Diffuser Vane Bleed Ports for Gas Turbine Surge Margin
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Solution Overview
Problem
Centrifugal compressors in gas turbine engines face challenges in controlling and delaying the onset of surge, a condition that results from increased incidence of fluid flow on diffuser vanes leading to stall and static pressure increase, with existing solutions being inadequate.
Innovation Solution
A diffuser design for centrifugal impeller assemblies in gas turbine engines featuring angled passages with bleed ports that recirculate air from downstream to the inlet space upstream of the leading edges, increasing the surge margin by reducing flow incidence and diffusion, thereby delaying surge conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bleed ports are added to recirculate air upstream of leading edges, then surge margin is improved, but device complexity increases
Solution Approach 1:
The bleed ports are integrated directly into the diffuser vanes themselves, merging the surge control function with the existing diffuser structure. This eliminates the need for separate surge control components and reduces overall device complexity while still achieving the desired surge margin improvement through passive recirculation of air upstream of the leading edges.
Solution Approach 2:
The system uses passive recirculation where bleed ports automatically redirect air flow upstream of the leading edges based on pressure differentials without requiring external control mechanisms. The diffuser structure itself serves the dual purpose of diffusion and surge control, making the system self-regulating and reducing complexity.
2Reliability
If bleed ports are positioned downstream of leading edges, then flow incidence is reduced, but loss of energy increases
Solution Approach 1:
The bleed ports are positioned to extract air upstream of the leading edges where the flow has not yet incurred significant losses. By recirculating this relatively high-energy air back to the inlet space, the system reduces flow incidence on the vanes before stall conditions develop, preventing energy loss associated with stall and surge while minimizing the energy extracted through the bleed ports.
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 diffuser design effectively delays surge conditions by recirculating air through bleed ports, reducing flow incidence and diffusion, and maintaining efficiency during normal operations by minimizing bleed flow recirculation, thus enhancing the surge margin and operational stability.
Implementation Method 1
the diffuser case including a passive fluid communication defined at least partially through each vane between the corresponding bleed port and the inlet space upstream of the leading edges
Data Source
AI summary
A diffuser for a centrifugal impeller assembly of a gas turbine engine includes a diffuser case having a plurality of vanes extending therein defining a plurality of circumferentially distributed angled passages in communication with an inlet space. Each vane includes a bleed port defined in a suction surface thereof, in proximity of the leading edge. The diffuser case includes a passive fluid communication defined at least partially through each one of the vanes between each bleed port and the inlet space upstream of the leading edge, such that air bled through the bleed ports is recirculated upstream of the leading edges to the inlet space to increase a surge margin of the diffuser.