Embed Size (px)
Citation preview
GE-Confidential
STEAM TURBINE FUNDAMENTALS- I
28th September 2007
B.V.Subbarao
2GE-Confidential
INTRODUCTION
Material compiled in the subsequent pages is meant for educational purpose. Some of the pictures and contents taken and presented here are from the articles read from net with the courtesy of the respective authors.
This PPT is only meant for the internal use within GEDC - ST Engineering.
Fore-word
3GE-Confidential
SCOPE OF THE MODULE 1
Introduction to Steam Turbines Working Principle - Change of State Across Stage Classification based on Applications
Utility Size Operating principles Explanation of thermal power plant
Boiler Turbine Condenser Condensate pumps Steam turbine operating cycles
Simple Rankine Cycle - Modified cycles advantagesReheat Cycles - Regenerative cycleCombined cycles - Co-generative cycle
Compounding of steam turbinesPressure - Velocity & Pressure Velocity CompoundingCross compounding - Tandem Compounding
4GE-Confidential
INTRODUCTION
Steam Turbines are rotating equipments used to produce Mechanical Power from Thermal Energy of steam
Steam turbines are mostly 'axial flow' types. (Steam flows over the blades in a direction parallel to the axis of the wheel.)
WHAT IS A STEAM TURBINE !!
5GE-Confidential
WORKING PRINCIPLE
The steam is expanded in nozzles, resulting in the formation of a high velocity jet. This impinges on the moving blades, mounted on a shaft.
Here it undergoes a change of direction of motion which gives rise to a change in momentum
The shaft power in a turbine is obtained by the rate of change in momentum of a high velocity jet of steam impinging on a curved blade which is free to rotate.
HOW DOES IT WORK !!
6GE-Confidential
CLASSIFICATION
Application - Utility , Captive & Mechanical drives
Size - Small < 15 MW- Medium > 15 MW- Large > 300 MW
Type - Condensing & Back Pressure
Principle - Impulse & Reaction
VARIOUS TYPES !!!
7GE-Confidential
Impulse : Most of the pressure drop for the stage takes place in
nozzleReaction : Pressure drop in a stage takes place approximately
50% in Nozzle and 50% in Buckets
WORKING PRINCIPLE contd.
Basically Steam Turbines are 2
types
8GE-Confidential
Impulse
WORKING PRINCIPLE contd.
Reaction
9GE-Confidential
WORKING PRINCIPLE contd.
10GE-Confidential
ABOUT THE FLUID
Fluid - Superheated SteamInlet pressure* - 2400 – 4500 PSIGInlet Temp* - 1000 – 1100 Deg F
*Sub Critical >= 2400 Psig -1000F (165 bar / 538 C) *Super Critical >= 3500 Psig -1050F (240 bar / 565 C) Ultra Supercritical >= 4500 Psig -1112F (310 bar / 600 C)
Improvements in power plant performance are achieved by raising inlet steam conditions to Supercritical and Ultra supercritical levels
11GE-Confidential
OPERATING PRINCIPLE
The high-temperature, high-pressure steam enters the inlet control valves, which control the steam flow into the turbine.
The steam then travels through the first-stage nozzles, and strikes the first row of buckets. At this point the pressure decreases as the steam passes through the nozzles.
As the steam passes through each stage in a Turbine, the steam conditions vary (i.e. Pressure and Temperatures reduce and specific Volume and entropy increases.)
The expanding steam continues to flow through the rows of nozzles and buckets, each time striking the next row of buckets with a high velocity and causes the shaft to rotate to produce power.
Each row of nozzles and buckets designed for the conditions of steam from previous stage.
By the time the steam is ready to leave the turbine, almost all of its usable energy has been removed ..
12GE-Confidential
ELEMENTS OF A POWER PLANT
1.Boiler2.Steam Turbine3.Condenser4.Feed Pump
13GE-Confidential
STEAM TURBINE OPERATING CYCLE
Simple Rankine Cycle
4 to 1: Isobaric heat supply (Boiler) 1 to 2: Isentropic expansion (Steam turbine), 2 to 3: Isobaric heat rejection (Condenser), 3 to 4: Isentropic compression (Pump),
Critical point
Water lineSteam line ( saturated )
Wet steam zone SIMPLE RANKINE CYCLE
14GE-Confidential
Reheat cycles Regenerative cycle Combined Cycle Cogeneration Cycle
MODIFIED RANKINE CYCLE
STEAM TURBINE OPERATING CYCLE
15GE-Confidential
Reheat cycle one reheat Reheat cycle two reheats
STEAM TURBINE OPERATING CYCLE
16GE-Confidential
Reheat cycle one reheat
STEAM TURBINE OPERATING CYCLE
17GE-Confidential
STEAM TURBINE OPERATING CYCLE
18GE-Confidential
Regenerative Cycle
STEAM TURBINE OPERATING CYCLE
19GE-Confidential
CONCEPT OF MULTI STAGING
Stage : It is a combination of stationary nozzles and row of buckets. A multi-stage turbine is one that has many sets of these nozzles and buckets in series.
Multi-stage turbine : After the steam leaves the first set of nozzles, it enters subsequent stages. Steam discharged from the buckets of the upstream high-pressure stage becomes inlet to next stage.
Therefore, each consecutive stage operates at a lower pressure and the total energy conversion of steam from the highest to the lowest pressure is broken up in a series of stages which allow for better efficiency.
20GE-Confidential
CONCEPT OF MULTI STAGING
The specific volume increases due to expansion of steam in nozzles. The steam passages are gradually widened to accommodate the increasing volumetric flow rate, i.e., blade heights and wheel diameters are increased.
Due to expansion of steam, the temperature drops down at every stage. Each stage contributes a proportionate share of power to the turbine shaft.
What happens to the steam When it passes from one stage to the other !!
21GE-Confidential
COMPOUNDING OF STEAM TURBINE
Pressure Compounding Velocity Compounding Pressure Velocity Compounding Cross Compounding if all of the
machines are parallel Tandem Compounding if all the
machines are connected in series
What is compounding in steam turbines !!
22GE-Confidential
PRESSURE COMPOUNDING
23GE-Confidential
VELOCITY COMPOUNDING
24GE-Confidential
PRESSURE – VELOCITY COMPOUNDING
25GE-Confidential
COMPOUNDING CONTD/
26GE-Confidential
Steam Turbine Power Plants
Steam power plant cycles are characterized by the
pressure level they are operated Sub-critical cycles use steam pressures below the
critical pressure Super-critical cycles operate above the critical
pressure providing higher efficiency.
27GE-Confidential
Type of Steam Turbine is decided based on Steam parameters and Process Needs like Extraction Availability of cooling water for Condenser, Condensing
load and Back pressure Other Techno-economic considerations by the client
Steam Turbine Power Plants
28GE-Confidential
Customers Choice results in type of Plant
Combined Cycle Power Plants Vs. Simple cycle Power Plants
Cogeneration Plants Regeneration and reheating for cycle
efficiency improvements
Steam Turbine Power Plants
29GE-Confidential
Steam turbine Models
Single / Multi casings , Tandem / Cross CompoundedFossil Fuel Fired / Nuclear Steam turbinesCondensing Steam turbine Back Pressure Steam turbine Reheat and regeneration cyclesCogeneration Steam turbine
30GE-Confidential
SIZING CRITEREA
Typical Ratios, # of stages for each size of turbines
Number of stages in a turbine are fixed from the Enthalpy drop required in each stage and length of rotor from rotor-dynamic stand point.
Stage diameter, Nozzle / Bucket heights are decided by the volume flow rate
Machine configuration is dictated by the Enthalpy drop and steam Flow Rate
i.e., HP , IP , LP ( 2stage or 3 Stage )
31GE-Confidential
GE - Steam Turbine Nomenclature
Section I, Reheat and Multi-Casing Non-Reheat Turbines includes the more complex configurations in accordance with the traditional practice of the Schenectady code system.
Section II, Single-Casing, Non-Reheat Turbines, relatively simple design
32GE-Confidential
SECTION I
REHEAT AND MULTIPLE-CASING, NON-REHEAT STEAM TURBINESFULL-SPEED, REHEAT, SINGLE-FLOW CONDENSING TURBINES AFULL-SPEED, NON-REHEAT, DOUBLE-FLOW CONDENSING TURBINES
CFULL-SPEED, REHEAT, DOUBLE-FLOW CONDENSING TURBINES DFULL-SPEED, TANDEM-COMPOUND, DOUBLE-FLOW, PRIMARY (DP) AND DP /DS SECONDARY (DS) CONDENSING ELEMENTS FOR CROSS-COMPOUND,FOUR-FLOW, REHEAT TURBINES FULL-SPEED, REHEAT, TRIPLE-FLOW CONDENSING TURBINES FFULL-SPEED, TANDEM-COMPOUND, TRIPLE-FLOW, PRIMARY (FP) AND FP/FSSECONDARY (FS) CONDENSING ELEMENTS FOR CROSS-COMPOUND, SIX –FLOW REHEAT TURBINESFULL-SPEED, REHEAT, FOUR-FLOW CONDENSING TURBINES
GFULL-SPEED, NON-CONDENSING ELEMENTS OF CROSS-COMPOUND TURBINES
HHALF-SPEED, SINGLE-FLOW CONDENSING TURBINES JHALF-SPEED, DOUBLE-FLOW CONDENSING TURBINES KHALF-SPEED, TANDEM-COMPOUND DOUBLE-FLOW CONDENSING TURBINES
LHALF-SPEED, TANDEM-COMPOUND FOUR-FLOW CONDENSING TURBINES MHALF-SPEED, TANDEM-COMPOUND SIX-FLOW CONDENSING TURBINES NFULL-SPEED, REHEAT, SIX-FLOW CONDENSING TURBINES
SFULL-SPEED, NON-REHEAT, SIX-FLOW, CONDENSING TURBINES TSPECIAL DESIGN SERIES Special Designs
33GE-Confidential
SECTION II
SECTION II
SINGLE-CASING, NON-REHEAT STEAM TURBINESCONDENSING TURBINES WITH NO CONTROLLED EXTRACTIONS OR ADMISSIONS SCNON-CONDENSING TURBINES WITH NO CONTROLLED EXTRACTIONS OR ADMISSIONS SNCCONDENSING TURBINES WITH A SINGLE CONTROLLED EXTRACTION OR ADMISSION SAC NON-CONDENSING TURBINES WITH A SINGLE CONTROLLED EXTRACTION OR ADMISSION SANCCONDENSINGTURBINES WITH TWO CONTROLLED EXTRACTIONS OR ADMISSIONS DACNON-CONDENSING TURBINES WITH TWO CONTROLLED EXTRACTIONS OR ADMISSIONS DANC
34GE-Confidential
Summary : Machines commonly used
Type
Current m/c
Description
A A14-A15 FULL-SPEED, REHEAT, SINGLE-FLOW CONDENSING
D D10–D11
FULL-SPEED, REHEAT, DOUBLE-FLOW CONDENSING
G G1–G12 FULL-SPEED, REHEAT, FOUR-FLOW CONDENSINGDense packs are used for the retrofits of these machines
N N1 – N2 HALF-SPEED, TANDEM-COMPOUND SIX-FLOW CONDENSING (only for Nuclear Application)
SC SC4-SC5 CONDENSING TURBINES WITH NO CONTROLLED EXTRACTIONS OR ADMISSIONS
REHEAT AND MULTIPLE-CASING, NON-REHEAT STEAM TURBINES A to NSC Single casing Non reheat Steam Turbines
35GE-Confidential
Nuclear Vs Fossil Steam Turbines
Parameter Nuclear FossilSteam parameters
Low pressure and saturated steam used (60 -70 bar 250 to 280 Deg C)
HP Superheated with or without reheat(160 bar -540 Deg C)
Moisture capture provisions
1 or 2 stg. Moisture Separators and re-heaters provided after HP casings
No Moisture separators are employed due to superheated steam
LP rotors Specially designed Mono-block LP rotors ( This eliminates susceptibility to fretting and loosening of shrunk-on components )
-
Number of HP/LP casings
One HP casing Before LP stages ( 3 parallel stages)
HP + Reheat / IP stg Before LP Stages
Bucket Design
Aerodynamic Bucket design To eliminate flow separation and reduce losses and very long last stage buckets
Nuclear Vs Fossil Steam Turbines
36GE-Confidential
SC : CONDENSING TURBINES WITH NO CONTROLLED EXTRACTIONS OR ADMISSIONS
1 15 16
37GE-Confidential
SC : CONDENSING TURBINES WITH NO CONTROLLED EXTRACTIONS OR ADMISSIONS
1 15 16
38GE-Confidential
A : FULL SPEED, REHEAT, SINGLE FLOW CONDENSING TURBINES
A14 Off-Shell Control Valves(s), Double-Shell High Pressure Section With Reaction Staging, Generator on High Pressure End, Sliding Support of Shell on Front Standard.
39GE-Confidential
A : FULL SPEED, REHEAT, SINGLE FLOW CONDENSING TURBINES
A15 Off-Shell Control Valves(s), Double-Shell High Pressure Section With Reaction Staging, Generator on High Pressure End, Sliding Support of Shell on Front Standard. Fixed Support of Shell on Fixed Mid Standard, Sliding Low Pressure Exhaust Hood. For Single-Shaft and Multi-Shaft Combined Cycle.
40GE-Confidential
D : FULL SPEED, REHEAT, DOUBLE FLOW CONDENSING TURBINES KW OUTPUT 293,597
FLOW (LB/HR) 1,922,040 PSIA 2414.4
°F 1000/1000 % MU 0.0
1 717 16 1 6
41GE-Confidential
D : FULL SPEED, REHEAT, DOUBLE FLOW CONDENSING TURBINES KW OUTPUT 293,597
FLOW (LB/HR) 1,922,040 PSIA 2414.4
°F 1000/1000 % MU 0.0
1 717 16 1 6
42GE-Confidential
G2 : FULL SPEED, REHEAT, FOUR FLOW CONDENSING TURBINES ( HP + Reheat + LP-A + LP–B )
43GE-Confidential
G3 : FULL SPEED, REHEAT, FOUR FLOW CONDENSING TURBINES ( HP + Reheat + LP-A + LP–B )
44GE-Confidential
N : FULL SPEED, NON REHEAT, SIX FLOW CONDENSING TURBINES ( LP-A + LP–B + LP-C)
45GE-Confidential
Thank you
STEAM TURBINE FUNDAMENTALS- I
