Two-stroke internal combustion engine

Abstract

A two-stroke internal combustion engine has at least one cylinder (1) receiving a piston (2) and having at least one injection nozzle (4) in the form of a multi-hole low-pressure nozzle inserted in a bore (5) in the cylinder jacket (6). The multi-hole low-pressure nozzle has a nozzle plate (15) with nozzle openings (16) arranged within an enveloping circle (17) to form a common nozzle jet (11) with an opening angle (α) dependent on the inclination of the nozzle axis (12) relative to the orifice surface of the bore and preventing the nozzle jet from being applied to the cylinder jacket. A resulting vector (14) from the velocity vector (13) of the nozzle jet in the direction of the nozzle axis (12) and the velocity vector (10) of the flushing air flow in the flow main direction defines with the cylinder jacket a maximum inclination angle (γ) of 20°.

Claims

1. A two-stroke internal combustion engine comprising: a cylinder having a cylinder jacket having a bore therein; said cylinder receiving a piston and having at least one injection nozzle comprising a multi-hole low-pressure nozzle inserted in the bore in the cylinder jacket; said cylinder during operation of the engine receiving air therein from one or more channels in a flushing airflow that flows in a main flow direction adjacent the bore in the cylinder jacket; wherein the multi-hole low-pressure nozzle comprises a nozzle plate with nozzle openings arranged within an enveloping circle so as to form a common nozzle jet; said nozzle jet injecting fuel into the cylinder at a nozzle-jet velocity with an opening angle (α) of injected fuel that is dependent on an inclination of a nozzle axis relative to an orifice surface of the bore; wherein the nozzle is positioned above the one or more channels and injects fuel into the cylinder only above the piston, and the opening angle (α) is angled away from the cylinder jacket by an angle great enough that fuel injected by the nozzle jet is prevented from being applied to the cylinder jacket; and wherein the nozzle is supported in a position and orientation such that a velocity vector of the nozzle jet velocity in a direction of the nozzle axis combined with a velocity vector of the flushing air flow in the main flow direction results in a resulting vector for a total flow of a fuel-air mixture from the fuel injected by the nozzle jet and the airflow that is at an inclination angle (γ) relative to the cylinder jacket that is not greater than 20°.

2. A two-stroke internal combustion engine according to claim 1, wherein the nozzle plate has at least three nozzle openings distributed over the circumference of the enveloping circle.

3. A two-stroke internal combustion engine according to claim 2, wherein the enveloping circle of the nozzle openings has a diameter corresponding to at least one third of a radius of the bore in the cylinder jacket receiving the injection nozzle.

4. A two-stroke internal combustion engine according to claim 1, wherein the enveloping circle of the nozzle openings has a diameter corresponding to at least one third of a radius of the bore in the cylinder jacket receiving the injection nozzle.

Description

BRIEF DESCRIPTION OF THE INVENTION

(1) In the drawing, for example, the subject matter of the invention is shown, wherein:

(2) FIG. 1 shows a two-stroke internal combustion engine according to the invention in sections in an axial section through a cylinder,

(3) FIG. 2 shows an injection nozzle inserted into a bore in the cylinder jacket and exposed in the area of the nozzle plate on a larger scale, and

(4) FIG. 3 shows the injection nozzle according to FIG. 2 inserted into the bore in a front view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) According to FIG. 1, a two-stroke internal combustion engine according to the invention comprises at least one cylinder 1 with a piston 2, which is shown in the lower dead center position. An injection nozzle 4 is provided on the cylinder side opposite an outlet channel 3, which is inserted into a bore 5 in the cylinder jacket 6. Between the crankcase (not shown) and the combustion chamber of the cylinder 1, overflow channels 7, 8 are disposed opposite each other in pairs with respect to the drawing plane. In addition, the cylinder 1 has an overflow channel diametrically opposed to outlet channel 3 as an upright channel 9. The flushing air flow caused by the overflow channels 7, 8 and the upright channel 9 has a velocity vector 10 in the direction of the resulting main air flow. The fuel is injected into the combustion chamber in the form of a nozzle jet 11 in the direction of the nozzle axis 12. The velocity vector of the nozzle jet in the direction of the nozzle axis 12 is marked with reference numeral 13. The velocity vector 13 of the nozzle jet 11 forms a resulting vector 14 with the velocity vector 10 of the flushing air flow, which vector 14 is decisive for the total flow resulting from the flushing air flows and the nozzle jet 11 and illustrates the flow path of the fuel-air mixture in the combustion chamber.

(6) The front surface of the flushing air flow should undergo as little change as possible in its course by the nozzle jet 11 in order to be able to create a good displacement purge. For this reason, the fuel should be fed as evenly as possible into the air flow via the flushing air front. In the area where the flushing air stream and nozzle jet 11 meet, this requires a cross-sectional area of nozzle jet 11 adapted to the flushing air front on the one hand and a comparatively small impulse of the nozzle jet 11 on the other. Despite these conditions, the nozzle jet should not be applied to the cylinder jacket 6 due to a Coanda effect. This means that the opening angle α of the nozzle jet 11 must remain limited with regard to the inclination angle of the nozzle axis 12 in relation to the cylinder axis in order not to fall below the application angle decisive for the Coanda effect. According to FIG. 1, at the given opening angle α the smallest angle β between the jacket of the nozzle jet 11 and the cylinder jacket 6 must therefore not fall below the application angle. On the other hand, this means that the opening angle α of the nozzle jet 11 must be limited accordingly if the nozzle axis 12 has a given angle of inclination.

(7) In order to meet these different requirements with simple constructional means, the injection nozzle 4 is designed in the form of a multi-hole low-pressure nozzle with a nozzle plate 15, whose nozzle openings 16 are arranged within an enveloping circle 17 in such a way that the individual nozzle jets merge into a common nozzle jet 11, whose opening angle α can be specified by the orientation of the nozzle openings 16. If, according to FIG. 2, the injection valve 4 is opened by applying pressure to the valve body 18, the fuel is injected into the combustion chamber through the nozzle openings 16 with a comparatively low impulse in the form of nozzle jet 11 and hits the resulting flushing air flow there in order to distribute itself finely in this air flow without disturbing the flushing air flow. According to FIG. 1, the fuel-air mixture is guided away from the piston crown upwards against the cylinder head in accordance with the flow conditions, wherein the velocity vectors 10, 13 determine the flow path for the air flow on the one hand and for the nozzle jet 11 of the injected fuel on the other hand. This flow path of the fuel-air mixture should not be applied to the cylinder jacket 6 to prevent the cylinder jacket 6 from being wetted with fuel. This is successful if, with a resulting vector 14 inclined against the cylinder jacket 6, the angle of inclination γ of this vector 14 relative to the cylinder jacket 6 is at most 20°.