System and method for testing performance of cavitation venturi

Abstract

According to the performance test system and method for the cavitation venturi tube, when a test medium is incompressible fluid, a plunger pump outputs the constant test medium with the specified flow at the determined rotating speed, the flow speed, the flow pattern and the flow resistance of the test medium in a pipeline are constant, the pressure change caused by the pipeline structure, the flow pattern and the flow speed can be regarded as a constant value, and the performance of the cavitation venturi tube is tested. The system has and only has an independent variable of the valve opening degree of the electric control valve, so that transition of the cavitation venturi tube from the cavitation state to the non-cavitation state under the constant flow is realized, and the control and judgment on the working state of the cavitation venturi tube are more accurate; in the cavitation state and the cavitation critical point, the first inlet pressure of the cavitation venturi tube is a first constant value, and in the cavitation critical point and the non-cavitation state, the difference value between the first inlet pressure and the first outlet pressure of the cavitation venturi tube is a second constant value; according to the first constant value and the second constant value, the critical cavitation pressure ratio of the cavitation venturi tube can be calculated more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of flow regulating devices, and particularly to a performance testing system and method for a cavitation venturi tube. Background Art

[0002] A venturi tube, also known as a Venturi pipe, is a pipe that first contracts and then gradually expands. When the flowing liquid forms a stable cavitation zone behind the throat of the venturi tube, the venturi tube is in a normal working state at this time, and is called a cavitation venturi tube. The critical cavitation pressure ratio is a key performance parameter of the cavitation venturi tube, which is the ratio of the outlet pressure to the inlet pressure when the cavitation venturi tube is working in the critical cavitation state. When the actual ratio of the outlet pressure to the inlet pressure is higher than the critical cavitation pressure ratio, the cavitation venturi tube will not be able to cavitate reliably, thus losing the ability to isolate the transmission of combustion chamber pressure oscillations to the upstream. Therefore, the critical cavitation pressure ratio is a key parameter for evaluating the performance of the cavitation venturi tube. At present, a squeeze-type supply system is generally used to measure the critical cavitation pressure ratio of the cavitation venturi tube. By reducing the opening of the backpressure valve, the outlet pressure of the cavitation venturi tube is increased, and at the same time, the turning point of the inlet pressure is explored. However, the data curve near the cavitation critical point measured by this method is very steep. Due to the influence of the dynamic adjustment hysteresis time, there are great difficulties in accurate value taking and calculation; exceeding the critical cavitation pressure ratio will cause changes in the system flow rate, and the medium flow velocity, flow pattern, and flow resistance will all change accordingly. It is difficult to determine the parameter change law in the non-cavitation state, and it is also very difficult to infer the critical cavitation pressure ratio based on the non-cavitation state data. In summary, it is difficult for the prior art to accurately measure the critical cavitation pressure ratio of the cavitation venturi tube. Summary of the Invention

[0003] The purpose of the present invention is to provide a performance testing system and method for a cavitation venturi tube to accurately measure the critical cavitation pressure ratio of the venturi tube.

[0004] A performance test system for a cavitation venturi tube provided by the present invention, the system includes: an upstream module assembly, a piston pump, a flow meter, a cavitation venturi tube, an electric control valve, and a downstream module assembly connected in sequence; a first pressure gauge is also connected to the input end of the cavitation venturi tube; a second pressure gauge is also connected to the output end of the cavitation venturi tube; the piston pump, the flow meter, the first pressure gauge, the second pressure gauge, and the electric control valve are respectively connected to the measurement and control console; in the initial state, the valve opening of the electric control valve is the first preset opening; the upstream module assembly is used to input a test medium into the piston pump, output a test medium with a specified flow rate through the piston pump, and flow into the downstream module assembly through the cavitation venturi tube and the electric control valve in sequence; wherein, the magnitude of the specified flow rate is positively correlated with the rotational speed of the transmission shaft of the piston pump; the rotational speed of the transmission shaft of the piston pump is controlled by the measurement and control console; the measurement and control console is used to gradually reduce the valve opening of the electric control valve from the first preset opening in accordance with a preset adjustment step until it is reduced to the second preset opening, to obtain a plurality of data sets; wherein, each data set includes: flow rate data read by the flow meter; the first inlet pressure of the cavitation venturi tube read by the first pressure gauge, and the first outlet pressure of the cavitation venturi tube read by the second pressure gauge; according to the data in each data set, a first relationship curve is generated; wherein, the first relationship curve is used to characterize the variation laws of the first inlet pressure and the first outlet pressure of the cavitation venturi tube with time respectively; in the cavitation state and at the cavitation critical point, the first inlet pressure of the cavitation venturi tube is a first constant value, and the first outlet pressure increases linearly with time; in the cavitation critical point and the non-cavitation state, the first inlet pressure of the cavitation venturi tube increases linearly with time synchronously with the first outlet pressure, and the difference between the first inlet pressure and the first outlet pressure is a second constant value; calculate the difference between the first constant value and the second constant value to obtain the critical outlet pressure of the cavitation venturi tube at the cavitation critical point; calculate the ratio between the critical outlet pressure and the first constant value to obtain the critical cavitation pressure ratio of the cavitation venturi tube.

[0005] Further, the measurement and control console is further used for: during the process of adjusting the valve opening of the electric control valve, determining whether the first inlet pressure of the cavitation venturi tube is greater than a preset pressure threshold; if the first inlet pressure is not greater than the preset pressure threshold, determining whether the valve opening has been reduced to the second preset opening; if the valve opening has been reduced to the second preset opening, closing the piston pump to stop outputting the test medium with a specified flow rate.

[0006] Further, the system further includes: a relief valve; the relief valve is connected between the output end of the piston pump and the input end of the flow meter; the relief valve is also connected to the input end of the piston pump; the relief valve is used to open when the first inlet pressure is greater than the preset pressure threshold, so as to discharge at least a part of the test medium to the input end of the piston pump until the first inlet pressure is not greater than the preset pressure threshold.

[0007] Further, the measurement and control console is further configured to: adjust the valve opening of the electric control valve to the maximum opening, and close the plunger pump to stop outputting the test medium at the specified flow rate.

[0008] Further, the system further includes: an air storage tank; the output end of the plunger pump is further connected to the air storage tank; the air stored in the air storage tank is used to buffer the pressure fluctuation of the performance test system.

[0009] Further, the downstream module assembly includes: a downstream storage tank and a downstream liquid level gauge, and the downstream liquid level gauge is used to detect the downstream liquid level value of the test medium in the downstream storage tank; the upstream module assembly includes: an upstream storage tank and an upstream liquid level gauge, and the upstream liquid level gauge is used to detect the upstream liquid level value of the test medium in the upstream storage tank; a reflux assembly is connected between the upstream storage tank and the downstream storage tank; the volume of the upstream storage tank matches the volume of the downstream storage tank; in the initial state, the upstream liquid level value is not lower than the second proportional value of the maximum capacity of the upstream storage tank; the measurement and control console is configured to: if it is confirmed that the upstream liquid level value is not higher than the first proportional value of the maximum capacity of the upstream storage tank, or, if it is confirmed that the downstream liquid level value is not lower than the second proportional value of the maximum capacity of the downstream storage tank, open the reflux assembly to enable the test medium in the downstream storage tank to flow back to the upstream storage tank; wherein, the first proportional value is less than the second proportional value; if it is confirmed that the valve opening has been reduced to the second preset opening, close the plunger pump to stop outputting the test medium at the specified flow rate.

[0010] Further, the measurement and control console is further configured to: if it is confirmed that the upstream liquid level value is not lower than the second proportional value of the maximum capacity of the upstream storage tank, and / or, the downstream liquid level value is not higher than the first proportional value of the maximum capacity of the downstream storage tank, close the reflux assembly.

[0011] Further, the measurement and control console is further configured to: if it is confirmed that the upstream liquid level value is higher than the first proportional value of the maximum capacity of the upstream storage tank and lower than the second proportional value of the maximum capacity of the upstream storage tank, and, the downstream liquid level value is higher than the first proportional value of the maximum capacity of the downstream storage tank and lower than the second proportional value of the maximum capacity of the downstream storage tank, maintain the current state of the reflux assembly.

[0012] Further, the reflux assembly includes: a reflux filter, a reflux check valve, a first reflux pneumatic valve, a reflux water pump, and a second reflux pneumatic valve connected in sequence; the input end of the reflux filter is connected to the downstream storage tank; the output end of the second reflux pneumatic valve is connected to the upstream storage tank.

[0013] A performance test method for a cavitation venturi tube provided by the present invention includes: an upstream module assembly inputs a test medium into a plunger pump, the plunger pump outputs the test medium with a specified flow rate, and the test medium sequentially passes through the cavitation venturi tube and an electric control valve and flows into a downstream module assembly; wherein, the magnitude of the specified flow rate is positively correlated with the rotational speed of the transmission shaft of the plunger pump; the rotational speed of the transmission shaft of the plunger pump is controlled by a measurement and control console; the measurement and control console gradually reduces the valve opening of the electric control valve from a first preset opening to a second preset opening according to a preset adjustment step, and obtains a plurality of data sets; wherein, each data set includes: flow rate data read by a flow meter; the first inlet pressure of the cavitation venturi tube read by a first pressure gauge, and the first outlet pressure of the cavitation venturi tube read by a second pressure gauge; according to the data in each data set, a first relationship curve is generated; wherein, the first relationship curve is used to characterize the variation laws of the first inlet pressure and the first outlet pressure of the cavitation venturi tube with time respectively; in the cavitation state and at the cavitation critical point, the first inlet pressure of the cavitation venturi tube is a first constant value, and the first outlet pressure increases linearly with time; at the cavitation critical point and in the non-cavitation state, the first inlet pressure of the cavitation venturi tube increases linearly with time synchronously with the first outlet pressure, and the difference between the first inlet pressure and the first outlet pressure is a second constant value; calculate the difference between the first constant value and the second constant value to obtain the critical outlet pressure of the cavitation venturi tube at the cavitation critical point; calculate the ratio between the critical outlet pressure and the first constant value to obtain the critical cavitation pressure ratio of the cavitation venturi tube.

[0014] For the performance test system and method of the cavitation venturi tube provided by the present invention, when the test medium is an incompressible fluid, at a determined rotational speed, the plunger pump outputs the test medium with a constant specified flow rate, and its flow velocity, flow pattern, and flow resistance in the pipeline are constant. The pressure changes caused by the pipeline structure, flow pattern, and flow velocity can be regarded as constant values. This system has only one independent variable, i.e., the valve opening of the electric control valve, which realizes the transition of the cavitation venturi tube from the cavitation state to the non-cavitation state under a constant flow rate, and the control and determination of the working state of the cavitation venturi tube are more accurate; in the cavitation state and at the cavitation critical point, the first inlet pressure of the cavitation venturi tube is a first constant value, and at the cavitation critical point and in the non-cavitation state, the difference between the first inlet pressure and the first outlet pressure of the cavitation venturi tube is a second constant value. According to the first constant value and the second constant value, the critical cavitation pressure ratio of the cavitation venturi tube can be calculated more accurately. Description of the Drawings

[0015] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 Schematic diagram of a performance test system for a cavitation venturi tube provided by an embodiment of the present invention;

[0017] Figure 2 Schematic diagram of a first relationship curve provided by an embodiment of the present invention;

[0018] Figure 3 Schematic diagram of another performance test system for a cavitation venturi tube provided by an embodiment of the present invention;

[0019] Figure 4 Flowchart of a method for testing the performance of a cavitation venturi tube based on a constant flow system provided by an embodiment of the present invention;

[0020] Figure 5 Flowchart of a method for controlling the pressure in the performance test of a cavitation venturi tube provided by an embodiment of the present invention;

[0021] Figure 6 Flowchart of a method for circulating the working medium in the performance test of a cavitation venturi tube provided by an embodiment of the present invention;

[0022] Figure 7 Flowchart of a method for calculating the critical cavitation pressure ratio of a cavitation venturi tube provided by an embodiment of the present invention. Specific embodiments

[0023] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] As an important flow control component of a liquid rocket engine, the cavitation venturi tube has a simple structure, stable and reliable working state, and can isolate the influence of combustion chamber pressure oscillation on the supply system. The critical cavitation pressure ratio is a key parameter for evaluating the performance of the cavitation venturi tube. There are various factors affecting the critical cavitation pressure ratio, including but not limited to the friction effect between the fluid and the pipe wall and the friction effect between the gas-liquid two phases. In addition, the pipeline structure, wall roughness, medium flow rate, flow velocity, and flow pattern will all have an inestimable impact on the critical cavitation pressure ratio. It is difficult for related technologies to accurately measure the critical cavitation pressure ratio of the cavitation venturi tube. Based on this, the embodiments of the present invention provide a performance test system and method for a cavitation venturi tube, and this technology can be applied to applications that require measuring the critical cavitation pressure ratio of the cavitation venturi tube.

[0025] To facilitate the understanding of this embodiment, first, a performance test system for a cavitation venturi tube disclosed in an embodiment of the present invention will be introduced. As Figure 1 shown, the system includes: an upstream module assembly 100, a piston pump S05, a flowmeter S07, a cavitation venturi tube S08, an electric control valve S09, and a downstream module assembly 101, which are connected in sequence; a first pressure gauge is also connected to the input end of the cavitation venturi tube S08; a second pressure gauge is also connected to the output end of the cavitation venturi tube S08; the piston pump S05, the flowmeter S07, the first pressure gauge, the second pressure gauge, and the electric control valve S09 are respectively connected to a measurement and control platform 102. The cavitation venturi tube can be a venturi tube with an adjustable throat area or a venturi tube with a fixed throat area. If it is a venturi tube with an adjustable throat area, this cavitation venturi tube is usually also connected to the measurement and control platform 102; in the initial state, the valve opening of the electric control valve S09 is a first preset opening; the piston pump S05 is a positive displacement pump, which changes the volume in the cylinder through the reciprocating movement of the piston in the cylinder, so as to realize the suction and discharge of the test medium; the electric control valve S09 is a valve driven by electricity, mainly used in an automatic control system to adjust parameters such as the flow rate and pressure of the test medium in the pipeline. The electric control valve S09 combines an actuator and a control valve, and can automatically adjust the valve opening according to the instruction issued by the measurement and control platform 102 to achieve the required control effect; the above-mentioned first preset opening is usually an opening with a throttling area larger than the throat area of the cavitation venturi tube S08. For example, it can be the maximum opening of the electric control valve S09. Of course, it can also be a suitable opening selected according to actual needs, such as an opening of 90%.

[0026] The upstream module assembly 100 is used to input the test medium into the piston pump S05, output the test medium with a specified flow rate through the piston pump S05, and flow into the downstream module assembly 101 through the cavitation venturi tube S08 and the electric control valve S09 in sequence; among them, the size of the specified flow rate is positively correlated with the rotational speed of the transmission shaft of the piston pump S05; the rotational speed of the transmission shaft of the piston pump is controlled by the measurement and control platform; the above-mentioned test medium can be deionized water or other liquid media, etc., and can be specifically selected according to actual needs; the above-mentioned specified flow rate can be set according to actual needs. Under ideal conditions without considering leakage, this piston pump S05 can be regarded as a constant flow pump whose flow rate is independent of pressure, and its theoretical volume flow rate is:

[0027] Q V = nASZ;

[0028] In the formula, n is the rotational speed of the transmission shaft, A is the cross-sectional area of the plunger, S is the stroke of the plunger, and Z is the number of connections. Therefore, the above-specified flow rate is only regulated by the rotational speed of the transmission shaft of the plunger pump S05 and is not affected by the pressure changes upstream and downstream thereof; moreover, it can be seen from the above formula that the magnitude of the specified flow rate is positively correlated with the rotational speed of the transmission shaft, that is, the faster the rotational speed of the transmission shaft, the larger the specified flow rate, and the slower the rotational speed of the transmission shaft, the smaller the specified flow rate; the test medium of the specified flow rate output by the plunger pump S05 can be conveyed to the cavitation venturi tube S08 and then flow into the downstream module assembly 101 through the electric control valve S09.

[0029] The measurement and control console 102 is used to gradually reduce the valve opening of the electric control valve S09 from a first preset opening to a second preset opening at a preset adjustment step to obtain a plurality of data sets; wherein, each data set includes: the flow rate data read by the flow meter S07; the first inlet pressure of the cavitation venturi tube S08 read by the first pressure gauge, and the first outlet pressure of the cavitation venturi tube S08 read by the second pressure gauge.

[0030] The above-mentioned preset adjustment step can be understood as the adjustment amount each time the electric control valve S09 is adjusted. This adjustment step can be pre-calculated based on the rated flow rate, rated pressure, and throat area of the cavitation venturi tube S08. The specific calculation method can refer to related technologies and will not be elaborated here; the above-mentioned second preset opening is usually an opening with a throttling area smaller than the throat area of the cavitation venturi tube S08, generally a relatively small opening. For example, it can be an opening of 5%, etc., and can be specifically set according to actual requirements and will not be limited here; ideally, the flow rate data read by the above-mentioned flow meter S07 is the value corresponding to the specified flow rate calculated by the above formula. Considering that there may be fluctuations in actual applications, therefore, the flow rate data read by the flow meter S07 may be data fluctuating within the preset range of the specified flow rate, and the actual flow rate data can be read by the flow meter S07; since the first pressure gauge is arranged at the input end of the cavitation venturi tube S08 and the second pressure gauge is arranged at the output end of the cavitation venturi tube S08, therefore, the first inlet pressure corresponding to the test medium at the input end of the cavitation venturi tube S08 can be read by the first pressure gauge, and the first outlet pressure corresponding to the test medium at the output end of the cavitation venturi tube S08 can be read by the second pressure gauge; in actual implementation, the measurement and control console 102 can steadily reduce the valve opening of the electric control valve S09 according to the preset adjustment step obtained in advance, and can obtain a plurality of data sets corresponding to a plurality of time points. Each data set includes the flow rate data read by the flow meter S07, the first inlet pressure read by the first pressure gauge, and the first outlet pressure read by the second pressure gauge.

[0031] Generate a first relationship curve based on the data in each data group; wherein, the first relationship curve is used to characterize the variation laws of the first inlet pressure and the first outlet pressure of the cavitation venturi tube S08 with time respectively; in the cavitation state and at the cavitation critical point, the first inlet pressure of the cavitation venturi tube S08 is a first constant value, and the first outlet pressure increases linearly with time; at the cavitation critical point and in the non-cavitation state, the first inlet pressure of the cavitation venturi tube S08 increases linearly with time synchronously with the first outlet pressure, and the difference between the first inlet pressure and the first outlet pressure is a second constant value; calculate the difference between the first constant value and the second constant value to obtain the critical outlet pressure of the cavitation venturi tube S08 at the cavitation critical point; calculate the ratio between the critical outlet pressure and the first constant value to obtain the critical cavitation pressure ratio of the cavitation venturi tube S08.

[0032] In practical applications, the first relationship curve is actually a representative of a series of test curves. Although the horizontal axis is time, the speed of time here has no practical significance. The pressure is ultimately directly related to the valve opening of the electric control valve. The time here is converted according to the variation law of the valve opening of the electric control valve to make the pressure curve present a straight-line transition amount. All test curves can be transformed into the form of the first relationship curve through data processing. The specific conversion relationship can refer to the relevant technology implementation and will not be described in detail here.

[0033] Based on the data in each of the above data groups, a first relationship curve can be plotted, as Figure 2 shown in a schematic diagram of a first relationship curve; the first relationship curve usually also includes a flow curve, and the flow curve can be obtained by taking the average value of the flow data read at multiple time points in the steady section from multiple data groups, calculating the average flow data, and plotting the flow curve according to the average flow data, corresponding to the curve of the system flow in the figure; it can be seen from the first relationship curve that during the process of the performance test system steadily reducing the valve opening of the electric control valve S09 on the measurement and control platform 102, the following phenomena will occur in sequence:

[0034] ① The system flow is constant, the first inlet pressure of the cavitation venturi tube S08 remains unchanged, and the first outlet pressure gradually rises;

[0035] ② The system flow is constant. After the working condition of the cavitation venturi tube S08 reaches the cavitation critical point, the first inlet pressure of the cavitation venturi tube S08 rises synchronously with the first outlet pressure;

[0036] Since the output end of the plunger pump S05 is connected to the input end of the cavitation venturi tube S08 through the flowmeter S07, therefore, the above-mentioned first constant value usually refers to the supply pressure of the plunger pump. In the cavitation state, the first inlet pressure p in of the cavitation venturi tube S08 is equal to the first constant value, which is the supply pressure p pumpfeed; At the cavitation critical point and in the non-cavitation state, the difference Δp between the first inlet pressure and the first outlet pressure of the cavitation venturi tube S08 is a second constant value.

[0037] At the cavitation critical point and in the non-cavitation state, the pressure data of the cavitation venturi tube S08 conforms to the following relationship:

[0038] Δp = p in - p out ;

[0039] In the formula, p in is the first inlet pressure of the cavitation venturi tube S08, and p out is the first outlet pressure of the cavitation venturi tube S08; Therefore, the critical outlet pressure p critical of the cavitation venturi tube S08 at the cavitation critical point is:

[0040] p critical = p pumpfeed - Δp;

[0041] According to the definition of the critical cavitation pressure ratio, the critical cavitation pressure ratio p r of the cavitation venturi tube S08 can be calculated as:

[0042] p r = p critical / p pumpfeed ;

[0043] In theory, when the cavitation venturi tube S08 is in the cavitation state and the non-cavitation state, one data group corresponding to each selected time point can be obtained, and thus the supply pressure p pumpfeed of the plunger pump can be obtained, as well as the difference Δp between the first inlet pressure and the first outlet pressure of the cavitation venturi tube S08 at the cavitation critical point and in the non-cavitation state, so that the critical cavitation pressure ratio p r of the cavitation venturi tube S08 can be calculated. In actual tests, when the cavitation venturi tube S08 is in the cavitation state and the non-cavitation state, two to three data groups corresponding to each selected time point can be selected to confirm the working state of the cavitation venturi tube S08 and reduce random errors. The average value of the corresponding data in each data group is taken as the basis for calculating the critical cavitation pressure ratio p r of the cavitation venturi tube S08. For example, when in the cavitation state, the supply pressures of the plunger pump at three time points are selected and then averaged to obtain the average supply pressure of the plunger pump. When in the non-cavitation state, the first inlet pressure and the first outlet pressure corresponding to three time points are selected, and three Δp values can be calculated. The average value of these three Δp values is taken to obtain the average Δp. The average supply pressure of the plunger pump is subtracted by the average Δp to obtain the critical outlet pressure of the cavitation venturi tube S08. Dividing this critical outlet pressure by the average supply pressure of the plunger pump can obtain the critical cavitation pressure ratio p r.

[0044] In the above-mentioned cavitation venturi performance test system, the plunger pump S05 can output a constant specified flow rate of the test medium. Therefore, for incompressible fluids, the flow rate, flow pattern and flow resistance of the test medium in the pipeline of the performance test system are basically constant (only slight changes exist in the cavitation area of ​​the venturi and the electric control valve, and the impact of this slight change can be ignored). The pressure changes caused by the pipeline structure, flow rate and flow pattern can be regarded as constant values. The key data of the critical point of cavitation of the venturi can be measured at points in the cavitation state and non-cavitation state of the venturi. The performance test system has only one independent variable, which is the valve opening of the electric control valve S09, which realizes the transition of the venturi from the cavitation state to the non-cavitation state under constant flow. The critical cavitation of this scheme The pressure ratio calculation method allows the required data to be measured at one time through a single test, and the control and judgment of the working state of the cavitation venturi S08 is more accurate; in the cavitation state and the cavitation critical point, the first inlet pressure of the cavitation venturi S08 is a first constant value, and in the cavitation critical point and non-cavitation state, the difference between the first inlet pressure and the first outlet pressure of the cavitation venturi S08 is a second constant value, and the critical outlet pressure of the cavitation venturi S08 at the cavitation critical point can be calculated based on the first constant value and the second constant value, and the critical cavitation pressure ratio of the cavitation venturi S08 can be obtained by reverse deduction by calculating the ratio between the critical outlet pressure and the first constant value, and the critical cavitation pressure ratio of the cavitation venturi S08 can be calculated more accurately.

[0045] Furthermore, the measurement and control station 102 is also used to: during the process of adjusting the valve opening of the electric control valve S09, determine whether the first inlet pressure of the cavitation venturi tube S08 is greater than a preset pressure threshold; if the first inlet pressure is not greater than the preset pressure threshold, determine whether the valve opening has been reduced to a second preset opening; if the valve opening has been reduced to the second preset opening, close the plunger pump S05 to stop outputting the test medium at a specified flow rate.

[0046] The above-mentioned preset pressure threshold can be set according to actual needs. By setting the preset pressure threshold, the reliable operation of the plunger pump S05 and the cavitation venturi S08 can be guaranteed; in the process of the measurement and control station 102 adjusting the valve opening of the electric control valve S09, it can be judged in real time whether the first inlet pressure of the cavitation venturi S08 is within the preset pressure threshold. If it is within the preset pressure threshold, it can continue to judge whether the valve opening of the electric control valve S09 has been reduced to the second preset opening. If the valve opening has been reduced to the second preset opening, the flow source can be closed, that is, the plunger pump S05 can be closed to stop supplying the test medium of the specified flow rate. It is usually also necessary to vent the high-pressure gas and test medium remaining in the pipeline to restore the performance test system to its initial state; if the valve opening has not been reduced to the second preset opening, the valve opening of the electric control valve S09 can continue to be steadily reduced.

[0047] Further, the system further includes: a relief valve; the relief valve is connected between the output end of the plunger pump S05 and the input end of the flowmeter S07; the relief valve is also connected to the input end of the plunger pump S05; the relief valve is used to open when the first inlet pressure is greater than a preset pressure threshold, so as to discharge at least a part of the test medium to the input end of the plunger pump S05 until the first inlet pressure is not greater than the preset pressure threshold.

[0048] When the first inlet pressure of the cavitation venturi tube S08 is greater than the preset pressure threshold, the relief valve connected between the plunger pump S05 and the flowmeter S07 will automatically open relying on the pressure of the test medium, and discharge a part of the test medium to the input end of the plunger pump S05. Until the first inlet pressure is limited within the allowed preset pressure threshold, the relief valve can automatically close. By setting the relief valve, the safe operation of the plunger pump S05, the flowmeter S07, the cavitation venturi tube S08 and the electric control valve S09 is ensured.

[0049] Further, the measurement and control console 102 is further used for: adjusting the valve opening of the electric control valve S09 to the maximum opening, and closing the plunger pump S05 to stop outputting the test medium with a specified flow rate. Specifically, after the relief valve is started and the first inlet pressure is limited within the allowed preset pressure threshold, the measurement and control console 102 usually controls the electric control valve S09 to smoothly open its valve opening to the maximum opening, and the internal pressure of the pipeline will further drop; finally, the flow source is closed, that is, the plunger pump S05 is closed to stop supplying the test medium with a specified flow rate. Usually, it is also necessary to empty the high-pressure gas and test medium remaining in the pipeline to restore the performance test system to its initial state. At the end of the test, the valve opening of the electric control valve S09 is restored to the initial state.

[0050] Further, the system further includes: an air storage tank; the output end of the plunger pump S05 is also connected to the air storage tank; the air stored in the air storage tank is used to buffer the pressure fluctuation of the performance test system. In actual implementation, clean air is usually pre-stored in the air storage tank, and this air storage tank can be used as a buffer tank to buffer the pressure fluctuation of the performance test system and keep the pressure of the performance test system stable.

[0051] Further, the downstream module assembly 101 includes: a downstream storage tank and a downstream liquid level gauge, and the downstream liquid level gauge is used to detect the downstream liquid level value of the test medium in the downstream storage tank; the upstream module assembly 100 includes: an upstream storage tank and an upstream liquid level gauge, and the upstream liquid level gauge is used to detect the upstream liquid level value of the test medium in the upstream storage tank; in actual implementation, the downstream liquid level gauge can detect the downstream liquid level value of the test medium in the downstream storage tank at a preset detection frequency, and the upstream liquid level gauge can detect the upstream liquid level value of the test medium in the upstream storage tank at a preset detection frequency. For example, the preset detection frequency can be detection at a preset time interval or real-time detection, etc.; a reflux assembly is connected between the upstream storage tank and the downstream storage tank; the volume of the upstream storage tank matches the volume of the downstream storage tank; for example, an upstream storage tank and a downstream storage tank with the same or similar volumes can be selected, etc.; to avoid the reflux pump from idling, before the test starts, in the initial state, the upstream liquid level value should not be lower than the second proportional value of the maximum capacity of the upstream storage tank; the measurement and control console 102 is used for:

[0052] If it is confirmed that the upstream liquid level value is not higher than the first proportional value of the maximum capacity of the upstream storage tank, or if it is confirmed that the downstream liquid level value is not lower than the second proportional value of the maximum capacity of the downstream storage tank, the reflux assembly is opened to enable the test medium in the downstream storage tank to flow back to the upstream storage tank; wherein, the first proportional value is less than the second proportional value; if it is confirmed that the valve opening has been reduced to the second preset opening, the plunger pump S05 is closed to stop outputting the test medium at a specified flow rate.

[0053] Both the above-mentioned first proportional value and the second proportional value can be set according to actual needs, and the first proportional value is usually less than the second proportional value. For example, the first proportional value is one-third and the second proportional value is two-thirds, etc.; in actual implementation, if the upstream liquid level value of the test medium in the upstream storage tank is equal to or lower than the first proportional value of the maximum capacity of the upstream storage tank, or the downstream liquid level value of the test medium in the downstream storage tank reaches or exceeds the second proportional value of the maximum capacity of the downstream storage tank, the reflux assembly can be opened to replenish the test medium from the downstream storage tank to the upstream storage tank. During the reflux control process, the measurement and control console 102 usually judges in real time whether the valve opening of the electric control valve S09 has been reduced to the second preset opening. If it is confirmed that the electric control valve S09 has been reduced to the second preset opening, the flow source is usually closed, that is, the plunger pump S05 is closed to stop supplying the test medium at a specified flow rate. Usually, it is also necessary to drain the high-pressure gas and test medium remaining in the pipeline to restore the performance test system to the initial state.

[0054] If it is confirmed that the upstream liquid level value exceeds the first proportional value of the maximum capacity of the upstream storage tank, and at the same time the downstream liquid level value is lower than the second proportional value of the maximum capacity of the downstream storage tank, further judgment is usually required. Specifically, the measurement and control console 102 is also used to: if it is confirmed that the upstream liquid level value is not lower than the second proportional value of the maximum capacity of the upstream storage tank, and / or the downstream liquid level value is not higher than the first proportional value of the maximum capacity of the downstream storage tank, close the reflux assembly. If the upstream liquid level value of the test medium in the upstream storage tank reaches or exceeds the second proportional value of the maximum capacity of the upstream storage tank, and / or the downstream liquid level value of the test medium in the downstream storage tank is equal to or lower than the first proportional value of the maximum capacity of the downstream storage tank, it can be considered that there is more test medium in the upstream storage tank, and / or less test medium in the downstream storage tank. In this case, the reflux assembly can be closed to stop replenishing the test medium from the downstream storage tank to the upstream storage tank.

[0055] If it is confirmed that the upstream liquid level value is higher than the first proportional value of the maximum capacity of the upstream storage tank and lower than the second proportional value of the maximum capacity of the upstream storage tank, and the downstream liquid level value is higher than the first proportional value of the maximum capacity of the downstream storage tank and lower than the second proportional value of the maximum capacity of the downstream storage tank, maintain the current state of the reflux assembly, where the current state can be a closed state or an open state.

[0056] Further, the reflux assembly includes: a reflux filter, a reflux check valve, a first reflux pneumatic valve, a reflux water pump, and a second reflux pneumatic valve connected in sequence; the input end of the reflux filter is connected to the downstream storage tank; the output end of the second reflux pneumatic valve is connected to the upstream storage tank. In actual implementation, when it is necessary to open the reflux assembly, the first reflux pneumatic valve and the second reflux pneumatic valve can be opened, and the reflux water pump can be started; when it is necessary to close the reflux assembly, the first reflux pneumatic valve and the second reflux pneumatic valve can be closed, and the reflux water pump can be closed.

[0057] For easy understanding, refer to Figure 3 the schematic diagram of another cavitation venturi performance test system shown in

[0058] The pressurization and purging system includes: nitrogen storage tank ZX01, safety valve AQ01, solenoid valve DC01, solenoid valve Q05, solenoid valve Q07, solenoid valve Q10, filter Q01, filter Q12, check valve Q02, check valve Q08, check valve Q11, gate valve Q03, pressure reducer Q04, pressure reducer Q06, pressure reducer Q09. The nitrogen storage tank ZX01 stores pure high-pressure nitrogen. The safety valve AQ01 is normally in a normally closed state. If the pressure in the nitrogen storage tank ZX01 exceeds the specified safety value, the safety valve AQ01 will automatically open relying on the medium pressure, quickly discharge part of the medium, and automatically close until the pressure in the nitrogen storage tank ZX01 drops back to the specified safe range. The solenoid valve DC01 controls the filling or discharging of nitrogen into the nitrogen storage tank ZX01 during the test preparation stage and is in a normally closed state during the formal test. The filter Q01 blocks impurities in the nitrogen storage tank ZX01 from entering the pressurization and purging system pipeline, and the filter Q12 blocks impurities in the pressurization and purging system pipeline from entering the upstream storage tank ZX02. The filters need to be cleaned and maintained regularly to ensure their good filtering effect. The check valves Q02, Q08, and Q11 prevent the reverse flow of the medium, ensuring the safety and cleanliness of the upstream pipeline and components. The gate valve Q03 is manually opened or closed by the test personnel to control the nitrogen flow to the front of the pressure reducer in the pressurization and purging branch. The pressure reducers Q04, Q06, and Q09 output the upstream high-pressure gas as low-pressure gas with stable pressure, and their output pressures need to be set according to the downstream working conditions respectively. The pressure reducer Q04 controls the extrusion pressure of the upstream storage tank ZX02, the pressure reducer Q06 controls the constant flow supply and the purging pressure of the component test system, and the pressure reducer Q09 controls the purging pressure of the working medium return system. Among them, the purging pressure refers to the gas pressure required to purge impurities such as gas and dust in the pipeline. The purging circuit is used to control the supply of purging gas, and the purging gas is used to purge the pipeline, blowing the impurities in the pipeline to the downstream until they are discharged from the open port of the system; the purging gas can also be used for functions other than purging, such as pressurizing the pipeline when checking airtightness. Therefore, the gas pressure of the purging circuit can be adjusted according to actual needs. The solenoid valves Q05, Q07, and Q10 respectively control the pressurization of nitrogen to the upstream storage tank ZX02, the constant flow supply and the purging of the component test system, and the purging of the working medium return system.

[0059] The constant current supply and component test system includes an upstream storage tank ZX02, an air storage tank ZX03, safety valves AQ02 and AQ03, solenoid valves DC02, DC03 and DC05, a vacuum pump ZK01, pneumatic valves QD01, S04 and S10, gate valves ZF01 and S03, filters GL01, S01 and S11, a check valve S02, a plunger pump S05, a relief valve S06, a flowmeter S07, a (variable / fixed throat area) cavitation venturi S08, and an electric control valve S09. The upstream storage tank ZX02 stores deionized water to provide the test medium for the test; the storage tank ZX03 stores clean air and acts as a buffer tank to buffer the system pressure fluctuations and keep the system pressure stable. The safety valves AQ02 and AQ03 are normally in a normally closed state. If the pressure in the upstream storage tank ZX02 or the air storage tank ZX03 exceeds the specified safety value, the corresponding safety valve AQ02 or AQ03 will automatically open relying on the medium pressure, quickly discharge part of the medium, and the safety valve will automatically close until the storage tank pressure drops back to the specified safety range. During the test preparation stage, the solenoid valve DC02 controls the upstream storage tank ZX02 to discharge excess nitrogen. The upstream storage tank ZX02 is used to store and supply the liquid working medium. Below the upstream storage tank ZX02 is the liquid working medium, and above is the gas (air cushion) for pressurization and buffering. The solenoid valve DC03 controls the inflow or outflow of air to the air storage tank ZX03; during the formal test, both the solenoid valve DC02 and the solenoid valve DC03 are in a normally closed state. The vacuum pump ZK01 generates and maintains a vacuum environment by sucking the gas in the container, and the solenoid valve DC05 controls whether the vacuum pump ZK01 is connected to the upstream storage tank ZX02. The pneumatic valve QD01 allows the tester to remotely operate and execute preset instructions through the measurement and control console. The gate valve ZF01 needs to be manually opened or closed by the tester. The two cooperate to control the on-off relationship between the upstream storage tank ZX02 and the external deionized water container. The filter GL01 blocks external impurities from entering the upstream storage tank ZX02. During the test preparation stage, the solenoid valve DC05, the vacuum pump ZK01, the pneumatic valve QD01, the gate valve ZF01, and the filter GL01 cooperate to achieve the filling of deionized water into the upstream storage tank ZX02: keep the solenoid valves DC02, DC05, Q05, the pneumatic valve QD01, the second reflux pneumatic valve pneumatic valve S16, and the gate valve S03 closed, connect the open end of the filter GL01 to the external deionized water container; manually open the gate valve ZF01, turn on the vacuum pump ZK01, open the solenoid valve DC05, and after the pressure in the upstream storage tank ZX02 drops significantly, open the pneumatic valve QD01, at this time the deionized water is sucked into the upstream storage tank ZX02; continuously monitor the value of the upstream liquid level gauge YW01 and fill in the amount of water required for the test; close the pneumatic valve QD01, the gate valve ZF01, the solenoid valve DC05 in sequence, and turn off the vacuum pump ZK01 to complete the filling of deionized water.Filter S01 blocks impurities in the upstream storage tank ZX02 from entering the constant flow supply and component test system pipeline, and filter S11 blocks impurities in the constant flow supply and component test system pipeline from entering the downstream storage tank ZX04. All filters need to be cleaned and maintained regularly to ensure good filtering effect. Since the (adjustable / fixed throat area) cavitation venturi tube S08 upstream of filter S11, as the component to be measured, needs to be disassembled and installed frequently, filter S11 needs to be cleaned and maintained after each test. The check valve S02 prevents the reverse flow of the medium, ensuring the safety and cleanliness of its upstream pipeline and components. The gate valve S03 needs to be manually opened or closed by the test personnel, and the pneumatic valve S04 allows the test personnel to remotely control and execute preset instructions through the measurement and control console. The two cooperate to control the on-off of the constant flow supply and component test system pipeline. The plunger pump S05 is the pressurizing component of the constant flow supply and component test system. Under ideal conditions without considering leakage, the plunger pump S05 can be regarded as a constant flow pump whose flow is independent of pressure. The system flow is only regulated by the rotational speed of the plunger pump S05 and is not affected by the pressure changes upstream and downstream of it; the change in the throttling area of the throttling component downstream of the plunger pump S05 will not cause a change in the system flow, but only change the pressure distribution of the pipeline downstream of the plunger pump S05 and cannot adjust the system flow. The outlet pressure of the plunger pump S05 is as follows:.

[0060]

[0061] In the formula, p s is the saturated vapor pressure of the fluid under the current state (obtained by looking up the table), ρ is the fluid density (obtained by looking up the table), μ is the flow coefficient of the (adjustable / fixed throat area) cavitation venturi tube S08 (calculated from the test data), A S05_out is the cross-sectional area of the outlet pipeline of the plunger pump S05 (calculated according to the pipeline specifications); A t is the cross-sectional area of the throttling position of the constant flow supply and component test system pipeline, corresponding to the throat area of the (adjustable / fixed throat area) cavitation venturi tube S08 or the throttling area of the electric control valve S09. Specifically, when the cavitation venturi tube works in the cavitation state, the outlet pressure of the cavitation venturi tube ÷ the inlet pressure of the cavitation venturi tube ≤ the critical cavitation pressure ratio of the venturi tube. At this time, the throttling position downstream of the plunger pump S05 is at the throat of the cavitation venturi tube, and A t corresponds to the throat area of the (adjustable / fixed throat area) cavitation venturi tube S08; when the cavitation venturi tube works in the non-cavitation state, the outlet pressure of the cavitation venturi tube ÷ the inlet pressure of the cavitation venturi tube > the critical cavitation pressure ratio of the cavitation venturi tube. At this time, the throttling position downstream of the plunger pump S05 is at the narrowest position in the electric control valve S09, and A t corresponds to the throttling area of the electric control valve S09; the outlet pressure p of the plunger pump S05 S05_out is directly measured by the test; the flow data Q VIt is directly measured by the test. The system flow rate is constant throughout the test. Therefore, for incompressible fluids, the flow velocity, flow pattern, and flow resistance of the test medium in the pipeline of the performance test system are basically constant (there are only minor changes in the cavitation area of the venturi tube and at the electric control valve, and the impact caused by these minor changes can be ignored). The pressure changes caused by the pipeline structure, flow velocity, and flow pattern can be regarded as constant values. The performance test system has only one independent variable, which is the opening degree of the electric control valve, to achieve the transition of the venturi tube from the cavitation state to the non-cavitation state under a constant flow rate. The working state of the component is more accurate, and the critical cavitation pressure ratio can be deduced from the non-cavitation state data. With the constant flow supply and the cross-sectional area A of the throttling position in the pipeline of the component test system t decreases, the outlet pressure p of the plunger pump S05 S05_out increases. It should be noted that the decrease in the opening degree of the electric control valve S09 does not necessarily cause A t to decrease. Specifically, when the cavitating venturi tube operates in the cavitation state, A t is not affected by the opening degree of the electric control valve S09, and A t is always the throat area of the cavitating venturi tube; the opening degree of the electric control valve S09 needs to be reduced to a certain extent to make the cavitating venturi tube transition to the non-cavitation state. At this time, A t corresponds to the throttling area of the electric control valve S09, and the decrease in the opening degree of the electric control valve S09 will cause A t to decrease. To ensure that the pipeline pressure does not exceed the safety range, a relief valve S06 is set downstream of the plunger pump S05, forming a relief circuit with the plunger pump S05. Under normal circumstances, the relief valve S06 only conducts the plunger pump S05 and the downstream pipeline, and the relief valve S06 is in the normally closed state; if the first inlet pressure of the cavitating venturi tube exceeds the preset pressure threshold, or the outlet pressure p of the plunger pump S05 S05_out exceeds the specified safety value, the relief valve S06 will automatically open relying on the medium pressure, discharging part of the medium to the inlet of the plunger pump S05 until the outlet pressure p of the plunger pump S05 S05_out falls back within the specified safety range, and the relief valve S06 automatically closes. The flowmeter S07 monitors the constant flow supply and the flow rate of the component test system in real time. The (adjustable / fixed throat area) cavitating venturi tube S08 is the component to be tested, and the critical cavitation pressure ratio is its key performance parameter. The electric control valve S09 allows the control of the spool position through the control console, thereby adjusting the outlet pressure of the (adjustable / fixed throat area) cavitating venturi tube S08. The pneumatic valve S10 allows the test personnel to remotely operate and execute preset instructions through the control console to control the constant flow supply and the component test system to discharge the test medium to the downstream storage tank ZX04.

[0062] The working medium reflux system includes: downstream storage tank ZX04, safety valve AQ04, solenoid valve DC04, pneumatic valve QD02, first reflux pneumatic valve S14, second reflux pneumatic valve S16, gate valve ZF02, reflux filter S12, reflux check valve S13, and reflux water pump S15. The downstream storage tank ZX04 is used to store the test medium supplied by the constant flow and discharged from the component test system, and at the same time serves as the flow source of the working medium reflux system. The upstream storage tank ZX02 and the downstream storage tank ZX04 of the test system should be selected with the same or similar volumes. The safety valve AQ04 is normally in a normally closed state. If the pressure in the downstream storage tank ZX04 exceeds the specified safety value, the safety valve AQ04 will automatically open relying on the medium pressure, quickly discharge part of the medium, and automatically close until the pressure in the downstream storage tank ZX04 drops back to the specified safety range. The solenoid valve DC04 controls the inflow or outflow of air to the downstream storage tank ZX04, playing a role in regulating the internal air pressure of the downstream storage tank ZX04. The pneumatic valve QD02 allows the test personnel to remotely operate and execute preset instructions through the measurement and control console. The gate valve ZF02 needs to be manually opened or closed by the test personnel. The two cooperate to control the downstream storage tank ZX04 to discharge the excess test working medium to the outside. The filter S12 blocks the impurities in the downstream storage tank ZX04 from entering the pipeline of the working medium reflux system. The filter needs to be cleaned and maintained regularly to ensure its good filtering effect. The reflux check valve S13 prevents the reverse flow of the medium, ensuring the safety and cleanliness of the upstream pipeline and components. The first reflux pneumatic valve S14 and the second reflux pneumatic valve S16 allow the test personnel to remotely operate and execute preset instructions through the measurement and control console, respectively controlling the inflow of the test working medium into the reflux water pump S15 and the transportation of the test working medium from the reflux water pump S15 to the upstream storage tank ZX02. The reflux water pump S15 is a pressurizing component of the working medium reflux system, which transports the test working medium collected from the constant flow supply and discharged from the component test system in the downstream storage tank ZX04 back to the upstream storage tank ZX02, the flow source of the constant flow supply and the component test system, to realize the continuous recycling of the test working medium.

[0063] The measurement and control system and sensors include: upstream liquid level gauge YW01, downstream liquid level gauge YW02, thermometer WD01, thermometer WD02, pressure gauges YL01, YL02, YL03, YL04, YL05, YL06, YL07, YL08, YL09, YL10, YL11, YL12, YL13, YL14, and the measurement and control console. The upstream liquid level gauge YW01 and the downstream liquid level gauge YW02 respectively monitor the water levels in the upstream storage tank ZX02 and the downstream storage tank ZX04. The thermometers WD01 and WD02 respectively monitor the internal temperatures of the upstream storage tank ZX02 and the downstream storage tank ZX04. The pressure gauges YL01 - YL14 respectively monitor the pressures at their corresponding positions. The measurement and control console is used to read, display, and store the measured point data information, as well as preset the action instructions of each component in the test, control the start, stop, and end of the test. The measurement and control console is also used to remotely control the opening and closing of valves and monitor the working states of each sensor.

[0064] Based on the above system, there is provided a cavitation venturi performance test method based on a constant flow system as shown in Figure 4 The specific steps are as follows:

[0065] ST101, select the test object. The test object should be a cavitation venturi with an adjustable or fixed throat area, or a throttling element with the same working principle.

[0066] ST102, determine the test conditions and calculate the system parameters. Specifically, the test system parameters can be calculated based on the rated flow rate, rated pressure, and throat area of the test object, including the supply pressure, pipeline diameter, adjustment step of the backpressure valve (corresponding to the electric control valve S09), first preset opening degree, and second preset opening degree. Among them, the supply pressure specifically includes the nitrogen pressure stored in the nitrogen storage tank ZX01, the pressure of the extrusion air cushion in the upstream storage tank ZX02, the outlet pressure of the plunger pump S05 / the inlet pressure of the test object, such as the inlet pressure of the (adjustable / fixed throat area) cavitation venturi. The pipeline diameter needs to be the diameter of each part of the pipeline, ensuring that the throttling position of the system appears in the test object (adjustable / fixed throat area) cavitation venturi S08 or the electric control valve S09 rather than the pipeline itself, and there is no pressure loss that may affect the measurement accuracy. In practical applications, a minimum pipeline diameter threshold can be preset, and the pipeline of the entire system cannot be less than this pipeline diameter threshold. The adjustment step of the backpressure valve can be understood as the adjustment amount each time the backpressure valve is adjusted.

[0067] ST103, install the test components and confirm the system status; specifically, check the tightness of the test system, check the gas source pressure and the liquid level in the storage tank, check the valve opening and closing status, etc.

[0068] ST104, Start the test system.

[0069] ST105, Steadily reduce the opening of the backpressure valve of the cavitation venturi tube. The following phenomena will occur successively in the test system:

[0070] ① The system flow rate is constant, the first inlet pressure of the cavitation venturi tube remains unchanged, and the first outlet pressure gradually rises; the system flow rate is the flow rate of the plunger pump. When the overflow valve S06 is not opened, the system flow rate is also the flow rate through the cavitation venturi tube S08 of the test object (adjustable / fixed throat area). When the overflow valve S06 is not opened, the system flow rate can be directly measured by the flow meter during the test.

[0071] ② The system flow rate is constant. After the operating condition of the cavitation venturi tube reaches the cavitation critical point, the first inlet pressure of the cavitation venturi tube rises synchronously with the first outlet pressure;

[0072] ③ After the first inlet pressure of the cavitation venturi tube reaches the maximum value allowed by the system, the overflow valve opens.

[0073] If the overflow valve opens immediately when starting the test system, it indicates that the system flow rate is too large and the rotational speed of the drive shaft of the plunger pump needs to be adjusted downwards.

[0074] If the test task is completed before the first inlet pressure of the cavitation venturi tube reaches the maximum value allowed by the system, the test can be directly ended without experiencing the opening of the overflow valve.

[0075] ST106, Close the flow source, stop supplying the flow rate, drain the high-pressure gas and test medium remaining in the pipeline, and restore the test system to its initial state. Usually, after shutting down the plunger pump S05, cooperate with closing the pneumatic valve S04 (to avoid the idling of the plunger pump S05 and cut off the working medium after the plunger pump S05 is shut down).

[0076] ST107, Close the test system.

[0077] ST108, According to the data curve, referring to the method for calculating the critical cavitation pressure ratio of the venturi tube in the above-mentioned embodiment, inversely deduce the cavitation critical point of the cavitation venturi tube. The data curve refers to the original curve of the measured parameters changing with time during the test. Those required for the calculation include the flow rate curve, the first inlet pressure curve of the cavitation venturi tube, and the first outlet pressure curve of the cavitation venturi tube.

[0078] Based on the above system, there is provided a pressure control method for testing the performance of a cavitation venturi tube as shown in Figure 5 The specific steps are as follows:

[0079] ST201, Start the test.

[0080] ST202, Fill the test medium in front of the main valve (pneumatic valve S04).

[0081] ST203, the plunger pump S05 starts, and at the same time, the main valve is opened.

[0082] ST204, steadily reduce the opening of the backpressure valve of the cavitation venturi. At this time, the following situations occur in sequence: ① The system flow rate is constant, the first inlet pressure of the cavitation venturi remains unchanged, and the first outlet pressure gradually rises; ② When the system flow rate is constant and the operating condition of the cavitation venturi reaches the cavitation critical point, the first inlet pressure of the cavitation venturi rises synchronously with the first outlet pressure.

[0083] ST205, determine whether the inlet pressure of the cavitation venturi is within the maximum value allowed by the system.

[0084] ① If the judgment result of ST205 is "yes", execute ST206 to determine whether the opening of the backpressure valve of the cavitation venturi has been reduced to the target value (corresponding to the above-mentioned second preset opening). If the judgment result of ST206 is "yes", execute ST207 to close the flow source, stop supplying the flow rate, drain the high-pressure gas and test medium remaining in the pipeline, and restore the test system to the initial state; if the judgment result of ST206 is "no", then execute ST204 to continue steadily reducing the opening of the backpressure valve of the cavitation venturi.

[0085] ② If the judgment result of ST205 is "no", execute ST211 to start the overflow valve to limit the internal pressure of the pipeline below the maximum allowable safety pressure; execute ST212 to steadily open the backpressure valve of the cavitation venturi to the maximum opening, and the internal pressure of the pipeline will further drop; execute ST207 to close the flow source, stop supplying the flow rate, drain the high-pressure gas and test medium remaining in the pipeline, and restore the test system to the initial state.

[0086] If the overflow valve opens before the opening of the backpressure valve of the cavitation venturi is reduced to the target value, it is necessary to judge whether the completed operating condition covers the cavitation critical point according to the obtained inlet pressure data of the venturi. If the inlet pressure of the cavitation venturi has a stable rising section, it means that the measured operating condition covers the cavitation critical point well and there is no need to retest; if the inlet pressure of the cavitation venturi does not have a rising section or the rising section is very short, it means that the system flow rate setting is too large, and it is necessary to lower the preset target speed of the plunger pump and restart the test.

[0087] ST208, the test ends.

[0088] Based on the above system, a performance test working medium circulation method for a cavitation venturi as shown in Figure 6 is provided, and the specific steps are as follows:

[0089] ST301, the test starts.

[0090] ST302, fill the test medium in front of the main valve (pneumatic valve S04).

[0091] ST303, start the plunger pump S05 and open the main valve simultaneously.

[0092] ST304, monitor the liquid levels of each storage tank in real time, including the upstream liquid level gauge YW01 of the test system and the downstream liquid level gauge YW02 of the test system.

[0093] ST305, respectively judge the relationship between the liquid level of each storage tank and the maximum capacity of the storage tank. The upstream storage tank of the test system and the downstream storage tank of the test system should be selected with the same or similar volumes; to avoid the idling of the return water pump, before the start of the test, the upstream liquid level value should not be lower than the second proportional value of the maximum capacity of the upstream storage tank.

[0094] ① If the liquid level YW01 of the upstream storage tank of the test system is equal to or lower than 1 / 3 of the maximum capacity of the storage tank, or the liquid level YW02 of the downstream storage tank of the test system reaches or exceeds 2 / 3 of the maximum capacity of the storage tank, execute ST311, open the first return pneumatic valve S14 and the second return pneumatic valve S16 in the working medium return system, start the return water pump S15, and supplement the test medium from the downstream storage tank of the test system to the upstream storage tank of the test system.

[0095] ② If the liquid level YW01 of the upstream storage tank of the test system is higher than 1 / 3 of the maximum capacity of the storage tank, and at the same time the liquid level YW02 of the downstream storage tank of the test system is lower than 2 / 3 of the maximum capacity of the storage tank, execute ST306 for further judgment, specifically as follows:

[0096] (a) If the liquid level YW01 of the upstream storage tank of the test system reaches or exceeds 2 / 3 of the maximum capacity of the storage tank, and / or, the liquid level YW02 of the downstream storage tank of the test system is equal to or lower than 1 / 3 of the maximum capacity of the storage tank, execute ST307, close the first return pneumatic valve S14 and the second return pneumatic valve S16 of the working medium return system, and turn off the return water pump S15.

[0097] (b) If the liquid level YW01 of the upstream storage tank of the test system is lower than 2 / 3 of the maximum capacity of the storage tank, and at the same time the liquid level YW02 of the downstream storage tank of the test system is higher than 1 / 3 of the maximum capacity of the storage tank, the working medium return system maintains the current working state without adjustment.

[0098] ST308, judge whether the opening of the back pressure valve of the cavitation venturi tube has been reduced to the target value.

[0099] ① If the judgment result of ST308 is "yes", execute ST309, close the flow source, stop supplying the flow, drain the high-pressure gas and test medium remaining in the pipeline, and restore the test system to the initial state.

[0100] ② If the judgment result of ST308 is "no", then execute ST304 to continue monitoring the liquid levels of each storage tank in real time.

[0101] ST310, the test ends.

[0102] Based on the above system, provided as follows Figure 7 A method for calculating the critical cavitation pressure ratio of a cavitation venturi tube provided by an embodiment of the present invention, the specific steps are as follows:

[0103] ST401, in the cavitation stage of the cavitation venturi tube, take the pressure measured by the first pressure gauge at a certain moment (or take the pressures measured by the first pressure gauge at multiple moments, and take the average after removing abnormal values) as the inlet pressure p of the cavitation venturi tube at the cavitation critical point in .

[0104] ST402, in the non-cavitation stage of the cavitation venturi tube, take the difference between the pressures measured by the first pressure gauge and the second pressure gauge at a certain moment (or take the differences between the pressures measured by the first pressure gauge and the second pressure gauge at multiple moments, and take the average after removing abnormal values) as the difference Δp between the inlet pressure and the outlet pressure of the cavitation venturi tube at the cavitation critical point.

[0105] ST403, according to the inlet pressure p of the cavitation venturi tube at the cavitation critical point in and the difference Δp between the inlet pressure and the outlet pressure of the cavitation venturi tube at the cavitation critical point, subtract to obtain the outlet pressure p of the cavitation venturi tube at the cavitation critical point out .

[0106] ST404, according to the outlet pressure p of the cavitation venturi tube at the cavitation critical point out and the inlet pressure p of the cavitation venturi tube at the cavitation critical point in , divide to obtain the critical cavitation pressure ratio p of the cavitation venturi tube r .

[0107] The above performance test system for the cavitation venturi tube is applicable to the performance test of the cavitation venturi tube of a liquid rocket engine, and is also applicable to the performance test of the cavitation venturi tube of a solid-liquid rocket engine, a combined power engine, and other engines with high requirements for the reliability and accuracy of flow regulation. This solution also solves the problem of the test medium circulation during the performance test of the cavitation venturi tube, and can achieve long-term testing with a limited amount of test medium.

[0108] For the performance test system of the above cavitation venturi tube, a new method for accurately measuring the critical cavitation pressure ratio of the cavitation venturi tube is proposed: keeping the system flow rate constant, reducing the opening degree of the back pressure valve of the cavitation venturi tube, and according to the non-cavitation state data, calculating the difference between the outlet pressure and the inlet pressure of the cavitation venturi tube under the critical cavitation state, and then inversely deducing the critical cavitation pressure ratio of the cavitation venturi tube. During the whole testing process of this method, the system flow rate is constant. Under the non-cavitation state, for incompressible fluids, the flow velocity, flow pattern, and flow resistance of the medium are also constant, and the critical cavitation pressure ratio can be inversely deduced according to the non-cavitation state data. Relying on this testing method, the performance test system designed in this scheme is an experimental system based on a plunger pump. This experimental system uses nitrogen pressurization and purging; an air buffer tank and an overflow valve are arranged downstream of the plunger pump to ensure stable flow rate and the pressure is within a safe range; an electric control valve is arranged downstream of the cavitation venturi tube to adjust the back pressure; two water tanks are arranged upstream and downstream of the system, and the deionized water in the two water tanks can circulate, allowing the system to carry out long-term continuous testing.

[0109] The above performance test system can accurately calculate the critical cavitation pressure ratio of the cavitation venturi tube based on a constant flow system: keeping the system flow rate constant, steadily reducing the opening degree of the back pressure valve of the cavitation venturi tube, and measuring the system flow rate Q (constant value), the inlet pressure p of the cavitation venturi tube under the cavitation state in (i.e., the supply pressure p of the plunger pump pumpfeed ), the difference Δp (constant value) between the inlet pressure and the outlet pressure of the cavitation venturi tube at the critical cavitation point and under the non-cavitation state; through the difference Δp between the outlet pressure and the inlet pressure of the cavitation venturi tube under the critical cavitation state and the supply pressure p of the plunger pump pumpfeed , inversely deduce the critical cavitation pressure ratio p of the cavitation venturi tube r .

[0110] For the method for measuring and calculating the critical cavitation pressure ratio of the venturi tube proposed by the present invention, the system flow rate is constant throughout the testing process. Therefore, for incompressible fluids, the flow velocity, flow pattern, and flow resistance of the test medium in the pipeline of the performance test system are basically constant (there are only slight changes in the cavitation area of the cavitation venturi tube and at the electric control valve, and the influence brought by this slight change can be ignored), and the pressure changes caused by the pipeline structure, flow velocity, and flow pattern can be regarded as constant values. The performance test system has only one independent variable, i.e., the opening degree of the electric control valve, to realize the transition of the cavitation venturi tube from the cavitation state to the non-cavitation state under a constant flow rate. The working state of the components is more accurate, and the critical cavitation pressure ratio can be inversely deduced according to the non-cavitation state data. Compared with the prior art, this scheme avoids the non-linear pressure loss caused by the pipeline structure and flow pattern changes in the performance test of the cavitation venturi tube, and can calculate the critical cavitation pressure ratio of the cavitation venturi tube more accurately.

[0111] Compared with the prior art, the method for measuring and calculating the critical cavitation pressure ratio of the cavitation venturi tube proposed in this solution allows only the selected key points to be measured without continuously measuring the entire variation curve. The pressure control method for the performance test of the cavitation venturi tube based on a constant flow system proposed in this solution, with the plunger pump, the back pressure valve of the cavitation venturi tube, and the overflow valve cooperating with each other, enables the cavitation venturi tube to transition from the cavitation state to the critical cavitation state and finally to the non-cavitation state. The test process covers all working states of the cavitation venturi tube, achieving the goal of measuring the critical cavitation pressure ratio of the cavitation venturi tube. At the same time, the overflow valve ensures that the pipeline pressure of the test system is always within the safe range. Compared with the venturi tube performance test method using a vane pump, this solution avoids the situation of damage to the pressurizing components caused by changes in flow rate and pressure.

[0112] Compared with the traditional solution, the working medium circulation method for the performance test of the cavitation venturi tube proposed in this solution can collect the discharged test medium, filter it, boost the pressure through a water pump, and transport it back to the flow source of the constant flow supply and component test system. The test medium circulation system collects the discharged test medium and transports it back to the flow source of the performance test system, realizing the continuous circulation and flow of the test medium throughout the system during the test process, and allowing the system to carry out long-term continuous tests. At the same time, only one filling is required before starting the system throughout the test. The entire set of tests consumes at most the amount of water corresponding to the full volume of the upstream storage tank ZX02. Compared with the traditional test system that adds water immediately when the test is completed, the filling frequency is reduced, the test preparation time and labor consumption are saved, the required amount of water is reduced, and the test medium is saved.

[0113] The working medium circulation method for the performance test of the cavitation venturi tube proposed in this solution, compared with the traditional solution that determines the start and stop of the return system through manual judgment, allows the system to automatically switch the working state of the return system according to the real-time monitoring values of the upstream liquid level gauge YW01 and the downstream liquid level gauge YW02, effectively avoiding the situation of insufficient water volume in the upstream storage tank of the test system and too high water level in the downstream storage tank of the test system.

[0114] Since the pressure change generated when the cavitation venturi tube just transitions from the cavitation state to the non-cavitation state is very small and difficult to distinguish from the system pressure oscillation, when testing the performance of the cavitation venturi tube in the prior art, it is usually necessary for the test personnel to judge based on experience whether the cavitation venturi tube is at the critical cavitation point. The method for measuring and calculating the critical cavitation pressure ratio of the cavitation venturi tube proposed in this solution does not require subjective judgment and decision-making by the test personnel during the whole process of measurement and calculation, and the measurement and calculation results are objective. Therefore, it allows the measurement and control console to independently execute the test and calculation programs, and train a highly reliable venturi tube machine learning model according to the measurement and calculation results, and then predict the task-oriented working effect of the cavitation venturi tube based on this model.

[0115] A method for testing the performance of a cavitation venturi tube provided by the present invention, the method comprising the following steps:

[0116] Step 1: The upstream module assembly inputs the test medium into the plunger pump. The plunger pump outputs the test medium with a specified flow rate, which then flows through the cavitation venturi tube and the electric control valve in sequence and into the downstream module assembly. The magnitude of the specified flow rate is positively correlated with the rotational speed of the transmission shaft of the plunger pump. The rotational speed of the transmission shaft of the plunger pump is controlled by the measurement and control console.

[0117] Step 2: The measurement and control console gradually reduces the valve opening of the electric control valve from the first preset opening in accordance with a preset adjustment step until it is reduced to the second preset opening, obtaining multiple data sets. Each data set includes: the flow rate data read by the flow meter; the first inlet pressure of the cavitation venturi tube read by the first pressure gauge, and the first outlet pressure of the cavitation venturi tube read by the second pressure gauge.

[0118] Step 3: According to the data in each data set, a first relationship curve is generated. The first relationship curve is used to characterize the variation laws of the first inlet pressure and the first outlet pressure of the cavitation venturi tube with time respectively. In the cavitation state and at the cavitation critical point, the first inlet pressure of the cavitation venturi tube is a first constant value, and the first outlet pressure increases linearly with time. At the cavitation critical point and in the non-cavitation state, the first inlet pressure of the cavitation venturi tube increases linearly with time synchronously with the first outlet pressure, and the difference between the first inlet pressure and the first outlet pressure is a second constant value.

[0119] Step 4: Calculate the difference between the first constant value and the second constant value to obtain the critical outlet pressure of the cavitation venturi tube at the cavitation critical point.

[0120] Step 5: Calculate the ratio between the critical outlet pressure and the first constant value to obtain the critical cavitation pressure ratio of the cavitation venturi tube.

[0121] In the above performance test method of the cavitation venturi tube, in the cavitation state and at the cavitation critical point, the first inlet pressure of the cavitation venturi tube S08 is a first constant value. At the cavitation critical point and in the non-cavitation state, the difference between the first inlet pressure and the first outlet pressure of the cavitation venturi tube S08 is a second constant value. According to the first constant value and the second constant value, the critical outlet pressure of the cavitation venturi tube S08 at the cavitation critical point can be calculated. By calculating the ratio between the critical outlet pressure and the first constant value, the critical cavitation pressure ratio of the cavitation venturi tube S08 can be inversely deduced, and the critical cavitation pressure ratio of the cavitation venturi tube S08 can be calculated more accurately.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A performance test system for a cavitation venturi, characterized in that: The system comprises: an upstream module assembly, a plunger pump, a flow meter, a cavitation venturi, an electric regulating valve and a downstream module assembly connected in sequence; the input end of the cavitation venturi is also connected to a first pressure gauge; the output end of the cavitation venturi is also connected to a second pressure gauge; the plunger pump, the flow meter, the first pressure gauge, the second pressure gauge and the electric regulating valve are respectively connected to a measurement and control station; in an initial state, the valve opening of the electric regulating valve is a first preset opening; The upstream module assembly is used to input the test medium into the plunger pump, output the test medium of the specified flow rate through the plunger pump, and flow into the downstream module assembly through the cavitation venturi and the electric regulating valve in sequence; wherein the size of the specified flow rate is positively correlated with the speed of the transmission shaft of the plunger pump; the speed of the transmission shaft of the plunger pump is controlled by the measurement and control console; The control station is used to gradually reduce the valve opening of the electric regulating valve from the first preset opening according to the preset adjustment step until it is reduced to the second preset opening, thereby obtaining a plurality of data groups; wherein each of the data groups includes: flow data read by the flow meter; the first inlet pressure of the cavitation venturi tube read by the first pressure gauge, and the first outlet pressure of the cavitation venturi tube read by the second pressure gauge; A first relationship curve is generated according to the data in each of the data groups; wherein the first relationship curve is used to characterize the variation rules of the first inlet pressure and the first outlet pressure of the cavitation venturi respectively over time; in the cavitation state and the cavitation critical point, the first inlet pressure of the cavitation venturi is a first constant value, and the first outlet pressure increases linearly over time; in the cavitation critical point and the non-cavitation state, the first inlet pressure of the cavitation venturi increases linearly over time synchronously with the first outlet pressure, and the difference between the first inlet pressure and the first outlet pressure is a second constant value; Calculating the difference between the first constant value and the second constant value to obtain a critical outlet pressure of the cavitation venturi at the cavitation critical point; The ratio of the critical outlet pressure to the first constant value is calculated to obtain a critical cavitation pressure ratio of the cavitation venturi.

2. The system according to claim 1, characterized in that The control station is also used for: In the process of adjusting the valve opening of the electric regulating valve, determining whether the first inlet pressure of the cavitation venturi is greater than a preset pressure threshold; If the first inlet pressure is not greater than the preset pressure threshold, determining whether the valve opening has been reduced to the second preset opening; If the valve opening has been reduced to the second preset opening, the plunger pump is turned off to stop outputting the test medium at a specified flow rate.

3. The system according to claim 2, characterized in that The system further comprises: a relief valve; the relief valve is connected between the output end of the plunger pump and the input end of the flow meter; the relief valve is also connected to the input end of the plunger pump; The overflow valve is used to open when the first inlet pressure is greater than the preset pressure threshold, so as to discharge at least a portion of the test medium to the input end of the plunger pump until the first inlet pressure is no greater than the preset pressure threshold.

4. The system according to claim 3, characterized in that The control station is also used for: The valve opening of the electric regulating valve is adjusted to the maximum opening, and the plunger pump is turned off to stop outputting the test medium at a specified flow rate.

5. The system according to claim 2, characterized in that The system further comprises: an air tank; the output end of the plunger pump is also connected to the air tank; The air stored in the air tank is used to buffer the pressure fluctuation of the performance testing system.

6. The system according to claim 2, characterized in that The downstream module assembly includes: a downstream tank and a downstream level gauge, the downstream level gauge is used to detect the downstream level value of the test medium in the downstream tank; the upstream module assembly includes: an upstream tank and an upstream level gauge, the upstream level gauge is used to detect the upstream level value of the test medium in the upstream tank; a reflux assembly is connected between the upstream tank and the downstream tank; the volume of the upstream tank matches the volume of the downstream tank; in an initial state, the upstream level value is not less than a second proportional value of the maximum capacity of the upstream tank; the measurement and control station is used to: If it is confirmed that the upstream liquid level value is not higher than a first proportional value of the maximum capacity of the upstream tank, or if it is confirmed that the downstream liquid level value is not lower than a second proportional value of the maximum capacity of the downstream tank, opening the reflux component to allow the test medium in the downstream tank to reflux to the upstream tank; wherein the first proportional value is smaller than the second proportional value; If it is confirmed that the valve opening has been reduced to the second preset opening, the plunger pump is turned off to stop outputting the test medium at a specified flow rate.

7. The system according to claim 6, characterized in that The control station is also used for: If it is confirmed that the upstream liquid level value is not lower than a second proportional value of the maximum capacity of the upstream tank, and / or the downstream liquid level value is not higher than a first proportional value of the maximum capacity of the downstream tank, the reflux component is closed.

8. The system according to claim 6, characterized in that The control station is also used for: If it is confirmed that the upstream liquid level value is higher than the first proportional value of the maximum capacity of the upstream tank and lower than the second proportional value of the maximum capacity of the upstream tank, and the downstream liquid level value is higher than the first proportional value of the maximum capacity of the downstream tank and lower than the second proportional value of the maximum capacity of the downstream tank, the current state of the reflux component is maintained.

9. The system according to claim 6, characterized in that The reflux component includes: a reflux filter, a reflux check valve, a first reflux pneumatic valve, a reflux water pump and a second reflux pneumatic valve connected in sequence; the input end of the reflux filter is connected to the downstream storage tank; the output end of the second reflux pneumatic valve is connected to the upstream storage tank.

10. A performance test method for a cavitation venturi, characterized in that: The method comprises: The upstream module component inputs the test medium into the plunger pump, and the test medium of the specified flow rate is outputted through the plunger pump, and flows into the downstream module component through the cavitation venturi and the electric regulating valve in sequence; wherein the size of the specified flow rate is positively correlated with the speed of the transmission shaft of the plunger pump; the speed of the transmission shaft of the plunger pump is controlled by the measurement and control console; The control station gradually reduces the valve opening of the electric regulating valve from the first preset opening until it is reduced to the second preset opening according to the preset adjustment step, and obtains multiple data groups; wherein each of the data groups includes: flow data read by the flow meter; the first inlet pressure of the cavitation venturi read by the first pressure gauge, and the first outlet pressure of the cavitation venturi read by the second pressure gauge; A first relationship curve is generated according to the data in each of the data groups; wherein the first relationship curve is used to characterize the variation rules of the first inlet pressure and the first outlet pressure of the cavitation venturi respectively over time; in the cavitation state and the cavitation critical point, the first inlet pressure of the cavitation venturi is a first constant value, and the first outlet pressure increases linearly over time; in the cavitation critical point and the non-cavitation state, the first inlet pressure of the cavitation venturi increases linearly over time synchronously with the first outlet pressure, and the difference between the first inlet pressure and the first outlet pressure is a second constant value; Calculating the difference between the first constant value and the second constant value to obtain a critical outlet pressure of the cavitation venturi at the cavitation critical point; The ratio of the critical outlet pressure to the first constant value is calculated to obtain a critical cavitation pressure ratio of the cavitation venturi.

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