Gas Turbine Fuel Composition Determination via Flow Discrepancy
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Solution Overview
Problem
Gas turbines face performance issues due to uncompensated variations in fuel composition, leading to combustion instabilities, increased emissions, and reduced flameholding margin, as existing methods for determining fuel composition are costly, slow, or undesirable for control purposes.
Innovation Solution
A method and system that determines the fuel composition by calculating the temperature and pressure of fuel entering the combustor, using aero-thermal cycle models and fuel nozzle effective area to estimate total fuel flow, and adjusts machine controls based on performance parameters to compensate for changes in fuel composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement of fuel composition is used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses an intermediary calculation approach where fuel composition is not measured directly but inferred through mathematical relationships between measurable parameters (fuel flow rate, temperature, pressure) and fuel properties (heating value, density). This mediator methodology avoids complex direct measurement devices while achieving composition determination through the relationship: fuel composition changes affect heating value, which in turn affects the balance between measured fuel flow and cycle model predicted fuel flow.
Solution Approach 2:
The patent replaces mechanical/physical direct measurement systems with a computational/model-based approach. Instead of using physical sensors to directly measure fuel composition, the system substitutes a mathematical model (aero-thermal cycle model) that calculates fuel composition indirectly from readily available operational parameters, thereby eliminating the need for complex measurement hardware.
2Measurement precision
If direct measurement of fuel composition is used, then measurement precision is improved, but response speed deteriorates
Solution Approach 1:
The system performs preliminary calculations by continuously maintaining an aero-thermal cycle model that is pre-configured with fuel property relationships. When fuel composition changes occur, the model can immediately recalculate the expected fuel flow based on current operating conditions, providing rapid response without waiting for slow direct measurement processes. The model is prepared in advance with all necessary thermodynamic relationships to enable instant composition inference.
Solution Approach 2:
The patent substitutes slow physical measurement processes with rapid computational calculations. The mathematical model can evaluate fuel composition changes in real-time based on standard sensor inputs (flow, temperature, pressure), achieving response speeds limited only by computational capacity rather than physical measurement constraints.
3Device complexity
If fuel composition variation is uncompensated, then device complexity is reduced, but performance deteriorates
Solution Approach 1:
The patent implements a feedback control mechanism where the calculated fuel composition (or heating value) is continuously fed back to the control system. This feedback enables real-time adjustments to combustion parameters (air-fuel ratio, ignition timing, fuel injection rate) to compensate for composition variations, thereby maintaining combustion stability and performance without requiring overly complex hardware modifications.
Solution Approach 2:
The system responds to fuel composition changes by dynamically adjusting operational parameters such as fuel flow rate, air intake, and combustion chamber conditions. When the model detects heating value changes indicative of composition variation, it modifies control parameters to maintain optimal combustion, effectively adapting the system behavior to compensate for fuel variability.
Data Source
AI summary
Disclosed is a method and system for determining composition of a fuel entering a combustor. The method includes determining a temperature of the fuel entering the combustor, calculating a first estimated total fuel flow utilizing fuel properties and fuel nozzle effective area (Ae), and calculating a second estimated total fuel flow utilizing an aero-thermal cycle model analysis. The first estimated total fuel flow is compared to the second estimated total fuel flow and a lower heating value of the fuel is determined from a difference between the first estimated total fuel flow and the second estimated total fuel flow. A method and system for controlling a gas turbine includes calculating effects of the fuel composition on performance of the gas turbine and comparing one or more performance parameters to one or more parameter limits. One or more machine controls of the gas turbine are changed based on the results of the comparison.