Asymmetric Exhaust Hood Diffuser for Steam Turbine Backflow Reduction
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Solution Overview
Problem
Existing steam turbines experience pressure loss and backflow issues due to asymmetric diffuser configurations, leading to reduced performance.
Innovation Solution
The design includes an exhaust hood with a diffuser that features a bearing cone and flow guide with a cylindrical shape extending axially, where the diameter widens downstream, and the end edges are shaped to create an oval cross-section, allowing for improved fluid flow and reduced pressure loss by eliminating backflow regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an asymmetric diffuser configuration is used to reduce exhaust loss, then exhaust loss is reduced, but backflow occurs in the vicinity of the bearing cone on the opposite exhaust side
Solution Approach 1:
The patent applies asymmetry by configuring the bearing cone with different semi-vertical angles on the exhaust side and the side opposite to the exhaust side. Specifically, the semi-vertical angle on the exhaust side is made smaller than that on the opposite side, creating an asymmetric geometry that optimizes flow patterns while preventing backflow in the bearing cone region
Solution Approach 2:
The patent applies local quality by varying the geometric parameters of the bearing cone locally across different circumferential positions. The semi-vertical angle is specifically adjusted on the exhaust side compared to the opposite side, allowing each region to have optimized characteristics for its specific flow conditions
2Device complexity
If a conventional diffuser is used, then the structure is simple, but delamination occurs in the flow guide on the exhaust side
Solution Approach 1:
The flow guide is configured with asymmetric geometry where the semi-vertical angle differs between the exhaust side and the opposite side. This asymmetric design prevents delamination on the exhaust side by optimizing the flow attachment characteristics in that specific region
Solution Approach 2:
The flow guide employs local quality by applying different geometric parameters to different circumferential regions. The semi-vertical angle is locally optimized on the exhaust side to prevent delamination, while maintaining appropriate geometry elsewhere
3Area of stationary object
If the bearing cone diameter is increased, then the flow area is improved, but the diffuser length increases
Solution Approach 1:
The patent applies asymmetry by using different semi-vertical angles for the bearing cone on the exhaust side versus the opposite side. This allows the flow area to be optimized without uniformly increasing the diffuser length, as the geometric expansion is distributed differently across the circumferential direction
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 enhances the pressure recovery performance and reduces pressure loss, thereby improving the overall efficiency of the steam turbine.
Implementation Method 1
The diffuser disposed on a downstream side of the inner casing to form a diffuser space communicating with the first space, is oriented radially outward as going toward the downstream side, and allows the first space and the second space to communicate with each other
Implementation Method 2
The diffuser... is oriented radially outward as going toward the downstream side... allows the first space and the second space to communicate with each other
Data Source
AI summary
An exhaust hood (Ec) of the present invention is provided with an inner casing (21), an outer casing (30), and a diffuser (26). The inner casing (21) surrounds a rotor from the outside in a radial direction, and forms a first space (21s) in which a fluid flows in an axial direction (Da) between the rotor and the inner casing (21). The diffuser (26) is provided with a bearing cone (29) that has a diameter that gradually widens moving towards an axial downstream side (Dad) and forms a cylindrical shape extending to the axial downstream side (Dad) to be continuous with the outer circumferential surface of a rotor shaft that forms the first space (21s). An end edge (29a) on the axial downstream side (Dad) of the bearing cone (29) forms an oval shape in which, in a direction orthogonal to an axial line (Ar), a distance (R2an) between the axial line (Ar) and a second cone end part (29ab) of a second side (Dan) is greater than a distance (R2ex) between the axial line (Ar) and a first cone end part (29aa) of a first side (Dex).