Axial Flow Turbine Nozzle Box Gradual Steam Channel Width Design
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Solution Overview
Problem
Conventional nozzle boxes in axial flow turbines experience significant pressure losses due to abrupt changes in steam channel widths, leading to reduced turbine efficiency.
Innovation Solution
The nozzle box design features a gradual increase in steam channel widths in one direction and a corresponding decrease in the other direction from the inlet to the outlet, preventing abrupt area changes and minimizing total pressure loss ratios through a monotonous change in cross-sectional areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the steam channel width is monotonously increased toward the downstream side, then the working fluid can be uniformly led to the blade cascade, but the pressure loss in the passage part increases due to abrupt area changes
Solution Approach 1:
The patent applies parameter changes by gradually varying the steam channel width dimensions (Sa-1 to Sn-1 in the first direction and Sa-2 to Sn-2 in the second direction) along the channel center line from the inlet to the outlet. This gradual dimensional change prevents abrupt area expansions that cause pressure loss, while still achieving uniform flow distribution to the blade cascade. The cross-sectional area changes monotonously without sudden jumps, resolving the contradiction between uniform flow and pressure loss reduction.
2Area of stationary object
If the steam channel width is abruptly increased, then the flow area is expanded, but the total pressure loss ratio increases due to non-monotonous area changes
Solution Approach 1:
The patent employs curvature principles by ensuring the steam channel width changes gradually and smoothly rather than abruptly. The dimensions Sa-1 to Sn-1 and Sa-2 to Sn-2 are designed to change progressively along the channel center line, creating a smooth transition in cross-sectional area. This gradual curved transition prevents sudden expansions that would cause pressure loss, while still achieving the necessary area expansion for adequate steam flow to the blade cascade.
3Ease of manufacture
If the channel cross section is designed with circular shape at inlet, then the manufacturing is simplified, but the steam channel width causes abrupt area ratio changes leading to pressure loss
Solution Approach 1:
The patent applies local quality by maintaining a circular cross-sectional shape specifically at the inlet portion where manufacturing simplicity is crucial, while introducing gradual dimensional variations in the steam channel width (Sa-1 to Sn-1 and Sa-2 to Sn-2) along the channel center line toward the outlet. This localized approach preserves the easy-to-manufacture circular inlet shape while gradually transforming the geometry downstream to prevent abrupt area ratio changes and reduce pressure loss.
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 design reduces total pressure loss in the steam channel, enhancing turbine efficiency by maintaining a consistent flow and minimizing swirl and high-speed area losses.
Implementation Method 1
the steam channel widths Sa-1 to Sn-1 in a first direction and the steam channel widths Sa-2 to Sn-2 in a second direction which intersects with the channel center line 50 and is perpendicular to the first direction are gradually changed from an inlet 20a of a lead-in pipe 20 toward an outlet 40a of an annular pipe 40
Implementation Method 2
This design reduces total pressure loss in the steam channel, enhancing turbine efficiency by maintaining a consistent flow and minimizing swirl and high-speed area losses
Data Source
Figure 1
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AI summary
A nozzle box 10 includes: a lead-in pipe 20; a bent pipe 30 connected to the lead-in pipe 20 and formed so as to change a direction of a channel center line 50 to an axial direction of a turbine rotor 212; and an annular pipe 40 connected to the bent pipe 30 and leading steam to a first-stage nozzle 213a while spreading the steam in a circumferential direction of the turbine rotor 212. In the steam channel lead-in part structure 10, from an inlet of the lead-in pipe 20 toward an outlet of the annular pipe 40, steam channel widths Sa-1 to Sn-1 in a first direction intersecting with the channel center line 50 gradually increases and steam channel widths Sa-2 to Sn-2 in a second direction intersecting with the channel center line 50 and perpendicular to the first direction gradually decreases.