A method for controlling the flow of concrete and an automated system for the production of foamed concrete

Abstract

The application discloses a concrete flow control method and an automatic foamed concrete preparation system. The system comprises a concrete metering tank and a controller. A controllable valve assembly is arranged at the discharge port of the metering tank. The controllable valve assembly is connected with the controller. The metering tank is characterized in that a weight sensor is arranged below the metering tank. The method is applied to the controller and comprises the following steps: receiving a set target flow; receiving the weight of the metering tank in real time; taking the target flow as an instantaneous mass flow, taking the weight of the metering tank as the mass of residual material, determining a target valve opening degree based on the mapping relationship between the valve opening degree and the mass of residual material and the instantaneous mass flow, and performing opening degree control on the controllable valve assembly. The application does not depend on a sensor and can cope with flow fluctuation caused by the change of the material level in the tank.

Description

Technical Field

[0001] This invention belongs to the field of concrete engineering technology, and particularly relates to a concrete flow control method and an automated foam concrete preparation system. Background Technology

[0002] In concrete pouring, flow control is a crucial step in ensuring pouring quality. Traditional concrete flow control largely relies on manual methods based on on-site experience. This involves manually adjusting the opening of the mixing tank's discharge valve, relying on visual observation or past experience to determine if the pouring flow rate meets requirements, and thus adjusting the flow rate accordingly. To address the drawbacks of manual operation, some solutions involve installing online flow meters (such as electromagnetic flow meters or turbine flow meters) in the discharge pipeline to collect flow signals in real time. The controller then adjusts the valve opening or pump speed based on the deviation between the flow signal and the target flow rate.

[0003] However, this sensor-based control method is unreliable when dealing with high-viscosity, highly abrasive non-Newtonian fluids such as concrete. This is because the aggregates and mortar in concrete severely wear down the flow meter's measuring components, and the high-viscosity slurry easily adheres to the inner wall of the sensor, causing blockages and drifting of the measurement signal. This necessitates frequent maintenance and calibration of the flow meter, and may even force shutdowns, severely impacting construction efficiency. Furthermore, the sensor-feedback-based control logic exhibits significant response lag to nonlinear concrete fluids, and the control algorithm is complex, making it difficult to achieve stable and precise flow regulation. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a concrete flow control method and an automated foamed concrete preparation system, which can achieve accurate flow control of concrete without relying on sensors.

[0005] To achieve the above objectives, a first aspect of the present invention provides a concrete flow control method applied to a concrete conveying system. The system includes a concrete metering tank and a controller. A controllable valve assembly is provided at the outlet of the metering tank and is connected to the controller. The method is characterized by having a weight sensor located below the metering tank. The method, applied to the controller, includes the following steps: Receive the set target traffic; Real-time reception of the metering tank weight; The target flow rate is taken as the instantaneous mass flow rate, and the weight of the metering tank is taken as the mass of the remaining material. Based on the mapping relationship between the valve opening, the mass of the remaining material, and the instantaneous mass flow rate, the target valve opening is determined and the opening control is performed on the controllable valve assembly.

[0006] In some embodiments, the mapping relationship between the valve opening degree and the remaining material mass and instantaneous mass flow rate is established as follows: Acquire data on the change of outflow quality over time under multiple opening conditions; Based on the initial total mass of the mixing tank, determine the data on the change of the mass of the remaining material over time under multiple opening conditions; Curve fitting was performed on the outflow mass change data over time under each set of opening conditions to obtain multiple cumulative outflow mass functions; Differentiating each cumulative outflow mass function yields multiple instantaneous mass flow functions; Based on the remaining material mass and instantaneous mass flow rate at each moment under the multiple opening conditions, a mapping relationship between valve opening and remaining material mass and instantaneous mass flow rate is established.

[0007] In some embodiments, the mapping relationship between valve opening degree and remaining material mass and instantaneous mass flow rate is in the form of a three-dimensional lookup table or a multivariate function.

[0008] In some embodiments, the metering tank is provided with multiple support legs below it, and each support leg is provided with a weight sensor.

[0009] In some embodiments, the controllable valve assembly is a slide valve.

[0010] A second aspect of the present invention provides an automated foamed concrete preparation system, comprising a concrete metering tank, a programmable foam generator, a mixer, and a controller. The mixer has two inlets at its input end, which are respectively connected to the outlets of the concrete metering tank and the programmable foam generator. A controllable valve assembly is provided at the outlet of the concrete metering tank. Both the controllable valve assembly and the programmable foam generator are connected to the controller. A weight sensor is also provided below the concrete metering tank. The controller is configured to perform opening control on the controllable valve assembly based on the concrete flow control method described above. Target density for receiving foamed concrete products; Calculate the real-time weight change rate based on the real-time weight of the metering tank; The actual mass flow rate of the slurry is calculated based on the real-time weight change rate. Based on the actual mass flow rate and target density of the slurry, calculate the required foam volume flow rate, control the foam generator to produce and inject the corresponding amount of foam into the mixer.

[0011] In some embodiments, the mixer includes a tube with two inlets at one end for feeding slurry and foam, respectively, and a foam concrete outlet at the other end. Inside the tube, a spiral shaft is provided along the central axis of the tube. The spiral shaft is divided into two sections: a mixing section near the raw material inlet and a transmission section near the outlet. The blades of the mixing section are three-bladed, and the blades of the transmission section are continuous spiral blades.

[0012] In some embodiments, calculating the required foam volume flow rate based on the actual mass flow rate and target density of the slurry includes: obtaining the slurry density and the target density of the foamed concrete; calculating the ideal foam volume flow rate required for the current actual mass flow rate based on the principle that the sum of the slurry volume and the foam volume equals the total volume of the foamed concrete; and calculating the required actual foam volume flow rate based on the ideal foam volume flow rate and the foam breaking rate.

[0013] In some embodiments, controlling the foam generator to produce and inject a corresponding amount of foam into the mixer includes: determining the frequency control parameters of the air pump and liquid pump motors based on the required foam volumetric flow rate, according to a pre-calibrated mapping relationship between the foam volumetric flow rate and the frequency of the air pump and liquid pump motors.

[0014] In some embodiments, the method further includes: controlling the operating frequency of the mixer motor based on the mass flow rate of the foamed concrete, according to the relationship between the mass flow rate of the foamed concrete and the frequency of the mixer motor.

[0015] One or more of the above technical solutions establish a mapping relationship between valve opening and the mass of remaining material and instantaneous mass flow rate. By combining the target flow rate and the real-time weight of the metering tank to determine the valve opening, the discharge flow rate can be accurately controlled, avoiding errors caused by manual control. At the same time, adjusting the valve opening based on the mass of remaining material can cope with flow fluctuations caused by changes in the material level in the tank, thereby maintaining a stable flow rate during the pouring process.

[0016] The above solution also eliminates the need to rely on easily worn and clogged online flow meters, thereby reducing potential failure points, lowering maintenance costs and downtime risks. It is unaffected by changes in the density of concrete materials and is particularly suitable for metering slurries with unstable densities, such as slag-based materials. Attached Figure Description

[0017] The dimensions and scales in the accompanying drawings do not represent the actual dimensions and scales of the product. The drawings are for illustrative purposes only, and some non-essential elements or features have been omitted for clarity.

[0018] Figure 1 This is a flowchart of the concrete flow control method in an embodiment of the present invention; Figure 2 A flowchart illustrating the method for establishing the mapping relationship between valve opening degree and remaining material mass and instantaneous mass flow rate in an embodiment of the present invention; Figure 3 This is a graph showing the measured mass flow rate versus time under various valve opening conditions in embodiments of the present invention. Figure 4 This is a graph showing the instantaneous mass flow rate changing over time in an embodiment of the present invention; Figure 5 This is an example diagram illustrating the application of the automated foamed concrete preparation system in this invention. Figure 6 This is a three-dimensional schematic diagram of the structure of the automated foamed concrete preparation system in an embodiment of the present invention; Figure 7 This is a top view schematic diagram of the structure of the automated foamed concrete preparation system in an embodiment of the present invention; Figure 8 This is a schematic diagram of the mixer structure in an embodiment of the present invention; Figure 9 This is a schematic diagram of the foam generator functional modules in an embodiment of the present invention; Figure 10 This is a flowchart illustrating the coordinated control method of slurry and foam in an automated foam concrete preparation system according to an embodiment of the present invention. Figure 11 This is a graph showing the relationship between the frequency of the foam generator liquid pump motor and the corresponding foaming agent flow rate in an embodiment of the present invention. Figure 12 This is a graph showing the relationship between the frequency of the air pump motor of the foam generator and the corresponding air flow rate in an embodiment of the present invention. Figure 13 This is a curve showing the relationship between the amount of foamed concrete transported and the motor frequency in an embodiment of the present invention. Figure 14 The figure shows the experimental verification results of concrete flow control when the target flow rate is 12T / h. Figure 15 The figure shows the experimental verification results of concrete flow control when the target flow rate is 6.4 T / h. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] In this invention, terms such as "upper," "lower," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely relational terms determined for the convenience of describing the structural relationship of the various components or elements of this invention, and do not specifically refer to any component or element in this invention, and should not be construed as limiting this invention.

[0023] In this invention, terms such as "connection" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of the above terms in this invention based on the specific circumstances, and they should not be construed as limitations on this invention.

[0024] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0025] This invention provides a concrete flow control method applicable to the conveying process in concrete engineering, including on-site pouring in building construction, factory production of precast components, integrated preparation and conveying of special concrete (such as on-site preparation and continuous conveying of foamed concrete), and temporary transfer scenarios. This method focuses on the flow control of a concrete metering tank. By real-time acquisition of the material weight inside the tank and dynamic adjustment of the outlet valve opening, the output flow rate of concrete in the metering tank is controlled. This ensures that the flow rate of concrete flowing out of the metering tank matches the terminal operation rhythm and material performance requirements, effectively avoiding problems such as material accumulation, waste, operation interruption, or uneven quality caused by flow fluctuations. This provides technical support for stable and efficient operation in various concrete engineering conveying processes.

[0026] Specifically, the method is applied to a concrete conveying system, which includes a concrete metering tank and a controller. A controllable valve assembly is installed at the outlet of the metering tank, and a weight sensor is located below the metering tank. The controllable valve assembly is connected to the controller, and the method is applied to the controller, such as... Figure 1 As shown, it includes the following steps: S101, Receive the set target traffic; S102. Real-time reception of the weight of the measuring tank; S103. Using the target flow rate as the instantaneous mass flow rate and the weight of the metering tank as the remaining material mass, the target valve opening is determined based on the mapping relationship between the valve opening, the remaining material mass, and the instantaneous mass flow rate, and the opening control is performed on the controllable valve assembly.

[0027] The above method establishes a mapping relationship between valve opening and the mass of remaining material and instantaneous mass flow rate. By combining the target flow rate and the real-time weight of the metering tank to determine the valve opening, it can accurately control the discharge flow rate and avoid errors caused by manual control. At the same time, by adjusting the valve opening based on the mass of remaining material, it can cope with flow fluctuations caused by changes in the material level in the tank, thereby maintaining a stable flow rate during the pouring process.

[0028] In addition, the above method also solves the problem of hydrostatic pressure changes caused by the drop in material level in the tank. By adjusting the opening degree in relation to the remaining material mass, dynamic compensation of flow rate is achieved, avoiding the natural decrease in flow rate during the pouring process and ensuring the uniformity of pouring.

[0029] The concrete metering tank is used to contain concrete slurry and includes a discharge port. Exemplarily, it is a cylindrical container with a capacity of approximately 0.35 m³, supported by three legs, each equipped with a weight sensor for real-time measurement using the weight loss method. During operation, the three weight sensors provide analog signals of 4-20 mA to the PLC's analog input module. The PLC sums these signals to obtain the real-time total weight of the tank and its internal materials. By calculating the rate of change of weight, the slurry mass flow rate can be accurately characterized. Compared to volumetric measurement, this method is unaffected by changes in material density, resulting in higher measurement accuracy, and is particularly suitable for metering concrete slurry with large density fluctuations, such as those found in coal-fired ash-based materials.

[0030] In step S103, such as Figure 2 As shown, the method for establishing the mapping relationship between the valve opening degree and the remaining material mass, instantaneous mass, and flow rate is as follows: S1031. Obtain data on the change of outflow quality over time under multiple opening conditions.

[0031] Data acquisition was achieved using a combination of CFD simulation and experimental calibration. Specifically, the cumulative outflow mass-time curve of foamed concrete with a specific mix proportion under known valve openings was first collected using a miniaturized experimental platform. This was used to calibrate the rheological parameters (yield stress τ0, consistency coefficient k, and power-law exponent n) in the CFD simulation model. Then, based on the calibrated rheological parameters, a complete transient CFD simulation of multiple discrete valve openings was performed on a full-size industrial mixing tank. The simulation started at a full tank, and the complete data of the cumulative outflow mass changing over time under each opening condition was recorded in real time, forming a flow field database. For example, to obtain "ground-based" data for calibrating the CFD simulation, a basic experiment was first conducted on a miniaturized experimental platform. Foamed concrete with a specific mix proportion (density approximately 1600 kg / m³) was added to the experimental tank. The outlet valve was fixed at a known opening, for example, 80 mm. The valve was opened, allowing the concrete to flow out naturally under gravity. Simultaneously, a high-frequency data acquisition system was used to collect readings from the weight sensor, and a precise cumulative outflow mass-time curve was obtained. This curve is the cornerstone of the accuracy of subsequent simulation models.

[0032] A three-dimensional fluid domain model with a geometry identical to the experimental platform was established on a CFD simulation platform, and high-quality mesh generation was performed. In CFD software (such as ANSYS Fluent), concrete was defined as a non-Newtonian fluid, and the Herschel-Bulkley constitutive model, which describes its yield-shear thinning characteristics, was selected. The mathematical expression of this model is: τ=τ0+k×γ˙ n Where τ is the shear stress, γ˙ is the shear rate, τ0 is the yield stress, k is the consistency coefficient, and n is the power law exponent.

[0033] Initially, estimated values ​​were set for τ0, k, and n. A transient simulation with the same boundary conditions as the physical experiment (i.e., valve opening of 80 mm) was run. After the simulation, the cumulative outflow mass-time curve obtained from the simulation was extracted and compared with the measured experimental curve. By repeatedly adjusting the values ​​of τ0, k, and n and re-running the simulation, optimization algorithms (such as the least squares method) were used to minimize the error between the simulation curve and the experimental curve. In this embodiment, the optimal rheological parameters finally identified were: yield stress τ(0) = 24 Pa, consistency coefficient k = 92.24, and power law exponent n = 0.9.

[0034] For example, for full-size industrial mixing tanks (3 m 3A series of CFD simulations were conducted to fully cover the equipment's operating range, encompassing multiple discrete valve openings from 30 mm to 150 mm, with a step size of 10 mm. For each opening condition, a complete transient simulation was performed, recording the cumulative outflow mass change over time from a full tank state. After completing this series of simulations, a high-precision flow field database containing 13 sets of different operating conditions was obtained.

[0035] S1032. Determine the data on the change of the mass of the remaining material over time under multiple opening conditions based on the initial total mass of the mixing tank.

[0036] The difference between the initial total mass of the mixing tank and the cumulative outflow mass at different times under each set of opening conditions is calculated to obtain the mass of the remaining material in the tank at each time. Then, a data correspondence relationship between the mass of the remaining material and time under multiple sets of opening conditions is established. Figure 3 It is a graph showing the change of measured mass flow rate over time under multiple valve opening conditions.

[0037] S1033. Perform curve fitting on the outflow quality data over time under each set of opening conditions to obtain multiple cumulative outflow quality functions.

[0038] Import the cumulative outflow mass-time data corresponding to each valve opening in the flow field database into the data processing software, and select the exponential function Mass(t) = C + A·exp( The data is fitted using a curve (t / B), where Mass(t) is the cumulative outflow mass at time t, and A, B, and C are the fitting parameters. The specific values ​​of A, B, and C for each opening condition are determined through fitting calculations, thus obtaining the cumulative outflow mass function for the corresponding opening.

[0039] S1034. Differentiate each cumulative outflow mass function to obtain multiple instantaneous mass flow functions.

[0040] For each set of opening conditions, the first derivative of the cumulative outflow mass function Mass(t) fitted with respect to time t is obtained, and the instantaneous mass flow rate function FlowRate(t) is obtained through differentiation. (A / B)·exp( t / B), complete the conversion of cumulative outflow quality data into instantaneous quality flow data, and obtain the instantaneous quality flow at different times under each opening degree. Figure 4 It is a graph showing the instantaneous mass flow rate changing over time.

[0041] S1035. Based on the remaining material mass and instantaneous mass flow rate at each moment under the multiple opening conditions, establish a mapping relationship between valve opening and remaining material mass and instantaneous mass flow rate.

[0042] By integrating valve opening, remaining material mass, and instantaneous mass flow rate data at various times under all opening conditions, a mapping model is constructed between valve opening, remaining material mass, and instantaneous mass flow rate: Valve opening = f(remaining material mass, target flow rate). This model can be in the form of a three-dimensional lookup table or a multivariate function. After construction, an arbitrary target flow rate value must be input to verify the effectiveness of the "remaining material mass - valve opening" control curve output by the model in ensuring flow stability, ensuring the mapping relationship is accurate and reliable.

[0043] When the operator inputs a target flow rate (e.g., 12.5 T / h), the model can output a two-dimensional "quality-opening" control curve, which is the direct basis for PLC execution control.

[0044] The aforementioned model construction method pre-solves complex physical problems through extensive offline calculations, simplifying complex fluid dynamics issues into deterministic control graphs. This makes online control tasks simple and efficient, requiring only table lookups or simple function calculations, ensuring the system's real-time performance and reliability. Furthermore, the model accurately describes the non-Newtonian rheological properties of concrete and the dynamic changes in hydrostatic pressure as material decreases, achieving extremely high control precision. Experimental verification shows that under steady-state conditions, the error between the actual flow rate and the target flow rate can be controlled within 1.75%; even under complex conditions of simultaneous feeding and discharging, the maximum error does not exceed 5.1%.

[0045] After obtaining the "quality-opening" control curve, the control curve is programmed into the PLC program in the form of a piecewise function or lookup table. After the PLC is powered on, it executes a high-speed cyclic scanning program, which sequentially calculates the target opening degree in each millisecond-level scanning cycle. Then, through the motion control function block, the opening setpoint is converted into the absolute position of the servo motor and the corresponding number of pulses. The pulse sequence and direction signal are sent to the servo driver, and finally the servo driver drives the servo motor to rotate and adjusts the valve to the target opening degree through the electric cylinder. This process is repeated continuously. As the concrete flows out of the tank and the weight sensor reading decreases, the PLC will continuously query the model and fine-tune the valve opening degree (usually gradually increasing it to compensate for the decrease in hydrostatic pressure), forming a dynamic and precise closed-loop control to ensure that the outlet flow rate is highly constant throughout the entire pouring process.

[0046] The above-mentioned flow control method is not only applicable to foamed concrete, but can also be extended to any other viscous fluid with complex rheological properties, demonstrating strong technical scalability.

[0047] The aforementioned concrete flow control method not only solves the flow fluctuation problem in traditional concrete pouring, but can also be further extended to the preparation of foamed concrete, where higher precision in material proportioning is required, achieving accurate proportioning of concrete slurry and foam. Specifically, one or more embodiments of the present invention provide an automated foamed concrete preparation system. Figure 5 This diagram illustrates an application example of the automated foamed concrete preparation system. Raw materials (such as sand and gravel) are transported from the concrete mixing plant by concrete trucks and fed into a vibrating screen for preliminary processing. The processed material enters a metering tank, where a weight sensor collects the material's weight, and the data is transmitted to a controller. The controller regulates the feed through an electric valve, causing the metering tank to output a fixed amount of concrete, while simultaneously controlling a foam generator to produce foam. The foam and the quantitatively output concrete are mixed in a spiral mixing device. The resulting foamed concrete is then conveyed under high pressure by a high-pressure pump through a mixing and conveying equipment, completing the production process.

[0048] This automated foamed concrete preparation system includes a concrete metering tank 1, a programmable foam generator 2, a mixer 3, and a controller 4. The mixer 3 has two inlets at its input end, which are connected to the outlets of the concrete metering tank 1 and the programmable foam generator 2, respectively. A controllable valve assembly is installed at the outlet of the concrete metering tank 1. Both the controllable valve assembly and the programmable foam generator 2 are connected to the controller. A weight sensor is also installed below the concrete metering tank 1. Figure 10 As shown, the controller is configured as follows: S201, Receive the target density and set target flow rate of the foamed concrete product; S202. Receive the weight of the metering tank in real time and calculate the real-time weight change rate; S203. Using the target flow rate as the instantaneous mass flow rate and the weight of the metering tank as the remaining material mass, based on the mapping relationship between the valve opening and the remaining material mass and the instantaneous mass flow rate, determine the target valve opening and perform opening control on the controllable valve assembly. S204. Calculate the actual mass flow rate of the slurry based on the real-time weight change rate. S205. Based on the actual mass flow rate and target density of the slurry, calculate the required foam volume flow rate, control the foam generator to produce and inject the corresponding amount of foam into the mixer.

[0049] Based on the above concrete flow control method, the output flow of slurry can be stabilized, and the foam flow can be controlled based on the target density and the actual flow, ensuring accurate slurry-to-foam ratio and guaranteeing that the density of the final foamed concrete product meets the target requirements. The above method can realize the automated control of foamed concrete preparation without relying on manual experience for adjustment, thus improving the automation level of the preparation process.

[0050] For example, the concrete metering tank 1, the manual control console (integrated HMI control panel), the programmable foam generator 2, and the mixer 3 are all fixedly installed on the support frame (platform base frame) by bolts and other connectors, forming a stable connection between each component and the frame, constituting an integrated automated preparation equipment. The concrete metering tank 1 is connected to the frame by three support legs; the programmable foam generator 2 is installed on the support frame near the concrete metering tank 1, belonging to the upstream area along with the metering module; the mixer 3 is horizontally installed in the middle area of ​​the support frame, downstream of the metering module and the foam generation module; the PLC, as the central control unit, is installed in the electrical control cabinet 4 on the support frame, and the electrical control cabinet 4 is close to the manual operation area; the manual control console 5 is located at the edge of the support frame, and integrates the HMI control panel on it.

[0051] The concrete metering tank 1 is used to contain concrete slurry, and a discharge port is provided at the bottom of the tank. Exemplarily, it is a cylindrical container with a capacity of approximately 0.35 m³, supported by three legs, each equipped with a weight sensor for weight loss measurement. During operation, the three weight sensors provide analog signals of 4-20 mA to the PLC's analog input module. The PLC sums these signals to obtain the real-time total weight of the tank and its internal materials. By calculating the rate of weight change, the slurry mass flow rate can be accurately determined. Compared to volumetric measurement, this method is unaffected by changes in material density, resulting in higher measurement accuracy, and is particularly suitable for metering concrete slurry with unstable density, such as slag-based slurry.

[0052] A controllable valve assembly, which is a sliding plate valve, is located at the discharge port. This type of valve has an actuator thrust exceeding 1200N, capable of shearing potentially clogging aggregates, ensuring operational reliability, and effectively resisting jamming by large aggregates, thus adapting to the conveying needs of special slurries such as slag concrete. The valve is driven by an electric push rod, which incorporates a servo motor, synchronous belt, and ball screw mechanism, enabling high-precision and repeatable control of the valve's linear position (i.e., orifice size).

[0053] Programmable foam generator 2, used to produce foam at a variable output rate. For example... Figure 9As shown, the foam generator includes a liquid pump (such as a three-plunger pump), an air pump (or connected to a compressed air source), and a mixing chamber containing porous media. After diluted foaming agent and air are introduced into the mixing chamber, fine and stable foam is generated. Its control terminal is connected to a PLC. The motors of both the liquid and air pumps are driven by frequency converters. By adjusting the output frequency of the frequency converters, the PLC can independently and precisely control the flow rates of liquid and air. This not only dynamically regulates the total foam production but also precisely controls the gas-liquid ratio within the optimal range of 20:1 to 24:1, ensuring foam stability. Furthermore, an electrically controlled shut-off valve is installed in the air pipeline. Upon receiving a stop signal from the PLC, it immediately shuts off the air source, achieving instantaneous cessation of foam production and preventing foam overflow due to residual pressure in the pipeline, thus adapting to the intermittent operation requirements of the construction site. An electrically controlled valve is also installed in the air pipeline. When the PLC issues a stop command, this valve closes, cutting off the air source and stopping foam generation. This prevents unnecessary foam overflow due to residual pressure in the pipeline.

[0054] Mixer 3 is a spiral mixer, precisely positioned to align with the discharge ends of the concrete metering tank 1 and the foam generator 2. It simultaneously receives concrete slurry from the metering tank and foam from the foam generator. While ensuring thorough mixing of the slurry and foam, it also synchronously delivers the generated foamed concrete to downstream pumping equipment (such as a high-pressure pump), providing homogeneous finished material for subsequent pouring operations. The discharge port of the concrete metering tank corresponds to the inlet of the spiral mixer, and the slurry, regulated by a controllable valve assembly, is directly conveyed to the spiral mixer. The foaming outlet of the programmable foam generator faces the spiral mixer, and the generated foam is synchronously conveyed into the spiral mixer, where it is uniformly mixed with the slurry. The discharge end of the spiral mixer can be connected to downstream equipment such as a high-pressure pump, depending on production needs, to facilitate the subsequent delivery of the foamed concrete.

[0055] For example, such as Figure 8 As shown, the mixer 3 includes a pipe body 6, with a raw material inlet 7 at one end, which includes a slurry inlet and a foam inlet, and a foamed concrete outlet at the other end. Inside the pipe body, along its central axis, is a spiral shaft 8, which is divided into two ends: a mixing section 9 near the raw material inlet and a transmission section 10 near the outlet. The mixing section uses three-bladed blades, while the transmission section uses continuous threaded blades.

[0056] The slurry enters pipe 6 through the slurry inlet, while foam is injected into pipe 6 through the foam inlet. The auger shaft drives the blades of mixing section 9 to further mix the slurry and foam through rotational shearing, refining the bubbles and ensuring uniform distribution. After thorough mixing, the foamed concrete enters the conveying section 10 and is propelled forward by the blades of the auger conveying section 10, finally exiting from the outlet. On the one hand, the eddies and turbulence generated by the rotation of the blades of mixing section 9 can forcibly mix the slurry and foam, ensuring uniform bubble dispersion and improving product density consistency and mechanical properties. On the other hand, the blades of mixing section 9 also have shearing and anti-settling functions, preventing aggregate settling and stratification during the mixing process, adapting to the mixing requirements of special materials such as foamed concrete. The continuous spiral blades of conveying section 10 can achieve smooth and continuous material delivery, avoiding material stagnation or conveying blockage. Combined with the efficient mixing of mixing section 9, it realizes the integration of mixing and conveying, improving the continuity and stability of the overall preparation process. The three-bladed blades and spiral blades are connected to the auger shaft 8 by welding, which can resist the abrasion of the foamed concrete slurry and extend the service life of the mixer.

[0057] A programmable logic controller (PLC) is communicatively connected to the weight sensor, the controllable valve servo motor driver, and the programmable foam generator 2. It receives real-time weight signals from the weight sensor, calculates the slurry mass flow rate, determines the target valve opening based on a preset mapping relationship, and drives the servo motor to precisely adjust the valve. It independently adjusts the motor frequencies of the air pump and liquid pump in the foam generator to control foam production and the gas-liquid ratio. It sends a stop signal to the electrically controlled shut-off valve of the foam generator to achieve clean foam termination. In actual operation, after the operator inputs the target density through the human-machine interface (HMI), the PLC can initiate fully automated control, ensuring coordinated operation of all equipment. The PLC is also connected to a manual control panel 5, which is equipped with control modules for adjusting valve opening, foaming machine speed, and spiral mixing speed. For example, valve opening knobs, foaming machine speed control knobs, and spiral mixing speed control knobs can be installed on the manual control panel 5.

[0058] The method for determining the target valve opening degree and performing opening degree control on the controllable valve assembly in steps S201 and S203 is described in steps S101-S103.

[0059] In step S205, the required foam volume flow rate is calculated based on the actual mass flow rate and target density of the slurry. The specific method is as follows: obtain the slurry density and the target density of the foamed concrete, and calculate the ideal foam volume flow rate required for the current actual mass flow rate based on the principle that the sum of the slurry volume and the foam volume equals the total volume of the foamed concrete; and calculate the required actual foam volume flow rate based on the ideal foam volume flow rate and the foam breaking rate.

[0060] Let the real-time actual concrete mass flow rate be... The required foam volumetric flow rate is The density of the concrete slurry is The target density of foamed concrete is Under ideal conditions, neglecting the weight of the foam itself and assuming no foam breakage after mixing, the related equations can be derived using the principle of volume conservation, where the total volume V of the foamed concrete equals the sum of the original concrete volume and the foam volume: ; Considering that foam breaking inevitably occurs during the mixing process in actual production, a foam breaking rate η needs to be introduced to correct the ideal value. After correction, the foam volumetric flow rate that meets the actual production requirements is obtained. .

[0061] .

[0062] In step S205, after calculating the required foam volumetric flow rate, this flow rate requirement needs to be converted into specific operating parameters for the air pump and liquid pump of the foaming machine to control the foam generator's production and inject the corresponding amount of foam into the mixer. As one implementation method, since the foam output of the foaming machine is directly determined by the air flow rate delivered by the air pump and the foaming agent flow rate delivered by the liquid pump, and both flow rates have a clear correspondence with their respective motor frequencies, it is necessary to determine the mapping relationship between the foam volumetric flow rate and the motor frequencies of the air pump and liquid pump through calibration tests, and determine the frequency control parameters of the air pump and liquid pump motors based on the required foam volumetric flow rate.

[0063] For example, the calibration method is as follows: first, determine the mapping relationship between the liquid pump flow rate and the liquid pump motor frequency, and between the air pump flow rate and the air pump motor frequency through calibration tests, such as... Figure 11 and Figure 12Then, by setting different combinations of air pump and liquid pump motor frequencies, the corresponding total foam flow rate and gas-liquid ratio are calculated, and a calibration parameter table that meets the gas-liquid ratio requirements is established. The calibration parameter table includes the mapping relationship between foam volumetric flow rate and air pump and liquid pump motor frequencies. Specifically, the preliminary work is first completed, checking the sealing of the air and liquid circuits of the foaming machine, and ensuring that measuring equipment such as flow meters and pressure gauges are working properly. Then, calibration experiments are carried out in stages: For the liquid pump, the foam outlet and liquid pump are turned on, the liquid pump motor frequency is set and adjusted in 5Hz interval gradients, the flow meter data is read at each frequency and repeated 5 times to take the average value, the actual flow rate of the liquid pump corresponding to different frequencies is recorded, the data is imported into the processing software for linear fitting, and the correlation formula between the liquid pump flow rate and the motor frequency is obtained; For the air pump, because the air flow rate is large, the air pump motor frequency is adjusted in 2Hz interval gradients, and the remaining operations are the same as the liquid pump calibration, the actual flow rate of the air pump corresponding to different frequencies is recorded and linear fitting is completed to obtain the correlation formula between the air pump flow rate and the motor frequency. Based on the above two sets of correlation formulas, the corresponding total foam flow rate and gas-liquid ratio can be calculated by setting different combinations of air pump and liquid pump motor frequencies. Furthermore, through multiple frequency combination experiments and combined with foam stability test results, the motor frequency parameters that meet the preferred range of 20:1 to 24:1 for different foam flow rate requirements are finally calibrated, and the calibration parameter table is stored in the PLC to provide a basis for subsequent precise control.

[0064] When the system starts up, to ensure that the foam flows through the outlet pipe and enters the mixer hopper simultaneously with the concrete material, the foam generator is first controlled to generate and transport foam before the material feeding operation is performed. For example, the unit delay time for foam to be transported from the generator outlet to the mixer hopper via the pipe is pre-calibrated experimentally and preset in the PLC control program. When the system receives the start command, the PLC first sends a start signal to the programmable foam generator, controlling its air pump and liquid pump to start at the calibrated frequency, and foam begins to be generated and transported along the pipe. Simultaneously, the PLC starts a timer internally. When the timer reaches the preset delay time, the controllable valve assembly is opened to prevent excessive local foam or slurry concentration due to timing deviations, thus improving the uniformity of foam mixing.

[0065] The method further includes step S206: controlling the operating frequency of the mixer motor based on the relationship between the mass flow rate of foamed concrete and the frequency of the mixer motor. Specifically, firstly, the curve relationship between the mixer motor frequency and the average mass flow rate of foamed concrete is calibrated through offline experiments, and the curve is linearly fitted into a correlation formula to clarify the output of foamed concrete corresponding to different motor frequencies. Figure 13 The curve showing the relationship between the volume of foamed concrete transported and the motor frequency is fitted with the following formula: ; Where x is the motor frequency and y is the amount of foamed concrete transported.

[0066] The fitted formula or curve data is stored in the PLC as the control basis. During real-time operation, the PLC first calculates the real-time mass flow rate of the foamed concrete. Ignoring the weight of the foam itself, the real-time mass flow rate of the foamed concrete is equal to the real-time mass flow rate of the concrete slurry. Then, the PLC calls the pre-stored correlation formula or curve data, using the real-time mass flow rate of the foamed concrete as input, and reversely derives the target frequency of the matching mixer motor. Finally, the PLC sends a frequency control signal to the mixer motor driver, driving the motor to run at the target frequency. This ensures that the mixer's transport capacity matches the amount of foamed concrete generated in real time, avoiding excessively fast material transport and insufficient mixing due to excessively high frequency, while also preventing material stagnation and accumulation in the mixer due to excessively low frequency, thus ensuring the continuity and stability of foamed concrete preparation.

[0067] Example 1: Constant Flow Control A batch with an average density of 1612 kg / m³ 3 The slag-based concrete was loaded into the metering tank. The target flow rate was set to 12T / h on the HMI, and the system was started. The PLC monitored the rate of weight loss and dynamically adjusted the position of the slide valve.

[0068] like Figure 14 As shown, the system achieved a stable average flow rate of 11.73 T / h, with a deviation of only 1.82% from the set value.

[0069] To simulate more complex situations closer to actual construction (e.g., new concrete being added to the mixing tank during pouring), dynamic tests were conducted with simultaneous material feeding and discharging. The target flow rate was set at 4 m³ / h (approximately 6.4 T / h). During the test, the system not only had to adjust the valves according to the decrease in material but also had to adapt to sudden increases in material mass due to material feeding. Segmented analysis was performed on the flow rate data at different stages during the test, such as... Figure 15 As shown, even under such dynamically changing operating conditions, the system still exhibits good robustness, with the maximum error between the actual flow rate and the target flow rate at each stage controlled within 5.1%. This fully demonstrates that the control method of the present invention is not only highly accurate but also has a strong adaptability to changes in operating conditions, fully meeting the requirements of industrial applications.

[0070] Example 2: Foam Generator Optimization and Control The programmable foam generator was tested by varying the motor frequencies of the air and liquid pumps to obtain different air-liquid ratios. Its stability was evaluated by measuring the foam's defoaming and breaking rate over 120 minutes.

[0071] As shown in Table 1, the experiment found that a gas-liquid ratio of 22:1 was the optimal ratio, producing foam with an initial density of 23.31 g / L and a foam breakage rate of less than 43% after 120 minutes. This optimal ratio was subsequently programmed as the default setting for the PLC.

[0072] Table 1 Relationship between foam stability and gas-liquid ratio

[0073] Example 3: System Integration and Performance The entire system was run using the parameters determined in Examples 1 and 2. The target density of the final foamed concrete was set at 850 kg / m³. 3 The motor frequency of the spiral mixer is set to 50 Hz.

[0074] The system produces foamed concrete at a continuous rate of 25.1 T / h. Density measurements of the produced sample showed a density of approximately 850 kg / m³. 3 The target value deviation is less than ±5%, which is significantly improved in terms of quality consistency compared to the ±15% deviation commonly seen in traditional methods.

[0075] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0076] The scope of protection of this invention is defined only by the claims. Thanks to the teachings of this invention, those skilled in the art will readily recognize that alternative structures to the structures disclosed herein can be used as feasible alternative implementations, and that the implementations disclosed herein can be combined to produce new implementations, which also fall within the scope of the appended claims.

Claims

1. A method of controlling the flow of concrete for use in a concrete delivery system, said system comprising a concrete metering tank and a controller, said metering tank having a controllable valve assembly at its discharge outlet, said controllable valve assembly being connected to the controller, characterised in that, A weight sensor is located below the metering tank; the method is applied to the controller and includes the following steps: Receive the set target traffic; Real-time reception of the metering tank weight; The target flow rate is taken as the instantaneous mass flow rate, and the weight of the metering tank is taken as the mass of the remaining material. Based on the mapping relationship between the valve opening, the mass of the remaining material, and the instantaneous mass flow rate, the target valve opening is determined and the opening control is performed on the controllable valve assembly.

2. The concrete flow control method as claimed in claim 1, wherein, The method for establishing the mapping relationship between the valve opening degree and the remaining material mass and instantaneous mass flow rate is as follows: Acquire data on the change of outflow quality over time under multiple opening conditions; Based on the initial total mass of the mixing tank, determine the data on the change of the mass of the remaining material over time under multiple opening conditions; Curve fitting was performed on the outflow mass change data over time under each set of opening conditions to obtain multiple cumulative outflow mass functions; Differentiating each cumulative outflow mass function yields multiple instantaneous mass flow functions; Based on the remaining material mass and instantaneous mass flow rate at each moment under the multiple opening conditions, a mapping relationship between valve opening and remaining material mass and instantaneous mass flow rate is established.

3. The method of claim 2, wherein, The mapping relationship between valve opening degree and remaining material mass and instantaneous mass flow rate is in the form of a three-dimensional lookup table or a multivariate function.

4. The concrete flow control method as described in claim 1, characterized in that, The metering tank is equipped with multiple support legs, and each support leg is equipped with a weight sensor.

5. The concrete flow control method as described in claim 1, characterized in that, The controllable valve assembly is a slide valve.

6. An automated foamed concrete preparation system, comprising a concrete metering tank, a programmable foam generator, a mixer, and a controller, wherein, The mixer has two inlets at its input end, which are respectively connected to the outlets of a concrete metering tank and a programmable foam generator; a controllable valve assembly is provided at the outlet of the concrete metering tank; the controllable valve assembly and the programmable foam generator are both connected to a controller; a weight sensor is also provided below the concrete metering tank; the controller is configured to perform opening control on the controllable valve assembly based on the concrete flow control method as described in any one of claims 1-5. Target density for receiving foamed concrete products; Calculate the real-time weight change rate based on the real-time weight of the metering tank; The actual mass flow rate of the slurry is calculated based on the real-time weight change rate. Based on the actual mass flow rate and target density of the slurry, calculate the required foam volume flow rate, control the foam generator to produce and inject the corresponding amount of foam into the mixer.

7. The automated foamed concrete preparation system as described in claim 6, characterized in that, The mixer includes a tube body with two inlets at one end for feeding slurry and foam respectively, and a foam concrete outlet at the other end. Inside the tube body, a spiral shaft is provided along the central axis of the tube body. The spiral shaft is divided into two sections: a mixing section near the raw material inlet and a transmission section near the outlet. The blades of the mixing section are three-bladed, and the blades of the transmission section are continuous spiral blades.

8. The automated foamed concrete preparation system as described in claim 6, characterized in that, The calculation of the required foam volume flow rate based on the actual mass flow rate and target density of the slurry includes: obtaining the slurry density and the target density of the foamed concrete; calculating the ideal foam volume flow rate required for the current actual mass flow rate based on the principle that the sum of the slurry volume and the foam volume equals the total volume of the foamed concrete; and calculating the required actual foam volume flow rate based on the ideal foam volume flow rate and the foam breaking rate.

9. The automated foamed concrete preparation system as described in claim 6, characterized in that, Controlling the foam generator to produce and inject the appropriate amount of foam into the mixer includes: determining the frequency control parameters of the air pump and liquid pump motors based on the pre-calibrated mapping relationship between the foam volume flow rate and the frequency of the air pump and liquid pump motors, according to the required foam volume flow rate.

10. The automated foamed concrete preparation system as described in claim 6, characterized in that, The method further includes: controlling the operating frequency of the mixer motor based on the relationship between the mass flow rate of foamed concrete and the frequency of the mixer motor.

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