Design of a Gas turbine combustion system

Transcription

1 Design of a Gas turbine combustion system Torsten Strand torsten.strand@siemens.com Power Generation 1

2 Content The design requirements, criteria and targets The overall design process The gas turbine cycle: Excel calculations Burner and cooling mass flows: Design calculations Burner type: lean premixed, diffusion flame or something in between Combustor heat balance, choice of combustor design: Excel calculations The component designs burners combustor : Excel calculations fuel system : Excel calculations Ignition and supervision systems Operation Start up Part load Power Generation 2

3 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 compressors 40% 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 interest Fuel 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 3

4 Case 1 Gas Turbine in Simple Cycle Gas Turbine 63.6 % losses 100 % fuel 36.4 % electricity Pgt MW Pst 0 MW Paux 0.10 MW Pnet MW Heat duty 0 MJ/s Qfired MJ/s Alfa --- Net electrical Power efficiency Generation 36.4 % 4 Net total efficiency 36.4 %

5 Case 2 Gas Turbine in Cogeneration Cycle 12 % losses 1-pressure HRSG 52.2 % process heat 100 % fuel Gas Turbine 35.9 % electricity Pgt MW Pst 0 MW Paux 0.23 MW Pnet MW Heat duty 63.4 MJ/s Qfired MJ/s Alfa Net Power electrical Generation efficiency 35.9 % 5 Net total efficiency 88.1 %

6 Case 3 Gas Turbine in Combined Cycle 100 % fuel 2-pressure HRSG Gas Turbine 12 % losses 35.9 % electricity 520 deg C 31 deg C Pgt MW Pst MW Paux 0.70 MW Pnet MW Heat duty 0 MJ/s Qfired MJ/s Steam Turbine (condensing) 31 deg C 27 deg C 35 % losses 16.8 % electricity 15 deg C Alfa --- Net electrical efficiency 52.7 % Net total efficiency 52.7 % Power Generation 6

7 Case 4 Gas Turbine in Combined Cycle 11 % losses Steam Turbine (district heating) 2-pressure HRSG Gas Turbine 100 % fuel 35.9 % electricity 510 deg C 78 deg C 78 deg C 11.3 % electricity 42.1 % heat 90 deg C 60 deg C Pgt MW Pst MW Paux 0.62 MW Pnet MW Heat duty 51.1 MJ/s Qfired MJ/s Alfa Net electrical Power efficiency Generation 47.2 % 7 Net total efficiency 89.3 %

8 Well, we will try! Is it possible to use the same design for both applications? 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 8

9 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 C From experience the turbine cooling flow will then be around 16% 95MWth TIT 35MWe Turbine cooling Power Generation 9

10 Turbine Inlet Temperature and emissions Turbine Inlet Temperature C and NOX Jet Engines Single Crystal Blades GT200 GT10B/C GT35/GT120 Ceramics Steam Cooling GTX100 Stationary Gas Turbines Year Power Generation 10

11 The gas turbine cycle T p5, t5m t5 Tflame η ct = (t5m - t6)/(t5m - t6s) p3, t3 η c = (t3s - t2)/(t3 - t2) p6, t6 p7, t7 η pt = (t6m - t7)/(t6m - t7s) p2, t2 s Power Generation 11

12 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 restrictors In order to pass a certain flow at a certain temperature there is an associated flow area/pressure combination The flow area is determined by the turbine inlet guide vanes Inner/outer diameter Exit 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 useful m*rot(t)/p = constant Power Generation 12

13 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/p the 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 13

14 The gas turbine cycle T Tflame p5, t5m t5 η ct = (t5m - t6)/(t5m - t6s) p3, t3 p6, t6 η pt = (t6m - t7)/(t6m - t7s) η c = (t3s - t2)/(t3 - t2) p7, t7 p2, t2 95Mth 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! TIT 35MWe Turbine cooling Power Generation 6 Power Generation 14

15 SGT-600, Industrial gas turbine Gas turbine principle & components Power Generation 15

16 The core engine 2 Now we need to choose the pressure level for the turbine inlet There 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 C 1600 kpa η=37.6% TET=526 C T3=413 C 1500 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 air the 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 16

17 The combustor 1 Now we have basic full load data for the combustor Air flow to the combustor: 82.8/426/1785 kg/s/ C/kPa Fuel 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 2.02 kg/s 84.8 kg/s 1300 C 1700kPa Power Generation 17

18 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 Φ = 1/λ NOx ppmv Lean Premix Combustion Diffusion flames Water Injection Steam Injection Fuel/Air Equivalence Ratio Power Generation 18

19 Diffusion type dual fuel Injector Water inlet STD PART- POSITIONABLE ELBOW 2100K HCV GAS HOLES PURGE HOLES STEAM INLET Gas inlet Air Oil inlet Dual fuel Injector for gas and oil with water and steam injection Power Generation 19

20 NOx and CO vs Flame Temperature NOx ppm 50 EV Burner DLE Gas AEV Burner DLE Gas & Oil NOx CO ppm CO 30 Low oxygen burner 20 Catalytic burner Flame Temp K - Advanced DLE burners - Power Generation 20

21 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 21

22 The combustor 2 Now we have the basic flow data for the combustor Air flow to the burner: 65/426/1785 kg/s/ C/kPa Fuel flow: 2.02 kg/s Wall cooling flow: 17/426/1785 kg/s/ C/kPa 2.02 kg/s 84 kg/s 65 kg/s 1300 C 1700kPa 17 kg/s 426 C 1785kPa Power Generation 22

23 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, which ought to be enough for a film cooled sheet metal combustor 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 23

24 Wall cooling designs The shown wall design is the traditional one for film cooled combustors. Several similar designs with improved performance are in use Impingement Convection 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 Power Generation 24

25 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*[tgas 4 Twall 4 ] 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 surface Q = qhot*a = m*cp*(565-tcool) The length of a section depends of course on the design but mm is common The rings are laser drilled, rolled to form and seam welded in a fixture Power Generation 25

26 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 = 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 26

27 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 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 ms 15 ms which gives a axial length of around 600 mm Now it is time to make a choice of combustor type Annular Can-annular Tilted or in line with the flow Power Generation 27

28 Annular versus can-annular The annular combustor has compared to the can-annular type less wall surface area to cool fewer auxiliaries Spark plugs Flame detectors Annular combustors are used in almost all jet engines and many high temperature industrial turbines The can-annular design has most often fewer but larger burners transition 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 28

29 A GE can combustor Premixed Pilot Main swirl premixers Transition duct Power Generation 29

30 GE Frame 5 Power Generation 30

31 Siemens G30 Combustor Concept Pilot Burner Main Burner Double Skin Impingement Cooled Combustor Power Generation 31

32 . Annular combustor for Siemens SGT 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) DLE combustor for 25 ppmv with EV burners since 1991 Power Generation 32

33 Flows in conventional annular combustor Primary injection Primary zone Secondary injection Turbulence and mixing by primary and secondary jets Power Generation 33

34 Annular combustor types Tilted annular combustor with removable burners for easier maintenance In line annular combustor with burners fixed to the combustion chamber Power Generation 34

35 Annular combustor dimensions Assume tentatively outer radius inner radius height at the combustor front panel: at combustor exit: 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 Radius mm Combustor wall design Outer wall Inner wall are important aspects as well as manufacturing aspects Axial position mm Power Generation 35

36 Combustor re-circulating flow 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 Radius mm Combustor wall design Axial position mm Power Generation 36

37 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 37

38 DLE evolution, GT MW -history Residence time reduced by using many small burners, with short flames: introduced 1986, NOx 75 ppmv on gas Lean premix combustion in two-slotted cone, multiple burners: introduced 1991, NOx 25 ppmv on gas Lean premix combustion in four-slotted cone + mixing tube, multiple burners: introduced 1999, NOx < 15 ppmv on gas Single burner 1st gen. DLE 2nd gen. DLE 3rd gen. DLE GT10B (Annular combustor) Used in: GTX100 GT10B&C GT35C GT35 (Can-annular combustor) Silo Combustors Annular Combustors Power Generation 38

39 Dual fuel Injector Water inlet STD PART- POSITIONABLE ELBOW HCV GAS HOLES PURGE HOLES STEAM INLET Gas inlet Oil inlet Dual fuel Injector with water and steam injection Power Generation 39

40 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 recirculation Low 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 40

41 Swirl Burner Operation Gas fuel 1) Gas fuel is injected along the air inlet slots and is immediately mixed with the air. 3. Air 4. 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 No2 An oil-water emulsion is injected in the center of the EV cone. The oilwater 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 Power Generation 41

42 A 2nd generation premix burner Most lean premixed burners have A swirl generator which can be axial, radial or tangential A 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 42

43 A 3rd generation dual fuel burner Main gas Pilot oil Main oil Pilot gas Concentric tubes for fuel supply - A burner for ppm NOx Power Generation 43

44 The DLE dual fuel burner function Combustor wall Mixing tube Cone Main liquid fuel injection Gas fuel and Liquid fuel Combustor hood Flame Compr. discharge air Pilot gas fuel injection Pilot liquid fuel injection Main gas fuel injection Dry Low Emissions on gas and oil Power Generation 44

45 Pilot fuel injection with Igniter A high swirl burner Radial Swirler with Main fuel injection Quarl Flame Holder Power Generation 45

46 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 well A very well mixed flame has a tendency to be weak and sensitive to disturbances Instable 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 46

47 Pulsations The combustion pulsations are generally of two types High frequency acoustics ( Hz) generated by the instationary heat release in the turbulent shear layers of the swirling jet Low 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 successful the high frequency can be damped by Soft walls the low cycle frequencies can be damped by Helmhold s dampers Helmhold s damper Soft wall Power Generation 47

48 The fuel system The piping system for distribution of fuel to the burners has basically three pressure drops caused by The control valve The fuel injector flow area and calibration nozzle The 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 burners A safety against too high gas flow in case of an injector failure Power Generation 48

49 A typical gas fuel system for a 18 burner combustor with main and pilot Gas fuel unit 2, located inside the GT enclosure Enclosure wall Quick shut-off valves Gas control valves From gas fuel unit 1 To atmosphere Ventilation valves Power Generation 49

50 Fuel system pressure losses The main pressure drops occurs over the burner control valves The losses in pipes, bends, shut off valves etc are calculated by Δp = λ*ρ*c 2 /2 The burner pressure drops are calculated by Δp = {m/a eff } 2 *1/(2ρ) Aeff,main = mm 2 Aeff,pilot = mm 2 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) Power Generation 50

51 Fuel system and valves The fuel valve calculations uses the basic equation m = Ψ*Av*p1/rot(RgTg) Critical flow The critical pressure ratio π crit = κ κ 1 2 κ + 1 Sub critical flow Power Generation 51

52 Fuel valves 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 Effective area mm Main valve matrix Position % 11 0 p2/p1= Actual Power Generation 52

53 The Ψ factor Psi overall psi approx 1.35 Psi register Psi register p2/p1 psi 1.35 Kkap Psi = psi1.35+kkap*(kappa-1.35) Pressure ratio Power Generation 53

54 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 over Controlled from a PC Can be controlled by power turbine load or speed or generator frequency Has built in safety systems for protection of Personnel (explosions from fuel leaks or flame out) The unit (overheating of critical parts, over speed etc) Power Generation 54

55 The start procedure The start procedure goes like this The gas turbine is rotated by an electric motor in order to get an air flow through the combustor The 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 up At some point the turbine is making enough power to accelerate the compressor; the unit is self sustained and the electric motor is phased out Acceleration continues up to idle, where the generator is phased into the grid Loading up to full load in 5 10 minutes depending on requirement Fast loading means lower lifetime on critical parts The combustor often contains parts that are sensitive to thermal fatigue, but the life of a combustor is mostly limited by oxidation or buckling Power Generation 55

56 Mechanical drive start Exhaust temp GG speed Fuel flow Self-sustaining Cross ignition Torch ignition Power Generation 56

57 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 range On 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 flame There are a number of ways to keep the flame temperature high at part load e.g. Bleed off of compressor air Bypass of air Staging of burners (reducing the number of burners that are fueled) Power Generation 57

58 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 Power Generation 58

59 Calculation tasks The task is to design a gas turbine combustion system with certain data It 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 to You will be assigned a small set of data and from that you have to make some choices, as discussed in this presentation You will be assigned a power out put: 18, 26 or 35 MW an 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 flows The result will be your Excel sheet! Power Generation 59

60 The Excel program The Excel program consists of a number of sheets Termo 1: Gas turbine thermodynamic lay out calculations Termo 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 cooling Burners 1: Nominal design of burners coupled to Termo1 Diffusion, DLE, low oxygen and catalytic burner flows Burner 2: Part load operation coupled to Termo 2 Fuel system: Fuel system calculations Fuel: Fuel analysis Power Generation 60

61 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 Power Generation 61

62 The design steps On Termo1: put in your nominal data for ambient conditions, TIT and fuel flow make 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/p Copy 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 2 You 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 cooling Set Termo 2 to combustor design conditions Nominal or worst case? Make a combustor wall geometry Make a wall cooling configuration If you have done the design at nominal conditions check at worst conditions Power Generation 62

63 Fuel system Set Termo 2 to worst conditions = max fuel flow Assume a design pressure drop across the control valve, typically 200 kpa and 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. Power Generation 63

64 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 Power Generation 64

65 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 necessary fuel inlet pressure Adjust the valve size so that the valve flow area = required flow area Power Generation 65