Self-Aspirated Flow Control for Centrifugal Compressors
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Solution Overview
Problem
Centrifugal compressors face flow destabilization and reduced pumping capability below the stall point due to boundary layer flow separation, leading to aerodynamic inefficiencies, and traditional solutions like increasing compression stages or duct lengths result in increased dimensions and costs.
Innovation Solution
A self-aspirated flow control system with suction and blowing holes in the diffuser and interconnecting ducts, coupled via a manifold, and enhanced by fluidic oscillators for pulsed blowing, stabilizes fluid flow by recirculating boundary layer fluid to prevent separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of compression stages or length of interconnecting transition ducts is increased to reduce pressure gradients and prevent boundary layer flow separation, then compressor stability and aerodynamic efficiency are improved, but the overall dimensions and number of parts increase
Solution Approach 1:
The invention extracts and removes the problematic boundary layer fluid from the diffuser through suction holes, preventing it from causing flow separation. This targeted removal addresses the stability issue without requiring additional compression stages or extended duct lengths, thereby maintaining compact compressor dimensions while improving reliability.
Solution Approach 2:
The invention introduces a flow control stream as an intermediary substance that is injected through blowing holes into the interconnecting ducts. This flow control stream acts as a mediator to suppress boundary layer growth and prevent flow separation, achieving improved compressor stability without increasing the physical dimensions of the compressor.
2Loss of energy
If the radius of 180-degree bend portions or number of turning vanes is increased to reduce pressure losses in interconnecting ducts, then aerodynamic efficiency is improved, but the overall dimensions and cost increase
Solution Approach 1:
The invention extracts the boundary layer fluid that causes flow separation and pressure losses before it can significantly develop in the interconnecting ducts. By removing this problematic fluid through suction holes in the diffuser, pressure losses are reduced without requiring larger bend radii or additional turning vanes, maintaining compact dimensions while improving aerodynamic efficiency.
3Adaptability or versatility
If traditional flow control methods are used to prevent boundary layer flow separation, then compressor operational range is extended, but device complexity and number of components increase
Solution Approach 1:
The invention merges the flow control functionality directly into the existing diffuser and interconnecting duct structures by integrating suction holes in the diffuser and blowing holes in the ducts. This integration approach extends the operational range while minimizing additional components, as the flow control system utilizes the existing structural elements rather than adding separate dedicated components.
Solution Approach 2:
The system utilizes the compressor's own boundary layer fluid, suctioned from the diffuser, and redirects it through the manifold to the blowing holes for flow control. This self-service approach uses resources already present in the system, avoiding the need for external fluid sources or additional complex control mechanisms, thereby extending operational range while maintaining simplicity.
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 system stabilizes fluid flow, enhances aerodynamic performance, and extends the compressor's operational range by suppressing stalling mechanisms, offsetting thermodynamic penalties with aerodynamic gains and improved diffusion control.
Implementation Method 1
a first pressure in the high pressure diffuser is higher than a second pressure in a low pressure interconnecting duct, so that the pressure difference results in self-aspiration of a flow control fluid through a manifold
Implementation Method 2
The corresponding blowing into the low pressure interconnecting duct energizes the weak flow along a surface in the low pressure interconnecting duct and suppresses boundary layer separation in the low pressure interconnecting duct
Implementation Method 3
A fluidic oscillator is provided juxtaposed to the blowing holes and configured to facilitate pulsed blowing of the flow control stream into the boundary layer fluid in the first interconnecting duct via the blowing holes
Data Source
AI summary
A flow control system for a centrifugal compressor includes a plurality of suction holes provided in a diffuser and configured to facilitate suction of a flow control stream from a boundary layer fluid from the diffuser. A plurality of blowing holes are provided in a first interconnecting duct coupled to a de-swirl vane unit and configured to facilitate blowing of the flow control stream into the first interconnecting duct. The blowing holes may also be provided in a suction side or an end wall side of the de-swirl vane unit or in a second interconnecting duct coupled between the de-swirl vane unit and an impeller or an upstream diffuser of another compression stage. A manifold is coupled between the suction holes and the blowing holes and configured to direct flow of the flow control stream from the suction holes to the blowing holes.