Method for testing and evaluating cutting resistance reduction effect of rake teeth under high-pressure flushing condition

Abstract

The invention relates to a method for testing and evaluating the cutting resistance reduction effect of rake teeth under a high-pressure flushing condition. The method comprises the following steps: 1, preparing experimental soil and preparing an experimental device; 2, testing the cutting resistance reduction effect of the rake teeth under the high-pressure flushing condition; 3, analyzing the resistance reduction effect of high-pressure flushing: setting the cutting resistance of single rake tooth cutting to be F1 under the condition of no high-pressure flushing and the cutting resistance of single rake tooth cutting to be F2 under the condition of high-pressure flushing; f2 / F1 is smaller than or equal to 70%, and the high-pressure flushing drag reduction effect is obvious; 70% lt; f2 / F1 is smaller than or equal to 90%, and the high-pressure flushing drag reduction effect is obvious; f2 / F1gt; and the high-pressure flushing drag reduction effect is not obvious. Before and after the high-pressure flushing system is started, the consumption power difference value of the rake teeth cutting the soil body is W1, the consumption power of the high-pressure flushing system is W2, F2 / F1 is smaller than or equal to 90%, and W1gt is obtained; w2, a high-pressure flushing system is started; if W1 is smaller than or equal to W2, closing the high-pressure flushing system. The method provides a basis for evaluating the drag reduction effect and the opening condition of the high-pressure flushing system.

Description

Technical Field

[0001] This invention belongs to the field of dredging engineering technology, and in particular relates to a method for testing and evaluating the drag reduction effect of rake teeth under high-pressure flushing conditions. Background Technology

[0002] Dredging projects often encounter hard, difficult-to-excavate soils with low productivity. For example, in coastal port construction in my country, the soil at depths of -20 to -25 meters is generally difficult to excavate, consisting of clay. This clay has low water content, high cohesion, and is hard, requiring significant cutting force for excavation. Furthermore, in outer channels, dense silt layers formed due to a combination of factors such as siltation and dredging are continuously distributed within the channel, are thick, have low water content, high SPT blow counts, and are hard and difficult to excavate. Both hard clay and dense silt are among the most difficult soil types to excavate during dredging.

[0003] Currently, to improve the productivity of trailing suction hopper dredgers when excavating hard soil, high-pressure water jetting devices are installed on the dredger heads. However, there is no effective research method for studying the drag reduction effect of these devices under different excavation conditions (excavation angle, excavation depth, and excavation speed) and when excavating hard soil of different types. Furthermore, there is no method or basis for determining the activation conditions of the high-pressure water jetting system. Therefore, it is necessary to seek a testing and evaluation method for the drag reduction effect of the dredger teeth under high-pressure water jetting conditions. This method would be used in the design of the dredger head and the formulation of construction processes to test the drag reduction effect of the high-pressure water jetting system and to provide the activation conditions for the high-pressure water jetting system. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for testing and evaluating the drag reduction effect of rake teeth cutting under high-pressure water flushing conditions. This method involves conducting underwater cutting experiments with a single rake tooth to measure its cutting resistance; then conducting underwater cutting experiments under different high-pressure water flushing conditions to measure the cutting resistance under high-pressure water flushing conditions; and providing formulas for calculating the difference in power consumption of the rake teeth cutting soil before and after the high-pressure water flushing system is activated, as well as formulas for calculating the power consumption of the high-pressure water flushing system itself. By comparing the two sets of power calculations, the drag reduction effect of the rake teeth cutting soil under high-pressure water flushing conditions is evaluated, and the activation conditions of the high-pressure water flushing system are determined. This invention can evaluate the drag reduction effect of the high-pressure water flushing system when the rake teeth cut soil and determine the activation conditions of the high-pressure water flushing system, providing an effective testing and calculation method for the design and construction process of high-pressure water flushing systems.

[0005] This invention is implemented as follows: a method for testing and evaluating the drag reduction effect of rake teeth under high-pressure water flushing conditions, and the specific testing process is as follows:

[0006] Step 1: Preparation of experimental soil and setup of experimental apparatus

[0007] Prepare experimental soil with a certain particle ratio, water content, density, and standard penetration number that meet the requirements;

[0008] The experimental device includes a running trolley, a cutting harrow tooth device, a high-pressure flushing system, and a soil box;

[0009] Step 2: Test the drag reduction effect of harrow tooth cutting under high-pressure flushing conditions

[0010] Prepare for the test. After that, close the high-pressure flushing system, start the running trolley, and conduct underwater cutting experiments without high-pressure flushing; open the high-pressure flushing system and adjust the high-pressure flushing flow rate, and conduct underwater cutting experiments under high-pressure flushing conditions; obtain the cutting resistance of the harrow teeth during the corresponding cutting process through a cutting force sensor;

[0011] Step 3: Analyze the drag reduction effect of high-pressure flushing

[0012] Set the cutting resistance of single harrow tooth cutting without high-pressure flushing as F1, and the cutting resistance of single harrow tooth cutting under high-pressure flushing as F2;

[0013] Calculate the value of F2 / F1. When F2 / F1 ≤ 70%, the drag reduction effect of high-pressure flushing is obvious; when 70% < F2 / F1 ≤ 90%, the drag reduction effect of high-pressure flushing is relatively obvious; when F2 / F1 > 90%, the drag reduction effect of high-pressure flushing is not obvious.

[0014] In the above technical solution, preferably, the analysis of the drag reduction effect of high-pressure flushing in step 3 also includes judging the opening and closing conditions of the high-pressure flushing system;

[0015] Calculation formula for the power difference consumed by the harrow teeth cutting the soil before and after the high-pressure flushing system is opened:

[0016] W1 = (F1 - F2)·V·n

[0017] In the formula, W1 is the power difference consumed by the harrow teeth cutting the soil before and after the high-pressure flushing system is opened, with the unit of W; F1 - F2 is the cutting resistance reduced by high-pressure flushing, with the unit of N; V is the cutting speed of the harrow teeth, with the unit of m / s; n is the number of harrow teeth;

[0018] Calculation formula for the power consumed by the high-pressure flushing system:

[0019]

[0020] In the formula, W2 is the power consumed by the high-pressure flushing system, with the unit of W; P is the nozzle pressure of the high-pressure flushing system, with the unit of Pa; A is the area of the nozzle, with the unit of m 2 ; V is the water flow velocity at the nozzle, with the unit of m / s; ρ is the density of water, with the unit of kg / m 3 ; Q is the nozzle flow rate, with the unit of m 3 / s; m is the number of nozzles;

[0021] When F2 / F1≤90%, calculate and compare the values ​​of W1 and W2. When W1>W2, turn on the high-pressure flushing system; when W1≤W2, turn off the high-pressure flushing system.

[0022] In the above technical solution, preferably, the running trolley can achieve variable speed movement in the x, y, and z directions; the cutting rake tooth device is fixed on the running trolley and is used to conduct cutting experiments with different cutting angles, cutting depths, and cutting speeds; a cutting force sensor is installed on the cutting rake tooth device to measure the cutting force of the rake tooth; the high-pressure water flushing system is fixed on the running trolley, and the nozzle of the high-pressure water flushing system is installed in front of the rake tooth. During the process of the rake tooth cutting the soil, the nozzle sprays high-speed water to flush and pre-crush the soil, thereby reducing the cutting force of the rake tooth cutting the soil; the soil box is used to hold the experimental soil.

[0023] In the above technical solution, preferably, the preparation before testing is as follows: first, place and fix the soil box filled with experimental soil on the test bench; fix the cutting rake tooth device with cutting force sensor and high-pressure water flushing system on the running trolley; raise and lower the running trolley, adjust the position of the running trolley in the horizontal x direction and vertical y direction, set the cutting soil layer thickness, set the traveling speed of the running trolley and set it to the z direction; inject water into the test bench, and submerge the soil box.

[0024] Compared with the prior art, the advantages and positive effects of this invention are:

[0025] The present invention provides a method for testing and evaluating the drag reduction effect of rake teeth under high-pressure water flushing conditions. This method compares the cutting resistance of a single rake tooth under both high-pressure and low-pressure water flushing conditions to analyze the drag reduction effect of high-pressure water flushing when the rake head and teeth cut the soil. Simultaneously, by comparing the power consumption reduction achieved under high-pressure water flushing conditions with the power consumption of activating the high-pressure water flushing system, the activation conditions for high-pressure water flushing are determined. This provides a testing and calculation method for analyzing the drag reduction effect of the high-pressure water flushing system and determining its activation conditions. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the test of the rake tooth cutting and resistance reduction effect under high-pressure water flushing conditions provided in the embodiments of the present invention;

[0027] Figure 2 This is a schematic diagram of the high-pressure flushing system provided in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the cutting rake tooth device provided in an embodiment of the present invention.

[0029] In the diagram, 1. Water supply pump; 2. Main pipeline; 3. Main valve; 4. Water storage tank; 5. Diversion pipeline; 6. Diversion valve; 7. Flow meter; 8. Nozzle; 9. Cutting rake tooth device; 91. Rake tooth; 92. Cutting force sensor; 93. Tool holder; 94. Spacer block;

[0030] A. Running trolley; B. Soil box; C. Experimental table; D. High-pressure water flushing device. Detailed Implementation

[0031] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings:

[0032] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Example

[0035] Please see Figures 1-3 The embodiments of the present invention provide a method for testing and evaluating the resistance reduction effect of rake teeth cutting under high-pressure water flushing conditions in stiff plastic cohesive soil.

[0036] The clay soil used to prepare the molded soil has a moisture content of 20% and a density of 1.983 g / cm³. 3The plasticity index was 18.3 (belonging to clay), the liquidity index was 0.01 (stiff plastic state), and the standard penetration test (SPT) blow count was 21 blows. The single rake tooth of the cutting rake tooth device had dimensions of 75mm × 200mm and an angle of 45 degrees. A cutting force sensor 92, installed on the rake tooth 91, was used to measure the cutting resistance of a single rake tooth, with a range of 0–30000N and a sampling frequency of 200Hz. The dimensions of the soil-filling box B were 0.6m high × 5m long × 2.2m wide. Two sets of single rake tooth cutting experiments were conducted, with cutting depths of 60mm and 90mm respectively, a cutting speed of 1.3m / s, and the surface depth of the soil-filling box B submerged by water was 10cm. The nozzle 8 of the high-pressure water flushing system had a diameter of 18mm and a flow rate of 22.89m³. 3 / h.

[0037] The specific working process of this embodiment:

[0038] Step 1: Preparation of experimental soil and setup of experimental apparatus

[0039] Preparation of experimental soil:

[0040] (1) The average moisture content of the original clay soil was 2.58%. Water was sprayed into the clay soil particles using a sprinkler, and 17.5% water was added.

[0041] (2) After mixing evenly, put the mixed dispersed clay into a sealed plastic bag and let it sit for more than 24 hours.

[0042] (3) The compacted cohesive soil was compacted using a plate tamper, and a standard penetration test (SPT) was performed. The SPT results were 21 blows, the moisture content was 20%, and the density was 1.983 g / cm³. 3 Experimental clay.

[0043] Preparation of experimental setup:

[0044] (1) Running trolley A, soil box B, experimental platform C, high-pressure water flushing system D, cutting rake tooth device E. Among them, the dimensions of soil box B are 0.6m high × 5m long × 2.2m wide.

[0045] (2) The cutting rake tooth device 9 consists of rake teeth 91, a cutting force sensor 92, a cutter holder 93, and pads 94. The cutting force sensor 92 is located between the rake teeth 91 and the cutter holder 93. The rake teeth 91 are 75mm × 200mm in size and have an angle of 45 degrees. The cutting force sensor 92 has a range of 0–30000N and a sampling frequency of 200Hz. The number and size of the pads 94 are adjustable according to the thickness of the soil layer being cut. The rake teeth 91 can be replaced with rake teeth of different angles, and the vertical height can be adjusted by replacing the pads 94 of different thicknesses to change the cutting thickness of the soil. The cutting rake tooth device 9 is installed on the running trolley A.

[0046] (3) The high-pressure flushing system includes a water supply pump 1, a main pipeline 2, a main valve 3, a water storage tank 4, branch pipelines 5, branch valves 6, a flow meter 7, and nozzles 8. The nozzle diameter of the high-pressure flushing system is 18mm, the water flow velocity at the nozzle is 25m / s, the nozzle pressure is 0.32Mpa, and the nozzle flow rate is adjustable. Specifically, the water supply pump 1 is connected to the main pipeline 2, the main valve 3 is installed on the main pipeline 2, the outlet of the main pipeline 2 is connected to the inlet of the water storage tank 4, several branch pipelines 5 are set, the outlet of the water storage tank 4 is connected to each branch pipeline 5, each branch pipeline 5 is equipped with a branch valve 6 and a flow meter 7, and the outlet of each branch pipeline 5 is connected to a nozzle 8. The cutting rake tooth device 9 corresponds one-to-one with the nozzle 8. The water supply pump 1, main pipeline 2, main valve 3, water storage tank 4, branch pipelines 5, branch valves 6, and flow meter 7 are located inside the running trolley A, and the nozzles 8 are installed on the running trolley A.

[0047] Step 2: Testing the drag reduction effect of the rake teeth under high-pressure water flushing conditions

[0048] (1) First, place and fix the soil box B filled with experimental clay on the experimental table C; fix the cutting rake tooth device with cutting force sensor and high pressure water flushing system on the running trolley A; raise and lower the running trolley, adjust the horizontal (x direction) and vertical (y direction) positions of the running trolley, set the cutting soil layer thickness to 60mm and 90mm respectively, and set the running trolley travel speed to 1.3m / s (z direction);

[0049] (2) Fill the experimental platform with water, submerging the soil box by 10cm; turn off the high-pressure water flushing system, start the running trolley, and conduct an underwater cutting experiment under conditions without high-pressure water flushing; obtain the cutting resistance F1 of the rake teeth during the cutting process through the corresponding cutting force sensor.

[0050] (3) Re-raise and lower the trolley, adjust its horizontal (x-direction) and vertical (y-direction) positions, set the cutting soil layer thickness to 60mm and 90mm respectively, and set the trolley's traveling speed to 1.3m / s (z-direction); turn on the high-pressure water flushing system and adjust the nozzle flow rate to 22.89m³ / s. 3 / h, underwater cutting experiments were conducted under high-pressure water flushing conditions; the cutting resistance F2 of the rake teeth during the cutting process was obtained through the corresponding cutting force sensor.

[0051] Step 3: Analysis of the drag reduction effect of high-pressure water flushing

[0052] 1) When the cutting angle is 45 degrees, the cutting speed of the rake teeth is V = 1.3 m / s, and the cutting depth is 60 mm:

[0053] (1) The cutting resistance of a single rake tooth during cutting without high-pressure water flushing is F1; the cutting resistance of a single rake tooth during cutting with high-pressure water flushing is F2; the cutting resistance reduced by high-pressure water flushing is F1 - F2.

[0054] F1 = 2570N; F2 = 1670N; F1 - F2 = 900N; F2 / F1 = 1670 / 2570 = 65%;

[0055] After the high-pressure water flushing is turned on, the cutting resistance of a single rake tooth drops from 2570N to 1670N, and the cutting resistance is reduced to 65% of the original value, indicating that the effect of reducing resistance by high-pressure water flushing is obvious.

[0056] (2) Calculation formula for the difference in power consumed by the rake teeth in cutting the soil before and after the high-pressure water flushing system is turned on:

[0057] (In this embodiment, the number of rake teeth of the clay rake head n = 22)

[0058] W1 = (F1 - F2)·V·n = 900×1.3×22 = 25740W

[0059] (3) Calculation formula for the power consumed by the high-pressure water flushing system:

[0060] (In this embodiment, the number of nozzles of the high-pressure water flushing system of the clay rake head m = 22)

[0061] W2 = P·A·V·m = P·Q·m

[0062] Among them,

[0063]

[0064] (4) Compare the numerical values of W1 and W2. When W1 > W2, turn on the high-pressure water flushing system; when W1 ≤ W2, turn off the high-pressure water flushing system.

[0065] W1 = 25740W < W2 = 43675W; The power consumption reduced by reducing resistance by turning on the high-pressure water flushing system is less than the power consumed by the high-pressure water flushing system. At this time, it shows that it is uneconomical to turn on the high-pressure water flushing system under this working condition, and the high-pressure water flushing system should be turned off.

[0066] 2) When the cutting angle is 45 degrees, the rake tooth cutting speed is V = 1.3m / s, and the cutting depth is 90mm:

[0067] (1) The cutting resistance of a single rake tooth during cutting without high-pressure water flushing is F1; the cutting resistance of a single rake tooth during cutting with high-pressure water flushing is F2; the cutting resistance reduced by high-pressure water flushing is F1 - F2.

[0068] F1=4460N; F2=2676N; F1-F2=1784N; F2 / F1=2676 / 4460=60%;

[0069] After the high-pressure water flushing was turned on, the cutting resistance of the single rake tooth decreased from 4460N to 2676N, and the cutting resistance was reduced to 60% of the original value, indicating that the high-pressure water flushing has a significant drag reduction effect.

[0070] (2) Formula for calculating the difference in power consumption of the rake teeth cutting the soil before and after the high-pressure water flushing system is activated:

[0071] (In this embodiment, the number of rake teeth in the clay rake head is n = 22)

[0072] W1=(F1-F2)·V·n=1784×1.3×22=51022W

[0073] (3) Formula for calculating the power consumption of a high-pressure flushing system:

[0074] (In this embodiment, the number of nozzles in the high-pressure water flushing system of the clay rake head is m = 22)

[0075] W2=P·A·V·m=P·Q·m

[0076] in,

[0077]

[0078]

[0079] (4) Compare the values ​​of W1 and W2. When W1>W2, turn on the high-pressure flushing system; when W1≤W2, turn off the high-pressure flushing system.

[0080] W1 = 51022W > W2 = 43675W; the power consumption reduction due to drag reduction by turning on the high-pressure flushing system is greater than the power consumed by the high-pressure flushing system. This indicates that turning on the high-pressure flushing system can save costs under this operating condition, and the high-pressure flushing system should be turned on.

[0081] This invention tests the cutting resistance of a single rake tooth under two conditions: with and without high-pressure water flushing. The obtained data are then compared and analyzed to determine the drag-reduction effect of high-pressure water flushing during soil cutting. Simultaneously, by comparing the power consumption reduction resulting from drag reduction under high-pressure water flushing conditions with the power consumed by the high-pressure water flushing device itself, the activation conditions of the high-pressure water flushing system are determined. This testing method provides a powerful tool for analyzing the drag-reduction effect of high-pressure water flushing systems and also provides a set of testing and calculation methods for determining the activation conditions of high-pressure water flushing systems.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for testing and evaluating the drag reduction effect of rake teeth under high-pressure water flushing conditions, characterized in that, The specific test process is as follows: Step 1: Preparation of experimental soil and experimental device Prepare experimental soil with a certain particle ratio, water content, density, and standard penetration blow count that meet the requirements; The experimental device includes a running trolley, a cutting harrow tooth device, a high-pressure water flushing system, and a soil box; [[ID=**4**]]Step 2: Test on the drag reduction effect of harrow tooth cutting under high-pressure water flushing Make preparations before the test. After that, close the high-pressure water flushing system, start the running trolley, and conduct underwater cutting experiments without high-pressure water flushing; open the high-pressure water flushing system and adjust the high-pressure water flushing flow rate to conduct underwater cutting experiments under high-pressure water flushing; obtain the cutting resistance of the harrow teeth during the corresponding cutting process through the cutting force sensor; Step 3: Analysis of the drag reduction effect of high-pressure water flushing Set the cutting resistance of single harrow tooth cutting without high-pressure water flushing as F1, and the cutting resistance of single harrow tooth cutting under high-pressure water flushing as F2; Calculate the value of F2 / F1. When F2 / F1 ≤ 70%, the drag reduction effect of high-pressure water flushing is obvious; when 70% < F2 / F1 ≤ 90%, the drag reduction effect of high-pressure water flushing is relatively obvious; when F2 / F1 > 90%, the drag reduction effect of high-pressure water flushing is not obvious.

2. The method for testing and evaluating the drag reduction effect of rake teeth under high-pressure water flushing conditions according to claim 1, characterized in that, The analysis of the drag reduction effect of high-pressure water flushing in Step 3 also includes the judgment of the opening and closing conditions of the high-pressure water flushing system; Calculation formula for the power difference consumed by the harrow teeth cutting the soil before and after the high-pressure water flushing system is opened: W1 = (F1 - F2)·V·n In the formula, W1 is the power difference consumed by the harrow teeth cutting the soil before and after the high-pressure water flushing system is opened, with the unit of W; F1 - F2 is the cutting resistance reduced by high-pressure water flushing, with the unit of N; V is the cutting speed of the harrow teeth, with the unit of m / s; n is the number of harrow teeth; Calculation formula for the power consumed by the high-pressure water flushing system: In the formula, W2 is the power consumption of the high-pressure flushing system, in watts (W); P is the nozzle pressure of the high-pressure flushing system, in pads (Pa); and A is the nozzle area, in m². 2 V represents the water flow velocity at the nozzle, in m / s. ρ is the density of water, with units of kg / m³. 3 Q represents the nozzle flow rate, in meters per second (m³). 3 / s; m is the number of nozzles; When F2 / F1 ≤ 90%, calculate and compare the values of W1 and W2. When W1 > W2, open the high-pressure water flushing system; when W1 ≤ W2, close the high-pressure water flushing system.

3. The method for testing and evaluating the drag reduction effect of rake teeth under high-pressure water flushing conditions according to claim 1, characterized in that, The running trolley can achieve variable-speed movement in the x, y, and z directions; the cutting harrow tooth device is fixed on the running trolley and is used to conduct cutting experiments with different cutting angles, cutting depths, and cutting speeds; a cutting force sensor is installed on the cutting harrow tooth device to measure the cutting force of the harrow teeth; the high-pressure water flushing system is fixed on the running trolley, and the nozzle of the high-pressure water flushing system is installed in front of the harrow teeth; the soil box is used to hold the experimental soil.

4. The method for testing and evaluating the drag reduction effect of rake teeth under high-pressure water flushing conditions according to claim 1, characterized in that, The preparations before the test are as follows: First, place and fix the soil box filled with experimental soil on the experimental bench; fix the cutting harrow tooth device equipped with a cutting force sensor and the high-pressure water flushing system on the running trolley; lift and lower the running trolley, adjust the position of the running trolley in the horizontal x direction and the vertical y direction, set the thickness of the cutting soil layer, set the traveling speed of the running trolley and set it in the z direction; inject water into the experimental bench until the water surface submerges the soil box filled with soil.

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