阅读说明：本技术 一种基于非牛顿流体流变特性测试系统的流量控制方法 (Flow control method based on non-Newtonian fluid rheological property test system ) 是由 李祥刚 阳志强 李德才 张志力 邓艳 李辉 孙琳 张乾 张昌凡 于 2021-07-15 设计创作，主要内容包括：一种基于非牛顿流体流变特性测试系统的流量控制方法,属于非牛顿流体的流量控制领域,包括以下步骤：S1：将在线流变特性测试结果传输到流量智能控制系统内置的计算模块；S2：计算模块根据流变特性测试结果得到该物料实时的流变特性本构方程；S3：计算模块计算得到电机电流与非牛顿流体物料流量之间的对应关系；S4：根据S3的对应关系,得到流量控制数学模型,并将其内置于控制模块；S5：控制模块将反馈的实际流量与设定流量进行比较,对数学模型参数进行调整,从而快速精准控制流量大小。本发明通过电机运动精确控制生产设备某位置的流量,使非牛顿流体的流量控制精确度高,控制实时,克服了常规灌装阀灌装密封件易磨损、结构复杂、效率低的问题。(A flow control method based on a non-Newtonian fluid rheological property test system belongs to the field of flow control of non-Newtonian fluids and comprises the following steps: s1: transmitting the online rheological characteristic test result to a built-in calculation module of the intelligent flow control system; s2: the calculation module obtains a real-time rheological property constitutive equation of the material according to a rheological property test result; s3: the calculation module calculates and obtains the corresponding relation between the current of the motor and the material flow of the non-Newtonian fluid; s4: obtaining a flow control mathematical model according to the corresponding relation of S3, and arranging the flow control mathematical model in a control module; s5: the control module compares the fed back actual flow with the set flow and adjusts the parameters of the mathematical model, thereby controlling the flow rapidly and accurately. The invention accurately controls the flow of a certain position of production equipment through the movement of the motor, ensures that the flow control accuracy of the non-Newtonian fluid is high, controls the non-Newtonian fluid in real time, and solves the problems of easy abrasion, complex structure and low efficiency of the filling sealing member of the conventional filling valve.)

1. A flow control method based on a non-Newtonian fluid rheological property testing system is characterized by comprising the following steps:

s1: transmitting the online rheological characteristic test result to a built-in calculation module of the intelligent flow control system;

s2: the calculation module obtains a real-time rheological property constitutive equation of the material according to a rheological property test result;

s3: the calculation module calculates and obtains the corresponding relation between the current of the motor and the material flow of the non-Newtonian fluid;

s4: obtaining a flow control mathematical model according to the corresponding relation of S3, and arranging the flow control mathematical model in a control module;

s5: the control module compares the fed back actual flow with the set flow and adjusts the parameters of the mathematical model, thereby controlling the flow rapidly and accurately.

2. The flow control method according to claim 1, wherein the online rheological property test results of S1 include shear speed, shear stress and viscosity, and are calculated by online measurement of a non-newtonian fluid online rheological property test system installed on a production device or a production device with a function of testing total flow in real time.

3. The flow control method according to claim 1, wherein the intelligent flow control system in S1 comprises a rheological data acquisition module, a calculation module, a control module and a human-computer interaction module.

4. The flow control method according to claim 3, wherein the rheological data acquisition module completes data acquisition of the multi-element sensor through driving software, stamps a time stamp, and stores the time stamp in a real-time database.

5. The flow control method according to claim 3, characterized in that the control module is a flow tracking sliding mode controller based on sliding mode variable structure theory.

6. The flow control method according to claim 3, wherein the computing module is implemented by industrial software of an embedded or non-embedded system.

7. The flow control method according to claim 1, wherein the calculation module calculation process of S3 includes the steps of:

s3.1: calculating to obtain the relation between the motor torque and the material flow according to the rheological property constitutive equation of S2, the basic equation of the transportation process and boundary conditions;

s3.2: obtaining the relation between the motor torque and the motor current according to the motor characteristics;

s3.3: and (3) combining S3.1 and S3.2 to obtain the relation between the motor current and the material flow.

8. The flow control method according to claim 7, wherein the transport process basic equations comprise mass conservation equations, momentum quantification and energy conservation equations, and the boundary conditions comprise the shape, size, temperature of the contact part of the equipment and the material, the rotating speed and torque of the rotating part of the equipment, the speed and force of the linear motion part of the equipment, and the pressure of the material at the key position of the equipment.

9. The flow control method according to claim 1 or 7Wherein said constitutive equation comprises Newton's equationEquation of powerCarreau equationBinghan equationWagner equation

Where σ is the shear stress, σ_yIs yield shear stress, eta is shear viscosity, eta₀The viscosity of the mixture is zero in shearing,for shear rate, K, n and λ are material parameters, τ (t) is the bias stress tensor, t 'is any one time in the past, m (t-t') is the memory function, the linear visco-elastic behavior of the material is reflected, h (I)₁,I₂) A non-linear decay function, a strain dependence of the rheological behaviour of the reaction material, C^-1Is the Finger tensor.

10. The flow control method according to claim 9, wherein said Finger tensor C^-1＝F^-1·(F^T)^-1＝F^-1·(F^-1)^T(ii) a Is provided at t₁，t₂At time, the object occupies spatial configuration 1 and configuration 2, respectively, at t₁At time, any line element in the object is X, at t₂The spatial position occupied at the moment becomes x, then at t₁，t₂Gradient of deformation occurring in the object between momentsF^-1Is the inverse tensor of F.

Technical Field

The invention relates to the field of flow control of non-Newtonian fluids, in particular to a flow control method based on a non-Newtonian fluid rheological property test system.

Background

Many processing equipment exist non-Newtonian fluid transportation processes, such as chemical equipment, food processing equipment, high polymer material forming processing equipment and the like. In the use process of the devices, the flow rate is often required to be controlled, for example, in the injection molding and extrusion molding processes of high polymer materials, the flow rate entering a mold is required to be accurately controlled to control the product quality; for another example, during the canning of viscous foods (oyster sauce, porridge and the like), the instantaneous flow needs to be accurately and rapidly controlled to prevent over-filling or under-filling. The viscosity of the non-Newtonian fluid is not constant, but depends heavily on temperature, pressure, shear rate, thermal history, strain history and the like, and the control of the machine has delay characteristics, so that the flow control of the non-Newtonian fluid has the situations of inaccuracy, serious delay and the like.

For example, in the patent with the publication number of CN211203034U, namely 'a liquid leakage prevention canning valve', the technical scheme that the flow is controlled by the canning valve is adopted for accurate canning, and the canning valve has the problems of easy abrasion of a sealing piece, complex structure, low efficiency and the like; if the filling valve is not adopted, the problems of inaccurate filling metering, such as excessive filling or insufficient filling, exist.

Disclosure of Invention

In order to overcome the technical problems, the invention provides a control method for accurately controlling the flow of a certain position of production equipment through the movement of a motor, which has the following technical scheme:

a flow control method based on a non-Newtonian fluid rheological property testing system comprises the following steps:

s1: transmitting the online rheological characteristic test result to a built-in calculation module of the intelligent flow control system;

s2: the calculation module obtains a real-time rheological property constitutive equation of the material according to a rheological property test result;

s3: the calculation module calculates and obtains the corresponding relation between the current of the motor and the material flow of the non-Newtonian fluid;

s4: obtaining a flow control mathematical model according to the corresponding relation of S3, and arranging the flow control mathematical model in a control module;

s5: the control module compares the fed back actual flow with the set flow and adjusts the parameters of the mathematical model, thereby controlling the flow rapidly and accurately.

Preferably, the online rheological property test result described in S1 includes shear speed, shear stress and viscosity, and is obtained by real-time online measurement and calculation of a non-newtonian fluid online rheological property test system installed on a production device or a production device with a function of testing total flow.

Preferably, the intelligent flow control system in S1 includes a rheological data acquisition module, a calculation module, a control module, and a human-computer interaction module.

Preferably, the rheological data acquisition module completes data acquisition work of the multi-element sensor through driving software, stamps a time stamp and stores the time stamp in a real-time database.

Preferably, the control module is a flow tracking sliding mode controller based on a sliding mode variable structure theory.

Preferably, the computing module can be implemented by industrial software of an embedded or non-embedded system.

Preferably, the calculation process of the calculation module of S3 includes the following steps:

s3.1: calculating to obtain the relation between the motor torque and the material flow according to the rheological property constitutive equation of S2, the basic equation of the transportation process and boundary conditions;

s3.2: obtaining the relation between the motor torque and the motor current according to the motor characteristics;

s3.3: and (3) combining S3.1 and S3.2 to obtain the relation between the motor current and the material flow.

Preferably, the basic equations of the transportation process comprise a mass conservation equation, a momentum quantification equation and an energy conservation equation, and the boundary conditions comprise the shape, the size and the temperature of a contact part of the equipment and the material, the rotating speed and the torque of a rotating movement part of the equipment, the speed and the force of a linear movement part of the equipment and the pressure of the material at a key position of the equipment.

Preferably, the constitutive equation comprises newton's equationEquation of powerCarreau equationBinghan equationWagner equation

Where σ is the shear stress, σ_yIs yield shear stress, eta is shear viscosity, eta₀The viscosity of the mixture is zero in shearing,k, n and lambda are material parameters for shear rate, tau (t) is the bias stress tensor, t 'is any one time in the past, m (t-t') is the memory function, the linear visco-elastic behavior of the material is reflected,h(I₁,I₂) A non-linear decay function, a strain dependence of the rheological behaviour of the reaction material, C^-1Is the Finger tensor.

Preferably, the Finger tensor C^-1＝F^-1·(F^T)^-1＝F^-1·(F^-1)^T(ii) a Is provided at t₁，t₂At time, the object occupies spatial configuration 1 and configuration 2, respectively, at t₁At time, any line element in the object is X, at t₂The spatial position occupied at the moment becomes x, then at t₁，t₂Gradient of deformation occurring in the object between moments F^-1Is the inverse tensor of F.

The invention has the beneficial effects that: the flow control system is changed from a black box system to a white box system, and the flow of a certain position of production equipment is accurately controlled through the motion of a motor, so that the flow control accuracy of the non-Newtonian fluid is high, the control is real-time and efficient, and the defects of easy abrasion of a sealing piece, complex structure, low efficiency and the like in the conventional flow control mode are overcome.

Drawings

FIG. 1 is a schematic diagram illustrating the principle of closed-loop intelligent control of non-Newtonian fluid flow according to actual flow feedback when the device itself can measure flow in real time according to the present invention;

FIG. 2 shows the results of fitting the rheological data of PP (polypropylene) according to the invention using Newton's equation;

FIG. 3 shows the results of fitting the rheological data of PP (polypropylene) according to the invention using the power equation;

FIG. 4 is a schematic diagram of the principle of closed-loop control of non-Newtonian fluid flow according to flow feedback from an on-line rheometer when the device of the present invention does not have the function of measuring total flow.

Detailed Description

The invention is further illustrated by the following specific examples.

Example 1

A flow control method based on a non-Newtonian fluid rheological property testing system comprises the following steps:

s1: and transmitting the online rheological characteristic test result to a built-in calculation module of the intelligent flow control system. The online rheological characteristic test result comprises shear speed, shear stress and viscosity, and is obtained by real-time online measurement and calculation of a non-Newtonian fluid online rheological characteristic test system arranged on production equipment or production equipment with a function of testing total flow; the intelligent flow control system comprises a rheological data acquisition module, a calculation module, a control module and a man-machine interaction module: the rheological data acquisition module finishes data acquisition work of the multi-element sensor through driving software, stamps a timestamp and stores the timestamp into a real-time database; the control module is a flow tracking sliding mode controller based on a sliding mode variable structure theory; the computing module may be implemented by industrial software of an embedded or non-embedded system.

S2: and the calculation module obtains a real-time rheological property constitutive equation of the material according to the rheological property test result. The constitutive equation comprises Newton's equationEquation of powerCarreau equationBinghan equationWagner equationWhere σ is the shear stress, σ_yIs yield shear stress, eta is shear viscosity, eta₀The viscosity of the mixture is zero in shearing,for shear rate, K, n and λ are material parameters, and τ (t) is the responseThe tensor force, t 'is any time in the past, m (t-t') is a memory function, and h (I) is the linear viscoelastic behavior of the reaction material₁,I₂) A non-linear decay function, a strain dependence of the rheological behaviour of the reaction material, C^-1Is the Finger tensor. Finger tensor C^-1＝F^-1·(F^T)^-1＝F^-1·(F^-1)^T(ii) a Is provided at t₁，t₂At time, the object occupies spatial configuration 1 and configuration 2, respectively, at t₁At time, any line element in the object is X, at t₂The spatial position occupied at the moment becomes x, then at t₁，t₂Gradient of deformation occurring in the object between momentsF^-1Is the inverse tensor of F.

The goodness of fit of the constitutive equation is expressed in terms of a coefficient of determination R2 (i.e., the square of the correlation coefficient R). The value of the decision coefficient R2 is between 0 and 1, and the closer to 1, the greater the fitting degree is. A critical decision coefficient Rc2 is set, and when R2> Rc2, the test piece is considered to be qualified.

When the data of the rheological measurement module is input into the calculation module, the calculation module automatically tries the above-mentioned constitutive equations in a simple to complex sequence (i.e. tries the parameters in a sequence from less to more), and if the current constitutive equation is calculated as R2> Rc2, the current constitutive equation is considered as the best constitutive equation (the parameters are minimum on the premise of ensuring the fitting effect).

S3: the calculation module calculates and obtains the corresponding relation between the current of the motor and the material flow of the non-Newtonian fluid;

s3.1: and calculating to obtain the relation between the motor torque and the material flow according to the rheological property constitutive equation of S2, the basic equation of the transportation process and the boundary conditions. The basic equations of the conveying process comprise a mass conservation equation, a momentum quantification equation and an energy conservation equation, and the boundary conditions comprise the shape, the size and the temperature of a contact part of the equipment and the material, the rotating speed and the torque of a rotating movement part of the equipment, the speed and the force of a linear movement part of the equipment and the pressure of the material at a key position of the equipment.

S3.2: obtaining the relation between the motor torque and the motor current according to the motor characteristics;

s3.3: and (3) combining S3.1 and S3.2 to obtain the relation between the motor current and the material flow.

S4: obtaining a flow control mathematical model according to the corresponding relation of S3, and arranging the flow control mathematical model in a control module;

s5: the control module compares the fed back actual flow with the set flow and adjusts the parameters of the mathematical model, thereby controlling the flow rapidly and accurately.

Example 2

The flow control of the injection machine (the equipment can measure the flow in real time) is an important link related to the quality of the final product, and different flow rates should be adopted at different stages of injection molding: in the initial stage, the melt is made to pass through the injection runner at a high speed; when the melt enters the die cavity opening, the injection speed should be reduced in order to prevent jetting; in the process of filling the mold, the injection speed is increased to ensure that the mold cavity is quickly filled with the melt; to prevent overfilling and flashing, the injection rate should be reduced, i.e. about to fill the mold. The flow control also affects the total injection amount, and the product shrinkage injection can be caused when the total injection amount is too small; if the total shot size is too large, the product will have flash, the product pressure will be too large, and the mold will be damaged.

The plastic melt is injected into the mold cavity through a nozzle under the driving of the screw motion. Since the compression ratio of the plastic is small during the injection process and the density changes are relatively negligible, the flow rate of the plastic melt can be controlled by the advancing speed of the screw, which is the most important controlled variable during the injection phase.

In actual production, closed-loop control can be realized by installing displacement and speed sensors. The propelling speed of the screw is controlled by the flow rate of the hydraulic oil, and the flow rate of the hydraulic oil is controlled by the opening of the electro-hydraulic proportional speed regulating valve, so that the injection speed is controlled by adjusting the opening of the electro-hydraulic proportional speed regulating valve at the bottom.

As shown in fig. 1, the precise control of the flow rate of the injection machine can be realized by the following specific steps:

s1: according to the pressure and speed distribution of the melt flowing through the nozzle, on-line rheological test can be realized, air injection can be carried out at injection temperature by adopting different injection pressures/speeds (namely, the nozzle is far away from a sprue bush and directly ejects the material), the material pressure value in a charging barrel and the screw advancing speed value recorded by an injection machine are written into a calculation module, and the shear stress and shear rate data of the material are obtained according to the calculation module, for example, the table 1 is the rheological data of the PP (polypropylene) material measured at 180 ℃.

TABLE 1 rheological data of PP (Polypropylene) measured at 180 ℃

S2: obtaining a constitutive equation of the material by a calculation module: setting a critical decision coefficient R_c ²0.9, i.e. when R²>And when the fitting effect of the constitutive equation is 0.9, the fitting effect of the constitutive equation is qualified. First try a minimum parameter newton's equationThe fitting results are shown in fig. 2, and are:calculating to obtain R²＝0.79<And 0.9, judging that the fitting effect is unqualified.

Continue to try the power equationThe fitting results are shown in fig. 3, and are:calculating to obtain R²＝0.99>0.0, judging that the fitting effect is qualified, and therefore selecting the form of the power law equation. And recording the fitting result in a calculation module.

S3: and then obtaining the relation between the current and the actual flow of the hydraulic control servo valve for finally controlling the screw to advance, wherein if the fluid channel of the injection machine is in a circular tube shape, the relation between the power law fluid flow Q and the pressure difference P is as follows:

i.e. the flow Q is proportional to P^1/nIn the case where the shape of the fluid passage is fixed, the proportionality coefficient thereof is constant. Depending on the motor characteristics, the current I is proportional to the motor load, i.e. I is proportional to P. So in this case Q is proportional to I^1/n. The proportionality coefficient can be calculated according to the pressure value of the material in the material barrel and the forward speed value of the screw recorded by the injection machine in the step S1.

S4: the flow control is realized by controlling the current of the hydraulic control servo valve.

S5: in the actual injection process, the relation between the current of the hydraulic control servo valve and the actual flow is changed due to the process of filling the material into the mold, and the model parameter of the relation between the current of the hydraulic control servo valve and the actual flow is continuously adjusted according to the change of the actual flow, so that the purpose of accurately controlling the flow of the injection machine is achieved.

Example 3

The filling machine (without the function of testing the total flow and additionally provided with an online rheological property testing system) is widely applied to the industries of food (edible oil, blend oil, soybean oil, fruit juice and the like), daily chemicals (liquid detergent, laundry detergent, hand sanitizer and the like), lubricating oil (machine oil, glass water, antifreeze and the like), seasonings (soy sauce, table vinegar, extremely fresh flavor and the like), wine (mineral water, white spirit, red wine and the like) and the like. In order to accurately control the filling amount and reduce damage to equipment and meters caused by impact, vibration and the like generated by a pipeline when a valve is suddenly opened and closed, the flow rate needs to be accurately controlled. At present, the accurate filling is generally carried out by adopting a filling valve, and the filling valve has the problems of easy abrasion of a sealing piece, complex structure, low efficiency and the like.

By adopting the method shown in fig. 4, the accurate control and real-time adjustment of the flow of the filling equipment can be realized. An online rheological test system is additionally arranged on the filling equipment, and a mathematical model for flow control is obtained according to a test result of the online rheological test system, so that the control system can automatically track the system error and timely adjust the switching time of the electrohydraulic valve which can be controlled in a grading way to control the flow of the filling machine.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.