design of a gas turbine combustion system
TRANSCRIPT
Power Generation 1
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Design of a Gas turbine combustion systemTorsten Strand [email protected]
Power Generation 2
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Content
The design requirements, criteria and targets
The overall design processThe gas turbine cycle: Excel calculationsBurner and cooling mass flows: Design calculationsBurner type: lean premixed, diffusion flame or something in betweenCombustor heat balance, choice of combustor design: Excel calculations
The component designsburners combustor : Excel calculationsfuel system : Excel calculations
Ignition and supervision systems
OperationStart upPart load
Power Generation 3
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Assumptions
We are going to design a new gas turbine with the shaft power of 35MW for a market consisting of
60% compressor drivers for pipe line compressors40% industrial cogeneration
The first customer segment want a very reliable and robust simple cycle unit for pumping of gas from desolated gas fields in
Siberia ( 0 to -50°C)Iranian mountains (-20 to +45°C, low ambient pressure)Saudi Arabian deserts (+10 to +50°C)Efficiency and emissions are not of prime interestFuel is natural gas
The second customer type want an efficient, but still very reliable gas turbine with low emissions and suitable for steam production in waste heat recovery boilers for industries, mainly in the western world. Fuel is natural gas or industrial off gases.
Power Generation 4
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Case 1Gas Turbine in Simple Cycle
100 % fuel
Gas Turbine
63.6 % losses
36.4 % electricity
Pgt 44.30 MWPst 0 MWPaux 0.10 MWPnet 44.20 MWHeat duty 0 MJ/sQfired 121.4 MJ/s
Alfa ∞ ---Net electrical efficiency 36.4 %Net total efficiency 36.4 %
Power Generation 5
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100 % fuel
1-pressure HRSG
Gas Turbine
Case 2Gas Turbine in Cogeneration Cycle
12 % losses
35.9 % electricity
52.2 % process heat
Pgt 43.82 MWPst 0 MWPaux 0.23 MWPnet 43.59 MWHeat duty 63.4 MJ/sQfired 121.4 MJ/s
Alfa 0.69 ---Net electrical efficiency 35.9 %Net total efficiency 88.1 %
Power Generation 6
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Steam Turbine (condensing)
100 % fuel
15 deg CGas Turbine
Case 3Gas Turbine in Combined Cycle
2-pressure HRSG
520 deg C
27 deg C
31 deg C31 deg C
12 % losses
35.9 % electricity
16.8 % electricity
35 % lossesPgt 43.69 MWPst 20.78 MWPaux 0.70 MWPnet 63.77 MWHeat duty 0 MJ/sQfired 120.9 MJ/s
Alfa ∞ ---Net electrical efficiency 52.7 %Net total efficiency 52.7 %
Power Generation 7
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100 % fuel
Gas Turbine
Steam Turbine (district heating)
90 deg C
60 deg C
2-pressure HRSG
Case 4Gas Turbine in Combined Cycle
510 deg C
78 deg C
78 deg C
11 % losses
35.9 % electricity
11.3 % electricity 42.1 %
heat
Pgt 43.70 MWPst 14.18 MWPaux 0.62 MWPnet 57.26 MWHeat duty 51.1 MJ/sQfired 121.4 MJ/s
Alfa 1.12 ---Net electrical efficiency 47.2 %Net total efficiency 89.3 %
Power Generation 8
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Is it possible to use the same design for both applications?
Well, we will try!
The compressor drive requires a variable speed power turbine, so we have to assume a twin shaft unit
The efficiency of the cogeneration unit ought to be in the range of 37% at full load, which means that the heat input is around 95MW
Power Generation 9
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The core engine 1
We have now a basic design.
A critical parameter is the Turbine Inlet Temperature. The higher TIT the better gas turbine cycle, but generally also less robustness and higher turbine cooling flow
Let us assume a conservative TIT = 1300°CFrom experience the turbine cooling flow will then be around 16%
95MWth
35MWe
Turbine cooling
TIT
Power Generation 10
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Turbine Inlet Temperatureand emissions
Turbine Inlet Temperature C and NOX
1940 1960 1980 2000
1000
1500
500
Jet Engines
Stationary Gas Turbines
Single Crystal Blades
GT10B/CGT35/GT120
GTX100
Year
CeramicsSteam Cooling
GT200
100
200
Power Generation 11
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The gas turbine cycle
p2, t2
p3, t3
p5, t5mt5
Tflame
p7, t7
p6, t6
ηct = (t5m - t6)/(t5m - t6s)
ηpt = (t6m - t7)/(t6m - t7s)
ηc = (t3s - t2)/(t3 - t2)
T
s
Power Generation 12
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The turbine pressure levels
How are the pressure levels at the compressor and power turbine sat?
The turbine can be seen as a tube with restrictorsIn order to pass a certain flow at a certain temperature there is an associated flow area/pressure combinationThe flow area is determined by the turbine inlet guide vanes
Inner/outer diameterExit blade angle, which is on gas turbines is generally fairly large, which means that the stage design is of reaction type (the enthalpy drop is divided between vane and blade)
m = A *rot(2*Δp*ρ) = A *rot(2*Δp*p/RT) = Ψ*A*p/rot(RT)
For computational purposes the below formula is very usefulm*rot(T)/p = constant
Power Generation 13
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Turbine flow
The flow capacity of the turbine is determined by the smallest area in the turbine inlet guide vane and the root and tip section diameters
the turbine “wideness”the turbine flow number m*rotT/pthe ”turbine constant”
The flow capacity of the turbine determines the position of the operating line in the compressor map.
An uncooled turbine has better efficiency than a cooled turbine, which has less good profiles (lower aspect ratio, thick trailing edges) and mixing losses from the cooling flows
Power Generation 14
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The gas turbine cycle
Power Generation 6
95Mth
35MWe
Turbine cooling
TIT
p2, t2
p3, t3
p5, t5mt5
Tflame
p7, t7
p6, t6
ηct = (t5m - t6)/(t5m - t6s)
ηpt = (t6m - t7)/(t6m - t7s)
ηc = (t3s - t2)/(t3 - t2)
T
s
The next step is to make a simple thermodynamic model of the gas turbine in order to get the conditions for the combustor.
We will do it in Excel!
Power Generation 15
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SGT-600, Industrial gas turbine
Gas turbine principle & components
Power Generation 16
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The core engine 2
Now we need to choose the pressure level for the turbine inletThere is an optimal pressure level for efficiency associated with the turbine inlet temperature, but it is generally quite high which means a low TET. We have also to consider the steam production in the waste heat recovery boiler, so we need a fairly high TET > 520°C ??We will try some pressures for TIT = 1300°C
1800 kPa η=38.3% TET=509°C T3=438°C 1700 kPa η=38.0% TET=517°C T3=426°C1600 kPa η=37.6% TET=526°C T3=413°C1500 kPa η=37.1% TET=536°C T3=400°C
The higher the pressure the higher also the compressor exit air temperature T3. That air is
the combustion airthe cooling air for the turbine and combustor walls
For combustion high air temperature is generally better
NOx and combustion pulsations have a tendency to increase with pressure
Power Generation 17
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The combustor 1
Now we have basic full load data for the combustorAir flow to the combustor: 82.8/426/1785 kg/s/°C/kPaFuel flow: 2.02 kg/s Combustor exit flow: 84.8/1300/1700 kg/s/°C/kPa
In order to design the combustor we have to know which type of burner we are going to use
82.8 kg/s
426°C
1785kPa
84.8 kg/s
1300°C
1700kPa
2.02 kg/s
Power Generation 18
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Burner 1: types of burners
The conventional combustors were designed for Stoichiometric combustion, using fuel injectors with low air flows Φ ≅1. Water or steam injection were used for NOx reduction
The lean premixed combustors are designed with a high air flow that cools the flame
The low oxygen combustors relay on a combustion process in O2-depleted gas, achieved by recirculation of combustion products
NOx ppmv
200
100
0. 5 1.0 1.5Fuel/Air Equivalence Ratio
Water Injection
Steam InjectionLean Premix Combustion
Diffusion flames
Φ = 1/λ
Power Generation 19
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Diffusion type dual fuel Injector
STEAM INLET
PURGE HOLES
HCV GAS HOLES
Dual fuel Injector for gas and oil with water and
steam injection
STD PART-POSITIONABLE ELBOW
Gas inlet
Oil inlet
Water inlet
Air
2100K
Power Generation 20
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NOx and CO vs Flame Temperature
-- Advanced DLE burners Advanced DLE burners --
10
20
30
40
50
1700 1800 1900Flame Temp K
NOx ppm
CO
40
30
20
10
CO ppmEV BurnerDLE Gas
NOxAEV BurnerDLE Gas & Oil
Low oxygen burner
Catalytic burner
Power Generation 21
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Our case
The Oil&Gas customers have presently no high requirements on emissions, but the industrial customers will have a requirement of NOx< 10 ppm
We will try to build a low NOx burner of lean premix type
Our trial choice is a LP burner with a design flame temperature of 1750K How much air is needed for the combustion?
We will do a heat balance calculation for the flame zone
Power Generation 22
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The combustor 2
Now we have the basic flow data for the combustorAir flow to the burner: 65/426/1785 kg/s/°C/kPaFuel flow: 2.02 kg/s Wall cooling flow: 17/426/1785 kg/s/°C/kPa
65 kg/s
17 kg/s
426°C
1785kPa
84 kg/s
1300°C
1700kPa
2.02 kg/s
Power Generation 23
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Wall cooling
The burner air is around 65 kg/s out of the 82 kg/s combustion air
We have around 21% of the combustion air for wall cooling, whichought to be enough for a film cooled sheet metal combustor.
438450 500 850
1477÷1300
If the film cooling air is on the low side Thermal Barrier Coating can be used.
If there is more air than necessary for cooling, it can be injected as dilution air in the down stream part of the combustor.
Power Generation 24
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Wall cooling designs
438450 500 850
1477÷1300
The shown wall design is the traditional one for film cooled combustors.Several similar designs with improved performance are in use
The use of Thermal barrier coatings has been more common. Conventionally only thin TBC (<0.5 mm) has been used. But lately also thick TBC (up to 1.5 mm) has become frequent.
In turbines with higher turbine inlet temperature, the cooling air has not been enough for film cooling. Wall with only outside cooling and thick TBC is then the solution.
Meal wall Bound coat TBC
Impingement Convection
Power Generation 25
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Wall heat transfer: film cooling
For initial design we can assume a heat flux to the combustor wall in the range of 600kW/m2 but dependent on the gas temperature. The hot side heat transfer is a combination of convective and radiation heat flux
qhot = α*(Tgas – Twall) + const*S-B*[Tgas4 – Twall4]α ≅ 590 when velocities are around 30 m/s and pressure 1700 kPa, increasing at higher velocities and pressure. The radiation constant is dependent on flame radiation and surface emissivity
In the combined impingement/convection cooled design we can assume that the metal temperatures for one wall section starts at air temperature and reaches 850°C, with an average wall temperature of 565°C.
It is then assumed that the injected cooling air will absorb the heat flow to the surfaceQ = qhot*A = m*cp*(565-tcool)
The length of a section depends of course on the design but 50 ÷ 70 mm is common
The rings are laser drilled, rolled to form and seam welded in a fixture
Power Generation 26
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Wall cooling: convection cooling
In the case when there is not enough air for film cooling, outside convection cooling with the combustion air has to be used.
The cooled side heat transfer has then to match the hot side heat flux
Q = qhot*A = α*A*(twall – tair)
When using TBC the heat flow through the wall is reduced by the low heat conductivity of the ceramics, λ = 1.1÷ 1.6 and the lower absorption of radiation
The cold side heat transfer coefficient α is a function of the air velocity, pressure and the shape of the surface. Usually the wall surface has ribs, fins etc to enhance the heat transfer up to 1.7 times
Annular combustor with convection cooled walls
Power Generation 27
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Combustor size
The bulk flow velocity in the combustor can tentatively be set to around 30 m/s, which means that there is a need for a flow area in the combustion chamber inlet exit section of around 0.63 m2
The turbine inlet velocity can be in the range of 100-130 m/s, which means that there is a need for an exit area in the range of ~0.2 m2
The length of the combustor depends on what residence time we want. This could be investigated by combustion kinetics calculations, but a value based on experience for natural gas and diesel oil is 15÷20 ms 15 ms which gives a axial length of around 600 mm
Now it is time to make a choice of combustor typeAnnularCan-annular
Tilted or in line with the flow
Power Generation 28
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Annular versus can-annular
The annular combustor has compared to the can-annular typeless wall surface area to coolfewer auxiliaries
Spark plugsFlame detectors
Annular combustors are used in almost all jet engines and many high temperature industrial turbines
The can-annular design has most oftenfewer but larger burnerstransition ducts between the circular combustion chambers and sectors of the turbine inlet, which is difficult to design and cool Can combustors are used in many industrial turbines by tradition and for easier maintenance
The can type of combustor is easier to develop since the testing can be done on one of the combustors, while it is quite difficult to use the test results from a sector test of an annular combustor
Power Generation 29
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A GE can combustor
Main swirl premixers
Premixed PilotTransition duct
Power Generation 30
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GE Frame 5
Power Generation 31
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Siemens G30 Combustor Concept
Double Skin ImpingementCooled Combustor
Main Burner
Pilot Burner
Power Generation 32
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Annular combustor for Siemens SGT-600
.
DLE combustor for 25 ppmv with EV burners since 1991
18 DLE burners
Sheet metal (HastX), annular combustor with film cooled walls and impingement cooled front panel
Number of cooling holes 5800
Outer diam ~ 1 m
Power ~ 75 MWth
Manufactured by Trestad Svets in Trollhättan (now a Siemens Company)
Power Generation 33
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Flows in conventional annular combustor
Primary injection
Primary zoneSecondary injection
Turbulence and mixing by primary and secondary jets
Power Generation 34
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Annular combustor types
In line annular combustor with burners fixed to the combustion chamber
Tilted annular combustor with removable burners for easier maintenance
Power Generation 35
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Annular combustor dimensions
Assume tentativelyouter radius inner radius height
at the combustor front panel: 600 400 200 at combustor exit: 450 390 60
The philosophy for the wall contour differs. There are e.g. parallel walls and pear like forms.
CFD calculations on
• the velocity and temperature distribution at the combustor exit
• the recirculation pattern
are important aspects as well as manufacturing aspects.
Combustor wall design
0
100
200
300
400
500
600
700
-200 0 200 400 600
Axial position mm
Rad
ius
mm
Outer wallInner wall
Power Generation 36
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Combustor re-circulating flow
Combustor wall design
0
100
200
300
400
500
600
700
-200 0 200 400 600
Axial position mm
Rad
ius
mm
The recirculation of hot gases in the combustor is necessary for
• ignition of the flame
• lowering of NOx by reducing the O2 content in the flame
The recirculation can be achieved in different ways, but the most common is to use swirling flows.
Swirling jet aerodynamics is important and a lot of research is done in that field
Power Generation 37
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Exit temperature profile
The radial temperature profile is very important for the rotating blade life. Due to the wall cooling flows a peaky profile can be expected, which is good for the blades (cold root and tip sections), if it is not too hot in the centre. Dilution air can be used to shape the exit profile.
The tangential profile is important for the stationary vanes.
Power Generation 38
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DLE evolution, GT 15-50 MW- history
Used in: GTX100 GT10B&C GT35C
Silo Combustors Annular Combustors
Single burner 1st gen. DLE
Residence time reduced by using many small burners, with short flames:• introduced 1986, NOx ≈ 75 ppmv on gas
2nd gen. DLE
Lean premix combustion in two-slotted cone, multiple burners:• introduced 1991, NOx ≈ 25 ppmv on gas
3rd gen. DLE
Lean premix combustion in four-slotted cone + mixing tube, multiple burners:• introduced 1999, NOx < 15 ppmv on gas
GT10B (Annular combustor)
GT35 (Can-annular combustor)
Power Generation 39
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Dual fuel Injector
STEAM INLET
PURGE HOLES
HCV GAS HOLES
Dual fuel Injector with water and steam
injection
STD PART-POSITIONABLE ELBOW
Gas inlet
Oil inlet
Water inlet
Power Generation 40
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The burner 2
There is one basic philosophy for the lean premix burner: the fuel and air has to be mixed as evenly as possible. The better mixing, the lower NOx.
Choice of swirl strength for good ignition and recirculationLow swirl and weak recirculation is providing an unattached flame with low pressure drop. The mixing in of oxygen depleted recirculation products is quite low. Ignition has to secured by zones with higher fuel concentrations. The flow out from the combustor is quite even.High swirl burners has often flames attached to a flame holder. The recirculation is strong, but in many cases the mixing in of the recirculation flow is not as good as it could be. The exit profile is often distorted by the swirling flows reaching all the way to the turbine.
Power Generation 41
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1)1) Gas fuel is injected along the air inlet slots and is immediately mixed with the air.
2) At the burner exit a lean mixture enters the flame zone, which is stabilised by the vortex breakdown in the inner core of the exit flow
3) The high air flow velocity inside of the burner protects the burner wall against flame flashback
4) Operation with oil No2An oil-water emulsion is injected in the center of the EV cone. The oil-water jet is atomised and partly evaporated; ignition of the vapour occurs in the vortex breakdown zone. NOx formation is reduced and remains below 42 ppm
Swirl Burner Operation
1.
Air
Gas fuel
2.
4.3.
Power Generation 42
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A 2nd generation premix burner
Most lean premixed burners haveA swirl generator which can be axial, radial or tangentialA device to mix in the fuel as evenly as possible often integrated in the swirl generator
Most lean premixed burners has a pilot flame that is supporting the main flame at part load, when the flame temperature tends to be too low
Power Generation 43
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A 3rd generation dual fuel burner
-- A A burnerburner for 10 for 10 --15 ppm 15 ppm NOxNOx
Concentric tubes for fuel supply
Main oil
Main gas Pilot oil
Pilot gas
Power Generation 44
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The DLE dual fuel burner function
Mixing tube Cone Gas fuel andLiquid fuel
Main liquid fuel injection
Main gas fuel injectionPilot gas fuel injection
Flame
Combustor wall
Compr. discharge air
Dry Low Emissions on gas and oil
Combustor hood
Pilot liquid fuel injection
Power Generation 45
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A high swirl burner
Pilot fuel injection with Igniter
Radial Swirlerwith Main fuel injection
lame Holder
Quarl
F
Power Generation 46
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Emissions and pulsations
In a burner with very good mixing it is theoretically possible to come done in NOx to around 5 ppm at 1750K, but
It is hard to do the mixing that wellA very well mixed flame has a tendency to be weak and sensitive to disturbancesInstable flames can induce pulsations and acoustic phenomena in the combustion chamber
In order to have stable combustion a fuel richer zone is arrange somewhere to anker the flame, often designed as a pilot diffusion flame that can be controlled by its own fuel supply. That flame is often producing quite a lot of NOx, maybe 1÷2 ppm/% pilot fuel, so even a small pilot can supply an additional 5 ppm NOx
The pilot flame is often arranged in the centre of the burner, but also at the exit ring
Power Generation 47
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Pulsations
The combustion pulsations are generally of two typesHigh frequency acoustics (1000-3000 Hz) generated by the instationaryheat release in the turbulent shear layers of the swirling jetLow frequency combustion dynamics (50-500Hz) generated by the movements of the flame front
It is possible to design combustion systems without pulsations, often after a period of testing and tuning of the aerodynamics and fuel distribution
But if not successfulthe high frequency can be damped by “Soft walls”the low cycle frequencies can be damped by Helmhold´s dampers
Soft wall
Helmhold´sdamper
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The fuel system
The piping system for distribution of fuel to the burners has basically three pressure drops caused by
The control valveThe fuel injector flow area and calibration nozzleThe piping system losses in bends or due to wall friction
The minimum pressure drop over the control valve must be around 200 kPa to achieve a stable control
The total pressure drop over the burner depends somewhat on the injector design, but a calibration nozzle is most often used to provide
Even flow to all burnersA safety against too high gas flow in case of an injector failure
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A typical gas fuel system for a 18 burner combustor with main and pilot
Ventilation valves
Quick shut-off valves
Gas fuel unit 2, located inside the GT enclosure
Enclosure wall
From gas fuel unit 1
To atmosphere
Gas control valves
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Fuel system pressure losses
The main pressure drops occurs over the burnercontrol valves
The losses in pipes, bends, shut off valves etc are calculated byΔp = λ*ρ*c2/2
The burner pressure drops are calculated byΔp = {m/Aeff}2*1/(2ρ)
Aeff,main = 30 ÷ 60 mm2
Aeff,pilot = 10÷15 mm2
The required pressure drop over the valves is then calculated from the available pressure or
the required gas pressure is calculated for a minimum valve pressure drop of 200 kPa on the coldest day (max power output)
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Fuel system and valves
The fuel valve calculations uses the basic equationm = Ψ*Av*p1/rot(RgTg)
Critical flow
Sub critical flow
1
12 −
⎟⎠⎞
⎜⎝⎛
+=
κκ
κπ crit
The critical pressure ratio
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Fuel valves
Main valve matrix
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70 80 90 100
110
Position %
Effe
ctiv
e ar
ea m
m2
p2/p1=0.20.3
0.4
0.5
0.6
0.7
0.8
0.9
Actual
The fuel valves can of different designs but they generally has an
effective flow area as a function of shaft position
but with a small influence of the pressure ratio
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The Ψ factor
Psi overall
0.250
0.300
0.350
0.400
0.450
0.500
0.550
0.600
0.650
0.700
0.750
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Pressure ratio
psi
1.251.31.351.41.4 approx1.35Psi register
Psi registerp2/p1 psi 1.35 Kkap
0.00 0.6761 0.17510.50 0.6761 0.17510.55 0.6759 0.15760.60 0.6700 0.14010.65 0.6562 0.12260.70 0.6338 0.10510.75 0.6017 0.08760.80 0.5582 0.07000.85 0.5002 0.05250.90 0.4217 0.03501.00 0.2500 0.0000
Psi = psi1.35+Kkap*(kappa-1.35)
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The operation
The gas turbine is very flexible The gas turbine plant is very compact and contains everything needed for the operation, which means that there are a number of systems in the plant (lubrication, fuel distribution and control, ventilation, fire detection and control…..)Quick to start and take up load by a number of preset sequences:
push the button for start and stop of fuel change overControlled from a PCCan be controlled by power turbine load or speed or generator frequencyHas built in safety systems for protection of
Personnel (explosions from fuel leaks or flame out)The unit (overheating of critical parts, over speed etc)
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The start procedure
The start procedure goes like thisThe gas turbine is rotated by an electric motor in order to get an air flow through the combustorThe igniter is activated (spark plug or torch burner)The fuel valve is put in a preset start value and the shut off valve is opened. Ignition has to occur within seconds, otherwise shut down.Speed is increased and fuel flow is ramped upAt some point the turbine is making enough power to accelerate the compressor; the unit is self sustained and the electric motor is phased outAcceleration continues up to idle, where the generator is phased into the gridLoading up to full load in 5 ÷ 10 minutes depending on requirement
Fast loading means lower lifetime on critical partsThe combustor often contains parts that are sensitive to thermal fatigue, but the life of a combustor is mostly limited by oxidation or buckling
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Mechanical drive start
Exhaust temp
GG speed
Fuel flow
Cross ignition
Torch ignition
Self-sustaining
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Part load operation
When the power (fuel flow) is reduced from full load the air flow is also going down and so is the pressure and air temperature
On a single shaft unit the rotor speed is constant and the air flow can be controlled by the inlet guide vanes of the compressor so that the flame temperature is kept high in a wide load rangeOn a twin shaft unit the rotor speed is going down, but not as much as one could wish. The flame temperature drops and flame stability has to be kept up by increasing the pilot flameThere are a number of ways to keep the flame temperature high at part load e.g.
Bleed off of compressor airBypass of airStaging of burners (reducing the number of burners that are fueled)
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Combustion supervision
The combustor is supervised by flame detectors, usually two separate systems to prevent explosions
fuel must not be injected when there is no flame
The burners are usually checked with the turbine exhaust temperature measurements
Deviation in temperatures can indicate burner problems
Some combustors have differential pressure and pulsation measurement (fast pressure transducers)
Some burner have temperature measurements
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Calculation tasks
The task is to design a gas turbine combustion system with certain dataIt is advisable to use the Excel program GTZ-Combustor`s manual version, which can be improved by introduction of a number of iterations and modifications if you like toYou will be assigned a small set of data and from that you have to make some choices, as discussed in this presentationYou will be assigned
a power out put: 18, 26 or 35 MWan application for which you have to discuss and decide on NOx level, burner type and combustor type
– gas pipe line compressor driver– industrial heat &power generation– peak&reserve power
Then you have to go through the design procedure and come up with a combustor wall design, burner type and number/size of burners, cooling and dilution flowsThe result will be your Excel sheet!
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The Excel program
The Excel program consists of a number of sheetsTermo 1: Gas turbine thermodynamic lay out calculationsTermo 2: Gas turbine thermodynamic part load calculation: (fixed geometry)Combustor 1: Film cooled combustor geometry and wall cooling Combustor 2: Convection cooled combustor geometry and wall coolingBurners 1: Nominal design of burners coupled to Termo1
Diffusion, DLE, low oxygen and catalytic burner flowsBurner 2: Part load operation coupled to Termo 2 Fuel system: Fuel system calculationsFuel: Fuel analysis
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The program
It is basically a manual program for educational purpose, but in order to simplify things for you there are
some iterations and couplings between sheets, which can go wrong. Restart by using the Run/test 1/0 button.The calculated m*rotT/p values in Termo 1 must be copied to Termo 2 manually as fixed values when the nominal design is done
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The design steps
On Termo1:put in your nominal data for ambient conditions, TIT and fuel flowmake your choice of burner type 1-4 Iterate air flow, fuel flow, pressure level until you have got what you want in output efficiency and TET (also number of burners and burner size)
You have now determined the main flow areas in the unit Aeff ~ m*rotT/pCopy those values to Termo 2 (the fixed geometry program)In the shaded area you have the relevant data for the combustor, which are copied to the two combustor sheets from Termo 2You have to choose one of them (film cooled or convection cooled)
If there is not air enough for film cooling you have to use convection coolingSet Termo 2 to combustor design conditions
Nominal or worst case? Make a combustor wall geometryMake a wall cooling configuration
If you have done the design at nominal conditions check at worst conditions
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Fuel system
Set Termo 2 to worst conditions = max fuel flow
Assume a design pressure drop across the control valve, typically 200 kPaand pressure drops in the piping system
Find the required fuel pressure (often we want a margin of 5%)
Choose the size of the fuel valve so that is around 85 ÷ 90% open at this condition
If the fuel valve pressure drop is set = 0 the pressure drop is calculated and the valve position can be used to to match the required flow area with the valve area.
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Design sequence for turbine, burner and combustor
Make a turbine lay out in Termo 1
considering TIT, p5, TET and efficiency
Choose a burner type considering the target NOx level.
Adjust the no of burners and/or burner diam. to get the right flow conditions for the required burner λ in Burner 1
Choose a combustor type considering the cooling flow available
Transfer the m*rotT/p values to Termo 2 and set Termo 2 to combustor design conditions
Go to Combustor 1 or 2 and adjust the dilution flow.
Design the combustor wall geometry trying to fulfill the design criteria
Design the wall cooling by adjusting number and diameter of the cooling holes in Combustor 1
Or the height of the cooling ducts in Combustor 2
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Design the fuel system
Set Termo 2 to worst conditions ambient conditions considering the max power output
Assume that the fuel valve should be 85 -90% open with a pressure drop of 200kPa at this condition
Adjust the valve size so that the valve flow area = required flow area
Adjust the necessary fuel inlet pressure