RU2744797C1 - Two-stroke two-piston internal combustion engine - Google Patents

Abstract

FIELD: engine building.

SUBSTANCE: invention relates to engine building. A two-stroke two-piston internal combustion engine contains a cylinder head, a cylinder block equipped with purge ports in one of the cylinders, and exhaust ports in the other, pistons moving in said cylinders generally unidirectionally, each of which controls the purge and exhaust, respectively. It also contains a mechanism for converting the reciprocating movement of the pistons into the rotational movement of the crankshaft by means of one common V-shaped connecting rod with two piston heads and pistons pivotally connected thereto. Moreover, the pistons are connected to the piston heads of the connecting rod by means of two piston pins in the form of two-movable hinges, which provide the mechanism with 2 degrees of freedom, and the pistons have the possibility of additional self-oscillating movement.

EFFECT: increased fuel efficiency due to the use of effective direct-flow blowing, improved specific weight and dimensions.

6 cl, 17 dwg

Description

The technical field to which the invention relates

The invention relates to engine building, in particular, to a device for reciprocating internal combustion engines (ICE).

State of the art

In engine building, ICE designs are known, in particular piston ones, in which the processes of air charge intake, compression, expansion (stroke), and exhaust gas discharge are carried out. And only the working stroke is related to the transformation of the chemical energy of the fuel, as a result of its oxidation (combustion), into useful work. The widespread use of electronic controls for such a parameter as the piston stroke is considered to be promising directions in the development of piston engines, as a result of which the compression ratio that is optimal in terms of economy is provided when the engine is operating in any mode [1].

The dominant trend in the automotive engine building is the improvement of the mass and dimensions of the internal combustion engine due to their forcing with the use of controlled turbocharging. This approach allows you to reduce the number of cylinders and / or their dimensions and is called "downsizing". Two-stroke internal combustion engines have significant advantages over four-stroke internal combustion engines in terms of weight and dimensions, and in particular engines with direct-flow blowdown: with oppositely moving pistons (PDP) and two-piston U-type ("uniflow engines") [2].

Also known is a two-stroke piston internal combustion engine and its method of operation [3]. In the specified ICE with PDP, a mechanism with 2 (two) degrees of freedom is used to convert the reciprocating movement of the pistons into the rotational movement of the crankshaft, which makes it possible to implement a method of operation in which the pistons move in the absence of a rigid kinematic connection with the position of the crankshaft and thereby create conditions for the occurrence of self-oscillations of the pistons, which are not transmitted directly to the crankshaft, but generate additional flows of kinetic energy circulating in the moving links of the piston motion conversion mechanism.

The layout and dimensions of an internal combustion engine with a RAP do not always comply with the requirements of the vehicles they are driving. Therefore, it is advisable to transfer the principles and method of operation of the internal combustion engine [3] to engines with direct-flow blowdown, but with a traditional arrangement of cylinders (adjacent to each other) as in a U-type internal combustion engine (“split-single engine”) [4], in which one cylinder is “split »For two with a common combustion chamber.

Engines of this type, with two cylinders (intake and exhaust) and one common crankshaft, differ in the ways of transferring force from the pistons to the crankshaft crank:

a) through two connecting rods and two cranks with angular displacement;

b) through the main and trailed connecting rod and a common crank;

c) through a forked connecting rod and a common crank.

Known two-stroke internal combustion engine [5], in which the connecting rods are on a common crank, and the displacement of the exhaust-intake phases is achieved by displacement of the axes of the cylinders relative to the plane passing through the axis of rotation of the crankshaft. The specified engine is a mechanism with the 1st (one) degree of freedom, which means the presence of a rigid connection between the angle of rotation of the crankshaft (r.c.v.) and the position of each of the pistons and the absence of the possibility of influencing the working process.

Known two-stroke internal combustion engine [6], in which the connecting rods are on a common crank, and the displacement of the exhaust-intake phases is achieved by different lengths of the exhaust and intake connecting rods. The specified engine is a mechanism with the 1st (one) degree of freedom, which means the presence of a rigid connection between the SCC angle. and the position of each of the pistons and the lack of the possibility of influencing the working process.

Known two-stroke internal combustion engine [7], which has one main connecting rod (outlet) and one trailed (inlet). The specified engine is a mechanism with the 1st (one) degree of freedom, which means the presence of a rigid connection between the SCC angle. and the position of each of the pistons and the lack of the possibility of influencing the working process.

Known two-stroke internal combustion engine [8], in which the pistons are connected to the crank by a forked connecting rod, while both pistons are exhaust, because the engine is equipped with a single-flow valve-slotted purge. The specified engine is a mechanism with the 1st (one) degree of freedom, which means the presence of a rigid connection between the SCC angle. and the position of each of the pistons and the lack of the possibility of influencing the working process.

Known two-stroke two-piston internal combustion engine [9], in which the pistons are connected to the crank by a forked connecting rod, it is not stipulated that the pistons have a different design of the piston pins. With regard to a two-piston internal combustion engine with a forked connecting rod, [2] states: "For the possibility of lateral movement of the piston head of the connecting rod, one of the two-piston pins has a special design." It is easy to show that the design of the engine declared in [9] has a 0-th (zero) degree of freedom, which means that the proposed ICE is not a mechanism.

Known two-stroke internal combustion engine [10], in which the pistons are connected to the crank by a forked connecting rod in a shape similar to the connecting rod from [9], while it is argued that to ensure the operability of the mechanism, the distance between the centers of the piston heads of the V-shaped (forked) connecting rod must be variable, and the connecting rod rods themselves must be flexible. The fatigue strength of such a connecting rod should be very high (unlimited), however, it is proposed to make a connecting rod made of aluminum, which makes the performance of a rigid connection between the r.s.c. angle. and the position of each of the pistons and the lack of the possibility of influencing the working process.

Known two-stroke internal combustion engine [7], which has one main connecting rod (outlet) and one trailed (inlet). The specified engine is a mechanism with the 1st (one) degree of freedom, which means the presence of a rigid connection between the SCC angle. and the position of each of the pistons and the lack of the possibility of influencing the working process.

Known two-stroke internal combustion engine [8], in which the pistons are connected to the crank by a forked connecting rod, while both pistons are exhaust, because the engine is equipped with a single-flow valve-slotted purge. The specified engine is a mechanism with the 1st (one) degree of freedom, which means the presence of a rigid connection between the SCC angle. and the position of each of the pistons and the lack of the possibility of influencing the working process.

Known two-stroke two-piston internal combustion engine [9], in which the pistons are connected to the crank by a forked connecting rod, it is not stipulated that the pistons have a different design of the piston pins. With regard to a two-piston internal combustion engine with a forked connecting rod, [2] states: "For the possibility of lateral movement of the piston head of the connecting rod, one of the two-piston pins has a special design." It is easy to show that the design of the engine declared in [9] has a 0-th (zero) degree of freedom, which means that the proposed ICE is not a mechanism.

Known two-stroke internal combustion engine [10], in which the pistons are connected to the crank by a forked connecting rod in a shape similar to the connecting rod from [9], while it is argued that to ensure the operability of the mechanism, the distance between the centers of the piston heads of the V-shaped (forked) connecting rod must be variable, and the connecting rod rods themselves must be flexible. The fatigue strength of such a connecting rod should be very high (unlimited), however, it is proposed to make the connecting rod from aluminum, which makes the performance

p ₅ - the number of single-moving kinematic pairs of the 5th class.

A diagram of such a prototype mechanism is shown in FIG. 1a. Fixed elements: support 0, cylinder block (BC) 3, cylinder head (GC) 4. Moving links: crank 1, connecting rod 2, piston 5, piston 6. Class 5 kinematic pairs: liner-piston friction pair - two, hinges - four.

n = 4 is the number of moving links;

p ₅ = 6 - the number of one-way kinematic pairs of the 5th class.

w = 3 * 4 - 2 * 6 = 0

This result corresponds to the situation with the internal combustion engine from [9].

In order to reflect the flexibility factor of the connecting rod rods in the ICE of the prototype, it is enough to add a fictitious (extensible) link and an additional hinge to the scheme.

FIG. 1b shows the replacement of the left rod of the connecting rod with a combination of two links - a curved main and a fictitious one:

n = 4 + 1 is the number of moving links;

p ₅ = 6 + 1 - the number of one-way kinematic pairs of the 5th class.

w = 3 * 5 - 2 * 7 = 1

Thus, the prototype is a mechanism with the 1st (one) degree of freedom.

FIG. 1c shows the possibility of modifying the scheme "b" in order to change the number of degrees of freedom of the mechanism to 2 (two). For this, links 7 and 8 are introduced (bearing in mind that these can be eccentrics) with a length equal to the eccentricity e and two hinges.

n = 4 + 2 is the number of moving links;

p ₅ = 6 + 2 - the number of one-way kinematic pairs of the 5th class.

w = 3 * 6 - 2 * 8 = 2

The number of degrees of freedom of the flat mechanism according to the "c" scheme is equal to 2 (two). As a piston pin, a structural element with one connecting rod (smaller diameter) neck and two piston ones can be used, one of which, or both (as in Fig. 2) are split (e 'in e' ').

In the presence of one more, redundant in comparison with traditional internal combustion engines, degrees of freedom, each fixed position of the crankshaft will no longer correspond to a strictly defined position of the pistons; it will be set dynamically based on the processes occurring in the above-piston space.

Brief Description of Drawings

FIG. 1 shows images related to the scheme of the mechanism of the internal combustion engine of the prototype (Fig. 1a and 1b) and the proposed internal combustion engine (Fig. 1c).

FIG. 2 shows the images of the piston pin as a two-piece hinge one-piece (Fig. 2a) and split (Fig. 2b).

FIG. 3 shows a transverse (through the axes of the cylinders) section of the proposed internal combustion engine.

FIG. 4 is an enlarged view of the connecting rod piston head to the exhaust piston.

FIG. 5 shows a diagram of the swirling movement of the purge air.

FIG. 6 shows a diagram of the opening phases of the gas exchange organs (windows).

FIG. 7 shows the assumed dependence of the deviation of the axis of symmetry of the connecting rod under the influence of oscillation of the pistons.

FIG. 8 shows the dependence of the speeds of the pistons and the connecting rod on the angle of the c.c.v.

FIG. 9 shows the dependence of the specific kinetic energy of the pistons and the connecting rod on the f.c.h. angle.

FIG. 10 shows the dependence of the power of the inertial forces of the pistons and connecting rod on the r.c.v. angle.

FIG. 11 shows the effect of piston oscillations on the indicator diagrams of the internal combustion engine.

DETAILED DESCRIPTION The invention can be carried out in the form of the apparatus shown in FIG. 3. The implementation of the invention involves the use of two, moving mainly unidirectionally, pistons 5 and 6, connected with a fork rod 2 by means of double-hinged piston pins 7 and 8. An additional, 2nd degree of freedom of the mechanism for converting the reciprocating motion of pistons 5 and 6 into rotational the movement of the neck of the crank 1 is provided by two double-pivot pins 7 and 8 (double-movable hinges) formed by the pin 7 'and liners 7' '(for the piston 5) as in FIG. 4. Unlike traditional pistons, in which the piston pin has a tight fit, in the piston 5 (6), the liners 7 '' make a reciprocating movement, so the hole in the piston must be made with a bushing, for example, a bronze one. The small eccentricity e between the connecting rod axis of the pin 7 'and the piston axis of the liner 7' 'allows the connecting rod head to be shifted horizontally at a maximum of 2e, however, the actual shifting of the connecting rod head turns out to be much less, which provides a possible rocking motion of the connecting rod 2 relative to the crank axis 1 with a swing about 1 degree. Thus, the oscillatory movements of the forked connecting rod 2 at any fixed position of the crank 1 are capable of causing the oscillatory movements of the pistons 5 and 6, which, even during the rotation of the crank 1, will be superimposed on their main reciprocating movements in the cylinder block 3.

The operation of the described device is carried out as follows.

In the position of the crank 1 at the upper volumetric dead center (BOMT or 180 degrees, r.c.), but not TDC of pistons 5 and 6 (as in Fig. 3), the air charge is in a compressed state and has already been produced in it ( with some advance to PTO) fuel injection through a nozzle (not shown) oriented towards the combustion chamber 13. The combustion chamber 13 of a simple semi-ellipsoid shape can have a ceramic coating, which will not only reduce heat loss to the cylinder head 4, but also improve volumetric film evaporation fuel, and hence the completeness of its combustion. When the crank rotates (clockwise) after passing the PTO, a working stroke begins with the performance of useful work, in which the piston 5 leads the piston 6 in its movement to its bottom dead center (BDC). The piston 5 reaches the upper edge of the exhaust ports 9, while the purge ports 10 are covered by a piston skirt 6. Subsequently, the free release of exhaust gases through the exhaust ports 9 into the exhaust manifold 11 begins, and the piston 6 reaches the upper edge of the purge ports 10. Further, through the purge ports 10 air entering the space above the piston displaces the exhaust gases through the outlet ports 9 into the exhaust manifold 11 - the forced release of exhaust gases begins with their replacement with purge air, i.e. purge process. When the crank 1 rotates, the exhaust ports 9 are closed first and air is pressurized. After closing the scavenging ports 10, the above-piston space is closed again and the process of compressing the air charge begins, until the PTO is reached. The two-stroke cycle ends.

The asymmetry of the laws of motion of the pistons relative to the PTO leads to the fact that in the area of the PTO the inertial forces act on the right and left pistons in different directions: one accelerates, the other slows down. Therefore, even if the gas forces applied to the piston crowns are equal, an asymmetry of the forces applied to the right and left piston heads of the connecting rod occurs, which is the incentive for their mutual deviation and, in particular, vibrations of the connecting rod 2 itself relative to the crank axis 1. If the movement of the connecting rod 2 in the absence of oscillations, call it "equilibrium" (analogy with a pendulum), then this movement will correspond to the movement of a segment with the length of the connecting rod lying on the axis of its symmetry. In this case, the end of this segment - the "midpoint" - will move along a vertical straight line passing through the axis of rotation of the crankshaft, as in the case of a central crank mechanism.

The main consequence of the presence of the 2nd degree of freedom is that the fixed position of the crank 1 does not correspond to any fixed position of the pistons 5 and 6, like any other traditional piston internal combustion engine. In this case, self-oscillations of the pistons arise, which generate additional flows of kinetic energy in the moving links of the mechanism [3].

An example of possible implementations of the proposed internal combustion engine.

Initial data:

1. Power - 50 kW

2. Frequency of rotation of c.v. - 4000 rpm

3. Piston stroke - 92 mm

4. Diameter of cylinders - 80 mm

5. Crank radius - 45 mm

6. The length of the connecting rod (along the axes) - 250 mm

7. The camber angle of the connecting rod - 28 degrees.

8. Eccentricity of the piston pin - 7 mm

9. Compression ratio (geometric) - 20

10. Compression ratio (valid) - 16

11. Purge air pressure - 0.12 MPa

12. Excess air ratio - 1.7

The claimed constructive scheme does not impose restrictions on the type of internal combustion engine, i.e. on the method of mixture formation and the method of ignition, but in the future the diesel version of the internal combustion engine is considered.

To ensure the compression ratio ε _d = 16 and higher, it is necessary to minimize the volume of the combustion chamber. On the other hand, it is necessary to provide a minimum resistance to gas flow from one cylinder (inlet) to another (outlet) during purging. The channel 14, made in the BC, is oriented in the direction of the tangent to the circles at which the maximum circumferential velocity of the vortex air movement, and the combustion chamber 13 is located above the specified channel and is oriented along its axis, as in Fig. five.

The inventive design scheme of the internal combustion engine naturally provides a phase shift (24 ° c.c.v.) of the dependences of the piston stroke on the sc.c.v. angle, which is favorable for the implementation of direct-flow blowing in the process of gas exchange. As seen in FIG. 6 with a total duration of gas exchange of 132 ° sc.c.v., the purge period (overlapping of the phases of opening of the gas exchange organs) accounts for 72 ° sc.c.v.

The operability of the claimed ICE structural scheme can only be proved by calculation. The calculation of the internal combustion engine is a complex mathematical problem, therefore, simplifying assumptions are made to solve it:

a) the intensity of self-oscillations of the pistons is proportional to the power of heat release dQ / dt (according to the model of II Vibe with m = 0.55 and ϕ _z = 65 ° SCH) [3];

b) the movements of the links are determined by the superposition of "equilibrium" movements, i.e. in the absence of vibrations and movements "caused" by vibrations of the connecting rod according to a given law.

"Equilibrium" movement of the links is obtained by imposing restrictions on the movement of the "midpoint" of the connecting rod strictly in a straight line, conventionally reducing the degree of freedom of the mechanism by 1 (one).

FIG. 7 shows the assumed relationship between the deviation of the connecting rod axis dG _{a / k} and the rate of heat release K * dQ / dt, with a maximum deviation from the "equilibrium" position equal to 0.5 °. The possible phase shift of the dependences (lag) is of the order of 10 ° sc.c. Such vibrations of the connecting rod are "caused" by vibrations of the pistons, the speed dependences of which are shown in FIG. 8: a) "balanced" movements (b / c); b) in the presence of self-oscillations (a / c).

The movements of the pistons and connecting rod occur with a change in their kinetic energy, while the kinetic energy of the pistons is proportional to their mass (0.6 kg each), and the kinetic energy of the connecting rod is proportional to its moment of inertia (0.0325 kg * m ² ). The kinetic energy of the connecting rod from movement along the axes of the cylinders is not taken into account. The dependences of the specific (relative to the piston mass) kinetic energy are shown in Fig. 9: a) "balanced"movements; b) in the presence of self-oscillations.

The change in the kinetic energy of the links is associated with the power of inertial forces, positive with a decrease in kinetic energy and negative with an increase. FIG. 10 shows the dependences of the power of the inertial forces circulating in the links of the ICE mechanism in connection with a change in their kinetic energy. As seen in FIG. 10a, the power values are comparable to the cylinder power, as in traditional internal combustion engines. However, as seen in FIG. 106, in order to bring the thermomechanical system out of "equilibrium" with the expected amplitude and frequency (5 times the rotational speed of the r.v.), it is necessary to apply an order of magnitude greater power. There is no source of such power, therefore, the inertia of the most "energy-intensive" link - the connecting rod naturally prevents an increase in the amplitude and frequency of oscillations of the ICE links with two degrees of freedom. Thus, real vibrations of the links of the internal combustion engine mechanism will occur with a lower amplitude and frequency equal to the crankshaft rotation frequency, therefore, they should be associated with an additional shift of the connecting rod at the moments of the mechanism transition through the TDC (BDC). As mentioned earlier, the TDC of the pistons are spaced 12 ° sc.c. relative to the PTO (180 ° sc.c.). Such a shift of the connecting rod in the area of the PTO can be called "trigger", and the assumed law of variation of the deflection of the connecting rod dG _{trigger is} shown in Fig. 7. The calculation shows that the "trigger" shift of the connecting rod with an amplitude of 0.1 ° occurs at the power of inertia forces of the same order as the cylinder power of the internal combustion engine.

FIG. 11 shows, in the form of an indicator diagram, the influence of piston oscillations on the in-cylinder processes. Taking into account the self-oscillations (a / c) of the pistons leads to a slight increase in the average indicator pressure from 0.96 MPa to 0.97 MPa, however, it helps to reduce the rigidity of the engine by 11%.

Thus, the proposed engine provides the achievement of the technical effect, which consists in increasing the fuel efficiency through the use of effective direct-flow blowing, improving the specific weight and dimensions. The engine can be implemented using means known in the art. Therefore, the proposed engine has industrial applicability.

Since the preferred embodiments of the present invention will be obvious to those skilled in the art of propulsion engineering, and the invention itself is susceptible of many variations, modifications and changes in detail, it is intended that all material contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in restrictive sense.

Sources of information

1. Design and calculation of piston engines: textbook for universities / N.D. Chainov, A.N. Krasnokutsky, L.L. Myagkov; ed. N. D. Chainova. - Moscow: Publishing house of MSTU im. N.E. Bauman, 2018 .-- 536 p.

2. Combined two-stroke engines. Orlin A.S., Krugloye M.G., M., "Mechanical Engineering", 1968, 576 p.

3. Pat. RU 2729562, 2020.

4.https://en.wikipedia.org/wiki/Split-single_engine.

5. Pat. US 1476305, 1923.

6. Pat. US 2048243, 1936.

7. Pat. US 2443502, 1948.

8. Pat. US 2168096, 1939.

9. Pat. US 4079705, 1978.

10. Pat. US 5758611, 1998.

Claims (6)

1. A two-stroke two-piston internal combustion engine containing a cylinder head, a cylinder block equipped with purge ports in one of the cylinders and exhaust ports in the other, pistons moving in these cylinders mainly unidirectionally, each of which controls purge and exhaust, respectively, a mechanism for converting the reciprocating movement of the pistons into the rotational movement of the crankshaft by means of one common V-shaped connecting rod with two piston heads and pistons pivotally connected to it, characterized in that the pistons are connected to the piston heads of the connecting rod by means of two piston pins in the form of two-movable hinges providing the mechanism 2 degrees of freedom, and the pistons have the possibility of additional self-oscillating motion. 2. A two-stroke two-piston internal combustion engine according to claim 1, characterized in that both two-moving joints are made in the form of a two-moving rotational-rotational kinematic pair of the “joint-joint” type, allowing the piston pin to rotate simultaneously relative to its two axes, piston and connecting rod, and arc displacement of the center of the piston head of the connecting rod relative to the piston axis of the piston pin. 3. Two-stroke two-piston internal combustion engine according to claim 2, characterized in that the piston pins are made in the form of an eccentric with two axes - piston and connecting rod, and three journals - one middle, connecting rod and two extreme, piston, one of which or both are detachable. 4. Two-stroke two-piston internal combustion engine according to claim 1, characterized in that the cylinder block on the side adjacent to the cylinder head has an open channel connecting the cylinders, the axis of which is simultaneously tangent to two circles, on which the maximum circumferential velocity of the vortex air movement in cylinders. 5. A two-stroke two-piston internal combustion engine according to claim 1, characterized in that the cylinder head on the side adjacent to the cylinder block has an open combustion chamber of a simple semi-ellipsoidal shape, the major axis of which is collinear with the channel axis according to claim 4 in order to sum their transverse cross-sections and minimizing the resistance to the flow of purge air. 6. The two-stroke two-piston internal combustion engine of claim 1, wherein the cylinder head is air-cooled with a finned outer surface, and the combustion chamber of claim 5 has a ceramic coating with low thermal conductivity to minimize heat loss through the cylinder head.

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