Volume bomb model for analyzing ignition process of low-activity fuel

Abstract

The invention relates to a volume bomb model for analyzing the ignition process of low-activity fuel, and the model comprises a volume bomb which is a cylinder or a semi-cylinder and is internally provided with a spraying hole assembly, and the axis of the spraying hole assembly is perpendicular to the axis of the volume bomb; the spraying hole assembly comprises an ignition spraying hole and at least one fuel spraying hole, the ignition spraying hole is formed in the eccentric position of the containing bomb, the fuel spraying hole is formed in the axis position of the containing bomb, and the spraying range of the ignition spraying hole at least partially coincides with the spraying range of the adjacent fuel spraying hole. According to the volume bomb model, the multiple fuel spraying holes are formed in the axis position of the volume bomb, the ignition spraying holes are formed in the eccentric position, and the axes of the ignition spraying holes intersect with the axes of the adjacent fuel spraying holes, so that first fuel beams sprayed out of the adjacent fuel spraying holes are directly ignited by the ignition fuel beams sprayed out of the ignition spraying holes; meanwhile, the second fuel beams sprayed out of the other fuel spraying holes are indirectly ignited, and direct ignition and indirect ignition can be studied at the same time; and the combustion problem of premixed dual fuels can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of fuels, and relates to low-activity fuels, in particular to a bomb-capacity model for analyzing the ignition process of low-activity fuels. Background Art

[0002] At present, the low-carbon and zero-carbon fuels commonly used in internal combustion engines mainly include natural gas, methanol, ammonia and hydrogen fuels, etc. Their ignition properties are much lower than diesel, and it is difficult to directly perform compression ignition combustion on compression ignition internal combustion engines. The traditional volume bomb model injects low-activity fuel at low pressure in the intake port, and realizes methanol compression ignition by igniting the low-activity homogeneous mixture directly injected into the diesel cylinder near the top dead center. There are the following problems:

[0003] 1. During the combustion process, misfire or partial combustion is prone to occur under low load conditions, and rough combustion or detonation is prone to occur under medium and high load conditions, which seriously limits the replacement rate of low-activity fuels. In actual applications, the overall replacement rate is only 30%-40%, and the carbon emission reduction effect is limited, and the practical application significance is not great;

[0004] 2. The bomb has a cylindrical structure. Generally, there is only one fuel nozzle in the bomb, and the axis of the fuel nozzle coincides with the axis of the bomb. An ignition nozzle is set at the eccentric position of the bomb. This structure can only simulate the direct ignition process of diesel on a single low-activity fuel oil beam under unrestricted conditions, but cannot simulate indirect ignition. In addition, the coincidence of the axis of the fuel nozzle and the axis of the bomb makes the space occupied by the fuel during the combustion process much smaller than the internal space of the bomb, resulting in the equivalent ratio of the cylindrical bomb being much lower than the equivalent ratio of the actual engine, and it is impossible to accurately simulate the combustion conditions of the actual engine.

[0005] Therefore, we propose a capacitive model for analyzing the ignition process of low-activity fuel to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a bomb-capacity model with high substitution rate and accurate simulation for analyzing the ignition process of low-activity fuel.

[0007] To solve the above problems, the technical solution of the present invention is:

[0008] A capacitive model for analyzing the ignition process of low-activity fuels, including:

[0009] The container bomb is a cylinder or a semi-cylinder, and a spray hole assembly is arranged inside, and the axis of the spray hole assembly is perpendicular to the axis of the container bomb;

[0010] The spray hole assembly includes a pilot spray hole and at least one fuel spray hole. The pilot spray hole is arranged at an eccentric position of the bomb container, and the fuel spray hole is arranged at an axial position of the bomb container. The spray range of the pilot spray hole at least partially overlaps with the spray range of the adjacent fuel spray hole.

[0011] In a further embodiment, when the number of the fuel injection holes is greater than or equal to two, a horizontal angle is formed between adjacent fuel injection holes.

[0012] In a further embodiment, the angle between adjacent fuel injection holes is 36 degrees to 60 degrees.

[0013] In a further embodiment, the height of the bullet container is 0.2 to 0.4 times the radius.

[0014] A method for constructing a containment model for analyzing the ignition process of low-activity fuels comprises the following steps:

[0015] Step S101: Establishing a bullet-proof model

[0016] Constructing a bomb container, the structure of which is as described in any one of claims 2 to 4;

[0017] Step S103: Setting the nozzle assembly

[0018] A spray hole assembly is arranged inside the bomb container, and the structure and position of the spray hole assembly are as described in any one of claims 2 to 4;

[0019] Step S105: Setting reaction conditions and reaction model

[0020] Set the temperature, pressure and gas composition inside the bomb;

[0021] Setting up a spray sub-model, a flow sub-model and a chemical reaction sub-model in the container;

[0022] The fuel composition and injection pressure of the pilot nozzle and the fuel nozzle are respectively set;

[0023] Step S107: Simulating the combustion process

[0024] Carry out simulated combustion and obtain data of the combustion process.

[0025] In a further embodiment, in step S101, in establishing a bomb container model, the internal space of the bomb container is gridded.

[0026] In a further embodiment, step S103 sets the nozzle assembly so that the pilot fuel beam sprayed from the pilot nozzle directly ignites the first fuel beam sprayed from the adjacent fuel nozzle and indirectly ignites the second fuel beam sprayed from the remaining fuel nozzles.

[0027] In a further embodiment, the pilot fuel bundle is a high-activity fuel, and the first fuel bundle and the second fuel bundle are both low-activity fuels.

[0028] In a further embodiment, in step S105, in setting the reaction conditions and reaction model, the temperature inside the bomb is set to 600 K to 1000 K, the pressure is set to 4 MPa to 8 MPa, and the gas composition is set to 79% nitrogen and 21% oxygen.

[0029] In a further embodiment, the flow sub-model adopts a RANS model, and the chemical reaction sub-model adopts a binary fuel chemical reaction model of high-activity fuel-low-activity fuel;

[0030] The spray sub-models include: spray droplet breakup model, using the KH-RT model; spray droplet collision model, using the NTC collision model; spray wall interaction model, using the Wall film with O'Rourke splash model.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This bomb model sets a number of fuel nozzles at the axial position of the bomb, and sets a pilot nozzle at an eccentric position. The axis of the pilot nozzle intersects with the axis of the adjacent fuel nozzle, so that the first fuel beam sprayed from the adjacent fuel nozzle is directly ignited by the pilot fuel beam sprayed from the pilot nozzle, and the second fuel beams sprayed from the remaining fuel nozzles are indirectly ignited, so that direct ignition and indirect ignition can be studied at the same time; and the combination of direct ignition and indirect ignition can well solve the combustion problem existing in premixed dual fuels, and the maximum substitution rate reaches more than 90%, which greatly improves the carbon emission reduction effect.

[0033] 2. The axis of the nozzle of this bomb-capacitor model is perpendicular to the axis of the bomb-capacitor. Compared with the setting in which the axis of the nozzle coincides with the axis of the cylinder in the traditional bomb-capacitor model, the geometric structure is optimized to better reflect the influence of fuel heat release on the thermodynamic properties of the working fluid during ignition and the interaction between the fuel oil beam and the wall surface; and it can greatly reduce the bomb-capacitor space, improve the fuel equivalence ratio, and make the ignition process in the bomb-capacitor closer to the ignition process in the internal combustion engine, which has practical application significance.

[0034] 3. In this bomb model, under the condition of off-axis ignition, due to the various forms of spatial interaction between the pilot oil jet and the low-activity fuel oil jet, the low-activity fuel oil jet can be directly ignited by the pilot oil jet or ignited by the adjacent oil jet or spontaneously combust. At the same time, the ignition position can also be the head, middle and tail of the oil jet. The ignition method is flexible and diverse, and the ignition efficiency is high. The position of the pilot oil jet and the low-activity fuel oil jet can be arranged more flexibly, which can be adjusted according to different target engines and has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of a bomb-capacity model for analyzing the ignition process of low-activity fuel;

[0036] Figure 2 It is a heat release rate line graph of a bomb-capacity model used to analyze the ignition process of low-activity fuel;

[0037] Figure 3 The figure is a flow chart for constructing a containment model for analyzing the ignition process of low-activity fuel.

[0038] In the figure: 1, bomb container; 2, pilot nozzle; 21, pilot fuel bundle; 3, fuel nozzle; 31, first fuel bundle; 32, second fuel bundle; α, angle. DETAILED DESCRIPTION

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0040] Embodiment 1:

[0041] A capacitive model for analyzing the ignition process of low-activity fuels, such as Figure 1 As shown, the bomb container 1 is a cylinder or a semi-cylinder, the side of the cylinder or the semi-cylinder is an arc-shaped structure, the radius of the cylinder or the semi-cylinder is equivalent to the circular radius of the upper edge of the target engine piston pit, and the height of the cylinder or the semi-cylinder is generally 0.2 times to 0.4 times the radius, so that the shape of the bomb container 1 is close to a pie-shaped structure, and the proportion of air can be minimized, so that the total equivalent ratio of the bomb container 1 is more in line with the total equivalent ratio of the actual engine. Preferably, the radius of the bomb container 1 is set to 40mm-100mm.

[0042] A spray hole assembly is arranged inside the bomb container 1, and the spray hole assembly includes an ignition spray hole 2 and a plurality of fuel spray holes 3. The ignition spray hole 2 is arranged at an eccentric position of the bomb container 1, and the ignition spray hole 2 has a certain angle. A plurality of fuel spray holes 3 are arranged at the axial position of the bomb container 1, and the axial line of the pilot spray hole 2 intersects with the axial line of the adjacent fuel spray holes 3 in the horizontal direction, so as to ensure that the ignition fuel beam 21 sprayed from the pilot spray hole 2 intersects with the first fuel beam 31 sprayed from the adjacent fuel spray holes 3, thereby directly igniting the first fuel beam 31; the number of fuel spray holes 3 is set according to demand. If it is necessary to conduct research on the direct ignition process, only one fuel spray hole 3 is required, and the first fuel beam 31 can be directly ignited by the ignition fuel beam 21 of the pilot spray hole 2; if it is necessary to conduct indirect ignition According to the research on the ignition process, at least two fuel injection holes 3 are set. In this embodiment, the number of fuel injection holes 3 is two, and the angle α between the axes of adjacent fuel injection holes 3 is 36°-60°. The size of the specific angle α corresponds to the number of nozzles of the target engine. For example, if the target engine is provided with 10-hole nozzles, the angle α between adjacent fuel injection holes 3 is 36°. If the target engine is provided with 6-hole nozzles, the angle α between adjacent fuel injection holes 3 is 60°. While the ignition fuel beam 21 directly ignites the first fuel beam 31, the second fuel beam 32 ejected from the remaining fuel injection holes 3 is indirectly ignited; the fuel injection pressure is set according to the injection pressure range of the ignition fuel and the low-activity fuel of the target engine. Preferably, the first fuel beam 31 and the second fuel beam 32 use methanol fuel, and the ignition fuel beam 21 uses diesel fuel; the total calorific value of diesel fuel accounts for 5%-10%.

[0043] Embodiment 2:

[0044] A capacitive model for analyzing the ignition process of low-activity fuels, such as Figure 2 , Figure 3 As shown, establishing the bullet-proof model also includes the following steps:

[0045] Step S101: Establishing a bullet-proof model

[0046] Construct the bomb container 1 in the simulation software, and divide the internal space of the bomb container 1 into grids, with the basic grid size not exceeding 2 mm, so that the basic grid size can take into account both calculation speed and calculation accuracy according to requirements;

[0047] Then, the radius and height of the bomb container 1 are set according to the requirements, wherein the radius of the bomb container 1 is equivalent to the circular radius of the upper edge of the target engine piston pit, and the height of the bomb container 1 is set to 0.2-0.4 times the radius. Preferably, the radius of the bomb container 1 is set to 30 mm and the height is set to 10 mm; the radius of the arc-shaped side of the bomb container 1 is 5 mm.

[0048] Step S103: Setting the nozzle assembly

[0049] A virtual nozzle assembly is arranged inside the bomb container 1, namely, an ignition nozzle 2 and a plurality of fuel nozzles 3. The ignition nozzle 2 is arranged at an eccentric position of the bomb container 1, and the plurality of fuel nozzles 3 are arranged at an axial position of the bomb container 1. The axis of the ignition nozzle 2 intersects with the axis of the adjacent fuel nozzle 3, and the axes of the plurality of fuel nozzles 3 have an angle α in the horizontal direction.

[0050] Step S105: Setting reaction conditions and reaction model

[0051] The temperature, pressure and gas composition inside the bomb 1 are set, wherein the temperature is set to 600K-1000K, the pressure is set to 4MPa-8MPa, and the gas composition is set to 79% nitrogen and 21% oxygen. The nitrogen ratio can also be increased as needed to increase the dilution degree, thereby controlling the intensity of the combustion reaction. The initial parameter settings of the bomb 1 are shown in Table 1:

[0052] Table 1

[0053] parameter Numeric Initial pressure / MPa 5,6,7,8 Initial temperature / K 1000

[0054] A spray sub-model, a flow sub-model and a chemical reaction sub-model are set inside the container 1, wherein the flow sub-model adopts the RANS model; the chemical reaction sub-model adopts the binary fuel chemical reaction model of diesel-low activity fuel, or the chemical reaction model corresponding to other target fuels of the study; the spray sub-models include: a spray droplet breakup model, which adopts the KH-RT model; a spray droplet collision model, which adopts the NTC collision model; and a spray wall interaction model, which adopts the Wall film with O'Rourke splash model.

[0055] According to the intake boundary conditions of the target engine and the thermodynamic boundary conditions in the vicinity of the top dead center, different temperatures, pressures and gas components are set for the pilot nozzle 2 and the plurality of fuel nozzles 3; the parameters of the pilot nozzle 2 are shown in Table 2:

[0056] Table 2

[0057] project parameter Number of nozzles 1 Aperture / mm 0.1 Injection pressure / MPa 40 Injection duration / ms 0.11 Injection time / ms 0

[0058] The parameters of the fuel injection hole 3 are shown in Table 3:

[0059] Table 3

[0060] project parameter Number of nozzles 2 Aperture 0.2 Injection pressure / MPa 80 Injection duration / ms 0.67 Injection time / ms 1.0

[0061] Step S107: Simulating the combustion process

[0062] A high-activity fuel is set for the pilot nozzle 2 as the pilot fuel, such as diesel; a low-activity fuel is set for the fuel nozzle 3 as the combustion fuel, such as methanol fuel or ammonia fuel, etc.; the combustion simulation is started, the pilot fuel beam 21 sprayed from the pilot nozzle 2 directly ignites the first fuel beam 31 sprayed from the adjacent fuel nozzle 3, and indirectly ignites the second fuel beam 32 sprayed from the remaining fuel nozzles 3. After the combustion is completed, the data is recorded and analyzed to complete the simulated combustion process.

[0063] The heat release rate of the combustion process is Figure 2 As shown, it can be concluded that the ignition fuel bundle 21, the first fuel bundle 31, and the second fuel bundle 32 release heat in sequence and the heat release rate increases in sequence. Therefore, compared with the method of only setting direct ignition, this combination of indirect ignition and direct ignition can greatly improve the heat release rate of low-activity fuel, make full use of low-activity fuel, and greatly improve the overall substitution rate in practical applications.

[0064] The ignition delay period data of the combustion process is shown in Table 4:

[0065] Table 4

[0066]

[0067]

[0068] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A bomb-capacity model for analyzing the ignition process of low-activity fuels, characterized in that: include: The container bomb (1) is a cylinder or a semi-cylinder, and a spray hole assembly is arranged inside, and the axis of the spray hole assembly is perpendicular to the axis of the container bomb (1); The spray hole assembly comprises an ignition spray hole (2) and at least one fuel spray hole (3); the ignition spray hole (2) is arranged at an eccentric position of the container (1); the fuel spray hole (3) is arranged at an axial position of the container (1); and the spray range of the ignition spray hole (2) at least partially overlaps with the spray range of the adjacent fuel spray hole (3).

2. The bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 1, characterized in that: When the number of the fuel injection holes (3) is greater than or equal to two, a horizontal angle (α) is formed between adjacent fuel injection holes (3).

3. The bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 2, characterized in that: The included angle (α) between adjacent fuel injection holes (3) is 36 degrees to 60 degrees.

4. The bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 3, characterized in that: The height of the bullet container (1) is 0.2 to 0.4 times the radius.

5. A method for constructing a containment model for analyzing the ignition process of low-activity fuels, characterized in that: The following steps are involved: Step S101: Establishing a bullet-proof model Constructing the bomb container (1), wherein the structure of the bomb container (1) is as described in any one of claims 2 to 4; Step S103: Setting the nozzle assembly The spray hole assembly is arranged inside the container (1), and the structure and position of the spray hole assembly are as described in any one of claims 2 to 4; Step S105: Setting reaction conditions and reaction model Setting the temperature, pressure and gas composition inside the bomb (1); A spray sub-model, a flow sub-model and a chemical reaction sub-model are set in the container (1); The fuel composition and injection pressure of the pilot injection hole (2) and the fuel injection hole (3) are respectively set; Step S107: Simulating the combustion process Carry out simulated combustion and obtain data of the combustion process.

6. The method for constructing a bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 5, characterized in that: In the step S101 of establishing a bomb container model, the internal space of the bomb container (1) is gridded.

7. The method for constructing a bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 6, characterized in that: In the step S103, in the nozzle assembly, the pilot fuel beam (21) ejected from the pilot nozzle (2) directly ignites the first fuel beam (31) ejected from the adjacent fuel nozzle (3), and at the same time indirectly ignites the second fuel beam (32) ejected from the remaining fuel nozzles (3).

8. The method for constructing a bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 7, characterized in that: The pilot fuel bundle (21) is a high-activity fuel, and the first fuel bundle (31) and the second fuel bundle (32) are both low-activity fuels.

9. The method for constructing a bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 8, characterized in that: In the step S105 of setting the reaction conditions and the reaction model, the temperature inside the container (1) is set to 600 K to 1000 K, the pressure is set to 4 MPa to 8 MPa, and the gas composition is set to 79% nitrogen and 21% oxygen.

10. The method for constructing a bomb-capacity model for analyzing the ignition process of low-activity fuel according to claim 9, characterized in that: The flow sub-model adopts the RANS model, and the chemical reaction sub-model adopts a binary fuel chemical reaction model of high-activity fuel-low-activity fuel; The spray sub-models include: a spray droplet breakup model, which adopts the KH-RT model; a spray droplet collision model, which adopts the NTC collision model; and a spray wall interaction model, which adopts the Wall film with O'Rourke splash model.

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