Piston and combustion system

Abstract

The present application relates to the diesel internal combustion engine technical field, specifically to the piston and combustion system. The piston comprises a piston body, the top surface of the piston body is formed with a combustion bowl structure, the combustion bowl structure comprises a combustion surface and a throat, the combustion surface is provided with a groove opened along the radial direction of the piston body, and the groove penetrates the throat, the groove has the maximum depth at the middle part along the circumferential direction of the piston body, and the depth of the groove gradually decreases from the middle part to both sides along the circumferential direction. The groove bottom has the maximum depth at the circumferential middle part, and the depth monotonically decreases to both sides, forming an arc ridge geometry, so that the normal momentum of the spray beam is decomposed into radial outward expansion and circumferential bidirectional components after the spray beam hits the arc surface, the radial distribution uniformity is significantly improved, the equivalence ratio of the upper space and the bowl bottom area is balanced, the central fuel-rich core and the wall oil are weakened, the circumferential concentration field is more balanced, so that the combustion duration is shortened, the smoke peak is inhibited, and the cycle stability and thermal efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of diesel internal combustion engine technology, specifically to pistons and combustion systems. Background Technology

[0002] Compression-ignition diesel internal combustion engines commonly employ re-entry combustion bowls and multi-hole injectors to improve air utilization and suppress smoke. Traditional designs rely on radial diffusion of the spray and the overall swirling or tumble flow formed by the intake air to facilitate mixing. Within the bowl, there are also solutions using geometric features such as annular grooves, ribs, or steps to guide the flow. However, existing solutions often suffer from insufficient matching between the spray and bowl shape features, and inadequate circumferential diffusion. Specifically, the coverage and flow distribution of the upper and lower spray layers (or different radius zones) are not coupled and matched with the internal geometry of the bowl, resulting in uneven spatial mixing distribution. This easily leads to centrally rich or locally lean zones, resulting in excessively long combustion duration and high smoke levels. Summary of the Invention

[0003] The objective of this invention is to at least solve the problem of uneven fuel distribution within the piston. This objective is achieved through the following technical solution: A first aspect of the present invention provides a piston, including a piston body, wherein a combustion bowl structure is formed on the top surface of the piston body, the combustion bowl structure including a combustion surface and a throat, the combustion surface having a groove formed along the radial direction of the piston body, the groove penetrating the throat, the groove having a maximum depth at the center along the circumferential direction of the piston body, and the depth of the groove gradually decreasing from the center to the sides along the circumferential direction.

[0004] According to the piston of the present invention, the groove bottom has the maximum depth at the circumferential center and decreases monotonically towards both sides, forming an arc ridge geometry. This causes the normal momentum of the jet to be decomposed into radial outward and circumferential bidirectional components after impacting the arc surface. The fluid is symmetrically diverted along both sides with the depth gradient and continuously entrained, thereby establishing a multi-stage, multi-directional entrainment and diffusion channel with radial and circumferential coupling between the throat, the bottom of the bowl, and the upper space. Through the above synergistic effect, the traditional process of passive diversion at a single point in the throat can be transformed into a two-stage controlled diversion and diffusion along the radial direction to the throat position. This significantly improves the radial distribution uniformity and balances the equivalence ratio between the upper space and the bottom of the bowl region. At the same time, it weakens the central fuel-rich core and the oil adhering to the wall, making the circumferential concentration field more balanced. This shortens the combustion duration, suppresses the smoke peak, and is conducive to improving cycle stability and thermal efficiency.

[0005] In addition, the piston according to the present invention may also have the following additional technical features: In some embodiments of the present invention, the combustion bowl structure is coaxially arranged with the piston body, and along the radial direction, the outermost edge of the piston bowl structure is the outer edge, and the radius of the piston body is R; The distance from the central axis of the piston body to the outer edge is D1, and the value of D1 ranges from 0.86R to 0.96R. The distance from the central axis to the throat is D2, and the value of D2 ranges from 0.45R to 0.55R. The maximum depth of the combustion bowl structure is H, and the value of H ranges from 0.21R to 0.29R.

[0006] In some embodiments of the present invention, along the direction from the central axis to the throat, the combustion surface is sequentially formed with a central boss, a first arc structure and a second arc structure, wherein the first arc structure and the second arc structure are both arc surfaces recessed into the combustion surface; The radius of the central boss is d1, and the value of d1 ranges from 0.22R to 0.28R. The radius of the first circular arc structure is d2, and the value of d2 ranges from 0.10R to 0.16R. The radius of the second circular arc structure is d3, and the value of d3 ranges from 0.04R to 0.11R.

[0007] In some embodiments of the present invention, the throat has a rounded corner structure, the radius of the throat is d4, and the value of d4 ranges from 2 to 4.5 mm.

[0008] In some embodiments of the present invention, the combustion bowl structure further includes an inner edge, which is disposed between the throat and the outer edge. The combustion surface between the inner edge and the throat is recessed inward to form a third arc structure. The radius of the third arc structure is d5, and the value of d5 ranges from 0.13R to 0.19R. The inner edge is a rounded corner structure, and the radius of the inner edge is d6, and the value of d6 ranges from 1 to 2.5 mm.

[0009] In some embodiments of the present invention, the combustion surface between the inner edge and the outer edge is recessed inward and sequentially forms a fourth arc structure and a transition arc. The radius of the fourth arc structure is d7, and the value of d7 ranges from 0.15R to 0.29R. The radius of the transition arc is d8, and the value of d8 ranges from 0.20R to 0.35R.

[0010] A first aspect of the present invention provides a combustion system comprising: Cylinder liner and cylinder head; The piston described above is disposed inside the cylinder liner, and the combustion surface of the piston body and the cylinder head together form a combustion chamber; The injector has a first nozzle and a second nozzle spaced apart along the axial direction of the piston, the first nozzle being located above the second nozzle, and the amount of fuel injected by the first nozzle being 30% to 40% of the total amount of fuel injected.

[0011] In some embodiments of the present invention, the spray cone angle of the first nozzle is greater than that of the second nozzle, and the difference between the spray cone angle of the first nozzle and the spray cone angle of the second nozzle is in the range of 4° to 12°.

[0012] In some embodiments of the present invention, the area where the first nozzle sprays oil toward the combustion surface is a first region, the area where the second nozzle sprays oil toward the combustion surface is a second region, the portion of the groove located in the first region is a first groove, the portion of the groove located in the second region is a second groove, the volume of the first groove is V1, the volume of the second groove is V2, and the volume ratio between the first groove and the second groove is [value missing]. Wherein, r1 is the diameter of the first nozzle and r2 is the diameter of the second nozzle.

[0013] In some embodiments of the present invention, the first groove has a first width w1 and a first depth h1, wherein the value of the first width w1 ranges from [value missing]. The range of values ​​for the first depth h1 is: ; The second groove has a second width w2 and a second depth h2, wherein the value of the second width w2 is within the range of... The range of values ​​for the second depth h2 is: ; Wherein, R is the radius of the piston body, and trajpar is the trajectory parameter. Attached Figure Description

[0014] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of a partial structure of the top of a piston body according to an embodiment of the present invention is shown. Figure 2 A first-view view of a piston body according to an embodiment of the present invention is shown schematically; Figure 3 A partial structural diagram of the piston cup structure according to an embodiment of the present invention is shown schematically; Figure 4A partial perspective view of the piston bowl structure according to an embodiment of the present invention is shown schematically; Figure 5 A partial cross-sectional view of a piston body according to an embodiment of the present invention is shown schematically; Figure 6 This is a cross-sectional view of the groove along the direction perpendicular to the radial direction; Figure 7 A schematic diagram of the spray cone angle of the fuel injector; Figure 8 A schematic diagram of the spray cone angle corresponding to the first nozzle and the first region; Figure 9 This is a schematic diagram of the spray cone angle corresponding to the second nozzle and the second region.

[0015] The attached figures are labeled as follows: 100. Piston body; 101. Top surface; 10. Combustion surface; 11. Groove; 12. Central boss; 20. Throat; 30. Inner edge; 40. Outer edge; 200. Injector; 201. First nozzle; 2011. First region; 202. Second nozzle; 2021. Second region. Detailed Implementation

[0016] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0017] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0018] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0019] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure is flipped, an element described as "below other elements or features" or "below other elements or features" would subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations.

[0020] like Figures 1 to 6 As shown, according to an embodiment of the present invention, a piston suitable for compression-ignition diesel internal combustion engines is provided. The piston includes a piston body 100, the top surface 101 of which is recessed inward to form a combustion bowl structure. The combustion bowl structure includes a combustion surface 10 and a throat 20. The combustion surface 10 is composed of a bowl bottom and sidewalls, and transitions continuously with the throat 20 via a smooth curved surface. A groove 11 is provided on the combustion surface 10, extending radially along the piston body 100. The groove 11 extends outward from the inner region of the combustion bowl and penetrates the throat 20, forming an opening section at the throat 20, thus communicating with the upper and lower spaces of the groove 11 and the throat 20. Preferably, the radial starting end of the groove 11 is located near the bowl bottom, and the radial ending end is located outside the re-entry section outside the throat 20, transitioning continuously with the surrounding bowl surface via a smooth curved surface to avoid sharp corners or steps.

[0021] Specifically, the groove 11 has an arc-shaped concave structure, that is, the bottom of the groove 11 has the maximum depth at the center of the circumference, and the depth of the groove 11 gradually decreases from the center along the circumference to both sides until it connects with the bowl surface. Preferably, the connection between the bottom of the groove and the bowl surface on both sides adopts an arc or spline transition to ensure at least tangential continuity.

[0022] Preferably, multiple grooves 11 are uniformly arranged circumferentially on the combustion surface 10. The radial direction of each groove 11 is consistent with the corresponding main spray direction. The angular width of the opening section of the groove 11 at the throat 20 is the same or substantially the same along the circumferential direction, thereby achieving consistent flow guidance and diversion in multiple circumferential sectors. For ease of dimension definition, the bowl depth can be defined as the axial distance from the piston crown reference plane to the lowest point of the bowl bottom. The depth of the groove 11 is measured with the theoretical bowl surface without grooves as the zero reference.

[0023] In manufacturing, the transition radius between the groove 11 and the combustion surface 10 is determined to be reasonable based on the material and process. It can be formed by casting and then CNC machining for fine finishing or directly CNC machining. The outer edge 40 of the opening section of the throat 20 maintains sufficient structural thickness to balance strength and heat dissipation requirements.

[0024] In this embodiment, during piston operation, the mixture formed by the spray and intake air is guided radially by the groove 11 and undergoes controlled splitting at the throat 20 through the open section. Simultaneously, due to the arc-ridge geometry of the groove 11, which is deepest in the circumferential center and gradually shallows towards both sides, the normal momentum after the spray impact is decomposed into radial outward and circumferential bidirectional components. The mixture naturally splits along both sides and is entrained and rises back in the bowl bottom region. Through the guiding flow through the throat 20 and the circumferential splitting effect of the arc-ridge groove bottom, the passive single-point splitting that originally occurred only at the throat 20 can be transformed into a two-stage controlled splitting along the radial direction to the throat 20, improving the uniformity of fuel and mixture distribution in both the radial and circumferential directions, reducing localized rich combustion zones, and suppressing oil adhesion to the walls, thereby shortening the combustion duration and reducing peak smoke opacity.

[0025] In some embodiments, a combustion bowl structure is formed on the top surface 101 of the piston body 100, and the combustion bowl structure is coaxially arranged with the piston body 100. To standardize the measurement caliber, R is defined as the radius of the piston body 100 (the radial distance from the piston's central axis to the outer circular surface within the crown reference plane). The outermost edge (outer edge 40) is the boundary between the combustion bowl structure and the unopened area of ​​the crown (the intersection of the outer curved surface of the re-entry section and the crown reference plane). The throat 20 is the circumferential position of the minimum opening diameter of the combustion bowl. The combustion surface 10 is a continuous curved surface formed by the bowl bottom and sidewalls. The maximum depth H is the absolute value of the axial distance from the crown reference plane to the central apex of the combustion bowl (the minimum point of the combustion surface 10 relative to the reference).

[0026] Under the above definition, the combustion bowl structure satisfies the following geometric relationship (see...). Figure 5 (Illustrative diagram) The radial distance from the central axis of the piston body 100 to the outer edge 40 is D1, and the value of D1 ranges from 0.86R to 0.96R. Specifically, it can be 0.86R, 0.88R, 0.90R, 0.92R, 0.94R, or 0.96R. In a preferred embodiment, D1 = 0.92R.

[0027] The radial distance from the central axis of the piston body 100 to the throat 20 is D2, and the value of D2 ranges from 0.45R to 0.55R. Specifically, it can be 0.45R, 0.50R, or 0.55R, with the preferred embodiment being D2=0.50R.

[0028] The maximum depth H of the combustion bowl structure satisfies the value range of 0.21R to 0.29R. Specifically, it can be 0.21R, 0.23R, 0.25R, 0.27R, or 0.29R, with the preferred embodiment being H=0.25R.

[0029] It should be explained that D1 and D2 are measured radially within the coronal reference plane, and H is the absolute value of the axial distance from the coronal reference plane to the apex of the central bowl. If the central region is an isobath or a small plateau, then the geometric center of this isobath is taken as the apex of the central bowl.

[0030] D1 is within the range of 0.86R to 0.96R, ensuring a moderate re-entry section width, providing sufficient space for recirculation and entrainment while avoiding excessive re-entry that would limit effective volume and spray distribution. D2 is within the range of 0.45R to 0.55R, ensuring that the throat 20 position is neither excessively recessed (avoiding spray congestion and excessively high fuel concentration and insufficient air in certain areas) nor excessively extended (avoiding direct leakage from the throat 20, weakening re-entry recirculation). H is within the range of 0.21R to 0.29R, achieving a balance between the combustion bowl depth and total volume in terms of spray cone angle, intake organization, and compression ratio, taking into account spray distribution, mixing uniformity, and heat release concentration, which is beneficial for reducing smoke, shortening combustion duration, and improving isochoricity and cycle stability. When combined with the groove 11 penetrating the throat 20, the spray and mixture achieve two-stage controlled splitting and entrainment between the inside and outside of the throat 20 and the bottom area of ​​the bowl, further improving radial and circumferential equivalence uniformity and reducing oil residue on the walls and localized rich combustion zones.

[0031] To verify the effectiveness of the aforementioned geometric range, a bench test was conducted on a single-cylinder prototype from the same platform. Fuel, injection strategies, and turbocharging / intercooling were kept consistent, with only the D1, D2, and H of the combustion bowl changed (the rest remained unchanged). Example test conditions: engine speed 2000 r / min, BMEP ≈ 10 bar, injection pressure differential 120 MPa, intake air temperature 40℃, back pressure 1.2 bar. The results are as follows (steady-state average):

[0032] Compared to the comparative example, under the same injection and air-fuel ratio conditions, the embodiment showed a reduction in smoke density (FSN) of approximately 35%–42%, a reduction in particulate matter (PM) of approximately 20%–24%, a shortening of combustion duration (CA10–90) of approximately 5°–6°CA, an improvement in indicated fuel consumption rate (ISFC) of approximately 1.5%–2%, and NOx levels maintained within acceptable limits. These results demonstrate that the aforementioned geometric range can suppress fuel-rich cores and fuel adsorption on the combustion walls while maintaining heat release concentration, significantly improving mixing and combustion uniformity.

[0033] In some embodiments, along the central axis of the piston body 100 toward the throat 20, on the diameter section passing through the central axis, the combustion surface 10 is sequentially formed by splicing together a central boss 12, a first arc structure and a second arc structure. The first arc structure and the second arc structure are formed by the combustion surface being recessed inward. The three are connected by a continuous curved surface transition to at least satisfy tangential continuity, preferably curvature continuity. The central boss 12 has a radius of curvature d1 in the arc segment of the cross section, with a value ranging from 0.22 to 0.28R, specifically 0.22R, 0.24R, 0.26R, or 0.28R. The first arc structure outside the central boss 12 has a radius of curvature d2 in the arc segment of the cross section, with a value ranging from 0.10 to 0.16R, specifically 0.10R, 0.12R, 0.14R, or 0.16R. The second arc structure extending outward has a radius of curvature d3 in the arc segment of the cross section, with a value ranging from 0.04 to 0.11R, specifically 0.04R, 0.06R, 0.08R, or 0.11R, where R is the radius of the piston body 100. Preferably, d1 > d2 > d3, and the normal and curvature of each arc segment are continuous with those of adjacent segments at the splicing point to ensure that the slope of the combustion surface 10 on the cross-section is monotonous, without steps or sharp corners. To standardize the measurement diameter, d1, d2, and d3 are obtained by circular fitting the corresponding arc segments on the diameter cross-section, and the endpoints of each arc segment are determined by the condition that the tangents of adjacent segments are equal. The throat 20 is located at the minimum opening diameter of the re-entry section, and the second arc structure transitions continuously outward with the curved surface of the throat 20. If necessary, a smooth transition section connecting with the circumferential guide groove 11 is provided at the throat 20 to avoid local separation and stress concentration.

[0034] spray along Figure 4As shown, J represents the injection direction of the injector 200, J1 represents fuel that travels approximately upwards after the collision, J2 represents fuel that travels approximately downwards after the collision, J3 represents fuel that travels approximately to one side after the collision, and J4 represents fuel that travels approximately to the other side after the collision. After the fuel injected by the injector 200 enters along the set direction, it first undergoes controlled splitting at the throat 20. Under the combined action of the curved surface of the throat 20 and the opening section of the groove 11 penetrating the throat 20, the air-fuel mixture is divided into multiple paths. First, it is sent upwards and outwards along the normal direction of the throat 20 to the upper space outside the throat 20. Second, guided by the opening section of the groove 11, it diffuses symmetrically in the circumferential direction towards both sides of the groove 11 at the throat 20. Third, some of the air-fuel mixture falls back into the recess after crossing the throat 20, completing buffering and spreading in the bottom area of ​​the bowl, and is then entrained and lifted upwards in subsequent flow. The fuel entering the recess flows sequentially through the second arc structure (section curvature radius d3, adjacent to the throat 20), the first arc structure (section curvature radius d2), and the central boss 12 (section curvature radius d1 is relatively large). The second arc structure, with a smaller curvature radius, guides the re-entry flow to rotate rapidly, smoothly reversing momentum from the throat 20. Subsequently, the first arc structure, with a medium curvature radius, achieves smooth expansion and redistribution from the outside to the inside, evenly delivering the mixture to the medium radius zone and suppressing separation. Finally, the central boss 12, with a larger curvature radius, completes bottom buffering and final homogenization, weakening the central impact and local fuel-rich core, and together with the circumferential diffusion on both sides of the groove 11, promotes entrainment and recovery. Thus, in the closed-loop chain of "throat 20-stage initial diversion, circumferential bidirectional diffusion, concave descent, rotation, expansion, buffering, and entrainment recovery," a quantitative and balanced supply of the mixture in the radial and circumferential directions is achieved, reducing the near-wall liquid film and the central fuel-rich zone, thereby shortening the combustion duration, reducing smoke opacity, and improving cycle stability and indicated thermal efficiency. Simultaneously, the central boss 12, the first arc structure, and the second arc structure adopt a cylinder diameter-based profile curvature radius range setting, facilitating calibration migration and geometric reuse of different cylinder diameter platforms within this range.

[0035] Furthermore, in the combustion bowl structure of the piston described above, the throat 20 is a transition section that forms the minimum opening diameter of the combustion bowl. Preferably, it adopts a rounded corner structure to ensure a continuous transition with the re-entry section of the combustion surface 10. On the diametrical cross-section through the central axis of the piston body 100, the curve of the rounded corner of the throat 20 is fitted with an arc, and its radius is defined as d4, with a value ranging from 2 mm to 4.5 mm. Preferably, to balance controlled flow splitting and structural strength, d4 is taken as 2.5 mm to 3.5 mm, more preferably 3.0 mm. The rounded corner and the curved surfaces on both sides of the throat 20 (including the re-entry section and the outer curved surface of the throat 20) satisfy at least tangential continuity, preferably curvature continuity, to avoid forming steps or sharp edges. To standardize the measurement diameter, d4 is measured according to the radius of the arc at the junction of the minimum opening of the throat 20 and the re-entry section on the diametrical cross-section, and remains substantially consistent in the circumferential direction. When the combustion surface 10 is provided with a flow guide groove 11 that penetrates the throat 20, the fillet is smoothly connected to the boundary surface of the groove 11 with a transition arc at the opening of the groove 11, maintaining continuity and minimum wall thickness requirements. This fillet can be formed by CNC precision finishing after casting or by direct CNC machining. Machining errors do not affect the above-mentioned range and function of the throat 20, and meet the structural strength requirements of the throat 20.

[0036] Furthermore, the combustion bowl is coaxially arranged with the piston body 100. An inner edge 30 is provided along the radial path from the throat 20 outwards to the outermost edge (i.e., outer edge 40) along the central axis of the piston body 100. The inner edge 30 is located between the throat 20 and the outer edge 40. In the diametrical section through the central axis of the piston body 100, the combustion surface 10 between the throat 20 and the inner edge 30 adopts an inwardly concave third arc structure for transition. The radius of curvature of this third arc structure is defined as d5, and its value ranges from 0.13R to 0.19R, specifically 0.13R, 0.15R, 0.17R, and 0.19R. To ensure strength and geometric smoothness, the inner edge 30 has a rounded corner structure, and its rounded corner radius in the diametrical section is defined as d6, with a value range of 1.0mm to 2.5mm. Preferably, the third arc structure is at least tangentially continuous, and more preferably curvature continuously continuous, with respect to the crown reference plane of the throat 20 surface, the inner edge 30 fillet, and the surrounding area of ​​the outer edge 40, to avoid the formation of steps or sharp edges and to reduce flow separation and stress concentration. To standardize the measurement diameter, d5 is obtained by circular fitting the transition section between the throat 20 and the inner edge 30 on the diameter profile, with the fitting endpoints determined by equal tangents or equal curvature conditions with adjacent surfaces. d6 is the actual machining radius of the inner edge 30 fillet in the diameter profile, and remains substantially consistent in the circumferential direction. When the combustion surface 10 is also provided with a flow guide groove 11 penetrating the throat 20, the third arc structure smoothly connects to the boundary surface of the groove 11 at the opening of the groove 11 with a transition arc to maintain continuity and minimum wall thickness requirements. This area can be formed by casting followed by CNC finishing or direct CNC machining. The tool fillet and tolerance settings should ensure that d5 or d6 falls within the above range and meets the minimum metal connection thickness of the throat 20 and the surrounding area of ​​the inner edge 30.

[0037] Furthermore, along the radial path from the inner edge 30 to the outer edge 40 along the central axis of the piston body 100, in the diametrical section passing through the central axis, the combustion surface 10 is concave inward and successively consists of a fourth circular arc structure and a transition circular arc, ultimately intersecting with the crown reference plane at the outer edge 40. The fourth circular arc structure is an arc segment within the section, with its radius of curvature defined as d7, ranging from 0.15R to 0.29R, specifically 0.15R, 0.20R, 0.25R, or 0.29R. The transition circular arc is the converging arc connecting the fourth circular arc structure and the crown reference plane, with its cross-sectional radius of curvature defined as d8, ranging from 0.20R to 0.35R, specifically 0.20R, 0.25R, 0.30R, or 0.35R. Preferably, the outer end of the fourth arc structure and the transition arc meet the condition of equal tangency at the splice. The overall combustion surface 10 and the adjacent third arc structure achieve at least tangential continuity at the inner edge 30, and more preferably curvature continuity, to ensure a monotonous profile slope without steps or sharp corners, while also considering flow adhesion and structural strength. The transition arc smoothly connects to the crown reference plane at the outer edge 40, maintaining the minimum metal connection thickness and machining allowance at the outer edge 40. To standardize the measurement diameter, d7 and d8 are obtained by circular fitting of the corresponding arc segments on the diameter profile, with the fitting endpoints determined by the equal tangency / equal curvature conditions with adjacent segments. The fourth arc structure remains basically consistent in the circumferential direction. When the combustion surface 10 is provided with a flow guide groove 11 penetrating the throat 20, the fourth arc structure and the transition arc smoothly connect in the vicinity of the opening of the groove 11 with a small transition arc or spline surface to avoid forming new sharp corners or weak sections.

[0038] In some embodiments, a groove 11 provided on the combustion surface 10 extends from the central axis of the piston body 100 toward the outer edge 40 and penetrates the throat 20. At any point, a cross-section perpendicular to the radial direction of the piston is taken, and the shape and size of the groove 11 in this cross-section are observed. The cross-sectional width of the groove 11 is measured along the circumferential direction, and the cross-sectional depth is measured along the normal of the ungrooved theoretical combustion surface 10 as a reference. By examining each such cross-section sequentially along the central axis toward the outer edge 40, it can be seen that the cross-section of the groove 11 gradually increases, with at least one of the cross-sectional width and cross-sectional depth continuously increasing with outward movement, preferably both increasing simultaneously. By adopting the groove 11 channel with the cross-section gradually increasing from the inside to the outside, the initial diversion and circumferential diffusion at the throat 20 obtain a more abundant and continuous flow channel. The local impact and shear peak near the throat 20 are weakened, thereby reducing the formation of liquid film and initial smoke core. As for the flow falling back into the pit, when it passes through the curved surface near the throat 20 from the outside to the inside, then to the middle curved surface, and finally to the bottom buffer zone, the geometric relationship of the cross-section from large to small forms a gentle convergence and traction effect, which is conducive to entrainment and revaporization, and promotes a more uniform equivalence ratio in both the radial and circumferential directions.

[0039] like Figures 1 to 9 As shown, this embodiment also provides a combustion system, including a cylinder liner and a cylinder head. A piston is disposed within the cylinder liner and can reciprocate. The top surface 101 of the piston body 100 coaxially forms a combustion bowl structure, and the combustion surface 10 and the cylinder head together form a combustion chamber. Preferably, the combustion bowl structure includes a throat 20, an inner edge 30, and an outer edge 40. The combustion surface 10 is formed by a second arc structure, a first arc structure, and a central boss 12 continuously spliced ​​together on a diametrical cross-section through the piston's central axis. A guide groove 11 penetrating the throat 20 can be provided at the throat 20. The aforementioned curved surfaces transition smoothly with the rounded corners of the throat 20 and the inner edge 30. An injector 200 is installed on the cylinder head. The injector 200 has nozzles along the piston axial direction, including at least a first nozzle 201 and a second nozzle 202. The first nozzle 201 is located axially above the second nozzle 202, and the nozzle axes of both nozzles face inward toward the interior of the combustion bowl. To facilitate circumferential coverage, the first nozzle 201 and the second nozzle 202 can be arranged in their respective nozzle groups at equal intervals in the circumferential direction. The fuel injection volume output by the first nozzle 201 (or the first nozzle 201 group) accounts for 30% to 40% of the total fuel injection volume, and the remaining fuel injection volume is output by the second nozzle 202 (or the second nozzle 202 group). During assembly, the main hit radius of the spray from the first nozzle 201 is arranged to fall within the vicinity of the throat 20 or the corresponding area in the upper space outside the throat 20 (e.g., Figure 8 As shown in Figure a), to promote upward diffusion and circumferential expansion at the throat 20, the main impact radius of the second nozzle 202 is located in the recessed area inside the throat 20 (as shown in Figure a). Figure 9 As shown in Figure b), the falling mixture flows sequentially along the second arc structure near the throat 20, the inward first arc structure, and the central protrusion 12 at the bottom of the bowl, and is entrained and lifted back. When the combustion surface 10 is provided with a guide groove 11 penetrating the throat 20, the first nozzle 201 and the opening section of the groove 11 can be arranged one-to-one or staggered in the circumferential direction to form a controlled multi-directional flow channel at the throat 20. At the same time, the second nozzle 202 cooperates with the groove 11 to complete buffering, spreading and re-entraining in the pit. Through the synergy of the above structure and fuel injection ratio, the throat 20 first achieves flow diversion. Part of the mixed gas enters the upper space from the throat 20 upwards, while another part diffuses left and right along the circumference of the throat 20. The remaining mixed gas falls back into the recess and flows from the outside to the inside through the second arc structure, the first arc structure, and the central boss 12. Finally, it is sucked up and rises in the bowl and merges with the upper flow. The first nozzle 201 is responsible for supplying the upper space and expanding the throat 20 circumferentially, while the second nozzle 202 is responsible for replenishing the recess and the middle radius zone. The fuel injection ratio of the two is within the aforementioned range, which can suppress the local fuel richness and liquid film formation in the recess and near-wall area without sacrificing the upper re-oxidation capacity, thus obtaining a more balanced radial and circumferential mixing distribution.

[0040] In the aforementioned combustion system, the first nozzle 201 is axially positioned above the second nozzle 202. The spray cone angle of the nozzles (defined as a full angle, i.e., twice the angle between the outer envelope of the spray and the spray axis) is set as follows: the spray cone angle of the first nozzle 201 is greater than that of the second nozzle 202, with a difference of 4° to 12°. Specifically, the spray cone angle of the first nozzle 201 is 145° to 155°, and the spray cone angle of the second nozzle 202 is 141° to 147°. To ensure circumferential coverage and avoid mutual obstruction, the first nozzle 201 and the second nozzle 202 can be circumferentially distributed and staggered in their respective rings. The spray radius of the first nozzle 201 preferably falls in the corresponding area of ​​the upper space outside the throat 20, so as to undertake the supply of "upward delivery and circumferential expansion". The spray radius of the second nozzle 202 preferably falls in the pit or medium radius zone inside the throat 20, so as to cooperate with the outer-to-inner curved surface sequence on the combustion surface 10 to complete buffering, spreading and entrainment and recovery. In this embodiment, the upper row of nozzles achieves rapid coverage and circumferential expansion of the upper space outside the throat 20 with a larger cone angle, while the lower row of nozzles directionally supplies fuel to the inner side of the throat 20 and the pit area with a relatively smaller cone angle. The two form a complementary supply in the radial direction, which not only enhances the initial diversion and re-oxidation capacity at the throat 20, but also suppresses the local fuel richness and liquid film in the pit and near the wall. Compared to the comparison scheme with equal cone angle or too small or too large difference, this ratio can significantly reduce smoke opacity and improve cycle stability, while having better calibration robustness to small disturbances in spray cone angle and rail pressure.

[0041] In this embodiment, the cylinder head is equipped with an injector 200. The injector 200 has a first spray hole 201 and a second spray hole 202 arranged along the piston axis. On the combustion surface 10, the combustion surface 10 is divided into two spray landing sectors by the principal projection of the spray axes of the two spray holes and their equidistant dividing lines. The sector covered by the first spray hole 201 spraying fuel towards the combustion surface 10 is defined as the first region 2011, and the sector covered by the second spray hole 202 is defined as the second region 2021. The portion of the groove 11 radially penetrating the throat 20 on the combustion surface 10 within the first region 2011 is called the first groove, and the portion within the second region 2021 is called the second groove. The volumes of the two grooves are measured using the theoretical combustion surface 10 without grooves as the zero reference and according to the three-dimensional solid difference, and are denoted as V1 and V2 respectively. To ensure that the supply and channel volume of the two sectors match the flow capacity of the spray holes, the volume distribution is preferably determined by the following formula:

[0042] Where r1 is the orifice diameter of the first nozzle 201, and r2 is the orifice diameter of the second nozzle 202 (under the same pressure difference and similar flow coefficient, the flow capacity of the two nozzles is approximately proportional to the square of the orifice diameter). Within the manufacturing and assembly tolerances, a volume deviation of ±5% to ±10% is allowed without affecting the function.

[0043] The volume of groove 11 in the two sectors is distributed according to the square ratio of the orifice diameter, so that the "effective channel volume" of the first region 2011 (corresponding to the first nozzle 201) and the second region 2021 (corresponding to the second nozzle 202) matches their respective spray mass flow rates. The first nozzle 201 side obtains a more sufficient outward delivery and circumferential expansion channel, while the second nozzle 202 side obtains a corresponding proportion of fallback, spreading, and entrainment channel. The initial diversion and four-way diffusion at the throat 20 are thus more stable, the radial and circumferential supply of the two sectors is more balanced, and the local fuel-rich nuclei and near-wall liquid film are weakened, resulting in a decrease in smoke opacity, a shortened combustion duration, and improved cycle stability.

[0044] Further, the combustion surface 10 is divided into a first region 2011 and a second region 2021 based on the landing sector of the two nozzles on the combustion surface 10. The portion of the groove 11 located in the first region 2011 is defined as the first groove, and the portion located in the second region 2021 is defined as the second groove. For any groove, its width w (circumferentially) and depth h (measured along the normal vector of the ungrooved theoretical combustion surface 10 as the zero reference) are measured on a cross-section perpendicular to the radial direction of the piston body 100. Let R be the radius of the piston body 100, and let trajpar∈[0,1] be the normalized trajectory parameter along the radial path (from inside to outside) of the groove 11, where trajpar=0 is taken at the inner end of the groove, and trajpar=1 is taken at the outer end of the groove. Preferably, the dimensions are set according to the following intervals: First tank:

[0045] Second tank:

[0046] The above expression indicates that at a given trajpar position, each dimension is taken from the corresponding coefficient range. As trajpar increases from 0 to 1, w1, h1, w2, and h2 monotonically increase, causing the cross-section of the tank to gradually enlarge from the inside out. Preferably, the outline of the tank is continuous with the surrounding combustion surface 10 at least tangentially in each cross-section, and the circumferential shape maintains an arc ridge shape with the deepest part in the middle of the tank bottom and gradually becoming shallower towards both sides.

[0047] The present invention also includes an engine comprising the aforementioned combustion system. The engine includes a cylinder block, cylinder liners, and a cylinder head. A piston reciprocates within the cylinder liner. The combustion bowl structure on the piston top surface 101, together with the cylinder head, forms a combustion chamber. An injector 200 is provided on the cylinder head, having a first nozzle 201 and a second nozzle 202 spaced apart along the piston axial direction. The spray cone angle, fuel injection ratio, impact radius, and geometric matching relationship with the combustion surface 10 are all configured according to the aforementioned embodiment of the combustion system. The engine also includes an intake system and an exhaust system. The intake system may include one or more of an intake manifold, a turbocharger, and an intercooler. The exhaust system may include one or more of an exhaust manifold and an aftertreatment device (such as an oxidation catalyst, a particulate filter, a selective catalytic reduction device, etc.). The fuel supply system may include a low-pressure fuel circuit, a high-pressure pump, and a common rail. The control device is an engine control unit, used to control the injection timing, injection quantity, rail pressure, and the distribution strategy of the first nozzle 201 and the second nozzle 202 based on operating parameters such as engine speed, load, and temperature. Preferably, the engine is a compression-ignition diesel internal combustion engine. In a multi-cylinder arrangement, each cylinder is equipped with a piston and injector 200 of the combustion system. During assembly, the jet of the first nozzle 201 covers the throat 20 and its upper outer space, and the jet of the second nozzle 202 covers the recess and mid-radius zone inside the throat 20. The grooves 11 on the combustion surface 10 correspond one-to-one with the opening section of the throat 20 in each cylinder or are arranged in a predetermined phase offset. During operation, controlled flow is first achieved at the throat 20. Part of the mixture is sent upward and outward and spread circumferentially, while part of the mixture falls back into the recess and flows sequentially along the second arc structure, the first arc structure, and the central boss 12, and is entrained and lifted back, thereby achieving a balanced mixture distribution in both radial and circumferential dimensions. Compared with conventional structures, this exhibits the effects of reducing particulate matter and smoke, shortening the combustion duration, and improving cycle stability.

[0048] The present invention also includes a vehicle comprising the aforementioned engine. The vehicle includes a frame and a body, with the engine mounted in an engine compartment and connected to a transmission system. Preferably, the vehicle is any of a passenger car, commercial vehicle, or construction machinery. In heavy-duty or high-load vehicles, turbocharging and efficient aftertreatment configurations can be optionally added to fully leverage the advantages of the combustion system in reducing particulate emissions and improving fuel economy. During vehicle operation, the aforementioned combustion system within the engine maintains a stable mixing and combustion process at different altitudes and ambient temperatures, thereby achieving lower smoke levels, shorter combustion duration, and better cycle consistency and overall vehicle economy without sacrificing nitrogen oxide control.

[0049] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A piston, characterized in that, The piston body (100) includes a piston body (100), and a combustion bowl structure is formed on the top surface (101) of the piston body (100). The combustion bowl structure includes a combustion surface (10) and a throat (20). The combustion surface (10) is provided with a groove (11) opened in the radial direction of the piston body (100), and the groove (11) penetrates the throat (20). The groove (11) has the maximum depth in the middle part along the circumferential direction of the piston body (100), and the depth of the groove (11) gradually decreases from the middle part to both sides along the circumferential direction.

2. The piston according to claim 1, characterized in that, The combustion bowl structure is coaxially arranged with the piston body (100). Along the radial direction, the outermost edge of the piston bowl structure is the outer edge (40), and the radius of the piston body (100) is R. The distance from the central axis of the piston body (100) to the outer edge (40) is D1, and the value of D1 ranges from 0.86R to 0.96R. The distance from the central axis to the throat (20) is D2, and the value of D2 ranges from 0.45R to 0.55R; The maximum depth of the combustion bowl structure is H, and the value of H ranges from 0.21R to 0.29R.

3. The piston according to claim 2, characterized in that, Along the central axis to the throat (20), the combustion surface (10) sequentially forms a central boss (12), a first arc structure and a second arc structure. Both the first arc structure and the second arc structure are arc surfaces recessed into the combustion surface (10). The radius of the central boss (12) is d1, and the value of d1 ranges from 0.22R to 0.28R. The radius of the first circular arc structure is d2, and the value of d2 ranges from 0.10R to 0.16R. The radius of the second circular arc structure is d3, and the value of d3 ranges from 0.04R to 0.11R.

4. The piston according to claim 3, characterized in that, The throat (20) has a rounded corner structure and the radius of the throat (20) is d4, the value of which ranges from 2mm to 4.5mm.

5. The piston according to claim 4, characterized in that, The combustion bowl structure also includes an inner edge (30), which is located between the throat (20) and the outer edge (40). The combustion surface (10) between the inner edge (30) and the throat (20) is recessed inward to form a third arc structure. The radius of the third arc structure is d5, and the value of d5 is from 0.13R to 0.19R. The inner edge (30) is a rounded corner structure, and the radius of the inner edge (30) is d6, and the value of d6 is from 1 to 2.5mm.

6. The piston according to claim 5, characterized in that, The combustion surface (10) between the inner edge (30) and the outer edge (40) is concave inward and forms a fourth arc structure and a transition arc in sequence. The radius of the fourth arc structure is d7, and the value of d7 is in the range of 0.15R to 0.29R. The radius of the transition arc is d8, and the value of d8 is in the range of 0.20R to 0.35R.

7. A combustion system, characterized in that, include: Cylinder liner and cylinder head; The piston according to any one of claims 1 to 6 is disposed within the cylinder liner, and the combustion surface (10) of the piston body (100) and the cylinder head together form a combustion chamber; The injector (200) has a first nozzle (201) and a second nozzle (202) spaced apart along the axial direction of the piston, the first nozzle (201) being located above the second nozzle (202), and the amount of fuel injected by the first nozzle (201) being 30% to 40% of the total amount of fuel injected.

8. The combustion system according to claim 7, characterized in that, The spray cone angle of the first nozzle (201) is greater than that of the second nozzle (202), and the difference between the spray cone angle of the first nozzle (201) and the spray cone angle of the second nozzle (202) is in the range of 4° to 12°.

9. The combustion system according to claim 7, characterized in that, The area where the first nozzle (201) sprays oil toward the combustion surface (10) is designated as the first region (2011), and the area where the second nozzle (202) sprays oil toward the combustion surface (10) is designated as the second region (2021). The portion of the groove (11) located in the first region (2011) is designated as the first groove, and the portion of the groove (11) located in the second region (2021) is designated as the second groove. The volume of the first groove is V1, and the volume of the second groove is V2. The volume ratio between the first groove and the second groove is V1. Wherein, r1 is the aperture of the first nozzle (201) and r2 is the aperture of the second nozzle (202).

10. The combustion system according to claim 9, characterized in that, The first groove has a first width w1 and a first depth h1, wherein the value of the first width w1 ranges from [value missing]. The range of values ​​for the first depth h1 is: ; The second groove has a second width w2 and a second depth h2, wherein the value of the second width w2 is within the range of... The range of values ​​for the second depth h2 is: ; Wherein, R is the radius of the piston body (100), and trajpar is the trajectory parameter.

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