Outlet Guide Vane Constriction for Turbine Flow Acceleration
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Solution Overview
Problem
Existing outlet guide vanes in gas turbines are deceleration vanes, leading to inefficient flow deflection and increased pressure losses, which limits the deflection of the flow and results in undesired separations.
Innovation Solution
An outlet guide grid with a constriction arranged closer to the trailing edge of the guide vane than the downstream end of the outer wall, combined with a core flow nozzle, transforms the exit guide grid into an acceleration grid, improving pressure distribution and reducing losses, allowing for higher flow acceleration and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If outlet guide vanes are designed as deceleration vanes in known gas turbines, then the flow deflection is limited, but pressure losses increase and undesired flow separations occur
Solution Approach 1:
The patent inverts the conventional design approach by transforming the outlet guide vane from a deceleration vane into an acceleration vane. This is achieved by positioning a constriction (core flow nozzle) downstream of the guide vane trailing edge, which accelerates the flow rather than decelerating it. This inversion resolves the technical contradiction by enabling strong flow deflection while avoiding the pressure losses and flow separations that plague conventional deceleration vane designs.
Solution Approach 2:
The patent changes the flow velocity parameter from deceleration to acceleration by modifying the downstream geometry. The constriction is positioned at a specific distance from the guide vane trailing edge, creating an acceleration zone that transforms the flow characteristics. This parameter change enables the outlet guide vane to deflect flow strongly without incurring the harmful effects of deceleration, thus resolving the contradiction between flow deflection capability and pressure losses.
2Speed
If the constriction is positioned closer to the trailing edge of the guide vane, then flow acceleration is improved, but the risk of flow separation increases
Solution Approach 1:
The patent applies preliminary action by positioning the constriction at an optimized distance downstream of the guide vane trailing edge. This distance is carefully selected to allow the flow to be properly conditioned by the guide vane before entering the acceleration zone created by the constriction. The preliminary conditioning of the flow prevents separation while enabling strong acceleration, thus resolving the contradiction between flow acceleration and flow separation risk.
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
This configuration reduces pressure losses and enables stronger flow acceleration, enhancing the overall efficiency of the low-pressure turbine and potentially shortening the engine length, making it lighter.
Implementation Method 1
At least one cross-sectionally reducing constriction (38) is arranged between the leading edge (E) of the guide vane (32) and the downstream end (35) of the outer wall (34). The constriction (38) is arranged closer to the trailing edge (H) than to the downstream end (35) of the outer wall (34). By combining the outlet guide vane with the core flow nozzle, the outlet guide vane becomes an acceleration vane
Data Source
Figure 1
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AI summary
The invention relates to an outlet guide grid with an outer wall (34'), an inner wall (36') for forming an annular channel (22) and for guiding the hot gas flow, and with at least one guide vane (32) arranged between the outer wall (34') and the inner wall (36'), wherein at least one cross-sectionally reducing constriction (38') is arranged between the leading edge (E) of the guide vane (32) and the downstream end (35') of the outer wall (34'). At least one absolute constriction (38') in the region between the leading edge (E) and the downstream end (35') is arranged closer to the trailing edge (H) of the guide vane (32) than to the downstream end (35').