RU2206757C2 - Two-stroke internal combustion engine - Google Patents

Abstract

FIELD: mechanical engineering; internal combustion engines. SUBSTANCE: proposed engine contains cylinder, intake and exhaust valves, piston and driven supercharger. Guide shield separating intake valve from exhaust valve is secured on intake valve. According to invention, guide shield is located in cylinder and is made in form of plate with flange. Shield is provided with holes in plate pointed to side of piston. Plate can be made in form of half of circle of diameter smaller than diameter of cylinder. Flange is pointed to side of cylinder cover, being made of height exceeding value of opening of intake valve. Cover is provided with slot of shape and dimensions corresponding to flange. EFFECT: improved efficiency owing to excess of degree of expansion over degree of compression, without impairing scavenging and charging of engine. 2 cl, 8 dwg

Description

 The invention relates to two-stroke reciprocating internal combustion engines with continued expansion in the main cylinders and can be used in transport and other industries.

 Two-stroke engines usually have a crank chamber purge, that is, the cylinder is purged through windows on the side of the cylinder by suction, compression and injection of the mixture in the crank chamber under the engine piston and supplying the mixture to the engine cylinder through the inlet windows. (I. Ya. Raikov, G.N. Rytvinsky. Design of automobile and tractor engines. - M.: Higher School, 1986. - 112-113 p., Fig.3.5g).

 The main drawback of two-stroke engines with a crank-chamber blowdown is the increased content of harmful products of oil combustion in the exhaust gases, since oil for lubricating the engine is mixed into the fuel.

 In conventional engines, the compression ratio is close to the expansion ratio and the gas pressure at the beginning of the release from the cylinder is several times higher than atmospheric pressure, that is, the gas energy at the beginning of the release is quite high and this energy is not used.

 Numerous engine designs are known in which ways to utilize gas pressure at the end of expansion have been sought by increasing the expansion ratio compared to the compression ratio.

 For example, a four-stroke engine with continued expansion in the main cylinders is known, in which the intake valve closes at half stroke, that is, the expansion ratio is 2 times the compression ratio (J. Matskerle. Modern economical car. - M.: Mashinostroenie, 1987. - 110 s.).

 The efficiency of this engine at maximum load is higher than the efficiency of a conventional engine with the same compression ratio, but its efficiency will decrease at partial loads twice as fast as in a conventional engine. This is because the mechanical loss of the engine is mainly determined by the size of the engine and the speed of rotation of the engine shaft and little depends on the gas pressure in the cylinders. The mechanical losses per unit mass of gas will be twice as much, since the gas mass in the engine is half that of a conventional engine of the same size. With a load of less than 50%, the efficiency of this engine will be lower than the efficiency of a conventional engine, but it will have twice the mass and volume of cylinders than a conventional engine of the same power.

 A two-stroke internal combustion engine is known, comprising cylinders having inlet windows located on the side of the cylinder near the bottom dead center, caps covering the cylinders and equipped with exhaust valves, pistons reciprocating between the bottom and top dead centers located in the cylinders and connected by a motion conversion mechanism with a shaft, a fuel supply device, a valve control mechanism, a purge device, for example a drive air atel connected to the inlet conduit with inlet ports (Yu Matskerle modern economical car M .: Engineering, 1987. -.. 221 pp.).

 There is no crank-chamber purge in this engine, no oil is added to the fuel and there is no high content of harmful products of oil combustion in the exhaust gases.

 The disadvantages of these two-stroke engines is that the expansion ratio is close to the compression ratio and at the beginning of the exhaust the exhaust gases have a pressure of 0.4-0.5 MPa, that is, they have significant energy that is not used.

 To purge the cylinder through the inlet windows, it is necessary to supply a volume of air of at least a cylinder volume per cycle. To ensure high-quality purge of the cylinder with low energy consumption for purging, it is necessary to use up to 40% of the cycle time for purging and inlet windows with a height of 25-30% of the piston stroke are needed. The exhaust valve should then open at 40-50% of the piston stroke from the BDC. That is, up to 30-40% of the cylinder volume is not used for gas expansion during the stroke and this volume is called the lost volume.

 But if you make inlet windows of lower height, that is, reduce the proportion of time spent on purging, the energy consumption for purging will increase.

 The technical result of the invention is to increase the degree of expansion in the cylinders in comparison with the degree of compression in the cylinders without increasing the specific gravity and volume of the engine and without deteriorating the purge quality, by reducing the proportion of the lost cylinder volume and increasing the specific work produced by the gas with continued expansion.

 To achieve this technical result, a two-stroke internal combustion engine comprises at least one cylinder, a cylinder cover, an intake device, an exhaust device, for example, a valve located in the cover, a piston reciprocating between the lower and upper dead points located in the cylinder and connected a motion conversion mechanism with a shaft, a fuel supply device, a valve control mechanism, a purge device, for example a supercharger connected inlet rapid pipeline with inlet devices.

 Distinctive features of the proposed engine is that the inlet device is made in the form of an inlet valve installed in the cylinder cover and connected to the valve control mechanism, and the engine has a guide plate attached to the inlet valve located in the cylinder and encloses the inlet valve from the exhaust valve.

 Additionally, the proposed engine is characterized in that the valve control mechanism is configured to open the exhaust valve when the engine piston does not reach the BDC at 5-10% of the piston stroke and close the exhaust valve when the piston does not reach the TDC at 30-50% of the piston stroke , and opening the intake valve at the BDC and closing the intake valve 2-5% of the piston stroke after closing the exhaust valve.

 These additional features characterize some possible forms of implementation of the invention.

 Additionally, the proposed engine is characterized in that the guide plate is a half-circle plate with a diameter of 1-3 mm less than the cylinder diameter with a side towards the cylinder cover located along the plate diameter, higher than the intake valve opening height, and the cylinder cover has a groove, in shape and size corresponding to the side.

 Additionally, the proposed engine is characterized in that the guide plate has holes on the entire surface, except for the edge, with a diameter close to the thickness of the shield, and the holes are made in the form of diffusers, sockets directed towards the piston, and the total area of the holes is more than half the area of the shield.

 These additional features characterize one of the possible versions of the engine parts given in the independent claim at the level of functional features.

 The engine operates as follows. When the engine piston is in the BDC, the intake valve and exhaust valve are open and air is supplied by the supercharger through the intake valve, and the exhaust gases are removed from the cylinder through the exhaust valve. The piston moves to TDC, and when 30-50% of the piston stroke remains at TDC, the exhaust valve closes and air continues to flow through the intake valve, i.e. recharging takes place. After 2-5% of the piston stroke, the inlet valve closes and compression begins in the cylinder. At the beginning of compression, the nozzle injects fuel and a combustible mixture is formed. When the piston approaches TDC, the spark plug ignites the mixture, combustion of the fuel occurs, and the temperature and pressure of the gases in the cylinder increase. The piston passes TDC and, under gas pressure, moves to BDC, that is, a working stroke occurs. When 5-10% of the piston stroke remains before BDC, the exhaust valve opens and exhaust gas begins to discharge. The gas pressure at the end of the expansion of 0.15-0.2 MPa and by the time the intake valve is opened, it will decrease to the pressure at the pressure head of the supercharger. The intake valve will open in the BDC, air will flow into the cylinder from the blower head. Then everything repeats.

 All cycle processes occur in one revolution of the motor shaft, that is, in two cycles. As in the prototype, at least 40% of the cycle time will be used for purging, only the purging time is shifted along the shaft rotation by 40-70 degrees and the energy consumption for purging will not be higher than that of the prototype.

 Unlike the prototype, inlet valves are not needed due to the presence of an inlet valve. Due to the low pressure at the end of the expansion, the exhaust valve can be opened directly when the piston approaches the BDC. This will allow for the expansion of gases in 1.3-1.4 times the volume of the cylinder than the prototype.

 In this engine, the mixture fills 30-50% of the cylinder volume before compression, and up to 95% of the cylinder volume is used to expand the combustion products. With the same compression ratios, the expansion ratio in the engine cylinders will be 2-3 times greater than the expansion ratio in the prototype cylinders, and the fuel energy will be used more fully.

 The guide plate protects the air flow entering through the inlet valve at a speed of 50-100 meters per second from directly entering the exhaust valve and prevents the mixing of air jets with exhaust gases. In the cavity between the cylinder cover and the guide plate, the air jets are decelerated and then the air enters the diffusers at a speed of 20-30 meters per second, and leaves the diffusers in a continuous stream, occupying half the cylinder section at a speed of 10-20 meters per second. This stream will mix little with the exhaust gases and cleaning the cylinder of residual gases will be no worse than that of the prototype. It will be possible to supply for purging 1.5-2 times less air.

 The proposed engine is illustrated by the drawings shown in FIG. 1-8.

 Figure 1 shows a diagram of the engine during air inlet into the cylinder through the intake valve and exhaust gas from the cylinder through the exhaust valve, the piston in the BDC.

 In FIG. 2 shows the engine cylinder while continuing to inlet air through the intake valve, i.e. recharging the cylinder.

 Figure 3 shows the cylinder of the engine during compression of the air with simultaneous injection of fuel.

 Figure 4 shows the cylinder of the engine with the piston in TDC and the combustion of fuel in the cylinder.

 5 shows an engine cylinder during a stroke.

 In FIG. Figure 6 shows the engine cylinder during the start of exhaust through the exhaust valve.

 7 shows an enlarged part of a cylinder.

 On Fig shows a diagram of the valve timing.

 The two-stroke internal combustion engine (Fig. 1) contains a cylinder 1, a cover 2 of a cylinder 1 with an inlet valve 3 and an exhaust valve 4, a piston 5 reciprocating and connected by a connecting rod 6 to the shaft 7, the nozzle 8, the spark plug 9, the mechanism control 10 of the valve 3 and 4, a supercharger 11 connected to the inlet pipe 12 to the intake valve chamber 3. There is an exhaust pipe 13 connected to the exhaust valve chamber 4. There is a throttle valve 14 mounted on the suction side of the supercharger 11. There is a guide shield to 15 attached to the intake valve 3.

 The engine operates as follows. When the engine piston 5 is in the BDC, the intake valve 3 and the exhaust valve 4 are open and air is supplied through the intake valve 3 by the supercharger 11, and the exhaust gases leave the cylinder 1 through the exhaust valve 4 (shown in FIG. 1). The piston 5 moves to the TDC, and when 30-50% of the stroke of the piston 5 remains at the TDC, the exhaust valve 4 closes, and air enters through the intake valve 3 and the cylinder 1 is recharged (shown in FIG. 2). After 2-5% of the piston stroke 5 after closing the exhaust valve 4, the intake valve 3 will close and compression will begin in cylinder 1. At the beginning of the compression, the nozzle 8 injects fuel and a combustible mixture is formed in the cylinder 1 (shown in FIG. 3). When the piston 5 approaches TDC, the spark plug 9 ignites the mixture, combustion of the fuel occurs, and the temperature and pressure of the gases in the cylinder 1 increase (shown in Fig. 4). The piston 5 passes through the TDC and, under gas pressure, moves to the BDC, that is, a stroke occurs (shown in FIG. 5). When 5-10% of the stroke of the piston 5 remains before BDC, the exhaust valves 4 are opened and the exhaust gas begins to discharge (shown in Fig.6). The gas pressure at the end of the expansion of 0.12-0.2 MPa and by the time the intake valve 3 opens, it will decrease to the pressure at the pressure head of the blower 12. The intake valve 3 will open at the BDC, air will begin to flow into cylinder 1. After the piston 5 passes through the BDC engine, everything repeats.

 On Fig shows a gas distribution phase diagram in which at least 40% of the cycle time is spent on gas exchange, only the intake and exhaust times are shifted along the shaft rotation by 40-70 degrees and the energy consumption for purging will not be higher than that of the prototype.

 When the engine is operating at partial load, the throttle valve 14 is covered. In the forced idle mode, the nozzle 8 is turned off.

 This engine can be either diesel or forced ignition. Forced ignition engines can be gasoline injected or carbureted.

 The proposed engine provides a new technical result. That is, the proposed engine in comparison with the prototype has a 2-3 times greater overall degree of expansion in the engine cylinders, and this will allow more fully use the energy of combustion of fuel. Moreover, this result was achieved without compromising the quality of gas exchange and increasing the energy consumption for purging.

 This technical result was obtained due to the lack of inlet windows. Compared to the push-pull prototype, a 1.4-1.5 times larger cylinder volume can be used to expand the gas. And in comparison with a four-stroke engine, due to the two-stroke cycle, the cylinder volume doubled is used for continued expansion without increasing the size of the engine and reducing its mechanical efficiency. In addition, as the degree of expansion increases, the gas does more work.

 Due to the increase in gas work with continued expansion and the increase in the volume of the cylinder used for expansion, the specific power of the proposed engine will be greater and the mechanical losses less than that of the push-pull prototype, up to an expansion ratio of 1.5 times greater than the compression ratio. Compared to a four-stroke engine, the specific power of the proposed engine will be higher, and mechanical losses less, up to a degree of expansion 3 times greater than the compression ratio.

 Calculations show that the efficiency of the proposed engine due to continued expansion in the engine cylinders will be higher than that of the prototype and the proposed engine will provide some fuel savings.

Claims (5)

 1. A two-stroke internal combustion engine comprising at least one cylinder, a cylinder cover, an intake and exhaust device, for example, valves located in the cylinder cover, a valve control mechanism, a piston located in the cylinder, reciprocating between the lower and upper dead points and connected by a motion conversion mechanism to the shaft, a fuel supply device, a purge device, for example a drive supercharger, connected by an inlet pipe to the inlet device and the guide plate attached to the intake valve and the inlet valve is fenced off from the exhaust valve, characterized in that the guide plate is located in the cylinder and wherein the plate has openings.  2. The two-stroke engine according to claim 1, characterized in that the valve control mechanism is configured to open the exhaust valve when the engine piston does not reach bottom dead center by 5-10% of the piston stroke and close the exhaust valve when the piston is 30- 50% of the piston stroke does not reach top dead center, and opening the intake valve at bottom dead center and closing the intake valve 2-5% of the piston stroke after closing the exhaust valve.  3. The two-stroke engine according to claim 1, characterized in that the guide plate is a plate made in the form of a half circle with a diameter smaller than the diameter of the cylinder, and has a side directed towards the cylinder cover and made with a height greater than the opening of the intake valve, and the lid has a groove corresponding in shape and size to the side.  4. The two-stroke engine according to claim 1, characterized in that the diameter of the plate is less than the diameter of the cylinder by 1-3 mm.  5. The two-stroke engine according to claim 1, characterized in that the holes in the guide plate are made over the entire surface of the plate, except for the side, have a diameter close to the thickness of the shield, and are made in the form of diffusers, sockets directed towards the piston, and the total area of the holes more than half the area of the shield.

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