A system and control strategy for generating large water droplets

Abstract

The application belongs to the technical field of fluid control and atomization, and relates to a system for generating large water droplets, in particular to a master control system, a liquid supply system, a generating system and an auxiliary system; the generating system comprises a water storage tank, a perforated steel sheet arranged at the bottom of the water storage tank, a tapered micro-hole formed in the perforated steel sheet, a piezoelectric transducer fixed at the bottom of the perforated steel sheet, a copper heat equalizing plate arranged at the top of the water storage tank and an electric heating layer mounted on the copper heat equalizing plate. Since the existing annular transducer technical solution cannot meet the demand of single water droplet or multiple water droplet generation and cannot meet the requirement of accurately controllable water droplet size, a rectangular transducer is used as an excitation device in the application, surface waves are superimposed by transducer vibration, the water level of the water storage tank is controllable in the application, a high-temperature pulse is applied to the air layer on the upper surface of the water layer, the pressure in the water tank during spraying is controllable, and the problem that the water droplet diameters are inconsistent due to uncontrollable pressure is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fluid control and atomization, in particular to a system and control strategy for generating large water droplets, which is suitable for applications such as icing wind tunnel and water droplet dynamics research that require the generation of single or multiple large water droplets. BACKGROUND

[0002] Currently, traditional water droplet generators are mainly used to generate small droplets, such as humidifiers and medical atomizers, etc. The water droplets generated by these devices are usually small (diameter of 5-50 microns) and can only generate multiple water droplets, which are not suitable for the fields of supercooled large water droplet dynamics and supercooled large water droplet icing. For these application scenarios, the diameter of the water droplets needs to reach hundreds of microns or even larger.

[0003] However, the existing large water droplet generation devices based on piezoelectric spraying all use ring-shaped piezoelectric materials, which produce multiple continuous large water droplets during a single excitation. Currently, there is no water droplet generation device or system that can produce multiple large water droplets and single large water droplets. In addition, the ring-shaped transducer cannot meet the demand of the water droplet generator to produce single or multiple large water droplets at the same time. The main reason is that the liquid viscosity will cause the water droplets to be unable to timely detach from the water hole when the steel sheet is deformed and extruded. Moreover, another technical solution adopted by existing small-sized water droplet generators is to use a gas-liquid mixed method. Due to the high gas and water pressure and the inability to accurately control it, multiple water droplets are sprayed from the liquid outlet at the same time, and the size of the water droplets cannot be controlled. Finally, the sticking position, excitation frequency and excitation voltage of the ring-shaped transducer used in the existing technology will cause the size of the liquid droplets to change, and the inaccurate opening position will also cause no water droplets to be generated during excitation.

[0004] Therefore, there is a need for a device based on piezoelectric atomization principle and suitable for single / multiple large water droplet generation. SUMMARY

[0005] The present application aims to solve one of the technical problems existing in the prior art or related art.

[0006] To this end, the technical solution adopted by the present application is as follows:

[0007] A system for generating large water droplets, comprising: a master control system, a liquid supply system, a generating system and an auxiliary system; the generating system comprises a water storage tank, a perforated steel sheet arranged at the bottom of the water storage tank, a tapered micro-hole opened on the perforated steel sheet, a piezoelectric transducer fixed at the bottom of the perforated steel sheet, a copper plate arranged at the top of the water storage tank, an electric heating layer mounted on the copper plate and a temperature sensor arranged in the electric heating layer; the auxiliary system comprises a water droplet monitoring module, a vibration compensation module and a dynamic pressure adjustment module; an air layer is left at the upper part of the water storage tank, the bottom of the air layer is at the same horizontal line with the liquid level sensor; the piezoelectric transducer is provided with at least two groups of symmetrical groups at the bottom of the perforated steel sheet.

[0008] In a preferred example, the liquid supply system comprises a liquid supply module, a water inlet pipe connected between the water storage tank and the liquid supply module, a water outlet pipe connected to the water storage tank and a liquid level sensor arranged on the water outlet pipe.

[0009] In a preferred example, the water droplet monitoring module comprises a high-speed camera and an image processing unit connected thereto.

[0010] The high-speed camera is arranged at the bottom of the water storage tank and is used for capturing the size and motion trajectory of the water droplets emitted by the tapered micro-hole in real time.

[0011] The image processing unit is integrated in the master control system and adjusts the excitation parameters of the piezoelectric transducer by analyzing the water droplet image feedback.

[0012] In a preferred example, the vibration compensation module comprises a vibration sensor and a reverse vibration generator.

[0013] The vibration sensor is mounted on the side edge of the perforated steel sheet and is used for detecting the asymmetric vibration generated when the piezoelectric transducer is excited.

[0014] The reverse vibration generator is fixed to the outer wall of the water storage tank and offsets the vibration interference of the perforated steel sheet by generating reverse vibration waves.

[0015] In a preferred example, the dynamic pressure adjustment module comprises an air pressure regulating valve and a pressure sensor.

[0016] The pressure sensor is embedded in the air layer of the water storage tank and is used for monitoring the pressure change of the air layer in real time.

[0017] The air pressure regulating valve is connected with the master control system and dynamically adjusts the pressure of the air layer according to the feedback of the pressure sensor, so as to maintain the constant liquid surface pressure.

[0018] The application can be further configured in a preferred example as follows: the auxiliary system further comprises a micropore cleaning module, the micropore cleaning module comprises a rotating device arranged at the bottom of the water storage tank, an air pump mounted on the rotating device, a fixing frame fixed to the side of the rotating device, and a cleaning nozzle connected to the air pump through a pipeline and mounted on the fixing frame.

[0019] The application can be further configured in a preferred example as follows: the image processing unit calculates the water droplet diameter through an edge detection algorithm, compares the water droplet diameter with a preset target diameter, and generates a pulse amplitude correction signal.

[0020] The trajectory tracking algorithm is also used to predict the water droplet landing point deviation, and an excitation timing adjustment signal of the piezoelectric transducer is generated.

[0021] The application can be further configured in a preferred example as follows: the following control strategies are further included.

[0022] First, the main control system is turned on, and the liquid supply module automatically inputs deionized water into the water storage tank until the liquid level reaches the position of the water outlet liquid level sensor, and then the liquid supply is stopped.

[0023] When a single water droplet generation starts, the electric heating layer is powered first, and the power supply is stopped when the temperature sensor feedback temperature reaches the preset value.

[0024] The piezoelectric transducer is excited immediately after the electric heating is stopped, and the piezoelectric transducer excitation is set to single pulse or multi-pulse mode, the single pulse mode emits only one water droplet, and the multi-pulse mode can emit multiple water droplets at a time.

[0025] The opening position of the conical micropore is the amplitude superposition position of the piezoelectric transducer.

[0026] The application can be further configured in a preferred example as follows: the control method of the single pulse mode is that the operation of the electric heating layer is closed before the spray is generated, each conical micropore emits only one large water droplet, and the water droplet size is controlled by the single pulse excitation amplitude.

[0027] The application can be further configured in a preferred example as follows: the control method of the multi-pulse mode is that the operation of the electric heating layer is not closed, and the liquid supply module continuously supplies liquid into the water storage tank through the water inlet pipe, a single conical micropore continuously emits large water droplets, the number of water droplets per unit time is adjusted by the pulse frequency, and the water droplet size is adjusted by the pulse amplitude.

[0028] The above technical solutions of the application have the following beneficial technical effects:

[0029] Since the existing technical solutions of the annular transducer cannot meet the demand of single water droplet or multiple water droplets, and cannot meet the requirement of accurate controllable water droplet size, the rectangular transducer is used as the excitation device in the application, the transducer vibration generates surface wave superposition, and the water pool liquid level is controllable in the application. By applying a high-temperature pulse to the air layer on the water layer upper surface, the water tank pressure is controllable during spraying, and the inconsistent water droplet diameter caused by uncontrollable pressure is avoided.

[0030] The application couples core components such as a water droplet monitoring module, a vibration compensation module and a dynamic pressure adjustment module through an auxiliary system, monitors, suppresses vibration, stabilizes pressure, and improves the stability and accuracy of large water droplet emission in multiple dimensions, while ensuring the smoothness of long-term operation of the system. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A water droplet generation system schematic diagram of an embodiment of the application;

[0032] Figure 2 A multi-hole steel sheet structure schematic diagram of an embodiment of the application.

[0033] REFERENCE NUMERALS:

[0034] 1, water tank; 2, piezoelectric transducer; 3, multi-hole steel sheet; 4, conical micro-hole; 5, electric heating layer; 6, copper heat equalizing plate; 7, temperature sensor; 8, liquid supply module; 9, water inlet pipe; 10, water outlet pipe; 11, liquid level sensor; 12, air layer; 13, main control system; 14, liquid supply indicator; 15, spray indicator; 16, high-speed camera; 17, image processing unit; 18, vibration sensor; 19, reverse vibration generator; 20, air pressure regulating valve; 21, pressure sensor; 22, rotator; 23, air pump; 24, fixing frame; 25, cleaning nozzle. DETAILED DESCRIPTION

[0035] To make the purpose, technical solutions and advantages of the application clearer and more explicit, the application is further described in detail below in combination with specific embodiments and with reference to the drawings. It should be noted that the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

[0036] It is understood that the description is only exemplary and is not intended to limit the scope of the application.

[0037] Some embodiments of the application provide a system for generating large water droplets and a control strategy.

[0038] In combination with Figure 1 and Figure 2As shown, the application provides a system for generating large water droplets, comprising: a master control system 13, a liquid supply system, a generating system and an auxiliary system.

[0039] Specifically, the generating system comprises a water storage tank 1, a perforated steel sheet 3 arranged at the bottom of the water storage tank 1, a tapered micro-hole 4 opened on the perforated steel sheet 3, a piezoelectric transducer 2 fixed at the bottom of the perforated steel sheet 3, a copper plate 6 arranged at the top of the water storage tank 1, an electric heating layer 5 mounted on the copper plate 6, and a temperature sensor 7 arranged in the electric heating layer 5.

[0040] Further, the master control system 13 is provided with a liquid supply indicator 14 and a spraying indicator 15. The liquid supply indicator 14 can be used to monitor and control the water supply operation of the liquid supply module 8 to the water storage tank 1 in real time, so that the water quantity in the water storage tank 1 is always maintained within a predetermined range. The spraying indicator 15 indicates the progress of spraying, i.e. the normal operation.

[0041] Specifically, the liquid supply system comprises a liquid supply module 8, a water inlet pipe 9 connected between the water storage tank 1 and the liquid supply module 8, a water outlet pipe 10 connected to the water storage tank 1, and a liquid level sensor 11 arranged on the water outlet pipe 10. The liquid supply module 8 can maintain the water quantity in the water storage tank 1 within a predetermined range, and the liquid level sensor 11 is used to maintain the space of the air layer 12 to avoid excessive water affecting the operation.

[0042] Further, the upper part of the water storage tank 1 is provided with an air layer 12, the bottom of the air layer 12 is located on the same horizontal line as the liquid level sensor 11, and the air layer 12 is arranged to be easily subjected to high-temperature pulse, so that the pressure in the water storage tank 1 is controllable during spraying, and the inconsistency of water droplet diameter caused by uncontrollable pressure is avoided.

[0043] Further, the piezoelectric transducer 2 is provided with at least two groups of piezoelectric transducers 2 located symmetrically at the bottom of the perforated steel sheet 3, and the vibration of the two groups of piezoelectric transducers 2 generates surface wave superposition.

[0044] Further, the water droplet monitoring module comprises a high-speed camera 16 and an image processing unit 17 connected thereto; the high-speed camera 16 is arranged at the bottom of the water storage tank 1 and is used to capture the size and motion trail of the water droplets emitted by the tapered micro-hole 4 in real time; the image processing unit 17 is integrated in the master control system 13 and is used to adjust the excitation parameters of the piezoelectric transducer 2 by analyzing the water droplet image feedback.

[0045] Specifically, the image processing unit 17 calculates the water droplet diameter by an edge detection algorithm, compares it with a preset target diameter, and generates a pulse amplitude correction signal.

[0046] The deviation of the water droplet landing point is also predicted by a trajectory tracking algorithm to generate a trigger timing adjustment signal for the piezoelectric transducer 2.

[0047] We further specifically illustrate the specific implementation of the image processing unit 17:

[0048] The image processing unit 17 analyzes the water droplet image and feeds back the trigger parameter adjustment of the piezoelectric transducer 2 by the following steps:

[0049] Image acquisition and preprocessing: The high-speed camera 16 captures the water droplet image emitted by the conical micropore 4 at a rate of not less than 1000 frames per second, and the main control system 13 performs denoising, grayscale and edge sharpening processing on the image to extract the clear water droplet contour;

[0050] Feature quantization: The edge detection algorithm based on machine vision such as Canny operator is used to accurately calculate the diameter and shape parameters of the water droplet, and the optical flow method is used to track the motion trajectory of the water droplet to obtain its speed, acceleration and landing point position;

[0051] Data comparison and feedback: The difference between the real-time measured water droplet diameter and the preset target value is analyzed to generate a pulse amplitude correction signal; at the same time, the trigger timing adjustment signal is generated according to the trajectory prediction deviation, and the single pulse amplitude, multi-pulse frequency or trigger delay time of the piezoelectric transducer 2 is dynamically adjusted;

[0052] Closed-loop control: The main control system 13 transmits the correction signal to the driving circuit of the piezoelectric transducer 2 in real time through the PID algorithm, ensuring that the water droplet size error is controlled within ±5 microns, and the trajectory deviation is less than 2% of the preset threshold.

[0053] Technical effect: Through the closed-loop feedback mechanism of the image processing unit 17, dynamic calibration of the water droplet generation process is realized, and the size consistency, trajectory accuracy and system response speed of the emission are significantly improved.

[0054] Further, the vibration compensation module includes a vibration sensor 18 and a reverse vibration generator 19;

[0055] The vibration sensor 18 is installed on the side of the perforated steel sheet 3 for detecting the asymmetric vibration generated by the piezoelectric transducer 2 when triggered;

[0056] The reverse vibration generator 19 is fixed to the outer wall of the water storage tank 1, which generates a reverse vibration wave to offset the vibration interference of the perforated steel sheet 3, and the driving frequency of the reverse vibration generator 19 is synchronized with the trigger frequency of the piezoelectric transducer 2, and the amplitude is dynamically matched with the vibration superposition effect in the multi-pulse mode through the adaptive algorithm of the main control system 13.

[0057] Further, the dynamic pressure regulation module includes a gas pressure regulating valve 20 and a pressure sensor 21;

[0058] The pressure sensor 21 is embedded in the air layer 12 of the water tank 1 to monitor the pressure change of the air layer 12 in real time;

[0059] The air pressure regulating valve 20 is connected with the main control system 13 to dynamically adjust the pressure of the air layer 12 according to the feedback of the pressure sensor 21, so as to maintain the constant liquid level pressure.

[0060] Further, the auxiliary system further comprises a micropore cleaning module, the micropore cleaning module comprises a rotating device 22 arranged at the bottom of the water tank 1, a gas pump 23 installed on the rotating device 22, a fixed frame 24 fixed to the side of the rotating device 22, and a cleaning nozzle 25 connected to the gas pump 23 through a pipeline and installed on the fixed frame 24, the cleaning nozzle 25 is arranged around the conical micropore 4 of the multi-hole steel sheet 3, the micro gas pump 23 periodically removes the residues in the conical micropore 4 through pulse high-pressure gas flow, and the starting frequency is automatically optimized by the main control system 13 according to the liquid supply record of the liquid level sensor 11.

[0061] Further, the cleaning period of the gas pump 23 is staggered with the heating period of the electric heating layer 5 to avoid the thermal interference of high temperature on the cleaning gas flow, and the cleaning interval is dynamically adjusted through the data of the temperature sensor 7.

[0062] It should be noted that based on the above system of generating large water droplets, the following control strategies are further included:

[0063] First, the main control system 13 is opened, and the liquid supply module 8 automatically inputs deionized water into the water tank 1 until the liquid level reaches the position of the water outlet liquid level sensor 11, and then stops supplying liquid;

[0064] When the single water droplet generation starts, the electric heating layer 5 is powered first, and the power supply is stopped when the temperature sensor 7 feedbacks that the temperature reaches the preset value;

[0065] Immediately after stopping the electric heating, the piezoelectric transducer 2 is excited, and the piezoelectric transducer 2 is set to single pulse or multi-pulse mode, the single pulse mode emits only one water droplet, and the multi-pulse mode can emit multiple water droplets at a time.

[0066] Further, the control method of the single pulse mode is that the operation of the electric heating layer 5 is closed before the spray is generated, each conical micropore 4 emits only one large water droplet, and the water droplet size is controlled through the single pulse excitation amplitude.

[0067] Further, the opening position of the conical micropore 4 is the amplitude superposition position of the piezoelectric transducer 2.

[0068] Further, the control method of the multi-pulse mode is that the operation of the electric heating layer 5 is not turned off, and the liquid supply module 8 continuously supplies liquid into the water storage tank 1 through the water inlet pipe 9, and the single conical micro-hole 4 continuously emits large water droplets, the number of water droplets per unit time is adjusted by the pulse frequency, and the water droplet size is adjusted by the pulse amplitude.

[0069] In this scheme, water droplet dynamics is the scientific field that studies the motion behavior, mechanical properties, and interactions of water droplets under different conditions.

[0070] Mainly includes the following aspects:

[0071] 1. Water droplet generation and separation: Study the formation process of water droplets (such as separation from the liquid surface or nozzle), and analyze how water droplet size, shape, and generation frequency are affected by control factors such as pressure, surface tension, and fluid dynamics.

[0072] 2. Water droplet trajectory: Explore the trajectory and speed of water droplets in different media (such as air or other liquids). External forces such as gravity, air resistance, buoyancy, and surface tension will affect the acceleration and motion path of water droplets. For example, raindrops fall in the air and are affected by air resistance, eventually reaching a terminal velocity, and the movement speed remains stable.

[0073] 3. Water droplet collision and merging: When two or more water droplets meet, they may collide, merge, or break apart. The collision behavior of water droplets is affected by speed, temperature, surface tension, and collision angle. This process is particularly important in cloud physics (such as rain formation) and spraying technology (such as inkjet printing).

[0074] 4. Water droplet deformation and breakup: In high-speed motion or high-pressure environments, water droplets may deform, elongate, or even break into smaller droplets. The deformation process of water droplets is affected by fluid dynamics, surface tension, and inertial force. This process is important in aviation, spray cooling, and combustion research, as water droplet breakup can affect combustion efficiency or cooling effect.

[0075] 5. Water droplet evaporation and condensation: When the environment temperature or humidity changes, water droplets may evaporate or condense. Evaporation will gradually reduce the volume of water droplets, while condensation will make water droplets larger. The evaporation and condensation processes are very important in meteorology (such as cloud and rain formation), agricultural irrigation, and cooling tower design.

[0076] 6. Water droplet interaction with solid surfaces: The behavior of water droplets when they contact solid surfaces, such as spreading, bouncing, or wetting characteristics on the surface. The contact angle of water droplets (the angle between the liquid and the solid surface) and the hydrophilic or hydrophobic properties of the surface material will affect the behavior of water droplets on the surface. This phenomenon has wide applications in surface treatment, printing, coating design, and biomedical applications.

[0077] 7. Water droplet aerodynamics: In high-speed airflows, the shape and motion of water droplets are significantly affected. For example, water droplets on an airplane wing or a car windshield can deform, slide, or break due to air pressure. This dynamic process is of great significance in aviation safety and vehicle design.

[0078] Although embodiments of the present application have been shown and described, it would be appreciated by those skilled in the art that changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the application, the scope of which is defined by the claims and their equivalents.

Claims

1. A system for generating large water droplets, characterized by include: Main control system (13), liquid supply system, liquid generation system and auxiliary system; The generating system includes a water tank (1), a porous steel sheet (3) disposed at the bottom of the water tank (1), a conical micro-hole (4) opened on the porous steel sheet (3), a piezoelectric transducer (2) fixed at the bottom of the porous steel sheet (3), a heat-spreading copper plate (6) disposed at the top of the water tank (1), an electric heating layer (5) installed on the heat-spreading copper plate (6), and a temperature sensor (7) disposed in the electric heating layer (5). The liquid supply system includes a liquid supply module (8), an inlet pipe (9) connected between the water storage tank (1) and the liquid supply module (8), an outlet pipe (10) connected to the water storage tank (1) and a liquid level sensor (11) installed on the outlet pipe (10). The auxiliary system includes a water droplet monitoring module, a vibration compensation module, and a dynamic pressure regulation module; An air layer (12) is left at the top of the water storage tank (1), and the bottom of the air layer (12) is on the same horizontal line as the liquid level sensor (11); The piezoelectric transducer (2) is provided with at least two sets of symmetrically located at the bottom of the porous steel sheet (3), and the opening position of the conical micro-hole (4) is the position where the piezoelectric transducer (2) superimposes the amplitude. The vibration compensation module includes a vibration sensor (18) and a reverse vibration generator (19). The vibration sensor (18) is installed on the side of the porous steel sheet (3) to detect the asymmetric vibration generated when the piezoelectric transducer (2) is excited; The reverse vibration generator (19) is fixed to the outer wall of the water storage tank (1) and generates reverse vibration waves to counteract the vibration interference of the porous steel sheet (3). The dynamic pressure regulation module includes a pressure regulating valve (20) and a pressure sensor (21). The pressure sensor (21) is embedded in the air layer (12) of the water storage tank (1) to monitor the pressure change of the air layer (12) in real time; The pressure regulating valve (20) is connected to the main control system (13) and dynamically adjusts the pressure of the air layer (12) according to the feedback of the pressure sensor (21) in order to maintain a constant liquid surface pressure.

2. A system for generating large water droplets according to claim 1, wherein The water droplet monitoring module includes a high-speed camera (16) and an image processing unit (17) connected thereto. The high-speed camera (16) is located at the bottom of the water storage tank (1) and is used to capture the size and trajectory of the water droplets emitted by the conical micro-hole (4) in real time. The image processing unit (17) is integrated into the main control system (13) and adjusts the excitation parameters of the piezoelectric transducer (2) by analyzing the water droplet image feedback.

3. A system for generating large water droplets according to claim 1, wherein The auxiliary system also includes a micropore cleaning module, which includes a rotator (22) disposed at the bottom of the water tank (1), an air pump (23) mounted on the rotator (22), a fixing frame (24) fixed to the side of the rotator (22), and a cleaning nozzle (25) connected to the air pump (23) and mounted on the fixing frame (24) via a pipe.

4. A system for generating large water droplets according to claim 2, wherein The image processing unit (17) calculates the water droplet diameter by an edge detection algorithm, and compares it with a preset target diameter to generate a pulse amplitude correction signal; It also predicts the water droplet landing point deviation by a trajectory tracking algorithm, and generates a piezoelectric transducer (2) excitation timing adjustment signal.

5. A system for generating large water droplets according to claim 1, wherein The following control strategies are also included: First, turn on the main control system (13), and the liquid supply module (8) automatically inputs deionized water into the water storage tank (1) until the liquid level reaches the outlet liquid level sensor (11) position, then stop supplying liquid; At the beginning of single water droplet generation, first power on the electric heating layer (5), and stop power supply when the temperature sensor (7) feedback temperature reaches the preset value; Immediately after stopping the electric heating, excite the piezoelectric transducer (2), and the piezoelectric transducer (2) excitation is set to single pulse or multi-pulse mode, single pulse mode only emits one water droplet, and multi-pulse mode can emit multiple water droplets at a time.

6. A system for generating large water droplets according to claim 5, wherein, The control method of single pulse mode is: the operation of the electric heating layer (5) is turned off before the spray is generated, each conical micro-hole (4) only emits one large water droplet, and the water droplet size is controlled by single pulse excitation amplitude.

7. A system for generating large water droplets according to claim 5, wherein The control method of multi-pulse mode is: the operation of the electric heating layer (5) is not turned off, and the liquid supply module (8) continuously supplies liquid into the water storage tank (1) through the inlet pipe (9), a single conical micro-hole (4) continuously emits large water droplets, the number of water droplets per unit time is adjusted by the pulse frequency, and the water droplet size is adjusted by the pulse amplitude.

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