WO2014063811A1

WO2014063811A1 - Method for operating a charged, uniflow scavenged two-stroke internal combustion engine, a charged, uniflow scavenged two-stroke internal combustion engine and a recuperator

Info

Publication number: WO2014063811A1
Application number: PCT/EP2013/003180
Authority: WO
Inventors: Peter Kreuter
Original assignee: Peter Kreuter
Priority date: 2012-10-24
Filing date: 2013-10-22
Publication date: 2014-05-01
Also published as: DE102012020893A1; DE102012020893B4

Abstract

The invention relates to a method for operating a charged, uniflow scavenged two-stroke internal combustion engine comprising at least one piston (12) that moves back and forth in a cylinder (10) between a top dead centre (OT) and a bottom dead centre (UT), and comprising the following steps: feeding a fresh charge into a lower region of a working chamber (20) of the cylinder (10) when the piston (12) is in the region of UT thereof, discharging the combusted charge from the upper region of the working chamber (20), compressing the fresh charge by moving the piston (12) from the UT to the OT, igniting the compressed fresh charge when the piston (12) is located in the region of the OT thereof, and combusting said fresh charge at least as the piston begins to move from the OT to the UT; and characterised in that a recuperator (40), arranged in the working chamber between the piston and a cylinder head (22), is moved such that the combusted charge, prior to being discharged from the working chamber (20), flows through the recuperator (40) which is at a distance from the cylinder head (22), at least one portion of the fresh charge subsequently flowing through the recuperator (40) as the piston (12) moves from a UT, and then, before the piston (12) reaches the OT thereof, flowing through the recuperator (40) once more from the side thereof facing away from the piston (12) to the side thereof facing the piston, by virtue of said recuperator (40) being brought close to the cylinder head (12).

Description

Method for operating a supercharged, longitudinally-flushed two-stroke internal combustion engine as well as supercharged, longitudinally-flushed two-stroke internal combustion engine and recuperator

The invention relates to a method for operating a supercharged, longitudinally-flushed two-stroke internal combustion engine and a supercharged, longitudinally-flushed two-stroke internal combustion engine. which works by the method according to the invention. The invention further relates to a recuperator for such an internal combustion engine.

Two-stroke internal combustion engines are gaining in importance against the background of the need to reduce fuel consumption. Characterized in that the rotational angle of the crankshaft of two-stroke engine between two power strokes is half the angle of rotation of a four-stroke internal combustion engine with the same number of cylinders have two-stroke internal combustion engines high potential for downsizing, for example by reducing the number of cylinders.

The invention has for its object to improve the efficiency of two-stroke internal combustion engines.

A solution to this problem is achieved by a method according to claim 1. The fact that in the inventive method stored in a recuperator exhaust gas energy of the fresh charge is supplied in a thermodynamically favorable manner, the efficiency of the internal combustion engine, d. H. the removable on the crankshaft, usable for the propulsion of a vehicle mechanical power in relation to the fuel consumption.

Claim 2 is directed to a two-stroke internal combustion engine, which operates according to the inventive method.

The internal combustion engine according to the invention is further developed with the features of claims 3 and 4 in an advantageous manner.

Claim 5 is directed to a recuperator for use in an internal combustion engine according to the invention. The invention, which can be used for two-stroke internal combustion engines of different sizes and powers, self-igniting or spark-ignited, fueled with gasoline, diesel, fuel or gas, is explained below with reference to schematic drawings, for example and with further details.

They show:

1 is a schematic view of parts of a piston / cylinder unit of a two-stroke internal combustion engine according to the invention,

Fig. 2 is a perspective view of a recuperator, and

Figures 3 to 6 are side views of the piston / cylinder unit in different operating positions to explain the function of the internal combustion engine according to the invention.

According to FIG. 1, a two-stroke internal combustion engine, in the illustrated example a diesel internal combustion engine, has at least one cylinder 10 in which a piston 12 formed with a combustion bowl 11 is movable up and down in the axial direction of the cylinder. The piston 12 is connected to a crankshaft not shown in FIG. 1 via a connecting rod 14. In Fig. 1, the piston 12 is approximately in its lowest position, d. H. its bottom dead center (UT), in which it in the cylinder wall formed passages, such as inlet slots 16, releases, which connect an annular space 18 surrounding the cylinder 10 with a working chamber 20 in the interior of the cylinder 10. The working chamber 20 is limited as shown in FIG. 1 down from the piston 12 and upwardly from a cylinder head 22. In the cylinder head 22, at least one outlet opening is formed, which is closable with an outlet valve 24 and from which an outlet channel 26 leads to the outside.

More specifically, in the illustrated example, a recess or pocket 30 is formed in the cylinder head 22, whose diameter is equal to the diameter of the working chamber 20 and which extends the working chamber 20 of FIG. 1 upwards. The outlet opening, which is closable with the outlet valve 24, is formed in the bottom wall 32 of the pocket 30 which closes the working chamber 20 upwards. In a central part of the bottom wall 32, an annular groove is formed, via which the bottom wall 32 merges into a Ringansätz 36, the Working chamber 20 projects out. By means of the annular projection 36, an injection nozzle inserted into the cylinder head 22 protrudes into the working chamber 20 while sealing.

In the upper region of the working chamber 20, a recuperator 40 is arranged, the outer diameter of which is equal to or at most slightly smaller than the inner diameter of the working chamber 20.

As can be seen from FIG. 2, in the example shown, the recuperator 40 has a main body 42 of heat-resistant material, for example heat-resistant steel, with advantageously high thermal conductivity and high specific heat. The main body 42 is formed by a disc having a circular outer contour, which is provided with throughflow openings 44, for example through holes, which pass axially through the main body 42. For example, the thickness of the main body 42 is about 5 mm and are the through holes 44 with a diameter of about 1 mm, for example, and an areal density of, for example, about 25 / cm ² , the stated values being in no way restrictive.

In its middle region, the base body 42 has a collar 46, which encloses a central through-opening 48.

On the main body 42, a shaft 50 is rigidly fixed, which is similar to a shaft of the exhaust valve 24 passed through the cylinder head 22 with sealing linearly movable. Similar to the way in which the outlet valve 24 can be actuated by means of an outlet cam 52 in a manner known per se, the recuperator 40 is linearly reciprocatable by means of a recuperator cam 54.

The dimensioning of the collar 46 is such that the collar 46 at least substantially fluid-tightly surrounds the annular shoulder 36 of the cylinder head 22 and can be moved into the annular groove 34. The collar 46, the annular shoulder 36 and the annular groove 34 thus form sealing means which at least largely prevent fluid passage through the passage opening 48. To control the charge of the internal combustion engine, the annular space 18 is connected to an inlet channel 60, wherein for controlling the connection between the inlet channel 60 and the annular space 18, for example, an annular slide valve is provided, the annular slide is designated in Fig. 1 with 62. The annular slide 62 is rotatable in the example shown by means of its own drive or by the crankshaft of the internal combustion engine, not shown, in the clockwise direction, so that an inlet opening 64 of the annular slide 62 with the annular space 18 in alignment or the connection between the inlet channel 60 and the annular space 18 can be arranged occlusive. The function of a longitudinally purged two-stroke engine is known per se and will not be explained in detail here. For safe flushing of the working chamber 20, the compressed air is supplied to the inlet channel 60 via a compressor device, not shown, compressed air. The compressor device may include, for example, an exhaust gas turbocharger and / or a loader driven by the crankshaft or its own drive.

In the following, in particular, the function of the recuperator 40 will be explained with reference to FIGS. 3 to 6.

Similar to FIG. 1, FIG. 3 shows the piston 12 in its BDC, in which the piston 12 releases the inlet slots 16, so that fresh charge, for example compressed fresh air, flows into the working chamber 20 at the bottom. The exhaust valve 24 is open at this time and the recuperator 40 is located a short distance from the exhaust valve 24 in its BDC, ie its lowermost position in which the collar 46 slightly overlaps the collar 36. The inlet opening 64 of the annular slide 62 releases the connection from the inlet channel 60 to the annular space 18. The compressed, flowing in through the inlet slots 16 into the working chamber 20 fresh charge displaces the burnt during the previous working or expansion stroke charge from the working chamber 20, the burned charge through the through holes 44 of the recuperator 40 therethrough and the open _r exhaust valve 24 and into the outlet channel 26 flows. The working chamber 20 is rinsed.

The hot burned charge can leave the working chamber 20 only through the recuperator 40, since the collar 46 overlaps the annular shoulder 36 and the outer contour of the recuperator 40 largely coincides with the outer circumference of the working chamber 20. On in this way, the burnt charge transfers thermal energy contained in it to the recuperator 40, which is heated up.

During the subsequent upward movement of the piston 12 from its BDC (FIG. 4), the piston 12 passes over the inlet slots 16 and the inlet opening of the annular slide 62 moves out of overlap with the annular space 18 so that the inlet into the working chamber 20 is closed , The outlet valve 24 closes, so that the fresh charge is compressed in the working chamber 20 and through the recuperator 40 into the remaining above the recuperator volume of the working chamber 20, to which the volume of the bag 30 is heard, is pressed. The fresh charge takes in the recuperator 40 stored thermal energy and is thereby additionally heated.

Just before the piston 12 reaches its TDC, i. Shortly before the end of the compression stroke, the recuperator 40 is moved with further rotation of the Rekuperatornockens 54 from its UT according to Figures 3 and 4 in its TDC, in which the recuperator 40 at least approximately in contact with the bottom wall 32 of the bag 30 and the closed Exhaust valve 24 is located .. In this case, the collar 46 dips into the annular groove 34. The part of the compressed fresh charge located between the recuperator 40 and the bottom wall 32 is forced through the recuperator 40 back into the remaining space of the working chamber 20 or into the combustion bowl 11 of the piston 12, wherein the fresh charge continues to receive thermal energy from the recuperator 40.

When the piston 12 has reached its TDC (FIG. 5) and the recuperator 40 is in its TDC when the exhaust valve 24 is closed, the compressed fresh charge is largely in the combustion bowl 1 1. In this state, fuel is discharged from the

Injection nozzle 38 is injected into the combustion chamber trough 11, so that the combustion of the fresh charge begins and the piston 12 moves under work output from its TDC in the direction UT (Fig. 6). The outlet valve 24 remains closed. The recuperator 40 may initially remain in its TDC and then moves out of the pocket 30 into its BDC before the piston 12 reaches its BDC. When the piston 12 passes over the inlet slots 16, the exhaust valve 24 is opened. The rotary valve moves to a position in which it releases the connection to the annular space 18, so that the positions of FIG. 3 are reached again and the cycle starts again. With the example of a cylinder described internal combustion engine, a high efficiency is achieved because a large part of the thermal energy contained in the exhaust gas is stored in the recuperator and the fresh charge is supplied under the compression. The stroke of the recuperator 40 is small compared to that of the piston 12 and is for example 20%, advantageously 15%, more preferably only 10% of the piston stroke.

As can be seen schematically from the shapes of the cams 52 and 54 of FIG. 1, the exhaust valve 24 is only relatively short open during the phase during which the piston 12 releases the inlet slots 16. In this case, in particular as a function of the rotational speed of the internal combustion engine, the opening of the exhaust valve 24 already begin before the piston reaches the inlet slots and / or end after the piston has crossed the inlet slots on its way to the OT. The recuperator 40 remains relatively long in its UT, i. H. spaced from the bottom wall 32 and abuts the bottom wall only in the phase in which the piston is in its TDC and moves out of the TDC.

Instead of an exhaust valve, a plurality of exhaust valves may be used. The recuperator can be formed in different ways and, for example, provided with a plurality of passing through the cylinder head shafts 50. It is advantageous for the function of the recuperator that the burned charge leaving the working chamber 20 flows as completely as possible through the recuperator into the outlet of the internal combustion engine and effectively heats the recuperator, which has a sufficiently high heat energy storage capacity. Further, it is advantageous if the fresh charge in its compression flows through the recuperator first completely from the piston side to the side facing away from the piston and flows back before reaching the TDC of the piston from the side facing away from the piston side of the recuperator 40 to the side of the piston 12 back. The heat-storing region of the recuperator and its flow through can be designed in many different ways. In the central region of the recuperator, through which the injection nozzle 38 protrudes, a collar does not necessarily have to be formed. The recuperator can abut directly on the outer circumference of a correspondingly designed injection nozzle 38 and be movable along this outer circumference. The formation of a pocket in the cylinder head, the annular groove, the annular shoulder or the collar is not mandatory. The exhaust cam (s) 52 and the recuperator cam (s) 54 may be actuated by a common camshaft driven by the crankshaft. It is advantageous if the exhaust cam or the exhaust cam can be ordered in phase relative to the crankshaft. The inlet controlling rotary valve 62 can also be driven from the crankshaft ago, wherein the phase control of the rotary valve 62 is variable relative to the crankshaft for power control. The rotary valve can also be rotationally driven by its own drive, such as an electric motor. The rotary valve may be replaced by other suitable valves.

It goes without saying that several of the cylinders described can be combined to form a multi-cylinder internal combustion engine.

In forming the internal combustion engine with spark ignition, the injection nozzle 38 is replaced by a spark plug. In the case of direct injection in the combustion chamber, an injection nozzle may additionally be present. With external mixture formation of the fresh air is already flow above the inlet slots 16 fuel added.

If the piston 12 is formed without combustion bowl 1 1, a compression-determining distance may remain in the TDC of the piston between the piston top and the bottom of the recuperator.

List of reference cylinders

Combustion bowl

piston

pleuel

inlet slot

annulus

working chamber

cylinder head

outlet valve

exhaust port

bag

bottom wall

ring groove

annular shoulder

injection

recuperator

body

Durchströmöf tions

collar

Through opening

exhaust

Rekuperatornocken

inlet channel

rotary vane

inlet port

Claims

claims

1. A method for operating a supercharged, longitudinally-flushed two-stroke internal combustion engine having at least one piston (12) reciprocable in a cylinder (10) between a top dead center (TDC) and a bottom dead center (UT), comprising the following steps:

Feeding fresh charge into a lower region of a working chamber (20) of the cylinder (10) during the piston (12) located in the region of its BDC,

Pushing out burned charge from the upper area of the working chamber (20),

Compacting the fresh charge by moving the piston (12) from BDC to TDC, igniting the compressed fresh charge at located in the area of its TDC pistons (12) and

Burning the fresh charge at least during the beginning of the movement of the piston (12) from the TDC to the TDC,

characterized in that

a recuperator (40) arranged in the working chamber (20) between the piston (12) and a cylinder head (22) is moved in such a way that

the burned charge before it is expelled from the working chamber (20) flows through the recuperator (40) remote from the cylinder head (22),

then at least a portion of the fresh charge flows through the recuperator (40) during its movement of the piston (12) out of its UT

and then, before the piston (12) reaches its TDC, by approaching the recuperator (40) to the cylinder head (22) again flows through the recuperator from its side facing away from the piston (12) to its side facing the piston (12).

2. Charged, longitudinally-flushed two-stroke internal combustion engine, containing

at least one cylinder (10) in which a piston (12) connected to a crankshaft is reciprocally movable between a top dead center (TDC) and a bottom dead center (TDC) to form a variable-volume working chamber (20),

at least one inlet slit (16) formed in the cylinder wall, which releases a connection between the working chamber (20) and a fresh charge supply device (18, 60) when the piston (12) is in the BDC, at least one exhaust valve (24) with which one in a cylinder head (22) formed. Outlet opening is closable,

a recuperator (40) disposed between the piston (12) and the cylinder head (22) substantially fills the cross section of the working chamber (20) and is movable in the axial direction of the cylinder (10), and

Means for actuating the exhaust valve (24) and the recuperator (40) such that the exhaust valve (24) is closed during the movement of the piston (12) from the TDC to the vicinity of the TDC when the piston (12 ) is open and during the movement of the piston from near the UT to the OT is open and

the recuperator (40) is moved away from the cylinder head (22) at or before opening the exhaust valve (24) and is moved toward the cylinder head (22) after closing the exhaust valve before the piston (12) reaches its TDC.

3. Brennkaftmäschine according to claim 2, wherein the recuperator (40) has a plate-shaped base body (42) with flow openings (44) and at least one passage opening (48) in an axial direction of the cylinder with a cylinder head (22) recorded Component (50) is aligned and whose flow through capacity for a fluid flow from the working chamber (20) to the outlet valve (24) by means of sealing means (34, 36) is limited.

4. Internal combustion engine according to claim 2 or 3, wherein the exhaust valve (24) and the recuperator (40) from a common driven by a crankshaft of the internal combustion engine camshaft are actuated.

5. recuperator for use in a supercharged internal combustion engine according to claim 2, with a plate-shaped base body (42), pass through the through-flow openings (44) and is rigidly connected to a perpendicular to the surface of the body extending shank (50).