Classifications

• • 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
  • 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
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
  • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
  • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
  • F01N3/2033—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using a fuel burner or introducing fuel into exhaust duct
• • 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
  • F02D19/08—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 simultaneously using pluralities of fuels
  • F02D19/081—Adjusting the fuel composition or mixing ratio; Transitioning from one fuel to the other
• • 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
  • F01N2610/00—Adding substances to exhaust gases
  • F01N2610/04—Adding substances to exhaust gases the substance being hydrogen
• • 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
  • F01N2610/00—Adding substances to exhaust gases
  • F01N2610/08—Adding substances to exhaust gases with prior mixing of the substances with a gas, e.g. air
• • 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

• TITLE Device and method for reduction of harmful emissions from a combustion engine are provided.
• the present invention relates to an arrangement for reducing harmful emissions from an internal combustion engine according to the pre-characterizing clause of Patent Claim 1 below.
• the invention is intended in particular for use in connection with engines adapted for supplying hydrogen gas to the inlet side and/or exhaust gas side of the engine.
• the invention also relates to a procedure for such reduction in harmful emissions according to the pre-characterizing clause of Patent Claim 14 below.
• the light-off temperature can be defined as the temperature at which the catalyst provides a 50?> conversion rate.
• Modern catalysts operate with light-off temperatures of around 200°C to 300°C.
• Another way of shortening the time that passes before the three-way catalyst reaches its light-off temperature is to use a separate, smaller primary catalyst, which is positioned upstream of the ordinary three-way catalyst.
• a separate, smaller primary catalyst With suitable positioning and design of the primary catalyst, an increased temperature of the exhaust gases that flow through the three-way catalyst positioned downstream is obtained (on account of the exothermic reaction) .
• the primary catalyst contributes to reduced emissions from the catalyst system as a whole.
• a disadvantage of this method is that the primary catalyst positioned upstream may have a negative influence on the external gas exchange of the engine.
• such a primary catalyst is normally arranged relatively close to the engine, which may lead to problems relating to ageing as a result of the high temperatures that normally prevail in the vicinity of the engine .
• a further method of shortening the light-off time of the three-way catalyst is to delay the moment of ignition of the engine, which produces an increase in the exhaust gas temperature and a reduction in emissions.
• a disadvantage of this method is that it gives rise to relatively high fuel consumption.
• a further method of shortening the light-off time of the three-way catalyst is to have a combustible gas flow towards the three-way catalyst and be ignited with the aid of a separate ignition arrangement. In this way, effective and rapid heating-up of the catalyst is achieved.
• a disadvantage of this method is that it requires a separate ignition arrangement, which in turn creates problems relating to reliability and adds an extra cost in the manufacture of the vehicle.
• this method leads to a very high thermal load on the catalytic coating (thermal shock) , which may lead to a limited life of the catalyst.
• the three-way catalyst may also be brought to its light-off temperature rapidly by allowing a gas to be combusted spontaneously (that is to say without any separate ignition arrangement) in close association with the three-way catalyst.
• a gas to be combusted spontaneously that is to say without any separate ignition arrangement
• a system that applies this principle is disclosed in patent specification WO 96/11330.
• hydrogen gas is produced on board the vehicle with the aid of a separate electrolysis arrangement.
• the hydrogen gas is supplied to a point upstream of the three-way catalyst together with added air fed from a secondary air pump.
• a further problem that may arise in connection with exhaust gas cleaning with the aid of a catalyst is that, in the case of a certain type of gas composition, the presence of HC, CO and certain other substances leads to poisoning of the active surfaces of the catalyst. To a great extent, this poisoning controls the light-off temperature which, as mentioned above, is of the order of 200-300°C, which applies in the case of a normal hydrogen content in the exhaust gases (of the order of ⁇ 1%), while the light-off temperature is roughly 100-130°C in the case of an increased hydrogen content (at least roughly 4%) .
• the aim of the present invention is to provide an improved arrangement for reducing harmful emissions from an internal combustion engine, which brings about in an optimum manner a shortening of the time until a three-way catalyst reaches its light-off temperature.
• This aim is achieved by means of an arrangement, the characterizing features of which emerge from Patent Claim 1 below. Said aim is also achieved by means of a procedure, the characterizing features of which emerge from Patent Claim 14 below.
• the invention is intended for reducing harmful emissions from an internal combustion engine by rapid heating-up of an exhaust gas catalyst which is arranged in an exhaust system belonging to said engine.
• the invention comprises means of supplying hydrogen and means of supplying air to the exhaust system upstream of said catalyst, the mixture of hydrogen and air giving rise to spontaneous exothermic combustion in association with the catalyst.
• the invention also comprises a control unit for controlling the functioning of said means.
• the invention is characterized in that said control unit is adapted to control the supply of air and hydrogen to the exhaust system in connection with starting the engine for a period of time that lasts at least until the exhaust gas catalyst has reached a limit temperature at which its functioning is not hampered by CO or HC poisoning.
• a short heating-up time for the catalyst is achieved by accurate optimization of the invention.
• a further aim of the invention is to provide a stable starting cycle of an engine while the emissions of CO and HC impurities are essentially eliminated.
• this aim can be achieved by providing a hydrogen supply on the inlet side of the engine during the starting cycle, that is to say before any liquid fuel is supplied to the engine.
• liquid fuel means the normal fuel for the engine, which at present in most markets consists of petrol or alcohol/petrol mixtures.
• Figure 1 shows a basic diagram of an internal combustion engine arrangement, in which the present invention can be used, and Figure 2 shows an alternative embodiment of the invention.
• FIG. 1 shows diagrammatically an arrangement according to the present invention.
• the invention is arranged in association with an internal combustion engine 1 in the form of a conventional petrol engine.
• the engine 1 is fed in the usual manner with inflowing air via an air inlet 2.
• the engine 1 is also provided with a number of (for example four) cylinders 3 as well as a corresponding number of injection arrangements 4 for fuel.
• Each injection arrangement 4 is electrically connected to a central control unit 5.
• the quantity of air that is supplied to the engine 1 is regulated in a known manner with the aid of a gas throttle 6.
• the control unit 5 is preferably computer-based and is adapted to control in a known manner the fuel supply to each injector arrangement 4 with fuel from a fuel tank
• the engine 1 is of the multi-point injection type, in which the correct quantity of fuel for the engine 1 can in a known manner be supplied individually to each cylinder 3.
• the exhaust gases from the engine 1 are led out from the cylinders 3 via a branch pipe 7 and onward to an exhaust pipe 8 connected to the branch pipe 7.
• an exhaust gas catalyst 9 which consists of a conventional three-way catalyst for reducing NO ;: and HC impurities as well as CO, which takes place by means of known catalytic reactions .
• the control unit 5 is adapted to control the air/fuel mixture to the engine 1 so that it is constantly adapted to the current operating conditions.
• the system comprises at least one sensor for detecting the oxygen concentration in the exhaust gases.
• a sensor 10 is shown, which is preferably of the lambda-probe type and is connected to the control unit 5 via an electrical connection.
• the sensor 10 is preferably positioned in the exhaust pipe 8, upstream of the catalyst 9.
• Control of the engine 1 takes place in an essentially known manner depending on various parameters which reflect the operating conditions of the engine 1 and the vehicle concerned. For example, the engine control may take place depending on the acceleration applied, the engine speed, the quantity of air to the engine and the oxygen concentration in the exhaust gases.
• the engine 1 shown in the figure is of the four-cylinder type. It is to be noted, however, that the invention may be used in engines with different numbers of cylinders and different cylinder configurations. Moreover, the invention may in principle also be used in the case of single-point injection, where a single fuel-injection arrangement is positioned in the inlet pipe of the engine .
• the engine 1 can be provided with hydrogen gas from a hydrogen gas container 11.
• Supply of hydrogen to the inlet side of the engine takes place via a first hydrogen gas line 12 which opens into the air inlet 2 and is controlled with the aid of a first valve 13 which can preferably be controlled electrically and is for this purpose connected to the control unit 5.
• the exhaust gas side of the engine 1 can also be fed with hydrogen gas from the container 11. This takes place via a second hydrogen gas line 15 which opens into the exhaust pipe 8.
• the hydrogen supply to the exhaust gas side is controlled with the aid of a second valve 16 which can also preferably be controlled electrically and is therefore connected to the control unit 5.
• the hydrogen that is to be supplied to the air inlet 2 and/or the exhaust pipe 8 is preferably produced on the vehicle with the aid of a separate electrolysis arrangement 17 which is connected to the hydrogen gas container 11 via a further line 18.
• a container 19 for water is also connected to the electrolysis arrangement 17 via a further line 20.
• the electrolysis arrangement 17 is preferably activated, which means that hydrogen will be produced and stored under pressure in the container 11.
• the control unit 5 is also adapted so as, under certain predetermined operating conditions of the engine 1 (preferably when the engine is cold and the catalyst therefore needs to be heated to its light-off temperature as rapidly as possible) , to open the valve 16 and feed hydrogen to a point upstream of the catalyst 9.
• the invention is also adapted so as to supply air to the exhaust system 8 for mixing with said hydrogen so that a combustible gas mixture is formed.
• the control unit 5 is adapted to control the functioning of the engine 1 so that a given quantity of surplus oxygen is produced in the exhaust gas mixture that flows through the catalyst 9.
• One way of achieving this air supply is to operate the engine 1 using essentially only hydrogen, which then preferably takes place for a given period of time in connection with starting the engine 1.
• the hydrogen supply allows the combustion to be controlled towards lean operation, a lean fuel/air mixture being combusted so that an oxygen surplus arises on the exhaust gas side, more specifically an exhaust gas mixture with an oxygen content of 4% or more.
• Another way of bringing about a supply of air to the exhaust system is to use a separate secondary air pump 21 which is then adapted to feed air to a point along the hydrogen line 15 via an air line 22.
• the air pump 21 is electrically connected to the control unit 5.
• the control unit 5 is adapted so as to activate the air pump 21 under certain operating conditions.
• the air line 22 is adapted to open into the hydrogen gas line 15 at a point which preferably lies immediately downstream of the valve 16. In this way, an initial intermixing of air and hydrogen can take place before the gas mixture reaches the exhaust pipe 8, which results in a homogeneous gas mixture .
• the air that is supplied to the exhaust system (either by hydrogen-assisted lean operation of the engine or with the aid of the air pump 21) will be mixed with the hydrogen that has been supplied via the line 15. This in turn gives rise to spontaneous exothermic combustion in association with the catalyst 9. This leads to heating-up which in turn results in the catalyst 9 being heated up rapidly to its light-off temperature.
• the arrangement according to the invention is preferably adapted so that hydrogen gas can be fed to the inlet side of the engine 1. More specifically, such hydrogen supply can take place during the first seconds after starting the engine 1. In this stage, therefore, preferably only hydrogen is supplied, that is to say without any simultaneous supply of liquid fuel (which usually consists of petrol or a suitable alcohol/petrol mixture) .
• liquid fuel which usually consists of petrol or a suitable alcohol/petrol mixture
• a number of advantages are obtained. Firstly, it may be pointed out that emissions of CO, CO and HC impurities from the engine 1 can be virtually eliminated during this stage.
• a very stable starting cycle of the engine is also brought about, not least during cold starts.
• lambda regulation is simple because the quantity of oxygen supplied does not need to be regulated with particularly great accuracy.
• control unit 5 is preferably adapted in such a manner that liquid fuel is supplied gradually while the supply of hydrogen is gradually throttled. This phasing-in of the liquid fuel is activated at a given moment after starting the engine 1.
• the invention can be used during a "pre-crank" cycle, that is to say according to a cycle that is initiated before the engine 1 has been started.
• This pre-crank cycle can preferably be initiated with the aid of a separate proximity sensor, for example in the form of a circuit breaker 23 which senses the presence of the driver in the vehicle in which the invention is used and which for this purpose can be arranged in a door (not shown) in the vehicle.
• This circuit breaker 23 is then electrically connected to the control unit 5.
• a signal will be issued from the circuit breaker 23 to the control unit 5.
• the air pump 21 is also activated by the control unit 5 to feed air.
• the control unit 5 also sets the valve 16 in an open position, hydrogen and air are mixed in the downstream part of the hydrogen line 15.
• This gas mixture is combusted and heat is generated.
• the supply of hydrogen gas to the exhaust gas side is preferably controlled in such a manner that it amounts to 0-28% of the total quantity of gas (as a percentage by volume) , preferably 3-18%. It has emerged that such a proportion of hydrogen in the gas mixture in the exhaust pipe 8 leads to substantial heating-up of the upstream end section of the catalyst 9, which makes possible rapid heating-up of the catalyst 9.
• proximity sensor can be used in order to detect the presence of the driver of the vehicle and for initiating the pre-crank cycle when presence is detected.
• a capacitive proximity sensor may be used, which is a type of sensor in which conductive elements are arranged in association with the driver's seat and are adapted so that they form a given capacitance, the value of which can be detected by a separate measuring unit. In this way, given predetermined values of said capacitance may correspond to presence or non-presence respectively in the seat.
• the pre-crank cycle according to the above can then be activated.
• the air and hydrogen mixture is fed to the exhaust pipe 8 for a given period of time t that lasts at least until said limit temperature T has been reached.
• the engine 1 can then be started in the conventional manner.
• carbon monoxide is fed through the catalyst 9 (on account of incomplete combustion of the hydrocarbons contained in the engine fuel) , but this carbon monoxide does not give rise to any CO poisoning because the catalyst 9 has been heated to the limit temperature T .
• the catalyst 9 therefore continues to be heated by the hydrogen/air mixture supplied in the hydrogen-rich environment until it reaches its normal light-off temperature T L which is usually of the order of 200- 300°C.
• T L normal light-off temperature
• the engine system can then be controlled with a normal exhaust gas environment, that is to say without hydrogen being supplied.
• the period of time for which the pre-crank cycle is active (which is normally the period of time that passes before the engine 1 is started) can be defined by predetermined factors, for example the anticipated time required before said limit temperature T G has been reached.
• the control unit 5 is adapted to activate the pre-crank cycle during this predetermined period of time.
• this period of time may depend on, for example, the temperature of the catalyst 9 or the external temperature.
• such a temperature value can be detected by a temperature sensor (not shown) , and the control unit 5 can be adapted to interrupt the pre-crank cycle and start the engine 1 when a predetermined limit value has been reached.
• HC poisoning can also occur in diesel engines.
• the invention can therefore be used for supplying air and hydrogen to an exhaust system in connection with starting an engine, which takes place for a period of time that lasts at least until the catalyst has reached a limit temperature at which its functioning is not hampered by either CO poisoning or HC poisoning.
• a further way of reaching the light-off temperature of the catalyst rapidly is to use a "post-crank" cycle, that is to say a cycle that is initiated essentially at the same time as the engine is started and continues for a given time after the engine 1 has been started.
• the necessary air supply on the exhaust gas side can be achieved with the aid of the abovementioned air pump 21 or - according to an alternative embodiment - by operating the engine with essentially only hydrogen gas for a given time.
• the control unit 5 is then adapted to control the supply of hydrogen gas to the engine so that an oxygen surplus is created in the exhaust gases of the engine.
• the engine is preferably controlled with a hydrogen gas supply on the inlet side so that an oxygen surplus of roughly 4% is produced in the exhaust gases.
• the hydrogen that is supplied to the exhaust system will react catalytically with the oxygen in the exhaust gas even at low temperatures if CO or HC is not present in the exhaust gas.
• the engine must therefore be operated with only hydrogen and air for a period of time until the catalyst has reached the limit temperature T G .
• the quantity of hydrogen gas supplied on the exhaust gas side is then controlled so that at least stoichiometry in relation to the quantity of oxygen is achieved, that is to say so that the ratio of hydrogen gas to oxygen is at least 2:1. This leads to a reduction in NO. : impurities at temperatures above the limit value T .
• the air pump 21 can be operated parallel with the hydrogen gas supply to produce the oxygen surplus .
• the control unit 5 can then be adapted so that a given quantity of hydrogen is fed to the inlet 2 of the engine, the control unit 5 controlling the air pump 21 so that it delivers any surplus that may be required in order for the desired hydrogen/air mixture to be obtained in the exhaust pipe 8.
• control unit 5 is preferably adapted so that the liquid fuel is supplied gradually while the supply of hydrogen is gradually throttled.
• a small quantity of liquid fuel can be supplied via the ordinary fuel injection of the system of the engine parallel with the hydrogen supply.
• the engine is started on hydrogen- enriched fuel and not pure hydrogen gas, the risk of undesirable self-ignition and flame propagation on the inlet side of the engine being reduced in a known manner.
• the quantity of energy that is delivered to the engine in the form of liquid fuel and hydrogen gas respectively can then be varied during the starting cycle and is suitably controlled by the control unit 5.
• the invention is designed with means of minimizing heat losses, which are in turn adapted to limit any flame formation in the catalyst 9.
• this can be brought about by a special flame extinguisher (not shown) which, in a known manner, consists of a tube-like element with a number of duct-like or tube-like elements running through, through which the exhaust gases from the engine flow.
• the flame extinguisher is positioned in the upstream end portion of the catalyst 9.
• the flame extinguisher can be designed as a separate component positioned next to the catalyst 9 or as an integral part of the catalyst 9. With the aid of the flame extinguisher, propagation of any flames occurring in the catalyst 9 is prevented, which could otherwise lead to thermal shock in the catalyst 9.
• the flame extinguisher is preferably designed so that the so-called hydraulic diameter of its duct-like or tube-like elements is of the order of 0.5-1.2 mm, which may vary, however, depending on the hydrogen concentration, the material selected etc. Effective flame-limiting can be achieved by means of an accurately adjusted hydraulic diameter.
• An alternative way of preventing flame formation in the catalyst 9 is to design the upstream end portion of the catalyst 9 without any catalytic coating.
• the supporting structure of the catalyst 9 is preferably made of a ceramic material, suitably cordierite.
• This ceramic material has a certain porosity and can in this way absorb the water that is formed during combustion of the hydrogen in the washcoat layer of the catalyst. This water evaporates during operation as a result of heat generation in the catalyst.
• the valve 16 can be controlled so that a pulsed supply of hydrogen is brought about, that is to say so that a periodic activation and deactivation of the valve 16 takes place.
• a control is possible because the valve 16 can be controlled electrically and is connected to the control unit 5.
• the control unit 5 can be adapted to switch the valve 16 on and off alternately.
• the valve can be controlled so that it is open for a tenth of a second and then closed for a corresponding time.
• the injection point (along the hydrogen gas line 15) for the air from the air pump is selected so that the hydrogen and the air are mixed well and also are supplied to the exhaust pipe 8 at a gas velocity that exceeds the flame velocity of the hydrogen/air mixture. In this way, the risk of a flame being propagated "backwards" in the line 15 is eliminated.
• an exhaust gas catalyst 9' can be combined with an HC adsorbent 2 .
• an HC adsorbent is known per se and is used for adsorption of HC impurities in the exhaust gases from the engine. After a given time, which corresponds to the HC adsorbent 24 being heated up and reaching a predetermined temperature, the adsorbed HC impurities are given off and in this way flow through the catalyst 9'. This means that the catalyst 9' then cleans the HC impurities.
• the HC adsorbent 24 is positioned next to the exhaust pipe 8 Between the HC adsorbent 24 and the catalyst 9', a volume 25 is formed, into which a mixture of hydrogen and air is fed via a line 26.
• the air is preferably supplied from a secondary air pump and is mixed in the line 26 with hydrogen, preferably from an electrolysis arrangement. The mixture is supplied to the volume 25 where combustion takes place. In this way, the catalyst 9 can be heated up to its light-off temperature rapidly.
• the invention is not limited to the exemplary embodiments described above and shown in the drawings but can be varied within the scope of the patent claims below.
• the abovementioned pre-crank and post-crank cycles can be combined, that is to say they can be initiated in a sequence one after the other during the starting sequence of the engine.
• the invention is effective for preventing both CO and HC poisoning of a catalyst.
• HC poisoning may occur mainly in diesel engines .
• hydrogen is produced on board the vehicle by an electrolysis process.
• the invention may use an exchangeable hydrogen gas container (for storing hydrogen under pressure) which is mounted in the vehicle and exchanged or refilled after it has been emptied.

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• 1997
  • 1997-07-18 SE SE9702757A patent/SE509787C2/sv not_active IP Right Cessation
• 1998
  • 1998-07-17 JP JP2000503329A patent/JP2001510260A/ja active Pending
  • 1998-07-17 WO PCT/SE1998/001396 patent/WO1999004145A1/en not_active Application Discontinuation
  • 1998-07-17 EP EP98934110A patent/EP1009923A1/en not_active Withdrawn

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