CN107014588B - A water jet transient impact pressure test method and device based on PVDF - Google Patents

Abstract

The invention discloses a PVDF-based water jet transient impact pressure testing method and device, wherein the device comprises a water pump, a nozzle, a motor, a front cut-off disc, a rear cut-off disc, a target plate and a computer; the inlet of the water pump is connected with the water tank through a pipeline, the outlet of the water pump is connected with the nozzle through a pipeline, the motor, the rear stop disc and the target plate are arranged on the test bench, the output shaft of the motor is connected with the front stop disc, the target plate, the front stop disc and the rear stop disc are parallel, and a plurality of through holes are formed in the front stop disc corresponding to the nozzle; the rear stop disc is provided with a jet hole corresponding to the nozzle; the target plate is provided with a pressure sensor corresponding to the jet hole, and the pressure sensor is connected with a computer. The invention has simple structure and convenient operation; the invention adopts the stop disc to cut off the continuous water jet, and can test the transient impact effect of the water jet under a certain stable working pressure.

Description

A water jet transient impact pressure test method and device based on PVDF

technical field

The invention belongs to the technical field of water jet impact pressure testing, and in particular relates to a PVDF-based water jet transient impact pressure testing method and device.

Background technique

High-pressure water jet technology is a new type of technology that uses the pump body as the power source, high-speed water flow as the energy carrier, and finally acts on the target body for physical crushing. In view of the high-efficiency, dust-free, low-heat and low-vibration characteristics of high-pressure water jets for material crushing, this technology has been widely used in industrial cleaning, surface rust removal, rock cutting, mining and oil and gas drilling in recent decades. field.

High-pressure water jet rock breaking is an important application branch of this technology, which can be used in underground coal mine hydraulic mining and oil and gas jet drilling. The impact fracture of rock by water jet can be divided into two stages, that is, the initial crushing stage and the later crack propagation stage. A large number of experimental studies have shown that the impact strength required for the formation of the initial rock fragmentation core is far greater than the strength required for the crack propagation in the later stage of rock fragmentation. The reason why the water jet can break rocks efficiently is that at the initial moment when the water jet impacts the target, it will induce a huge impact pressure—water hammer pressure. The peak value of the pressure can reach dozens of times the stable impact pressure, but the duration is very short. , usually on the order of microseconds.

Therefore, it is of great significance to accurately grasp the transient impact pressure of water jet to efficiently guide water jet to break rock. At present, the Venturi tube is mainly used to test the impact pressure of the water jet, but this method can only test the pressure in the jet field, and cannot directly obtain the impact pressure of the jet hitting the target. On the other hand, the transient impact pressure of water jet has the characteristics of high intensity and short time. It is difficult for general monitoring sensors to meet the requirements of short response time, wide measurement range and high reliability. The paper "Research on Transient Dynamic Characteristics of Water Jet Impact and Rock Breaking Mechanism" uses PVDF film sensor to monitor the impact pressure of water jet, which provides a new idea for the test of transient impact pressure of water jet. However, there are still two important defects in the test method proposed in this paper: (1) using a single cut-off disc to cut off the continuous water jet is likely to cause defects such as asymmetric structure and poor convergence of the cut-off water jet; (2) high-pressure water The jet directly impinges on the PVDF film, on the one hand, it is easy to damage the sensor structure, and on the other hand, it is easy to cause the loss of tiny charge signals on the PVDF film. In addition, the test system proposed in the paper "Research on Transient Dynamic Characteristics of Water Jet Impact and Rock Breaking Mechanism" still has problems such as difficult alignment of the jet center and the center of the target body, and difficulty in adjusting the distance between the nozzle and the target body.

Contents of the invention

In order to solve the above technical problems, the present invention provides a PVDF-based water jet with simple structure and convenient operation, which can not only accurately test the impact pressure of pure water jets, but also be used to test the transient impact pressures of abrasive jets, gas jets, etc. Transient impact pressure testing device and method.

The technical solution adopted in the present invention is: a water jet transient impact pressure test device based on PVDF, including a water pump, a nozzle, a motor, a front cut-off disk, a rear cut-off disk, a target plate and a computer; the inlet of the water pump passes through a pipeline It is connected to the water tank, the outlet of the water pump is connected to the nozzle through a pipe, the motor, the rear cut-off disk and the target plate are installed on the test bench, the output shaft of the motor is connected to the front cut-off disk, the target plate, the front cut-off disk and the rear cut-off disk Parallel, the front cut-off plate is provided with a plurality of through holes corresponding to the nozzle, and the plurality of through holes are evenly arranged along the circumferential direction; the rear cut-off plate is provided with a jet hole corresponding to the nozzle; the target plate is set corresponding to the jet hole. There is a pressure sensor, and the pressure sensor is connected with the computer.

In the above PVDF-based water jet transient impact pressure testing device, the water pump is a plunger pump, and the pressure sensor is a PVDF piezoelectric sensor.

In the above-mentioned PVDF-based water jet transient impact pressure testing device, a slide rail is provided on the test bench, and the motor, the rear cut-off disk and the target plate are installed on the slide rail of the test bench.

In the above-mentioned PVDF-based water jet transient impact pressure test device, the PVDF pressure sensor includes an upper cover and a PVDF film, the upper cover is provided with a groove for accommodating the PVDF film, and the PVDF film is installed on the circular convex surface of the target plate. On the stage, the upper cover covers the PVDF film through the groove, and the upper cover is pre-tightened by bolts; the end surface of the upper cover facing the boss is provided with a wire groove connected to the groove, and the wire of the PVDF film is drawn out from the wire groove.

In the above-mentioned PVDF-based water jet transient impact pressure testing device, the outlet of the water pump is connected back to the water tank through a pipeline, and an overflow valve is provided on the pipeline.

In the above-mentioned PVDF-based water jet transient impact pressure test device, a pressure gauge is provided on the pipeline connecting the water pump and the nozzle.

A water jet transient impact pressure testing method utilizing the above-mentioned PVDF-based water jet transient impact pressure testing device, comprising the steps of:

(1) Assemble a PVDF-based water jet transient impact pressure test device;

(2) Install the PVDF sensor on the target plate;

(3) Adjust the height of the nozzle so that the center of the nozzle and the center of the jet hole on the rear cut-off plate are in a straight line, and the center of the jet hole is located on the pitch circle of the through holes on the front cut-off plate; then turn the front cut-off plate, keep the through hole away from the center of the nozzle;

(4) Adjust the position of the front cut-off disk and the target body so that the distance between the nozzle and the front cut-off disk is 3 mm, and adjust the position of the rear cut-off disk and the target body so that the distance between the rear cut-off disk and the target body is 3 mm;

(5) Turn on the computer, turn on the water pump, adjust the working pump pressure of the water pump to 10MPa, and turn on the motor after keeping it stable, so that the water jet is cut into multiple pulse jets;

(6) Collect data from the pressure sensor to obtain the impact pressure curve;

(7) Gradually reduce the pump pressure of the water pump until it is closed, and analyze and process the data.

Compared with prior art, the beneficial effect that the present invention has is:

(1) In the present invention, the front cut-off disc and the rear cut-off disc work together to cut off the continuous water jet, and the cut-off water jet obtained under a certain stable working pressure has a stable structure and good convergence, and can accurately realize the water jet flow under a certain stable working pressure. Transient impact test of water jet.

(2) The present invention uses a PVDF piezoelectric sensor to test the impact pressure, and can directly obtain the impact load on the target plate under the impact of high-pressure pure water jet, high-pressure abrasive jet, high-pressure pulse jet, etc.; the sampling frequency of the acquisition card of the present invention can be as high as 1MHZ , so the sampling time can be accurate to the order of microseconds, and the change rule of the transient impact pressure can be effectively tested.

(3) The present invention adopts the upper cover with grooves and the boss on the target plate to install PVDF film inlays, and at the same time seals the wires for PVDF signal transmission in the wire groove of the upper cover, avoiding the PVDF film from being impacted by water jets. damage problem, while ensuring the accuracy of signal transmission.

(4) The present invention uses sliding guide rails to determine the positions of the nozzle, the cut-off plate and the target body, which has the advantages of accurate positioning and convenient operation.

(5) The PVDF-based water jet transient impact pressure testing device of the present invention also has the advantages of simple structure and convenient operation.

Description of drawings

Fig. 1 is a structural diagram of the inventive PVDF-based water jet transient impact pressure test device.

Fig. 2 is a structural diagram of the front cut-off disc of the PVDF-based water jet transient impact pressure test device of the present invention.

Fig. 3 is a front view of the sensor of the PVDF-based water jet transient impact pressure testing device of the present invention.

Fig. 4 is a cross-sectional view at the sensor of the PVDF-based water jet transient impact pressure testing device of the present invention.

Figure 5 is a water jet transient impact pressure curve.

Implementation

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figures 1-4, the PVDF-based water jet transient impact pressure test device of the present invention includes a water pump 2, a nozzle 8, a test bench 5, a motor 6, a front cut-off disc 9, a rear cut-off disc 10, and a target plate 12 And computer 14; What described water pump 2 adopted is plunger pump, and the inlet of water pump 2 is connected with water tank 1 through pipeline, and the outlet of water pump 2 is connected with nozzle 8 through pipeline, and pressure gauge 4 is provided on this pipeline. The outlet of the water pump 2 is connected back to the water tank 1 through a pipeline, and the pipeline is provided with an overflow valve 3 .

Described test bench 5 is provided with slide rail 7, and described motor 6, rear cut-off disc 10 and target plate 12 are installed on the slide rail 7 of test bench, and motor 6, rear cut-off disc 10 and target plate 12 all can be Move on the slide rail 7 to adjust the positions of the motor 6, the rear cut-off disc 10 and the target plate 12.

The output shaft of the motor 6 is connected with the front cut-off disk 9 and can drive the cut-off disk 9 to rotate. The target plate 12, the front cut-off disk 9 and the rear cut-off disk 10 are parallel, and the front cut-off disk 9 is provided with four through holes 16 corresponding to the nozzles; the four through holes 16 are evenly arranged along the circumferential direction. Corresponding to the nozzle, a jet hole 17 is arranged on the rear cut-off disk 10 , and the diameter of the jet hole 17 is smaller than the diameter of the through hole 16 . The target plate 12 is provided with a pressure sensor corresponding to the jet hole 17 on the rear cut-off disc 10 , and the pressure sensor is connected to a computer 14 through an acquisition card 13 .

The pressure sensor used is a PVDF piezoelectric sensor, including a top cover 11 and a PVDF film 19, the top cover 11 is provided with a circular groove 22 for accommodating the PVDF film 19, and the PVDF film 19 is installed on the circular groove of the target plate 12. On the boss 23 , the upper cover 11 covers the PVDF film 19 through the groove 22 , and pre-tightens the upper cover 11 through the bolts in the mounting holes 21 . The end surface of the upper cover 11 facing the boss 23 is provided with a wire groove 20 communicating with the groove, and the wires of the PVDF film 19 are led out from the wire groove 20 of the upper cover 11 and connected to the acquisition card 13 .

A water jet transient impact pressure test method based on PVDF, comprising the steps of:

(1) Connect the test device according to the overall connection diagram of the water jet transient impact pressure test system;

(2) Install the PVDF film 19 on the boss 23 of the target plate 12, cover the upper cover 11 on the PVDF film 19, and adjust the pre-tightening bolts so that the upper cover 11 is closely attached to the PVDF film 19;

(3) Adjust the height of the nozzle 8 so that the center of the nozzle 8 is on a straight line with the center of the jet hole 17 on the rear cut-off disk 10, and the center of the jet hole 17 is located on the pitch circle of the four through holes 16 on the front cut-off disk ; Then rotate the front cut-off plate 9 to allow the through hole 16 to avoid the center of the nozzle 8;

(4) Adjust the position of the cut-off disk and the target body so that the distance between the nozzle and the cut-off disk is 3mm, and the distance between the cut-off disk and the target body is 3mm;

(5) Turn on the computer, open the impact pressure test acquisition and analysis software, perform zero reset processing, and change the sensor acquisition trigger mode to manual trigger;

(6) Turn on the plunger pump, adjust the working pump pressure to 10MPa through the overflow valve, and turn on the motor after keeping it stable, so that the water jet is cut off into multiple pulse jets;

(7) Manually click the sensor acquisition button to collect the data of the pressure sensor, so as to obtain the impact pressure curve shown in Figure 5;

(8) Gradually reduce the pump pressure of the water pump until it is closed, and analyze and process the data.

Claims (7)

1. A water jet transient impact pressure test method based on PVDF, which adopts the water jet transient impact pressure test device based on PVDF to realize, it is characterized in that: the water jet transient impact pressure test device based on PVDF comprises water pump, nozzle , motor, front cut-off disk, rear cut-off disk, target plate and computer; the inlet of the water pump is connected to the water tank through a pipeline, and the outlet of the water pump is connected to the nozzle through a pipeline, and the motor, the rear cut-off disk and the target plate are installed on On the test bench, the output shaft of the motor is connected to the front cut-off disk, the target plate, the front cut-off disk and the rear cut-off disk are parallel, and there are multiple through holes corresponding to the nozzles on the front cut-off disk, and the through holes are evenly arranged along the circumferential direction; A jet hole is arranged on the rear cut-off plate corresponding to the nozzle; a pressure sensor is arranged on the target plate corresponding to the jet hole, and the pressure sensor is connected to the computer; Including the following steps: (1) Assemble a PVDF-based water jet transient impact pressure test device; (2) Install the PVDF sensor on the target plate; (3) Adjust the height of the nozzle so that the center of the nozzle and the center of the jet hole on the rear cut-off plate are in a straight line, and the center of the jet hole is located on the pitch circle of the through holes on the front cut-off plate; then turn the front cut-off plate, keep the through hole away from the center of the nozzle; (4) Adjust the position of the front cut-off disk and the target body so that the distance between the nozzle and the front cut-off disk is 3 mm, and adjust the position of the rear cut-off disk and the target body so that the distance between the rear cut-off disk and the target body is 3 mm; (5) Turn on the computer, turn on the water pump, adjust the working pump pressure of the water pump to 10MPa, and turn on the motor after keeping it stable, so that the water jet is cut into multiple pulse jets; (6) Collect data from the pressure sensor to obtain the impact pressure curve; (7) Gradually reduce the pump pressure of the water pump until it is closed, and analyze and process the data. 2. the water jet transient impact pressure test method based on PVDF according to claim 1 is characterized in that: the front cut-off disc is provided with four through holes corresponding to the nozzle; the diameter of the jet hole is less than that of the through hole. diameter. 3. The PVDF-based water jet transient impact pressure testing method according to claim 1, characterized in that: the water pump is a plunger pump, and the pressure sensor is a PVDF piezoelectric sensor. 4. The water jet transient impact pressure test method based on PVDF according to claim 1, characterized in that: the test bench is provided with a slide rail, and the motor, the rear cut-off disc and the target plate are installed on the slide rail of the test bench. on track. 5. The water jet transient impact pressure test method based on PVDF according to claim 2, characterized in that: the PVDF pressure sensor comprises a loam cake and a PVDF film, the loam cake is provided with a groove for accommodating the PVDF film, and the PVDF film is installed On the circular boss of the target plate, the upper cover covers the PVDF film through the groove, and pre-tightens the upper cover through the bolt; The wires are led out from the wire guide. 6. The PVDF-based water jet transient impact pressure test method according to claim 1, characterized in that: the outlet of the water pump is connected back to the water tank through a pipeline, and the pipeline is provided with an overflow valve. 7. The PVDF-based water jet transient impact pressure test method according to claim 1, characterized in that: the pipeline connecting the water pump and the nozzle is provided with a pressure gauge.

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