RU2499150C1 - Method of gas exchange in two-stroke ice - Google Patents

Abstract

FIELD: engines and pumps.SUBSTANCE: combustion products are vented from cylinder cavity via openings released by the piston and directed into atmosphere via exhaust manifold. Then, cylinder cavity is scavenged by fresh charge and filled via inlet ports cleared by the piston to bypass the fresh charge portion from cylinder cavity into exhaust manifold tight after combustion chamber with filling the part of exhaust manifold with said fresh charge. Then, exhaust manifold is shut off by slide valve timed with piston to bar the combustion products for increase in exhaust manifold pressure upstream of said slide valve. Thereafter, increased gas pressure upstream of said slide valve displaces the fresh charge fed in exhaust manifold back towards the cylinder. Thus fresh charge is forced from exhaust manifold shutoff by slide valve into cylinder cavity via open outlet ports by the energy of combustion products. Now, inlet and outlet ports are closed by the piston at the compression stroke start. Note here that before closure of inlet ports by the piston, at least, before said moment, pressure outside the cylinder, in the area of inlet ports, is increased to constrict the fresh charge release from cylinder cavity.EFFECT: higher specific power of two-stroke engine.3 cl, 6 dwg

Description

The invention relates to the field of mechanical engineering, namely, to two-stroke internal combustion engines.

A known method of organizing gas exchange in a two-stroke engine by releasing the cylinder cavity from combustion products through exhaust gas distribution bodies, releasing them into the atmosphere through the exhaust manifold with the formation of a pressure wave directed towards the cylinder, to create resistance to the movement of the fresh charge supplied to the cylinder cavity and reduce due to this direct release of fresh charge into the atmosphere (GB 2321498 A publ., 07.29.1998).

The disadvantages of this method are the low efficiency of the charge return to the cylinder, since the sound wave does not have the ability to change the direction of motion of the gases moving in the exhaust manifold. In addition, the creation of a constant resistance to the movement of gases in the exhaust manifold prevents both the cleaning of the cylinder and the displacement of fresh combustion products from the cylinder cavity and does not allow the cylinder of the two-stroke engine to be sufficiently filled.

There is a method of operating a two-stroke engine by releasing the cylinder cavity from the combustion products through exhaust gas distribution bodies, releasing them into the atmosphere through the exhaust manifold with overlapping the passage section of the exhaust channels in order to prevent direct release of fresh charge into the atmosphere (see application US 2003/0230258, publ. 12/18/2003).

The effectiveness of this method is higher than the method with wave release, however, the resistance to the movement of combustion products also increases, since the spool on most engine operating modes constantly throttles the section of the exhaust manifold. In addition, there are problems with the heat resistance of the spool body located next to the outlet windows, and the sealing of its drive.

The closest technical solution to the claimed one is the method of organizing gas exchange in a two-stroke engine, which consists in the fact that the working cavity of the cylinder is freed from the combustion products through the exhaust windows opened by the piston, with their direction into the atmosphere through the exhaust manifold, they are blown and filled with a fresh charge through the cylinder cavity through the purge windows opened by the piston pass part of the fresh charge, without interfering with its movement, from the cylinder cavity into the exhaust manifold after the combustion products by supplying parts of the exhaust manifold with a fresh charge, then the section of the exhaust manifold is closed with a spool body synchronized with the movement of the piston, blocking the movement of combustion products and thereby increasing the pressure in the exhaust manifold in front of the spool body in the direction of gas movement from the cylinder cavity, the fresh charge entering the exhaust is displaced the collector, by increased gas pressure in front of the spool device, back in the direction of the cylinder and pump a fresh charge from the blocked spool device by means of the exhaust manifold into the cylinder cavity through the open exhaust windows due to the energy of the combustion products, after which the purge and exhaust windows are closed with a piston at the beginning of the compression stroke (see WO 2010/044703 A2, publ. 04/22/2010).

The disadvantage of this method is the short period of time during which it is possible to fill the cavity of the cylinder through the outlet windows with the purpose of boosting, namely, after closing the purge windows, which prevents in this case the fresh charge from the cylinder coming back through the purge windows.

The technical result of the claimed invention is to increase the specific power of a two-stroke engine by increasing the degree of boost when returning a fresh charge coming out of the cylinder during blowing, which allows both recharging and boost of a two-stroke engine without loss of charge.

The problem is achieved by implementing a method of organizing gas exchange in a two-stroke engine, which consists in the fact that the cylinder cavity is freed from the combustion products through exhaust windows opened by the piston, with their direction into the atmosphere through the exhaust manifold, purged and filled with a fresh charge through the cylinder cavity, opened by the piston, bypass part of the fresh charge, without interfering with its movement, from the cylinder cavity to the exhaust manifold after the combustion products with fresh filling near a part of the exhaust manifold, then the exhaust manifold cross-section is blocked by a spool body synchronized with the movement of the piston, blocking the movement of combustion products and thereby increasing the pressure in the exhaust manifold in front of the spool organ along the gas flow from the cylinder cavity, displaces the fresh charge received in the exhaust manifold, increased gas pressure in front of the spool device back in the direction of the cylinder and pump a fresh charge from the outlet blocked by the spool device the collector into the cylinder cavity through open exhaust windows due to the energy of the combustion products, and then close the purge and exhaust windows with a piston at the beginning of the compression stroke, and during the period before the piston closes the purge windows temporarily, at least until the piston closes the purge windows, increase the pressure in the region of the purge windows outside the cylinder, thereby limiting the release of fresh charge from the cylinder cavity.

The task is also achieved by the fact that they can purge by supplying a fresh charge to the cylinder cavity from a variable piston piston chamber communicated with the purge windows through the purge channels, while increasing the pressure in the region of the purge windows outside the cylinder by supplying a fresh charge pumped from the exhaust manifold into the sub-piston chamber in communication with the exhaust manifold by means of a channel with a locking body installed in it, or they can purge the path supplying fresh charge to the cylinder cavity through purge windows from a constant-volume purge chamber communicated with the supercharger by means of an inlet channel with a shut-off element installed in it, while increasing the pressure in the region of the purge windows outside the cylinder by supplying an additional charge to the purge from the exhaust manifold the camera.

The invention is illustrated using the drawings.

Figure 1 shows a variant of the engine with a piston blow, which implements the claimed method;

Figure 2 is the same, a variant of the engine with a purge, carried out using a supercharger;

Figure 3-6 shows the sequence of gas exchange in the embodiment of the engine shown in figure 1, while in figure 3 - the moment the piston opens the exhaust windows and the beginning of the free release of combustion products;

Figure 4 - the end of the free release and the beginning of the purge of the cylinder cavity through the opening of the piston purge windows;

Figure 5 - overlapping spool of the exhaust manifold and the beginning of the reverse movement of part of the combustion products in the direction of the cylinder cavity;

Figure 6 - return released from the cylinder fresh charge before the piston closes the purge and exhaust windows.

The claimed method is implemented in an engine containing a piston 1 installed in the cylinder 2 with the formation of the working cavity 3. The piston 1 controls the opening and closing of the exhaust windows 4 and the purge windows 5. The piston 1 is connected to the drive shaft (not shown) with a connecting rod or rod 6. The piston 1 can be installed with the formation of the piston chamber 7 of variable volume. In this case, the cavity 3 of the cylinder 2 is purged by displacing the fresh charge from the sub-piston chamber 7 through the purge channels 8 through the purge windows 5.

The purge can also be carried out by supplying a fresh charge under pressure using a blower (not shown in the drawings) through the inlet channel 9 to the purge windows 5 through the purge chamber 10, communicating with the working cavity 3 only through the purge windows 5. At the inlet of the inlet channel 9 to the purge a shut-off element is installed in the chamber 10, for example, a non-return valve 11. Moreover, the supercharger can also be used in the engine variant with a purge from the sub-piston chamber 7.

The exhaust windows 4 are in communication with the exhaust manifold 12, in which a spool device is installed, for example, a rotating disk 13 with a cutout for the passage of gases, with the possibility of overlapping the cross section of the exhaust manifold 12 for a predetermined time. The spool disk 13 is kinematically connected to the drive shaft (not shown in the drawings).

The exhaust manifold 12 is in communication with either the sub-piston chamber 7 or the purge chamber 10 by means of a bypass channel 14 in which a shut-off element is installed, for example, a bypass valve 15, which can be either controlled or self-acting.

The engine may contain a supercharger (not shown in the drawings), which supplies a fresh charge to either one of the inlet channels or both.

The engine in which the claimed method is implemented operates as follows. Fresh charge is supplied to the sub-piston chamber 7 either under the action of the vacuum created by the piston 1 moving towards the TDC, or under the excess pressure created by the supercharger. From the piston chamber 7, fresh charge is supplied through the purge channels 8 to the purge windows 5. Either the fresh charge is supplied by a supercharger under pressure to the purge chamber 10, for example, acting as a purge receiver.

At the end of the expansion stroke, the piston 1 first opens the exhaust ports 4, and the free release of combustion products into the exhaust manifold 12 begins (FIG. 3). Moreover, in the constructive way, the maximum possible time-section of the free release is achieved. In this case, the cavity 3 of the cylinder 2 is freed from the combustion products at the highest possible speed, which allows not only to completely clean it, but also to create a vacuum (Kadenashi effect) to increase the pressure drop between the cavity 3 and the sub-piston chamber 7 or the inlet channel 9, which directly feeds fresh charge from the supercharger. With this approach to blowing a two-stroke engine, there is no need to solve the problems associated with choosing the angles of direction of the blowing channels to cylinder 2 (arising from the design of known engines) to prevent fresh charge from being transferred to the exhaust manifold and mixing the fresh charge with the combustion products.

When implementing the claimed method of operation, it is only necessary to provide minimal resistance to the passage of a fresh charge into an already empty cavity 3 of the cylinder through the purge channels 8 and through windows 5 and 4 to the exhaust manifold 12.

After the free release ends with the piston 1, the purge windows 5 open, and the cavity 3 is filled with a fresh charge either from the sub-piston chamber 7 or from the purge chamber 10 with the exhaust ports 4 open (Fig. 4). The cavity 3 is filled until a fresh charge begins to exit through the outlet windows 4 (Fig. 5) into the exhaust manifold 12.

It should be noted that the direction of exit of the purge channels into the cavity 3 at an angle to the surface of the cylinder 2 in any plane reduces the consumption of fresh charge during purging.

The free filling of the cavity 3 of the cylinder 2 is also prevented by any throttling of the exhaust manifold (a technique very common in the state of the art) to reduce direct losses of fresh charge. In this regard, it should be noted that the use of wave resonators in the exhaust system is ineffective and does not contribute to the return to the cylinder cavity of the fresh charge that has already left it. In essence, this is the same throttling in the area of the outlet windows, but in the short-term settlement period.

At the end of the filling of the cavity 3, when implementing the inventive method, at a considerable distance from the cylinder 2, the exhaust manifold 12 is blocked by the spool disk 13 (Fig. 5), blocking the path of the combustion products leaving the cavity 3. At the same time, the pressure in the blocked exhaust manifold 12 increases, obstructing the movement of the fresh charge emerging from the cavity 3 along the exhaust manifold 12. Moreover, the pressure of the combustion products in the exhaust manifold 12 squeezes the fresh charge back into the cavity 3 (Fig.6).

At this point, both the purge 5 and outlet 4 windows have not yet been closed by the piston 1 that has passed the BDC, so a fresh charge is supplied from the exhaust manifold 12 to the cavity 3 both through the outlet windows 4 and into the bypass channel 14. The pressure wave passes through the bypass channel 14 to the purge windows 5 and prevents the exit through them from the cavity 3 of the charge, pressed by the charge transferred to the cavity 3 from the exhaust manifold 12.

In known engines, a piston moving from a BDC squeezes a significant amount of fresh charge both through the exhaust ports into the exhaust manifold and through the blowdown windows back into the piston chamber.

In an engine operating according to the claimed method, essentially, recharging of cavity 3 of cylinder 2 takes place through still not purging 5 and exhaust 4 windows. It is possible to achieve such a phenomenon as “recharging” even in the absence of a supercharger if a fresh charge passes through the entire cavity 3, completely filling it, and goes into the exhaust manifold 12, without experiencing significant resistance, both when passing through the purge channels 8 and windows 5, and when leaving the cavity 3. It is also desirable that the amount of harmful volume in the sub-piston chambers is as low as possible, then the purge will be more intense, the phenomenon of inertial pressurization of a fresh charge into the sub-piston chamber will occur 7 and, accordingly, into the cavity 3 of cylinder 2. That is. the more fresh charge leaves the cavity 3 after it is filled, the greater will be its filling due to recharging before closing the outlet windows 4.

All the actions listed in the previous paragraph are unacceptable during the organization of the working process in two-stroke engines of the prior art, as they lead to significant direct losses of fresh charge and insufficient charge supply due to increased resistance to its movement.

In order to reduce the reverse bypass of the fresh charge from the cavity 3 at the time of recharging from the side of the exhaust manifold 12, in the closest claimed method, the purge pressure is increased and the operation of the exhaust system is adjusted so that recharging through the outlet windows 4 begins later than the purge windows 5 close However, in this case, the recharge time section is significantly reduced, which is determined, in fact, by the difference in the heights of the purge 5 and outlet 4 windows.

To increase the filling of the cavity 3 of the cylinder by increasing the time-cross-section of the charge supply through the outlet windows 4 due to the earlier start of the charge return, it is necessary to prevent the fresh charge from leaving the cavity 3 through the still uncleaned purge windows 5. For this, during the discharge of the fresh charge from the exhaust manifold 12 into the cavity 3 of the cylinder increase the pressure in the region of the purge windows 5 outside the cylinder 2. There are various options for implementing a pulsed increase in pressure at a given moment, for example, using resonance s Helmholtz or by short-term supply of fresh charge portion of the air or gas accumulator.

Thus, the implementation of the claimed invention allows:

- increase the specific power of the engine due to the possibility of boosting the two-stroke engine without loss of charge with a larger actual time-cross-section of the supply of fresh charge into the cylinder;

- to increase the reliability and life of the engine by reducing the thermal tension of the cylinder-piston group and exhaust organs by passing part of the cold fresh charge through the exhaust windows, both leaving the cylinder during purging, and in the opposite direction when returning the part of the fresh charge that has left the cylinder.

- reduce the toxicity of combustion products as a result of preventing direct loss of fuel and oil, and by reducing oil consumption due to a decrease in the thermal tension of the cylinder-piston group.

Claims (3)

1. The method of organizing gas exchange in a two-stroke engine, which consists in the fact that the cylinder cavity is freed from the combustion products through the exhaust ports opened by the piston, with their direction into the atmosphere through the exhaust manifold, they are blown and filled with fresh charge through the exhaust windows opened by the piston, they pass part of the fresh charge, without interfering with its movement, from the cylinder cavity into the exhaust manifold after the combustion products with the fresh charge filling part of the exhaust manifold, then blocking the cross section of the exhaust manifold is controlled by a slide valve synchronized with the movement of the piston, blocking the movement of combustion products and thus increasing the pressure in the exhaust manifold in front of the slide valve in the direction of gas movement from the cylinder cavity, the fresh charge entering the exhaust manifold displaces the increased gas pressure in front of the slide valve back in the direction of the cylinder and pump a fresh charge from the exhaust manifold blocked by the spool device into the cylinder cavity through open outlets the windows due to the energy of the combustion products, after which they close the purge and exhaust windows with a piston at the beginning of the compression stroke, and in the period before the piston closes the purge windows, temporarily, at least until the piston closes the purge windows, increase the pressure in the region of the purge windows outside the cylinder , thus limiting the release of fresh charge from the cylinder cavity. 2. The method according to claim 1, characterized in that the purge is carried out by supplying a fresh charge to the cylinder cavity from a sub-piston chamber of variable volume in communication with the purge windows through the purge channels, while increasing the pressure in the region of the purge windows outside the cylinder by feeding pumped from the exhaust a fresh charge collector additionally into the sub-piston chamber, in communication with the exhaust manifold by means of a channel with a locking member installed therein. 3. The method according to claim 1, characterized in that the purge is carried out by supplying a fresh charge by the supercharger to the cylinder cavity through the purging windows from a constant-volume purging chamber in communication with the supercharger via an inlet channel with a shut-off element installed in it, while increasing the pressure in the area of the purge windows outside the cylinder by supplying a fresh charge pumped from the exhaust manifold additionally to the purge chamber.

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