WO2003094265A1 - A gas turbine engine and fuel cell stack combination - Google Patents

A gas turbine engine and fuel cell stack combination Download PDF

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Publication number
WO2003094265A1
WO2003094265A1 PCT/GB2003/001838 GB0301838W WO03094265A1 WO 2003094265 A1 WO2003094265 A1 WO 2003094265A1 GB 0301838 W GB0301838 W GB 0301838W WO 03094265 A1 WO03094265 A1 WO 03094265A1
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WO
WIPO (PCT)
Prior art keywords
fuel cell
cell stack
gas turbine
turbine engine
compressor
Prior art date
Application number
PCT/GB2003/001838
Other languages
French (fr)
Inventor
Gerard Daniel Agnew
Philip Patrick Walsh
Paul Fletcher
Original Assignee
Rolls-Royce Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rolls-Royce Plc filed Critical Rolls-Royce Plc
Priority to AU2003222996A priority Critical patent/AU2003222996A1/en
Publication of WO2003094265A1 publication Critical patent/WO2003094265A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C1/00—Gas-turbine plants characterised by the use of hot gases or unheated pressurised gases, as the working fluid
    • F02C1/04—Gas-turbine plants characterised by the use of hot gases or unheated pressurised gases, as the working fluid the working fluid being heated indirectly
    • F02C1/05—Gas-turbine plants characterised by the use of hot gases or unheated pressurised gases, as the working fluid the working fluid being heated indirectly characterised by the type or source of heat, e.g. using nuclear or solar energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D17/00—Regulating or controlling by varying flow
    • F01D17/10—Final actuators
    • F01D17/12—Final actuators arranged in stator parts
    • F01D17/14—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits
    • F01D17/16—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of nozzle vanes
    • F01D17/162—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of nozzle vanes for axial flow, i.e. the vanes turning around axes which are essentially perpendicular to the rotor centre line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C3/00—Gas-turbine plants characterised by the use of combustion products as the working fluid
    • F02C3/20—Gas-turbine plants characterised by the use of combustion products as the working fluid using a special fuel, oxidant, or dilution fluid to generate the combustion products
    • F02C3/26—Gas-turbine plants characterised by the use of combustion products as the working fluid using a special fuel, oxidant, or dilution fluid to generate the combustion products the fuel or oxidant being solid or pulverulent, e.g. in slurry or suspension
    • F02C3/28—Gas-turbine plants characterised by the use of combustion products as the working fluid using a special fuel, oxidant, or dilution fluid to generate the combustion products the fuel or oxidant being solid or pulverulent, e.g. in slurry or suspension using a separate gas producer for gasifying the fuel before combustion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/08—Heating air supply before combustion, e.g. by exhaust gases
    • F02C7/10—Heating air supply before combustion, e.g. by exhaust gases by means of regenerative heat-exchangers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H01M8/04014—Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2220/00—Application
    • F05D2220/70—Application in combination with
    • F05D2220/74—Application in combination with a gas turbine
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/14—Combined heat and power generation [CHP]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • a GAS TURBINE ENGINE AND FUEL CELL STACK COMBINATION The present invention relates to a gas turbine engine and fuel cell stack combination.
  • SFC specific fuel consumption
  • Recuperated gas turbine engines use heat exchangers to return heat from the final turbine exhaust to pre-heat compressed air entering the combustor. This helps to conserve fuel by raising the combustor air temperature and therefore limiting the amount of fuel needed to achieve the turbine inlet temperature.
  • Our published International patent application 09936688A discloses a small gas turbine engine comprising a centrifugal compressor, a diffuser, a heat exchanger, a combustor and at least one turbine.
  • the compressor has variable inlet guide vanes
  • the diffuser has variable outlet guide vanes
  • the at least one turbine has variable inlet guide vanes so that the flow capacity of each component is independently variable while maintaining the temperature, the pressure ratio and the speed of rotation of the gas turbine engine substantially constant.
  • EP1055809A2 discloses a small gas turbine engine comprising a centrifugal compressor, a diffuser, a heat exchanger, a combustor and at least one turbine.
  • the compressor has variable inlet guide vanes
  • the diffuser has variable outlet guide vanes
  • the combustor has a variable area inlet
  • the at least one turbine has variable inlet guide vanes so that the flow capacity of each component is independently variable while maintaining the temperature, the pressure ratio and the speed of rotation of the gas turbine engine substantially constant.
  • Fuel cells are being developed for electrical power generation.
  • the presence of a catalyst in the fuel cell allows the fuel to react at lower temperatures than for conventional combustion and allows the direct production of electricity.
  • a fuel cell has a thermal efficiency of about 60% compared to about 30 to 45% for a simple cycle gas turbine engine or a reciprocating internal combustion engine.
  • a fuel cell achieves lower exhaust emissions, particularly oxides of nitrogen NOx, due to the lack of conventional combustion.
  • Gas turbine engine and fuel cell combinations are being developed where the fuel cell is arranged between the compressor and the turbine of the gas turbine engine.
  • the fuel cell reaction is made to occur at elevated pressures to increase the power density and reduce specific costs .
  • the gas turbine engine produces shaft output power from the fuel cell exhaust gases and the output power is used to drive an electrical generator to increase the system efficiency. This increases the thermal efficiency to over 70% and lowers the unit cost by a factor of about 3 to 5.
  • Gas turbine engine and fuel cell combinations operate below their maximum power output for most of the time. While operating gas turbine engine and fuel cell combinations at less than maximum power, the operating temperature and the pressure ratio is less than that at maximum power, and this results in lower engine efficiency. Designing the fuel cell stack and any associated heat exchanger to deal with these lower, "off design", temperatures and pressure ratios increases the unit cost.
  • Achieving a competitive unit cost is the single most important barrier to a fuel cell, or a gas turbine engine and fuel cell combination, entering and being successful in the market place.
  • the present invention seeks to provide a novel gas turbine engine and fuel cell stack combination which reduces, preferably overcomes, the above mentioned problems .
  • the present invention provides a gas turbine engine and a fuel cell stack combination, the gas turbine engine comprising a first compressor and a first turbine, the first turbine being arranged to drive the first compressor, the first compressor having variable inlet guide vanes, the first turbine having variable inlet guide vanes, the fuel cell stack having at least one anode chamber and at least one cathode chamber, the first compressor being arranged to supply oxidant to the at least one cathode chamber and the fuel cell stack being arranged to supply hot exhaust gases from the at least one cathode chamber to the first turbine.
  • a second turbine may be arranged downstream of the first turbine, the second turbine having variable inlet guide vanes .
  • the second turbine may be arranged to drive an output shaft.
  • the second turbine may be arranged to drive the output shaft via a gearbox.
  • the first turbine may be arranged to drive an output shaft.
  • the first turbine may be arranged to drive the output shaft via a gearbox.
  • the output shaft is arranged to drive an electrical generator.
  • the first compressor is a centrifugal flow compressor .
  • the first turbine is a radial flow turbine.
  • the second turbine is an axial flow turbine .
  • a diffuser is arranged between the first compressor and the fuel cell stack, the diffuser having variable area guide vanes.
  • the fuel cell stack is arranged to supply hot gases to a combustion chamber and the combustion chamber is arranged to supply hot gases to the first turbine .
  • a heat exchanger is arranged to transfer heat from a position downstream of the first turbine to a position between the first compressor and the solid oxide fuel cell stack to heat the oxidant supplied to the at least one cathode chamber.
  • a heat exchanger may be arranged to transfer heat from a position downstream of the second turbine to a position between the first compressor and the solid oxide fuel cell stack to heat the oxidant supplied to the at least one cathode chamber.
  • Figure 1 is a schematic diagram of a gas turbine engine according to the present invention.
  • Figure 2 is a schematic diagram of an alternative gas turbine engine according to the present invention.
  • Figure 3 is a schematic diagram of another gas turbine engine according to the present invention.
  • Figure 4 is a schematic diagram of a further gas turbine engine according to the present invention.
  • a gas turbine engine and fuel cell stack combination according to the present invention is particularly suitable for industrial use, domestic use, marine vessel use or automotive applications, which operate largely at low power.
  • a gas turbine engine and fuel cell stack combination 10 comprises a gas turbine engine 12 and a fuel cell stack 42.
  • the gas turbine engine 10 comprises an inlet 14, a first centrifugal flow compressor 16, a diffuser 18, a first radial flow turbine 20 and an exhaust 22.
  • the first turbine 20 is arranged to drive the first compressor 16 via a shaft 26.
  • the first turbine 22 is arranged to drive an output shaft 32 via the shaft 26.
  • the output shaft 32 is coupled to any suitable load device, in this example an electric generator 39.
  • the load may also be for example, the driving wheels of a motor vehicle or locomotive, or a propeller of a marine vessel.
  • the inlet duct 14 includes a stage of variable inlet guide vanes 34 upstream of the first centrifugal flow compressor 16.
  • the diffuser includes a stage of variable guide vanes 36.
  • the first radial flow turbine 20 includes a stage of variable inlet guide vanes 38 upstream of the first turbine 20.
  • the fuel cell stack 42 comprises a plurality of solid oxide fuel cells 44, each of which comprises an anode electrode 46, a solid oxide electrolyte 48 and a cathode electrode 50.
  • At least one anode chamber 52 is arranged to supply a fuel, for example hydrogen, to the anode electrodes 46 and at least one cathode chamber 54 is arranged to supply an oxidant, for example oxygen or air, to the cathode electrodes 50.
  • the gas turbine engine and fuel cell stack combination 10 is arranged such that the first centrifugal flow compressor 16 of the gas turbine engine 10 supplies an oxidant, air or oxygen, to the cathode chambers 54 of the solid oxide fuel cells 44 of the fuel cell stack 42.
  • the fuel cell stack 42 is also arranged such that the cathode chambers 54 of the fuel cell stack 42 supplies hot exhaust gases to the first radial flow turbine 20 of the gas turbine engine 10.
  • the solid oxide fuel cell stack 42 produces electricity.
  • the solid oxide fuel cell stack 42 and the electrical generator 39 are connected to a power electronics unit 44.
  • the gas turbine engine and the solid oxide fuel cell stack of the combination 10 both provide electricity, and the power electronics unit 44 supplies electricity to the mains grid, domestic houses, hospital, offices, a marine vessel, locomotive, etc.
  • the gas turbine engine and solid oxide fuel cell stack combination 10 may also provide combined heat and power.
  • the heat generated by the solid oxide fuel cell stack 42 and/or the heat generated by the gas turbine engine 12 are used to provide heating, for example central heating and/or hot water, for domestic houses, hospital, offices, a marine vessel, trains etc.
  • the gas turbine engine and the solid oxide fuel cell stack of the combination 10 may both be arranged to provide electricity and the power electronics unit 44 supplies the electricity to electrical motors which in turn drive the wheels of a vehicle or locomotive or drive a propeller of a marine vessel .
  • the gas turbine engine of the combination 10 may be arranged to drive an output shaft, which in turn drives the wheels of a vehicle or locomotive or drives a propeller of a marine vessel.
  • the solid oxide fuel cell stack 42 of the combination provides electricity and the power electronics unit 44 supplies electricity to electrical motors, which in turn drive the wheels of a vehicle or drive a propeller of a marine vessel and/or provide electricity for the vehicle or marine vessel.
  • FIG 2 is similar to figure 1 but differs in that there is a heat exchanger 23.
  • the exhaust 22 from the first radial flow turbine 20 is arranged to flow through the heat exchanger 23.
  • the oxidant supplied from the first centrifugal flow compressor 16 flows through the heat exchanger 23 to reach the cathode chambers 54 of the solid oxide fuel cell stack 42.
  • the heat exchanger 23 transfers heat from the exhaust gases 22 to the oxidant supplied to the cathode chambers 54 of the solid oxide fuel cell stack 42.
  • FIG 3 is similar to figure 2 but differs in that there is a second turbine 28.
  • the first radial flow turbine 20 is arranged to drive the first centrifugal flow compressor 16 only.
  • the second axial flow turbine 28 is arranged downstream of the first radial flow turbine 20.
  • the second axial flow turbine 28 is provided with variable inlet guide vanes 40.
  • the second axial flow turbine 28 is arranged to drive the electrical generator 39, for example a high frequency alternator, via the output shaft 32.
  • the electrical generator 39 supplies electrical power to the power electronics unit 44.
  • the second axial flow turbine 28 and output shaft 32 may be arranged to drive a synchronous electrical generator 39 via a gearbox, to avoid the cost and efficiency losses of a power electronics unit 44.
  • FIG 4 An alternative gas turbine engine and fuel cell stack combination 310 according to the present invention is shown in figure 4, and like parts are denoted by like numerals.
  • Figure 4 is similar to figure 2 but differs in that there is also a combustor 21.
  • the cathode chambers 54 of the fuel cell stack 42 are arranged to supply the hot exhaust gases to the combustor 21.
  • Fuel is burnt in the hot exhaust gases supplied by the cathode chambers 54 of the fuel cell stack 42 to produce further hot exhaust gases, which are supplied to the first radial flow turbine 20.
  • the main feature of the present invention is that the power output of the gas turbine engine and solid oxide fuel cell stack combination may be varied by changing the oxidant mass flow, whilst the temperature and the pressure at the inlet to the cathode chambers of the solid oxide fuel cell stack remain substantially constant over a wide
  • the oxidant mass flow is varied by adjusting the angles of the variable inlet guide vanes of the first compressor, the variable diffuser vanes of the diffuser and the variable inlet guide vanes of the first turbine and second turbine. This provides many advantages.
  • the substantially constant pressure and temperature in the cathode chambers of the fuel cell stack allows the solid oxide fuel cell stack to operate near to its design point, this improves the efficiency of the combination. At part power, low oxidant flow conditions, the system pressure drops are reduced, which further improves the efficiency of the combination.
  • the temperature levels in the combination may be constrained over the whole operating power range to levels which allow the use of materials and components suitable for use at lower temperatures and hence at least some of the components may be lower cost components. This is particularly beneficial for the heat exchangers .
  • the heat transfer requirement in the gas turbine engine and solid oxide fuel cell combination cycle remains relatively constant, minimising the cost and risk from the heat exchanger.
  • the constant pressure of the oxidant supplied to the cathode chambers of the solid oxide fuel cell stack allows the anode electrodes to operate at a constant temperature, which allows a reduction in unit cost.
  • the constant pressure of the oxidant supplied to the cathode chambers of the solid oxide fuel cell stack avoids relatively high-pressure levels. Hence, this enables the pressure vessel to be designed for use at lower and constant pressure levels and again allows a reduction in unit cost.
  • the constant pressure in the cathode chambers of the solid oxide fuel cell stack minimises damage in various failure cases.
  • variable inlet guide vanes may be used during starting and transients to reduce, or minimise, thermal stresses in the heat exchanger and solid oxide fuel cell stack. Hence, this enables cheaper materials to be used and again allows a reduction in unit cost .
  • the speed of rotation of the shaft may remain above the critical speeds typical of overhung shaft layouts.
  • variable inlet guide vanes of the first compressor and first and second turbines allow control of the compressor surge margin at off design, transient and starting conditions. This increases the design point thermal efficiency and reduces unit cost.
  • variable inlet guide vanes of the first compressor and the variable guide vanes of the first and second turbines allow a lower starting/crank power for the gas turbine engine.
  • variable inlet guide vanes of the first compressor and first and second turbines enable operation over a greater power and/or speed range. Additionally the combination is able to operate with a greater diversity of fuels over a conventional arrangement.
  • the excess oxidant used for cooling the solid oxide fuel cell stack may be varied without altering the key cycle temperatures or pressures. In a conventional arrangement if the fuel is changed then the amount of oxidant used for cooling the solid oxide fuel cell stack must be varied. However, in the conventional arrangement this easily causes temperatures in the solid oxide fuel cell stack or reformer to exceed the acceptable limits.
  • first centrifugal flow compressor it may be equally possible to use a first axial flow compressor.
  • first radial flow turbine it may be equally possible t-o use a first axial flow turbine.
  • second axial flow turbine it may be equally possible to use a second radial flow turbine.
  • present invention has been described with reference to a solid oxide fuel cell stack it may be equally possible to use other types of fuel cell for example molten carbonate fuel cells, solid polymer fuel cells etc.

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Abstract

A gas turbine engine and fuel cell stack combination (10) comprises a gas turbine engine (10) and a fuel cell stack (42). The gas turbine engine (10) comprises a first compressor (16) and a first turbine (20) arranged in flow series. The first turbine (20) is arranged to drive the first compressor (16) and an electrical generator (39). The first compressor (16) has variable inlet guide vanes (34) and the first turbine (20) has variable inlet guide vanes (38). The fuel cell stack (42) comprises at least one anode chamber (52) and at least one cathode chamber (54) and a plurality of fuel cells (44). The first compressor (16) supplies oxidant to the cathode chamber (54) and the cathode chamber (54) supplies hot exhaust gases to the first turbine (20). The power output of the gas turbine engine and fuel cell stack (10) combination may be varied by changing the oxidant mass flow, whilst the temperature and the pressure at the inlet to the cathode chambers (54) of the fuel cell stack (42) remain substantially constant over a wide operating range.

Description

A GAS TURBINE ENGINE AND FUEL CELL STACK COMBINATION The present invention relates to a gas turbine engine and fuel cell stack combination.
One main consideration for the operation of gas turbine engines is the specific fuel consumption value
(SFC) , measured in kg/kWhrs. In general for certain gas turbine engine applications especially marine, automotive, aero and even industrial, a significant proportion of operation is at low power. A gas turbine engine utilises hot working fluid expanding through a given expansion ratio in the turbines which produces a power in excess of that required for the compressor to produce the corresponding pressure ratio. This is due to the pressure and the temperature ratios being proportional to one another during compression or expansion in the simple gas turbine engine cycle, which means that temperature change and hence work,, is proportional to the initial temperature level. Therefore reducing the amount of fuel available at part power results in reduced temperature levels and hence a reduced speed and pressure ratio thus resulting in a significant increase in specific fuel consumption (SFC) .
Recuperated gas turbine engines use heat exchangers to return heat from the final turbine exhaust to pre-heat compressed air entering the combustor. This helps to conserve fuel by raising the combustor air temperature and therefore limiting the amount of fuel needed to achieve the turbine inlet temperature.
Our published International patent application 09936688A discloses a small gas turbine engine comprising a centrifugal compressor, a diffuser, a heat exchanger, a combustor and at least one turbine. The compressor has variable inlet guide vanes, the diffuser has variable outlet guide vanes and the at least one turbine has variable inlet guide vanes so that the flow capacity of each component is independently variable while maintaining the temperature, the pressure ratio and the speed of rotation of the gas turbine engine substantially constant.
Our published European patent application EP1055809A2 discloses a small gas turbine engine comprising a centrifugal compressor, a diffuser, a heat exchanger, a combustor and at least one turbine. The compressor has variable inlet guide vanes, the diffuser has variable outlet guide vanes, the combustor has a variable area inlet and the at least one turbine has variable inlet guide vanes so that the flow capacity of each component is independently variable while maintaining the temperature, the pressure ratio and the speed of rotation of the gas turbine engine substantially constant.
Fuel cells are being developed for electrical power generation. The presence of a catalyst in the fuel cell allows the fuel to react at lower temperatures than for conventional combustion and allows the direct production of electricity. A fuel cell has a thermal efficiency of about 60% compared to about 30 to 45% for a simple cycle gas turbine engine or a reciprocating internal combustion engine. A fuel cell achieves lower exhaust emissions, particularly oxides of nitrogen NOx, due to the lack of conventional combustion.
Gas turbine engine and fuel cell combinations are being developed where the fuel cell is arranged between the compressor and the turbine of the gas turbine engine. The fuel cell reaction is made to occur at elevated pressures to increase the power density and reduce specific costs . In addition the gas turbine engine produces shaft output power from the fuel cell exhaust gases and the output power is used to drive an electrical generator to increase the system efficiency. This increases the thermal efficiency to over 70% and lowers the unit cost by a factor of about 3 to 5. Gas turbine engine and fuel cell combinations operate below their maximum power output for most of the time. While operating gas turbine engine and fuel cell combinations at less than maximum power, the operating temperature and the pressure ratio is less than that at maximum power, and this results in lower engine efficiency. Designing the fuel cell stack and any associated heat exchanger to deal with these lower, "off design", temperatures and pressure ratios increases the unit cost.
Achieving a competitive unit cost is the single most important barrier to a fuel cell, or a gas turbine engine and fuel cell combination, entering and being successful in the market place.
Accordingly the present invention seeks to provide a novel gas turbine engine and fuel cell stack combination which reduces, preferably overcomes, the above mentioned problems .
Accordingly the present invention provides a gas turbine engine and a fuel cell stack combination, the gas turbine engine comprising a first compressor and a first turbine, the first turbine being arranged to drive the first compressor, the first compressor having variable inlet guide vanes, the first turbine having variable inlet guide vanes, the fuel cell stack having at least one anode chamber and at least one cathode chamber, the first compressor being arranged to supply oxidant to the at least one cathode chamber and the fuel cell stack being arranged to supply hot exhaust gases from the at least one cathode chamber to the first turbine.
A second turbine may be arranged downstream of the first turbine, the second turbine having variable inlet guide vanes . The second turbine may be arranged to drive an output shaft. The second turbine may be arranged to drive the output shaft via a gearbox.
The first turbine may be arranged to drive an output shaft. The first turbine may be arranged to drive the output shaft via a gearbox. Preferably the output shaft is arranged to drive an electrical generator.
Preferably the first compressor is a centrifugal flow compressor . Preferably the first turbine is a radial flow turbine. Preferably the second turbine is an axial flow turbine .
Preferably a diffuser is arranged between the first compressor and the fuel cell stack, the diffuser having variable area guide vanes.
Preferably the fuel cell stack is arranged to supply hot gases to a combustion chamber and the combustion chamber is arranged to supply hot gases to the first turbine . Preferably a heat exchanger is arranged to transfer heat from a position downstream of the first turbine to a position between the first compressor and the solid oxide fuel cell stack to heat the oxidant supplied to the at least one cathode chamber. A heat exchanger may be arranged to transfer heat from a position downstream of the second turbine to a position between the first compressor and the solid oxide fuel cell stack to heat the oxidant supplied to the at least one cathode chamber. The present invention will be more fully described by way of example with reference to the accompanying drawings in which : -
Figure 1 is a schematic diagram of a gas turbine engine according to the present invention. Figure 2 is a schematic diagram of an alternative gas turbine engine according to the present invention.
Figure 3 is a schematic diagram of another gas turbine engine according to the present invention.
Figure 4 is a schematic diagram of a further gas turbine engine according to the present invention. A gas turbine engine and fuel cell stack combination according to the present invention is particularly suitable for industrial use, domestic use, marine vessel use or automotive applications, which operate largely at low power.
A gas turbine engine and fuel cell stack combination 10 according to the present invention, as shown in figure 1, comprises a gas turbine engine 12 and a fuel cell stack 42. The gas turbine engine 10 comprises an inlet 14, a first centrifugal flow compressor 16, a diffuser 18, a first radial flow turbine 20 and an exhaust 22. The first turbine 20 is arranged to drive the first compressor 16 via a shaft 26. The first turbine 22 is arranged to drive an output shaft 32 via the shaft 26. The output shaft 32 is coupled to any suitable load device, in this example an electric generator 39. However, the load may also be for example, the driving wheels of a motor vehicle or locomotive, or a propeller of a marine vessel.
The inlet duct 14 includes a stage of variable inlet guide vanes 34 upstream of the first centrifugal flow compressor 16. The diffuser includes a stage of variable guide vanes 36. The first radial flow turbine 20 includes a stage of variable inlet guide vanes 38 upstream of the first turbine 20. The fuel cell stack 42 comprises a plurality of solid oxide fuel cells 44, each of which comprises an anode electrode 46, a solid oxide electrolyte 48 and a cathode electrode 50. At least one anode chamber 52 is arranged to supply a fuel, for example hydrogen, to the anode electrodes 46 and at least one cathode chamber 54 is arranged to supply an oxidant, for example oxygen or air, to the cathode electrodes 50.
The gas turbine engine and fuel cell stack combination 10 is arranged such that the first centrifugal flow compressor 16 of the gas turbine engine 10 supplies an oxidant, air or oxygen, to the cathode chambers 54 of the solid oxide fuel cells 44 of the fuel cell stack 42. The fuel cell stack 42 is also arranged such that the cathode chambers 54 of the fuel cell stack 42 supplies hot exhaust gases to the first radial flow turbine 20 of the gas turbine engine 10.
The solid oxide fuel cell stack 42 produces electricity. The solid oxide fuel cell stack 42 and the electrical generator 39 are connected to a power electronics unit 44. In this arrangement the gas turbine engine and the solid oxide fuel cell stack of the combination 10 both provide electricity, and the power electronics unit 44 supplies electricity to the mains grid, domestic houses, hospital, offices, a marine vessel, locomotive, etc. The gas turbine engine and solid oxide fuel cell stack combination 10 may also provide combined heat and power. In this case the heat generated by the solid oxide fuel cell stack 42 and/or the heat generated by the gas turbine engine 12 are used to provide heating, for example central heating and/or hot water, for domestic houses, hospital, offices, a marine vessel, trains etc.
Alternatively in another arrangement the gas turbine engine and the solid oxide fuel cell stack of the combination 10 may both be arranged to provide electricity and the power electronics unit 44 supplies the electricity to electrical motors which in turn drive the wheels of a vehicle or locomotive or drive a propeller of a marine vessel .
Alternatively in another arrangement the gas turbine engine of the combination 10 may be arranged to drive an output shaft, which in turn drives the wheels of a vehicle or locomotive or drives a propeller of a marine vessel. The solid oxide fuel cell stack 42 of the combination provides electricity and the power electronics unit 44 supplies electricity to electrical motors, which in turn drive the wheels of a vehicle or drive a propeller of a marine vessel and/or provide electricity for the vehicle or marine vessel.
A further gas turbine engine and fuel cell stack combination 110 according to the present invention is shown in figure 2, and like parts are denoted by like numerals. Figure 2 is similar to figure 1 but differs in that there is a heat exchanger 23. In this embodiment the exhaust 22 from the first radial flow turbine 20 is arranged to flow through the heat exchanger 23. The oxidant supplied from the first centrifugal flow compressor 16 flows through the heat exchanger 23 to reach the cathode chambers 54 of the solid oxide fuel cell stack 42. Thus the heat exchanger 23 transfers heat from the exhaust gases 22 to the oxidant supplied to the cathode chambers 54 of the solid oxide fuel cell stack 42.
Another gas turbine engine and fuel cell stack combination 210 according to the present invention is shown in figure 3, and like parts are denoted by like numerals. Figure 3 is similar to figure 2 but differs in that there is a second turbine 28. In this embodiment the first radial flow turbine 20 is arranged to drive the first centrifugal flow compressor 16 only. The second axial flow turbine 28 is arranged downstream of the first radial flow turbine 20. The second axial flow turbine 28 is provided with variable inlet guide vanes 40. The second axial flow turbine 28 is arranged to drive the electrical generator 39, for example a high frequency alternator, via the output shaft 32. The electrical generator 39 supplies electrical power to the power electronics unit 44. Alternatively the second axial flow turbine 28 and output shaft 32 may be arranged to drive a synchronous electrical generator 39 via a gearbox, to avoid the cost and efficiency losses of a power electronics unit 44.
An alternative gas turbine engine and fuel cell stack combination 310 according to the present invention is shown in figure 4, and like parts are denoted by like numerals. Figure 4 is similar to figure 2 but differs in that there is also a combustor 21. In this embodiment the cathode chambers 54 of the fuel cell stack 42 are arranged to supply the hot exhaust gases to the combustor 21. Fuel is burnt in the hot exhaust gases supplied by the cathode chambers 54 of the fuel cell stack 42 to produce further hot exhaust gases, which are supplied to the first radial flow turbine 20.
The main feature of the present invention is that the power output of the gas turbine engine and solid oxide fuel cell stack combination may be varied by changing the oxidant mass flow, whilst the temperature and the pressure at the inlet to the cathode chambers of the solid oxide fuel cell stack remain substantially constant over a wide
*. operating range. The oxidant mass flow is varied by adjusting the angles of the variable inlet guide vanes of the first compressor, the variable diffuser vanes of the diffuser and the variable inlet guide vanes of the first turbine and second turbine. This provides many advantages.
The substantially constant pressure and temperature in the cathode chambers of the fuel cell stack allows the solid oxide fuel cell stack to operate near to its design point, this improves the efficiency of the combination. At part power, low oxidant flow conditions, the system pressure drops are reduced, which further improves the efficiency of the combination.
The temperature levels in the combination may be constrained over the whole operating power range to levels which allow the use of materials and components suitable for use at lower temperatures and hence at least some of the components may be lower cost components. This is particularly beneficial for the heat exchangers .
The heat transfer requirement in the gas turbine engine and solid oxide fuel cell combination cycle remains relatively constant, minimising the cost and risk from the heat exchanger.
The constant pressure of the oxidant supplied to the cathode chambers of the solid oxide fuel cell stack allows the anode electrodes to operate at a constant temperature, which allows a reduction in unit cost.
The constant pressure of the oxidant supplied to the cathode chambers of the solid oxide fuel cell stack avoids relatively high-pressure levels. Hence, this enables the pressure vessel to be designed for use at lower and constant pressure levels and again allows a reduction in unit cost.
The constant pressure in the cathode chambers of the solid oxide fuel cell stack minimises damage in various failure cases.
The variable inlet guide vanes may be used during starting and transients to reduce, or minimise, thermal stresses in the heat exchanger and solid oxide fuel cell stack. Hence, this enables cheaper materials to be used and again allows a reduction in unit cost .
The speed of rotation of the shaft may remain above the critical speeds typical of overhung shaft layouts.
The variable inlet guide vanes of the first compressor and first and second turbines allow control of the compressor surge margin at off design, transient and starting conditions. This increases the design point thermal efficiency and reduces unit cost.
The variable inlet guide vanes of the first compressor and the variable guide vanes of the first and second turbines allow a lower starting/crank power for the gas turbine engine.
The variable inlet guide vanes of the first compressor and first and second turbines enable operation over a greater power and/or speed range. Additionally the combination is able to operate with a greater diversity of fuels over a conventional arrangement. The excess oxidant used for cooling the solid oxide fuel cell stack may be varied without altering the key cycle temperatures or pressures. In a conventional arrangement if the fuel is changed then the amount of oxidant used for cooling the solid oxide fuel cell stack must be varied. However, in the conventional arrangement this easily causes temperatures in the solid oxide fuel cell stack or reformer to exceed the acceptable limits.
Furthermore, it is possible to provide a conventional combustor to increase power for peak load demands.
Although the invention has been described with reference to a first centrifugal flow compressor it may be equally possible to use a first axial flow compressor. Although the invention has been described with reference to a first radial flow turbine it may be equally possible t-o use a first axial flow turbine. Although the invention has been described with reference to a second axial flow turbine it may be equally possible to use a second radial flow turbine. Although the present invention has been described with reference to a solid oxide fuel cell stack it may be equally possible to use other types of fuel cell for example molten carbonate fuel cells, solid polymer fuel cells etc.

Claims

Claims : -
1. A gas turbine engine and a fuel cell stack combination (10) , the gas turbine engine (12) comprising a first compressor (16) and a first turbine (20) , the first turbine (20) being arranged to drive the first compressor (16), the fuel cell stack (42) having at least one anode chamber (52) and at least one cathode chamber (54), the first compressor (16) being arranged to supply an oxidant to the at least one cathode chamber (54) and the fuel cell stack (42) being arranged to supply hot exhaust gases from the at least one cathode chamber (54) to the first turbine (20) , characterised in that the first compressor (16) having variable inlet guide vanes (34), the first turbine (20) having variable inlet guide vanes (38) .
2. A gas turbine engine and a fuel cell stack combination as claimed in claim 1 wherein a second turbine (28) is arranged downstream of the first turbine (20) , the second turbine (28) having variable inlet guide vanes (40).
3. A gas turbine engine and a fuel cell stack combination as claimed in claim 2 wherein the second turbine (28) is arranged to drive an output shaft (32) .
4. A gas turbine engine and a fuel cell stack combination as claimed in claim 3 wherein the second turbine (28) is arranged to drive the output shaft (32) via a gearbox.
5. A gas turbine engine and a fuel cell stack combination as claimed in claim 1 wherein the first turbine (20) is arranged to drive an output shaft (32) .
6. A gas turbine engine and a fuel cell stack combination as claimed in claim 5 wherein the first turbine (20) is arranged to drive the output shaft (32) via a gearbox.
7. A gas turbine engine and a fuel cell stack combination as claimed in claim 3, claim 4, claim 5 or claim 6 wherein the output shaft (32) is arranged to drive an electrical generator (39) .
8. A gas turbine engine and a fuel cell stack combination as claimed in any of claims 1 to 7 wherein the first compressor (16) is a centrifugal flow compressor.
9. A gas turbine engine and a fuel cell stack combination as claimed in any of claims 1 to 8 wherein the first turbine (20) is a radial flow turbine.
10. A gas turbine engine and a fuel cell stack combination as claimed in claim 2 wherein the second turbine (28) is an axial flow turbine.
11. A gas turbine engine and a fuel cell stack combination as claimed in any of claims 1 to 10 wherein a diffuser is arranged between the first compressor (16) and the fuel cell stack (42), the diffuser having variable area guide vanes (36) .
12. A gas turbine engine and a fuel cell stack combination as claimed in any of claims 1 to 11 wherein the fuel cell stack (42) is arranged to supply hot gases from the at least one cathode chamber (54) to a combustion chamber (21) and the combustion chamber (21) is arranged to supply hot gases to the first turbine (20) .
13. A gas turbine engine and a fuel cell stack combination as claimed in any of claims 1 to 12 wherein a heat exchanger (23) is arranged to transfer heat from a position downstream of the first turbine (20) to a position between the first compressor (16) and the solid oxide fuel cell stack (42) to heat the oxidant supplied to the at least one cathode chamber (54) .
14. A gas turbine engine and a fuel cell stack combination as claimed in claim 13 wherein the heat exchanger (23) is arranged to transfer heat from a position downstream of the second turbine (28) to a position between the first compressor (16) and the solid oxide fuel cell stack (42) to heat the oxidant supplied to the at least one cathode chamber (54 ) .
15. A gas turbine engine and a fuel cell stack combination as claimed in any of claims 1 to 14 wherein the fuel cell stack (42) is a solid oxide fuel cell stack.
PCT/GB2003/001838 2002-05-03 2003-04-30 A gas turbine engine and fuel cell stack combination WO2003094265A1 (en)

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GB0210186A GB2388160A (en) 2002-05-03 2002-05-03 A gas turbine engine and fuel cell stack combination

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