DE102017213705A1 - Method and device for reducing the emissions of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for reducing pollutants from exhaust emissions. The basic idea of the invention is that water is supplied in excess to the fuel mixture at time intervals T1 during certain periods of time T2.

Description

The invention relates to the field of internal combustion engines, thus the gasoline or diesel engines or other internal combustion engines.

A major issue of our time is the pollution of air by particulate matter and nitrogen dioxide (NO ₂ ). The limit value of NO ₂ outdoors is discussed. 40 micrograms per cubic meter are required as the highest value. The official permissible fine dust values are also narrow, at least in Germany.

Very serious is the problem of soot and the associated pollution. Large seagoing vessels use heavy fuel oil of various qualities. The installation of particle filters leads to a certain success. However, the particles retained by a filter must be eliminated. This is done by burning, which is expensive.

For years, an emulsion of fuel and water (KWE) has been generated and fed to the engine instead of pure fuel. Contributions to this topic were provided by the inventor, see DE 41 39 782 . EP 92 12 0388 . DE 198 15 752 ,

The application of the KWE process has certain advantages with regard to the reduction of NO _x and of soot particles. However, further improvement is desirable.

For this purpose, storage catalysts have already been used. These serve to store NO _x , and thus the reduction of NO _x in the emission of the exhaust gas.

Modern lean mix engines work with excess oxygen. The resulting in lean-burn nitrogen oxides are stored in the storage catalyst as nitrates. Since a part is present as NO, it must first be oxidized to NO ₂ . If the storage capacity of the catalyst is exhausted, a rich reducing exhaust gas mixture is temporarily adjusted via the engine control in order to clean the catalyst. It is thus briefly added fuel, thus more than is necessary for burning. In these cyclically occurring fat phases (lambda <1), in which sufficient reducing agent (H ₂ , CO and HC) is provided at a low oxygen concentration, for example less than 1%, the stored nitrates and the reducing agents react to form N ₂ , H ₂ O and CO ₂ .

The oxidation of CO and C _m H _n is still possible in oxygen excess at lambda> 1 analogous to the conventional three-way catalyst, but nitrogen oxides NO _x must be cached. Their catalytic reduction succeeds only in a stoichiometric to rich exhaust gas mixture. New engines therefore require an advanced type of catalyst with additional chemical elements that allow storage of nitrogen oxides. To meet current emission standards, diesel passenger cars are equipped with NO _x storage catalytic converters.

To achieve this intermediate storage of nitrogen oxides, a noble metal catalyst such as platinum and a NO _x storage component are applied to suitable supports, for example an alkaline earth metal such as barium carbonate or barium oxide. In the lean, that is, oxygen-rich atmosphere, the nitrogen oxides are oxidized under the action of the noble metal catalyst and absorbed to form nitrates such as barium nitrate in the catalyst and thus removed from the exhaust gas stream.

The regular "enrichment" causes these reactions to proceed in opposite directions; the NO _x molecules are returned to the exhaust gas stream and further reduced by the reducing components present in the rich atmosphere, such as C _m H _n - unburned hydrocarbons - and / or CO. The storage catalyst can store NO _x only in a temperature range of 250 to 500 ° C. The temperature window is reached by triple-flow exhaust pipes or exhaust bypasses.

If the absorption capacity of the catalyst is exhausted, the engine electronics temporarily set a rich, reducing exhaust gas mixture (for about two seconds). In this short fat cycle, the nitrogen oxides cached in the catalyst are reduced to nitrogen, thus preparing the catalyst for the next storage cycle. By doing so, it is also possible to minimize the pollutant emissions of economical lean burn engines and to comply with valid limit values of the Euronorm. The absorption capacity (about 60 to 90 seconds) is monitored by a NO _x sensor.

The invention has for its object to improve the method mentioned, in particular the _NOx -components more reliably prevent and reduce the time of changing the exhaust gas mixture by changing the fatness degree.

This object is solved by the features of claim 1. Accordingly, the inventor takes a straight opposite path, as the prior art. Instead of overfatting the exhaust gas mixture, the inventor proposes a brief overhydration, thus an addition of water. this leads to to an excess of unburned fuel as well as to an excess of CO. This binds NO _x and can be eliminated.

• 1 zeigt ein Stapeldiagramm, das bei zwei unterschiedlichen Geschwindigkeiten den verbleibenden NO_x-Wert wiedergibt, und zwar einmal bei Verwendung von Dieselkraftstoff, und einmal bei Anwendung der Erfindung.
• 2 zeigt ein Stapeldiagramm, das die verbleibende Partikelmenge wiedergibt, und zwar einmal bei Verwendung von Dieselkraftstoff, und einmal bei Anwendung der Erfindung.
• 3 zeigt einen bekannten Speicherkatalysator in räumlicher Darstellung.

The invention is explained in more detail with reference to the drawing. It details the following:

• 1 Figure 12 is a stack diagram showing the remaining NO _x value at two different speeds, once using diesel fuel and once using the invention.
• 2 Figure 11 is a stack diagram showing the amount of particulate remaining once using diesel fuel and once using the invention.
• 3 shows a known storage catalyst in a spatial representation.

How to get out 1 recognizes the application of the invention results in more favorable NO _x values in the exhaust gases leaving the catalyst. At a vehicle speed of 120 km / h, the remaining amount of NO _x is 2% lower than when using diesel fuel.

At higher speeds, namely 140 km / h, when using the invention significantly less NO _x remains in the exhaust gas, as with the use of diesel fuel.

2 shows the relationships with respect to soot particles. The improvement in applying the invention is downright dramatic. At a driving speed of 120 km / h 51% particles remain in the exhaust gas less than without application of the invention, namely when driving with diesel fuel.

At a driving speed of 140 km / h, the particulate content is even 71% lower when the invention is applied than when diesel fuel is used.

The in 3 Catalyst shown is a storage catalyst. It includes a housing 1 , a pressure sensor 2 , an exhaust gas temperature sensor 3 , a lambda probe 4 , a diesel particulate filter 5 , the actual NO _x storage catalyst 6 , as well as an exhaust temperature sensor 7 , Efficiency progressively increases with KWE operation at higher load.

The fuel-air mixture is intermittently, that is supplied at short intervals water, in each case at intervals. Thus, the optimal combustion is interrupted during the addition of water for a short time. It creates the necessary CO and HC components. When the exhaust gas is introduced into the catalyst, the said components purify the catalyst of NOx. The method according to the invention can thus be summarized as follows:

Although the use of a water-fuel emulsion (KWE) is also described here in the exemplary embodiment, solutions without WKE are also suitable, so that the injection or supply of gaseous fuel-air mixtures come into consideration. Very important is the over-watering of the fuel mixture feeding the engine.

In the inventive addition of water to the fuel-air mixture, there is the formation of HC, CO and CO ₂ , so that the nitrate compounds are reconverted and precipitated in the storage catalyst.

The benefits are quite significant. The work area can be greatly expanded, especially at higher load. Increases of 50 ° C are possible.

The storage capacity is much higher than with the conventional intermittent addition of fuel.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4139782 [0004]
• EP 92120388 [0004]
• DE19815752 [0004]

Claims (4)

A method of reducing pollutants from exhaust emissions, comprising the following features: 1.1 introducing a fuel-air mixture; 1.2 passing the exhaust gases of the engine through a catalyst, in particular by a storage catalytic converter; characterized by the following features: 1.3 the fuel mixture is over-watered at time intervals T1 during certain periods of time T2; 1.4 the pollutants are removed from the catalyst. Method according to Claim 1 characterized by the use of the fuel-water emulsion process. Method according to Claim 2 , characterized in that the emulsion 5 to 30 wt .-% of water are supplied, based on the amount of emulsion. Method according to Claim 1 to 3 , characterized in that the duration T2 of the overhydration is between 2 and 120 s.

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