Turbine Inlet Guide Vane Stall Avoidance
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Solution Overview
Problem
Gas turbines experience significant off-design aerodynamic conditions during start-up and shutdown, leading to rotating stall, which causes high vibratory stresses and premature blade failures due to resonance, resulting in increased maintenance costs and downtime.
Innovation Solution
A method involving the use of inlet guide vanes and bleed valves to limit the duration of rotating stall by shifting the stall window to higher rotational speeds and modulating the inlet guide vane positions to minimize exposure to the stall window during start-up and shutdown, allowing blades to pass through it briefly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas turbines operate during start-up and shutdown, then the turbine can complete necessary operational cycles, but rotating stall occurs causing high vibratory stresses and premature blade failures
Solution Approach 1:
The patent applies dynamics by making the inlet guide vane angle variable during start-up and shutdown operations. Instead of maintaining a fixed geometry, the IGV angle is dynamically adjusted based on rotational speed to keep the operating point outside the rotating stall window. This dynamic geometric adaptation allows the turbine to complete operational cycles while avoiding the harmful resonant conditions that cause blade failures.
2Reliability
If variable stage geometry is increased to avoid off-design aerodynamic conditions, then rotating stall can be reduced, but device complexity increases
Solution Approach 1:
The patent applies local quality by modifying only the inlet guide vane geometry and operation, rather than redesigning the entire variable stage geometry system. The IGV angle is adjusted locally at the inlet to influence the entire flow field and prevent rotating stall. This localized modification achieves improved aerodynamic performance during transient operations without the complexity of comprehensive stage geometry changes.
3Reliability
If air extractions are increased to manage off-design conditions, then aerodynamic stability improves, but loss of substance increases
Solution Approach 1:
The patent applies parameter changes by modifying the inlet guide vane angle parameter during start-up and shutdown to prevent rotating stall. Instead of extracting air to manage off-design conditions, the IGV angle is adjusted to maintain favorable aerodynamic parameters that keep the operating point outside the rotating stall window. This parameter adjustment achieves aerodynamic stability without the substance loss associated with air extraction.
Data Source
Figure 1~2
Figure 3
AI summary
A method of starting up a turbine with a compressor (10) have an inlet guide vane (20), a number of bleed valves (40), and a number of blades (30) so as to avoid a rotating stall window (50). The method may include starting rotation of the blades (30), increasing the speed of the rotation of the blades (30), closing one or more bleed valves (40) so as to shift the rotating stall window (50) to a higher rotational speed, partially opening the inlet guide vane (20) to a position outside the rotating stall window (50), and opening the bleed valves (40) while partially closing the inlet guide vane (20) so as to pass through the rotating stall window (50).