Device and Method for Radial Gap Measurement with Millimeter Waves

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This invention relates to a device and method for measuring the radial gap between turbine blades and the housing wall using millimeter wave technology. Unlike previous capacitive or microwave-based systems that only provide an average gap measurement, this invention enables high-resolution profiling of each blade edge as it passes. It uses continuous millimeter waves emitted and received by a sensor within the housing, with the precise distance between the blade edge and housing determined via phase analysis of the reflected waves. Advanced focusing—either algorithmic (synthetic aperture radar, SAR) or optical (using a lens)—is used to achieve local resolution down to the fine structures of blade edges.

Use CasesContent extracted from patent full text and abstract with AI.

• Real-time monitoring of radial clearances in gas or steam turbines during operation to prevent collisions and optimize efficiency.
• Detection and assessment of turbine blade edge wear, damage, or structural changes (e.g., due to erosion or rotor shift).
• Adaptive control systems in power plants to automatically adjust operating parameters based on live turbine gap measurements.
• Preventive maintenance planning by providing detailed data on changes in the blade's profile or positioning.
• Quality assurance during turbine manufacturing or repair to verify gap profiles per design specifications.

BenefitsContent extracted from patent full text and abstract with AI.

• Provides high lateral (spatial) resolution, allowing detection of detailed blade edge features—such as sealing lips or holes—that integral measurements would miss.
• Enables continuous, real-time monitoring under harsh thermal and operating conditions where optical sensors might fail.
• Reduces the need for large safety clearances, potentially increasing turbine efficiency and power output.
• Decreases or eliminates the need for reference measurements or extensive calibration, simplifying installation and maintenance.
• Offers robust performance independently of prior knowledge of blade geometry or variations in rotor position.

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Inventors & Applicants

Patent Abstract

The method involves continuously transmitting millimeter wave by a transmitter and receiver unit (60) accommodated in a region of a housing wall (100) of a turbine housing (10). The millimeter wave reflected at a radial outer edge (30) is received by the transmitter and receiver unit. A profile of the outer edge is detected in direction of movement of a turbine blade (20) by subsequent focusing with help of numeric process. The distance between a blade edge and the housing wall is determined by a phase analysis of the received millimeter wave.