Turbine Blade Root Recesses for Resonant Frequency Control
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Solution Overview
Problem
Turbine rotor blades often fail to meet resonant frequency requirements due to vibrational excitations from rotational speed and hot gas, leading to unacceptable vibrations, and existing methods for adjusting mass distribution can impair structural integrity and aerodynamics.
Innovation Solution
Introducing recesses or reducing dimensions at the blade root or platform underside of turbine rotor blades, specifically in sacrificial regions, to adjust mass distribution without affecting structural integrity or aerodynamics, allowing for precise control of resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mass is reduced from the blade airfoil to adjust resonant frequency, then vibrational properties are improved, but structural integrity and aerodynamic performance deteriorate
Solution Approach 1:
The patent applies local quality by creating recesses specifically in sacrificial regions (blade root and platform underside) that have different functional requirements compared to the blade airfoil. These regions are designed to be non-load-critical and non-aerodynamic, allowing localized mass reduction without compromising overall structural integrity or aerodynamic performance while still achieving the desired resonant frequency adjustment.
Solution Approach 2:
The patent shifts the mass adjustment from the traditional one-dimensional approach of reducing blade airfoil mass to a three-dimensional approach by utilizing the sacrificial regions at the blade root and platform underside. This dimensional shift allows mass redistribution in locations that do not affect the critical aerodynamic surfaces or load-bearing paths, thereby resolving the contradiction between vibrational property improvement and structural integrity maintenance.
2Duration of action of stationary object
If protective layers are applied to increase lifetime, then corrosion and thermal protection are improved, but vibrational behavior deteriorates
Solution Approach 1:
The patent applies preliminary action by adjusting the resonant frequency through recesses in sacrificial regions before the protective layers are applied. This sequence ensures that the base structure's vibrational properties are optimized first, and then the protective layers are added without requiring subsequent vibrational adjustments, thereby maintaining both extended lifetime from protection and reliable vibrational behavior.
Solution Approach 2:
The patent effectively discards the sacrificial regions (blade root and platform underside) as non-critical mass that can be removed without affecting performance, and recovers the vibrational properties by creating controlled recesses in these discarded areas. This allows protective layers to be applied for lifetime extension while the sacrificial regions absorb the mass adjustment needed for optimal vibrational behavior.
3Reliability
If turbine rotor blades are designed with high resonant frequency to avoid vibration, then operational reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the resonant frequency parameter through controlled mass reduction in sacrificial regions. By changing the mass parameter in non-critical areas (blade root and platform underside), the resonant frequency is adjusted to achieve operational reliability without requiring complex design modifications to the critical blade airfoil geometry or structure, thereby avoiding increased manufacturing complexity.
Data Source
AI summary
A method for producing turbine rotor blades or the base bodies thereof includes a) providing the base body, which has, following one another along a longitudinal axis, a blade root, a blade platform and a blade airfoil, b) sensing a value of at least one parameter of the base body, at least one of the parameters representing a vibrational property of the base body, c) comparing the sensed value with a predetermined target interval, d) if the sensed value lies outside the target interval, reducing the mass of the base body, wherein the reduction of the mass takes place at the blade root and/or on the blade platform by introducing at least one recess and/or by reducing a dimension below the corresponding target value.