A combustion chamber with low dissipation and high thermal efficiency under high compression ratio

Abstract

A combustion chamber with low heat dissipation and high thermal efficiency at a high compression ratio includes a fixed cylinder head and a movable piston, with the piston crown facing the inside of the cylinder head. A first flat portion is provided on the side of the piston crown facing the cylinder head, and a recessed portion is provided on the first flat portion. This invention provides a combustion chamber with low heat dissipation and high thermal efficiency at a high compression ratio, which can avoid the sluggish airflow forming a hindrance effect during intake and compression, thereby avoiding rapid heat dissipation and improving thermal efficiency.

Description

Technical Field

[0001] This invention relates to the field of engine combustion chambers, specifically a combustion chamber with low heat dissipation and high thermal efficiency at a high compression ratio. Background Technology

[0002] The function of the engine combustion chamber is to mix the fuel from the intake system and the fuel injector and then burn it under isobaric pressure to form high-temperature gas. The combustion chamber is an important component of the engine.

[0003] Currently, to improve engine thermal efficiency and reduce fuel consumption and emissions, high compression ratios, high tumble intake manifolds, high EGR (Exhaust Gas Recirculation) rates, and Atkins cycles are the mainstream technical approaches. The theoretical thermal efficiency of an engine is directly related to its compression ratio and the specific heat ratio of the working fluid; specifically, the higher the compression ratio and the specific heat ratio, the higher the thermal efficiency. The compression ratio is calculated as CR = (Vs + Vc) / Vc, where Vc is the volume enclosed by the cylinder head and piston crown at top dead center, and Vs is the displacement per cylinder. It can be seen that the smaller Vc is, the larger the compression ratio.

[0004] In addition, other factors such as combustion rate also affect thermal efficiency. Currently, the main approach is to dilute the working fluid and increase the specific heat ratio by using high EGR, and then combine this with TKE (high turbulent kinetic energy) at the ignition moment to accelerate the combustion rate and achieve high thermal efficiency.

[0005] In summary, smaller Vc and higher TKE are important means to achieve high thermal efficiency. Current technologies mainly reduce Vc by machining a protruding structure on the piston crown, and this requires machining recesses into the protruding structure to create a stable combustion space. The ramp formed by this protruding structure causes a sluggish effect in the intake tumble flow during intake and compression, increasing the dissipation rate of TKE, leading to a decrease in TKE before ignition, thus reducing the combustion rate and ultimately preventing an improvement in thermal efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies under high compression ratio combustion chamber conditions, this invention provides a combustion chamber with low dissipation and high thermal efficiency at high compression ratios. This chamber avoids the sluggish effect of tumble airflow during intake and compression, thereby preventing rapid dissipation of TKE and improving thermal efficiency.

[0007] To achieve the above objectives, the specific solution adopted by the present invention is as follows: a combustion chamber with low dissipation and high thermal efficiency under high compression ratio, comprising a fixedly disposed cylinder head and a movable piston, wherein the piston top faces the inner side of the cylinder head, and a first flat portion is provided on the side of the piston top facing the cylinder head, and a recessed portion is provided on the first flat portion.

[0008] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: the cylinder head is provided with mounting holes for installing spark plugs, and a certain height space is created between the cylinder head and the piston crown recess.

[0009] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: the cylinder head is provided with several fire surfaces that extend deep into the interior, and the fire surfaces and the combustion chamber form a more compact combustion space.

[0010] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: the cylinder head is provided with two intake valve bottoms and two exhaust valve bottoms, and the cylinder head is provided with multiple inwardly recessed parts, one of which is located between the two exhaust valve bottoms, and the other two are located between the intake valve bottoms and the exhaust valve bottoms, respectively.

[0011] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: the fire surface is provided with three, and the three fire surfaces correspond to the three recesses.

[0012] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: a second flat portion is provided on the side of the piston top facing the cylinder head, the first flat portion faces the bottom of the intake valve, and the second flat portion faces the bottom of the exhaust valve.

[0013] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: two intake valve clearance pits corresponding to the bottom of the intake valve are provided on the first flat part.

[0014] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: two exhaust valve clearance pits are provided on the second flat part, which correspond to the bottom of the exhaust valve.

[0015] As a further optimization of the combustion chamber with low dissipation and high thermal efficiency under the above-mentioned high compression ratio: the first planar portion and the second planar portion are smoothly transitioned by an inclined transition surface to minimize the adverse effects of the intake VVT ​​avoidance pit.

[0016] Beneficial effects: By eliminating the unavoidable protrusions and slopes on the top surface of traditional high compression ratio pistons, this invention avoids the sluggish airflow forming a blocking effect during intake and compression, thereby preventing rapid dissipation of TKE and improving thermal efficiency. Attached Figure Description

[0017] Figure 1 This is a top view of the cylinder head structure;

[0018] Figure 2 This is a 3D structural diagram of the cylinder head;

[0019] Figure 3 This is a three-dimensional view A of the piston top structure;

[0020] Figure 4 This is a three-dimensional view of the piston top (B).

[0021] Figure 5 This is a cross-sectional schematic diagram of the cylinder head in the embodiment;

[0022] Figure 6 This is a comparison diagram of the present invention and the prior art in the compression uplink process;

[0023] Figure 7 This is a comparison diagram of the present invention and the prior art in the compressed downlink process;

[0024] Figure 8 This is a simulation result diagram from the embodiment.

[0025] Figure descriptions: 1-Cylinder head, 2-Intake valve bottom, 3-Exhaust valve bottom, 4-Concave portion, 5-Piston top, 6-First flat surface, 7-Recessed portion, 8-Transition surface, 9-Second flat surface, 10-Intake valve clearance pit, 11-Exhaust valve clearance pit, 12-Fire surface, 13-Base surface. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figures 1 to 4 A combustion chamber with low dissipation and high thermal efficiency under high compression ratio includes a fixed cylinder head 1 and a movable piston, wherein the piston top 5 faces the inside of the cylinder head 1, a first flat portion 6 is provided on the side of the piston top 5 facing the cylinder head 1, and a recessed portion 7 is provided on the first flat portion 6.

[0028] During use, when the piston top 5 moves to the top dead center, the recessed part 7 reaches the vicinity of the spark plug. Since the first flat part 6 does not have the protruding structure and ramp structure of the traditional scheme, it can effectively avoid the intake tumble flow forming a blocking effect during the intake and compression process, thereby avoiding rapid dissipation of TKE and thus achieving the effect of improving thermal efficiency. The recessed part 7 and the cylinder head 1 can form a combustion space, forming a high TKE in the central area, ensuring that the fuel can burn efficiently.

[0029] This invention eliminates the unavoidable protrusions and ramps on the top surface of traditional high-compression pistons, especially the ramps on the exhaust side and the protrusions on both sides between the intake and exhaust, which have a significant impact on tumble dissipation. This patent avoids the tumble airflow forming a hindrance effect during intake and compression, thus achieving the effect of avoiding rapid TKE dissipation and improving thermal efficiency.

[0030] To ensure that the recessed portion 7 can move smoothly to the vicinity of the spark plug, the cylinder head 1 is provided with a mounting hole for installing the spark plug. The recessed portion 7 faces the mounting hole, which can concentrate the tumble airflow center and the high TKE zone near the spark plug during ignition.

[0031] The cylinder head 1 has the following structure: several firing surfaces 12 are provided on the cylinder head 1, and the distance between the firing surfaces 12 and the first flat portion 6 is smaller than the distance between the base surface 13 of the cylinder head 1 and the first flat portion 6. When the piston crown 5 reaches top dead center, a very small gap is formed between the firing surfaces 12 and the first flat portion 6, thereby concentrating the gas in the combustion space located in the central region, effectively improving thermal efficiency.

[0032] Because thermal efficiency is related not only to TKE (Total Kiln Equivalent) but also to the volume of the combustion space, to avoid the expansion of the combustion space caused by the first flat portion 6, which would lead to a decrease in thermal efficiency, the cylinder head 1 is provided with multiple inwardly recessed portions 4. By providing the recessed portions 4, the combustion space can be reduced, that is, the Vc (Volume Capacity) can be reduced, thereby ensuring that thermal efficiency can be improved.

[0033] The specific arrangement of the recessed portion 4 is as follows: the cylinder head 1 is provided with two intake valve bottoms 2 and two exhaust valve bottoms 3, and the cylinder head 1 is provided with multiple inwardly recessed portions 4, one of which is located between the two exhaust valve bottoms 3, and the other two are located between the intake valve bottoms 2 and the exhaust valve bottoms 3 respectively. The specific distribution of the intake valve bottoms 2 and the exhaust valve bottoms 3 is conventional technology in this field and will not be described in detail here.

[0034] The specific distribution of the spark plug surfaces 12 is as follows: there are three spark plug surfaces 12, and the three spark plug surfaces 12 correspond to three concave portions 4. It should be noted that the intersection line between the spark plug surface 12 and the concave portion 4 needs to be as close as possible to the center of the spark plug, thereby shortening the flame propagation distance, increasing the mass of the combustible mixture under the same flame propagation distance, and thus improving the heat release rate.

[0035] In order to achieve a high tumble flow under small valve lift without affecting the intake manifold masking structure, a second flat portion 9 is provided on the side of the piston top 5 facing the cylinder head 1, a first flat portion 6 faces the intake valve bottom 2, and a second flat portion 9 faces the intake valve bottom 3. By providing the second flat portion 9, the intake manifold seat back masking structure can be designed.

[0036] In order to make the space on the exhaust side smoother and fully ensure that it will not obstruct or interfere with the tumble airflow, the first flat part 6 and the second flat part 9 are connected by an inclined transition surface 8. The transition surface 8 is located on the leeward side of the tumble flow and will not interfere with the tumble flow.

[0037] Two intake valve clearance recesses 10 are provided on the first flat part 6, which correspond to the bottom of the intake valve 2.

[0038] Two exhaust valve clearance recesses 11 are provided on the second flat part 9, which correspond to the bottom of the exhaust valve 3.

[0039] Please see Figure 1 and 5 The following is a theoretical analysis of the effects of the present invention.

[0040] like Figure 5 In the MM cross-sectional view, the thick black line A represents the cylinder head combustion chamber, B represents the piston top combustion chamber, and C represents the cylinder liner with one or more rings; a represents the base surface 13 of the cylinder head 1, and the black dashed line a' represents the planar structure of the exhaust-side cylinder head 1 of the present invention that is recessed upwards, creating a height difference between it and the bottom surface a of the cylinder head 1; b represents the piston exhaust-side ramp and protrusion structure of the existing solution, which obstructs the tumble airflow, as described in the following principle. Figure 6 As shown in the comparison; b' is the piston top 5 planar structure of the present invention. Both b' and a' are machined, resulting in high dimensional accuracy. The gap between a' and b' can be controlled to be small, minimizing harmful volume and shortening flame propagation distance. d is the central recess of an existing high compression ratio piston. d' is the recess 7 of the present invention. Due to the presence of a' and b', the Vc clearance volume is squeezed smaller. Under the same Vc and compression ratio, d' can be deeper than d, which is more conducive to the formation of tumble flow and the increase of top dead center (TKE), thereby accelerating combustion. In addition, from the MM cross-section, during the piston compression upward movement, for existing high compression ratio schemes, the tumble flow formed during the intake process is hindered and disturbed by the protruding structure and the ramp structure, resulting in turbulent dissipation and deteriorating subsequent ignition and combustion. However, after the piston plane of the present invention is lifted, the exhaust side and both sides of the combustion chamber are very smooth, and the tumble flow can be effectively guided and maintained.

[0041] like Figure 5 In the NN cross-sectional view: the thick black line A represents the combustion subspace of the cylinder head 1, B represents the combustion subspace of the piston top 5, and A and B together form the combustion space; C represents the cylinder liner of the engine block with one or more rings; a represents the base surface 13 of the cylinder head 1; the black dashed line a' represents the planar structure of the cylinder head 1 on both sides of the combustion chamber of this invention, which is the same plane as a' in MM, and it creates a height difference with the bottom surface of the cylinder head 1; b represents the protruding structure on both sides of the piston in the existing solution, which also hinders the tumbling airflow, as in the principle of... Figure 7As shown in the comparison; b' is the first flat portion 6 of the piston top 5 of the present invention. Both a' and b' are machined, with high dimensional accuracy. The gap between a' and b' can be controlled to be small, minimizing harmful volume and shortening flame propagation distance. d is the central recess of an existing high compression ratio piston; d' is the central recess structure of the present invention. Due to the presence of a' and b', the Vc clearance volume is squeezed smaller. Under the same Vc and compression ratio, d' can be deeper than d, which is more conducive to the formation of tumble flow and the improvement of top dead center (TKE), thereby accelerating combustion. From the comparison of the NN cross sections, it can also be seen that the patented structure on both the intake and exhaust sides can also eliminate the turbulent dissipation of the side clearance caused by the piston's upward movement in the existing scheme.

[0042] Please see Figure 8 The invention was verified by in-cylinder transient CFD flow simulation. The simulation results show that the tumble flow field of the prior art is affected by the protruding structure and the ramp, which obstructs the airflow. However, this application eliminates these adverse effects, which increases the in-cylinder transient tumble intensity by more than 15%, increases the TKE before ignition by as much as 20%, shortens the combustion duration by more than 3°CA, and improves the engine thermal efficiency by more than 2%.

[0043] Through practical verification, using this invention, the compression ratio of the engine can reach as high as 15.5 or even higher, effectively maintaining the intensity of the tumble airflow. At the same time, the radial flame propagation distance of the combustion chamber is significantly shortened, and the combustible mixture is more centrally located compared to the prior art, resulting in higher combustion efficiency and thus improving the engine's thermal efficiency.

[0044] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A combustion chamber with low dissipation and high thermal efficiency at a high compression ratio, comprising a fixed cylinder head (1) and a movable piston, wherein the piston top (5) faces the inside of the cylinder head (1), characterized in that: The piston top (5) is provided with a first flat part (6) on the side facing the cylinder head (1), which is higher than the piston second flat part (9). When the piston runs to the vicinity of the top dead center, the first flat part (6) has exceeded the top plane of the machine body and the base surface (13) of the cylinder head and penetrates into the cylinder head. In addition, a recessed part (7) is provided on the first flat part (6). The cylinder head (1) is provided with a plurality of fire surfaces (12). The fire surfaces (12) extend into the cylinder head relative to the base surface (13). The distance between the fire surfaces (12) and the first flat part (6) is less than the distance between the base surface (13) and the first flat part (6) of the cylinder head (1). The minimum gap between the fire surfaces (12) and the first flat part (6) of the piston is ensured by machining to ensure dimensional accuracy, thereby reducing harmful volume. The cylinder head (1) has a mounting hole for installing a spark plug. The recess (7) faces the mounting hole. Due to the presence of the first flat part (6) and the fire surface (12), the recess (7) can be deepened under the same high compression ratio, forming an ignition space between the spark plug and the recess (7). The cylinder head (1) is provided with two intake valve bottoms (2) and two exhaust valve bottoms (3). The cylinder head (1) is provided with multiple inwardly recessed parts (4). One of the recessed parts (4) is located between the two exhaust valve bottoms (3), and the other two recessed parts (4) are located between the intake valve bottoms (2) and the exhaust valve bottoms (3), respectively. Due to the presence of the fire surface (12), the intersection line of the recessed part (4) and the fire surface (12) can be more concentrated and closer to the center spark plug, which effectively reduces the combustion chamber volume, is more conducive to achieving a high compression ratio, and shortens the flame propagation distance.

2. The combustion chamber with low dissipation and high thermal efficiency at a high compression ratio as described in claim 1, characterized in that: The fire-powered surface (12) is provided in three parts, and the three fire-powered surfaces (12) are close to the three recesses (4).

3. The combustion chamber with low dissipation and high thermal efficiency at a high compression ratio as described in claim 1, characterized in that: The minimum clearance between the second planar portion (9) and the base surface (13) at the top dead center is ensured by machining, thereby reducing the harmful volume of the combustion chamber.

4. The combustion chamber with low dissipation and high thermal efficiency at a high compression ratio as described in claim 3, characterized in that: Two intake valve clearance recesses (10) are provided on the first flat part (6) corresponding to the bottom of the intake valve (2), which is determined by the large operating range of intake VVT ​​and valve lift.

5. A combustion chamber with low dissipation and high thermal efficiency at a high compression ratio as described in claim 3, characterized in that: The second flat portion (9) has two exhaust valve clearance pits (11) corresponding to the bottom of the exhaust valve (3), and the depth of the exhaust valve clearance pits (11) is shallower than the depth of the intake valve clearance pits (10).

6. The combustion chamber with low dissipation and high thermal efficiency at a high compression ratio as described in claim 3, characterized in that: The first planar portion (6) and the second planar portion (9) are connected by an inclined transition surface (8). The transition surface (8) is located on the intake side and on the leeward side of the tumble airflow, and will not have a negative impact on the airflow.

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