HRSG Structural Array for Gas Turbine Exhaust Diffusion
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Solution Overview
Problem
High exhaust gas velocities from gas turbines cause flow-induced vibrations and reduced heat transfer effectiveness in HRSGs, leading to potential damage and inefficiency due to non-uniform velocities and high aerodynamic loading on heat transfer tubes.
Innovation Solution
A structural array of grate-like panels is placed upstream of the HRSG tubes, diffusing the high velocity exhaust stream and redistributing gas flow, secured to structural elements to withstand the forces and allow for thermal expansion, with adjustable mounts for optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the HRSG is located close to the gas turbine to minimize plant area and duct size, then the area required for the power plant is reduced, but high velocity gas jet impacts the front rows of heat transfer tubes causing flow-induced vibrations and potential damage
Solution Approach 1:
A structural array is introduced as an intermediary component between the gas turbine exhaust diffuser and the HRSG front tube rows. This array diffuses the high-velocity exhaust stream, reducing the jet velocity and aerodynamic loading before the gas reaches the heat transfer tubes, thereby preventing flow-induced vibrations while allowing close coupling of the HRSG to the gas turbine
Solution Approach 2:
The structural array consists of multiple discrete structural components or panels arranged in a grate-like configuration. This segmentation allows the array to effectively diffuse the exhaust stream while maintaining structural integrity under high aerodynamic loading, and enables the array to be positioned optimally between the gas turbine and HRSG
2Ease of operation
If flow controls are placed in the diverging duct to redirect flow and improve distribution, then flow distribution to front tube rows is improved, but the flow controls are subjected to very high aerodynamic loadings and thermal stress making long-term operation unlikely
Solution Approach 1:
The flow control function is extracted from the diverging duct environment and relocated to the HRSG inlet region. The structural array is positioned where it is exposed to lower aerodynamic loadings and more stable thermal conditions, while still achieving the desired flow diffusion and distribution effect on the front tube rows
Solution Approach 2:
The structural array is designed with sufficient structural strength and stiffness to withstand the aerodynamic loadings it will encounter, and is positioned to allow thermal expansion. The array acts as a pre-diffuser that cushions the high-velocity jet before it reaches the heat transfer tubes, protecting them from vibration damage
3Productivity
If a grate-like structure is placed at a fixed distance upstream of the heat exchanger, then flow diffusion is achieved, but the structure cannot adapt to thermal expansion and optimization requirements
Solution Approach 1:
The structural array is designed with adjustable mounts that allow the distance between the array and the HRSG front tube rows to be modified. This dynamic positioning capability enables optimization of the diffusion effect for different operating conditions and accommodates thermal expansion of the HRSG and supporting structures during operation
Solution Approach 2:
The adjustable mounts allow the position parameter of the structural array to be changed relative to the HRSG. This enables optimization of the array-to-tube distance to achieve the desired flow diffusion and heat transfer effectiveness, while also accommodating thermal expansion and contraction of the system components
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
The structural array effectively reduces flow-induced vibrations and improves heat transfer by diffusing the exhaust stream, minimizing damage and enhancing the distribution of gas flow, thereby increasing the reliability and efficiency of the HRSG system.
Implementation Method 1
A structural array of grate-like panels is placed upstream of the HRSG tubes, diffusing the high velocity exhaust stream and redistributing gas flow
Implementation Method 2
The high aerodynamic loading on the tube banks can also cause movement of the entire front tube bank resulting in damage to components in and around the tube bank
Implementation Method 3
thermal stress due to going from ambient temperature to the high gas turbine exhaust temperature
Data Source
Figure 1
Figure 2
Figure 3a~4b
AI summary
A heat recovery steam generator ("HRSG") (40), which is closely coupled to a gas turbine, includes a flow controls structural array (10) disposed upstream of the tubes (42) of the HRSG (40). The structural array (10) is formed of a plurality of grate-like panels (18) secured to horizontal supports (24) mounted to the support structure of the HRSG (40). The structural array (10) diffuses the high velocity exhaust stream (14) exiting the gas turbine and redistributes the gas flow evenly throughout the HRSG (40). The structural array (10) reduces wear and damage of the tubes (46).