DE2550885A1 - Diesel engine with precombustion chamber - uses sintered ceramic inner surface with specified low thermal conductivity - Google Patents

Abstract

The diesel engine is of the type provided with a pre- combustion chamber (4). At least the inner surface (9) of this chamber is ina material whose thermal conductivity is maximum 0.01 and preferably around 0.005 or less cal. per an, sec. degree. The chamber is at least partly lined with zirconium oxyde. The lining may be up to 1 mm thick. The chamber may be a separate insert which is entirely in the material mentioned and preferably a sintered ceramic material.

Description

2550883

Doimler-Benz Aktiengesellschaft
Stuttgart-Untertürkheim

Daim Io 9οΐ / *> Ιο.11.75

Self-igniting internal combustion engine

The invention relates to a compression ignition internal combustion engine with each main combustion chamber provided ancillary room (vortex chamber, antechamber).

These adjoining rooms are important for the design of the combustion process. When starting such engines, these Adjoining rooms, however, represent fissures in the main combustion chamber, Via which a noticeable part of the compression heat is dissipated in an undesirable manner, in such a way that the ignition temperature is not achieved. One of the reasons for this is the high level of convection of the compressed air inside the adjoining rooms. For this reason, diesel engines with pre-chambers or with vortex chambers need special starting assistance. In pre-chamber engines, preheating is usually used, i.e. the resistance electrical heating of the air in the antechamber. This preheating is often used in particular for "personal

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-ST- Daim Io

cars perceived as annoying; next to it the glow plugs burn occasionally and give rise to anger. Another jump start is the ether injection.

The object of the invention is to provide the motors of the type mentioned at the beginning Kind to the effect that it can be started without any special starting help simply by turning it on from a cold state can be started.

This object is achieved in that the Kebenraum, at least with regard to its inner surface, made of a material with a thermal conductivity of at most about o, oil, preferably about 0.005 or less cal / cm s degree.

Due to the low thermal conductivity - carbon steel for comparison, for example, has a thermal conductivity of about 0.1, high-alloy chrome steel about o, o35 cal / cm s degree - due to this low thermal conductivity, there is thermal insulation of the adjoining rooms reached on the inside and the cooling effect of the adjacent room walls reduced to the compression heating. The result is that the compression end temperature of the invention equipped prechamber or swirl chamber motors with a cold start easily high enough for a Auto-ignition of the fuel.

The adjoining rooms can expediently with a zirconium oxide layer (Thermal conductivity about 0.005 cal / cm s degree) of preferably less than about 1 mm layer thickness coated be. The zirconium oxide layer can be applied by spraying.

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% - Daim Io 9ol / 4

Due to the heat-insulating coating of the adjoining rooms a rise in temperature in the load-bearing wall parts of the adjoining rooms is not to be expected, as this is a prerequisite it can be that the thermal coupling of the supporting secondary walls to the cooling circuit of the engine remains unchanged is equal to; on the other hand, a greater heat resistance has to be overcome on the heat supply side. This will work out overall result in a reduction in the temperature level of the more conductive, load-bearing wall parts of the adjoining rooms.

The adjoining rooms are usually designed as a separate insert part. The inventive purpose can also be achieved if the insert part as a whole is made of one of the materials mentioned Kind, preferably consists of a sintered ceramic.

The invention is explained briefly below with reference to an embodiment shown in the drawings; show it

1 shows a section through the cylinder head area of a prechamber diesel engine and

2 shows an antechamber insert in an enlarged individual illustration with a heat-insulating device according to the invention Inner coating.

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kr - Daim Io

In the pre-chamber diesel engine shown in detail a two-part prechamber insert 2/3 with a spherical prechamber 4 is provided on the cylinder head 1 and a neck-shaped connection 5 to the main combustion chamber 6. Injection valve 7 is provided on the prechamber.

To avoid excessive heat emission from the compressed gases to the wall parts of the antechamber insert 2/3 with a cold start are the parts of the antechamber insert on the inside 9 with a layer 8 made of zirconium oxide provided, which represents a large thermal resistance. The layer can be about 1 mm thick.

The air that is compressed into the antechamber and warmed up by the compression can only be very small Lose some of the compression heat. The result is that even with very cold engine parts and with cold intake air the compression end temperature is so high after a few compression processes at the latest that it is for a safe auto-ignition of the injected fuel is sufficient. A special start-up aid is therefore not necessary.

A thermal insulation of the adjoining rooms is in this regard therefore particularly effective because the compressed air flowing into the adjoining rooms creates a strong turbulence there is brought. This creates a very strong forced convection and - with the high heat gradient between the air and non-insulated adjoining room - a very large heat transfer

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Deim Io 9οΐ / Ί

corridor. Due to the thermal insulation according to the invention the heat gradient between the convected air and the wall surface is very much reduced, so that only a small one Heat transfer can occur.

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Claims (4)

25G0G85 Daim Io 9ol / 4 Expectations Self-igniting internal combustion engine with a side chamber (vortex chamber, antechamber) provided for each main combustion chamber, characterized in that the side chamber (4, 5) at least with regard to its inner surface (9) is made of a material with a thermal conductivity of at most about o, ol,
preferably of about 0.05 or less cal / cm s degree
consists. 2. Internal combustion engine according to claim 1, characterized in that the adjoining space is at least partially coated with zirconium oxide (layer 8). 3. Internal combustion engine according to claim 2, characterized in that the coating (8) is up to about 1 mm thick. 4. Internal combustion engine according to claim 1, with a
Adjoining space formed by a separate insert part, in particular an antechamber, thereby
characterized in that the insert as a whole consists of a material of the type mentioned, preferably of a sintered ceramic material. 709820/0135