RU2784514C1 - Two-stroke reciprocating internal combustion engine with variable compression and expansion ratios - Google Patents

Abstract

FIELD: internal combustion engines.

SUBSTANCE: invention can be used in internal combustion engines. A two-stroke reciprocating internal combustion engine contains a block of cylinders (16) equipped with purge and exhaust ports (12) and (11), pistons (7) and (8) moving in cylinders (16) in opposite directions. Pistons (7) and (8) control purge and exhaust respectively. The mechanism for converting the reciprocating motion of the pistons (7) and (8) into the rotational motion of the crankshaft (1) is carried out by means of one common connecting rod (2) and pivotally connected through the rods (5) and (6) with each of the pistons (7) and (8) two rocker arms (3) and (4). Rocker arms (3) and (4) swing on two-movable hinges (9) and (10) with fixed centers of rotation. One of the hinges (9) is driven to change the phase angle of the hinge relative to the crank (1) to change the compression ratio and the expansion ratio.

EFFECT: increasing fuel efficiency, reducing weight and size indicators.

8 cl, 13 dwg

Description

The field of technology to which the invention belongs

The invention relates to the field of engine building, in particular, to the arrangement of reciprocating internal combustion engines (ICE).

State of the art

The ICE cycle is determined by the number of strokes that the engine piston makes to complete one working cycle, and in the case of using a crank mechanism, a two-stroke engine performs one revolution of the crankshaft, and a four-stroke engine performs two revolutions. “Because the number of duty cycles is more than 2 times, the expected increase in power of a two-stroke engine is 2 times higher. In reality, the power of a two-stroke engine increases by approximately 1.5 ... 1.7 times due to the loss of part of the working volume, the deterioration of cleaning and filling, as well as the power consumption for actuating the scavenge pump. [one].

In connection with the intensive development of hybrid power plants for road transport, internal combustion engines are taking on the role of an auxiliary source of mechanical energy used directly for transmission to a transmission or to drive an electric generator. This circumstance puts forward an additional requirement for improving the weight and dimensions of the internal combustion engine. The best weight and size indicators are 2-stroke internal combustion engines and, in particular, internal combustion engines with oppositely moving pistons (PDP / “opposed piston engine”). A review of the designs of such internal combustion engines is presented in [2]. The most advanced aircraft engine Junkers Jumo-207 with PDP, produced since 1938, had a specific power value of 42 kW / l. Currently, interest is returning to engines with PDP: aviation diesel "Gemini-100" (S / D = 2 × 72/69) with a specific power of 46 kW / l [3]; diesel car Ford F-150 (S/D=2×88.5/80) with a specific power of 73 kW/l [4]. These engines with PDP have a design with two crankshafts connected by a gear train, which sets a misalignment of the crankshafts fixed in terms of the angle of rotation. By changing the angular mismatch of the crankshafts, it is possible to change both the valve timing and the compression ratio, however, the mismatch device must pass through itself up to half of the engine power, which will make such a device inertial and energy-intensive.

Known ICE with PDP [5], in which the mechanism for converting the reciprocating motion of the pistons contains two rocker arms and one crankshaft. The design feature was that there was one working stroke per revolution of the crankshaft, but the engine remained four-stroke, because. each stroke occurred exactly one quarter of a revolution of the crankshaft. In this internal combustion engine, for the first time, the principle of exceeding the degree of expansion over the degree of compression was implemented, which was later transformed into the principle of the Atkinson-Miller cycle in engines with over-expansion (“over-expanshion”).

Known ICE with PDP [6], in which the mechanism for converting the reciprocating motion of the pistons contains two rocker arms and one crankshaft. A design feature is that the engine pistons are connected to the pistons of the air compressor, which provides blowing, which additionally eliminates the occurrence of a side pressure force on the cylinder walls. To pair the rocker arm with the piston, a kinematic pair of the “hinge-slider” type was used. The necks of the hinges, on which the yokes swing, are connected by a stress member made of high-strength steel, which compensates for counter loads, reduces the transfer of loads to the engine housing and makes it possible to make it from light alloys. The disadvantages of this internal combustion engine include the complexity of the design and the impossibility of influencing the workflow.

Known ICE with PDP [7], in which the mechanism for converting the reciprocating motion of the pistons contains two rocker arms and one crankshaft. A design feature is the placement of rocker arms on eccentrics, which can be rotated by a mechanical drive controlled by a computer. The design of the internal combustion engine allows you to change the compression ratio in automatic mode in accordance with the load. The disadvantages of the design of the specified internal combustion engine should include the limited impact on the work process only through a change in the compression ratio.

Known ICE with PDP [8], in which the mechanism for converting the reciprocating motion of the pistons contains two rocker arms and one crankshaft. The design feature is that the mechanism has two degrees of freedom. In the presence of one more degree of freedom, which is redundant compared to traditional internal combustion engines, 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 taking place in the over-piston space.

It is shown that using the mechanism of action on the swing centers of the rocker arms on two-movable hinges, it is possible to change the degree of compression and the degree of expansion within a wide range. In particular, we mean the version of the internal combustion engine, when both two-moving hinges are made in the form of a two-moving rotational-rotational kinematic pair of the "hinge-hinge" type, which simultaneously with the rotation of the rocker arm rotates (along the arc) displacement of its center of swing relative to the fixed center of rotation of the hinge.

Specified in [8] the engine according to the set of features closest to the set of essential features of the invention can be selected as a prototype.

The aim of the invention is to increase the efficiency of the internal combustion engine, in which, through the use of a mechanism for changing the compression ratio and expansion ratio, it becomes possible to promptly and optimally adjust the working process, and hence achieve increased fuel efficiency and reliability of the internal combustion engine.

Disclosure of invention

This goal is achieved by the fact that in a known two-stroke piston internal combustion engine containing a cylinder block equipped with purge and exhaust ports, pistons moving in these cylinders in opposite directions, each of which controls purge and exhaust, respectively, a mechanism for converting reciprocating motion pistons into rotational motion of the crankshaft by means of one common connecting rod and two rocker arms articulated through the rod with each of the pistons, the rocker arms swing on two-movable joints with fixed centers of rotation, while one of the joints is driven into rotation with the possibility of changing the phase angle of the position of the hinge relative to the crankshaft crank shaft to change the compression ratio and expansion ratio.

On FIG. 1a is a prototype diagram, from which it can be seen that the crank 1, connecting rod 2, rocker arms 3 and 4, rods 5 and 6, pistons 7 and 8, hinges (eccentricity) 9 and 10 are a set of ten (n=10) links connected 12 (twelve) hinges and 2 (two) sliding pairs (piston-cylinder). Thus, there are 14 kinematic pairs of the 5th class (p ₅ =14). Using the A.P. Malyshev for the number of degrees of freedom of a flat mechanism gives the result:

w=3n-2p ₅ =3*10-2*14=2.

The imposition of a connection (rotation) between the crank 1 and the two-movable hinge 9 means the addition of a virtual link v (as in Fig. 1b) with two hinges at the ends. Such a mechanism has n=10+1=11 and p ₅ =14+2=16. Using the A.P. Malyshev for the number of degrees of freedom of a flat mechanism gives the result:

n=11 - number of moving links;

p ₅ =16 - the number of single-moving kinematic pairs of the 5th class;

w=3*11-2*16=1

Thus, adding a connection between the crankshaft and the two-moving joint makes the joint 9 “single-movable” and translates the original mechanism (prototype) into a mechanism with the 1st degree of freedom, in which each position of the crank corresponds to a strictly defined position of all links, and hence the pistons. In the break of the link v, a phase regulator (variator) is provided, which only “determines” (associated or counter rotation) the connection of the crank 1 with the hinge 9, but does not change it in essence.

Brief description of the drawings

On FIG. 1 shows images related to the scheme of the ICE mechanism of the prototype (Fig. 1a) and the proposed ICE (Fig. 1b).

On FIG. Figure 2 shows images of double-moving hinges of the rocker arms of the exhaust (Fig. 2a) and purge (Fig. 2b) pistons.

On FIG. 3 shows a longitudinal (through the axis of the cylinders) section of the proposed internal combustion engine. Auxiliary mechanisms and units are not shown.

On FIG. 4 shows the kinematic diagrams of a mechanical phase regulator of direct (Fig. 4a) and reverse (Fig. 4b) action.

On FIG. 5 shows the dependence of the change in the (relative) volume of the above-piston space at VDC (volumetric top dead center) and the degree of compression/expansion on the phase of rotation of the joint.

On FIG. 6 shows the dependence of the change in the total stroke of the pistons on the angle of c.c.v. for the proposed and traditional ICE.

On FIG. 7 shows the dependence of the current degree of expansion on the angle of the c.v. for the proposed and traditional ICE.

On FIG. 8 shows the change in the purge / exhaust phases from the compression ratio for the traditional and proposed internal combustion engines (here: (o) - "open"; (h) - "closed").

On FIG. 9 shows the indicator diagrams of the traditional and proposed ICE.

On FIG. 10 shows the effect of the compression ratio on the flow of the working process when the maximum combustion pressure is limited.

Implementation of the invention

The invention can be implemented in the form of the device shown in FIG. 3 and with details in FIG. 4. The implementation of the invention involves the use of oppositely moving pistons 7 and 8 connected by rods 5 and 6 with rocker arms 3 and 4, respectively. The transformation of the rocking movements of the rocker arms 3 and 4 into the rotational movement of the crank 1 occurs due to the use of a three-hinged connecting rod 2. The two-moving hinge 10 with an eccentricity e2, being passive, can perform rotational-oscillatory movements, and the hinge 9 with an eccentricity e1 with a drive, being active, can perform only rotational movement (one- or opposite-direction with the crankshaft as in Fig. 2).

The double-moving hinge 10 can be made in the form of a double-moving rotational-translational kinematic pair of the "hinge-slider" type, which allows, simultaneously with the rotation of the rocker arm, a translational displacement of its center of swing relative to the fixed center of rotation of the hinge, as in the prototype [8].

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

In the position of the mechanism in the region of the volume BDC (as in Fig. 3), from the air manifold 14 through the purge windows 12, air enters the cylinder 16 and displaces the exhaust gases through the exhaust windows 11 into the exhaust manifold 13. When the crank 1 rotates (clockwise), the first exhaust windows 11 are closed and air is blown. Next, purge windows 12 are closed and the process of compressing the air charge begins.

In the variant of the diesel working process with compression ignition in the region of volumetric TDC, the fuel is supplied through the nozzle 15 to the combustion chamber (CC) formed by the bottoms of the pistons 7 and 8, and the walls of the cylinder 16. In the variant of the working process with external carburetion and forced ignition, the nozzle (not shown) can be located in front of the purge windows 12. After the pistons 7 and 8 have passed the volumetric TDC, the combustion process of the fuel is completed and the process of gas expansion begins with the completion of useful work. Before reaching the geometric BDC of piston 7, exhaust windows 11 open and the free release of exhaust gases into the exhaust manifold 13 begins. Further, before reaching the geometric BDC of piston 8, purge windows 12 open and forced exhaust gases are expelled with their replacement by scavenging air, t .e. purge process. The two-stroke cycle is completed.

The crankshaft (crank 1) is connected with an active two-movable hinge 9 mechanical transmission: gear, chain, belt. The intermediate agent of this connection is an auxiliary device for adjusting the phase angle between the positions of the crank 1 and the eccentricity of the hinge 9 - the phase regulator. The phase regulator can be of a hydraulic type, as in variable valve timing (VVT) systems of automobile engines. But four-five-blade phase regulators have a limited angle range of 20 ... 30 degrees, which is not enough for stable control of the engine mechanism in order to change the compression and expansion ratios. Desirable is the range of regulation of the phase angle 90 ... 110 degrees, p.c.v.

A larger range of regulation is provided by mechanical phase regulators based on a pair of special helical gears with the opposite direction of cutting teeth. They perform the function of coupling halves, which are covered by a common cylindrical coupling. The displacement of the coupling along the axis ensures the angular displacement of one shaft relative to the other.

As a phase regulator, a device (indicated by "F") can be used, made according to kinematic schemes as in Fig. 4. In FIG. 3 shows a conventional connection between the crankshaft 1 and the hinge 9 using a spur gear with unidirectional rotation of the gears, while the phase regulator "F" (option as Fig. 4a) is represented as an intermediate gear. The mechanism is shown in position at a phase angle value of 90 degrees, r.c.v. (crank advance). The phase angle is changed by rotating the phase regulator housing using a worm gear.

The presence of two hinges in the head of the connecting rod 2 for connection with the rocker arms 3 and 4 leads to the fact that when the connecting rod 2 is tilted, caused by the rotation of the neck of the crank 1, at any moment, except for volumetric BDC and TDC, asymmetry occurs in the angular velocities of the rocker arms 3 and 4: one speeds up, the other slows down. As a result, the pistons reach their dead points (minimum distance to the center of the CS) at different times. Since the volumetric TDC practically coincides in angle p.k.v with the position of the crank at the point of 180 degrees, p.k.v. (geometric TDC), it can be argued that over the entire range of regulation of the phase angle, the positions of the dead points of the pistons change little: exhaust - 18 ... 20 degrees, c.c.v. to TDC; purge - 13 ... 20 degrees, p.k.v. after TDC. Thus, there is a phase shift of the dead points of the pistons of 30 ... 40 degrees, c.c.v., which is 3-4 times greater than the mismatch angle of 10-12 degrees, c.c.v. cranked vlov ICE with PDP, made according to the classical scheme ("traditional").

An example of a possible implementation of the proposed ICE.

As an analogue, the internal combustion engine of a sports aircraft was taken, a 3-cylinder diesel engine with a PDP (traditional) "Gemini-YuO" with S / D = 2 × 72/69, power N _e = 75 kW, with a crankshaft speed of n = 4000 rpm, with a power density of 46 kW/l.

Initial data:

1. Power - 80 kW (2 cylinders)

2. RPM k.v. - 4000 rpm

3. Stroke - 95 mm

4. Cylinder diameter - 80 mm

5. Crank radius - 45mm

6. Connecting rod length - 90 mm

7. Compression ratio (geometric) - 19

8. Compression ratio (actual) - 15

The use of hinge 9 with eccentricity e1=3 mm and hinge 10 with eccentricity e2=8 mm allows, by changing the rotation phase of the hinge 9, to change the compression ratio over a wide range: from 9 to 16 (see Fig. 5).

The asymmetry of the dependences of the piston stroke S _vy and S _inlet on the angle of c.c.v. relative to the geometric TDC and their phase shift (40 degrees, c.c.v.) lead to the fact that the dependence of the total piston stroke S _pdp on the c.c.v. in the area of TDC volume is much flatter than that of an internal combustion engine with a traditional crank mechanism S _trad , as shown in Fig. 6. As a traditional one, an engine is considered geometrically similar to a diesel engine with a PDP type 10D100 with a compression ratio of 15.1 and a misalignment angle of the crankshafts equal to 12 degrees. a.c.c. in [9]. The flatness of this characteristic is manifested in the fact that the change in the volume of the over-piston space in the proposed ICE is slower than in the traditional one (see Fig. 7). This means that the process of heat release (combustion) proceeds as close as possible to isochoric (V=const), which is characterized by the highest thermal efficiency, all other things being equal. This phase shift is also favorable for the implementation of direct-flow purge in the process of gas exchange.

On variable compression ICEs (Prius, Toyota) operating on the Atkinson-Miller cycle and using a variable valve timing (VVT) mechanism, late closing of the intake valves leads to the expulsion of part of the air charge (or fuel-air mixture) back into the intake manifold, which is inevitable leads to a decrease in the specific power of the engine. In the proposed engine, the mechanism for changing the compression ratio is different: simultaneously with a decrease in the stroke of the pistons, an increase in the volume of the COP in the PTO occurs (see Fig. 5). At the same time, the change in the opening/closing phases of the exhaust and purge windows is much less than that of traditional internal combustion engines. If a traditional internal combustion engine has a compression ratio of 15, then to lower the compression ratio to 9, it is necessary to increase the misalignment angle of the crankshafts from 12 to 36 degrees, which means (see Fig. 8) an increase in the closing angle of the purge windows from 58 to 72 degrees, p. q.v. after BDC and an increase in the opening angle of the outlet windows from 62 to 78 degrees, p.c.v. to NMT. For the proposed ICE, a change in the compression ratio from 16 to 9 implies an increase in the closing angle of the purge windows from only 52 to 56 degrees, p.c.v. after BDC with a practically unchanged phase of opening the exhaust windows.

Thus, the proposed internal combustion engine is characterized by a much smaller loss of power for the implementation of gas exchange processes than a traditional internal combustion engine.

В расчетах использовались одинаковые режимные параметры: цикловая подача топлива, коэффициент избытка воздуха, давление и температура продувочного воздуха. Процесс сгорания расчитывался с использованием модели И.И. Вибе с m=0,3 и ϕ_z=40 град, п.к.в., опережение начала сгорания ϕ_ос=5 град, п.к.в. до ВОМТ, теплопередача по формулам Г. Вошни.To identify the advantages of the proposed design scheme of the internal combustion engine with PDP compared to the traditional one, a series of calculations of the working process was performed in order to compare indicator indicators (efficiency, average pressure). An engine with two crankshafts displaced by 12 degrees, c.c.v. with the same displacement, COP volume, actual compression ratio

The same operating parameters were used in the calculations: cyclic fuel supply, excess air ratio, pressure and temperature of the purge air. The combustion process was calculated using the model of I.I. Vibe with m=0.3 and ϕ _z =40 deg, p.c.v., advancing the start of combustion ϕ _os =5 deg. up to VOMT, heat transfer according to the formulas of G. Voshni.

As seen from FIG. 9 at the same pressures of the beginning of combustion, in the proposed ICE, the maximum combustion pressure is higher than in the traditional ICE due to the lower rate of change in the volume of the over-piston space (see Fig. 7). The average indicator pressure P _i =0.84 MPa for the proposed internal combustion engine is higher than that of the traditional P _i =0.73 MPa by 15%, which means its increased fuel efficiency.

Unlike internal combustion engines operating on the Atkinson-Miller cycle, the proposed internal combustion engine allows not only not to reduce the specific power with a decrease in the compression ratio, but, on the contrary, to increase it. From FIG. 10 shows that a decrease in the compression ratio from 15 to 9 with an increased purge pressure from 0.125 to 0.185 MPa and a limitation on the maximum combustion pressure P _z \u003d 13 MPa allows you to increase the average indicator pressure P _i from 0.84 to 1.30 MPa, which at speed k.v. 4000 rpm and mechanical efficiency 0.82 means obtaining a specific power from 46 to 72 kW / l.

The proposed internal combustion engine provides an excess of the expansion ratio over the compression ratio in the entire range of the latter.

Thus, the proposed engine provides the achievement of a technical effect, which consists in increasing fuel efficiency, improving the specific weight and size indicators. 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 apparent to those skilled in the art of engine building and the invention itself is susceptible to many variations, modifications and changes in detail, it is intended that all material contained in the foregoing description or shown in the accompanying drawings is to be interpreted as illustrative and not in restrictive sense.

Sources of information

1. Internal combustion engines. The device and operation of piston and combined engines. Alekseev V.P., Voronin V.F., Grekhov L.V. etc. M., "Engineering", 1990, 284 p.

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

3. https://www.geminidiesel.aero

4.https://www.achatespower.com

5.Pat. US 336505, 1886.

6.Pat. US 2730087, 1956.

7.Pat. US 9359896, 2016.

8. RU 2739104, 2020.

9. Internal combustion engines (locomotive diesels and gas turbines). Simeon A.E., Khomich A.Z., Kurits A.A. and others. M., "Transport", 1984,384 p.

Claims (8)

1. A two-stroke reciprocating internal combustion engine, containing a cylinder block equipped with purge and exhaust ports, pistons moving in said cylinders in opposite directions, each of which controls purge and exhaust, respectively, a mechanism for converting the reciprocating motion of the pistons into rotational motion of the crankshaft by means of one common connecting rod and pivotally connected through the rod with each of the pistons of two rocker arms, swinging on two-movable hinges with fixed centers of rotation, characterized in that one of the hinges is driven to change the phase angle of the hinge relative to the crankshaft crank to change the compression ratio and degree of expansion. 2. Two-stroke reciprocating internal combustion engine according to claim 1, characterized in that the active two-moving joint with a drive refers to the rocker of the exhaust piston, and the passive two-moving joint without a drive refers to the rocker of the scavenging piston. 3. A two-stroke piston internal combustion engine according to claim 2, characterized in that both two-moving hinges are made in the form of a two-moving rotational-rotational kinematic pair of the “hinge-hinge” type, which simultaneously with the rotation of the rocker arm allows a rotational arc displacement of its center of swing relative to a fixed center hinge rotation. 4. A two-stroke piston internal combustion engine according to claim 2, characterized in that the passive two-moving hinge without a drive is made in the form of a two-moving rotational-translational kinematic pair of the “hinge-slider” type, which allows, simultaneously with the rotation of the rocker arm, a translational displacement of its swing center relative to fixed pivot point. 5. A two-stroke piston internal combustion engine according to claim 2, characterized in that the drive of the active two-moving hinge ensures its rotation is unidirectional with the rotation of the engine crankshaft and with a phase advance. 6. A two-stroke piston internal combustion engine according to claim 2, characterized in that the drive of the active two-movable joint ensures its rotation in the opposite direction with the rotation of the engine crankshaft and with a phase lag. 7. A two-stroke reciprocating internal combustion engine according to claim 5 or 6, characterized in that the drive of the active two-moving joint contains a hydraulic or mechanical phase regulator. 8. A two-stroke piston internal combustion engine according to claim 7, characterized in that the phase regulator is driven by a third-party energy source and, depending on the engine load, changes the compression ratio and expansion ratio.

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