Adaptive reconstruction of turbine capacity caused by device or system capacity changing

Turbine capacity expanding introduction

1. Introduction
Enterprises are developing at a high speed, and the power load is increasing day by day. Expansion and transformation of the existing steam turbine can solve part of the power gap problem. The expansion and reconstruction of steam turbines is mainly by optimizing the design of steam inlet passages of the turbine's through-flow, increasing flowing area, and increasing steam inlet and exhaust capacity of the turbine, so as to enhance the turbine's function and increase economic benefits.
Early old steam turbines, thermal performance is poor, after years of operation, the main equipment is aging, and efficiency is significantly reduced. While expanding and transforming, adopt advanced mature aerodynamic thermal design technology and structural strength design technology to optimize the design of through-flow part and replace with accurately calculated blades. At the same time, smoothing meridian plane and reducing steam flow loss which can improve steam turbine’s efficiency, and further achieve the purpose of capacity expansion
QNST has introduced and digested the most advanced and mature aerodynamic thermal design technology from domestic and oversea to improve efficiency and reduce costs. Turbine through-flow expansion and efficiency improvement have been provided for multiple power plants, practice has proven that turbine through-flow reconstruction is an important means to improve the efficiency, safety and also reasonably extend the life
2. Turbine capacity expanding scope and parameters

Scope: 6MW～300MW；

Efficiency improving: 3%～6%；

Capacity increasing: 10%～25%；

Typical capacity expanding transformation parameters are shown in the table on the right

3. Cases
The leading principle of the transformation is: keep the existing foundation unchanged, do not make major changes to the thermal system (including steam/water system, regeneration system, gland seal system, and position of each steam extraction port), the front bearing housing and the rear bearing housing are unchanged, casing supping are unchanged, connection method  of rotor, generator and main oil pump and position also with turning gear device are unchanged, replace the moving blades, rotor impellers, diaphragm, nozzle group and guide blade carrier; smooth meridian plane, at same time, eliminate the weak links and unsafe factors of the original turbine, improve the safety, efficiency and function effectively.

3.1 Key technology of through-flow reconstruction

（1）Meridional plane contraction stator blade shall be used for adjusting stage of HP casing

（2）Pressure stage diaphragm static blade of HP casing shall use new type optimize efficient blade.

（3）diaphragm static blade of MP/LP casing shall use bending-torsional static blade.

（4）Adopt new type moving blade, improve speed distribution and reduce rotor blade loss

（5）Increase each stage’s rotor blade end gland seal teeth number, reduce leakage loss. 

（6）Adopt meridian Channel Smoothing Technology

（7）Improve water erosion resistance of last stage blades

（8）Increase last stage blade root reaction degree, improve last stage aerodynamic performance.

3.2 Other parts that may be involved after capacity expanding reconstruction

（1）Expanding original extraction port size for increasing extraction flow
（2）Open new port at casing for bleed steam.

（3）After condensing steam turbine expanding the capacity, exhaust steam flow increasing, to ensure proper vacuum, bigger size condenser or tubes with better heat exchange effect shall be choose. 
（4）Speed governing system reform. 
（5） Generator capacity expanding or change. 
3.3 Other works of capacity expanding
（1）Recalculate critical rotor speed, casing strength, and axial thrust of the turbine
（2）Shaft leaking system, drain system and regeneration system optimization and reconstruction, overall review of the transformed system
（3）Provide corresponding technical data, drawings, heat balance diagrams and instructions for reforming.

Generator capacity expanding

1. Instruction

If turbine was expending capacity, the matched generator shall be expanding the capacity as increasing 10~20%, the control technology should be upgrade. 
Generally speaking, generator volume is related to the generator capacity, speed and voltage level. If the capacity of generator is increased without changing the volume, speed and voltage level, the temperature rise of generator, especially stator and rotor shall increase. The temperature rise limit of the insulation material used in stator and rotor windings limits the increasing of generator capacity. To increase the capacity of generator, it is necessary to reduce various losses inside generator, increase the heat resistance rating of insulating material, and strengthen ventilation and cooling to stabilize temperature rise of main parts at their rated output below temperature rise limit.
2. Technology Application

1）Finite element electromagnetic field analysis, Mechanical stress calculation, temperature field and ventilation cooling calculation technology

2）insulation technology

3）Ventilating cooling technology

4）Air cooling reconstruction technology

5）Excitation technology

3. Retrofitting scheme

1）According to the end user’s retrofitting requirements, collect the calculation sheet and actual operation records of original generator, do theoretical calculations and propose retrofitting content and plan;

2）Generator returned to factory for mechanical and electrical performance inspection

3）All replacement parts (including stator windings) are all purchased, produced and accepted according to the current national standards and factory drawing requirements;

4）Assembly quality meets the requirements of first-class products in industry standard grading regulations

5）The inspection and acceptance of the steam turbine generator after the capacity expansion and transformation is in accordance with the national standard GB755-2008, GB / T7064-2002 and the former Ministry of Electric Power DL / T596.