Acoustic Combustor Temperature Measurement
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Solution Overview
Problem
Existing methods for measuring temperature inside a combustor are limited by the difficulty in obtaining precise, real-time data due to the harsh conditions and inhomogeneous temperature distributions, especially when relying on passive acoustic measurements.
Innovation Solution
An active and controllable acoustic source and receiver system is used to emit and detect acoustic signals within a specific frequency band, allowing for precise determination of gas temperature at a particular axial position by measuring the resonance frequency, enabling real-time monitoring and adaptation to different combustor types and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If passive acoustic measurement is used to monitor gas temperature, then the measurement system is simple, but the precision and significance of temperature determination is strongly limited due to inhomogeneous temperature distribution and inability to perform real-time control
Solution Approach 1:
The patent applies active acoustic excitation with dynamically adjustable frequency and amplitude, allowing the measurement system to adapt to changing combustion conditions in real-time. The acoustic source is modulated to track resonance frequencies, enabling precise temperature determination despite inhomogeneous temperature distributions in the combustor.
Solution Approach 2:
The patent utilizes acoustic resonance vibrations of the combustor cavity to enhance temperature measurement precision. By exciting the combustor at its resonance frequencies and measuring the response, the system achieves high-precision temperature determination that overcomes the limitations of passive acoustic measurement.
2Measurement precision
If passive acoustic spectrum measurement is used, then the measurement method is simple, but the highest power level occurs at locations with strongly inhomogeneous temperature distribution, causing measured temperature to deviate from flame temperature
Solution Approach 1:
The system dynamically adjusts the acoustic excitation frequency to track the resonance frequency of the combustor. This dynamic adaptation allows the measurement to be performed at optimal locations and conditions, ensuring that the measured temperature accurately reflects the flame temperature even in regions with complex flow patterns.
Solution Approach 2:
The patent implements a feedback mechanism where the acoustic response is continuously monitored and used to adjust the excitation frequency. This closed-loop control ensures that measurements are always taken at the resonance frequency, maximizing temperature measurement accuracy and eliminating deviations caused by inhomogeneous temperature distributions.
3Productivity
If spatially averaged temperature measurement over resonance cavity is used, then the measurement system is simple, but dynamic temperature measurements and real-time control of combustor are not possible
Solution Approach 1:
The patent divides the combustor into multiple measurement sections by placing acoustic sources and receivers at different axial positions. This segmentation enables independent temperature measurement at each location, providing spatially resolved temperature data that supports dynamic control while maintaining manageable system complexity through modular configuration.
Solution Approach 2:
The system performs preliminary acoustic excitation and resonance frequency determination before actual temperature measurement. This preliminary action establishes the resonance characteristics of the combustor, enabling subsequent rapid temperature measurements and real-time control without requiring complex real-time frequency analysis during operation.
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 method provides high precision and reliability in determining gas temperature in real-time, with a high time resolution of up to 50 Hz, allowing for effective control of combustor operations and simultaneous monitoring of temperatures at multiple axial locations.
Implementation Method 1
emitting an acoustic signal from an acoustic source, the acoustic signal having a frequency which is within a frequency band that comprises one resonance frequency of the gas in the combustor
Implementation Method 2
determine the actual temperature of the gas at a particular axial position based on the actual resonance frequency of the gas
Data Source
AI summary
A method for determining the temperature of an aggressive and/or abrasive gas is described using an acoustic transmitter and an acoustic receiver. The transmitter emits an acoustic signal with varying frequencies and the receiver extracts from the acoustic input signal a frequency of the maximum. Based on this the frequency of this maximum the temperature of the gas between transmitter and receiver is calculated.