Tandem Stator Flow Recirculation for Compressor Stall
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Solution Overview
Problem
Tandem stator designs in gas turbine compressors face challenges in achieving acceptable performance and operating range, especially at off-design conditions, due to flow distortions and physical constraints such as engine weight and compressor length.
Innovation Solution
A method involving the extraction of airflow at two different locations within the compressor, forming a mixed recirculation flow, which is then re-injected upstream of the tandem stator rows to improve flow momentum and reduce end wall flow deficiencies, utilizing a flow recirculation system with specific conduit configurations to equalize pressures and prevent flow reversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If tandem stator rows are used in compressors with very high pressure ratios, then high flow turning and high Mach number flow are achieved, but large distortions in flow occur at off-design conditions
Solution Approach 1:
The patent extracts a portion of the main airflow from two different locations within the compressor gaspath and separates it from the main flow. This extracted flow is then recirculated back upstream to counteract adverse flow conditions, effectively removing the distorted flow components and replacing them with healthier flow characteristics.
Solution Approach 2:
The patent implements a feedback mechanism by extracting flow from downstream locations and recirculating it back to upstream locations. This creates a closed-loop system where flow characteristics are continuously adjusted by feeding back corrected flow from downstream to upstream, stabilizing the flow field and reducing distortions at off-design conditions.
2Length of moving object
If physical constraints on engine weight and overall compressor length are imposed, then engine weight and compressor length are reduced, but stator length, number of stators, and gas path size are restricted
Solution Approach 1:
The patent utilizes the radial dimension by extracting flow from two different radial locations and combining them in a recirculation path. This three-dimensional approach to flow management allows the system to achieve better flow control without increasing the axial length of the compressor, effectively using the radial and circumferential dimensions to compensate for the constrained axial space.
Solution Approach 2:
The recirculation system serves multiple functions simultaneously: it reduces flow distortions, controls boundary layer characteristics, manages secondary flows, and improves overall compressor performance. This multi-functional approach allows a single system to address multiple performance issues without requiring separate devices, thereby avoiding additional length and weight penalties.
3Reliability
If flow is extracted at two different locations and recirculated upstream, then compressor performance and stall range are enhanced, but device complexity increases
Solution Approach 1:
The patent combines two separate flow extraction streams from different locations into a single recirculation conduit that delivers mixed flow back to the upstream location. This merging approach allows the system to achieve the benefits of multiple extraction points while using a unified recirculation path, reducing the complexity that would result from entirely separate recirculation loops for each extraction point.
Solution Approach 2:
The recirculation conduit acts as an intermediary element that connects downstream extraction points to upstream injection points. This intermediary structure facilitates the transfer and mixing of flows between different locations in the compressor, enabling complex flow control functions through a relatively simple intermediate component rather than requiring direct modifications at multiple locations.
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
Enhances compressor performance and stall range by re-energizing the inlet end wall boundary layer and reducing secondary flows, particularly beneficial at off-design conditions where large flow distortions occur.
Implementation Method 1
extracting a first portion of the main airflow from a first location proximate radially inner roots of stators of the first or second stator rows; extracting a second portion of the main airflow from a second location proximate the radially inner roots of the stators of the first or second stator rows, the second location downstream of the first location relative to the main airflow; combining the first and second portions together to form a mixed recirculation flow; and re-injecting the recirculation flow back into the main airflow at a third location, the third location upstream of the first and second locations
Implementation Method 2
re-energizing the inlet end wall boundary layer and reducing secondary flows, particularly beneficial at off-design conditions where large flow distortions occur
Data Source
AI summary
A method of operating a compressor of a gas turbine engine is described which includes directing a main airflow through tandem stator rows in a gaspath of the compressor, extracting a first portion of the main airflow from a first location proximate radially inner roots of stators of the first or second stator rows, extracting a second portion of the main airflow from a second location proximate the radially inner roots of the stators of the first or second stator rows, the second location being downstream of the first location relative to the main airflow, and re-injecting the combined extracted flow back into the main airflow at a third location. The third location is located upstream of the first and second locations, and is upstream of a leading edge of stators of the first stator row.