Engine piston, engine and engine control method

Abstract

This invention relates to the field of engine technology, and discloses an engine piston, an engine, and an engine control method. The engine piston has a second sub-combustion recess connected to a first sub-combustion recess and an upper combustion recess; the lower combustion recess is symmetrical about a plane of symmetry. The first sub-combustion recess is semi-ellipsoidal, and the contour line of its wall on the plane of symmetry is a first semi-elliptical contour line. The central axis of the piston body and the major axis of the first contour line are perpendicular and both lie on the plane of symmetry. The second contour line of the wall of the second sub-combustion recess on the plane of symmetry is connected to the first end of the first contour line and is oriented along one side of the line containing the minor axis of the first contour line. Both the second and first contour lines are curves of the same ellipse. During the intake phase, it can better sweep out residual exhaust gas in the first sub-combustion recess, avoiding the formation of flow dead zones. During the compression phase, it can improve the tumbling effect of the fluid. When the piston reaches near top dead center, it can increase the flame propagation speed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engines, in particular to an engine piston, an engine and an engine control method. BACKGROUND

[0002] Adopting methanol to replace traditional diesel, gasoline and other fuels can greatly reduce the emission of engine nitrogen oxides, particulate matter and the like. Among them, the mixing level and turbulent kinetic energy of the mixed gas flowing into the combustion chamber are important indicators affecting the combustion performance of the methanol engine, and the geometric configuration of the combustion chamber is one of the important factors affecting the mixing level and turbulent kinetic energy of the mixed gas in the combustion chamber.

[0003] The methanol engine in the related art usually sets the pit wall of the combustion chamber pit to be a cylindrical body or a smooth curved surface type. For the pit wall of the combustion chamber pit in the form of a cylindrical body, the top surface of the piston will hinder the mixed gas from flowing into the combustion chamber, and is easy to form a mixing dead zone, which is not conducive to mixing uniformity. For the pit wall of the combustion chamber pit in the form of a smooth curved surface, although it can guide the mixed gas to form a rolling flow in the combustion chamber to improve the mixing uniformity and flame propagation speed, and can improve the turbulent kinetic energy of the mixed gas in the combustion chamber, but the scavenging effect of the mixed gas in the scavenging stage and the turbulent kinetic energy in the combustion chamber still need to be further improved. SUMMARY

[0004] The purpose of the present application is to provide an engine piston, an engine and an engine control method to solve the above-mentioned problems existing in the combustion chamber in the related art.

[0005] In one aspect, the present application provides an engine piston, which comprises a piston body, wherein the piston body is provided with a top surface perpendicular to the axial direction of the piston body and a combustion chamber pit recessed in the top surface;

[0006] The combustion chamber pit comprises a lower combustion pit and an upper combustion pit distributed in sequence along the axial direction of the piston body, the lower combustion pit comprises a first sub-combustion pit and a second sub-combustion pit, the second sub-combustion pit is arranged between the first sub-combustion pit and the upper combustion pit, and is connected with the first sub-combustion pit and the upper combustion pit; the upper combustion pit is used to guide the fluid to flow into the first sub-combustion pit through the second sub-combustion pit;

[0007] The lower combustion pit is symmetrical about a symmetry plane, the first sub-combustion pit is in a semi-ellipsoidal shape, a profile line of the pit wall of the first sub-combustion pit on the symmetry plane is a first profile line, the first profile line is a semi-ellipse, a center axis of the piston body and a straight line on which a long axis of the first profile line is located are perpendicular and both are located on the symmetry plane; a profile line of the pit wall of the second sub-combustion pit on the symmetry plane is a second profile line, the second profile line is connected with a first end of the first profile line and is located on one side of a straight line on which a short axis of the first profile line is located in a direction, and the second profile line and the first profile line are curves of the same ellipse, and the direction is parallel to the straight line on which the long axis of the first profile line is located.

[0008] As an optional solution of the engine piston, a junction line of the second sub-combustion pit and the first sub-combustion pit is a first junction line, all points on the first junction line are located on the same plane; a junction line of the second sub-combustion pit and the upper combustion pit is a second junction line, all points on the second junction line are located on the same plane; the first junction line and the second junction line intersect at a second end of the first profile line.

[0009] As an optional solution of the engine piston, the upper combustion pit is in a slanting truncated cone shape, a small end of the upper combustion pit is in communication with the second sub-combustion pit, and a center axis of the upper combustion pit is perpendicular to the plane on which the second junction line is located.

[0010] As an optional solution of the engine piston, a profile line of the pit wall of the upper combustion pit on the symmetry plane includes a third profile line connected with the second end of the first profile line and a fourth profile line connected with the second profile line.

[0011] An included angle between the third profile line and the top surface is α, and a value range of α is 10°-50°; and / or, an included angle between the fourth profile line and the top surface is β, and a value range of β is 0°-30°.

[0012] As an optional solution of the engine piston, a distance between a first intersection point of the third profile line and the top surface and a second intersection point of the fourth profile line and the top surface is L1; a length of a projection of the third profile line on the plane on which the top surface is located in an axial direction of the piston body is L2, and a length of a projection of the fourth profile line on the plane on which the top surface is located in the axial direction of the piston body is L3; L2=(0.1-0.2)L1, and L3=(0.1-0.2)L1.

[0013] As an alternative to the above-mentioned engine piston, the diameter of the piston body is D1, the distance between the first intersection point of the third profile line and the top surface and the second intersection point of the fourth profile line and the top surface is L1, and L1=(0.7-0.9)D1.

[0014] As an alternative to the above-mentioned engine piston, the intersection point of the third profile line and the top surface is the first intersection point, the intersection point of the fourth profile line and the top surface is the second intersection point, the minimum distance between the first intersection point and the outer peripheral wall of the piston body is L4, the minimum distance between the second intersection point and the outer peripheral wall of the piston body is L5, and L4

[0015] As an alternative to the above-mentioned engine piston, the diameter of the piston body is D1, the long axis length of the first sub-combustion pit is D2, and the short axis length of the first sub-combustion pit is D3, D2=(0.55-0.75)D1, and D3=(0.4-0.55)D1.

[0016] The engine piston provided by the present application has at least the following beneficial effects:

[0017] By setting the first sub-combustion pit in a semi-ellipsoidal shape, the first profile line formed by the pit wall of the first sub-combustion pit on the symmetry plane is a semi-elliptical shape, and the center axis of the piston body and the straight line on which the long axis of the first profile line is located are perpendicular and both located on the symmetry plane. It can be understood that the first sub-combustion pit in a semi-ellipsoidal shape has a smaller curvature of the pit wall compared to the cylindrical pit or the semi-spherical pit in the related art, which is beneficial for the fluid to flow along the straight line on which the long axis of the first profile line is located, i.e., beneficial for the fluid to flow in the transverse direction, so that the fluid flowing into the first sub-combustion pit can better sweep out the residual exhaust gas in the first sub-combustion pit during the intake stage, and the phenomenon of easily forming a fluid flow dead zone due to the deep depth of the pit in the related art can be effectively avoided.

[0018] Secondly, by setting the first profile line formed by the pit wall of the first sub-combustion pit on the symmetry plane as a semi-ellipse, the center axis of the piston body and the straight line where the long axis of the first profile line is located are perpendicular and both are located on the symmetry plane, so that when the fluid flows into the first sub-combustion pit, the tumble flow is formed under the guidance of the pit wall of the first sub-combustion pit; the second sub-combustion pit is arranged between the first sub-combustion pit and the upper combustion pit and is connected with the first sub-combustion pit and the upper combustion pit, the second profile line is connected with the first end of the first profile line and is located on the side of the straight line where the short axis of the first profile line is located, specifically, the second profile line and the gas outlet of the intake port are distributed on the same side, in the compression stage, the tumble flow in the first sub-combustion pit goes up, the pit wall of the second sub-combustion pit can guide the fluid to further go up to form tumble flow, so as to further strengthen the tumble flow effect of the fluid, reduce the energy loss in the tumble flow process and improve the mixing uniformity of the fluid; when the piston body operates to the vicinity of the top dead center, the tumble flow is broken, the turbulent kinetic energy is greatly improved, and then the flame propagation speed and the thermal efficiency of the engine can be effectively improved.

[0019] Therefore, by adopting the engine piston, the exhaust gas remaining in the first sub-combustion pit can be better swept out in the intake stage, the phenomenon of easy formation of fluid flow dead zone caused by the deep depth of the pit is avoided, the tumble flow effect of the fluid can be better improved in the compression stage, the mixing uniformity of the fluid is improved, when the piston operates to the vicinity of the top dead center, the flame propagation speed and the thermal efficiency of the engine can be better improved.

[0020] On the other hand, the application also provides an engine, which comprises a cylinder, the cylinder comprising a cylinder body and a cylinder cover connected with each other, and the engine further comprises the engine piston described above, the piston body being arranged in the cavity formed by the cylinder body and the cylinder cover in the axial direction of the piston body, and a combustion chamber being formed between the combustion chamber pit and the cylinder cover.

[0021] As an optional solution of the engine, the cylinder cover is provided with a tangential intake port and a spiral intake port which are independent of each other, one end of the tangential intake port and one end of the spiral intake port are both connected with an intake manifold of the engine, and the other end of the tangential intake port and the other end of the spiral intake port are both connected with the combustion chamber.

[0022] The engine provided by the application has at least the following beneficial effects:

[0023] By adopting the engine piston, the exhaust gas remaining in the first sub-combustion pit can be better swept out in the intake stage, the phenomenon of fluid flow dead zone caused by the deep pit depth can be avoided, the fluid tumble effect can be better improved in the compression stage, the fluid mixing uniformity can be improved, the flame propagation speed can be better improved when the piston runs to the vicinity of the top dead center, and the thermal efficiency of the engine can be improved.

[0024] In another aspect, the present application also provides an engine control method for implementing the above-mentioned engine, and the engine control method comprises:

[0025] When the engine is in the first operating condition, the fuel injection parameters are determined according to the intake flow of the intake manifold, the engine speed and the engine torque, the fuel injection parameters include the first injection amount of fuel injected into the tangential air inlet, the second injection amount of fuel injected into the spiral air inlet, the first time period of fuel injection into the tangential air inlet, and the second time period of fuel injection into the spiral air inlet.

[0026] The first injection amount of fuel is injected into the tangential air inlet in the first time period, and the second injection amount of fuel is injected into the spiral air inlet in the second time period; the first injection amount of fuel is greater than the second injection amount of fuel.

[0027] As an optional solution of the above-mentioned engine control method, the specific steps of determining the first injection amount of fuel and the second injection amount of fuel according to the intake flow of the intake manifold, the engine speed and the engine torque comprise:

[0028] determining the total first fuel injection amount according to the current intake flow;

[0029] determining the first fuel injection proportion of the first injection amount of fuel in the total first fuel injection amount and the second fuel injection proportion of the second injection amount of fuel in the total first fuel injection amount according to the current engine speed and the current engine torque;

[0030] calculating the first injection amount of fuel and the second injection amount of fuel according to the total first fuel injection amount, the first fuel injection proportion and the second fuel injection proportion;

[0031] wherein the value of the first fuel injection proportion is greater than 60% and less than 75%, and the value of the second fuel injection proportion is greater than 25% and less than 40%.

[0032] As an optional solution of the above-mentioned engine control method, the start time of the first time period is earlier than the start time of the second time period.

[0033] The engine control method provided by the present application at least has the following beneficial effects:

[0034] The engine applying the engine control method can effectively relieve the phenomenon that fuel collides with the wall due to the mismatch between fuel injection amount and intake flow rate under high load operation conditions, effectively improve fuel atomization effect and mixing uniformity, and effectively improve flame propagation speed and engine thermal efficiency on the basis of ensuring charge efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A first structural schematic diagram of an engine piston is provided for an embodiment of the present application.

[0036] Figure 2 A second structural schematic diagram of an engine piston is provided for an embodiment of the present application.

[0037] Figure 3 A structural schematic diagram of an intake port along a first viewing angle is provided for an embodiment of the present application.

[0038] Figure 4 A structural schematic diagram of an intake port along a second viewing angle is provided for an embodiment of the present application.

[0039] Figure 5 A structural schematic diagram of an intake port along a third viewing angle is provided for an embodiment of the present application.

[0040] Figure 6 A first flowchart of an engine control method is provided for an embodiment of the present application.

[0041] Figure 7 A second flowchart of an engine control method is provided for an embodiment of the present application.

[0042] Figure 8 A simulation evolution diagram of tumble effect in a combustion chamber during a process in which a crank angle changes from 600°CA to 700°CA is provided for an embodiment of the present application.

[0043] Figure 9 A simulation diagram of tumble effect in a combustion chamber when a crank angle is 700°CA is provided for an embodiment of the present application.

[0044] Figure 10 A simulation evolution diagram of flame propagation effect in a combustion chamber during a process in which a crank angle changes from 710°CA to 740°CA is provided for an embodiment of the present application.

[0045] Figure 11 A broken line comparison diagram of turbulent kinetic energy before and after optimization is provided for an embodiment of the present application.

[0046] Figure 12 A broken line comparison diagram of non-uniformity coefficient before and after optimization is provided for an embodiment of the present application.

[0047] Figure 13 The broken line contrast chart of the exothermic rate before and after optimization provided for the embodiment of the present application.

[0048] In the figure:

[0049] 1, piston body; 11, top surface; 12, combustion chamber pit; 121, lower combustion pit; 1211, first sub-combustion pit; 1212, second sub-combustion pit; 122, upper combustion pit;

[0050] 2, tangential intake port; 3, spiral intake port; 4, first mounting hole; 5, second mounting hole; 6, exhaust port. DETAILED DESCRIPTION

[0051] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0052] In the description of the present application, it should be noted that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", are only for the purpose of description, and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and moreover, the "above", "above" and "above" of the first feature to the second feature include the vertical height of the first feature above and obliquely above the second feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The "below", "below" and "below" of the first feature to the second feature include the vertical height of the first feature below and obliquely below the second feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0053] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0054] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0055] This invention provides an engine piston, such as Figure 1 As shown, the engine piston includes a piston body 1. The piston body 1 has a top surface 11 perpendicular to its own axial direction and a combustion chamber recess 12 recessed in the top surface 11. The combustion chamber recess 12 includes a lower combustion recess 121 and an upper combustion recess 122 sequentially distributed along the axial direction of the piston body 1. The lower combustion recess 121 includes a first sub-combustion recess 1211 and a second sub-combustion recess 1212. The second sub-combustion recess 1212 is disposed between the first sub-combustion recess 1211 and the upper combustion recess 122, and connects the first sub-combustion recess 1211 and the upper combustion recess 122. The upper combustion recess 122 is used to guide fluid through the second sub-combustion recess 1212 into the first... The lower combustion pit 1211 is symmetrical about a plane of symmetry. The first lower combustion pit 1211 is semi-ellipsoidal, and the contour line of the pit wall of the first lower combustion pit 1211 on the plane of symmetry is the first contour line, which is semi-elliptical. The central axis of the piston body 1 and the major axis of the first contour line are perpendicular and both lie on the plane of symmetry. The contour line of the pit wall of the second lower combustion pit 1212 on the plane of symmetry is the second contour line. The second contour line is connected to the first end of the first contour line and is oriented on one side of the minor axis of the first contour line. Both the second contour line and the first contour line are curves of the same ellipse, and their orientation is parallel to the major axis of the first contour line. It can be understood that, along the axial direction of the piston body 1, one end of the contour line formed by the lower combustion pit 121 on the plane of symmetry is below the other end.

[0056] By setting the first sub-combustion recess 1211 to be semi-ellipsoidal, the first contour line formed by the recess wall of the first sub-combustion recess 1211 on the plane of symmetry is semi-elliptical. The central axis of the piston body 1 and the long axis of the first contour line are perpendicular to each other and both are located on the plane of symmetry. It can be understood that, compared with the cylindrical or hemispherical recesses in related technologies, the semi-ellipsoidal first sub-combustion recess 1211 has a smaller curvature of the recess wall, which is conducive to the flow of fluid along the long axis of the first contour line, that is, it is conducive to the flow of fluid in the lateral direction. Thus, during the intake stage, the fluid flowing into the first sub-combustion recess 1211 can better sweep out the residual exhaust gas in the first sub-combustion recess 1211, and can effectively avoid the phenomenon of fluid flow dead zone caused by the deep recess in related technologies.

[0057] Secondly, the first profile line formed by the pit wall of the first sub-combustion pit 1211 on the symmetry plane is a semi-ellipse, the central axis of the piston body 1 and the straight line on which the long axis of the first profile line is located are perpendicular and are both located on the symmetry plane, so that when the fluid flows into the first sub-combustion pit 1211, the tumble flow is formed under the guidance of the pit wall of the first sub-combustion pit 1211; the second sub-combustion pit 1212 is arranged between the first sub-combustion pit 1211 and the upper combustion pit 122 and is connected with the first sub-combustion pit 1211 and the upper combustion pit 122, the second profile line is connected with the first end of the first profile line and is located on the side of the straight line on which the short axis of the first profile line is located, specifically, the second profile line and the air outlet of the intake port are distributed on the same side, in the compression stage, the fluid in the first sub-combustion pit 1211 forms the tumble flow and moves upward, the pit wall of the second sub-combustion pit 1212 can guide the fluid to further move upward to form the tumble flow, so that the tumble flow effect of the fluid can be further enhanced, the energy loss in the tumble flow process is reduced, and the mixing uniformity of the fluid is improved; when the piston body 1 operates to the vicinity of the top dead center, the tumble flow is broken, the turbulent kinetic energy is greatly improved, and then the flame propagation speed and the thermal efficiency of the engine can be effectively improved.

[0058] Therefore, by adopting the engine piston, the exhaust gas remaining in the first sub-combustion pit 1211 can be better swept out in the intake stage, the phenomenon that the fluid flow dead zone is easily formed due to the deep depth of the pit is avoided, the tumble flow effect of the fluid can be better improved in the compression stage, the mixing uniformity of the fluid is improved, when the piston operates to the vicinity of the top dead center, the flame propagation speed and the thermal efficiency of the engine can be better improved.

[0059] Specifically, the fluid is the mixed gas of air and fuel. In the embodiment, the fuel is methanol. In other embodiments, the fuel can also be liquid ammonia or methane and other clean fuels.

[0060] Specifically, the tumble flow refers to the rotating flow phenomenon of the fluid in the combustion chamber. The turbulent kinetic energy refers to the average value of the turbulent pulsation kinetic energy of unit mass of fluid.

[0061] In the example, in the embodiment, the central axis of the first sub-combustion pit 1211 is collinear with the central axis of the piston body 1. In other embodiments, the central axis of the first sub-combustion pit 1211 can also be arranged in parallel with the central axis of the piston body 1.

[0062] In the example, in the embodiment, the bottom surface of the piston body 1 is a plane and is perpendicular to the axial direction of the piston body 1. In other embodiments, the bottom surface of the piston body 1 can also be a curved surface according to actual working condition requirements.

[0063] Optionally, in the embodiment, the intersection line of the second sub-combustion pocket 1212 and the first sub-combustion pocket 1211 is a first intersection line, and all points on the first intersection line are located on the same plane; the intersection line of the second sub-combustion pocket 1212 and the upper combustion pocket 122 is a second intersection line, and all points on the second intersection line are located on the same plane; the first intersection line and the second intersection line intersect at the second end of the first contour line. In this way, the end face where the opening of the second sub-combustion pocket 1212 is located is a plane, and the plane is arranged at an angle with the central axis of the first sub-combustion pocket 1211. Compared with arranging the end face where the opening of the second sub-combustion pocket 1212 is located as an arc face or a stepped face, the processing difficulty of the second sub-combustion pocket 1212 can be reduced on the basis of further improving the tumble effect. In other embodiments, the end face where the opening of the second sub-combustion pocket 1212 is located can also be arranged as an arc face or a stepped face according to actual working condition requirements.

[0064] Optionally, as shown in Figure 1 , the upper combustion pocket 122 is in the shape of a truncated cone, the small end of the upper combustion pocket 122 communicates with the second sub-combustion pocket 1212, and the central axis of the upper combustion pocket 122 is perpendicular to the plane where the second intersection line is located. Specifically, as shown in Figure 1 and Figure 2 , the contour line of the pocket wall of the upper combustion pocket 122 on the symmetry plane includes a third contour line connected with the second end of the first contour line and a fourth contour line connected with the second contour line, the angle between the third contour line and the top surface 11 is α, and the angle between the fourth contour line and the top surface 11 is β. Since the top surface 11 is perpendicular to the central axis of the piston body 1, and the central axis of the upper combustion pocket 122 is perpendicular to the plane where the second intersection line is located, α is greater than β. That is, the inclination angle of the third contour line is relatively large.

[0065] Based on the fact that the second contour line and the gas outlet of the intake port are distributed on the same side, the angle α is relatively large. After the mixed gas flows into the combustion chamber pocket 12, the pocket wall of the upper combustion pocket 122 can guide the mixed gas to flow more easily to the central area of the combustion chamber pocket 12, thereby further improving the tumble effect of the mixed gas and the mixing uniformity of the mixed gas; when the piston body 1 operates near the top dead center, the turbulent kinetic energy can be further improved, thereby further improving the flame propagation speed and further improving the thermal efficiency of the engine.

[0066] The angle β is relatively small, so that an inclined fourth contour line can be formed to ensure that the pocket wall of the upper combustion pocket 122 can guide the mixed gas to flow from the upper combustion pocket 122 into the first sub-combustion pocket 1211 through the second sub-combustion pocket 1212.

[0067] Exemplarily, in the embodiment, the value range of a is 10°-50°. This is to ensure that the inclination angle of the third profile line is relatively large, so as to ensure that the mixed gas can flow more easily to the center area of the combustion chamber pit 12, and when the piston body 1 is running near the top dead center, the turbulent energy can be further improved.

[0068] Exemplarily, in the embodiment, the value range of β is 0°-30°. This is to ensure that the mixed gas can be guided to flow from the upper combustion pit 122 to the first sub-combustion pit 1211 through the second sub-combustion pit 1212.

[0069] It can be understood that the value of a can be adaptively set to 10°, 15°, 20°, 30°, 40°, or 50°, etc. according to actual working condition requirements. The value of β can be adaptively set to 10°, 15°, 20°, 25°, or 30°, etc. according to actual working condition requirements. The value range of the value range of the value range of a and the value range of the value range of β are both the experience ranges obtained from a large number of previous tests.

[0070] Specifically, as shown in Figure 1 and Figure 2 The distance between the first intersection point of the third profile line and the top surface 11 and the second intersection point of the fourth profile line and the top surface 11 is L1; the length of the projection of the third profile line on the plane where the top surface 11 is located along the axial direction of the piston body 1 is L2, and the length of the projection of the fourth profile line on the plane where the top surface 11 is located along the axial direction of the piston body 1 is L3.

[0071] Exemplarily, in the embodiment, L2=(0.1-0.2)L1, and L3=(0.1-0.2)L1. This is to further ensure that the inclination angle of the third profile line is relatively large, and further ensure that the inclination angle of the fourth profile line is relatively small. For the third profile line, the tumble effect of the mixed gas can be further improved, and the mixing uniformity of the mixed gas can be improved; when the piston body 1 is running near the top dead center, the turbulent energy can be further improved, so as to further improve the flame propagation speed and further improve the thermal efficiency of the engine. For the fourth profile line, the intake efficiency of guiding the mixed gas to flow from the upper combustion pit 122 to the first sub-combustion pit 1211 through the second sub-combustion pit 1212 can be further ensured.

[0072] It can be understood that the value of L2 can be adaptively set to 0.1L1, 0.15L1, or 0.2L1, etc. according to actual working condition requirements. The value of L3 can be adaptively set to 0.1L1, 0.15L1, or 0.2L1, etc. according to actual working condition requirements. The value range of the value range of L2 and the value range of the value range of L3 are both the experience ranges obtained from a large number of previous tests.

[0073] Specifically, as shown in Figure 1 and Figure 2As shown, the diameter of the piston body 1 is D1; the distance between the first intersection point of the third profile line and the top surface 11 and the second intersection point of the fourth profile line and the top surface 11 is L1.

[0074] Optionally, D1>L1. In this way, the structural strength of the piston body 1 is ensured, the risk of forming hot spots on the top of the pit wall of the combustion chamber pit 12 is reduced, and the structural strength of the piston body 1 is improved. The hot spot refers to a region with an abnormally high local temperature in the combustion chamber.

[0075] For example, in this embodiment, L1=(0.7-0.9)D1. It can be understood that the value of L1 can be adaptively set to 0.7D1, 0.8D1, 0.85D1 or 0.9D1 according to actual working condition requirements. The value range of L1 is an experience range obtained from a large number of previous tests.

[0076] In other embodiments, D=L1 can also be set; further, the pit wall of the upper combustion pit 122 is connected to the outer peripheral surface of the piston body 1 through a circular arc chamfer surface. This can also reduce the risk of forming hot spots on the top of the pit wall of the combustion chamber pit 12, and can increase the opening area of the combustion chamber pit 12 to further improve the intake efficiency.

[0077] Specifically, as shown in Figure 1 and Figure 2 the minimum distance between the first intersection point and the outer peripheral wall of the piston body 1 is L4, and the minimum distance between the second intersection point and the outer peripheral wall of the piston body 1 is L5.

[0078] Further optionally, in this embodiment, L4

[0079] Specifically, the communication between the lower combustion pit 121 and the upper combustion pit 122 forms a throat. Further, the pit wall of the lower combustion pit 121 and the pit wall of the upper combustion pit 122 are connected through a circular arc chamfer surface. This can improve the smoothness of the fluid passing through the throat, and can effectively reduce the risk of forming hot spots at the throat.

[0080] wherein, as shown in Figure 1 and Figure 2As shown, the diameter of the piston body 1 is D1, the long axis length of the first sub-combustion pit 1211 is D2, and the short axis length of the first sub-combustion pit 1211 is D3.

[0081] Exemplarily, in the embodiment, D2=(0.55-0.75)D1, and D3=(0.4-0.55)D1. D2=(0.55-0.75)D1 is configured to enable the fluid to flow into the first sub-combustion pit 1211 more smoothly, and D3=(0.4-0.55)D1 is configured to reduce the friction between the mixed gas and the pit wall of the first sub-combustion pit 1211, fully utilize the flow guiding effect of the pit wall of the first sub-combustion pit 1211 to form tumble flow, and further improve the tumble flow effect. It can be understood that the value of D2 can be adaptively set to 0.55D1, 0.6D1, 0.65D1, 0.7D1 or 0.75D1 according to actual working condition requirements. The value of D3 can be adaptively set to 0.4D1, 0.45D1, 0.5D1 or 0.55D1 according to actual working condition requirements. The value range of D2 and the value range of D3 are both experience ranges obtained from a large number of previous tests.

[0082] The application further provides an engine, which comprises a cylinder including a cylinder body and a cylinder cover connected together, and further comprises the engine piston described above, wherein the piston body 1 is arranged in the cavity formed by the cylinder body and the cylinder cover in the axial direction of the piston body 1, and the combustion chamber pit 12 and the cylinder cover form a combustion chamber. By using the engine piston described above, the exhaust gas remaining in the first sub-combustion pit 1211 can be better swept out during the intake stage, the phenomenon of fluid flow dead zone caused by the deep depth of the pit can be avoided, the tumble flow effect of the fluid can be better improved during the compression stage, the mixing uniformity of the fluid can be improved, the flame propagation speed can be better improved when the piston runs to the vicinity of the top dead center, and the thermal efficiency of the engine can be improved.

[0083] In the embodiment, as shown in the figure, Figures 3-5 The cylinder cover is provided with a tangential intake passage 2 and a spiral intake passage 3 which are independent of each other, one end of the tangential intake passage 2 and one end of the spiral intake passage 3 are both in communication with the intake manifold of the engine, and the other end of the tangential intake passage 2 and the other end of the spiral intake passage 3 are both in communication with the combustion chamber. Specifically, when the engine takes in air, the air is divided into two parts, the first part of the air flows into the combustion chamber through the tangential intake passage 2, and the second part of the air flows into the combustion chamber through the spiral intake passage 3 at the same time. Further specifically, the tangential intake passage 2 has the characteristics of large flow rate, low flow resistance and high charging efficiency, and the spiral intake passage 3 has the characteristic of being able to form strong vortex flow. The specific structures of the tangential intake passage 2 and the spiral intake passage 3 both belong to the prior art, and thus will not be described here.

[0084] Exemplarily, in the embodiment, one end of the tangential air inlet 2 and one end of the spiral air inlet 3 are directly communicated with an air intake manifold, and the air intake manifold is communicated with an air intake main pipe. Air flows from the air intake main pipe to the air intake manifold, and is then divided into two parts to flow into the combustion chamber through the tangential air inlet 2 and the spiral air inlet 3 respectively.

[0085] In the embodiment, the engine further comprises a first injector and a second injector arranged on the cylinder head, the injection end of the first injector extends into the tangential air inlet 2 for injecting fuel into the tangential air inlet 2, and the injection end of the second injector extends into the spiral air inlet 3 for injecting fuel into the spiral air inlet 3. Further, in the embodiment, as shown in the figure, the cylinder head is provided with a first mounting hole 4 communicated with the tangential air inlet 2 and a second mounting hole 5 communicated with the spiral air inlet 3; the first injector is mounted on the cylinder head through the first mounting hole 4, and the injection end of the first injector extends into the tangential air inlet 2; and the second injector is mounted on the cylinder head through the second mounting hole 5, and the injection end of the second injector extends into the spiral air inlet 3. Figure 5

[0086] In the embodiment, the fuel injected by the first injector and the second injector is methanol, that is, the engine in the embodiment is a methanol engine.

[0087] Optionally, the fuel injection direction of the first injector is distributed at an acute angle with the flow direction of the gas flowing through the tangential air inlet 2. This can make the fuel injected by the first injector into the tangential air inlet 2 better mixed with the air in the tangential air inlet 2, thereby improving the mixing effect; and secondly, it can effectively alleviate the wall attachment phenomenon caused by the fuel injected by the first injector colliding with the wall surface of the tangential air inlet 2, thereby effectively improving the atomization effect of the fuel injected by the first injector. It can be understood that the included angle between the fuel injection direction of the first injector and the flow direction of the gas flowing through the tangential air inlet 2 can be set to 45°, 50° or 60°, etc. according to actual working condition requirements.

[0088] Optionally, the fuel injection direction of the second injector is distributed at an acute angle with the flow direction of the gas flowing through the spiral air inlet 3. This can make the fuel injected by the second injector into the spiral air inlet 3 better mixed with the air in the spiral air inlet 3, thereby improving the mixing effect; and secondly, it can effectively alleviate the wall attachment phenomenon caused by the fuel injected by the second injector colliding with the wall surface of the spiral air inlet 3, thereby effectively improving the atomization effect of the fuel injected by the second injector. It can be understood that the included angle between the fuel injection direction of the second injector and the flow direction of the gas flowing through the spiral air inlet 3 can be set to 45°, 50° or 60°, etc. according to actual working condition requirements.

[0089] Specifically, as shown in the figure, Figures 3-5 ​As shown, the cylinder head is also provided with an exhaust passage 6 for exhaust. The passages on the cylinder head include the tangential intake passage 2, the spiral intake passage 3 and the exhaust passage 6, and the intake passages include the tangential intake passage 2 and the spiral intake passage 3. The specific structure of the exhaust passage 6 belongs to the prior art, and thus will not be described here.

[0090] Since the tangential intake passage 2, the spiral intake passage 3 and the exhaust passage 6 are all virtual bodies, Figures 3-5 The tangential intake passage 2 indicated in the middle is used to reflect the profile of the tangential intake passage 2, Figures 3-5 The spiral intake passage 3 indicated in the middle is used to reflect the profile of the spiral intake passage 3, Figures 3-5 The exhaust passage 6 indicated in the middle is used to reflect the profile of the exhaust passage 6. Further, since the first mounting hole 4 is in communication with the tangential intake passage 2, and the second mounting hole 5 is in communication with the spiral intake passage 3, Figure 5 The first mounting hole 4 indicated in the middle is used to reflect the profile of the first mounting hole 4, Figure 5 The second mounting hole 5 indicated in the middle is used to reflect the profile of the second mounting hole 5.

[0091] In this embodiment, the intake manifold is provided with an intake flow sensor for monitoring the intake flow of the intake manifold.

[0092] In this embodiment, the cylinder head is also provided with a pressure sensor electrically connected to the controller, and the pressure sensor is used to monitor the cylinder pressure. The cylinder pressure refers to the pressure in the combustion chamber when the piston of the engine moves to the compression top dead center.

[0093] Further specifically, the intake flow sensor, the pressure sensor, the first injector and the second injector are all electrically connected to the controller, the controller can receive the intake flow monitored by the intake flow sensor and the cylinder pressure monitored by the pressure sensor, and the controller can control the first injector and the second injector to inject fuel. In this embodiment, the controller is a vehicle controller.

[0094] The application also provides an engine control method, as shown in the figure, the engine control method comprises: Figures 1-7 As shown, the engine control method comprises:

[0095] S100, when the engine is running, the running condition of the engine is judged in real time. Wherein, the running condition of the engine includes the first running condition and the second running condition; the load of the engine in the first running condition is greater than the load of the engine in the second running condition. Specifically, the first running condition refers to the high load running condition of the engine, and the second running condition refers to the low load running condition of the engine.

[0096] Specifically, when the load of the engine is greater than or equal to the preset load percentage, the engine is in a high load operating condition, i.e., the engine is in a first operating condition; when the load of the engine is less than the preset load percentage, the engine is in a low load operating condition, i.e., the engine is in a second operating condition. In the embodiment, the preset load percentage is set to be 30% as an example. The preset load percentage is an empirical value obtained from a large number of previous tests.

[0097] Specifically, the engine load refers to the ratio of the actual output of the engine to the maximum output at a specific speed, and the output refers to power or torque, etc. The engine load percentage refers to the ratio of the actual output torque of the engine to the maximum torque of the engine when the throttle is fully open at a specific speed, expressed in percentage.

[0098] If the engine is in the first operating condition, steps S200 and S300 are performed.

[0099] S200, determining the fuel injection parameters according to the intake flow of the intake manifold, the engine speed and the engine torque, the fuel injection parameters including the first fuel injection amount injected into the tangential air inlet 2, the second fuel injection amount injected into the spiral air inlet 3, the first time period of injecting fuel into the tangential air inlet 2, and the second time period of injecting fuel into the spiral air inlet 3.

[0100] S300, injecting the first fuel injection amount of fuel into the tangential air inlet 2 in the first time period, and injecting the second fuel injection amount of fuel into the spiral air inlet 3 in the second time period; the first fuel injection amount is greater than the second fuel injection amount.

[0101] If the engine is in the second operating condition, steps S400 and S500 are performed.

[0102] S400, determining the total second fuel injection amount injected into the tangential air inlet 2 according to the intake flow of the intake manifold, and determining the third time period of injecting fuel into the tangential air inlet 2 according to the engine speed and the engine torque.

[0103] S500, injecting the total second fuel injection amount of fuel into the tangential air inlet 2 in the third time period.

[0104] Specifically, when the engine is in a low load operating condition, the throttle opening degree is small, the air intake amount is small, and the fuel injection amount to be injected is small, while when the engine is in a high load operating condition, the throttle opening degree is large, the air intake amount is large, and the fuel injection amount to be injected is large.

[0105] Since the fuel and air required by the engine when running at low load are both small, when the engine is running at low load, by controlling the fuel injection amount of the second fuel injection total amount into the tangential intake port 2 in the third time period according to the intake flow of the intake manifold, the engine speed and the engine torque, the fuel injection amount can be ensured to meet the engine operation, and the additional energy consumption caused by simultaneously starting the first injector and the second injector can be avoided, and since the tangential intake port 2 has the characteristics of large flow, low flow resistance and high charging efficiency, the air in the tangential intake port 2 can mix with the fuel injected by the first injector and drive the fuel injected by the first injector to flow into the combustion chamber of the engine quickly and efficiently, thereby effectively alleviating the phenomenon of fuel colliding with the wall in the tangential intake port 2 and causing wall attachment on the basis of ensuring the charging efficiency; secondly, by using the above-mentioned engine piston, when the engine is running at low load, the mixing uniformity of the mixture in the combustion chamber can be further improved on the basis of ensuring the charging efficiency, and the flame propagation speed in the combustion chamber can be improved.

[0106] Since the engine high load operation requires more fuel and air, the engine high load operation controls the first fuel injection amount to the tangential intake port 2 in the first time period and the second fuel injection amount to the spiral intake port 3 in the second time period according to the intake flow of the intake manifold, the engine speed and the engine torque. It can be understood that under this operating condition, each time the fuel is injected, the fuel is divided into two parts for injection, the first part of the fuel is injected into the tangential intake port 2 by the first injector, mixed with the air in it and flows into the combustion chamber of the engine, and the second part of the fuel is injected into the spiral intake port 3 by the second injector, mixed with the air in it and flows into the combustion chamber of the engine. Compared with the related art, the fuel injection amount injected into the tangential intake port 2 in this embodiment is less than the total fuel injection amount, and the fuel injection amount injected into the spiral intake port 3 is less than the total fuel injection amount, thereby effectively alleviating the phenomenon that the fuel is easy to collide with the wall and cause wall attachment due to the mismatch between the fuel injection amount and the intake flow caused by injecting a large amount of fuel into one intake port in the related art, effectively improving the atomization effect of the fuel injected into the tangential intake port 2, and effectively improving the atomization effect of the fuel injected into the spiral intake port 3. In addition, by setting the first fuel injection amount injected into the tangential intake port 2 to be greater than the second fuel injection amount injected into the spiral intake port 3, the characteristics of the tangential intake port 2 of large flow, low flow resistance and high charging efficiency and the characteristics of the spiral intake port 3 of being able to form strong vortex are effectively utilized. Specifically, the tangential intake port 2 has the characteristics of large flow, low flow resistance and high charging efficiency, and the efficiency of transporting the mixed gas of air and fuel into the combustion chamber of the engine is high, so as to further alleviate the phenomenon that the fuel is easy to collide with the wall and cause wall attachment in the tangential intake port 2 due to the mismatch between the fuel injection amount and the intake flow on the basis of ensuring the charging efficiency; the spiral intake port 3 has the characteristic of being able to form strong vortex, which can effectively improve the mixing effect of the air and fuel flowing into the combustion chamber, and since the amount of fuel injected into the spiral intake port 3 is small, the phenomenon that the fuel is easy to collide with the wall and cause wall attachment in the spiral intake port 3 due to the mismatch between the fuel injection amount and the intake flow can be further effectively alleviated. Secondly, by using the above-mentioned engine piston, the engine high load operation can further improve the mixing uniformity of the mixed gas in the combustion chamber on the basis of ensuring the charging efficiency, and improve the flame propagation speed in the combustion chamber.

[0107] Further, the fuel injection direction of the first injector is distributed at an acute angle with the flow direction of the gas flowing through the tangential intake port 2, so that the fuel injected into the tangential intake port 2 by the first injector can better mix with the air in the tangential intake port 2 to improve the mixing effect, and further alleviate the wall attachment phenomenon caused by the fuel injected by the first injector colliding with the wall of the tangential intake port 2. It should be noted that the flow direction of the gas flowing through the tangential intake port 2 here refers to the flow direction of the gas at the first injector in the tangential intake port 2.

[0108] Further, the fuel injection directions of the second injectors are distributed at acute angles with the flow direction of the gas flowing through the helical intake passage 3, so that the fuel injected by the second injectors into the helical intake passage 3 can be better mixed with the air in the helical intake passage 3 to improve the mixing effect, and the wall-attaching phenomenon caused by the fuel injected by the second injectors colliding with the wall of the helical intake passage 3 can be further alleviated. It should be noted that the flow direction of the gas flowing through the helical intake passage 3 here refers to the flow direction of the gas at the second injectors in the helical intake passage 3.

[0109] Therefore, by adopting the engine control method, the wall-attaching phenomenon caused by the fuel colliding with the wall due to the mismatch between the fuel injection amount and the intake flow rate can be effectively alleviated on the basis of ensuring the charge efficiency during the entire operation of the engine, the fuel atomization effect and the mixing uniformity can be effectively improved, and the flame propagation speed in the combustion chamber can be effectively improved; secondly, the additional energy consumption can be effectively avoided.

[0110] As shown in FIGS. 1, 2 and 3, the engine control method comprises the following steps: Figure 6 and Figure 7 As shown in FIGS. 1, 2 and 3, the engine control method comprises the following steps:

[0111] S211, determining the first fuel injection total amount according to the current intake flow rate.

[0112] Specifically, the first fuel injection total amount is obtained by searching a first table according to the current intake flow rate, and the first table is formed by the intake flow rate and the first fuel injection total amount. The first table is an experience table obtained by a large number of tests in the early stage. As an alternative, the first fuel injection total amount is obtained by searching a first Map according to the current intake flow rate, and the first Map is formed by the intake flow rate and the first fuel injection total amount. The first Map is an experience Map obtained by a large number of tests in the early stage.

[0113] S212, determining the first fuel injection ratio of the first fuel injection amount to the first fuel injection total amount and the second fuel injection ratio of the second fuel injection amount to the first fuel injection total amount according to the current engine speed and the current engine torque.

[0114] Specifically, the ratio of the first fuel injection ratio to the second fuel injection ratio is obtained according to the current engine speed and the current engine torque from a second table formed by engine speed, engine torque and the ratio of the first fuel injection ratio to the second fuel injection ratio. The second table is an empirical table obtained from a large number of previous tests. Alternatively, the ratio of the first fuel injection ratio to the second fuel injection ratio is obtained according to the current engine speed and the current engine torque from a second map formed by engine speed, engine torque and the ratio of the first fuel injection ratio to the second fuel injection ratio. The second map is an empirical map obtained from a large number of previous tests.

[0115] S213, calculating the first fuel injection amount and the second fuel injection amount according to the total first fuel injection amount, the first fuel injection ratio and the second fuel injection ratio.

[0116] Specifically, the first fuel injection amount = the total first fuel injection amount x the first fuel injection ratio; and the second fuel injection amount = the total first fuel injection amount x the second fuel injection ratio.

[0117] For the combustion chamber recess 12 of the present embodiment, the first fuel injection ratio is greater than 60% and less than 75%, and the second fuel injection ratio is greater than 25% and less than 40%. It can be understood that the values of the first fuel injection ratio and the second fuel injection ratio are different for combustion chamber recesses 12 of different shapes and size specifications.

[0118] The specific steps of determining the first time period and the second time period in step S200 according to the intake flow rate of the intake manifold, the engine speed and the engine torque include:

[0119] The first crank angle corresponding to the start of fuel injection into the tangential intake port 2, the first crank angle change corresponding to the duration of fuel injection into the tangential intake port 2, the second crank angle corresponding to the start of fuel injection into the spiral intake port 3, and the second crank angle change corresponding to the duration of fuel injection into the spiral intake port 3 are determined according to the current engine speed and the current engine torque. The first time period is determined according to the first crank angle and the first crank angle change; and the second time period is determined according to the second crank angle and the second crank angle change.

[0120] Specifically, the first crank angle is obtained according to the current engine speed and the current engine torque from a third table formed by engine speed, engine torque and the first crank angle. The third table is an empirical table obtained from a large number of previous tests. Alternatively, the first crank angle is obtained according to the current engine speed and the current engine torque from a third map formed by engine speed, engine torque and the first crank angle. The third map is an empirical map obtained from a large number of previous tests.

[0121] Specifically, the first crank angle change amount is obtained by referring to a fourth table according to the current engine speed and the current engine torque, the fourth table being formed by the engine speed, the engine torque and the first crank angle change amount. The fourth table is an experience table obtained by a large number of experiments in the past. As an alternative, the first crank angle change amount is obtained by referring to a fourth map according to the current engine speed and the current engine torque, the fourth map being formed by the engine speed, the engine torque and the first crank angle change amount. The fourth map is an experience map obtained by a large number of experiments in the past.

[0122] Specifically, the second crank angle is obtained by referring to a fifth table according to the current engine speed and the current engine torque, the fifth table being formed by the engine speed, the engine torque and the second crank angle. The fifth table is an experience table obtained by a large number of experiments in the past. As an alternative, the second crank angle is obtained by referring to a fifth map according to the current engine speed and the current engine torque, the fifth map being formed by the engine speed, the engine torque and the second crank angle. The fifth map is an experience map obtained by a large number of experiments in the past.

[0123] Specifically, the second crank angle change amount is obtained by referring to a sixth table according to the current engine speed and the current engine torque, the sixth table being formed by the engine speed, the engine torque and the second crank angle change amount. The sixth table is an experience table obtained by a large number of experiments in the past. As an alternative, the second crank angle change amount is obtained by referring to a sixth map according to the current engine speed and the current engine torque, the sixth map being formed by the engine speed, the engine torque and the second crank angle change amount. The sixth map is an experience map obtained by a large number of experiments in the past.

[0124] As an alternative, the above tables can be combined into one table. The above maps can be combined into one map.

[0125] It can be understood that the crank angle corresponding to the first time period start time is the first crank angle, and the crank angle corresponding to the second time period start time is the second crank angle.

[0126] It can be understood that, since the first crank angle corresponding to the start of each fuel injection into the tangential intake port 2 and the first crank angle change amount corresponding to the duration of each fuel injection into the tangential intake port 2 are determined, the fuel injection pressure of each fuel injection into the tangential intake port 2 by the first injector is fixed. Since the second crank angle corresponding to the start of each fuel injection into the spiral intake port 3 and the second crank angle change amount corresponding to the duration of each fuel injection into the spiral intake port 3 are determined, the fuel injection pressure of each fuel injection into the spiral intake port 3 by the second injector is fixed.

[0127] In other embodiments, the first crank angle corresponding to the start of fuel injection into the tangential intake port 2, the third crank angle corresponding to the end of fuel injection into the tangential intake port 2, the second crank angle corresponding to the start of fuel injection into the spiral intake port 3, and the fourth crank angle corresponding to the end of fuel injection into the spiral intake port 3 can also be obtained by looking up a table or a map; the first time period is determined according to the first crank angle and the third crank angle, and the second time period is determined according to the second crank angle and the fourth crank angle.

[0128] Specifically, in the present embodiment, steps S211 to S213 and the step of determining the first time period and the second time period are preferably executed simultaneously to improve efficiency. In other embodiments, steps S211 to S213 are executed first, and then the step of determining the first time period and the second time period is executed; or, the step of determining the first time period and the second time period is executed first, and then steps S211 to S213 are executed.

[0129] In this way, when the engine is in the first operating condition, the phenomenon of fuel colliding with the wall and adhering to the wall due to the mismatch between the fuel injection amount and the intake flow rate caused by the relatively large amount of fuel injected into one intake port in the related art can be effectively alleviated while ensuring the charge efficiency. In addition, especially for the spiral intake port 3, the mixing effect of air and fuel in the spiral intake port 3 can be effectively improved, the phenomenon of fuel colliding with the wall and adhering to the wall in the spiral intake port 3 can be alleviated, and the mixing effect of air and fuel after flowing into the combustion chamber can be effectively improved.

[0130] Preferably, the start time of the first time period is earlier than the start time of the second time period. That is, the first crank angle is less than the second crank angle. It can be understood that, when the engine is in the first operating condition, the first injector starts to inject fuel into the tangential intake port 2 first and injects relatively more fuel, the second injector starts to inject fuel into the spiral intake port 3 later and injects relatively less fuel, forming an asynchronous injection mode of "early injection and more injection in the tangential intake port 2, and late injection and less injection in the spiral intake port 3".

[0131] For "early injection and more injection in the tangential intake port 2", the characteristics of large flow rate, low flow resistance, and high charge efficiency of the tangential intake port 2 can be better utilized, so that the phenomenon of fuel colliding with the wall and adhering to the wall in the tangential intake port 2 due to the mismatch between the fuel injection amount and the intake flow rate can be further alleviated while ensuring the charge efficiency.

[0132] Due to the relatively short penetration distance of the spiral intake passage 3, the "spiral intake passage 3 late injection and less injection" is arranged, which can further alleviate the phenomenon of fuel colliding with the wall and causing wall attachment in the spiral intake passage 3 on the basis of better playing the characteristics of the spiral intake passage 3 forming strong vortex. Secondly, it can further alleviate the phenomenon of fuel colliding with the wall and causing wall attachment in the spiral intake passage 3 due to the mismatch between fuel injection quantity and intake flow.

[0133] Therefore, by thus arranging, the tangential intake passage 2 and the spiral intake passage 3 can better match the structural characteristics of themselves, so that the fuel in the tangential intake passage 2 can better match the penetration distance of the tangential intake passage 2, and the fuel in the spiral intake passage 3 can better match the penetration distance of the spiral intake passage 3, further alleviating the phenomenon of fuel colliding with the wall and causing wall attachment in the intake passage due to the mismatch between fuel injection quantity and intake flow. Secondly, by thus arranging, the mixed gas of fuel and air in the tangential intake passage 2 and the mixed gas of fuel and air in the spiral intake passage 3 can flow into the combustion chamber roughly synchronously, further playing the characteristics of the spiral intake passage 3 forming strong vortex, so that the fuel and air flowing into the combustion chamber can be better mixed, and the distribution uniformity of the mixed gas in the combustion chamber can be improved, thereby effectively improving the effect of fuel mixed combustion in the cylinder. The penetration distance refers to the farthest distance that the fuel can move in the injection direction.

[0134] For the combustion chamber recess 12 of the embodiment, the first crank angle is in the range of 330°CA-380°CA, and the absolute value of the difference between the first crank angle and the second crank angle is in the range of 10°CA-50°CA. To ensure that the first crank angle is less than the second crank angle, and to limit the fuel injection time when the first injector starts to inject fuel, and the fuel injection time when the second injector starts to inject fuel. Specifically, the crank angle range of one working cycle of the engine is 0°CA-720°CA, and 0°CA is the crank angle corresponding to the top dead center.

[0135] It can be understood that for combustion chamber recesses 12 of different shapes and size specifications, the value range of the first crank angle is different, the value of the first crank angle is different, the value of the second crank angle is different, the value of the first crank angle change is different, and the value of the second crank angle change is different.

[0136] Specifically, when the engine is in the first operating condition, if the cylinder pressure of the engine is greater than the maximum value of the first cylinder pressure range, although the in-cylinder combustion effect of the engine is better at this time, the engine has hidden dangers such as knock, knock and / or mechanical damage, and if the cylinder pressure of the engine is less than the minimum value of the first cylinder pressure range, there are hidden dangers such as insufficient in-cylinder combustion of the engine and decline of engine power performance. Wherein, the first cylinder pressure range is an empirical value obtained from a large number of previous tests. Therefore, in order to avoid the above-mentioned hidden dangers, the engine control method preferably further comprises:

[0137] When the engine is in the first operating condition, the cylinder pressure of the engine is obtained in real time.

[0138] Determine whether the cylinder pressure is within the first cylinder pressure range.

[0139] If the cylinder pressure is within the first cylinder pressure range, the next time the fuel is injected, the first time period is maintained, the first fuel injection amount of fuel is injected into the tangential air inlet 2, and the second fuel injection amount of fuel is injected into the spiral air inlet 3.

[0140] If the cylinder pressure is not within the first cylinder pressure range, the next time the fuel is injected, the first time period and the second time period remain unchanged, the first fuel injection ratio and the second fuel injection ratio are adjusted or the first fuel injection total amount is adjusted based on the unchanged first fuel injection total amount. To avoid the hidden dangers caused by the cylinder pressure not being within the first cylinder pressure range when the engine is in the first operating condition.

[0141] If the cylinder pressure is greater than the maximum value of the first cylinder pressure range, the next time the fuel is injected, the first time period and the second time period remain unchanged, and it is determined whether (the first fuel injection ratio determined this time-A%) is within the first preset ratio range and whether (the second fuel injection ratio determined this time+B%) is within the second preset ratio range. Wherein, A is a positive number greater than zero, and B is a positive number greater than zero.

[0142] If (the first fuel injection ratio determined this time-A%) is within the first preset ratio range and (the second fuel injection ratio determined this time+B%) is within the second preset ratio range, the first fuel injection ratio of the next time the fuel is injected into the tangential air inlet 2 is adjusted to be equal to the first fuel injection ratio determined this time minus A, and the second fuel injection ratio of the next time the fuel is injected into the spiral air inlet 3 is adjusted to be equal to the second fuel injection ratio determined this time plus B. By setting in this way, the gap between the early injection and more injection of the tangential air inlet 2 and the late injection and less injection of the spiral air inlet 3 is reduced, that is, the gap between the asynchronous injection fuel injection amounts is reduced, so as to alleviate the phenomenon that the cylinder pressure is greater than the maximum value of the first cylinder pressure range, and improve the operation safety and reliability of the engine.

[0143] If the first fuel injection ratio determined this time (A%) is not within the first preset ratio range, and / or, the second fuel injection ratio determined this time (B%) is not within the second preset ratio range, it is determined whether the first fuel injection total amount determined this time (C) is less than the first minimum limit fuel injection total amount.

[0144] If the first fuel injection total amount determined this time (C) is greater than or equal to the first minimum limit fuel injection total amount, the first fuel injection total amount next time is adjusted to be the first fuel injection total amount determined this time minus C.

[0145] If the first fuel injection total amount determined this time (C) is less than the first minimum limit fuel injection total amount, the first fuel injection total amount next time is adjusted to be the first minimum limit fuel injection total amount.

[0146] It can be understood that when the first fuel injection ratio determined this time (A%) is not within the first preset ratio range, and / or, the second fuel injection ratio determined this time (B%) is not within the second preset ratio range, the phenomenon of the cylinder pressure being greater than the maximum value of the first cylinder pressure range is alleviated by reducing the first fuel injection total amount next time, and the running safety and reliability of the engine are improved, so that when the engine is in the first running condition, the power safety and reliability of the engine can be effectively improved on the basis of ensuring the power performance of the engine.

[0147] Specifically, the first preset ratio range and the second preset ratio range are both experience ranges obtained from a large number of previous tests. The first minimum limit fuel injection total amount is an experience value obtained from a large number of previous tests.

[0148] Exemplarily, in the embodiment, the first preset ratio range is 50% to 65%, and the second preset ratio range is 35% to 50%. Further, in the embodiment, the values of A and B are both 5. It can be understood that the value of A can be increased or decreased and the value of B can be increased or decreased adaptively according to actual working condition requirements.

[0149] If the cylinder pressure is less than the minimum value of the first cylinder pressure range, the first time period and the second time period are kept unchanged next time when fuel is injected, it is determined whether the first fuel injection ratio determined this time (M%) is within the first preset ratio range, and it is determined whether the second fuel injection ratio determined this time (E%) is within the second preset ratio range. Wherein, M is a positive number greater than zero, and E is a positive number greater than zero.

[0150] If (the first fuel injection ratio determined this time + M%) is within the first preset ratio range, and (the second fuel injection ratio determined this time - E%) is within the second preset ratio range, then the first fuel injection ratio for the next time of fuel injection into the tangential air inlet 2 is adjusted to = the first fuel injection ratio determined this time + M%, and the second fuel injection ratio for the next time of fuel injection into the spiral air inlet 3 is adjusted to = the second fuel injection ratio determined this time - E%. In this way, the difference between the fuel injection amount of the tangential air inlet 2 and the fuel injection amount of the spiral air inlet 3 is increased, that is, the difference between the asynchronous fuel injection amounts is increased, so that more mixed gas can be collected in the combustion chamber of the engine in a short time, and the mixing effect of the mixed gas is better, thereby further promoting the in-cylinder combustion and increasing the cylinder pressure.

[0151] If (the first fuel injection ratio determined this time + M%) is not within the first preset ratio range, and / or, (the second fuel injection ratio determined this time - E%) is not within the second preset ratio range, then it is determined whether (the first fuel injection total amount determined this time + F) is greater than the first maximum limit fuel injection total amount. Wherein, F is the second adjustment step of the first fuel injection total amount.

[0152] If (the first fuel injection total amount determined this time + F) is greater than or equal to the first maximum limit fuel injection total amount, then the first fuel injection total amount for the next time is adjusted to = the first maximum limit fuel injection total amount.

[0153] If (the first fuel injection total amount determined this time + F) is less than the first maximum limit fuel injection total amount, then the first fuel injection total amount for the next time is adjusted to = the first fuel injection total amount determined this time + F.

[0154] It can be understood that when (the first fuel injection ratio determined this time + M%) is not within the first preset ratio range, and / or, (the second fuel injection ratio determined this time - E%) is not within the second preset ratio range, the combustion effect is improved by increasing the first fuel injection total amount for the next time, so as to further promote the in-cylinder combustion and increase the cylinder pressure.

[0155] Specifically, the first maximum limit fuel injection total amount is an empirical value obtained from a large number of experiments in the prior art.

[0156] In the embodiment, the values of M and E are both set to 5. It can be understood that the value of M and the value of E can also be increased or decreased adaptively according to the actual working condition requirements.

[0157] In the embodiment, the first adjustment step of the first fuel injection total amount is equal to the second adjustment step of the first fuel injection total amount. In other embodiments, the first adjustment step of the first fuel injection total amount and the second adjustment step of the first fuel injection total amount can also be unequal.

[0158] Specifically, the specific step of determining the total amount of the second fuel injection into the tangential intake port 2 according to the intake flow rate of the intake manifold in step S400 is as follows:

[0159] The total amount of the second fuel injection is obtained according to the current intake flow rate by referring to a seventh table formed of the intake flow rate and the total amount of the second fuel injection. The seventh table is an empirical table obtained from a large number of experiments in the past. As an alternative, the total amount of the second fuel injection is obtained according to the current intake flow rate by referring to a seventh map formed of the intake flow rate and the total amount of the second fuel injection. The seventh map is an empirical map obtained from a large number of experiments in the past.

[0160] Specifically, the specific step of determining the third time period of the fuel injection into the tangential intake port 2 according to the engine speed and the engine torque in step S400 is as follows:

[0161] The fifth crank angle at which the fuel injection into the tangential intake port 2 is started and the third crank angle variation amount of the duration of the fuel injection into the tangential intake port 2 are determined according to the current engine speed and the current engine torque. The third time period is determined according to the fifth crank angle and the third crank angle variation amount.

[0162] It is understood that the crank angle at the start of the third time period is the fifth crank angle.

[0163] Specifically, the fifth crank angle is obtained according to the current engine speed and the current engine torque by referring to an eighth table formed of the engine speed, the engine torque, and the fifth crank angle. The eighth table is an empirical table obtained from a large number of experiments in the past. As an alternative, the fifth crank angle is obtained according to the current engine speed and the current engine torque by referring to an eighth map formed of the engine speed, the engine torque, and the fifth crank angle. The eighth map is an empirical map obtained from a large number of experiments in the past.

[0164] Specifically, the third crank angle variation amount is obtained according to the current engine speed and the current engine torque by referring to a ninth table formed of the engine speed, the engine torque, and the third crank angle variation amount. The ninth table is an empirical table obtained from a large number of experiments in the past. As an alternative, the third crank angle variation amount is obtained according to the current engine speed and the current engine torque by referring to a ninth map formed of the engine speed, the engine torque, and the third crank angle variation amount. The ninth map is an empirical map obtained from a large number of experiments in the past.

[0165] In other embodiments, the fifth crank angle corresponding to the start of fuel injection into the tangential intake passage 2 and the sixth crank angle corresponding to the end of fuel injection into the tangential intake passage 2 can also be obtained by looking up a table or a Map; and the third time period is determined according to the fifth crank angle and the sixth crank angle.

[0166] Alternatively, the above tables can be combined into one table. The above Maps can be combined into one Map.

[0167] In this way, when the engine is in the second operating condition, the phenomenon of fuel colliding with the wall of the tangential intake passage 2 and then adhering to the wall can be effectively alleviated while ensuring the charge efficiency.

[0168] Specifically, when the engine is in the second operating condition, if the cylinder pressure of the engine is greater than the maximum value of the second cylinder pressure range, although the in-cylinder combustion effect of the engine is better at this time, it will cause an increase in fuel consumption and / or mechanical damage and other hidden dangers, and if the cylinder pressure of the engine is less than the minimum value of the second cylinder pressure range, it will also cause insufficient in-cylinder combustion of the engine, a decrease in engine power performance, and other hidden dangers. The second cylinder pressure range is an empirical value obtained from a large number of previous tests. Therefore, in order to avoid the above-mentioned hidden dangers, the engine control method preferably further comprises:

[0169] When the engine is in the second operating condition, the cylinder pressure of the engine is obtained in real time.

[0170] It is determined whether the cylinder pressure is within the second cylinder pressure range.

[0171] If the cylinder pressure is within the second cylinder pressure range, the second time period is kept unchanged and the second fuel injection amount is adjusted next time.

[0172] If the cylinder pressure is not within the second cylinder pressure range, the second fuel injection amount is adjusted next time while keeping the third time period unchanged.

[0173] If the cylinder pressure is greater than the maximum value of the second cylinder pressure range, it is determined whether (the second fuel injection amount determined this time - G) is less than the second minimum limit fuel injection amount next time, where G is the first adjustment step of the second fuel injection amount.

[0174] If (the second fuel injection amount determined this time - G) is greater than or equal to the second minimum limit fuel injection amount, the second fuel injection amount next time is adjusted to be the second fuel injection amount determined this time - G.

[0175] If (the second fuel injection amount determined this time - G) is less than the second minimum limit fuel injection amount, the second fuel injection amount next time is adjusted to be the second minimum limit fuel injection amount.

[0176] The second minimum limit for total fuel injection is an empirical value obtained from numerous previous tests.

[0177] It is understandable that when the cylinder pressure is greater than the maximum value of the second cylinder pressure range, the phenomenon of the cylinder pressure being greater than the maximum value of the second cylinder pressure range is alleviated by reducing the total amount of the second fuel injection in the next cycle. This can also avoid increased fuel consumption and extend the service life of the engine.

[0178] If the cylinder pressure is less than the minimum value of the second cylinder pressure range, then during the next injection, the third time period remains unchanged, and it is determined whether (the determined second total fuel injection + H) is greater than the second maximum limit total fuel injection. Here, H is the second adjustment step size of the second total fuel injection.

[0179] If (the total amount of the second fuel injection determined this time + H) is greater than or equal to the total amount of the second maximum limit fuel injection, then the total amount of the second fuel injection next time will be adjusted to the total amount of the second maximum limit fuel injection.

[0180] If (the total amount of the second fuel injection determined this time + H) is less than the total amount of the second maximum limit fuel injection, then the total amount of the second fuel injection next time will be adjusted to the total amount of the second fuel injection determined this time + H.

[0181] The second maximum limit of fuel injection is an empirical value obtained from a large number of previous tests.

[0182] It is understandable that when the cylinder pressure is less than the minimum value of the second cylinder pressure range, the combustion effect is improved by increasing the total amount of the second fuel injection in the next cycle, so as to further promote in-cylinder combustion and increase cylinder pressure.

[0183] In this embodiment, the first adjustment step size of the second fuel injection quantity is set to be equal to the second adjustment step size of the second fuel injection quantity. In other embodiments, the first adjustment step size of the second fuel injection quantity and the second adjustment step size of the second fuel injection quantity may not be equal.

[0184] like Figure 8 As shown, with the engine piston employing the above-mentioned engine control method, the tumble effect remains consistently good as the engine crankshaft angle changes from 600°CA to 700°CA; Figure 9 As shown, when the crankshaft angle of the engine is 700°CA, the turbulent kinetic energy range is wider, which can effectively improve the flame propagation speed.

[0185] like Figure 10 As shown, by employing the engine control method described above, the flame propagation speed is significantly increased as the engine crankshaft angle changes from 710°CA to 740°CA. The red area in the figure represents the region of the flame within the combustion chamber.

[0186] As shown in Figure 11 , by using the engine piston of the above engine control method, the crank angle of the engine is 700°CA, and the turbulent kinetic energy is increased by 16.6%. As shown in Figure 12 , by using the engine piston of the above engine control method, the crank angle of the engine is 700°CA, and the non-uniformity coefficient is reduced by 36%, and the non-uniformity coefficient is a coefficient representing the uniformity of the mixture. As shown in Figure 13 , by using the engine piston of the above engine control method, the heat release rate is significantly improved. The heat release rate refers to the heat released by the fuel in the combustion chamber per unit time. Figures 11 to 13 The optimized curves in the above figures correspond to the control of the methanol engine by the engine control method of the present embodiment.

[0187] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. An engine piston, characterized in that, Includes a piston body (1), the piston body (1) having a top surface (11) perpendicular to its own axis and a combustion chamber recess (12) recessed in the top surface (11); The combustion chamber recess (12) includes a lower combustion recess (121) and an upper combustion recess (122) sequentially distributed along the axial direction of the piston body (1). The lower combustion recess (121) includes a first sub-combustion recess (1211) and a second sub-combustion recess (1212). The second sub-combustion recess (1212) is disposed between the first sub-combustion recess (1211) and the upper combustion recess (122) and connects the first sub-combustion recess (1211) and the upper combustion recess (122). The upper combustion recess (122) is used to guide fluid through the second sub-combustion recess (1212) into the first sub-combustion recess (1211). The lower combustion pit (121) is symmetrical about the plane of symmetry. The first sub-combustion pit (1211) is semi-ellipsoidal. The contour line of the pit wall of the first sub-combustion pit (1211) on the plane of symmetry is the first contour line. The first contour line is semi-elliptical. The central axis of the piston body (1) is perpendicular to the line containing the major axis of the first contour line and both are located on the plane of symmetry. The contour line of the pit wall of the second sub-combustion pit (1212) on the plane of symmetry is the second contour line. The second contour line is connected to the first end of the first contour line and is located on one side of the line containing the minor axis of the first contour line along the orientation. The second contour line and the first contour line are both curves of the same ellipse. The orientation is parallel to the line containing the major axis of the first contour line. The boundary line between the second sub-combustion pit (1212) and the first sub-combustion pit (1211) is the first boundary line, and all points on the first boundary line are located in the same plane; the boundary line between the second sub-combustion pit (1212) and the upper combustion pit (122) is the second boundary line, and all points on the second boundary line are located in the same plane; the first boundary line and the second boundary line intersect at the second end of the first contour line; The contour lines of the upper combustion pit (122) on the plane of symmetry include a third contour line connected to the second end of the first contour line and a fourth contour line connected to the second contour line; the angle between the third contour line and the top surface (11) is α, and the value of α ranges from 10° to 50°; the angle between the fourth contour line and the top surface (11) is β, and the value of β ranges from 0° to 30°. The intersection of the third contour line and the top surface (11) is the first intersection point, and the intersection of the fourth contour line and the top surface (11) is the second intersection point. The minimum distance between the first intersection point and the outer peripheral wall of the piston body (1) is L4, and the minimum distance between the second intersection point and the outer peripheral wall of the piston body (1) is L5, where L4 < L5.

2. The engine piston according to claim 1, characterized in that, The upper combustion pit (122) is obliquely truncated cone-shaped. The small end of the upper combustion pit (122) is connected to the second sub-combustion pit (1212), and the central axis of the upper combustion pit (122) is perpendicular to the plane where the second boundary line is located.

3. The engine piston according to claim 1, characterized in that, The distance between the first intersection point of the third contour line and the top surface (11) and the second intersection point of the fourth contour line and the top surface (11) is L1; the length of the projection of the third contour line along the axial direction of the piston body (1) onto the plane where the top surface (11) is located is L2, and the length of the projection of the fourth contour line along the axial direction of the piston body (1) onto the plane where the top surface (11) is located is L3; L2 = (0.1~0.2)L1, L3 = (0.1~0.2)L1.

4. The engine piston according to claim 1, characterized in that, The diameter of the piston body (1) is D1; ​​the distance between the first intersection of the third contour line and the top surface (11) and the second intersection of the fourth contour line and the top surface (11) is L1; L1 = (0.7~0.9)D1.

5. The engine piston according to any one of claims 1-4, characterized in that, The piston body (1) has a diameter of D1, the major axis of the first sub-combustion pit (1211) has a length of D2, and the minor axis of the first sub-combustion pit (1211) has a length of D3, where D2 = (0.55~0.75)D1 and D3 = (0.4~0.55)D1.

6. An engine, the engine comprising a cylinder, the cylinder comprising a cylinder block and a cylinder head connected to each other, characterized in that, The engine further includes the engine piston according to any one of claims 1-5, wherein the piston body (1) is slidably disposed in the cavity formed by the cylinder block and the cylinder head along its own axial direction, and the combustion chamber recess (12) forms a combustion chamber between the cylinder head and the combustion chamber recess (12).

7. The engine according to claim 6, characterized in that, The cylinder head is provided with a tangential intake passage (2) and a spiral intake passage (3) that are independent of each other. One end of the tangential intake passage (2) and one end of the spiral intake passage (3) are connected to the intake manifold of the engine. The other end of the tangential intake passage (2) and the other end of the spiral intake passage (3) are connected to the combustion chamber.

8. An engine control method, characterized in that, For use in the engine of claim 7, the engine control method includes: When the engine is running, the engine's operating conditions are judged in real time; the engine's operating conditions include a first operating condition and a second operating condition, wherein the engine load is greater in the first operating condition than in the second operating condition. When the engine is in the first operating condition, the fuel injection parameters are determined based on the intake flow rate of the intake manifold, the engine speed and the engine torque. The fuel injection parameters include the first amount of fuel injected into the tangential intake (2), the second amount of fuel injected into the spiral intake (3), the first time period of fuel injection into the tangential intake (2), and the second time period of fuel injection into the spiral intake (3). During the first time period, the first amount of fuel is injected into the tangential intake (2), and during the second time period, the second amount of fuel is injected into the spiral intake (3); the first amount of fuel is greater than the second amount of fuel.

9. The engine control method according to claim 8, characterized in that, The specific steps for determining the first and second injection quantities based on the intake manifold flow rate, engine speed, and engine torque include: The total amount of the first fuel injection is determined based on the current intake airflow. The first fuel injection percentage of the first fuel injection quantity to the first total fuel injection quantity and the second fuel injection percentage of the second fuel injection quantity to the first total fuel injection quantity are determined based on the current engine speed and the current engine torque. The first fuel injection quantity and the second fuel injection quantity are calculated based on the first total fuel injection quantity, the first fuel injection ratio, and the second fuel injection ratio; Wherein, the first fuel injection ratio is greater than 60% and less than 75%, and the second fuel injection ratio is greater than 25% and less than 40%.

10. The engine control method according to claim 8, characterized in that, The start time of the first time period is earlier than the start time of the second time period.

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