DE4201018A1 - Exhaust gas treatment for IC engine - metering hydrogen@ and oxygen@ into exhaust duct to ignite and raise temp. to process exhaust products - Google Patents

Abstract

The exhaust gas treatment system has a gas generator (11) to produce hydrogen and oxygen from the electrolysis of water. The hydrogen is fed into the exhaust duct, as well as metered amounts of oxygen, and ignited by an igniter (8). The controlled burn is activated before the start of the engine and effectively removes exhaust products as well as carbon. The processor controlled ignition removes harmful exhaust products without requiring a costly catalyser and without loss of engine power. A second line of treatment can be provided by a small volume catalyser. ADVANTAGE - No harmful exhaust products emitted esp. when starting, no loss in engine performance.

Description

The invention relates to a method for the aftertreatment of Exhaust gas from an internal combustion engine according to the preamble of Pa claim 1.

Since it has not been possible with known gasoline or diesel engines Lich, the processed fuel-air mixture is complete to burn, there are various pollutants in the exhaust gases, for example hydrocarbons, carbon monoxide, carbon dioxide, Contain nitrogen oxides or soot particles. The aftercare of the Exhaust gases using catalysts or soot filters can indeed Reduce pollutant content in the exhaust gas, at the same time but fuel consumption increases. They also work both the catalyst and the soot filter only at higher temperatures satisfactory, which means that during cold starts and during the warm-up phase, however, larger quantities of pollutants to the um world.

From DE-OS 38 35 939 an exhaust system is known in which a catalytic converter before the engine starts by a Heating device preheated and from a predetermined temperature additional fuel is injected into the exhaust pipe. This method has the disadvantage that the one by the built catalyst increased fuel consumption by the one bring the fuel into the exhaust pipe increased even further becomes.  

From US 36 57 892 is a method in which ent in the exhaust gas hold water to water using a carbon substrate material gas and carbon monoxide is dissociated, known. Through the Subsequent oxidation of the hydrogen in the soot filter tempera necessary to burn off the deposited soot particles generated. The disadvantage here is that only after the start the internal combustion engine generates hydrogen and thus the tem temperature increase only after a start-up time. Furthermore only a small amount of hydrogen can be generated.

The object of the invention is now that described To eliminate disadvantages, i.e. to create a procedure with which the pollutants contained in the exhaust gas are reduced can without increasing fuel consumption.

The object is achieved by the features of the main demanding solved. Other advantages and configurations go from the subclaims and the description.

When using an exhaust gas afterburning operation is the Internal combustion engine with high excess air possible, which the The proportion of nitrogen oxides in the exhaust gas is significantly reduced. Therefore can be used if the nitrogen oxide limits are not met an additional catalyst can be dispensed with. Just as can in diesel engines by burning the soot particles in the Hydrogen burners do not use a soot filter will. In both cases, additional throttling of the Exhaust gases avoided, which leads to a reduction in fuel consumption needs leads. Contrary to using fuel as Additional fuel for the exhaust gas afterburning are at Combustion of hydrogen but no additional pollutants produced.  

By adding oxygen from electrolysis or from the ambient air can cool the exhaust gas and thus the exhaust gas temperature can be regulated in a simple manner. This is especially important to additional exhaust aftertreatment elements that further improve the exhaust gas quality in the Exhaust pipe are arranged to protect against overheating.

In addition, even before the start of the internal combustion machine the combustion of hydrogen in the exhaust pipe is ignited, the exhaust gas generated at the start is effective be burned. This can increase emissions Quantities of pollutants during cold start or during warm running phase can be prevented.

The production of hydrogen from water by means of electrolysis has the advantage that instead of a hydrogen storage only an easy-to-use water tank is required.

In the following the invention with reference to the drawing he purifies. It shows in detail

Fig. 1 is a schematic representation of an apparatus for performing the method according to the invention and

Fig. 2 is a schematic representation of another device for performing the method according to the invention.

Fig. 1 shows the exhaust system of a motor vehicle, not shown. The exhaust gas generated by an internal combustion engine 1 is emitted to the environment through an exhaust pipe 2 . For aftertreatment of the exhaust gases, hydrogen is introduced into the exhaust line 2 via a first line 3 and a first nozzle 4 . In addition, the exhaust gas line 2 is supplied with oxygen or air via a second line 5 and one or more nozzles 6 . A swirl plate 7 is also provided for better mixing of the hydrogen with the oxygen, the air or the exhaust gas. An ignition device 8 , which is supplied with the necessary ignition voltage by a high-voltage source 9 , is arranged downstream of the two nozzles 4 and 6 . Together with the ignition device 8, the two nozzles 4 and 6 form a hydrogen burner 10 . The required hydrogen and oxygen is formed in an electrolysis cell 11 , which is supplied with water from a storage container 12 via a feed line 13 . The operating voltage for the electrolysis cell 11 is provided via the supply line 14 by a control device 15 , which in turn is connected to the voltage supply of the motor vehicle via a supply line 16 . From the control device 15 , two valves 19 , 20 can be controlled via control lines 17 , 18 , with which the amount of hydrogen or oxygen supplied to the hydrogen burner 10 can be controlled. In addition, the amount of oxygen supplied can additionally be increased by an air pump 21 , which is controlled by the control unit 15 via a further control line 22 .

The control unit 15 is informed about all necessary operating parameters via various sensors. Via a tempera ture sensor 23 and a pressure sensor 24 upstream of the hydrogen burner 10 , the resulting exhaust gas mass flow is determined. The temperature of the afterburned exhaust gas can also be determined by a further temperature sensor 25 downstream of the hydrogen burner 10 . In addition, the control unit 15 receives information about the water level in the storage container 12 via a sensor 26 . After successful startup of the hydrogen burner 10, a signal for releasing the starting process is finally transmitted via line 27 .

By starting the hydrogen burner 10 before the start of the internal combustion engine 1 it is achieved that the resulting exhaust gas can be passed through the burning hydrogen immediately after the start of the internal combustion engine 1 and can thereby be combusted. On the other hand, the afterburning makes it possible to operate the internal combustion engine 1 with a higher excess air. This can lead to the amount of nitrogen oxides in the exhaust gas falling below the legal limit values. In this case, the use of an additional catalyst can be dispensed with. In addition, the soot burn-off filter can be dispensed with because of the direct afterburning of the exhaust gases in a diesel engine. Since exhaust systems without catalytic converter, or soot combustion filter, have a lower gas back pressure, the fuel consumption of the internal combustion engine 1 can also be reduced in this way.

The amount of hydrogen generated in the electrolysis cell 11 can be varied in a simple manner by the control unit 15 by changing the electrical charge supplied, for example as a function of the exhaust gas mass flow. In addition, the supply of hydrogen or oxygen to the exhaust pipe 2 can be controlled by the valves 19 , 20 . For example, the supply can be interrupted quickly if problems arise. Advantageously, the oxygen nozzle is arranged 6 upstream of the Wasserstoffdüse 4 so that hydrogen, which could possibly remain in the exhaust line 2 fuel burner 10 after switching off the water, tung by an increased addition of air by the pump 21 from the Abgaslei 2 may be blown out.

FIG. 2 shows a second exemplary embodiment of an exhaust system that has been slightly modified compared to FIG. 1, the same parts being identified by the same reference numbers.

Deviating from FIG. 1 is in the exhaust pipe 2 downstream of the hydrogen burner 10, a further exhaust gas treatment member 28 is disposed. This can be, for example, a catalyst or a soot burning filter. In a bypass line 29 to the exhaust gas aftertreatment element 28 , a differential pressure sensor 30 is arranged, which transmits the pressure increase in the exhaust gas line 2 generated by the exhaust gas aftertreatment element 28 to the control unit 15 . Here, the hydrogen burner 10 is used to afterburn the resulting exhaust gases at the start of the internal combustion engine 1 . On the one hand, part of the pollutants in the exhaust gas are removed directly by the afterburning; on the other hand, this quickly increases the operating temperature of the downstream exhaust gas aftertreatment element 28 . Both effects result in the exhaust gas aftertreatment element 28 working more effectively and thus the amount of pollutant released to the environment is reduced. Furthermore, the hydrogen burner can also be used to burn off a soot filter. In this case, the hydrogen burner is ignited only at certain time intervals or when a predetermined exhaust gas back pressure, which is determined by the differential pressure sensor 30 , is reached for a predetermined time interval. The differential pressure signal is determined for the exhaust gas aftertreatment element 28 when new. In operation, for example a soot filter, the value changes as a result of deposits. If a predetermined limit value is reached, the hydrogen burner 10 switches on and the filter is burned free.

In the case of a catalytic converter, the differential pressure measurement also provides information about the state of pollution, or wear. A continuous function or monitoring of the exhaust gas aftertreatment element 28 is thus ensured. A defective exhaust gas aftertreatment element can be recognized immediately as a result of exceeding or falling below predetermined limit values and a signal can be passed on to the control unit 15 .

By adding cold oxygen or cold ambient air through the pump 21 , overheating damage to the exhaust gas aftertreatment element 28 is excluded, since the cooling air flow is supplied to the exhaust gas as soon as the measured exhaust gas temperature exceeds a predetermined limit value.

Claims (9)

1. A method for the aftertreatment of the exhaust gas of an internal combustion engine, the exhaust gas being brought to a temperature necessary for the afterburning of the exhaust gas by the oxidation of gaseous hydrogen, characterized in that hydrogen gas is arranged in an exhaust gas line ( 2 ) on the internal combustion engine ( 1 ) ) is introduced and ignited. 2. The method according to claim 1, characterized in that in addition oxygen from the electrolysis or from the surrounding air is introduced into the exhaust line ( 2 ). 3. The method according to claim 2, characterized in that the exhaust gas temperature downstream of the gas inlet nozzles ( 4 , 6 ) measure ge and the amount of supplied oxygen or ambient air is increased with increasing exhaust gas temperature. 4. The method according to claim 1, characterized in that before the start of the internal combustion engine ( 1 ) oxygen and / or hydrogen gas is introduced into the exhaust line ( 2 ). 5. The method according to claim 1, characterized, that the hydrogen is obtained from water by means of electrolysis becomes. 6. The method according to claim 1, characterized in that the amount of hydrogen which is introduced into the exhaust pipe ( 2 ) is increased with increasing exhaust gas mass flow. 7. The method according to claim 1, characterized in that an ignition device ( 8 ) is provided in the exhaust line ( 2 ) downstream of the gas inlet openings. 9. The method according to claim 1, characterized in that a further exhaust gas treatment element ( 28 ) is arranged in the exhaust line ( 2 ) downstream of the gas inlet openings. 10. The method according to claim 9, characterized in that the pressure increase in the exhaust gas line ( 2 ) caused by the exhaust gas aftertreatment element ( 28 ) is measured.