Turbomachine Control System for Combined Cycle Efficiency and Life
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Solution Overview
Problem
Turbomachinery systems, particularly gas turbines with bottoming cycles, face reduced lifespan and efficiency due to high firing temperatures, which lead to shorter life of combustion parts and lower combined cycle efficiency, necessitating a control method to manage firing temperatures effectively.
Innovation Solution
A model-based control system that derives a constant efficiency load path by determining a firing temperature reduction set point using non-linear analysis and sensor data, allowing for dynamic generation of load path curves that balance part life and efficiency, considering constraints like CO, LBO, and NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high firing temperature is used to satisfy emissions and combustion requirements, then combustion system performance is improved, but turbomachine system life is shortened
Solution Approach 1:
The patent implements dynamic load paths that adjust firing temperature based on operating conditions and time. The system transitions from static high-temperature operation to dynamic temperature management, where the firing temperature is modulated along predetermined trajectories that balance performance requirements with thermal stress accumulation, thereby extending component life while maintaining combustion effectiveness.
Solution Approach 2:
The patent changes the firing temperature parameter from a constant high value to a time-varying parameter following specific load paths. By implementing minimum load paths and constant efficiency load paths, the system varies the firing temperature to reduce thermal stress on components while maintaining sufficient combustion performance, directly addressing the contradiction between high temperature operation and component longevity.
2Stability of the object's composition
If high firing temperature is used to meet combustion dynamics requirements, then combustion stability is improved, but turbine exhaust temperature increases
Solution Approach 1:
The patent employs dynamic load paths that modulate firing temperature to maintain combustion stability while controlling exhaust temperature. By following constant efficiency load paths, the system dynamically adjusts the temperature profile to preserve combustion dynamics requirements without allowing exhaust temperature to rise excessively, thus resolving the contradiction between combustion stability and exhaust temperature control.
3Temperature
If water is sprayed into superheater and reheater steam circuits to maintain steam temperature within design limits, then steam temperature control is improved, but HRSG pressure parts life is shortened
Solution Approach 1:
The patent applies preliminary action by reducing the firing temperature at the source through dynamic load paths, thereby preventing excessive steam temperature generation in the first place. This upstream temperature control eliminates or reduces the need for downstream water spraying in the superheater and reheater, thus protecting HRSG pressure parts from thermal shock and extending their service life while maintaining steam temperature within design limits.
4Reliability
If high firing temperature is used to satisfy emissions requirements, then emissions compliance is improved, but combined cycle efficiency is lowered
Solution Approach 1:
The patent changes the firing temperature parameter from a constantly high value to a dynamically adjusted parameter following constant efficiency load paths. By optimizing the temperature profile over time, the system maintains emissions compliance through sufficient peak temperatures while reducing overall energy losses, thereby improving combined cycle efficiency compared to sustained high-temperature operation.
Data Source
AI summary
Systems and methods for improved control of a turbomachine system with a bottoming cycle system are presented. The systems and methods include a controller that utilizes modeling techniques to derive a plurality of load path curves. The controller utilizes a current load path, a minimum load path, and a constant efficiency load path. The systems and methods include a control process configured to receive a user input representative of a life cycle control modality and to execute a control action based on deriving a load efficiency by applying the current load path, the minimum load path, the constant efficiency load path, or a combination thereof, and the life cycle control modality. The control action is applied to control the turbomachine system and the bottoming cycle system fluidly coupled to the turbomachine system. Further, the life cycle control modalities may be selected by a user based upon known tradeoffs.