Steam Turbine Inner Housing Process Steam Deflection
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Solution Overview
Problem
Steam turbines with reheating systems face challenges such as high thermal stresses in the outer wall due to temperature differences and the risk of condensate formation, leading to potential leaks or cracks, and energy losses from additional inlet housings.
Innovation Solution
The steam turbine design includes a high-pressure inner housing with a process steam deflection section and reheater arrangement, where process steam is throttled to reheating parameters without doing work, allowing it to be directed between sealing shells to locally heat the area, reducing thermal stresses and eliminating cold spots, and using a higher leakage mass flow to preheat the rotor and inlet section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If process steam is fed to the low-pressure part of the steam turbine, then the steam turbine can generate mechanical energy, but the temperature drop causes partial condensation and high moisture content that damages turbine blades
Solution Approach 1:
The steam turbine is divided into multiple independent inner housings (high-pressure, intermediate-pressure, low-pressure stages) that can be separately designed and optimized. Each housing handles specific pressure and temperature ranges, allowing tailored blade designs and moisture separation mechanisms for each stage.
Solution Approach 2:
An intermediate superheater is introduced as a mediator between the high-pressure and low-pressure stages. It reheats the process steam after the high-pressure stage, reducing moisture content before the steam enters the low-pressure turbine blades, thereby preventing droplet erosion.
2Object-affected harmful factors
If the process steam is reheated in an intermediate superheater, then the moisture content drops and blade damage is prevented, but the thermal stress on the outer wall increases due to high temperature differences
Solution Approach 1:
The turbine is segmented into multiple independent inner housings rather than a single outer housing. This allows each housing to be thermally isolated and optimized for its specific temperature range, reducing thermal stress on any single structure.
Solution Approach 2:
Different housing materials and thermal insulation properties are applied to different sections based on local temperature requirements. The high-pressure housing uses materials suitable for high temperatures, while the low-pressure housing is optimized for lower temperatures, reducing overall thermal stress.
3Strength
If additional inlet housings are used to cool the overheated process steam, then thermal stress is reduced, but energy losses increase
Solution Approach 1:
The process steam that would otherwise be wasted or require cooling is instead utilized to preheat the incoming live steam through heat exchangers. This converts the thermal energy that would be a loss into a useful heating function, reducing overall energy consumption.
Solution Approach 2:
The steam after expanding through the turbine stages is not discarded but recovered and used for preheating purposes. The thermal energy is recovered and reused, eliminating the need for additional cooling housings and associated energy losses.
4Device complexity
If a single-shell steam turbine is used, then the device complexity is reduced, but the housing cannot withstand the high temperature differences and pressures required for efficient operation
Solution Approach 1:
The single shell is segmented into multiple independent inner housings (high-pressure, intermediate-pressure, low-pressure) that can each be optimized for their specific operating conditions. This maintains relative structural simplicity while achieving the necessary temperature and pressure resistance.
Solution Approach 2:
Multiple inner housings are nested within the outer housing structure. Each inner housing is positioned concentrically or adjacently, creating a compact multi-chamber structure that withstands high temperature differences while maintaining a relatively simple overall form factor.
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 enhances temperature distribution, reduces thermally driven deformation, allows smaller clearances between the rotor and housing, increases efficiency, and supports higher temperature differences, leading to cost-effective operation with reduced design complexity and energy losses.
Implementation Method 1
The process steam which has been expanded in the first steam expansion device is throttled directly to the reheating parameters without doing any work and is conducted into the area between the high-pressure sealing shell and the low-pressure sealing shell
Implementation Method 2
The removed process steam can thereby be used to direct it into an area of the high-pressure sealing shell and the low-pressure sealing shell in order to locally heat the area
Implementation Method 3
The high-pressure sealing shell is designed such that a predeterminable leakage mass flow can be conducted via the high-pressure sealing shell in an area between the high-pressure sealing shell and the low-pressure sealing shell
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a steam turbine (1), having a low-pressure inner housing (NDIG) and a high-pressure inner housing (HDIG) within a steam turbine outer housing (20), a reheater (50) downstream of the HDIG (30) and upstream of the NDIG (40) wherein the first steam inlet section of the HDIG (30) faces the second steam inlet section of the NDIG (40), and a process steam deflection section (60) for deflecting process steam out of the first steam outlet section into a gap between an inner wall of the steam turbine outer housing and an outer wall of the HDIG (30) and of the NDIG, a high-pressure sealing shell (34) for sealing the upstream end-section of the HDIG (30), a low-pressure sealing shell (44) for sealing the upstream end-section of the NDIG (40), the high-pressure sealing shell (34) and the low-pressure sealing shell (44) being located adjacent to one another, and the HDIG (30) being designed such that process steam can be drawn from the HDIG and can be conveyed to a region between the high-pressure sealing shell (34) and the low-pressure sealing shell (44).