A method for optimizing structural parameters of a high-pressure water jet coal breaking pressure relief nozzle

Abstract

The application discloses a kind of high-pressure water jet coal breaking pressure relief nozzle structure parameter optimization methods, comprising: coal body and nozzle structure features are collected, corresponding SPH particle filling type two-dimensional grid model is constructed;Based on the analysis of the influencing factors of nozzle impact coal breaking performance, a parameter theoretical model is constructed;The physical and mechanical parameters of coal and water jet are obtained and substituted into the nozzle parameter theoretical model, and the theoretical value interval of different parameters is calculated;The theoretical value of different parameters is substituted into the SPH particle filling type two-dimensional grid model for numerical simulation, the coal breaking effect under different parameters is evaluated by establishing the nozzle impact coal breaking performance degree index, and the optimal structure parameters of high-pressure water jet coal breaking pressure relief nozzle are obtained.The nozzle structure parameter optimization method of the application is more in line with the actual situation, and the optimal structure parameters obtained have higher accuracy, can derive more cracks in the coal body, and has an important role in ensuring the maximum pressure relief effect and lower pressure relief cost.

Description

Technical Field

[0001] This invention belongs to the technical field of structural parameter optimization of high-pressure water jet coal crushing and pressure relief nozzles, and in particular relates to a method for optimizing the structural parameters of high-pressure water jet coal crushing and pressure relief nozzles. Background Technology

[0002] Rockburst is a typical dynamic disaster in mines. It typically occurs when coal and rock masses reach their destructive strength limits, releasing elastic energy suddenly, rapidly, and intensely. This causes instantaneous failure of the coal and rock strata, accompanied by the impact of coal dust and rock, resulting in damage to mine tunnels and personal injury accidents. Currently, the main pressure relief measures used in coal mine roadways include borehole pressure relief, blasting pressure relief, and hydraulic fracturing. While these methods have achieved certain application results, they all have certain applicable conditions and limitations.

[0003] High-pressure water jet slotting and pressure relief technology uses high-pressure water to impact the coal seam, causing the coal to break apart and form uniform annular slots. A plastic fracture zone is created around these slots, ultimately resulting in a pressure-relieved and weakened area. This method has become an important research direction for preventing rockbursts in deep mining of coal seams prone to rockbursts. The nozzle, as a crucial component of high-pressure water jet slotting and pressure relief equipment, has seen limited research both domestically and internationally on parameters such as nozzle outlet type, outlet velocity, and outlet diameter. Inappropriate nozzle structural parameters not only significantly increase pressure relief costs but also result in lower crack propagation within the coal seam, reduced pressure relief effect in the roadway, and a persistently high risk of rockbursts at the coal face. Therefore, there is an urgent need for a method to optimize the structural parameters of high-pressure water jet coal breaking and pressure relief nozzles. Summary of the Invention

[0004] The purpose of this invention is to provide a method for optimizing the structural parameters of a high-pressure water jet coal crushing and pressure relief nozzle, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a method for optimizing the structural parameters of a high-pressure water jet coal crushing and pressure relief nozzle, comprising:

[0006] Obtain the physical and mechanical parameters of the coal body and water jet, and construct an SPH particle-filled two-dimensional mesh model based on the physical and mechanical parameters of the coal body and water jet;

[0007] Construct a theoretical model of nozzle parameters;

[0008] Substituting the physical and mechanical parameters of the coal body and water jet into the theoretical model of nozzle parameters, the theoretical value range of different nozzle parameters is calculated.

[0009] Construct an index for the performance of nozzle impact coal breaking;

[0010] Numerical simulations were performed using theoretical values ​​of different nozzle parameters and an SPH particle-filled two-dimensional mesh model. The simulation results under different parameters were evaluated based on the nozzle's coal crushing performance index, and the optimal structural parameters of the high-pressure water jet coal crushing and pressure relief nozzle were obtained.

[0011] Optionally, the construction of the SPH particle-filled two-dimensional mesh model is also based on mesh model data, which is obtained based on the structural features of the coal body and nozzle, and the geometric dimensions of the SPH particle-filled two-dimensional mesh model are obtained based on the mesh model data.

[0012] Optionally, the physical and mechanical parameters of the coal body and water jet include: coal density, coal compressive strength, tensile strength and critical failure load, bulk modulus, shear modulus and Poisson's ratio, and water jet density.

[0013] Optionally, the theoretical model of the nozzle parameters includes nozzle exit type, nozzle exit velocity, nozzle exit diameter, jet angle, and target distance.

[0014] Optionally, the SPH particle-filled two-dimensional mesh model includes a nozzle SPH particle-filled two-dimensional mesh model and a coal body SPH particle-filled two-dimensional mesh model. The construction process includes: both the coal body and the nozzle are filled with SPH particles, and the SPH particle density is set based on the physical density of the water jet in the coal body and the nozzle. The physical and mechanical parameters of the coal body and the nozzle are set, and the boundary conditions are restricted on the bottom surface and two sides of the coal body.

[0015] Optionally, the indicators of the nozzle impact coal breaking performance include: crack propagation axial ratio and crack propagation radial ratio, crack propagation crushing zone area ratio, crack number ratio within the optimal crack propagation angle, and coal breaking specific energy consumption.

[0016] Optionally, the crack propagation axial ratio and crack propagation radial ratio are obtained based on the crack depth and coal model length; the crack propagation fracture zone area ratio is obtained based on the crack propagation fracture zone area and coal model area; the crack number ratio within the optimal crack propagation angle is obtained based on the number of cracks within the optimal crack propagation angle range and the total number of cracks; and the coal breaking energy consumption is obtained based on the energy consumed by water jet impact coal breaking and the crack propagation fracture zone area.

[0017] Optionally, the simulation effect under different parameters can be evaluated based on the influence weight of each indicator in the nozzle impact coal breaking performance index.

[0018] Optionally, a theoretical model of the nozzle parameters can be constructed based on the analysis of factors affecting the nozzle's impact coal breaking performance.

[0019] The technical effects of this invention are as follows:

[0020] This invention provides a method for optimizing the structural parameters of a high-pressure water jet coal crushing and pressure relief nozzle. The method involves collecting structural characteristics of the coal body and nozzle, and constructing an SPH particle-filled mesh model. Based on the analysis of factors influencing the nozzle's impact coal crushing performance, theoretical models are constructed for nozzle outlet type, nozzle outlet velocity, nozzle outlet diameter, jet angle, and target distance parameters. The physical and mechanical parameters of the coal body and water jet are substituted into the theoretical nozzle parameter model to calculate the theoretical value ranges for different nozzle parameters. The theoretical values ​​of different nozzle parameters are then substituted into the SPH particle-filled two-dimensional mesh model for numerical simulation. An index for the nozzle's impact coal crushing performance is established to evaluate the coal crushing effect under different parameters, thus obtaining the optimal structural parameters of the high-pressure water jet coal crushing and pressure relief nozzle. The structural parameter optimization method for the high-pressure water jet coal crushing and pressure relief nozzle involved in this invention is more consistent with actual field conditions, and the obtained optimal nozzle structural parameters are more accurate. It can generate more cracks inside the coal body, playing a crucial role in maximizing the pressure relief effect and minimizing pressure relief costs. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0022] Figure 1 This is a flowchart illustrating the method for optimizing the structural parameters of the high-pressure water jet coal-breaking and pressure-relieving nozzle in an embodiment of the present invention.

[0023] Figure 2 This is a roadway layout diagram of the 6302 working face of a mine in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the SPH particle-filled mesh model constructed in this invention;

[0025] Figure 4 This is a diagram showing the evolution of impact coal crushing cracks for different nozzle outlet types in embodiments of the present invention;

[0026] Figure 5 This is a diagram showing the evolution of impact coal crushing cracks under different nozzle exit velocity parameters in an embodiment of the present invention.

[0027] Figure 6 This is a diagram showing the evolution of impact coal crushing cracks under different nozzle outlet diameter parameters in an embodiment of the present invention.

[0028] Figure 7 This is a diagram showing the evolution of impact coal breaking cracks under different jet angle parameters in an embodiment of the present invention;

[0029] Figure 8 This is a diagram showing the evolution of coal cracks caused by impact under different target distance parameters in an embodiment of the present invention. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0032] Example 1

[0033] like Figure 1-8 As shown, this embodiment provides a method for optimizing the structural parameters of a high-pressure water jet coal crushing and pressure relief nozzle, including:

[0034] Collect structural features of the coal body and nozzles, and construct an SPH particle-filled mesh model;

[0035] Based on the analysis of factors affecting the performance of nozzle impact coal breaking, a theoretical model is constructed for nozzle outlet type, nozzle outlet velocity, nozzle outlet diameter, jet angle and target distance parameters.

[0036] Substitute the physical and mechanical parameters of the coal body and water jet into the theoretical model of the nozzle parameters to calculate the theoretical value range of different nozzle parameters;

[0037] The theoretical values ​​of different nozzle parameters were substituted into the SPH particle-filled two-dimensional mesh model for numerical simulation. The coal breaking effect under different parameters was evaluated by establishing a nozzle impact coal breaking performance index, and the structural parameters of the optimal high-pressure water jet coal breaking and pressure relief nozzle were obtained.

[0038] In some embodiments, the process of collecting coal body and nozzle structural features and constructing an SPH particle-filled mesh model includes:

[0039] Based on the structural characteristics of the coal body and nozzle, the collected grid model data is as follows: coal body length l mz and width l mj Nozzle length l pj Nozzle inlet diameter D ent .

[0040] The physical and mechanical parameters of the coal body and water jet collected are as follows: coal body density ρ m Coal body compressive strength σ c Tensile strength σ t and critical failure load F p Bulk modulus K, shear modulus G, Poisson's ratio ν, water jet density ρ s wait.

[0041] A two-dimensional mesh model was constructed using the collected data. Both the coal body and the water jet were filled with SPH particles, and the corresponding SPH particle density was set according to their physical density. The physical and mechanical parameters of the coal body and the water jet were set, and the bottom and two sides of the coal body model were constrained by boundary conditions.

[0042] In some embodiments, the theoretical model for nozzle outlet type, nozzle outlet velocity, nozzle outlet diameter, jet angle, and target distance parameters based on the analysis of factors affecting nozzle impact coal breaking performance includes:

[0043] Nozzle outlet type parameter model:

[0044] Through research and analysis, the most popular nozzle outlet types on the market were identified. The structural characteristics of each type of nozzle outlet were analyzed, and the nozzle length l was obtained. pj and nozzle inlet diameter D ent ;

[0045] Nozzle exit velocity parameter model:

[0046] Since the water pressure Pent inside the nozzle is much greater than the water pressure Pout outside the nozzle, the water jet pressure and velocity inside and outside the nozzle satisfy the following relationship:

[0047]

[0048] Where: Pent and Pout are the water jet pressures inside and outside the nozzle, respectively; ρ s Vt is the water jet density, which is a constant; Vt and Vout are the water jet velocities at the nozzle inlet and outlet, respectively, in m / s.

[0049] Assuming the water jet is continuous, the static pressure at the nozzle inlet and outlet and the water jet velocity have the following relationship:

[0050]

[0051] By combining equations (1) and (2), we can obtain:

[0052]

[0053] Because Pent >> Pout Simplifying equation (3), the nozzle exit velocity Vout parameter model is as follows:

[0054]

[0055] Nozzle outlet diameter parameter model:

[0056] After undergoing acceleration within the nozzle, the water jet impacts and damages the coal mass from the nozzle outlet. Assuming the axial velocity of the nozzle makes a 90° angle with the coal surface, and the water jet acts directly on the coal surface from the nozzle outlet, neglecting energy loss in the air, the impact force Fc can be calculated using the following formula:

[0057]

[0058] In the formula: ρ s is the water jet density, which is a constant; Dout is the nozzle outlet diameter, in mm; Vout is the nozzle outlet velocity, in m / s.

[0059] The physical and mechanical properties of the coal body itself determine whether a water jet can cause impact damage. Therefore, when a water jet acts on the coal surface from the nozzle outlet, the impact force of the water jet is greater than or equal to the coal body's own destructive load F. p The water jet impact will cause overall damage to the coal body. Considering that the pressure relief from the water jet impact only requires internal fractures within the coal body, a calculation coefficient k for the coal body damage load is set. This coefficient can be taken as 0.1 to 1.0, depending on the physical and mechanical properties of the coal body, the roadway strata, and the loss of the water jet impact load in the air. Therefore, the nozzle outlet diameter D... out The parametric model is:

[0060]

[0061] Jet angle parameter model:

[0062] The jet angle refers to the angle between the nozzle exit velocity Vout and the coal surface. Different jet angles determine the magnitude of the water jet impact force perpendicular to the coal surface. Assuming the distance between the nozzle outlet and the coal surface is 0, the water jet impact force at this time... for:

[0063]

[0064] Similarly, it is assumed that the impact force of the water jet is greater than or equal to the failure load F of the coal body itself. p It can damage the coal body, therefore the jet angle parameter model is:

[0065]

[0066] Target distance parameter model:

[0067] Target distance refers to the distance from the nozzle outlet to the coal body in the direction of the water jet, during which the water jet impact force F ck Subjected to air resistance F kThe influence of this weakens the coal-breaking ability of the water jet to some extent, assuming the nozzle jet angle is... The impact force of the water jet within the target distance l can be calculated by the following formula:

[0068]

[0069] Where: η is the air resistance coefficient, which is a constant; S is the cross-sectional area of ​​the nozzle converging section, in mm. 2 ; l is the target distance, mm; V xd =(V1+V2) / [1+(V1V2 / c 2 )], where is the relative velocity between the water jet and the air, in m / s.

[0070] Similarly, the impact force of the water jet is greater than or equal to the failure load F of the coal body itself. ph The water jet impact will cause overall damage to the coal body. Considering that the pressure relief from the water jet impact only requires internal fissures within the coal body, a calculation coefficient κ for the coal body damage load is set. This coefficient κ can be taken from 0.1 to 1.0, depending on the physical and mechanical properties of the coal body, the roadway strata, and the attenuation of the water jet impact load in the air. Therefore, the target distance parameter model is as follows:

[0071]

[0072] In some embodiments, substituting the physical and mechanical parameters of the coal body and water jet into the theoretical model of the nozzle parameters to calculate the theoretical value range of different nozzle parameters includes:

[0073] Substituting the physical and mechanical parameters of the coal body and water jet collected in step one into the nozzle parameter theoretical model, the nozzle exit velocity Vout, nozzle exit diameter Dout, and jet angle are calculated. And the theoretical range of the target distance l.

[0074] In some embodiments, the theoretical values ​​of different nozzle parameters are substituted into the SPH particle-filled two-dimensional mesh model for numerical simulation. The coal breaking effect under different parameters is evaluated by establishing a nozzle impact coal breaking performance index. The structural parameters of the optimal high-pressure water jet coal breaking and pressure relief nozzle are obtained as follows:

[0075] ① The axial and radial ratios of crack propagation, w1 and w2:

[0076]

[0077] Where: l z l j The depth of coal cracks in the axial and radial directions of the nozzle, in mm; l mz l mj The length of the coal body model along the axial and radial directions of the nozzle is in mm.

[0078] ② The ratio of the crack propagation and fracture zone area to w3:

[0079]

[0080] Wherein: S p S m The area of ​​the crack propagation fracture zone and the area of ​​the coal body model are shown in mm. 2 a1 and a2 are the lengths of the coal crack propagation and breakage zones in the axial and radial directions of the nozzle, respectively, in mm.

[0081] ③ The ratio of the number of cracks within the optimal crack propagation angle, w4:

[0082] The impact of the water jet inside the coal seam generates numerous cracks, and the angle between the crack and the coal surface is the crack propagation angle. As the angle increases, the effect of crack propagation inside the coal body first increases and then decreases. The optimal crack propagation angle range is defined as the range where the crack depth is greatest and the crack breaking effect is best. The ratio of the number of cracks within this angle range to the total number of cracks is defined as the crack number ratio w4 within the optimal crack propagation angle.

[0083]

[0084] Where: m1 is The number of cracks in the interval; m2 is the total number of cracks.

[0085] ④ Coal breaking energy consumption w5:

[0086] The energy consumed by water jet impact in breaking coal is E w The energy E consumed w The specific energy consumption for coal breaking is defined as w5, which is the area of ​​the crack propagation and fracture zone w3.

[0087]

[0088] Wherein: S out The nozzle outlet cross-sectional area is in mm. 2 .

[0089] ⑤ By determining the influence weight of each indicator, a method for evaluating the performance of nozzle impact coal breaking is constructed:

[0090]

[0091] Where wt is the evaluation index of the coal breaking effect of a certain nozzle, wi is the coal breaking performance index of different nozzles, and wimax is the maximum value of the coal breaking performance index of different nozzles.

[0092] Table 1 shows the performance indicators of nozzle impact coal breaking under different parameter conditions:

[0093] Table 1

[0094]

[0095]

[0096] Based on the values ​​of each evaluation indicator, take the corresponding (0, 1, 2, 3) indicator values, and finally comprehensively evaluate the merits of the parameters.

[0097] When w t When w is ≤0.25, the impact crushing performance of this nozzle structure is poor, with low crack propagation and high stress concentration within the coal body; when w is <0.25, the performance is poor. t When ≤0.5, the impact crushing performance of this nozzle structure is generally good, with low crack propagation and high stress concentration within the coal body; when 0.5 < w t When w is ≤0.75, the impact coal breaking performance of this nozzle structure is relatively good, the crack propagation degree is good, and the stress concentration degree inside the coal body is low; when w is >0.75, the impact coal breaking performance is relatively good. t At that time, the impact coal breaking performance level of the nozzle structure parameters was good, the crack propagation degree was good, and the stress concentration degree inside the coal body was low.

[0098] This embodiment takes the haulage roadway of the 6302 working face in a certain mine as an example. The working face is located in the west-central part of the 630 mining area. The main coal seam is No. 3 coal, with a burial depth of 981.2-1101.2m, which is a coal seam with a strong tendency to impact. The 6302 working face haulage roadway is located west of the 6301 goaf. The coal pillar width between the roadway and the goaf is 6m. Due to the high ground stress under the deep mining conditions and the lateral support pressure of the goaf, the 6302 working face haulage roadway is located in a high stress concentration area. The working face layout is as follows: Figure 2 As shown. The following section, combining the structural parameter optimization method of the high-pressure water jet coal breaking and pressure relief nozzle in this invention, optimizes the nozzle structural parameters in the high-pressure water jet pressure relief measures of the 6302 working face transport roadway. The specific implementation steps are as follows:

[0099] The geometric dimensions of the coal body model constructed based on the characteristics of the No. 3 coal seam in the 6302 working face are set to length l. mz =75mm and width l mj =50mm. The geometry of the nozzle model is set to length l. pj=25mm, the nozzle inlet diameter (Dent parameter) is determined according to the outlet type. Both the coal body and water jet are filled with SPH particles, and the corresponding SPH particle density is set according to their physical densities. Physical and mechanical parameters of the coal body and water jet are set, and boundary conditions are imposed on the bottom and two sides of the coal body model. The constructed mesh model is as follows: Figure 3 As shown.

[0100] After a high-pressure water jet impacts the coal body, numerous cracks combine to form a large fracture zone, creating a significant stress relief zone within the coal body and greatly reducing stress concentration. The crack propagation is related to the coal's inherent physical and mechanical properties. This method assigns physical parameters to the coal body based on mine exploration results; the coal's mechanical parameters are shown in Table 2. The water jet density is taken as ρ. s 1000 kg.m -3 .

[0101] Table 2

[0102]

[0103] After constructing the nozzle and coal body mesh model, the method of controlling numerical simulation variables is used to conduct numerical simulations on the nozzle outlet type, nozzle outlet velocity, nozzle outlet diameter, jet angle and target distance parameters, and optimize and determine the optimal nozzle structure parameters.

[0104] First, through research and analysis, six popular nozzle outlet types were identified. The structural characteristics of each type of nozzle outlet were analyzed to obtain the nozzle inlet diameter (Dent). To explore the optimal nozzle outlet type and analyze the crack propagation within the coal body under different nozzle outlet types, a jet outlet diameter of 2.5 mm, a jet outlet velocity of 447.2 m / s (jet inlet pressure of 100 MPa), a jet angle of 90°, and a target distance of 20.0 mm were selected. Numerical simulations of impact coal breaking were conducted for six nozzle outlet types: straight, conical, straight tapering, straight expanding, inner cone with outer straight, and inner wide with outer narrow. The crack propagation after impact coal breaking under different nozzle outlet types is shown below. Figure 4 As shown in Table 3, the crack propagation under different nozzle exit type parameters was evaluated, and the evaluation results are as follows:

[0105] Table 3

[0106]

[0107] After determining that the nozzle outlet type is a straight tapering type, in order to explore the optimal nozzle outlet velocity and analyze the crack propagation inside the coal body when the velocity changes, a nozzle with a straight tapering outlet type, a jet diameter of 2.5 mm, a jet angle of 90°, and a target distance of 4.0 mm was selected. Through research and analysis, it was found that the maximum inlet pressure Pent of the commercially available mine impact coal breaking and pressure relief nozzles is 120 MPa. According to equation (4), the nozzle outlet velocity Vout at different nozzle inlet pressures Pent can be determined. Here, the nozzle outlet velocities Vout at nozzle inlet pressures of 20 MPa, 40 MPa, 60 MPa, 80 MPa, 100 MPa, and 120 MPa are used to carry out numerical simulation of impact coal breaking, as shown in Table 4. The crack propagation after impact coal breaking at different nozzle outlet velocities is as follows. Figure 5 As shown in Table 5, the crack propagation under different nozzle exit velocity parameters was evaluated, and the evaluation results are as follows:

[0108] Table 4

[0109]

[0110]

[0111] Table 5

[0112]

[0113] After determining the direct nozzle outlet type and nozzle outlet velocity, in order to explore the optimal nozzle outlet diameter and analyze the crack propagation inside the coal body under different nozzle outlet diameters, a straight tapering nozzle was selected, with an outlet velocity of 489.9 m / s, a jet angle of 90°, and a target distance of 4.0 mm. According to equation (6), the minimum nozzle outlet diameter for the water jet to cause impact damage to the coal body is determined to be 2.8 mm (calculation coefficient κ is 0.1). Here, numerical simulations of impact coal breaking are carried out with nozzle outlet diameters of 2.8 mm, 3.0 mm, 3.2 mm, 3.4 mm, 3.6 mm, and 3.8 mm, respectively. The crack propagation after impact coal breaking with different nozzle outlet diameters is as follows: Figure 6 As shown in Table 6, the crack propagation under different nozzle outlet diameter parameters was evaluated, and the evaluation results are as follows:

[0114] Table 6

[0115]

[0116] After determining the direct nozzle outlet type, nozzle outlet velocity, and nozzle outlet diameter, in order to explore the optimal jet angle and analyze the crack propagation inside the coal body under different jet angles, a straight tapering nozzle was selected, with an outlet velocity of 489.9 m / s, an outlet diameter of 3.6 mm, and a target distance of 4.0 mm. According to equation (8), the minimum jet angle for the water jet to cause impact damage to the coal body is determined to be 9.9° (calculation coefficient κ is 0.10). Here, numerical simulations of impact coal breaking are carried out at jet angles of 10°, 30°, 50°, 70°, and 90° respectively. The crack propagation after impact coal breaking at different jet angles is as follows: Figure 7 As shown in Table 7, the crack propagation under different jet angle parameters was evaluated, and the evaluation results are as follows:

[0117] Table 7

[0118]

[0119] After determining the nozzle outlet type, nozzle outlet velocity, nozzle outlet diameter, and jet angle, in order to explore the optimal target distance and analyze the crack propagation inside the coal body under different target distances, a straight tapering nozzle was selected, with an outlet velocity of 489.9 m / s, an outlet diameter of 3.6 mm, and a jet angle of 90°. According to equation (10), the minimum target distance for the water jet to cause impact damage to the coal body is determined to be 0.87 m (considering the influence of air resistance, the calculation coefficient κ is 1.0). According to the engineering practice of high-pressure water jet cutting and pressure relief, the impact force is the largest when the target distance is equal to 100 times the nozzle outlet diameter Dout. Here, the numerical simulation of impact coal breaking is carried out when the target distance is 20.0 mm, 40.0 mm, 60.0 mm, 80.0 mm, 100.0 mm, and 120.0 mm respectively. The crack propagation after impact coal breaking with different nozzle outlet diameters is as follows. Figure 8 As shown in Table 8, the crack propagation under different target distance parameters was evaluated, and the evaluation results are shown in Table 8:

[0120] Table 8

[0121]

[0122] Based on the above results, the optimal parameters for the high-pressure water jet coal breaking and pressure relief nozzles in the coal seam of the 6302 working face transport roadway are shown in Table 9:

[0123] Table 9

[0124] Nozzle outlet type Nozzle exit velocity m / s Nozzle outlet diameter (mm) Jet angle / ° Target distance / mm flat tapering type 489.9 3.6 90.0 40

[0125] This invention discloses a method for optimizing the structural parameters of a high-pressure water jet coal crushing and pressure relief nozzle, comprising the following steps: collecting structural characteristics of the coal body and nozzle, and constructing an SPH particle-filled mesh model; based on the analysis of factors affecting the nozzle's impact coal crushing performance, constructing theoretical models for nozzle outlet type, nozzle outlet velocity, nozzle outlet diameter, jet angle, and target distance parameters; substituting the physical and mechanical parameters of the coal body and water jet into the nozzle parameter theoretical model to calculate the theoretical value range of different nozzle parameters; substituting the theoretical values ​​of different nozzle parameters into the SPH particle-filled two-dimensional mesh model for numerical simulation, and evaluating the coal crushing effect under different parameters by establishing a nozzle impact coal crushing performance index, thereby obtaining the optimal structural parameters of the high-pressure water jet coal crushing and pressure relief nozzle. The structural parameter optimization method of the high-pressure water jet coal crushing and pressure relief nozzle involved in this invention is more in line with the actual field conditions, and the obtained optimal nozzle structural parameters are more accurate, capable of generating more cracks inside the coal body, which plays an important role in maximizing the pressure relief effect and reducing the pressure relief cost.

[0126] The above description is merely a preferred embodiment of this application, but the scope of protection of this application 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 this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for optimizing the structural parameters of a high-pressure water jet coal crushing and pressure relief nozzle, characterized in that, Includes the following steps: Obtain the physical and mechanical parameters of the coal body and water jet, and construct an SPH particle-filled two-dimensional mesh model based on the physical and mechanical parameters of the coal body and water jet; The SPH particle-filled two-dimensional mesh model includes a nozzle SPH particle-filled two-dimensional mesh model and a coal body SPH particle-filled two-dimensional mesh model. The construction process includes: both the coal body and the nozzle are filled with SPH particles, and the SPH particle density is set based on the physical density of the water jet in the coal body and the nozzle. The physical and mechanical parameters of the coal body and the nozzle are set, and the boundary conditions are restricted on the bottom surface and two sides of the coal body. Construct a theoretical model of nozzle parameters; Nozzle exit velocity The parametric model is: ;in, The pressure of the water jet inside the nozzle. It is the water jet density; Nozzle outlet diameter The parametric model is: ;in, For nozzle exit velocity, This represents the critical failure load of the coal seam. The coefficients for calculating the coal body failure load; The jet angle parameter model is as follows: ;in, The jet angle; The target distance parameter model is as follows: ;in, Target distance, The air drag coefficient, The cross-sectional area of ​​the nozzle's contraction section. The relative velocity between the water jet and the air; Substituting the physical and mechanical parameters of the coal body and water jet into the theoretical model of nozzle parameters, the theoretical value range of different nozzle parameters is calculated. Construct an index for the performance of nozzle impact coal breaking; The indicators of the nozzle's impact coal breaking performance include: the ratio of axial crack propagation to radial crack propagation, the ratio of crack propagation area to the broken zone, the ratio of the number of cracks within the optimal crack propagation angle, and the specific energy consumption for coal breaking. The crack propagation axial ratio and crack propagation radial ratio are obtained based on the crack depth and coal model length. The crack propagation fracture zone area ratio is obtained based on the crack propagation fracture zone area and coal model area. The crack number ratio within the optimal crack propagation angle is obtained based on the number of cracks within the optimal crack propagation angle range and the total number of cracks. The coal breaking energy consumption is obtained based on the energy consumed by water jet impact coal breaking and the crack propagation fracture zone area. Numerical simulations were performed using theoretical values ​​of different nozzle parameters and an SPH particle-filled two-dimensional mesh model. The simulation results under different parameters were evaluated based on the nozzle's coal crushing performance index, and the optimal structural parameters of the high-pressure water jet coal crushing and pressure relief nozzle were obtained. The simulation results under different parameters are evaluated based on the influence weight of each indicator in the nozzle impact coal breaking performance index.

2. The method for optimizing the structural parameters of the high-pressure water jet coal-breaking and pressure-relieving nozzle according to claim 1, characterized in that, The construction of the SPH particle-filled two-dimensional mesh model is also based on mesh model data, which is obtained based on the structural features of the coal body and nozzle, and the geometric dimensions of the SPH particle-filled two-dimensional mesh model are obtained based on the mesh model data.

3. The method for optimizing the structural parameters of the high-pressure water jet coal-breaking and pressure-relieving nozzle according to claim 1, characterized in that, The physical and mechanical parameters of the coal body and water jet include: coal density, coal compressive strength, tensile strength and critical failure load, bulk modulus, shear modulus and Poisson's ratio, and water jet density.

4. The method for optimizing the structural parameters of the high-pressure water jet coal-breaking and pressure-relieving nozzle according to claim 1, characterized in that, The theoretical model of nozzle parameters includes nozzle exit type, nozzle exit velocity, nozzle exit diameter, jet angle, and target distance.

5. The method for optimizing the structural parameters of the high-pressure water jet coal-breaking and pressure-relieving nozzle according to claim 4, characterized in that, The theoretical model of nozzle parameters is constructed based on the analysis of factors affecting the nozzle's impact coal breaking performance.

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