EP2946085A1 - Hydrogen flushed combustion chamber - Google Patents

Hydrogen flushed combustion chamber

Info

Publication number
EP2946085A1
EP2946085A1 EP13704722.1A EP13704722A EP2946085A1 EP 2946085 A1 EP2946085 A1 EP 2946085A1 EP 13704722 A EP13704722 A EP 13704722A EP 2946085 A1 EP2946085 A1 EP 2946085A1
Authority
EP
European Patent Office
Prior art keywords
hydrogen
reformer
gas
exhaust gas
prechamber
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP13704722.1A
Other languages
German (de)
French (fr)
Inventor
Michele SCHILIRÒ
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Caterpillar Energy Solutions GmbH
Original Assignee
Caterpillar Energy Solutions GmbH
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 Caterpillar Energy Solutions GmbH filed Critical Caterpillar Energy Solutions GmbH
Publication of EP2946085A1 publication Critical patent/EP2946085A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B39/00—Component parts, details, or accessories relating to, driven charging or scavenging pumps, not provided for in groups F02B33/00 - F02B37/00
    • F02B39/02—Drives of pumps; Varying pump drive gear ratio
    • F02B39/08—Non-mechanical drives, e.g. fluid drives having variable gear ratio
    • F02B39/10—Non-mechanical drives, e.g. fluid drives having variable gear ratio electric
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N5/00—Exhaust or silencing apparatus combined or associated with devices profiting by exhaust energy
    • F01N5/02—Exhaust or silencing apparatus combined or associated with devices profiting by exhaust energy the devices using heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N5/00—Exhaust or silencing apparatus combined or associated with devices profiting by exhaust energy
    • F01N5/04—Exhaust or silencing apparatus combined or associated with devices profiting by exhaust energy the devices using kinetic energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B19/00—Engines characterised by precombustion chambers
    • F02B19/12—Engines characterised by precombustion chambers with positive ignition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B33/00—Engines characterised by provision of pumps for charging or scavenging
    • F02B33/32—Engines with pumps other than of reciprocating-piston type
    • F02B33/34—Engines with pumps other than of reciprocating-piston type with rotary pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/0639—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels
    • F02D19/0642—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions
    • F02D19/0644—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions the gaseous fuel being hydrogen, ammonia or carbon monoxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M25/00—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture
    • F02M25/10—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture adding acetylene, non-waterborne hydrogen, non-airborne oxygen, or ozone
    • F02M25/12—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture adding acetylene, non-waterborne hydrogen, non-airborne oxygen, or ozone the apparatus having means for generating such gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M27/00—Apparatus for treating combustion-air, fuel, or fuel-air mixture, by catalysts, electric means, magnetism, rays, sound waves, or the like
    • F02M27/02—Apparatus for treating combustion-air, fuel, or fuel-air mixture, by catalysts, electric means, magnetism, rays, sound waves, or the like by catalysts
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/30—Use of alternative fuels, e.g. biofuels

Definitions

  • the present invention relates to a procedure for running a spark-ignited gas engine with a combustion chamber generating an exhaust gas stream with at least one prechamber spark plug, and with a hydrogen source, said source supplying a prechamber of said spark plug with hydrogen, and an injector, said injector being connected to the prechamber for flushing the prechamber with hydrogen, whereby the combustion chamber is loaded with a gas air mixture having a value lambda ⁇ of at least 1.6.
  • EP 0 770 171 Bl discloses ignition devices for internal combustion engines, and more particularly hydrogen assisted jet ignition (HAJI) devices for improving combustion efficiency.
  • HJI hydrogen assisted jet ignition
  • the term "hydrogen” is intended to include hydrogen and other fast-burning fuels.
  • the benefits from the lean combustion approach are theoretically explained as follows.
  • the excess air improves the engine's thermal efficiency by increasing the overall specific heat's ratio, by decreasing the energy losses from dissociation of the combustion products, and by reducing the thermal losses to the engine's cooling system.
  • the NOx production is exponentially reduced and the excess air may promote a more complete reaction of CO and hydrocarbon fuel emission from crevices and quench layers.
  • the object of the invention is to configure and arrange a fuel system for a Otto gas engine in such a manner that an efficient supply of hydrogen is achieved.
  • said hydrogen source is a thermal reformer converting water into hydrogen according to at least one of the following reactions:
  • the reformer is supplied with water and with heat from at least a part of the exhaust gas stream and in that there are additional heating means, said heating means being powered by a part of the gas the engine is powered with in order to achieve the following exothermic oxidation reaction: R3 : CH4 + 02 «-» 2H 2 0 + C0 2 , or
  • R3' C n H m + (n /2)02 «-» (m/2) H2 + n C0, whereby the heating means are thermodynamically coupled to the reformer and are additionally heating the reformer and/or
  • said hydrogen source being a converter that converts higher HCs to hydrogen, said HCs consisting of n carbon atoms and m hydrogen atoms according to at least one of the following reactions:
  • the hydrogen produced is injected into the prechamber and thus mixed at least in part to the gas mixture in the combustion chamber.
  • the hydrogen increases the rate of combustion and thus the efficiency of the engine.
  • the very lean gas-air mixture in the combustion chamber having a value lambda ⁇ of at least 1.6 or between 1.6 and 2.6 leads to a combustion with a lower NOx (nitrogen oxide) portion.
  • the increased rate of combustion allows a later point of ignition, which leads to a higher degree of efficiency.
  • Further efficiency asset results in part from the methane for the oxidation reaction R3, R3' , because there is energy recharged with hydrogen, produced by using exhaust gas energy.
  • the efficiency of the H2 production by a chemical reaction is not subject to restrictions like a thermo dynamic cyclic process. Therefore, the thermal exhaust energy used in this chemical process is reformed with a much better degree of efficiency, which leads to a better degree of efficiency overall .
  • a motor for example, an electric motor.
  • the exhaust gas turbine of the turbo charger could be replaced and the air compressor could be driven by electricity or fluids. This allows the exhaust gas to keep more of its thermal energy, i. e. higher exhaust gas temperatures of about 550 °C to 600 °C, which are 100 °C to 150 °C higher than in case of an exhaust gas turbine. These temperatures are used for the reactions Rl and R2. In this case, the degree of efficiency raises up to about 53 %.
  • At least one compressor for loading the combustion chamber with an air-gas- mixture is driven via a motor, for example electrically.
  • the connected exhaust gas turbine can be eliminated. Therefore, the exhaust gas has a temperature that is 100°C to 150°C higher when it enters the reformer. This higher temperature serves an improved operation of the reformer or the respective reactor in such that the heating means can generate less heating output.
  • the engine has an exhaust gas turbine and at least one further generator for generating power, said further generator is being driven mechanically via the exhaust gas turbine, said exhaust gas turbine being positioned downstream to the source.
  • the energy available from the exhaust gas can be gained in this stage and used to generate energy for heating or powering processes.
  • Figure 1 shows a schematic diagram of a supply chain of an engine generator unit with a H2 reformer
  • Figure 2 shows a schematic diagram similar to figure 1 with an electrically driven compressor
  • Figure 3 shows a schematic diagram of a supply chain of an engine generator unit with a gas converter
  • Figure 4 shows a schematic diagram of the cylinder head
  • the schematic diagram in Figure 1 shows the supply chain of a spark-ignited gas engine 1 with an air-gas mixture.
  • a fuel duct 12 is conducted via a compressor 8 and a fuel cooler 12.2 to the gas engine 1 or to a combustion chamber 1.1 of the gas engine 1.
  • a throttle valve 14 that is controlled based on the output of the gas engine 1 is provided in this fuel duct 12 immediately upstream of the gas engine 1.
  • the gas engine 1 is connected to a generator 26, for example as part of a genset.
  • the gas engine 1 comprises an exhaust gas duct 6 in which an exhaust gas turbine 15 is provided downstream to the gas engine 1 that is used to drive the above-mentioned compressor 8. After passing through the exhaust gas turbine 15, the exhaust gas is conducted through a reformer 5 where it dissipates heat to the reformer 5 or a first reactor 5.1 or a second reactor 5.2, respectively.
  • the exhaust gas passes the reformer 5, in parallel, via two separate exhaust gas streams that are coupled or controlled, respectively, via a valve 16 for exhaust gas, and associated with the respec ⁇ tive reactor 5.1, 5.2.
  • the valve 16 for exhaust gas is followed by a heat exchanger or superheater 17, respectively, and a downstream evaporator 18 for a water circuit 19 described below.
  • An exhaust gas heat exchanger 20 is provided downstream before the exhaust gas is carried off to the exhaust system not shown here.
  • the water circuit or water duct 19 with the water port 19.1 is provided for supplying the reformer 5 with water for producing hydrogen.
  • the water carried in it is preheated by a heat exchanger 12.1 for water coupled to the fuel duct 12, wherein the heat is taken from the compressed exhaust gas-air mixture.
  • the water is heated in the evaporator 18 mentioned above, and the vapor is overheated accordingly in the downstream superheater 17 before it is returned to one of the two reactors 5.1, 5.2 of the reformer 5 via a respective valve 21 for water, i.e. steam.
  • the hydrogen that is produced during reformation is fed to a prechamber 2.1 of a spark plug 2 via a hydrogen duct 22 and a condenser 22.1.
  • a mixing section 9 in which ambient air or gas is admixed to the hydrogen via an air port 9.1 and a gas-port 9.2 to obtain a hydrogen-gas or a hydrogen-gas-air mixture may be provided.
  • the oxygen generated during hydrogen generation is carried off into the environment via a waste gate 5.3.
  • the respective reactor 5.1, 5.2 additionally comprises heating means 7.1, 7.2 that are also supplied with the air- gas mixture fed to the gas engine 1.
  • the fuel duct 12 comprises an fuel valve 12.3 via which the required air-gas mixture is supplied via a fuel duct 13 and a fuel valve 13.1 to the respective reactor 5.1, 5.2 or the respective heating means 7.1, 7.2.
  • the Co2 exhaust gas that is produced when operating the respective heating means 7.1, 7.2 is carried off via the waste gate 5.3.
  • the gas engine 1 comprises a cooling circuit 24 with a cooling water heat exchanger 24.1 for cooling the gas engine 1.
  • the cooling circuit 24 is also connected to an oil cooling exchanger 25.
  • the compressor 8 is driven by an electric motor 10.
  • the connected exhaust gas turbine 15 as shown in Figure 1 is eliminated.
  • the exhaust gas when it enters the reformer 5, has a temperature that is 100°C to 150°C higher. This higher temperature serves improved operation of the reformer 5 or the respective reactor 5.1, 5.2 in such that the heating means 7.1, 7.2 have to generate less heating output .
  • the schematic diagram in Figure 3 shows the supply chain of a spark-ignited gas engine 1 with a gas converter.
  • the fuel duct 12 is conducted via the compressor 8 and the fuel cooler 12.2 to the spark-ignited gas engine 1 or to a combustion chamber 1.1 of the spark-ignited gas engine 1.
  • the throttle valve 14 that is controlled based on the output of the spark-ignited gas engine 1 is provided in this fuel duct 12 immediately upstream of the spark-ignited gas engine 1.
  • the compressor 8 is driven by an electric motor 10. Therefore, there is no need for a connected exhaust gas turbine.
  • the exhaust gas when it enters a reformer 3 described below, has a temperature that is 100°C to 150°C higher as in case of an exhaust gas turbine. This higher temperature contributes to the enhanced operation of the reformer 3.
  • the spark-ignited gas engine 1 comprises the exhaust gas duct 6, in which the reformer 3 for gas is provided downstream to the spark-ignited gas engine 1.
  • the heat of the exhaust gas is in part dissipated to the reformer 3 via a heat exchanger not shown here.
  • the exhaust gas turbine 15 Downstream to the reformer 3, the exhaust gas turbine 15 is provided with a generator 15.1 coupled to it. Further ex- pansion of the exhaust gas generates electricity that can also be used for the motor 10.
  • the exhaust gas turbine 15 is followed by the heat exchanger or superheater 19 and the evaporator 18 for a water circuit 19 described below.
  • the exhaust gas heat exchanger 20 is provided downstream before the exhaust gas is carried off to the exhaust system not shown here.
  • the water circuit or water duct 19 with the water port 19.1 is provided for supplying the reformer 3 with water vapor for producing reform gas.
  • the water carried in it is preheated by a water heat exchanger 12.1 coupled to the fuel duct 12, wherein the heat is taken from the compressed exhaust gas-air mixture.
  • the water is heated in the evaporator 18 mentioned above, and the vapor is overheated accordingly in the downstream superheater 19 before it is discharged into the reformer 3.
  • a gas-steam mixing point 13.2 for adding combustion gas to the water vapor is provided between the evaporator 18 and the superheater 19.
  • the mixing point 13.2 is connected to the gas duct 13 via a gas valve 13.1 for gas.
  • the reform gas that is produced during reformation can be fed to the mixer 11, and thus to the air-gas mixture, for combustion in the spark-ignited gas engine 1 via a reform gas duct 22 and a condenser 22.1.
  • the reform gas can be led via the injector 4 to the prechamber 2.1 of the spark plug 2 as described below.
  • the gas engine 1 comprises a cylinder head 1.2 with a spark plug 2 having a pre-chamber 2.1.
  • the prechamber spark plug 2 or the prechamber 2.1 respectively, is supplied with hydrogen or a mixture of hydrogen and gas and/or air via the injector 4.
  • a highly explosive gas mixture is produced there in such that even a very lean gas- air mixture in the combustion chamber 1.1 with a value lambda ⁇ of at least 1.6 or between 1.6 and 2.6 is ignita- ble, which leads to a combustion having a lower NOx (nitrogen oxide) portion and an increased rate of combustion.
  • the increased rate of combustion allows a delayed ignition point, which leads to a higher degree of efficiency.
  • spark plug prechamber spark plug prechamber
  • mixing section for gas and/or air air port

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion Methods Of Internal-Combustion Engines (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)

Abstract

The present invention relates to a spark-ignited gas engine 1 having an exhaust gas duct 6 and a cylinder head 1.2, said cylinder head 1.2 having at least one spark plug 2 with a prechamber 2.1 and an injector 2.2, said injector 4 being connected to the prechamber 2.1 for flushing the prechamber 2.1 with hydrogen, and having a thermal reformer 5 for generating hydrogen, whereas said reformer 5 is supplied with water and converts water into hydrogen according to the following reactions: R1: MOred + H20 «-» MOOX + H2 or R2: MOOX «-» MOred + 02, and the reformer 5 is connected to at least a part of the exhaust gas duct 6 for supplying the reformer 5 with heat and there are additional heating means 7.1, 7.2, said heating means 7.1, 7.2 being powered by a part of the gas the engine 1 is powered with in order to achieve the following exothermic oxidation reaction: R3: CH4 + 02 «-» 2H20 + C02, or R3' : CnHm + (n/2)02 «-» (m/2)H2 + nCO, whereby the heating means 7.1, 7.2 are thermodynamically coupled to the reformer 5 for additionally heating the reformer 5.

Description

Hydrogen flushed combustion chamber
The present invention relates to a procedure for running a spark-ignited gas engine with a combustion chamber generating an exhaust gas stream with at least one prechamber spark plug, and with a hydrogen source, said source supplying a prechamber of said spark plug with hydrogen, and an injector, said injector being connected to the prechamber for flushing the prechamber with hydrogen, whereby the combustion chamber is loaded with a gas air mixture having a value lambda λ of at least 1.6.
EP 0 770 171 Bl discloses ignition devices for internal combustion engines, and more particularly hydrogen assisted jet ignition (HAJI) devices for improving combustion efficiency. In the present specification the term "hydrogen" is intended to include hydrogen and other fast-burning fuels. The benefits from the lean combustion approach are theoretically explained as follows. The excess air improves the engine's thermal efficiency by increasing the overall specific heat's ratio, by decreasing the energy losses from dissociation of the combustion products, and by reducing the thermal losses to the engine's cooling system. In addition, as the flame temperature drops with decreasing fuel air ratio, the NOx production is exponentially reduced and the excess air may promote a more complete reaction of CO and hydrocarbon fuel emission from crevices and quench layers. It further discloses that the effect of changing the main chamber fuel composition for the range of 1 = 1 to 3.5 at full throttle (full power) and smaller ranges at part throttle was studied and that even at full throttle it was possible to reduce the work per cycle wc (and the torque) to no load quantities by increasing the relative air/fuel ratio; whereas the lean limit for this engine with normal ignition is shown to occur at 1 = 1.64, there exists no lean limit with hydrogen assisted jet ignition, HAJI, within the usable range of wc.
The object of the invention is to configure and arrange a fuel system for a Otto gas engine in such a manner that an efficient supply of hydrogen is achieved.
According to the invention, the aforesaid object is achieved in that
a) said hydrogen source is a thermal reformer converting water into hydrogen according to at least one of the following reactions:
Rl: Ored + H20 «-» M0OX + H2,
R2: M0OX «-» MOred + 02,
and in that the reformer is supplied with water and with heat from at least a part of the exhaust gas stream and in that there are additional heating means, said heating means being powered by a part of the gas the engine is powered with in order to achieve the following exothermic oxidation reaction: R3 : CH4 + 02 «-» 2H20 + C02, or
R3': CnHm + (n/2)02 «-» (m/2)H2 + nC0, whereby the heating means are thermodynamically coupled to the reformer and are additionally heating the reformer and/or
b) said hydrogen source being a converter that converts higher HCs to hydrogen, said HCs consisting of n carbon atoms and m hydrogen atoms according to at least one of the following reactions:
- CnHm + nH20 «-» (m/2 +n)H2 + nC0,
- CnHm + (n/2)02 «-» (m/2)H2 + nCO,
- CnHra + nC02 «-» (m 2,H2 + 2nC0, whereby the reformer is supplied with water, gas and with heat from at least a part of the exhaust gas stream.
The hydrogen produced is injected into the prechamber and thus mixed at least in part to the gas mixture in the combustion chamber. The hydrogen increases the rate of combustion and thus the efficiency of the engine. Additionally to this, the very lean gas-air mixture in the combustion chamber having a value lambda λ of at least 1.6 or between 1.6 and 2.6 leads to a combustion with a lower NOx (nitrogen oxide) portion. The increased rate of combustion allows a later point of ignition, which leads to a higher degree of efficiency. Further efficiency asset results in part from the methane for the oxidation reaction R3, R3' , because there is energy recharged with hydrogen, produced by using exhaust gas energy.
The efficiency of the H2 production by a chemical reaction is not subject to restrictions like a thermo dynamic cyclic process. Therefore, the thermal exhaust energy used in this chemical process is reformed with a much better degree of efficiency, which leads to a better degree of efficiency overall .
Moreover, recharging this produced hydrogen leads to a reduction of nitrogen oxide (NOx) and formaldehyde, i. e. methanal (CH20) emissions, because the added hydrogen has a catalytic effect on the combustion. For this, the efficiency of the engine is increased, too.
It can also be an advantage to drive at least one compressor for loading a combustion chamber with an air-gas- mixture via a motor, for example, an electric motor. In addition to the energy of reaction R3, R3' , the exhaust gas turbine of the turbo charger could be replaced and the air compressor could be driven by electricity or fluids. This allows the exhaust gas to keep more of its thermal energy, i. e. higher exhaust gas temperatures of about 550 °C to 600 °C, which are 100 °C to 150 °C higher than in case of an exhaust gas turbine. These temperatures are used for the reactions Rl and R2. In this case, the degree of efficiency raises up to about 53 %.
Further, it could be advantageous to supply said prechamber with a mixture of gas and hydrogen. In this case, the additional injection of hydrogen brings both advantages, namely less carbon particulate matter in the exhaust gas and a higher rate of combustion. This is because the ignition is more powerful by using additional hydrogen. Furthermore, the rebuilding of tar within the prechamber is reduced.
Another increase in the rate of combustion is achieved with supplying the prechamber with a mixture of hydrogen and air or with a mixture of hydrogen and gas and air, said mixture having a ratio λ of air a and hydrogen h as follows: 1 <= A=a/h or 1.2 <= A=a/h <= 1.5.
Additionally, it can be advantageous if at least one compressor for loading the combustion chamber with an air-gas- mixture is driven via a motor, for example electrically. For this, the connected exhaust gas turbine can be eliminated. Therefore, the exhaust gas has a temperature that is 100°C to 150°C higher when it enters the reformer. This higher temperature serves an improved operation of the reformer or the respective reactor in such that the heating means can generate less heating output.
It can be advantageous if the engine has an exhaust gas turbine and at least one further generator for generating power, said further generator is being driven mechanically via the exhaust gas turbine, said exhaust gas turbine being positioned downstream to the source. The energy available from the exhaust gas can be gained in this stage and used to generate energy for heating or powering processes.
Additionally, it can be advantageous if only higher HCs, which have at least two or three carbon atoms, are converted in the converter. For optimization the methane number of the gas available, it is more efficient to convert higher HCs first, i.e. methane itself must not be converted and therefore be joked with hydrogen.
Other advantages and details of the invention are explained in the claims and in the description as well as shown in the figures, in which:
Figure 1 shows a schematic diagram of a supply chain of an engine generator unit with a H2 reformer;
Figure 2 shows a schematic diagram similar to figure 1 with an electrically driven compressor;
Figure 3 shows a schematic diagram of a supply chain of an engine generator unit with a gas converter;
Figure 4 shows a schematic diagram of the cylinder head
with combustion chamber.
The schematic diagram in Figure 1 shows the supply chain of a spark-ignited gas engine 1 with an air-gas mixture.
Starting from a gas mixer 11 at which the ambient air is mixed with the combustion gas via an air port 11.1, a fuel duct 12 is conducted via a compressor 8 and a fuel cooler 12.2 to the gas engine 1 or to a combustion chamber 1.1 of the gas engine 1. A throttle valve 14 that is controlled based on the output of the gas engine 1 is provided in this fuel duct 12 immediately upstream of the gas engine 1. The gas engine 1 is connected to a generator 26, for example as part of a genset.
The gas engine 1 comprises an exhaust gas duct 6 in which an exhaust gas turbine 15 is provided downstream to the gas engine 1 that is used to drive the above-mentioned compressor 8. After passing through the exhaust gas turbine 15, the exhaust gas is conducted through a reformer 5 where it dissipates heat to the reformer 5 or a first reactor 5.1 or a second reactor 5.2, respectively. The exhaust gas passes the reformer 5, in parallel, via two separate exhaust gas streams that are coupled or controlled, respectively, via a valve 16 for exhaust gas, and associated with the respec¬ tive reactor 5.1, 5.2. The valve 16 for exhaust gas is followed by a heat exchanger or superheater 17, respectively, and a downstream evaporator 18 for a water circuit 19 described below. An exhaust gas heat exchanger 20 is provided downstream before the exhaust gas is carried off to the exhaust system not shown here.
The water circuit or water duct 19 with the water port 19.1 is provided for supplying the reformer 5 with water for producing hydrogen. First, the water carried in it is preheated by a heat exchanger 12.1 for water coupled to the fuel duct 12, wherein the heat is taken from the compressed exhaust gas-air mixture. Then the water is heated in the evaporator 18 mentioned above, and the vapor is overheated accordingly in the downstream superheater 17 before it is returned to one of the two reactors 5.1, 5.2 of the reformer 5 via a respective valve 21 for water, i.e. steam. The hydrogen that is produced during reformation is fed to a prechamber 2.1 of a spark plug 2 via a hydrogen duct 22 and a condenser 22.1. In addition, a mixing section 9 in which ambient air or gas is admixed to the hydrogen via an air port 9.1 and a gas-port 9.2 to obtain a hydrogen-gas or a hydrogen-gas-air mixture may be provided. The oxygen generated during hydrogen generation is carried off into the environment via a waste gate 5.3.
In order to achieve the temperatures required in the respective reactor 5.1, 5.2 or in the reformer 5, respectively, the respective reactor 5.1, 5.2 additionally comprises heating means 7.1, 7.2 that are also supplied with the air- gas mixture fed to the gas engine 1. For this purpose, the fuel duct 12 comprises an fuel valve 12.3 via which the required air-gas mixture is supplied via a fuel duct 13 and a fuel valve 13.1 to the respective reactor 5.1, 5.2 or the respective heating means 7.1, 7.2. The Co2 exhaust gas that is produced when operating the respective heating means 7.1, 7.2 is carried off via the waste gate 5.3.
In addition, the gas engine 1 comprises a cooling circuit 24 with a cooling water heat exchanger 24.1 for cooling the gas engine 1. The cooling circuit 24 is also connected to an oil cooling exchanger 25.
According to the functional diagram shown in Figure 2, the compressor 8 is driven by an electric motor 10. The connected exhaust gas turbine 15 as shown in Figure 1 is eliminated. For this, the exhaust gas, when it enters the reformer 5, has a temperature that is 100°C to 150°C higher. This higher temperature serves improved operation of the reformer 5 or the respective reactor 5.1, 5.2 in such that the heating means 7.1, 7.2 have to generate less heating output . Alternatively, there is an exhaust gas turbine 15 positioned downstream to the reformer 5 with a connected generator 15.1 for generating power. This power can be used for further heating means connected to the reformer 5 or the superheater 17 or the evaporator 18, for example.
The schematic diagram in Figure 3 shows the supply chain of a spark-ignited gas engine 1 with a gas converter.
Starting from the gas mixer 11, at which the ambient air is added via the air port 11.1 and mixed with the combustion gas provided via a gas duct 13, the fuel duct 12 is conducted via the compressor 8 and the fuel cooler 12.2 to the spark-ignited gas engine 1 or to a combustion chamber 1.1 of the spark-ignited gas engine 1. The throttle valve 14 that is controlled based on the output of the spark-ignited gas engine 1 is provided in this fuel duct 12 immediately upstream of the spark-ignited gas engine 1.
The compressor 8 is driven by an electric motor 10. Therefore, there is no need for a connected exhaust gas turbine. The exhaust gas, when it enters a reformer 3 described below, has a temperature that is 100°C to 150°C higher as in case of an exhaust gas turbine. This higher temperature contributes to the enhanced operation of the reformer 3.
The spark-ignited gas engine 1 comprises the exhaust gas duct 6, in which the reformer 3 for gas is provided downstream to the spark-ignited gas engine 1. The heat of the exhaust gas is in part dissipated to the reformer 3 via a heat exchanger not shown here.
Downstream to the reformer 3, the exhaust gas turbine 15 is provided with a generator 15.1 coupled to it. Further ex- pansion of the exhaust gas generates electricity that can also be used for the motor 10.
The exhaust gas turbine 15 is followed by the heat exchanger or superheater 19 and the evaporator 18 for a water circuit 19 described below. The exhaust gas heat exchanger 20 is provided downstream before the exhaust gas is carried off to the exhaust system not shown here.
The water circuit or water duct 19 with the water port 19.1 is provided for supplying the reformer 3 with water vapor for producing reform gas. First, the water carried in it is preheated by a water heat exchanger 12.1 coupled to the fuel duct 12, wherein the heat is taken from the compressed exhaust gas-air mixture. Then the water is heated in the evaporator 18 mentioned above, and the vapor is overheated accordingly in the downstream superheater 19 before it is discharged into the reformer 3.
A gas-steam mixing point 13.2 for adding combustion gas to the water vapor is provided between the evaporator 18 and the superheater 19. The mixing point 13.2 is connected to the gas duct 13 via a gas valve 13.1 for gas.
The reform gas that is produced during reformation can be fed to the mixer 11, and thus to the air-gas mixture, for combustion in the spark-ignited gas engine 1 via a reform gas duct 22 and a condenser 22.1.
Alternatively or additionally to this, the reform gas can be led via the injector 4 to the prechamber 2.1 of the spark plug 2 as described below. There is the mixing section 9 within the reform gas duct 22 with the air port 9.1 and the gas port 9.2, which allows mixing gas and/or air to the reform gas before it is injected into the prechamber 2.1.
According to Figure 4, the gas engine 1 comprises a cylinder head 1.2 with a spark plug 2 having a pre-chamber 2.1. The prechamber spark plug 2 or the prechamber 2.1, respectively, is supplied with hydrogen or a mixture of hydrogen and gas and/or air via the injector 4. By flushing the prechamber 2.1 with this fuel, a highly explosive gas mixture is produced there in such that even a very lean gas- air mixture in the combustion chamber 1.1 with a value lambda λ of at least 1.6 or between 1.6 and 2.6 is ignita- ble, which leads to a combustion having a lower NOx (nitrogen oxide) portion and an increased rate of combustion. The increased rate of combustion allows a delayed ignition point, which leads to a higher degree of efficiency.
Reference list
gas engine
combustion chamber
cylinder head
spark plug, prechamber spark plug prechamber
hydrogen source, converter
inj ector
hydrogen source, thermal reformer reactor
reactor
waste gate of reformer
exhaust gas duct, exhaust gas stream heating means
heating means
compressor
mixing section for gas and/or air air port
gas port
electric motor, motor
gas mixer
air port
fuel duct
heat exchanger
fuel cooler
fuel valve
fuel duct
fuel valve
mixing point
throttle valve
exhaust gas turbine further generator
valve for exhaust gas superheater
evaporator
water circuit, water duct water port
exhaust gas heat exchanger valve for water
hydrogen duct
condenser
cooling system / circuit cooling water heat exchanger oil cooling exchanger generator ratio airactual/ c*lrstoichiometric

Claims

Claims
1. Procedure for running a spark-ignited gas engine (1) with a combustion chamber (1.1) generating an exhaust gas stream (6) with at least one prechamber spark plug (2), and with a hydrogen source (3, 5), said source (3, 5) supplying a prechamber (2.1) of said spark plug (2) with hydrogen, and an injector (4), said injector (4) being connected to the prechamber (2.1) for flushing the prechamber (2.1) with hydrogen, whereby the combustion chamber (1.1) is loaded with a gas air mixture having a value lambda λ between 1.6 and 2.6, characterized in that
a) said hydrogen source (5) is a thermal reformer converting water into hydrogen according to at least one of the following reactions:
Rl: MOred + H20 «-» M0OX + H2,
R2: M0OX «-» MOred + 02,
and in that the reformer (5) is supplied with water and with heat from at least a part of the exhaust gas stream (6), and in that there are additional heating means (7.1, 7.2), said heating means (7.1, 7.2) being powered by a part of the gas the engine (1) is powered with in order to achieve the following exothermic oxidation reaction:
R3: CH4 + 02 «-» 2H20 + C02, or
R3' : CnHm + (n/2)02 «-» (m/2)H2 + nC0, whereby the heating means (7.1, 7.2) are thermody- namically coupled to the reformer (5) and are additionally heating the reformer (5) and/or b) said hydrogen source (3) is a converter that converts higher HCs to hydrogen, said HCs consisting of n carbon atoms and m hydrogen atoms according to at least one of the following reactions:
- CnHm + nH20 «-» (m/2 +n)H2 + nCO,
- CnHm + (n/2)02 «-» (m/2)H2 + nCO,
- CnHm + nC02 «-» (m/2)H2 + 2nCO,
whereby the reformer (3) is supplied with water, gas and with heat from at least a part of the exhaust gas stream ( 6 ) .
Procedure according to claim 1, in which said
prechamber (2.1) is supplied with a mixture of gas and hydrogen .
Procedure according to claim 1, in which said
prechamber (2.1) is supplied with a mixture of hydrogen and air or with a mixture of hydrogen, gas and air, said mixture having a ratio λ of air a and hydrogen h as follows: 1 <= A=a/h or
0,1 <= A=a/h <= 1.
Procedure according to claim 1, in which at least one compressor (8) for loading the combustion chamber (1.1) with an air-gas-mixture is driven via a motor (10).
Procedure according to claim 5, in which the compressor (8) is driven electrically.
Procedure according to claim 1, in which the engine (1) has an exhaust gas turbine (15) and at least one generator (15.1) for generating power, said generator (15.1) being driven mechanically via the exhaust gas turbine (15), said exhaust gas turbine (15) being positioned downstream to the reformer (3, 5).
7. Procedure according to claim 1, in which only higher HCs having at least two or three carbon atoms are converted in the converter (3) .
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