WO2009054777A1

WO2009054777A1 - Method and apparatus for cleaning of crankcase gases, and combustion engine

Info

Publication number: WO2009054777A1
Application number: PCT/SE2008/051150
Authority: WO
Inventors: Hans Östman
Original assignee: Scania Cv Ab (Publ)
Priority date: 2007-10-25
Filing date: 2008-10-08
Publication date: 2009-04-30
Also published as: SE531591C2; SE0702378L

Abstract

Method for cleaning the crankcase gases (2) of a combustion engine (1), comprising the step of causing the crankcase gases to pass through a catalyst (4). The method is distinguished particularly by the step of causing a catalyst (4) arranged separately for cleaning the crankcase gases to be warmed by a separated flow of exhaust gases (5) from the engine (1) which is added to the crankcase gases (2) before they are led to the catalyst (4). The amount of the separated flow of exhaust gases which is added to the crankcase gases is controlled under the influence of a mixing valve (7). The invention also relates to a device for cleaning and to a combustion engine (1).

Description

Method and apparatus for cleaning of crankcase gases, and combustion engine

BACKGROUND

TECHNICAL FIELD

The present invention relates to a method for cleaning of crankcase gases according to the introductory part of the attached claim 1. The invention relates also to a device according to the introductory part of the attached claim 8. The invention relates also to a combustion engine according to the attached claim 15.

STATE OF THE ART

Crankcases of combustion engines have to be vented, but the crankcase gases, which contain inter alia drops of oil, are not to be released to the environment and have to be dealt with in some other way. The crankcase gases are usually mixed with combustion air to the engine in order to be burnt in the engine. However, the crankcase gas cannot be supplied to the engine's turbo unit, since oil carbonisation problems would be caused by the temperature rise in the turbo unit. The crankcase gases are therefore supplied to the engine's inlet pipe after the turbo unit and have therefore, for pressure adaptation, to be compressed, which leads to corresponding carbonisation problems due to temperature rise in the compressor which compresses the crankcase gas.

A known way of treating crankcase gases is by catalytic means, i.e. by catalyst. This requires a relatively high temperature to "ignite" the catalyst, i.e. to start the catalytic process, and to cause the catalyst to work as effectively as possible. Solutions in this respect have been proposed, US 3 846 980, in which the catalyst is warmed by being situated in or close to the engine's exhaust flow. This provides indirect warming which is relatively ineffective and constructionally less acceptable, with no effective cleaning taking place during the lengthy warm-up period. Electrical warming has also been proposed, DE 101 28 464 Al, which inter alia is expensive and involves investment.

RECORD COPY - TRANSLATION (Rule 12.4) The object of the present invention is to provide an effective solution for crankcase gas cleaning with regard to oil, which solution inter alia results in effective and constructionally acceptable catalyst warming. Warming the catalyst for catalytic treatment of crankcase gases with regard to oil can be effected at relatively low temperature levels owing to the structural characteristics of the oil, and such warming does not require much energy. The catalytic process of the catalyst leaves a gaseous process product which causes no carbonisation problems. The prerequisites are thus created inter alia for deciding whether the crankcase gas treated should be supplied to the engine's inlet pipe before or after the engine's turbo unit in a previously described manner.

SUMMARY OF THE INVENTION

The object indicated above is achieved with a method, a device and a combustion engine with features according to the attached claims 1, 8 and 15 respectively.

Further advantages are afforded by what is indicated in the respective dependent claims.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described in more detail below in relation to embodiment examples and the attached drawing, in which - Fig. 1 depicts schematically an embodiment of a device according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 depicts a combustion engine 1, e.g. a diesel engine intended for a heavy vehicle such as a truck 1 ', with crankcase venting whereby crankcase gases represented by an arrow 2 are vented out from the engine's crankcase 3 via line devices 2'.

RECORD COPY - FR ANSLATION

( Rule 12.4) A catalyst 4 is adapted to being supplied, via the line devices 2', with crankcase gases for cleaning to remove oil in drop form/particle form.

The catalyst 4 is adapted to being warmed, during operation, by a mixture of crankcase gases 2 and exhaust gases from the engine 1, which exhaust gases are represented by an arrow 5 and are extracted via line devices 5' from the engine's exhaust flow in order to pass through the catalyst.

The temperature of the catalyst, the process temperature, is intended to be raised by the gas mixture to initially the temperature for commencing the catalytic process of the catalyst, the so-called ignition temperature, and thereafter to be raised further to the optimum process temperature of the catalyst at which the catalyst performs its most effective cleaning.

The ignition temperature for preferred kinds of catalysts is about 150°C and the optimum process temperature is about 180⁰C as regards cleaning of gas to remove oil particles. The low ignition temperature and the optimum process temperature relate to the physical fact that the oil molecules are of very substantial length/size compared with, for example, hydrocarbons and nitrogen oxides.

Preferred embodiments involve using a catalyst of, for example, the kind used in current exhaust cleaning for combustion engines, although such catalysts result in definitely lower ignition temperatures and optimum process temperatures when the gas cleaning relates mainly to oil in particle form.

The ignition temperatures are between about 140 and 160⁰C, usually about 150°C, and the optimum process temperature is between 160 and 200⁰C, usually about 180⁰C, depending entirely on the catalyst used.

A catalyst of the preferred kind is an oxidising catalyst whereby the oil particles treated in the catalyst are converted to and emitted in the form mainly of carbon dioxide (CO₂) and water (H₂O).

RECORD COPY - TRANSLATION ( Rule ! 2.4) Particularly preferred versions involve using a catalyst of the same kind as is used in vehicle brake systems for cleaning of compressor-compressed air to remove oil in drop/particle form. Such catalysts are significantly less bulky than catalysts intended for cleaning of exhaust gases from combustion engines, as they are dimensioned for significantly smaller flows even if their technical configuration is otherwise similar.

Ref. 6 denotes sensor devices for detecting the temperature of the crankcase gases, which is usually about 100°C, and ref. 7 denotes a mixing valve adapted to being controlled by control means 8, on the basis of the crankcase gas temperature detected and a likewise known exhaust gas temperature, to control the amount of exhaust gas added to the crankcase gases. The control arrangement may, if considered advantageous, comprise sensor devices 9 for detecting the exhaust gas temperature and sensor devices 10 for detecting the temperature of the gas mixture before the catalyst, which temperatures are intended to be supplied to said control means 8.

According to embodiments which in certain cases are preferred, the crankcase venting is closed and there are line devices 11 for supplying to the combustion air inlet of the engine 1 the gas mixture treated in the catalyst, represented by an arrow 4', for burning. The gas mixture is preferably supplied via the engine's turbo unit 12, as schematically depicted in Fig. 1, together with combustion air, charge air, represented by an arrow 11 ', from an air filter. The turbo unit is usually followed by a charge air cooler 12' situated downstream of the turbo unit and upstream of the engine. Embodiments are also conceivable in which the gas mixture 4' is supplied to the engine after the turbo unit 12.

According to embodiments which in certain cases are preferred, the gas mixture treated in the catalyst is intended to be supplied to the engine's exhaust system 13, depicted schematically in Fig. 1, this being catered for by line devices 14 represented by broken lines.

Embodiments are also conceivable in which an existing crankcase gas cleaning system is supplemented by the catalyst for cleaning with regard to oil, whereby

RFCORD CX)PY - TRANSLATION (Rule 12.4 j the catalyst is warmed both by the crankcase gases and by exhaust gases from the engine as above.

The method and the function of the device according to the invention are probably substantially and sufficiently indicated above.

The crankcase gases are thus supplied to and caused to pass through a catalyst 4 specially arranged for cleaning the crankcase gases 2 to remove oil in particle form, which catalyst in this application ignites and works best at definitely lower temperatures than catalysts used in more general cleaning of exhaust gases from a combustion engine. The catalyst is warmed to ignition temperature and thereafter to optimum gas treatment temperature by adding a necessary amount of exhaust gases from the engine to the inherently warm crankcase gases for passing through the catalyst. The relatively low temperatures for ignition and optimum process function in combination with direct heat transfer in the catalyst result inter alia in a short start-up stage and a short period of inferior crankcase gas cleaning.

When the catalyst has thus by rapid warm-up been adapted to a suitable operating temperature, effective conversion of oil in the crankcase gases to more suitable residual products becomes possible.

The amount of exhaust gases from the engine which is thus diverted from the ordinary exhaust flow is in practice very small, of the order of a few percent or at least less than 5 percent of the total exhaust flow. This entails a corresponding reduction of the potential for recovering energy in a turbine which forms part of a turbo compressor unit, but this reduction is in practice marginal.

The invention is described above in connection with preferred embodiments and embodiment examples.

More embodiments as well as minor modifications and additions are of course conceivable without thereby departing from the basic concept of the invention.

RECORD COPY - TRANSLATION (Rule I -¹ h Thus embodiments are conceivable in which the catalyst 4 during, for example, a start-up stage is only supplied with exhaust gases for passing through the catalyst to quickly warm up the catalyst to optimum process temperature, before starting to add the crankcase gases which are to be cleaned of oil.

The invention is thus not to be regarded as limited to the embodiments indicated above but may be varied within the scope indicated by the attached claims.

'<? COR D α)i'Y ! F - NSLATION {Rale i - t,.

Claims

1. A method for cleaning of crankcase gases of a combustion engine, comprising the step of causing the crankcase gases to pass through a catalyst which is arranged as a separate catalyst for cleaning of the crankcase gases and is warmed by exhaust gases from the engine, characterised by the steps

- of extracting from the exhaust flow of the engine a separated exhaust flow (5) which is mixed with the crankcase gases (2), which mixture passes through the catalyst (4), and

- of the amount of exhaust gases (5) added to the crankcase gases (2) being controlled under the influence of a mixing valve (7).

2. A method according to claim 1 , characterised by the steps

- of detecting the temperature of the crankcase gases (2) and

- of controlling the mixing valve (7) on the basis of the crankcase gas temperature thus detected and a likewise known exhaust gas temperature.

3. A method according to claim 1 or 2, characterised by the step of controlling the mixing valve (7) in order to raise the process temperature of the catalyst (4) to initially the temperature for commencing the catalytic process of the catalyst (4), the so-called ignition temperature, and thereafter to the optimum process temperature of the catalyst (4).

4. A method according to any one of claims 1-3, characterised by the step of using exhaust gases (5) to bring about a crankcase gas/exhaust gas mixture with a temperature of at least about 140-160⁰C, particularly about 150⁰C, and preferably about 160-200⁰C, particularly about 180° C, for passing through the catalyst (4).

5. A method according to any one of claims 1-4, characterised by the step

- of cleaning the crankcase gas (2) from oil in particle form with the catalyst (4) thereto adapted, whereby the oil particles treated in the catalyst (4) are converted to and emitted in the form mainly of carbon dioxide and water.

RFCOK D COPY - ^■' Λ! ION i R. ik' ϊJ. h

6. A method according to any one of claims 1-5, characterised by the step of supplying to the combustion air inlet of the engine (1), preferably via a turbo unit (12), the gas (4') treated in the catalyst (4).

7. A method according to any one of claims 1-5, characterised by the step of supplying to the exhaust system (13) of the engine (1) the gas (4') treated in the catalyst.

8. A device for cleaning the crankcase gases of a combustion engine, comprising a catalyst together with devices for supplying the catalyst with crankcase gases, which catalyst is arranged as a separate catalyst for cleaning the crankcase gases and is adapted to being warmed by exhaust gases from the engine, characterised in that line devices (5') are arranged for extracting from the engine's exhaust flow a separated flow of exhaust gases (5) from the engine (1) for mixing with the crankcase gases (2) and passing together with the latter through the catalyst (4), and that a mixing valve (7) is arranged in the line devices (5') to control the amount of exhaust gases (5) added to the crankcase gas (2).

9. A device according to claim 8, characterised by devices (6) for detecting the temperature of the crankcase gases (2), and by the mixing valve (7) being adapted to being controlled, on the basis of the crankcase gas temperature detected and a likewise known exhaust gas temperature, to control the amount of exhaust gases (5) added to the crankcase gas (2).

10. A device according to either of claims 8 and 9, characterised in that control means (8) are adapted to controlling the mixing valve (7) so that the process temperature of the catalyst (4) is raised initially to the temperature for commencing the catalytic process of the catalyst (4), the so-called ignition temperature, and thereafter to the optimum process temperature of the catalyst (4).

11. A device according to any one of claims 8-10, characterised in that a crankcase gas/exhaust gas mixture with a temperature of about 140-160°C,

^■ \SΪ 4HON particularly about 150°C, but preferably about 160-200°C, particularly about 18O⁰C, is intended to be supplied to the catalyst (4).

12. A device according to any one of claims 8-11, characterised in that the catalyst (4) is adapted to treating oil in particle form in the crankcase gases (2) and thereby to converting and emitting the treated oil in the form mainly of carbon dioxide and water.

13. A device according to any one of claims 8-12, characterised by devices for supplying to the combustion air inlet of the engine (1), preferably via a turbo unit (12), the gas mixture (4') treated in the catalyst (4).

14. A device according to any one of claims 8-12, characterised by devices (14) for supplying to the engine's exhaust system (13) the gas mixture (4') treated in the catalyst (4).

15. A combustion engine characterised by a device according to any one of claims 8-14.

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