Centrifugal Compressor Inlet Duct Swirl Generators
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Solution Overview
Problem
The operating range of conventional turbochargers with centrifugal compressors is limited by surge and choke phenomena, leading to performance issues across a wide range of operating conditions, and existing solutions like casing treatment and variable inlet guide vanes either increase complexity and cost or merely shift the operating range without extending it effectively.
Innovation Solution
A modified inlet duct with guide means that induces swirl in the flow adjacent to the tips of the impeller blades, directing the flow in the direction of rotation without disturbing the axial flow near the hub, thereby reducing the maximum mass flow rate at which surge occurs and minimizing throttling effects, thus widening the stable operating range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable inlet guide vanes are used to control flow angle, then the operating range can be shifted, but the device complexity and cost increase due to active control requirements
Solution Approach 1:
The inlet duct is segmented into different functional zones: a first portion with guide means that induces swirl adjacent to blade tips, and a second portion that maintains axial flow near the hub. This segmentation allows different flow conditions in different regions, extending the operating range without requiring active control mechanisms.
Solution Approach 2:
The guide means is positioned to affect only specific local regions of the flow (adjacent to blade tips) while leaving other regions (near the hub) undisturbed. This localized flow control achieves operating range extension without the need for complex global control systems.
2Reliability
If casing treatment with recirculation channels is used, then surge mass flow rate decreases, but device complexity and cost increase
Solution Approach 1:
The invention extracts the essential function of swirl induction from the complex casing treatment system and implements it directly in the inlet duct geometry. By taking out the swirl generation function and integrating it into the inlet duct, the patent achieves surge resistance improvement without adding complex recirculation channels or swirl vanes.
3Reliability
If guide means induce swirl in the entire flow, then surge mass flow rate decreases, but choke mass flow rate also decreases due to throttling effect
Solution Approach 1:
The guide means is designed to induce swirl only in specific local regions (adjacent to blade tips) while maintaining axial flow in other regions (near the hub). This localized approach reduces the incidence angle at blade tips to prevent surge, while preserving sufficient mass flow rate for choke conditions.
Solution Approach 2:
The flow domain is segmented into two distinct regions with different flow characteristics: a outer region with induced swirl for surge prevention, and an inner region with axial flow for maintaining mass flow rate. This segmentation resolves the contradiction between surge resistance and productivity.
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 increases the stability of the compressor by reducing the incidence angle of the flow onto the impeller blade tips, reducing the surge mass flow rate while maintaining the minimum choke mass flow rate, thereby extending the operating range without adding complexity or cost.
Implementation Method 1
guide means arranged to guide the flow to induce swirl in the flow adjacent tips of the blades, the direction of swirl being the direction of rotation of the blades
Implementation Method 2
centrifugal compressor with inlet and an impeller with a hub and blades
Implementation Method 3
the compressor is unable to force fluid against the pressure gradient on either side of its blades
Data Source
AI summary
A centrifugal compressor is disclosed. The centrifugal compressor comprises an inlet and an impeller comprising a hub and blades. The inlet is for conveying flow to the impeller comprising guide means and is arranged to guide the flow through the inlet to induce swirl in the flow adjacent tips of the blades, the direction of swirl being the direction of rotation of the blades, without substantially disturbing flow adjacent the hub.