Optical Sensor Combustor Control for Fuel-Air Uniformity
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Solution Overview
Problem
Current technologies face challenges in achieving combustion uniformity in multi-nozzle combustors, such as turbine engines, due to limited optical access and the inability of existing sensors to effectively monitor fuel/air ratios across varying zones, leading to inefficiencies, damage, and emissions issues.
Innovation Solution
A system utilizing passive optical sensors co-located with fuel nozzles to measure radiation in multiple spectral bands, allowing for fuel flow modulation to achieve uniform combustion by determining the fuel/air ratio in each combustor segment and adjusting fuel distribution accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If passive optical sensors are placed at the combustor exit to monitor combustion properties, then measurement of flow-path conditions is enabled, but optical access is limited and sensor placement flexibility is reduced
Solution Approach 1:
The combustor is divided into multiple zones with different fuel/air ratios, and optical sensors are placed at the front end to view through specific combustion zones. Each zone's emission characteristics are monitored separately, enabling precise measurement while providing flexibility in sensor placement locations.
Solution Approach 2:
Optical radiation serves as an intermediary medium to transmit information from the combustion zones to the sensors. By detecting emission from intermediate species and soot in different spectral bands, the system enables remote measurement without direct contact with the hot flow path, maintaining both measurement precision and operational flexibility.
2Measurement precision
If spectral bands CH (0.43 microns) and C2 (0.52 microns) are used for fuel/air ratio sensing, then detection capability is provided for premixed natural gas combustors, but these bands are overwhelmed by soot emission in high fuel/air ratio combustors
Solution Approach 1:
The system changes the spectral parameter by selecting different wavelength bands appropriate for different combustor types. For rich-burn combustors with high soot emission, UV bands (0.2-0.4 microns) are selected where soot emission is minimal, while for lean-premixed combustors, visible bands (CH, C2) are used. This parameter adaptation resolves the interference issue.
Solution Approach 2:
Different spectral bands are assigned to different combustion zones based on their local characteristics. UV bands monitor the rich primary zone where soot precursors emit, while avoiding bands where soot would dominate. This local optimization of spectral selection eliminates interference while maintaining detection precision.
3Reliability
If intensity-based optical sensors are used to monitor flame presence, then flame detection is enabled, but the sensed signal is not proportional to fuel/air ratio over full operating range
Solution Approach 1:
The system transitions from monitoring total intensity to monitoring spectral distribution parameters. By measuring intensity ratios across multiple spectral bands (UV, visible, IR) and analyzing the spectral shape, the system obtains parameters that are proportional to fuel/air ratio across the full operating range, while maintaining reliable flame detection.
Solution Approach 2:
The measurement approach moves from a single intensity dimension to multiple spectral dimensions. By collecting emission data across the electromagnetic spectrum and analyzing spectral characteristics rather than just total intensity, the system extracts fuel/air ratio information that is proportional over the full range while preserving flame detection capability.
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 approach enables effective control of combustion uniformity across a range of fuel/air ratios, reducing variations and improving efficiency, lifetime, and emissions performance by providing a proportional output for active control of fuel flow.
Implementation Method 1
An optical sensor collects naturally occurring optical radiation from the hot flow stream and determines the state of combustion within a volume defined by the sensor field of view
Implementation Method 2
A transducer compares radiation in a plurality of spectral bands and determines the fuel/air ratio
Data Source
AI summary
A system for controlling the uniformity of combustion over a range of operating conditions in a combustor with a plurality of fuel nozzles. The system includes a number of optical sensors, each sensor comprising an optical probe that collects naturally occurring optical radiation emanating from a segment of the combustor or combustor exhaust, and at least one transducer that receives the radiation collected by the probes, compares the intensity of collected radiation from each sensor in a plurality of spectral pass-bands that are indicative of the fuel/air ratio in the combustor segments, and produces output signals that are indicative of the state of combustion in the combustor segments. A control system receives the output signals from the transducers and in response controls the fuel flow to the fuel nozzles to achieve an output from each of the sensors that has been determined to be indicative of a predetermined state of combustion.