RU2044138C1 - Two-stroke internal combustion engine - Google Patents

Abstract

FIELD: engine engineering. SUBSTANCE: additional inlet air passageway 10 is connected with blowing passageway 4 from the side of blowing port 5. The diameter and length of additional inlet air passageway 10 are defined by relationships presented in the invention description. EFFECT: enhanced efficiency. 1 dwg

Description

 The invention relates to heat engines, namely to piston internal combustion engines.

Known two-stroke internal combustion engine containing at least one pair of cylinders equipped with pistons kinematically connected with the crankshaft with the possibility of their synchronous movement and forming compression chambers of different volumes in the cylinders, inlet, purge and exhaust channels and isolated crank chambers connected to the purge channels, and communicated with each other using a connecting channel, the cross-sectional area of which is equal to 4-10% of the piston bottom area, the spark plug located in the compression chamber of the first cylinder, and two carburetors. The first carburetor is installed in the inlet channel of the first cylinder and is intended for the preparation of a combustible mixture with an excess air coefficient α 0.75-1.2. The second carburetor is installed in the inlet of the second cylinder and is designed to prepare a combustible mixture with α 0.75. The output windows of the exhaust channels in the cylinders are made of different heights so that the height of the output window of the exhaust channel of the second cylinder exceeds the height of the output window of the exhaust channel of the first cylinder by 10-20 ° ^{of the} crankshaft. The spark plug is installed in the compression chamber of the first cylinder centrally, and the compression chamber of the latter is made larger in volume than the compression chamber of the second cylinder [1]
However, this engine has significant fuel loss during purging.

A two-stroke internal combustion engine is also known, comprising two adjacent cylinders equipped with pistons operating in the same phase and communicated with each other by a bypass channel made in the cylinder head, an exhaust gas bypass channel connected to the first cylinder, two connected to the second a purge channel cylinder, one of which is connected to a source of enriched combustible mixture, and the other to a source of lean fuel mixture, an spark plug mounted in a second cylinder. The cylinder head is equipped with a deflector located in the second cylinder between the spark plug and the bypass channel. The purge channels are connected to the second cylinder on both sides of the plane passing through the deflector parallel to the axis of the cylinder, and the channel associated with the source of lean working mixture is located on the side of the bypass channel [2]
However, the efficiency of reducing fuel consumption is low.

 In addition, the in-phase movement of the pistons leads to an increase in the unevenness of the torque and, as a consequence, to the unevenness of the stroke.

 Closest to the invention is a two-stroke internal combustion engine, which comprises a cylinder with exhaust and purge windows, a crank mechanism with a piston, a tight crank chamber, at least one purge channel communicating the purge window of the cylinder with the volume of the crank chamber, and also the main mixture forming an intake tract comprising a main throttle valve. Thus, this engine belongs to the class of internal combustion engines with external mixture formation, carried out, for example, using a carburetor in the main intake tract. Its main structural difference is the presence of an additional discharge channel and an additional air compressor driven by the engine either due to kinematic coupling with a crank mechanism or due to the energy of exhaust gases (turbocharger version). In this case, the discharge channel comprises a metering drive valve and connects the air compressor to the purge channel in the region of the purge window.

When the engine is running after filling the crank chamber with a combustible mixture (upward movement of the piston), the cavity of the purge channel is filled with clean air from the compressor through the discharge channel. The necessary dosage of such filling is carried out by a metering valve. At the next purge of the cylinder, it primarily receives clean air from the purge channel and only in the final stage of purging is the combustible mixture. Due to this, the purge gas losses turn out to consist mainly of clean air that does not contain fuel. Thanks to this, purge losses of fuel are reduced to a minimum. The engine can be made both in the piston version and in the versions with valve or spool control of the inlet of the combustible mixture into the crank chamber [3]
However, the presence of a special air compressor and a drive metering valve significantly complicates the design.

 The aim of the invention is to simplify the design.

d_вк
l_дк=

l_вк где d_дк, d_вк диаметры дополнительного воздушного и смесеобразующего впускных каналов;
l_дк, l_вк длины дополнительного воздушного и смесеобразующего впускных каналов;
n количество дополнительных впускных воздушных каналов.This is achieved by the fact that a two-stroke internal combustion engine with external mixture formation, comprising a piston, a cylinder connected to the crank chamber via at least one purge channel through a purge window, the mixture-forming inlet channel, is provided with at least one additional air inlet connected with a purge channel on the side of the purge window, and the diameter and length of the additional inlet air channel is determined from the conditions
d _dk =

d _vk
l _dk =

l _vk where d _dk , d _vk diameters of the additional air and mixture-forming inlet channels;
l _dk , l _{vk of the} length of the additional air and mixture-forming inlet channels;
n number of additional air inlets.

 The mixing inlet channel has a throttle, and the additional air inlet has an additional throttle.

 The drawing schematically shows the proposed engine. It contains a cylinder 1, a piston 2, a crank chamber 3, a purge channel 4, a purge window 5, a main inlet channel, a carburetor 7 of the main inlet channel, a flap (automatic) or slide valve 8 of the main intake, a main throttle valve 9, an additional air channel 10 , flap or slide valve 11 of the additional air channel, additional throttle valve 12, exhaust channel 13, exhaust window 14 and the spark plug 15.

 The engine operates as follows.

 When the piston 2 moves upward in the cylinder 1 in the crank chamber 3, a vacuum is created, under the action of which through the simultaneously opening valves 8 and 11, the combustible mixture enters the chamber 3 through the main inlet path formed by the main inlet channel 6 and the carburetor 7, and into the cavity of the purge channel 4 clean air through an additional air channel 10. At the same time, a combustible mixture is compressed in the above-piston volume of cylinder 1. When the piston approaches the top dead center (TDC), the spark plug 15 fires and the mixture above the piston burns out, and the gas temperature and pressure rise to a maximum. By the same moment, the maximum volume of the crank chamber 3 is filled with a fresh charge of the combustible mixture, and the cavity of the channel 4 with air. After the TDC, with some delay (by inertial pressurization), valves 8 and 11 are closed.

 When the piston 2 moves down (stroke), high-pressure hot gas above the piston gives off its energy to the latter, and through the connected connecting rod and crank to the engine power take-off shaft. At the same time, compression of the combustible mixture and air proceeds in the chamber 3 and in the channel 4 with an increase in their pressure. At the moment when the edge of the piston head crosses the upper edge of the exhaust window 14, the exhaust exhaust gas exhaust process begins. Its main mass is carried out of the cylinder through the exhaust channel 13 with hypersonic speed in the very first moments of the exhaust, as a result, the pressure in the cylinder drops sharply. After this, the purge window 5 opens and the cylinder volume begins to be purged with clean air entering it from the cavity of the purge channel 4. Any deflection geometry, deflector-loop or mixed, is possible.

 Following the air purge, the cylinder is purged with a combustible mixture coming from the chamber 3 through the purge channel 4. This mixture displaces the remaining exhaust gas from the cylinder together with the purge air into the channel 13. The purge process continues after the piston passes the bottom dead center (BDC) and ends to the moment the piston 2 closes the exhaust window 14 when moving up. At this point, the engine returns to its initial state. The described operation cycle is push-pull, as it takes place in two cycles (piston stroke) up and down or in one revolution of the crankshaft. Due to the fact that the purge losses of gas are mainly clean air that does not contain fuel, the purge losses of the latter are very small.

 For proper operation of the engine, it is important that the volume of air introduced into the channel 4 is not less than the volume of gas lost during purging. Otherwise, a significant portion of the combustible mixture will be expended on purge losses, which will lead to an increase in fuel purge losses. If air will be admitted significantly more than its losses during purging, then it will occupy a noticeable volume in the cylinder, the amount of which decreases the volume of the filling combustible mixture. As a result, the power developed by the engine decreases. In order for the intake air volume to be optimal, it is necessary to maintain the performance of the additional air channel 10 at a level of 20-30% of the performance of the main intake channel 6, taking into account the additional resistance of the carburetor 7. At maximum power, this ratio of performance is ensured by a constructive choice of the geometry of the channels 6 and 10 (the ratio of sections and lengths).

 When adjusting the engine power with the main throttle 9, the performance of channel 6 varies over a very wide range. To maintain this performance ratio at partial power modes, an additional throttle valve 11 is installed in the channel 10, kinematically connected with the valve 9. In this case, it is quite acceptable, and in many cases extremely desirable, that as the power decreases (the throttling increases), the relative performance of the additional air channel 10 increased to 35-40%. This means a transition to a lean mixture or a partial introduction of regulation of the quality of the combustible mixture, which can significantly increase the economy. chnost engine. In this case, one should not be afraid of a deterioration in the flammability of the combustible mixture (deterioration in the reliability of ignition), since sequential purging with air and a combustible mixture ensures their layer-by-layer distribution in the cylinder. In this case, a layer with a normal mixture will have quite good flammability. Unlike the prototype, this engine is well compatible with various systems of preliminary general pressurization, in particular with preliminary turbocharging.

 The given limits of the channel productivity ratio can be formulated as conditions by the ratio of the design parameters of the channels. To do this, consider the following.

1

(1) где С_р теплоемкость при постоянном давлении;
Т* температура в атмосфере;
Р давление в камере;
Р* атмосферное давление;
γ показатель адиабаты.As follows from the Bernoulli law for ideal flows, under the influence of the pressure difference Δ P at the ends of the channels, the same flow rates V
V

1

(1) where C _{p is the} heat capacity at constant pressure;
T * temperature in the atmosphere;
P pressure in the chamber;
P * atmospheric pressure;
γ is the adiabatic exponent.

V (2) где S,D площадь и диаметр канала, то соотношение производительностей будет иметь вид

(3) где G_дк производительность дополнительного канала;
G_ок производительность основного смесеобразующего (карбюраторного) канала;
D_дк диаметр дополнительного канала;
D_ок эффективный (с поправкой за диффузорное сужение) диаметр основного (смесеобразующего) канала.The indicated equality of velocities will be observed when taking into account additional resistance to the flow due to viscous friction losses, subject to the condition of maintaining the geometric similarity of the channels and the vortex interaction between the flow and the walls of the channels. Since the performance of channel G can be represented as
G SV

V (2) where S, D is the area and diameter of the channel, then the ratio of performance will be

(3) where G _{dk the} performance of the additional channel;
G _{ok the} performance of the main mixture-forming (carburetor) channel;
D _dk diameter of the additional channel;
D _ok effective (adjusted for diffuser narrowing) the diameter of the main (mixture-forming) channel.

или
D_дк=

· D_ок (4)
Кроме того, для соблюдения геометрического подобия длина дополнительного воздушного канала l_дк должна быть равной
l_дк= l_ок

· l_ок (5) где l_ок длина впускного смесеобразующего канала.The purge channel in the cylinder may not be one, but two or three, depending on the particular design. In the general case, there are n purge channels. Each purge channel may be associated with a separate additional air channel, so that their total number per cylinder is also n. In this case, the performance of a separate additional channel should be reduced n times. Thus, the condition for the ratio of productivity is transformed to the form

or
D _dk =

D _ok (4)
In addition, to comply with geometric similarity, the length of the additional air channel l _dk must be equal
l _dk = l _ok

· L _ok (5) where l _{ok is the} length of the inlet mixture forming channel.

 Conditions (4) and (5) are the constructive conditions for the correct operation of the engine.

Claims (1)

A TWO-STROKE INTERNAL COMBUSTION ENGINE, comprising a piston, a cylinder connected to the crank chamber via at least one purge channel through a purge window and a mixture-forming inlet channel, characterized in that it is equipped with at least one additional inlet channel connected to the purge channel from the side a purge window, the diameter and length of the additional inlet channel being determined in accordance with the dependencies

where d _{d to} , d _{c to the} diameters of the additional inlet and mixture forming channels;
l _{d to} , l _{s to the} length of the additional inlet and mixture-forming channels;
n number of additional channels.