration monitoring methods are used in dual rotor engines, then the measurement process is simple, but the ability to distinguish separate vibratory responses of counterrotating rotors is lost
Solution Approach 1:
The patent segments the combined vibration signal into individual rotor contributions by analyzing vibrations at different rotational phases. The method separates the vibratory responses of the first and second counterrotating rotors by measuring total vibration at multiple phase positions (0°, 90°, 180°, 270°) and mathematically resolving the individual unbalance components from the composite signal.
Solution Approach 2:
The patent employs periodic measurement sampling at specific rotational phases of the rotors. By taking vibration measurements at discrete phase intervals during rotor rotation and using these periodic samples to compute unbalance parameters, the method enables distinction between rotors operating at the same frequency through phase-dependent signal variation.
2Ease of manufacture
If single-plane balancing is applied to the entire engine, then the balancing process is simplified, but the ability to individually balance each rotor is reduced
Solution Approach 1:
The patent divides the single-plane balancing approach into separate balancing procedures for each rotor. By measuring vibrations at multiple rotational phases and resolving the unbalance components mathematically, the method enables individual unbalance determination for the first rotor and second rotor, allowing separate balance weight applications while maintaining procedural simplicity.
Solution Approach 2:
The patent introduces phase angle measurements as an intermediary parameter to bridge between the simple single-plane measurement approach and the need for individual rotor unbalance determination. The phase-dependent vibration measurements serve as intermediate data that, when processed through the resolution algorithm, yield separate unbalance values for each rotor.
3Ease of operation
If balance corrections are applied at accessible stages only, then the balancing procedure is easier to implement, but the precision of unbalance correction at inaccessible stages is reduced
Solution Approach 1:
The patent uses the accessible rotor (with applied balance weights) as an intermediary to indirectly determine and correct unbalance in the inaccessible rotor. The vibration measurements taken after balancing the accessible rotor provide phase-dependent information that allows calculation of the inaccessible rotor's unbalance, enabling precise correction without direct access.
Solution Approach 2:
The patent replaces the need for direct mechanical access to both rotors with a field-based measurement and calculation system. Instead of physically balancing both rotors directly, the method uses vibration field measurements and mathematical resolution to determine and guide balance corrections for both rotors, substituting mechanical accessibility requirements with computational analysis.
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
Enables continuous monitoring and balancing of dual rotor engines by resolving individual rotor unbalances, reducing vibration and noise, and maintaining optimal propulsion efficiency.
Implementation Method 1
a vibration sensing accelerometer is installed in the engine at any suitable location for detecting vibrations or vibratory response of the engine
Data Source
AI summary
Vibration is monitored in a dual rotor engine. A first total vibration of the engine is measured during operation. Relative phase of the two rotors is then clocked, and a second total vibration of the engine is then measured during operation. First and second total unbalances are then resolved at a common response frequency from the measured total vibrations. First and second rotor unbalances are then resolved for the corresponding rotors from the first and second total unbalances. In a further method, corresponding corrective balance weights may be determined for offsetting the resolved rotor unbalances.