Two-stroke internal combustion engine comprising an optimized injection system

Abstract

A two-stroke internal combustion engine comprises a cylinder, a piston arranged at least partially in the cylinder to define a combustion chamber, a crankshaft connected in torque-transmitting manner to the piston, a fuel injector arranged in the combustion chamber at a pressure not higher than 10 bar, an ignition device arranged in the combustion chamber, an intake duct fluidically connected to the combustion chamber through at least one intake port, an exhaust duct fluidically connected to the combustion chamber through an exhaust port to exhaust gases present in the combustion chamber in use; the engine further comprises a compressed air delivery duct fluidically connected to the combustion chamber through a delivery port, the delivery port being arranged at a vertical level higher than the vertical level of the intake port, and the delivery port and the injector being arranged at first and second vertical levels, respectively, higher than the vertical level of the exhaust port, the second level being greater than the first level, and the delivery port being oriented towards a portion of the cylinder head so that a first delivery direction of the flow of compressed air is deviated from the direction of exhaust of the gases through the exhaust port, and the fuel injector being oriented towards the piston so that a second delivery direction of the flow of atomized fuel tends towards the direction of exhaust of the gases, and the flow of compressed air introduced into the combustion chamber by the delivery port intersects the flow of fuel so that the trajectory direction of the flow of fuel is deviated from the direction of exhaust of the gases.

Description

Technical Field

[0001] [1] The present invention relates to a two-stroke internal combustion engine, and more particularly to a two-stroke internal combustion engine including an optimized injection system. Background Technology

[0002] [2] In the field of two-stroke internal combustion engines, it is well known that unburned hydrocarbon emissions generated by in-cylinder combustion flow from the combustion chamber through the exhaust port and are released into the atmosphere, which leads to a number of problems. For example, the known solutions have serious problems in complying with increasingly stringent regulations related to emissions of pollutants into the atmosphere, and poor combustion efficiency due to suboptimal mixing of fuel and oxidant is a typical problem of carburetor-fed two-stroke engines, such as the injection system known as "Ditech", or indirect injection system, i.e., an injection system outside the cylinder.

[0003] [3] An internal combustion engine is known from US4191141, which involves introducing pressurized fluid into the cylinder from an additional intake port at an intermediate height in the cylinder working space between the top dead center and bottom dead center positions on the piston head surface, in order to separate the incoming air-fuel mixture from the outgoing combustion gases.

[0004] [4] Therefore, there is always a need for simple and compact solutions from a structural perspective that can minimize emissions of unburned hydrocarbons and improve the combustion efficiency of two-stroke engines. Summary of the Invention

[0005] [5] The object of the present invention is to at least partially satisfy the above requirements, which is achieved by the two-stroke internal combustion engine according to claim 1.

[0006] [6] According to a preferred embodiment of the invention, a two-stroke internal combustion engine is described, having an optimized structural configuration that minimizes the emission of unburned hydrocarbons into the atmosphere, thereby not only contributing to the reduction of atmospheric pollutants but also to improving engine efficiency. To achieve this result, the engine includes several components known to those skilled in the art, particularly a cylinder, a piston at least partially disposed within the cylinder to define a combustion chamber, a crankshaft connected to the piston in a torque-transmitting manner, a fuel injector in the combustion chamber, an ignition device disposed in the combustion chamber, an intake manifold fluidly connected to the combustion chamber via at least one intake port, and an exhaust manifold fluidly connected to the combustion chamber via an exhaust port to discharge gases present in the combustion chamber during use. It should be noted that, in order to make the solution as compact as possible, the injector is configured to deliver atomized fuel at a pressure not exceeding 10 bar, thus there is no fuel pressurization system on the engine exceeding the aforementioned pressure. According to a first aspect of the invention, the engine described below further includes a compressed air supply line fluidly connected to the combustion chamber via a delivery port, the delivery port being positioned at a vertical height above the location of the intake port, and the delivery port and the injector being positioned at first and second vertical heights above the location of the exhaust port, respectively. Specifically, the second vertical height is greater than the first vertical height, i.e., the delivery port is located longitudinally between the exhaust port and the fuel injector. According to another aspect of the invention, based on the above structural arrangement, the delivery port is oriented towards a portion of the cylinder head so that a first delivery direction of the compressed air flow deviates from the direction of gas discharge through the exhaust port. Conversely, the fuel injector is oriented towards the piston so that a second delivery direction of the fuel flow tends towards the direction of gas discharge. Preferably, the compressed air delivery port and the fuel injector are located between the exhaust port and a height representing the top dead center of the cylinder. According to the invention, the above design configuration brings the delivery port and the injector closer together so that, in operation, the compressed air flow delivered to the combustion chamber through the delivery port intersects with the fuel flow delivered by the injector. Furthermore, the compressed air flow is delivered at a pressure that can be less than, equal to, or greater than the injector pressure, and the momentum of the compressed air flow allows the trajectory of the fuel flow to deviate from the direction of gas discharge. Advantageously, the supplied compressed air has a carrying effect on the fuel flow delivered by the injector, thereby guiding it away from the exhaust port. In this way, the fuel flow travels a longer trajectory within the combustion chamber before reaching the exhaust port, thus, compared to conventional solutions, more fuel remains within the combustion chamber when the piston completes the compression phase, rather than being partially expelled from the combustion chamber via the exhaust port. Attached Figure Description

[0007] [7] The structural and functional characteristics of this two-stroke internal combustion engine can be better understood from the detailed description below, with reference to Appendix Figure 1 , Figure 1 This represents a preferred but not limiting embodiment. Detailed Implementation

[0008] [8] According to a preferred embodiment of the present invention, Figure 1 A schematic diagram of a portion of a two-stroke internal combustion engine M is shown, which includes a low-pressure fuel injection system. For the purposes of the description below, the term "low-pressure fuel injection system" refers to a system that injects fuel into the combustion chamber within the cylinder at a pressure not exceeding 10 bar. In particular, as... Figure 1As shown, the engine includes a crankcase 1, which houses a portion of a drive shaft 2, such as a portion of a crankshaft, to which a piston 4 is fixed. Furthermore, the crankcase 1 is fluidly connected to an intake manifold L1 via an intake port 3, through which air drawn from the external environment is introduced into the crankcase. The crankcase 1 also has an open top from which a cylinder 6 extends longitudinally. The piston 4 includes a connecting rod 7, a first end of which is connected to the crankshaft 2, and a second end, longitudinally opposite the first end, is connected to a piston head 8, which is securely engaged within the cylinder. The space defined by the piston head within the cylinder defines a combustion chamber 9, in which, during operation, a mixture of atomized fuel and oxidant to be ignited to achieve the movement of the piston 4 and consequently the crankshaft 2 is distributed in a known manner. Specifically, the ignition of the atomized fuel and combustion mixture is performed in a conventional manner for two-stroke internal combustion engines, i.e., by generating a spark through a combustion ignition device 10 (e.g., a spark plug) to ignite the mixture fed into the combustion chamber 9. Specifically, air from the intake manifold L1 and entering the crankcase 1 through the intake port 3 is used as a combustion agent. To deliver the combustion agent from the crankcase 1 to the combustion chamber 9, a passage 11 is fluidly connected to the crankcase 1 at its inlet and to the combustion chamber 9 at its outlet. This passage preferably extends outside the cylinder 6, having a first port 12 on the crankcase 1 side in fluid communication with it, and a second port 13 longitudinally opposite the crankcase 1 to the first port 12, thus fluidly communicating with the combustion chamber 9. In operation, the movement of the piston 4 and the rotational movement of the crankshaft 2 facilitate the generation of an airflow toward the first port 12 in the direction of crankshaft rotation, thereby transferring the air received in the crankcase 1 to the combustion chamber 9 through the first port 12. Preferably, multiple passages 11 can be provided, for example, arranged around the circumference of the cylinder, wherein each passage includes a first port 12 for receiving air from the crankcase 1 in operation and a second port 13 for delivering the air received from the crankcase 1 to the combustion chamber 9. For example, up to seven channels 11 can be provided, with the crankcase 1 functioning as an intake manifold. An injector 14 facing the combustion chamber 9 is also provided, through which atomized fuel is introduced at a pressure not exceeding 10 bar. Therefore, based on the above structural configuration, atomized fuel and propellant are released into the combustion chamber 9 during use and mixed therein. This produces a fuel-oxidant mixture, which is then compressed in a known manner by the piston 4 moving towards the combustion ignition device during engine operation. The combustion ignition device is activated to ignite the mixture, for example by a spark, producing exhaust gases, and the pressure and volume within the combustion chamber 9 increase, causing the piston to move in the opposite direction, i.e., downwards, thereby rotating the crankshaft 2 in a known manner. The exhaust gases are then diverted to an exhaust pipe L2, which is in fluid communication with the combustion chamber 9 via an exhaust port 15.It should also be noted that the first port 12 and the second port 13 of passage 11, as well as the exhaust port 15, are positioned such that they are properly covered or exposed by the piston during use, more specifically by the side surface of the piston (also referred to by those skilled in the art as the "casing"), thereby interrupting or enabling fluid connections between the intake manifold L1 and the combustion chamber 9, and between the exhaust manifold L2 and the combustion chamber 9, respectively, particularly according to engine timing performed during the design phase. This aims to prevent a portion of the injected fuel mixture from being transferred to the exhaust manifold before ignition, while also preventing exhaust gases from being partially transferred to the intake manifold. As those skilled in the art know, timing is achieved by appropriately synchronizing the rotation of the crankshaft and the piston stroke to open and close the intake and exhaust ports. To minimize the transfer of unburned mixture to the exhaust manifold L2, and thus minimize the emission of unburned hydrocarbons into the atmosphere, according to a first aspect of the invention, the engine M includes a compressed air supply line L3, which is in fluid communication with the combustion chamber 9 via a delivery port 16. In particular, the compressed air supply line L3 is configured to, during operation, emit a compressed air flow oriented toward the fuel flow delivered by the injector 14 into the combustion chamber 9, more specifically, such that the compressed air flow exiting from the delivery port 16 intersects with the fuel flow. It should be noted that the injector 14 and the delivery port 16 are oriented such that, during operation, the compressed air flow delivered by the delivery port 16 deflects the trajectory of the fuel flow from its trajectory when it is delivered to the combustion chamber 9. For this purpose, the delivery port 16 is located at a vertical height above the location of the intake port 3, such that when the required amount of fuel is introduced through the intake port 3, the piston moving toward the cylinder head covers the cylinder port, and the injector and compressed air supply line are activated to deflect the direction of the fuel flow. Furthermore, the delivery port 16 and the injector 14 are respectively positioned at first and second vertical heights above the location of the exhaust port 15, wherein the second height is greater than the first height, i.e., the delivery port 16 is located longitudinally between the exhaust port and the injector. Preferably, the delivery port 16 and the injector 14 are located on the same side of the split surface of the cylinder 6, for example, the split surface passes through the cylinder axis and is preferably parallel to the crankshaft axis 2. Preferably, the delivery port 16 and the injector 14 may also be located on opposite sides of the split surface of the cylinder, i.e., one of the delivery port 16 and the injector 14 is located on the exhaust port 15 side. According to one aspect of the invention, the delivery port 16 is oriented toward a portion of the cylinder head 6 so that a first delivery direction D1 of the compressed air flow deviates from the direction DS of gas discharge through the exhaust port 15. For example, the delivery port is an orifice whose axis defines the first delivery direction D1. Furthermore, the fuel injector 14 is oriented toward the piston 4 so that a second delivery direction D2 of the fuel flow tends toward the direction DS of gas discharge through the exhaust port 15. For example, the second direction D2 is defined by the axis of the injector orifice 14. Based on this design configuration, the delivery port 16 and the fuel injector 14 are therefore arranged and oriented in such a way that, in use, the compressed air flow and the fuel flow intersect each other, a feature that causes the direction of the fuel flow to be deflected by the compressed air flow.Preferably, the fuel injector 14 and the delivery port 16 are longitudinally positioned between the exhaust port 15 and the height representing the piston top dead center (PMS). It should also be noted that, in order to deflect the fuel flow, the compressed air supplied to the combustion chamber 9 can be supplied at a pressure preferably less than, equal to, or greater than the pressure of the injector 14, the effect of which is related to the momentum of the compressed air flow. Preferably, the pressure of the compressed air is not higher than 10 bar and is sufficient to deflect the trajectory direction of the fuel flow away from the direction DS of the gas discharged through the exhaust port 15. According to the invention, the primary purpose of the compressed air supply line L3 is to introduce a compressed air flow into the combustion chamber 9, through which the fuel flow supplied by the injector 14 can be deflected, while the air flow required for mixing with the fuel is supplied through the intake line L2. Therefore, the size of the delivery port 16 is significantly reduced compared to the size of the second port 13 of the intake line L2, preferably the cross-section of the delivery port 16 is less than 1 / 30 of the cross-section of the second port 13, which results in a reduced contribution of the airflow supplied to the combustion chamber 9 through the compressed air supply line L3. Preferably, the airflow introduced into the combustion chamber 9 is at least an order of magnitude lower than the airflow introduced through the intake manifold L1, preferably less than 10%. Preferably, the fuel injector 14 and the delivery port 16 are disposed on the cylinder 6 such that the intersection point P between the compressed air supply direction D1 and the fuel delivery direction D2 is located on the same side of the cylinder's split surface as the injector 14 and the delivery port 16. More preferably, to achieve this result, the injector 14 and the delivery port are oriented relative to each other such that their respective delivery directions D1 and D2 are angled relative to each other, defining an angle in the range of 20 to 150 degrees. Advantageously, it should also be noted that delivering a compressed air flow intersecting with the fuel flow helps reduce the size of the fuel droplets in the delivered flow, promoting their subsequent evaporation, but most importantly, it facilitates a more uniform distribution of the mixture within the combustion chamber 9. In particular, the compressed air supplied through the delivery port 16 creates a drag effect on the fuel flow delivered by the injector 14, thereby guiding it away from the exhaust port 15. In this way, the fuel flow travels a longer path within the combustion chamber 9 before reaching the exhaust port 15, resulting in more fuel remaining in the combustion chamber when the piston completes its compression stroke compared to conventional solutions. The interaction between compressed air and the injected fuel also facilitates the homogenization of the mixture; this means that the non-uniform regions of rich and lean mixtures are minimized, promoting proper combustion and leading to increased efficiency and reduced emissions. This solution is particularly advantageous in any vehicle including handlebars, especially in motorcycle applications. Preferably, for small-displacement handlebar-equipped vehicles, such as 50cc, one injector 14 and one compressed air inlet 16 are provided; however, for larger-displacement handlebar-equipped vehicles, such as 125cc, 250cc, or 300cc, two injectors 14 and two corresponding inlets 16 can be provided to increase the maximum flow rate of fuel delivered to the combustion chamber 9, which is still within the scope of this invention.

Claims

1. A two-stroke internal combustion engine (M), comprising: Cylinder (6); Piston (4), which is disposed in the cylinder to define the combustion chamber (9); A drive shaft (2) is connected to the piston (4) in a torque transmission manner; A fuel injector (14) with a pressure not exceeding 10 bar is disposed in the combustion chamber (9); An ignition device (10) is disposed in the combustion chamber (9); An intake manifold (L1) is fluidly connected to the combustion chamber (9) via at least one intake port (13); An exhaust pipe (L2) is fluidly connected to the combustion chamber (9) through an exhaust port (15) for the gas present in the combustion chamber; A compressed air supply line (L3) is fluidly connected to the combustion chamber (9) through a delivery port (16), which is located at a vertical height above the location of the air inlet (13). The invention is characterized in that the delivery port and the injector (14) are respectively located at a first vertical height and a second vertical height higher than the location of the exhaust port (15) towards the cylinder head, the second height being greater than the first height, and wherein the delivery port is oriented towards the cylinder head so that the first delivery direction (D1) of the compressed air flow deviates from the direction (DS) of the gas being discharged through the exhaust port (15), and wherein the fuel injector is oriented towards the piston (4) so ​​that the second delivery direction (D2) of the atomized fuel flow is oriented towards the direction of gas discharge (DS), and the compressed air flow introduced into the combustion chamber by the delivery port (16) intersects with the fuel flow so that the trajectory direction of the fuel flow deviates from the direction of gas discharge (DS). Furthermore, the injector (14) and the delivery port (16) are arranged longitudinally between the exhaust port (15) and the vertical height representing the piston top dead center (PMS).

2. The engine (M) according to claim 1, wherein the injector (14) and the delivery port (16) are disposed on the same side of the split surface of the cylinder (6).

3. The engine (M) according to claim 2, wherein the orientation angle of the compressed air delivery direction (D1) and the fuel delivery direction (D2) is between 20 degrees and 150 degrees, and the intersection point (P) is located on the same side of the split surface of the cylinder (6) as the injector (14) and the delivery port (16).

4. The engine (M) according to any one of the preceding claims, wherein the cross-section of the delivery port (16) is less than 1 / 30 of the cross-section of the air inlet (13).

5. The engine (M) according to any one of the preceding claims, wherein the pressure of the compressed air delivered through the delivery port (16) is not higher than 10 bar.

6. The engine (M) according to any one of the preceding claims, wherein the delivery port (16) and the injector (14) are located in the vertical direction between the exhaust port (15) and the ignition device (10).

7. The engine (M) according to any one of the preceding claims, wherein the delivery port (16) faces the ignition device (10).

8. The engine (M) according to any one of the preceding claims, wherein the compressed air flow rate delivered through the delivery port (16) is at least one order of magnitude lower than the air flow rate delivered through the air inlet (13).

9. A vehicle with handlebars, comprising a two-stroke internal combustion engine according to any one of claims 1 to 8.

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