Gas Turbine Burner Pilot-Air Ratio Control
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Solution Overview
Problem
Existing techniques for controlling the operating point of combustion systems in gas turbines often result in fluctuations in pilot-fuel supply, leading to higher temperatures and emissions, as they rely heavily on altering the pilot-fuel/main-fuel ratio, which can be disadvantageous and inefficient.
Innovation Solution
The method involves controlling the pilot-air/pilot-fuel ratio to regulate the operating point of the combustion system by introducing pilot-air either premixed with pilot-fuel or through separate injection holes, allowing for precise adjustment of combustion characteristics without solely relying on changes in pilot-fuel amounts, thereby navigating the system away from undesired operational regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing techniques control operating point by altering pilot-fuel/main-fuel ratio, then the operating point can be adjusted, but fluctuations in pilot-fuel supply occur leading to higher temperatures and emissions
Solution Approach 1:
The patent changes the control parameter from pilot-fuel flow rate to pilot-air flow rate. By introducing pilot-air supply with controllable flow rate and adjusting the pilot-air/pilot-fuel ratio, the system achieves operating point adjustment without fluctuating pilot-fuel supply, thereby reducing temperature variations and emissions while maintaining adaptability.
Solution Approach 2:
The patent introduces pilot-air as an intermediary substance between pilot-fuel and the combustion process. Instead of directly controlling pilot-fuel flow, the system uses pilot-air to modulate the combustion characteristics, allowing operating point adjustment while stabilizing pilot-fuel supply and reducing harmful emissions.
2Stability of the object's composition
If pilot-fuel supply is increased to control operating point, then combustion stability is improved, but temperatures increase leading to higher emissions
Solution Approach 1:
The patent changes the control approach by introducing pilot-air flow rate as the adjustable parameter instead of increasing pilot-fuel supply. By controlling the pilot-air/pilot-fuel ratio, the system achieves combustion stability through improved mixing and flame anchoring while maintaining lower combustion temperatures and reducing emissions.
Solution Approach 2:
The patent uses pneumatic introduction of pilot-air into the combustion zone to stabilize combustion. The pressurized pilot-air stream provides flame anchoring and improves combustion stability without requiring increased pilot-fuel flow, thereby controlling combustion temperature and reducing thermal emissions.
3Speed
If pilot-fuel/main-fuel ratio is altered frequently to navigate operating point, then response to load fluctuations is improved, but system dynamics become unstable
Solution Approach 1:
The patent changes the dynamic control parameter from pilot-fuel flow to pilot-air flow. By adjusting pilot-air flow rate in response to load changes while keeping pilot-fuel supply stable, the system achieves fast response to load fluctuations without disrupting combustion dynamics stability, as the pilot-fuel/main-fuel ratio remains constant.
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 stable operation within desired regions, reducing the risk of high temperatures and emissions, and extends the lifespan of combustion system components by maintaining optimal combustion dynamics.
Implementation Method 1
A combustion system (1) for a gas turbine... having a combustion volume (28)... The pilot-fuel and the pilot-air are provided to the burner... via either a plurality of pilot-fuel holes (3) and a plurality of pilot-air holes (5) or a mix of pilot-fuel and the pilot-air
Data Source
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AI summary
A method for controlling pilot-fuel/pilot-air ratio provided to a burner of a combustion system for altering its operating point is presented. First, a value of a first parameter e.g. temperature, is checked, and if the value equals or exceeds a predetermined maximum limit of the first parameter that places the operating point in a first undesired region of operation, then a pilot-fuel/pilot-air ratio is altered such that the value of first parameter is moved to below the first parameter's predetermined maximum limit. Similarly, a value of a second parameter e.g. pressure, is checked, and if the value equals or exceeds a predetermined maximum limit of the second parameter that places the operating point in a second undesired region of operation, then again the pilot-fuel/pilot-air ratio is altered such that the value of second parameter is moved to below the second parameter's predetermined maximum limit. A combustion system is also presented.