A heavy-duty natural gas engine combustion system

Abstract

The present invention discloses a heavy-duty natural gas engine combustion system, including a cylinder and a cylinder head covering the cylinder, a composite intake duct composed of a vortex intake duct and a straight tumble intake duct is arranged on the cylinder head and is connected to the inside of the cylinder through an intake valve equipped with an intake valve, the intake valve is installed on the valve seat, the intake valve is located in the entire valve seat, two exhaust duct inlets are connected to the inside of the cylinder through exhaust valves installed on the cylinder head, a spark plug device is installed at the center of the bottom surface of the cylinder head, a steel piston is arranged in the cylinder head, the bottom surface of the cylinder head, the inner wall surface of the cylinder and the top surface of the piston form a space as a constricted combustion chamber, and the gas supply and injection system are respectively installed on the two intake ducts or the bottom surface of the cylinder head. The present invention has a simple and compact structure, is easy to manufacture and assemble, and while using a steel piston to achieve low heat dissipation, can also form an oblique axis vortex around the central axis of the cylinder through the composite intake duct to increase the turbulent kinetic energy in the cylinder, thereby improving the thermal efficiency.

Description

Technical Field

[0001] The present invention relates to an engine combustion system, and more particularly to a heavy-duty natural gas engine combustion system. Background Art

[0002] Heavy-duty natural gas engines have advantages in achieving low-carbon and clean combustion, but due to the relatively large spatial scale of the combustion chamber of heavy-duty engines and the low propagation rate of natural gas flames, the tendency to detonation is increased, which limits the increase in compression ratio. These factors have an adverse effect on thermal efficiency. At the same time, since a stoichiometric air-fuel ratio or a slightly lean mixture is usually used, the combustion temperature in the cylinder is high. On the one hand, the heat transfer loss is large, which affects the thermal efficiency. On the other hand, the engine heat load is high, which affects reliability. In addition, heavy-duty natural gas engines mostly use aluminum alloy pistons, which have large heat transfer losses and poor mechanical and thermal load tolerance, making it difficult to meet reliability requirements. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a heavy-duty natural gas engine combustion system that increases the turbulent kinetic energy in the cylinder, accelerates the flame propagation speed, reduces the knock tendency, and improves the thermal efficiency.

[0004] To achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

[0005] A heavy-duty natural gas engine combustion system of the present invention comprises a cylinder and a cylinder head covering the cylinder, wherein two intake passages are arranged on the cylinder head and are connected to the inside of the cylinder through an intake valve equipped with an intake valve, and two exhaust passage inlets are connected to the inside of the cylinder through an exhaust valve installed on the cylinder head, a spark plug device is installed at the center of the bottom surface of the cylinder head, a steel piston is arranged in the cylinder, and the space surrounded by the bottom surface of the cylinder head, the inner wall surface of the cylinder and the top surface of the piston serves as a constricted combustion chamber, the two intake passages are respectively a vortex intake passage and a straight tumble intake passage, the vortex intake passage comprises a straight flow section and a spiral valve cavity and an intake valve connected in sequence, the outlet of the spiral valve cavity is connected to the inlet of the intake valve, and the outlet of the spiral valve cavity can make the intake air flow form a transverse vortex around the vertical center axis of the cylinder at the intake valve;

[0006] The outlet end of the straight tumble flow inlet duct is arranged tangentially along the inlet end of the intake valve. The outlet of the straight tumble flow inlet duct can enable the intake air flow to form a longitudinal vortex in the vertical axis direction around the vertical center axis of the cylinder at the intake valve. The gas supply and injection system is installed on the vortex inlet duct and the straight tumble flow inlet duct, or on the bottom surface of the cylinder head.

[0007] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0008] The heavy-duty natural gas engine combustion system provided by the present invention not only uses a steel piston to achieve low heat dissipation, but also realizes the coordinated airflow movement of the transverse and longitudinal vortices and the coupling with the constricted combustion chamber structure through the vortex and straight tumble inlet duct, and utilizes the transverse vortex to have a better macroscopic large-scale flow retention ability, which can be sustained to the expansion stroke, promoting the expansion of the large-scale flame surface; and utilizes the longitudinal airflow to break into small-scale turbulence during the compression process to accelerate the propagation of small-scale flames. The ECU adjusts the rotating valve plate axis to change the angle of the guide valve plate, guides the direction of the transverse and longitudinal vortex movement in the cylinder, and makes the intake airflow direction as close to the center of the cylinder as possible, forming an oblique axis vortex around the central axis of the cylinder, thereby increasing the turbulent kinetic energy in the cylinder, accelerating the propagation speed of the flame, reducing the tendency of knocking, and improving thermal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0010] Figure 1 It is a schematic diagram of the overall structure and layout of the intake and exhaust passages in the combustion system of a heavy-duty natural gas engine of the present invention;

[0011] Figure 2 It is a schematic diagram of the lateral vortex viewed from above on the top surface of the cylinder head;

[0012] Figure 3 It is a schematic diagram of the longitudinal vortex in the cylinder from the front view;

[0013] Figure 4 It is a schematic diagram of the structure of the valve plate shaft and the guide valve plate in each intake passage;

[0014] Figure 5 It is a front view cross-sectional schematic diagram of the airflow condition during the compression stroke of an example of the present invention.

[0015] Figure markings: 1-swirl intake duct, 1-1-spiral valve chamber, 2-straight tumble intake duct, 3-valve shaft, 3-1-guide valve plate, 3-2-electric actuator, 4-intake valve, 5-intake valve, 6-cylinder head, 7-exhaust duct inlet, 8-exhaust valve, 9-spark plug, 10-cylinder, 11-recessed combustion chamber, 12-steel piston, L-axis line, a-direct current section. DETAILED DESCRIPTION

[0016] To further illustrate the functional structure of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and preferred embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments, and the protection scope of the present invention is not limited to the specific implementation methods.

[0017] like Figure 1 As shown, the heavy-duty natural gas engine combustion system provided by the present invention includes a cylinder 10 and a cylinder head 6 covering the cylinder, two intake passages are arranged on the cylinder head 6 and are connected to the interior of the cylinder 10 through an intake valve 4 equipped with an intake valve 5, the intake valve 5 is installed on the valve seat, the intake valve 4 is located in the entire valve seat, two exhaust passage inlets 7 are connected to the interior of the cylinder 10 through an exhaust valve 8 installed on the cylinder head 6, a spark plug device 9 is installed at the center of the bottom surface of the cylinder head 6, a steel piston 12 is arranged in the cylinder 10, and the space surrounded by the bottom surface of the cylinder head, the inner wall surface of the cylinder and the top surface of the piston serves as a constricted combustion chamber 11.

[0018] The above structure is the existing structure of the engine, and the improvements of the present invention are as follows:

[0019] The two intake passages are respectively a vortex intake passage 1 and a straight tumble intake passage 2. The vortex intake passage 1 comprises a straight section a and a spiral valve chamber 1-1 connected in sequence, the outlet of the spiral valve chamber 1-1 is connected to the inlet of the intake valve 4, and the outlet of the spiral valve chamber 1-1 can form a lateral vortex around the vertical center axis of the cylinder 10 at the intake valve 4. Figure 2 shown.

[0020] In order to form a lateral vortex, the structure of the spiral valve chamber 1-1 can be: the ratio of the outer radius R1 of the spiral valve chamber 1-1 to the radius r of the inlet end of the intake valve 4 is 1.1-1.2, and the ratio of the inner radius R2 of the spiral valve chamber 1-1 to the radius r of the inlet end of the intake valve 4 is 0.5-0.6. For the definitions of the various parameters involved in this paragraph, please refer to pages 337-344 of the "Automotive Engineering" journal published in 2021.

[0021] The outlet end of the straight tumble inlet duct 2 is tangentially arranged along the inlet end of the intake valve 4, that is, the outlet end of the straight tumble inlet duct 2 is smoothly connected to the inlet end of the intake valve 4. The outlet of the straight tumble inlet duct 2 can form a longitudinal vortex in the vertical axis direction around the vertical center axis of the cylinder 10 at the intake valve 4. Figure 3 shown.

[0022] A valve shaft 3 connected to an electric actuator 3-2 is installed in each of the vortex inlet duct 1 and the straight tumble inlet duct 2. The electric actuator 3-2 is connected to the ECU through a control line. The valve shaft 3 is perpendicular to the axis L of the straight section a in each corresponding inlet duct. A guide valve plate 3-1 is fixed on the valve shaft 3. Figure 4 As shown, the valve plate shaft 3 provided in each intake duct is close to one side of the intake valve 4, and the guide valve plate 3-1 can rotate in the intake duct driven by the valve plate shaft 3. In the initial state, the guide valve plate 3-1 is in a position parallel to the axis L of the direct section a of the intake duct, and is controlled by the ECU to rotate along the fan-shaped trajectory to a set angle and then stop. After the rotation stops, the guide valve plate 3-1 forms an acute angle A with the vertical plane of the intake duct axis L, and the acute angle A ranges from 45° to 60°, so that the intake airflow is guided by the guide valve plate 3-1, and the gas flow rate is increased to form a strong vortex motion.

[0023] The gas supply and injection system can be respectively installed on the vortex inlet 1 and the straight tumble inlet 2 or on the bottom surface of the cylinder head 6. The gas supply and injection system can adopt the existing structure.

[0024] The vortex inlet duct 1 satisfies the requirement that, in the absence of the valve shaft 3, the initial airflow can form a certain intensity of rotation in the spiral inlet duct, and form a transverse vortex at the inlet valve 4. The valve shaft 3 provided in the vortex inlet duct 1 can change the angle of the guide valve plate 3-1 on the valve shaft 3 by adjusting the rotation of the ECU, so that when the intake airflow enters the cylinder 10, the inlet direction of the intake airflow is as close to the center of the cylinder as possible, forming a transverse vortex motion around the vertical center axis of the cylinder 10.

[0025] The straight tumble inlet duct 2 can guide the initial airflow into the cylinder 10 through the tangential connection port of the air duct without the valve shaft 3, and form a longitudinal vortex at the intake valve 4. The valve shaft 3 arranged in the straight tumble inlet duct 2 can change the angle of the guide valve plate 3-1 on the valve shaft 3 by adjusting and rotating the valve shaft 3 through the ECU, so that when the intake airflow enters the cylinder 10, the inlet direction of the intake airflow is as close to the center of the cylinder as possible, forming a longitudinal vortex motion in the vertical axis direction around the vertical center axis of the cylinder 10.

[0026] like Figure 5As shown, the lateral vortex generated by the vortex intake duct 1 and the longitudinal vortex generated by the straight tumble intake duct 2 are used. The ECU adjusts the rotating valve plate shaft 3 to change the angle of the guide valve plate 3-1 to change the position of the airflow inlet, so that the direction of the intake airflow inlet is as close to the center of the cylinder as possible. The use of the steel piston 12 not only improves the overall pressure resistance of the piston, but also ensures the effective operation of the inner cooling oil cavity and heat dissipation and cooling. During the upward compression of the steel piston, the lateral and longitudinal vortices are combined into an oblique axis vortex that is biased toward the center of the constricted combustion chamber 11, so that the lateral and longitudinal vortices entering the constricted combustion chamber 11 from the intake duct form a high turbulent kinetic energy area near the center of the spark plug 9 electrode near the top dead center, and while the steel piston 12 is used to achieve low heat dissipation, the thermal efficiency is further improved.

[0027] The control method of the device can be calibrated by using the process of determining the control method of the existing device.

[0028] Test results:

[0029] The present invention adopts a steel piston, which improves the overall strength of the piston, reduces thermal expansion, improves reliability and achieves better heat dissipation and cooling effects. In addition, the composite intake duct matches the tapered combustion chamber, so that the intake airflow guides the lateral and longitudinal vortex directions in the cylinder as much as possible toward the center of the cylinder through the ECU to control the angle of the guide valve plate, forming an oblique axis vortex around the central axis of the cylinder, increasing the turbulence intensity near the spark plug at the ignition moment, accelerating the flame propagation speed, significantly reducing the knock tendency, and improving thermal efficiency.

[0030] Finally, it should be noted that: although the above-mentioned combined figures describe the present invention, the above design of the combustion system for the method of the present invention is only a preferred implementation method and is not limited to the above-mentioned technical scheme. The above-mentioned specific implementation method is only illustrative and not mandatory. Under the guidance of the present invention, ordinary technicians in this field can also make many modifications without departing from the purpose of the present invention, which are all within the protection of the present invention.

Claims

1. A heavy-duty natural gas engine combustion system, comprising a cylinder and a cylinder head covering the cylinder, wherein two intake passages are arranged on the cylinder head and are connected to the interior of the cylinder through an intake valve equipped with an intake valve, and two exhaust passage inlets are connected to the interior of the cylinder through an exhaust valve installed on the cylinder head, a spark plug device is installed at the center of the bottom surface of the cylinder head, a steel piston is arranged in the cylinder, and the space enclosed by the bottom surface of the cylinder head, the inner wall surface of the cylinder and the top surface of the piston serves as a constricted combustion chamber, characterized in that: The two inlet passages are respectively a vortex inlet passage and a straight tumble inlet passage, the vortex inlet passage comprises a straight section, a spiral valve chamber and an inlet valve connected in sequence, the outlet of the spiral valve chamber is connected to the inlet of the inlet valve, and the outlet of the spiral valve chamber can make the intake air flow form a transverse vortex around the vertical center axis of the cylinder at the inlet valve; The outlet end of the straight tumble flow inlet duct is arranged tangentially along the inlet end of the intake valve, and the outlet of the straight tumble flow inlet duct can form a longitudinal vortex in the vertical axis direction around the vertical center axis of the cylinder at the intake valve. The gas supply and injection system is installed on the vortex flow inlet duct and the straight tumble flow inlet duct, or on the bottom surface of the cylinder head. A valve plate shaft connected to an electric actuator is respectively installed in the vortex flow inlet duct and the straight tumble flow inlet duct. The electric actuator is connected to the ECU through a control line. The valve plate shaft is perpendicular to the axis of the direct current section in each corresponding intake duct. A guide valve plate is fixed on the valve plate shaft. The valve plate shaft provided in each intake duct is close to one side of the intake valve. The guide valve plate can rotate in the intake duct driven by the valve plate shaft. The angle of the guide valve plate is changed by adjusting the rotating valve plate shaft by the ECU to guide the lateral and longitudinal vortex movement directions in the cylinder, so that the direction of the intake air flow is as close to the center of the cylinder as possible, forming an oblique axis vortex around the center axis of the cylinder.

2. The heavy-duty natural gas engine combustion system according to claim 1, characterized in that: The guide valve plate forms an acute angle A with a plane perpendicular to the axis of the air inlet duct, and the acute angle A has a value range of 45°-60°.

3. The heavy-duty natural gas engine combustion system according to claim 1 or 2, characterized in that: The structure of the spiral valve cavity is as follows: the ratio of the outer radius of the spiral valve cavity to the radius of the inlet end of the intake valve is 1.1-1.2, and the ratio of the inner radius of the spiral valve cavity to the radius of the inlet end of the intake valve is 0.5-0.6.

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