CN103018005A - Method for reducing erosive abrasion of solid particles on wall surface - Google Patents

Abstract

The invention discloses a method for reducing erosive abrasion of solid particles on a wall surface. By performing calculating on a large number of values and experimental verifying on a near-wall flow field with solid particles and ditching longitudinal grooves on the wall surface, the method can reduce the erosive abrasion of the solid particles on the wall surface and provides a ditching mode obvious in abrasion reduction effect, the required diameters of the particles for reducing abrasion rate and the range of incidence angles are defined, and the method is effective in reducing wall surface abrasion of gas-solid flowing systems in the engineering field of steel, machinery and pertrifaction.

Description

A method for alleviating the erosion and wear of solid particles on the wall surface

technical field

The invention belongs to the field of wall wear, in particular to a method for reducing the erosion and wear of solid particles on the wall.

Background technique

There are a large number of gas-solid two-phase flow systems in the fields of iron and steel, machinery and petrochemical engineering, such as two-phase impeller machinery, pneumatic conveying and dust removal devices, etc. Since the velocity of solid particles in the airflow is very high and often deviates from the streamline, it will cause impact and wear on the wall surface, affecting normal production and bringing hidden dangers of accidents. Therefore, it is necessary to study the wall wear behavior of this type of flow system. There are usually two ways to reduce wall wear. One is to improve the wear resistance of wall materials, such as using wear-resistant materials, coating wear-resistant materials on the wall, or modifying the wall. However, this method is often used lead to higher costs. The second is based on the gas-solid two-phase flow theory, by changing the shape of the wall to change the conditions of the flow field near the wall, thereby affecting the velocity and trajectory of the solid particles, and finally reducing the wear of the solid particles on the wall. Research in recent years has adopted the method of welding ribs on the wall along the vertical direction of the fluid. Although this method can reduce wear, it brings additional losses in the flow field; Wear, although this method has a better effect of reducing wear, it is more difficult to implement.

Aiming at the deficiencies of the prior art, the present invention comprehensively considers various factors such as cost, flow field loss, and feasibility, and proposes an economical and effective method for alleviating the erosion and wear of solid particles on the wall surface, and gives the most obvious wear-reducing effect The grooving method defines the range of particle size and angle of incidence required to obtain a lower wear rate.

Contents of the invention

The purpose of the present invention is to provide a method for alleviating the erosion and wear of solid particles on the wall surface in view of the deficiencies in the prior art.

The object of the present invention is achieved by the following technical solutions: a method for alleviating solid particles to wall erosion wear, the method comprising:

(1) Dig longitudinal grooves on the wall, and the width of the grooves is equal to the distance between the grooves;

(2) Solid particles processed to small particles with a diameter of less than 50 μm;

(3) Adjust the incident angle of solid particles to 10°~30° or 70°~90°.

The beneficial effect of the present invention is: the present invention cuts longitudinal grooves on the wall surface to reduce the abrasion of the solid particles on the wall surface, so that a large amount of gas-solid two-phase energy in the engineering fields such as iron and steel, machinery and petrochemicals can be solved in a relatively low-cost manner. The equipment of the phase flow system provides effective protection, reduces the maintenance and renewal of equipment, and at the same time reduces the hidden danger of accidents caused by wear and tear of large-scale equipment in long-term operation, improves the stability and safety of production, and thus brings certain economic benefits .

Description of drawings

Fig. 1 is a schematic diagram of the test device;

In the figure, a gas storage tank 1, a pipeline 2, a valve 3, a pressure gauge 4, a flow meter 5, a fly ash tank 6, a test piece 7, a separator 8, a collection box 9, and a ventilator 10.

Detailed ways

The method for alleviating the erosive wear of the solid particles on the wall surface of the present invention is: digging a number of longitudinal grooves on the wall surface to reduce the wear of the solid particles on the wall surface. Wear reduction is most effective when the groove width is equal to the groove pitch. In the case of a defined wall and particle material, the wear rate depends on the size of the particles and the direction of particle motion at the inlet. When the wall surface material is A3 steel, the wall surface length, width and thickness are 450mm×120mm×15mm, and the wall surface groove width, height and groove spacing are 6mm×5mm×6mm, for fly ash particles with a density of 1500kg/ ^m3 , when When the particle diameter is 0~50μm and the incident angle is 10°~30° or 70°~90°, the wear rate per unit mass of particles can be less than 9mm ³ . The wear rate is defined as the wall wear volume loss per unit mass of particles colliding with the wall, and the unit is mm ³ . The incident angle is defined as the angle between the particle movement direction at the inlet and the horizontal direction, and the unit is degree.

Because the velocity of solid particles in the airflow is very high and often deviates from the streamline, it is extremely difficult to measure the collision wear between solid particles and the wall in the turbulent flow field. Therefore, the derivation basis of the method proposed in the present invention is based on two methods of numerical simulation and experimental verification.

The models in the numerical simulation method include near-wall flow field models and particle models. Particles move under the action of various forces in the near-wall flow field. The Lagrangian method is used to calculate the force acting on the solid particles, and then the movement information of the solid particles is obtained, and then the flow field is corrected based on the solid particle effect. Due to the local low Reynolds number region in the involved flow field, it is difficult to directly apply the standard k-ε mode, so the k-ε mode modified for the low Reynolds number situation needs to be used. First, the turbulent kinetic energy and dissipation rate are solved under the boundary conditions to obtain the velocity of the airflow field, the calculation area is divided into sub-areas, and a series of algebraic equations are obtained after the equations are integrated on the sub-areas, and then iteratively solved. Second, the particle velocity and trajectory are calculated. Third, consider the flow field velocity correction under the reaction of particles to the flow field. Fourth, when the particle hits the wall, calculate the rebound velocity and angle of the particle, and at the same time calculate the amount of wear on the wall. Finally, after the particle hits the wall, according to the rebound speed and angle of the particle, the calculation continues from the third part. During the calculation, the number of particles in each example is 80,000, and the particles are distributed equidistantly along the y and z directions at the entrance with a spacing of 1mm. The speed of the particles at the initial moment is the same as that of the airflow, and the initial movement direction of the particles is randomly selected. After a large number of calculations, the wear of the particles on the wall after excavating the longitudinal grooves, the relationship between the wear rate and the height and spacing of the grooves, and the effect of the particles on the wall wear were finally obtained.

The experimental verification method is shown in Figure 1. The high-pressure air flows out of the gas storage tank 1, and after the pipeline 2 passes through the valve 3, the pressure gauge 4, and the flow meter 5, it drives the fly ash in the fly ash tank 6 to flow through the test piece 7 , and then the fly ash is separated by the separator 8, the fly ash in the collection box 9 can be recycled, and the ventilator 10 at the end of the pipeline is used to generate negative pressure. The solid particles are fly ash particles with a density of 1500kg/m ³ and an average particle diameter of 57μm. The wall material is A3 steel, and the included angle with the airflow can be adjusted. The length, width and thickness are 450mm×120mm×15mm respectively. And three test pieces of 8mm×5mm×6mm. The gas storage tank is filled with high-pressure gas to make the pressure reach 0.392MPa, the Reynolds number Re≈105, and the flow field is turbulent. First open the ventilator 10 to generate enough negative pressure to ensure that the fly ash can flow through the separator 8 smoothly and enter the collection box; then open the gas storage tank valve 3, adjust the pressure of the pressure gauge 4 to 0.294MPa, and the flow meter 5 The flow is about 28m ³ /h. Then open the 6 valves of the fly ash tank to make the fly ash enter the pipeline system, and adjust the valve to make the fly ash reach the required concentration. During the test, the gas flow rate is kept constant by continuously adjusting the flow rate, and the mass loss of the test piece before and after the test is measured with a precision balance, and this is used as the amount of wear.

The main steps are as follows:

The first step is to determine that the solid particles are fly ash particles with a density of 1500kg/m ³ and an average particle diameter of 57μm; the wall material is A3 steel, and the included angle with the airflow can be adjusted. The length, width and thickness are 450mm×120mm× 15mm, using three test pieces without grooves and grooves with width, height and groove spacing of 6mm×5mm×6mm and 8mm×5mm×6mm respectively; Reynolds number Re≈105, and the flow field is turbulent. For the numerical simulation method, the number of particles in each test is 80,000, and the particles are distributed equidistantly along the y and z directions at the entrance with a spacing of 1mm. The particles and the airflow velocity at the initial moment are the same, and the initial movement direction of the particles is randomly selected. Under these working conditions, the wear rate per unit mass of particles on the wall surface after excavating longitudinal grooves is significantly lower than that on the wall surface without longitudinal grooves, and the width, height and groove spacing of the grooves are 6mm×5mm×6mm respectively The wear rate is lower than that of 8mm×5mm×6mm. For the experimental method, the gas storage tank is filled with high-pressure gas to make the pressure reach 0.392MPa, the pressure of the gas storage tank valves is adjusted to 0.294MPa, and the flow rate of the flowmeter is 28m ³ /h. Measured with a precision balance, the wear volumes of the two grooved specimens corresponding to the particles per unit mass are 6.6mm ³ and 7.8mm ³ respectively, while the wear volumes of the ungrooved specimens corresponding to the grains per unit mass are 10.6mm ³ , indicating that digging longitudinal grooves on the wall can reduce the wear of solid particles on the wall, and the wear rate is lower when the groove width is equal to the groove spacing.

The second step is shown in Table 1. The ratio of the groove width to the spacing is 3:1, 2:1, 1.5:1, 1:1, 1:1.5, 1:2, 1:3 when the debriefing calculation is carried out, and it is found that when The wear rate is the smallest when the ratio of the groove width to the groove spacing is 1:1, and the wear rate increases when the groove width is larger or smaller than the groove spacing, so when the groove width is equal to the groove spacing, the wear reduction effect most.

Table 1: Wear rates at different groove width-to-pitch ratios

Groove width, pitch ratio 3:1 2:1 1.5:1 1:1 1:1.5 1:2 1:3 Wear rate (W, mm ³ ) 7.8 7.2 6.5 5.3 6.2 6.8 7.4

The third step is shown in Table 2. Numerical simulations are carried out for the particle sizes of 20, 30, 40, 50, 60, 70, and 80 μm to obtain the wear rate values. It is found that within a certain range, large particles increase the wall wear rate. , and when the particle size exceeds a certain critical value, the size has little effect on the wear rate. When the particle diameter is less than 50μm, the wear rate is lower than 9mm ³ , which meets the wear rate requirements of most engineering fields such as steel, machinery and petrochemical.

Table 2: Wear rate at different particle diameters

Particle diameter (d _p , μm) 20 30 40 50 60 70 80 Wear rate (W, mm ³ ) 4 6.2 7.7 8.7 9.5 9.8 10

The fourth step is shown in Table 3. When the incident angle of the particles is 10° to 90°, the wear rate is obtained by numerical calculation. It is found that the movement direction of the particles at the inlet has a direct impact on the wall wear rate. When the incident angle is 50° The wear rate is the largest. When the incident angle is 10°~30° or 70°~90°, the wear rate per unit mass of particles can be less than 9mm ³ , which meets the wear rate requirements of most engineering fields such as steel, machinery and petrochemical.

Table 3: Wear rates at different particle incidence angles

Particle incident angle (α, °) 10 20 30 40 50 60 70 80 90 Wear rate (W, mm ³ ) 5.2 7.8 9.0 10.8 11.8 11.2 8.2 4.6 0.4

The above-mentioned embodiments are used to illustrate the present invention, rather than to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention.

Claims (1)

1. one kind alleviates solid grain to the method for wall erosive wear, it is characterized in that the method comprises:

(1) dig longitudinal groove at wall, and groove width equates with groove pitch;

(2) solid particle is machined to diameter less than 50

Granule;

(3) adjusting the solid particle incident angle is about

Or

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