FIELD OF THE INVENTION:
The present invention relates to the field of a steam turbine configuration for maximum efficiency. Particularly, the present invention relates to a configuration for low pressure range steam turbines especially in cement plant applications to achieve maximum efficiency.
TERMINOLOGY AND FORMULAS USED:
U-Peripheral velocity of rotor; C-Steam velocity; Ct-Tangential steam velocity; Ca-Axial Steam velocity; and Delta h- Enthalpy change.
The formulas employed in doing mean line calculations are as follows:
1) Loading factor-Delta h/U2
2) Peripheral velocity of rotor (U)= 3.147*D*N/60000 m/s
Where D=Rotor Hub Dia; N=speed of rotor in rpm.
3) Steam velocity C- 44.7 *(Delta h)0.5
4) Height of the blades in a stage (H)= 2 Q/3.147*D*sinα*ε*C
Where Q=Volumetric flow rate in each stage (m3/sec);
D= Rotor Hub Dia;
α= Blade or Nozzle Inlet angle;
ε=Degree of admission(Projected Area of nozzles/Total area of moving
blades); C=Steam velocity.
5) Flow Coefficient= Ca/U
DEFINITIONS OF TERMS USED:
Incidence: Incidence is defined as an optimum point on the blade for the flow to hit in order to generate maximum efficiency.
Meridional Plane: A plane cutting the turbo machine through diametric line and longitudinal axis.

Pitch: Circumference of the blade (2*Pi*r)/No.of blades in a row. Circumference of the blade depends on blade height (i.e., at hub, mean or tip).
Stage: Stage herein refers to a combination of rows of blades and nozzles.
Reaction: Enthalpy drop across the rows of blades/ Enthalpy drop across the stage.
Spanwise Reaction: Reaction across different cross-section of blade length.
BACKGROUND OF THE INVENTION:
Figure 1 illustrates a cross-sectional view of a conventional steam turbine.
According to the prior art, there is provided a conventional steam turbine configuration 100 comprising a casing 10, a rotor 12, a nozzle chest 14, a row of impulse blades 16, a plurality of rows of reaction nozzles 18 and a plurality of rows of reaction blades 20. The nozzle chest 14 and the row of impulse blades 16 are together called as a control stage CS. The plurality of rows of reaction nozzles 18 are formed by holding the reaction nozzles in nozzle diaphragms ND which in turn are inserted in to the grooves of the casing 10. The plurality of rows of reaction blades 20 are formed by inserting the reaction blades in to the grooves of the rotor 12.The plurality of rows of reaction nozzles 18 and the plurality of rows of reaction blades 20 are arranged in alternate manner in assembled condition.
The nozzle chest 14 has been used in steam turbines for the following purposes:
1) Generally, in steam turbines with high inlet steam pressure and high inlet steam temperature, it is not recommended to expose first stage of nozzles and moving blades to high pressure and high temperature steam in order to keep the bending stresses on the nozzles and the moving blades within tolerance limits and thereby reduce the chances of failure of the nozzles and moving blades. The nozzle chest 14 of the control stage CS is robust and is made up of high thickness material to withstand to high pressure and high temperature steam and thereby reduces the heat transfer to the casing 10. As the control

stage CS is impulse stage, pressure drop occurs only in the nozzle chest 14 and no pressure drop occurs in the row of impulse blades 16, the row of impulse blades 16 facilitate in directing the steam towards the first stage of nozzles.
2) Generally, the high pressure steam has low specific volume. So, the high pressure blades are generally short in height as the high pressure steam can get exposed only to small annulus area. Especially in part load conditions, the low specific volume of steam calls for control of admission of steam in to steam turbine which in turn calls for application of the nozzle chest 14. The nozzle chest 14 helps in sequential admission of steam in to steam turbine through opening and closing of throttle valves thereby increasing the efficiency of the turbine and ramping up the speed of the rotor 12 gradually keeping the centrifugal forces within tolerable limits.
The row of impulse blades 16 are mounted on a rotor disc D of the rotor 12 at the same height, parallel to the nozzles in the nozzle chest 14.
Figure 2 illustrates an isometric view of a nozzle chest of figure 1.
The nozzle chest 14 has its circumferential area facing the row of impulse blades 16 split in to three nozzle chambers for sequential entry of steam in to steam turbine.
Some techniques have been disclosed in the prior art for optimum admission of steam in to steam turbine for generation of maximum efficiency.
US Patent Application Publication no. 2007/0086890 published on April 19, 2007 titled “Optimized nozzle box steam path” discloses a nozzle box comprising a torus, a steam path ring and a bridge ring. The bridge ring is disposed between the torus and the steam path ring and a radial step provided at interface of the bridge ring and the steam path ring to facilitate in smooth steam flow path without turbulence and thereby increasing the efficiency of the turbine. The method followed herein the above mentioned patent application is optimizing steam flow path through design modification of the nozzle chest and thereby minimizing steam flow path losses.

US Patent no. 4940383 filed on July 21, 1989 titled “System for admitting steam in to a turbine” discloses a method and apparatus for increasing the efficiency of a steam turbine through sequential entry of steam by optimizing control valves involved in opening and closing and also by reducing number of turns in piping leading to nozzle chamber. The granted patent also teaches about reduction of raw material cost through reduction of control valves involved in operation of a steam turbine.
The requirement herein is to design a steam turbine for cement plant applications operating at maximum efficiency. The cement industry customer has two hot gas exhausts from processes which are sent to two waste heat recovery boilers and steam at following exit conditions is generated.
The exit parameters of the steam from two waste heat recovery boilers are taken as inlet conditions of steam to the steam turbine provided with conventional nozzle chest 14 and thermal calculations are performed to determine blade heights, number of rows efficiencies etc., and the results are tabulated in Table 1.
Considering throttle valve losses, the inlet pressure and exit pressure of the steam of high pressure module is 14.7 ata and 1.7 ata respectively. The steam at a pressure of 3 ata is adapted to enter in to a steam turbine at the exit of the sixth stage.

It can be inferred from the table 1 that the efficiency of the first stage (Impulse Stage) is less when compared to other six stages. The total to total efficiency (dry efficiency) of the high pressure module is 90.06% and the total power generated across the seven stages of high pressure module is 3530.4 kw.
Therefore, there is felt a need for development of a steam turbine configuration to overcome the drawbacks of the prior art and thereby achieve better first stage efficiency, better overall efficiency across the high pressure module and generate more power for a given set of boundary conditions.
OBJECTS OF THE INVENTION:
An object of the present invention is to provide a simple steam turbine configuration.
Another object of the present invention is to provide a steam turbine configuration to achieve better first stage efficiency.
One more object of the present invention is to provide a steam turbine configuration to generate more power for given set of operating parameters.
Still another object of the present invention is to reduce amount of raw material involved in manufacturing a steam turbine.

Further another object of the present invention is to manufacture a steam turbine at less cost.
Still one more object of the present invention is to reduce losses during steam expansion.
Further one more object of the present invention is to provide a steam turbine configuration to achieve better overall efficiency for high pressure module.
Still another object of the present invention is to provide an efficient steam turbine configuration for low pressure ranges.
SUMMARY OF THE INVENTION:
In accordance with the present invention a configuration (200) of a steam turbine to achieve maximum efficiency in cement plant applications is provided, the configuration (200) comprising a plurality of rows of reaction nozzles (44) mounted inside a casing (40) and a plurality of rows of reaction blades (46) mounted on a rotor (42), the plurality of rows of reaction nozzles (44) positioned in alternate manner to the plurality of rows of reaction blades (46) in assembled condition and directly exposed to steam at low inlet pressure ranges without the involvement of an impulse control stage (CS), the casing (40) provided with an injection port at a predefined position for injecting the steam.
Typically, the location of the injection port on the casing (40) is decided based on the pressure drop.
BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described with reference to the accompanying drawings in
which:
Figure 1 illustrates a cross-sectional view of a conventional steam turbine according
to the prior art ;
Figure 2 illustrates an isometric view of a nozzle chest of figure 1; and

Figure 3 illustrates a cross-sectional view of a steam turbine in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
A preferred embodiment will now be described in detail with reference to accompanying drawings. The preferred embodiment does not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
Figure 3 illustrates a cross-sectional view of a steam turbine.
In accordance with the present invention, there is provided a steam turbine configuration 200 comprising a casing 40, a rotor 42, a plurality of rows of reaction nozzles 44 and a plurality of rows of reaction blades 46.
It can be clearly observed from the figure 3 that the control stage CS present in the prior art steam turbine configuration 100 is eliminated from the steam turbine configuration 200 of the present invention. The removal of the control stage CS resulted in the free expansion of the steam without any blockages in the form of partitions of the nozzle chest 14.
The inlet conditions of the steam available from two waste heat recovery boilers are as follows:

It can be inferred from the figure 3 that the steam from one waste heat recovery boiler is adapted to enter in to steam turbine before first stage of high pressure module and the steam from other waste heat recovery boiler is adapted to inject in to steam turbine before last stage of high pressure module. Mixing of the steam expanding towards the last stage of high pressure module and the steam being injected happens at the last stage of high pressure module.
Typically, the positioning of the injection port is decided based on the injection pressure of the steam and the exit pressure of the steam at the stages.
Typically, the injection pressure of the steam is maintained slightly higher than the steam expanding towards the stage to facilitate in expansion of the steam towards further stages instead of entering in to the injection port.
Based on the given pressure and temperature of the steam at inlet condition, the inlet enthalpy of the steam is calculated as 3227.6 KJ/Kg.
Considering the mass flow rate at low pressure module and following design rules, the speed of the rotor at design condition is taken as 9000 rpm.
Considering throttle valve losses, the inlet pressure and exit pressure of the steam of high pressure module is 14.7 ata and 1.7 ata respectively.
After performing a number of iterations by varying the thermodynamic loading factor (delta h/U2) within the design constraint limits of 1.05 to 1.4 bar and also by varying pitch radius to maintain constant hub diameter, it has been decided to perform the enthalpy drop across nine stages of the high pressure module for given inlet and exit pressures of the steam and thereby achieving optimized efficiency across the nine stages. The blade/nozzle heights, no. of blades/nozzles in a row, stage reaction, stage enthalpy drop, stage efficiencies, stage power etc., are tabulated in Table 2.

It can be inferred from the table 2 that the first stage efficiency rose by 10% when compared to the prior art. The total to total efficiency (dry efficiency) of the high pressure module is 94.37% which shows an increase of 4.31% over the prior art. The total power generated across the ten stages of the high pressure module is 3953.8kw which shows an increase of 423.4 kw over the prior art.
This kind of steam turbine configuration finds its application only in low pressure ranges where bending stresses on the first stage nozzles and blades are within tolerance limits.
TECHNICAL ADVANCEMENTS:
A configuration of a steam turbine to achieve maximum efficiency in cement plant applications has several technical advantages including but not limited to the realization of:
• a simple steam turbine configuration ;
• a steam turbine configuration to achieve better first stage efficiency ;
• a steam turbine configuration to generate more power for given set of
operating parameters ;

• an efficient steam turbine configuration for low pressure ranges ;
• a steam turbine manufactured with less amount of raw material ;
• a steam turbine configuration to reduce losses during steam expansion ;
• a steam turbine configuration to achieve better overall efficiency for high
pressure module ; and
• a steam turbine manufactured at less cost.
Although the invention has been described herein above with reference to the embodiments of the invention, the invention is not limited to the embodiments described herein above. It is to be understood that modifications and variations of the embodiments can be made without departing from the spirit and scope of the invention.

We claim:
1) A configuration (200) of a steam turbine to achieve maximum efficiency in cement plant applications comprising a plurality of rows of reaction nozzles (44) mounted inside a casing (40) and a plurality of rows of reaction blades (46) mounted on a rotor (42), said plurality of rows of reaction nozzles (44) positioned in alternate manner to said plurality of rows of reaction blades (46) in assembled condition and directly exposed to steam at low inlet pressure ranges, said casing (40) provided with an injection port at a predefined position for injecting the steam, wherein the configuration (200) of a steam turbine is optimized for maximum efficiency for a given set of inlet conditions and operating parameters according to the following table:

2) A configuration (200) of a steam turbine to achieve maximum efficiency in cement plant applications as claimed in claim 1, wherein said configuration (200) find its application only in low pressure ranges and particularly, at the given set of inlet conditions according to the following table:

3) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1, wherein said
configuration (200) is optimized for ten stages and achieved a total power
of about 3953.8 kw.
4) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1, wherein said predefined
position of said injection port for injecting the steam is determined
depending on the pressure drop.
5) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1, wherein said
configuration (200) achieved a more power of about 423.4 kw by directly
exposing the steam to said plurality of rows of reaction nozzles (44) and
said plurality of rows of reaction blades (46) without the involvement of an
impulse control stage (CS).
6) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1, wherein said
configuration (200) achieved a more first stage efficiency of about 10% by
directly exposing the steam to said plurality of rows of reaction nozzles
(44) and said plurality of rows of reaction blades (46) without the
involvement of an impulse control stage (CS).

7) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1, wherein said
configuration (200) achieved a more overall efficiency of about 4.31% by
removing blockages and minimizing losses in the expansion of the steam.
8) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1, wherein said
configuration (200) is simple, easy and cost effective to manufacture.
9) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1 or 2, wherein the power
from two energy sources (Inlet Steam & Injection Steam) is efficiently
captured.
10) A configuration (200) of a steam turbine to achieve maximum efficiency
in cement plant applications as claimed in claim 1 or 4, wherein said
injection port on said casing (40)is provided at the beginning of a tenth
stage.