1. A gas flow field PIV tracer particle preparation facilities based on nanometer bubble technique which characterized in that: comprises a drying cavity, a pipeline valve, a fan, a high-pressure helium/hydrogen cylinder, a nano bubble generator, a temperature sensor, an ultrasonic atomization device, a drying pipe and a hot air blower; the high-pressure helium/hydrogen cylinder continuously provides an air source through an air inlet of the nano bubble generator, meanwhile, water is supplied through a water inlet of the nano bubble generator, so that a helium/hydrogen nano bubble solution is generated, then, the solution is atomized through an ultrasonic atomization device and sprayed into the drying cavity, and a hot air blower introduces dry air into the drying cavity through a drying pipe; the atomized droplets fall in a dry gas environment to finally form droplets with the particle size of 1-5 microns; the formed liquid drops are continuously conveyed to an airflow field testing section under the action of a fan; the drying chamber comprises a conical top cover, a cylindrical body and a conical bottom cover which is convenient for collecting liquid drops, the ultrasonic atomization device is arranged at the upper end of the top cover, and the inlet of the drying tube is respectively arranged on the conical surface and the cylindrical body at the lower end of the top cover.

2. The device for preparing PIV tracer particles in a gas flow field based on nanobubble technology as claimed in claim 1, wherein: the hot air blower is adjusted according to the temperature displayed by the temperature sensor on the drying cavity, so that the temperature of the drying cavity ranges from 50 ℃ to 90 ℃.

3. The device for preparing PIV tracer particles in a gas flow field based on nanobubble technology as claimed in claim 1, wherein: the nano bubble generator adopts a Venturi tube method, an ultrasonic cavitation method or a mechanical shearing method according to the working principle.

4. The device for preparing PIV tracer particles in a gas flow field based on nanobubble technology as claimed in claim 3, wherein: the nano bubble solution is produced by adopting a mechanical shearing method nano bubble generator, the gas flow range is 0.1L/h-0.5L/h, and the liquid flow range is 1L/h-3L/h.

5. The device for preparing PIV tracer particles in a gas flow field based on nanobubble technology as claimed in claim 1, wherein: the ultrasonic atomization device adopts a piezoelectric ultrasonic atomization device or a flow power ultrasonic atomization device, the atomization amount per hour is 100ml/h-200ml/h, the Sott average diameter range is 3 mu m-7 mu m, and the diameter range of fog drops is 1 mu m-10 mu m.

6. The device for preparing PIV tracer particles in a gas flow field based on nanobubble technology as claimed in claim 1, wherein: the temperature sensor is arranged on the cylindrical body of the drying cavity, and the temperature range to be measured by the temperature sensor is between 0 and 100 ℃.

7. A preparation method of PIV tracer particles of an airflow field based on a nanobubble technology is characterized by comprising the following steps:

opening a valve of a high-pressure helium/hydrogen cylinder, continuously providing an air source through an air inlet of a nano bubble generator, simultaneously supplying water through a water inlet of the nano bubble generator, and generating a helium/hydrogen nano bubble solution under the action of the nano bubble generator;

secondly, opening an ultrasonic atomization device to atomize the helium/hydrogen nanobubble solution and spraying the solution into a drying cavity;

thirdly, the small liquid drops formed by the ultrasonic atomization device fall and are dried in a drying cavity, and then liquid drops with smaller particle sizes are formed;

and fourthly, opening a pipeline switch, and continuously conveying the liquid drops with the particle size of 1-5 mu m formed in the drying cavity to the airflow field testing section under the action of the fan.

8. The method for preparing PIV tracer particles in the gas flow field based on the nanobubble technology as claimed in claim 7, wherein: in the third step, a hot air blower is added to introduce dry air into the drying cavity through the drying pipe.

Background

The PIV (particle image velocimetry) technology is a modern flow field measurement technology established based on image cross-correlation analysis. The technology integrates the advantages of a display measurement technology and a single-point measurement technology, not only can the whole structure of the measured flow field be displayed, but also the resolution and the precision of measurement are ensured. The technology can realize the measurement of the transient state of the flow field on the premise of not generating any interference on the flow field, and has very high resolution and precision. The PIV flow field measurement technology has the advantages of non-contact, no interference and the like, so that the PIV flow field measurement technology becomes the most common method in the field of current flow measurement.

The basic principle of the PIV technology is that tracer particles are uniformly scattered into fluid, then a laser is used for emitting pulse laser to form a sheet light plane in a flow field, and the tracer particles in the flow field are reflected or displayed in a fluorescent mode; arranging a camera in the vertical direction of a light sheet plane, exposing the camera at the pulse time of laser by adopting a synchronizer, capturing a particle image, and then storing the particle image into a computer; and the computer compares and analyzes the front image and the rear image by using a correlation algorithm to obtain the particle displacement, so that a velocity vector diagram of the full flow field is obtained. In essence, the velocity of the particles in the flow field is measured by the PIV, and the velocity of the flow field at the position of the particles is represented by the tracer particles which are scattered in the fluid and have good following performance.

The tracer particle is one of the necessary conditions for completing the PIV measurement, and the self characteristics of the tracer particle directly influence the effective degree of the measurement result. In the PIV technology, the velocity of the tracer particles which are well distributed in the fluid and have good follow-up performance is used for replacing velocity information of a flow field, so that the flow performance, the optical performance and other characteristics of the tracer particles have great influence on the PIV result. In addition, the size of the tracer particles is also very important, and the particles with proper size can ensure the accuracy of measurement. The size of the trace particles needs to be selected in consideration of the following aspects that the particle size is small enough compared with the measured area, the particle diameter is small, and the PIV measurement has good measurement precision; meanwhile, the particle size must meet the imaging requirement of an image acquisition system, the particles are too small to be imaged easily, and are easily interfered by noise points, so that the measurement precision is influenced. Thus, only a correct selection of trace particles can obtain a more accurate flow field flow characteristic.

At present, the PIV tracer particles commonly used in the experiment are mainly classified into the following categories: the first is to atomize the liquid into liquid drops as the trace particles, such as paraffin oil, and although the trace particles have good following performance in a flow field, the trace particles can cause pollution; the second type is titanium dioxide particles, silicon dioxide particles, aluminum oxide particles, magnesium oxide particles, glass beads, talcum powder, aluminum powder, magnesium powder and the like, and the tracing particles are high in density, so that the tracing performance in some flow fields is poor; the third type is polymer particles such as polystyrene and the like, the density of the tracer particles is about 1.1g/cm3, the flow field following performance is good, but the preparation cost of the tracer particles is high.

The tracer particles need to have good scattering characteristics and good following performance at the same time, however, the existing preparation method cannot meet the requirements at the same time, and a new tracer particle preparation method needs to be established. According to the invention, the micron-sized droplets containing a large number of nano-scale holes are prepared, and the trace particles have good scattering property and followability due to low density, and the preparation cost of the trace particles is low.

Disclosure of Invention

The invention aims to prepare a novel PIV tracing particle, which takes water, helium/hydrogen as materials and has a structure of a micron-sized droplet containing a large number of nano-scale holes. The particle size of the PIV tracer particle is 1-5 mu m, the density is 0.80g/cm3-0.95g/cm3, the particle size distribution is narrow, and the PIV tracer particle has good flow field following performance and light scattering property, and in addition, the preparation cost of the novel PIV tracer particle is low.

It is another object of the invention to propose a method for preparing novel PIV tracer particles. The density of the liquid is reduced by the nano-bubble generator, and then the helium/hydrogen nano-bubble solution is atomized into small droplets by the ultrasonic atomization device, so that the helium/hydrogen nano-bubble solution has good flow field following property; wherein, the drying cavity is continuously filled with hot dry air as a drying medium, thereby further reducing the diameter of small droplets and improving the flow field following property of tracer particles; in addition, a large number of nano-scale holes in the micro-droplets enhance the reflection of light, so that the light is difficult to transmit, and the tracer particles have good light scattering property.

The technical scheme adopted by the invention is as follows: a device for preparing PIV tracer particles in an airflow field based on a nanobubble technology comprises a drying cavity, a pipeline valve, a fan, a high-pressure helium/hydrogen cylinder, a nanobubble generator, a temperature sensor, an ultrasonic atomization device, a drying pipe and a hot air blower; the high-pressure helium/hydrogen cylinder continuously provides an air source through an air inlet of the nano bubble generator, meanwhile, water is supplied through a water inlet of the nano bubble generator, so that a helium/hydrogen nano bubble solution is generated, then, the solution is atomized through an ultrasonic atomization device and sprayed into the drying cavity, and a hot air blower introduces dry air into the drying cavity through a drying pipe; the atomized droplets fall in a dry gas environment to finally form droplets with the particle size of 1-5 microns; the formed liquid drops are continuously conveyed to an airflow field testing section under the action of a fan; the air heater can be adjusted according to the temperature displayed by the temperature sensor on the drying cavity, so that the drying cavity is in a proper temperature range (50-90 ℃).

The invention relates to a device for preparing PIV tracer particles in an airflow field based on a nano-bubble technology, wherein a nano-bubble generator can be divided into a venturi tube method, an ultrasonic cavitation method and a mechanical shearing method according to the working principle. The mechanical shearing method has low cost and high production efficiency, and is widely applied in the industry. The invention adopts a mechanical shearing method nano bubble generator to produce nano bubble solution. The mechanical shearing method is characterized in that when gas is introduced into liquid, large bubbles are generated in the liquid due to the existence of gas-liquid two phases, and the large bubbles are stirred and sheared at high speed by a blade, a thread and other parts to form nano bubbles. The gas flow range of the nano bubble generator can be 0.1L/h-0.5L/h, and the liquid flow range can be 1L/h-3L/h. The use of the nanobubble generator reduces the density of the liquid, allowing good fluid follow-up of the subsequently generated droplets.

The invention relates to a device for preparing PIV (particle image velocimetry) tracer particles in an airflow field based on a nanobubble technology, wherein an ultrasonic atomization device is divided into a piezoelectric ultrasonic atomization device and a flow-force ultrasonic atomization device. Important indexes for measuring the atomizing performance of the atomizer are the average diameter of the fogdrop and the diameter distribution of the fogdrop. The atomization amount of the ultrasonic atomization device used in the invention per hour is 100ml/h-200ml/h, the Sott average diameter of the device is 3 mu m-7 mu m, and the diameter of the fog drops is 1 mu m-10 mu m. The ultrasonic atomization device atomizes the helium/hydrogen nano bubble solution into small droplets, so that the flow field following performance of the ultrasonic atomization device is further improved.

The invention relates to a device for preparing PIV tracer particles in an airflow field based on a nanobubble technology, wherein a drying cavity comprises a conical top cover, a cylindrical body and a conical bottom cover convenient for collecting liquid drops. The ultrasonic atomization device is arranged at the upper end of the top cover, and the inlet of the drying pipe is respectively arranged on the conical surface and the cylindrical body at the lower end of the top cover.

The invention relates to a device for preparing PIV tracer particles in an airflow field based on a nanobubble technology, wherein a temperature sensor is arranged on a cylindrical body of a drying cavity, and the temperature range to be measured by the temperature sensor is between 0 and 100 ℃.

The invention relates to a novel PIV tracer particle preparation device, which corresponds to an airflow field PIV tracer particle preparation method based on a nanobubble technology and comprises the following operation steps:

opening a valve of a high-pressure helium/hydrogen cylinder, continuously providing an air source through an air inlet of a nano bubble generator, simultaneously supplying water through a water inlet of the nano bubble generator, and generating a helium/hydrogen nano bubble solution under the action of the nano bubble generator;

secondly, opening an ultrasonic atomization device to atomize the helium/hydrogen nanobubble solution and spraying the solution into a drying cavity;

thirdly, the small liquid drops formed by the ultrasonic atomization device fall and are dried in a drying cavity, and then liquid drops with smaller particle sizes are formed;

and fourthly, opening a pipeline switch, and continuously conveying the liquid drops with the particle size of 1-5 mu m formed in the drying cavity to the airflow field testing section under the action of the fan.

The invention relates to a preparation method of PIV tracer particles in an airflow field based on a nano bubble technology, which is characterized in that in the third step, a hot air blower is added to introduce dry air into a drying cavity through a drying pipe, and the temperature range of the drying cavity is between 0 and 100 ℃.

Compared with the prior art, the invention has the advantages that:

1. the density of the liquid is reduced by the nano-bubble generator, and then the helium/hydrogen nano-bubble solution is atomized into small droplets by the ultrasonic atomization device, so that the helium/hydrogen nano-bubble solution has good flow field following property;

2. the internal large number of nano-scale holes enhances the reflection of light, so that the light is difficult to transmit, and the tracer particles have good light scattering property.

3. After the experiment is finished, the temperature is raised, small drops generated by water can be sublimated and evaporated, and the experiment environment can not be polluted.

Drawings

Fig. 1 is a schematic diagram of a device for preparing PIV tracer particles in an airflow field based on a nanobubble technology.

In the figure: 1-drying cavity, 2-pipeline valve, 3-blower, 4-high pressure helium/hydrogen cylinder, 5-nano bubble generator, 6-temperature sensor, 7-ultrasonic atomization device, 8-drying pipe and 9-hot air blower.

Detailed Description

The invention relates to a device for preparing PIV tracer particles in an airflow field based on a nanobubble technology, which comprises a drying cavity 1, a pipeline valve 2, a fan 3, a high-pressure helium/hydrogen cylinder 4, a nanobubble generator 5, a temperature sensor 6, an ultrasonic atomization device 7, a drying pipe 8 and a hot air blower 9, as shown in figure 1. Opening a valve of the high-pressure helium/hydrogen cylinder 4, enabling the high-pressure helium/hydrogen cylinder to continuously provide an air source through an air inlet of the nano bubble generator 5, simultaneously supplying water through a water inlet of the micro-nano bubble generator 5, generating a helium/hydrogen nano bubble solution under the action of the micro-nano bubble generator 5, then starting an ultrasonic atomization device 7 to atomize the helium/hydrogen nano bubble solution, and spraying the atomized helium/hydrogen nano bubble solution into the drying cavity 1; the hot air blower 9 introduces dry air into the drying cavity 1 through the drying pipe 8, and small droplets formed by the ultrasonic atomization device 7 are evaporated in a dry gas environment to reduce the particle size; and finally, opening a pipeline valve 2, and continuously conveying the liquid drops with the particle size of 1-5 mu m formed in the drying cavity 1 to an airflow field testing section under the action of a fan 3. In addition, the whole tightness of the device is required to be ensured, the temperature in the drying box can be controlled more accurately, and the heat loss is reduced.

The invention relates to a preparation method of PIV tracer particles in an airflow field based on a nanobubble technology, which comprises the following steps:

1. opening a valve of a high-pressure helium/hydrogen cylinder, continuously providing an air source through an air inlet of a nano bubble generator, wherein the flow rate of helium/hydrogen is 0.2L/h, simultaneously supplying water through an water inlet of the nano bubble generator, the flow rate is 2L/h, and generating a helium/hydrogen nano bubble solution under the action of the nano bubble generator; the concentration of bubbles in liquid per milliliter can reach the magnitude of tens of millions to hundreds of millions, and the density of the liquid is reduced to 0.80g/cm3-0.95g/cm 3;

2. starting an ultrasonic atomization device to atomize the helium/hydrogen nanobubble solution, wherein the atomization flow is 2L/h, the size of liquid drops obtained by atomization is 1-10 mu m, and then spraying the liquid drops into a drying cavity;

3. the small droplets formed by the ultrasonic atomization device fall in a dry hot gas environment, and further the droplets with smaller particle size (the diameter is between 1 μm and 5 μm) are obtained through evaporation;

4. and opening a pipeline valve, and sending the liquid drops with the particle size of 1-5 mu m formed in the drying cavity to the airflow field testing section.