Single-Shaft Combined Cycle Retrofit With Hydraulic Axial Compensation
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Solution Overview
Problem
In single shaft combined cycle power plants, replacing the gas turbine part while maintaining operational integrity is challenging due to thermal expansion, which requires precise axial displacement compensation between the gas and steam turbine rotors, often necessitating continued cooperation with the original manufacturer to avoid axial clearance issues.
Innovation Solution
A method involving the removal of the old gas turbine part and tie rods, installation of a new gas turbine part with a thrust bearing and hydraulic unit, and a controller to enable stepless axial displacement of the gas turbine rotor relative to the stator, monitored by measuring devices to maintain axial clearance within limits, independent of the steam turbine rotor's displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the gas turbine part is replaced with a new design, then modernization and improved performance are achieved, but axial clearance issues arise due to thermal expansion incompatibility with the existing steam turbine part
Solution Approach 1:
The patent applies the dynamics principle by making the gas turbine stator movable along the axial direction through a hydraulic actuator system. This allows the stator position to be dynamically adjusted in response to thermal expansion variations, enabling compatibility between different gas turbine designs and the existing steam turbine part while maintaining proper axial clearances during operation
Solution Approach 2:
The patent introduces a hydraulic actuator system as an intermediary mechanism between the gas turbine stator and the fixed structure. This intermediary device mediates the thermal expansion differences between the gas and steam turbine parts by providing controlled axial movement of the stator, thus resolving the incompatibility issue when replacing gas turbine parts
2Reliability
If pin-ended supports and tie rods are used to compensate axial displacements, then axial clearance is maintained, but manufacturer dependency increases and replacement flexibility is reduced
Solution Approach 1:
The patent replaces the traditional mechanical compensation system (pin-ended supports and tie rods) with a hydraulic actuator system. This substitution eliminates the need for complex mechanical linkages and allows for easier replacement of gas turbine parts, as the hydraulic system can be integrated with the new design without requiring matching compensation mechanisms
Solution Approach 2:
The hydraulic actuator system serves multiple functions: it compensates for thermal expansion, maintains axial clearances, and enables compatibility with different gas turbine designs. This multi-functional approach replaces the specialized pin-ended support and tie rod system, providing both reliability and replacement flexibility
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 solution allows for the replacement of gas turbine parts without manufacturer dependency, ensuring continuous operation by dynamically adjusting the gas turbine rotor's position to match thermal expansions, thereby maintaining acceptable axial clearances and preventing damage.
Implementation Method 1
a hydraulic unit acting on the thrust bearing and a controller designed for controlling the hydraulic unit
Implementation Method 2
During the operation of such a combined cycle power plant the intermediate shaft undergoes a thermal expansion, which leads to an axial displacement of the steam turbine rotor
Data Source
AI summary
A method for modifying an existing single shaft combined cycle power plant having a steam turbine part and a gas turbine part which are connected to each other rigidly by an intermediate shaft. The gas turbine part is supported by two pin-ended supports allowing a certain axial displacement of the casing by rotating about corresponding axes. The old gas turbine part is replaced by a new gas turbine part having a different structure, namely a rigid support and a flexible support. Relative thermal expansion or displacement of the intermediate shaft is compensated by a hydraulic unit comprising a double-acting piston for displacing the gas turbine rotor with respect to the gas turbine stator. The hydraulic unit is controlled based on a displacement measurement in the steam turbine.