23-09-2014, 04:09 PM
ABSTRACT I would like to express my sincere thanks to my Project Guide, Mr. Alaok shukla. For his guidance and support throughout my training at BHEL, HARIDWAR ,RANIPUR . His calm willingness to teach has been a great help to me for successfully completing the project. My learning has been immeasurable and working under him was a great experience. I extend my sincere thanks to all the staff members of BLOCK 3 (TURBINE BLOCK) production line, for providing a very hospitable and helpful work environment and making my training an exciting and memorable evenjectt. In my training period I was allotted with the following proje ct � THE TURBINE TECHNOLOGIES FOR HIGH EFFICIENCY� Without their continuous help the project would not have been materialized in the present form.. A special thanks to Mr. RAJ SINGH (HRM.) for facilitating me with all tools and equipment Finally, I thank my institute Sri Sukhmani Institute of Engg.& Technology, Derabassi for making this experience of Industrial training in an esteemed organization like BHEL,HARIDWAR ,RANIPUR.
PROJECT REPORT
1. THE TURBINE TECHNOLOGIES FOR HIGH EFFICIENCY :
Advanced Shaft Sealing - retrofitting with retractable, brush, and abradable sealing.
• Blade Replacement – re - blading existing turbine stages with advanced blading, such as
3- dimensional blading.
• Major Component Modernization Options - entire replacement steam paths utilizing
state-of-the-art materials and technology to maximize performance and reduce
reliability and availability issues .
• Condenser Optimizations– analysis, reconfiguring, and tube replacement to optimize
the condenser performance . The key aspects of these technologies will be discussed to provide an executive summary of their features and benefits.
2. HP AND IP ELEMENTS:
MODULAR CONCEPT FOR OPTIMUM LP ENDS FOR A WIDE RANGE OF CONDENSER PRESSURES :
The third major design parameter with respect to modularity is the volume flow through the LP
end stages, which is directly connected to the mass flow and the condenser pressure. The
performance of the last stages and the exhaust diffuser is strongly related to the mean axial
velocity in this area. A number of different LP sizes are therefore required to cover the range of
condenser pressures without compromising the performance of the LP section. In this case, the
focus of the modular concept is to achieve an optimum balance between maximum LP
performance and moderate costs. Therefore, the main targets where set
• to define an optimum set of LP standard stages to cover the required range of volume flows.
• to enable cost effective connections of all required combinations of LP and IP components
• and thereby to maintain optimum performance.
Thereby, a large condenser pressure range of 20 to 200mbar is being considered.
3. SECONDARY FLOW LOSSES :
For usage in these stages , three dimensional 3DS blades have been developed to enhance efficiency by reducing secondary losses . the design is charactersied by the inclination of the profile part of the blades in the root and shroud regions . this angling of the blade imparts an additional force on the pressure and suction side of the flow due to the flow channel . this result in power aerodynamics force due to reduce pressure difference between the suction and pressure sides , hence reducing the driving force for cascade vertices , the main source of secondary losses.
3DS blade shows an efficiency improvement of 0.56% to 1% in comparision to conventional cylindrical blades .In rear stages of HP& IP turbines and few middle stages of the low pressure turbine ,profile losses to improper incidence flow on the relative long cylindrical blades are very high .
4. LP Blading :
Since the axial velocity after the last blade is primarily related to the exit area (and not to length of the last blade), a homogenous distribution of exit areas has been chosen for the Siemens family of LP standard stages . For each of the given exit areas, a set of three standard stages has been designed, In general, the last two rows of LP moving blades are designed as free-standing blades with
curved fir-tree roots for a homogenous stress distribution. The highly-efficient three-dimensional
airfoil design consists of super-sonic tip section for the large end blades (Fig. 10). The inlet edge
is flame or laser hardened, respectively, to prevent from droplet erosion.
5. BANANA TYPE GUIDE BLADES :-
In earlier design of only tapered guide blade flow sepration at hub region of moving blades was taking place due to low degree of reaction . Tapered and forward leaning guide blade known as banana type blades direct the steam flow toward the inner diameter providing sufficient flow at the hub section and therby minimizing the chances of flow sepration in the root area .
Blade section with transonic with discharge velocities in the range up to 1.3 are designed with suction sides that are as straight as possible in order to with eleminater over expantion and sections with higher match are provided with back curved suction faces profiles. The above measure lead to blades with lower profile loss. The velocity distribution at the hub and tip profile of alarger last stage blading with locally supersonic flow condition with convergent/ divergent ststionary and moving blades channels at blade hub and blade tip section .
6. HIGH PRESSURE AND INTERMEDIATE PRESSURE BLADING : -
In reaction steam turbines, the high pressure and intermediate pressure blades so far have
been of cylindrical design, i.e. with a constant profile over the entire length of the blade.
The profiles used are optimised with respect to profile losses and section modulus. Fig. 1
shows the relative flow losses at various points of HP and IP turbines.
The blade profile losses account for major part of these losses. The front stages of the
turbine exhibit relatively high secondary losses (which is the loss due to the development
and turning of boundary layer along the hub and the casing).
Development of new improved TX profile for cylindrical blade stages now affords a higher overall stage efficiency compared to so far used T4 profile. While the earlier T4 profile with its very flat optimum efficiency curve was suitable for a very wide range of applications, the new TX profile yields advantages for part-load operation over a predefined load range. This is in-line with current operating practice for large steam turbines. TX blades show an efficiency improvement of 0.2% over T4 blades. The initial stages of HP and IP turbine exhibit relatively high secondary flow losses due to low volume flow rates and low aspect ratio (blade height to chord).
The inlet boundary layer separation takes place at the end wall region due to pressure
difference between the pressure and suction surfaces of the steam flow channel. This
leads to formation of vortices.
The losses on account of these vortices formation are classified as secondary flow losses.
For usages in these stages, three dimensional (3DS) blades have been developed to
enhance efficiency by reducing secondary losses. The design is characterised by the
inclination of the profile part of the blade in root and shroud regions. This angling of the
blade imparts an additional force on the steam opposite to the force due to pressure
difference between the pressure and suction side of the flow channel. This results in
lower aerodynamic force due to reduced pressure difference between the suction and
pressure sides, hence reducing the driving force for cascade vortices, the main source of secondary losses.
A 3DS blade is shown in the figure 3. 3DS blades show an efficiency improvement of
0.5 % to 1 % in comparison to conventional cylindrical blades.
In rear stages of HP & IP turbines and in few middle stages of the low-pressure turbine,
profile losses due to improper incidence flow on the relatively long cylindrical blade are
very high. Figure 4 shows the velocity diagram for a typical blade stage. The incident
flow velocity to the moving blade changes due to the change in circumferential velocity
at each blade section along the blade height.
This causes improper incident losses especially in longer blades. Minimisation of these
losses calls for different inlet and outlet angles across the height of blade leading to
application of blade with pronounced twist and narrower outer section of profile.
Blade of such type of construction is shown in figure 5. The use of various profiles of
decreasing cross-section along the height significantly reduces profile losses. The
incident and exhaust flow angles are better optimised and the blade can be made longer.
The blades described here are equipped with T-roots and integral shrouds. Integral
shrouds enable better sealing with the casing thus reducing tip clearance losses in such
stages. These blades are installed without gaps at tip with neighboring blades. Root and
shroud are provided with the special rhombohedral form which results in an elastic
twisting of the blade on installation and ensures a closed, prestressed blade assembly,
even in the transient operating range.
7. THE MAIN TECHNOLOGICAL IMPROVEMENTS OF THESE BLADES ARE :-
7.1 3DV BLADING :
Most of the turbine manufacturers now use three dimensional blade design but they still
apply the same degree of reaction to all stages irrespective of being reaction or impulse
blading. This constraint puts a limit to design when aiming for the highest efficiency. As
three dimensional blade has to be designed for each individual stage and each particular
application, the purpose of keeping same degree of reaction has lost its benefit. BHEL
has now introduced new blading where in addition to three dimensional blade
shape, the reaction of each stage is set individually varying between 10 and 60 %. This is
being done with the help of a software called 3DV.
The use of numerical optimization methods has enabled BHEL to individually vary stage
reaction and stage loading for every stage in order to obtain maximum efficiency. This
allows efficiency to be increased by 1% as compared to blading with 50% reaction.
Computer tools and 5-axis milling machines facilitates manufacturing of such
complicated shapes of profiles. Thus a new generation of blading 3-dimensional variable
reaction is here to further improve the efficiency of steam turbines.
7.2 ADVANCED SHAFT SEALING TECHNOLGY : -
PROJECT REPORT
1. THE TURBINE TECHNOLOGIES FOR HIGH EFFICIENCY :
Advanced Shaft Sealing - retrofitting with retractable, brush, and abradable sealing.
• Blade Replacement – re - blading existing turbine stages with advanced blading, such as
3- dimensional blading.
• Major Component Modernization Options - entire replacement steam paths utilizing
state-of-the-art materials and technology to maximize performance and reduce
reliability and availability issues .
• Condenser Optimizations– analysis, reconfiguring, and tube replacement to optimize
the condenser performance . The key aspects of these technologies will be discussed to provide an executive summary of their features and benefits.
2. HP AND IP ELEMENTS:
MODULAR CONCEPT FOR OPTIMUM LP ENDS FOR A WIDE RANGE OF CONDENSER PRESSURES :
The third major design parameter with respect to modularity is the volume flow through the LP
end stages, which is directly connected to the mass flow and the condenser pressure. The
performance of the last stages and the exhaust diffuser is strongly related to the mean axial
velocity in this area. A number of different LP sizes are therefore required to cover the range of
condenser pressures without compromising the performance of the LP section. In this case, the
focus of the modular concept is to achieve an optimum balance between maximum LP
performance and moderate costs. Therefore, the main targets where set
• to define an optimum set of LP standard stages to cover the required range of volume flows.
• to enable cost effective connections of all required combinations of LP and IP components
• and thereby to maintain optimum performance.
Thereby, a large condenser pressure range of 20 to 200mbar is being considered.
3. SECONDARY FLOW LOSSES :
For usage in these stages , three dimensional 3DS blades have been developed to enhance efficiency by reducing secondary losses . the design is charactersied by the inclination of the profile part of the blades in the root and shroud regions . this angling of the blade imparts an additional force on the pressure and suction side of the flow due to the flow channel . this result in power aerodynamics force due to reduce pressure difference between the suction and pressure sides , hence reducing the driving force for cascade vertices , the main source of secondary losses.
3DS blade shows an efficiency improvement of 0.56% to 1% in comparision to conventional cylindrical blades .In rear stages of HP& IP turbines and few middle stages of the low pressure turbine ,profile losses to improper incidence flow on the relative long cylindrical blades are very high .
4. LP Blading :
Since the axial velocity after the last blade is primarily related to the exit area (and not to length of the last blade), a homogenous distribution of exit areas has been chosen for the Siemens family of LP standard stages . For each of the given exit areas, a set of three standard stages has been designed, In general, the last two rows of LP moving blades are designed as free-standing blades with
curved fir-tree roots for a homogenous stress distribution. The highly-efficient three-dimensional
airfoil design consists of super-sonic tip section for the large end blades (Fig. 10). The inlet edge
is flame or laser hardened, respectively, to prevent from droplet erosion.
5. BANANA TYPE GUIDE BLADES :-
In earlier design of only tapered guide blade flow sepration at hub region of moving blades was taking place due to low degree of reaction . Tapered and forward leaning guide blade known as banana type blades direct the steam flow toward the inner diameter providing sufficient flow at the hub section and therby minimizing the chances of flow sepration in the root area .
Blade section with transonic with discharge velocities in the range up to 1.3 are designed with suction sides that are as straight as possible in order to with eleminater over expantion and sections with higher match are provided with back curved suction faces profiles. The above measure lead to blades with lower profile loss. The velocity distribution at the hub and tip profile of alarger last stage blading with locally supersonic flow condition with convergent/ divergent ststionary and moving blades channels at blade hub and blade tip section .
6. HIGH PRESSURE AND INTERMEDIATE PRESSURE BLADING : -
In reaction steam turbines, the high pressure and intermediate pressure blades so far have
been of cylindrical design, i.e. with a constant profile over the entire length of the blade.
The profiles used are optimised with respect to profile losses and section modulus. Fig. 1
shows the relative flow losses at various points of HP and IP turbines.
The blade profile losses account for major part of these losses. The front stages of the
turbine exhibit relatively high secondary losses (which is the loss due to the development
and turning of boundary layer along the hub and the casing).
Development of new improved TX profile for cylindrical blade stages now affords a higher overall stage efficiency compared to so far used T4 profile. While the earlier T4 profile with its very flat optimum efficiency curve was suitable for a very wide range of applications, the new TX profile yields advantages for part-load operation over a predefined load range. This is in-line with current operating practice for large steam turbines. TX blades show an efficiency improvement of 0.2% over T4 blades. The initial stages of HP and IP turbine exhibit relatively high secondary flow losses due to low volume flow rates and low aspect ratio (blade height to chord).
The inlet boundary layer separation takes place at the end wall region due to pressure
difference between the pressure and suction surfaces of the steam flow channel. This
leads to formation of vortices.
The losses on account of these vortices formation are classified as secondary flow losses.
For usages in these stages, three dimensional (3DS) blades have been developed to
enhance efficiency by reducing secondary losses. The design is characterised by the
inclination of the profile part of the blade in root and shroud regions. This angling of the
blade imparts an additional force on the steam opposite to the force due to pressure
difference between the pressure and suction side of the flow channel. This results in
lower aerodynamic force due to reduced pressure difference between the suction and
pressure sides, hence reducing the driving force for cascade vortices, the main source of secondary losses.
A 3DS blade is shown in the figure 3. 3DS blades show an efficiency improvement of
0.5 % to 1 % in comparison to conventional cylindrical blades.
In rear stages of HP & IP turbines and in few middle stages of the low-pressure turbine,
profile losses due to improper incidence flow on the relatively long cylindrical blade are
very high. Figure 4 shows the velocity diagram for a typical blade stage. The incident
flow velocity to the moving blade changes due to the change in circumferential velocity
at each blade section along the blade height.
This causes improper incident losses especially in longer blades. Minimisation of these
losses calls for different inlet and outlet angles across the height of blade leading to
application of blade with pronounced twist and narrower outer section of profile.
Blade of such type of construction is shown in figure 5. The use of various profiles of
decreasing cross-section along the height significantly reduces profile losses. The
incident and exhaust flow angles are better optimised and the blade can be made longer.
The blades described here are equipped with T-roots and integral shrouds. Integral
shrouds enable better sealing with the casing thus reducing tip clearance losses in such
stages. These blades are installed without gaps at tip with neighboring blades. Root and
shroud are provided with the special rhombohedral form which results in an elastic
twisting of the blade on installation and ensures a closed, prestressed blade assembly,
even in the transient operating range.
7. THE MAIN TECHNOLOGICAL IMPROVEMENTS OF THESE BLADES ARE :-
7.1 3DV BLADING :
Most of the turbine manufacturers now use three dimensional blade design but they still
apply the same degree of reaction to all stages irrespective of being reaction or impulse
blading. This constraint puts a limit to design when aiming for the highest efficiency. As
three dimensional blade has to be designed for each individual stage and each particular
application, the purpose of keeping same degree of reaction has lost its benefit. BHEL
has now introduced new blading where in addition to three dimensional blade
shape, the reaction of each stage is set individually varying between 10 and 60 %. This is
being done with the help of a software called 3DV.
The use of numerical optimization methods has enabled BHEL to individually vary stage
reaction and stage loading for every stage in order to obtain maximum efficiency. This
allows efficiency to be increased by 1% as compared to blading with 50% reaction.
Computer tools and 5-axis milling machines facilitates manufacturing of such
complicated shapes of profiles. Thus a new generation of blading 3-dimensional variable
reaction is here to further improve the efficiency of steam turbines.
7.2 ADVANCED SHAFT SEALING TECHNOLGY : -