Steam Turbine Low-Pressure Section Ventilation Heating Control
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Solution Overview
Problem
Steam turbines face issues with impingement corrosion and temperature-related wear in low-pressure sections, leading to high maintenance costs and limited material options due to ventilation effects during no-load or low-load operations, which impair efficiency and restrict the use of lightweight materials.
Innovation Solution
A steam turbine system with an additional steam inlet device controlled by operating parameters to manage steam supply, reducing temperature and pressure stress in low-pressure sections, allowing for the use of lightweight materials like fiber composites and minimizing ventilation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low outlet pressure is used to improve efficiency, then energy conversion efficiency is improved, but impingement corrosion and wear of rotor vanes increase
Solution Approach 1:
The turbine is divided into multiple independent pressure sections (high-pressure, intermediate-pressure, and low-pressure sections) with separate steam inlets. This allows the low-pressure section to operate at optimal low outlet pressure for efficiency while the high-pressure section maintains higher pressure to reduce moisture content and impingement corrosion in the low-pressure section.
Solution Approach 2:
An intermediate-pressure section is introduced between the high-pressure and low-pressure sections. This intermediate section acts as a mediator that progressively reduces steam pressure and moisture content, preventing direct exposure of the low-pressure section to high-moisture steam that causes impingement corrosion.
2Reliability
If specially-coated rotor vanes are used to resist wear, then wear resistance is improved, but maximum application temperature is limited to about 120°C
Solution Approach 1:
The rotor vanes are divided into different sections corresponding to different pressure zones. Rotor vanes in the high-pressure section with higher temperatures use materials suitable for high temperature, while rotor vanes in the low-pressure section with lower temperatures can use lightweight materials with lower temperature limits but excellent wear resistance.
Solution Approach 2:
The temperature parameter in the low-pressure section is reduced through the multi-section design, allowing the use of materials with lower maximum application temperatures. This enables the use of specially-coated rotor vanes that provide superior wear resistance but can only withstand temperatures up to about 120°C.
3Weight of moving object
If lightweight materials like fiber composites are used for rotor vanes, then weight is reduced, but maximum temperature tolerance is limited
Solution Approach 1:
Rotor vanes are segmented by location within the turbine. Lightweight fiber composite materials are used specifically in the low-pressure section where temperatures remain below the material's maximum tolerance, while traditional high-temperature materials are used in the high-pressure section.
Solution Approach 2:
The temperature parameter in the low-pressure section is controlled to remain within the acceptable range for lightweight fiber composite materials. This parameter change enables the use of these materials in the low-pressure section, achieving weight reduction without exceeding material temperature limits.
4Ease of operation
If ventilation heating occurs in low-pressure section during no-load operation, then temperature increases to 200-250°C or more, but material options for rotor vanes are restricted
Solution Approach 1:
The harmful ventilation heating effect is extracted and isolated to specific sections. By providing separate steam inlets and controlling steam flow to different pressure sections independently, the ventilation effect that causes excessive temperature rise is eliminated or reduced in the low-pressure section during no-load operation.
Solution Approach 2:
The temperature parameter in the low-pressure section during no-load operation is controlled to remain below the maximum tolerance of lightweight materials. This is achieved by adjusting steam flow parameters and preventing excessive ventilation heating, thereby expanding material selection flexibility.
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 solution extends the service life of turbine components, reduces maintenance costs, and enables the use of lightweight materials by controlling steam supply to prevent temperature increases, thereby enhancing efficiency and operational flexibility.
Implementation Method 1
the thermal energy from steam supplied to the turbine is converted into mechanical work
Implementation Method 2
The temperature and the pressure of the steam are reduced in the route between steam inlet and steam outlet during this conversion
Implementation Method 3
moisture that has condensed out of the steam can precipitate and form water droplets in the turbine
Implementation Method 4
Water droplets entrained by the flow of steam collide with the rotating rotor vanes with a high level of energy so the vanes are subject to corresponding wear
Implementation Method 5
the steam in the low-pressure section (for example end stage), which has already been extensively expanded and cooled in preceding turbine sections, is heated again by the rotating rotor vanes
Data Source
AI summary
A steam turbine system including a steam turbine is provided. The steam turbine system includes a high-pressure side steam inlet device, a low-pressure side steam device, and a control device for controlling the steam turbine. An additional steam inlet device is also included arranged between the high-pressure side steam inlet device and the low-pressure side steam device. The control device control a supply of steam via the additional steam inlet device as a function of operating parameters detected at the steam turbine system.