Multistage Compressor Tie Rod Thermal Management
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Solution Overview
Problem
Multi-stage compressors with stack rotor configurations experience high thermal stresses due to temperature gradients between the tie rod and impellers during startup, leading to potential malfunctioning and reduced compressor lifespan.
Innovation Solution
A multi-stage compressor design that incorporates a return flow path allowing compressed gas to flow along the tie rod, utilizing forced convection to transfer heat generated during compression and reduce temperature gradients between the tie rod and impellers, thereby heating the tie rod faster and minimizing thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stack rotor configuration with tie rod is used to hold impellers together, then the structural integrity and assembly simplicity are improved, but high thermal stresses occur during startup due to temperature gradients between the tie rod and impellers
Solution Approach 1:
A thermal management system is introduced as an intermediary between the impellers and the surrounding environment. This system includes cooling channels or heat exchange pathways that facilitate controlled heat transfer, acting as a mediator to reduce temperature gradients and thermal stresses during operation.
Solution Approach 2:
The thermal parameters of the system are dynamically managed by introducing cooling pathways. The temperature distribution is actively controlled by allowing heat to be conducted away from the impellers through designated channels, changing the thermal state from uncontrolled heating to managed thermal equilibrium.
2Device complexity
If the tie rod is isolated from direct gas flow, then gas sealing is simplified, but the tie rod heats up slower than the impellers, increasing temperature gradients
Solution Approach 1:
Cooling channels are introduced as intermediary pathways that enable controlled thermal interaction. These channels serve as mediators between the gas flow and the tie rod, allowing indirect thermal management without compromising the sealing integrity of the direct gas path.
Solution Approach 2:
The thermal management is achieved by adding a new dimension to the system architecture - internal cooling channels or heat exchange pathways within or around the tie rod assembly. This dimensional addition allows thermal control without interfering with the primary gas flow path.
3Stability of the object's composition
If clearance is maintained between the tie rod and impellers, then thermal expansion is accommodated, but gas leakage occurs from the compression path to the clearance
Solution Approach 1:
The harmful gas leakage path is extracted or removed from the system by providing sealing elements that close off the clearance between the tie rod and impellers. The sealing mechanism extracts the leakage pathway, allowing the clearance to remain for thermal expansion while preventing gas escape.
Solution Approach 2:
Sealing elements are introduced as intermediary components between the compression path and the clearance space. These seals act as mediators that allow thermal expansion movement while maintaining gas tightness, separating the thermal management function from the gas containment function.
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 solution effectively reduces thermal gradients and extends the compressor's lifespan by ensuring the tie rod is heated uniformly, enhancing operational stability and reliability during startup.
Implementation Method 1
A multi-stage compressor design that incorporates a return flow path allowing compressed gas to flow along the tie rod, utilizing forced convection to transfer heat generated during compression
Implementation Method 2
heat generated by compressing the fluid processed by the compressor
Data Source
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AI summary
A multi-stage compressor (10) is described, comprising a rotor (1 1) having a plurality of axially stacked impellers (12; 12B, 12) and a tie rod (14) extending through the stacked impellers and holding the impellers together. A gas compression path (P) extends from a compressor inlet to a compressor outlet and through the impellers. A flow channel (17) is provided between the tie rod (14) and the stacked impellers (12, 12A, 12B). The flow channel develops along at least a portion of the tie rod (14). Hot gas is diverted from the compression path (P) and flows through the flow channel to heat the tie rod during startup of the compressor.