Control system and method for PIV clean particle generation and transmission system in low-temperature environmentTechnical Field
The invention belongs to the technical field of low-temperature tests, and particularly relates to a control system and a control method of a PIV clean particle generation and transmission system in a low-temperature environment.
Background
PIV technology utilizes double pulse laser to irradiate to the measured object, and the tracer particles are broadcast in the measured object, so as to obtain continuous 2 particle images, and the particle displacement is obtained by utilizing a cross correlation algorithm, so that the tracer particle speed is obtained. Since the tracer particles follow the movement of the object under test, the measured tracer particle velocity can be considered as the velocity of the object under test (provided that the particles are able to truly follow the object under test). In PIV test experiments, the following properties, light scattering properties and concentration of the trace particles play a decisive role in the quality of the test data.
The following property and the light scattering property of the tracer particle mainly depend on the density and the particle size of the tracer particle material, and for the same tracer particle material, the smaller the particle size of the tracer particle, the better the following property, the higher the data reliability, but the smaller the particle size can cause the brightness of the particle to be poor, and the signal to noise ratio of an original image to be affected, otherwise, the larger the particle size, the higher the brightness of the particle, the better the signal to noise ratio of the image, but the following property can be poor. In the PIV test, proper tracer particles are necessary to be selected according to practical application requirements, so that good balance of the tracer particles in the following property and the light scattering property is ensured.
PIV test technology is widely applied in normal temperature environment, and at present, conventional trace particles used in normal temperature environment are mainly divided into two main types, namely one type of oily liquid based on DEHS, vegetable oil and the like, the oily particle with the particle size of about 1 mu m can be generated by utilizing a Laskin nozzle atomization principle, and the other type of solid powder based on SiO2 and the like, and stable nano-level solid powder particles can be generated by utilizing a fluidized bed principle.
PIV tests are carried out in certain low-temperature environments, and the conventional trace particle generation technology is not applicable any more, and is mainly because of the pollution problem of the conventional trace particles, a large amount of heat insulation materials are often wrapped around the low-temperature pipeline test environment, and oil particles or solid powder particles pollute the heat insulation materials, so that the material is invalid due to the physical property change of the materials. Meanwhile, the physical properties of the oily liquid and the solid particles are very stable, and the oily liquid and the solid particles can be stuck inside the inner wall of the low-temperature pipeline and the heat insulation material for a long time after the test is finished, and cannot volatilize or degrade.
Therefore, PIV test research is carried out in a low-temperature test environment, a brand-new clean particle generation and transmission system is needed, and the technical requirements of 1) adopting clean tracer particle materials, 2) stabilizing physical properties of the tracer particles and being easy to clean after the test is finished, 3) particle size and density of the tracer particles meet the requirement of flow field following performance, 4) scattering performance of the tracer particles meets the requirement of optical measurement, and 5) concentration of the tracer particles is higher and controllable are met.
In summary, the problem of environmental pollution in the test can be well solved by using water as a trace particle material, but how to convert the water into trace particle flow with controllable particle size and concentration is a problem to be solved. The literature research and ground research show that three modes of generating micro water drops are mainly available, namely, the ultrasonic atomization principle is utilized, the device is easy to purchase in the market, the water mist concentration is large and is convenient to control, the average measured value of the particle size is basically 5-10 mu m, the following performance of PIV test experiments is not up to standard, the micro atomization nozzle principle is utilized, the device is easy to purchase in the market and is low in price, the technical index of the device usually declares that the particle size is 1 mu m or lower, the measured result shows that the particle size is usually larger than 20 mu m and even 100 mu m, the uniformity of the particle size is poor, PIV test experiment requirements cannot be met, the third mode is a method of instantly condensing water vapor, a pen successfully generates water particles or ice particles with the particle size of about 1 mu m in ground debugging in the mode, the PIV test experiments under the low-temperature environment can be successfully used, and the whole tracer particle generation process is required to be in a controllable state.
Currently, there is a need to develop a control system and method for a PIV clean particle generation and transport system in a low temperature environment.
Disclosure of Invention
The invention aims to provide a control system of a PIV clean particle generation and transmission system in a low-temperature environment, and aims to provide a control method of a PIV clean particle generation and transmission system in a low-temperature environment.
The control system of the PIV clean particle generation and transmission system in the low-temperature environment comprises a basic sensing layer, a basic control layer, a network transmission layer and an application service layer which are arranged from bottom to top, wherein the layers are connected through pipelines, cables and networks;
The basic sensing layer comprises a normal pressure pipeline subsystem, a cooling air flow pipeline subsystem, a trace particle generator subsystem, a cooling mixing device and a particle transmission pipeline subsystem;
The basic control layer comprises a programmable controller CPU, a programmable controller expansion module, a touch screen, a switch, a signal isolator, an intermediate relay, a low-voltage circuit breaker, a button indicator light and an uninterruptible power supply;
the network transmission layer comprises an industrial electric port switch and a network cable;
The application service layer comprises an upper computer, system software, monitoring software and a database.
The normal pressure pipeline subsystem is connected with a medium pressure nitrogen source and a trace particle generator through a normal pressure gas source pipeline, and a manual valve, a filter, an electronic pressure regulating valve, a check valve, a temperature sensor and a pressure sensor are arranged on the normal pressure gas source pipeline;
The normal pressure pipeline subsystem introduces the medium pressure nitrogen of the medium pressure nitrogen source into the trace particle generator through the interface reserved in the test hall, is used for driving the trace particle generator and simultaneously is also used as driving airflow of PIV trace particle flow, and is also used for monitoring the medium pressure nitrogen at the front end of the particle generator, so that the temperature and the pressure of the medium pressure nitrogen entering the particle generator are both within the design range.
The cooling air flow pipeline is provided with a safety valve, a filter, an electric pressure regulating valve, a temperature sensor, a pressure sensor, a flow sensor and a liquid nitrogen flash tank;
the cooling air flow pipeline converts liquid nitrogen from a test site into cryogenic dry nitrogen and transmits the cryogenic dry nitrogen to the cooling mixing device as a cooling air source, and the specific process is as follows:
The liquid nitrogen of the cooling air flow pipeline is provided by a low-temperature nitrogen source of a test site, namely a liquid nitrogen tank, the pressurized gas of the cooling air flow pipeline is provided by a medium-pressure nitrogen source in a factory building, the cooling air flow pipeline sprays the liquid nitrogen into a liquid nitrogen flash tank to cool the normal-temperature medium-pressure nitrogen, the liquid nitrogen is mixed with the medium-pressure nitrogen in the liquid nitrogen flash tank to form the cryogenic dry nitrogen, and the cryogenic dry nitrogen enters a cooling mixing device through the cooling air flow pipeline.
The tracer particle generator subsystem is characterized in that a main body of the tracer particle generator subsystem is a tracer particle generator, a pressure sensor, a temperature transmitter, a check valve, an electric heater and a manual valve are arranged on the tracer particle generator, and the tracer particle generator subsystem generates a humid air flow in a tracer particle generator container through a Laskin nozzle, wherein the humid air flow contains air with average diameter of l mu m-3 mu m or normal-temperature near-saturated water vapor.
Further, the main body of the cooling mixing device is a cooling tank, and a temperature transmitter and a regulating valve are arranged on the cooling tank;
The wet air flow generated by the trace particle generator subsystem and the cryogenic dry nitrogen generated by the cooling air flow pipeline subsystem are mixed in a cooling tank of the cooling mixing device, water vapor particles in the wet air flow are instantaneously condensed into ice particles with the average diameter of l mu m to 3 mu m, and the ice particles are injected into an inner runner of the particle transmission pipeline subsystem as PIV trace particles through a heat insulation pipeline.
The particle transmission pipeline subsystem comprises a particle transmission pipeline, wherein a manual valve and an electric valve are arranged on the particle transmission pipeline, and the particle transmission pipeline subsystem transmits PIV trace particles generated by the cooling mixing device into an inner flow path of the low-temperature test device.
The control method of the PIV clean particle generation and transmission system in the low-temperature environment comprises the following steps:
S10, checking by a control system;
the administrator checks and confirms that the instrument cable, the control cable, the power cable and the aviation plug are connected correctly and have perfect functions;
After an administrator checks that all the electric valves are closed, all the manual valves needing to be opened in advance are opened to be fully opened manually;
the administrator checks all the mechanical pointer tables to ensure that the mechanical pointer tables are intact and the readings are within the set normal range;
manually recording an inspection result after the inspection of the manager is completed;
s20, self-checking by a control system;
powering up a control system;
starting up an upper computer of the control system, logging in a correct user name, and entering an operation interface;
the control system performs self-checking to determine that the medium-pressure nitrogen pressure is within a set range;
the control system performs self-checking to determine that the medium-pressure nitrogen temperature is within a set range;
The control system self-tests to determine that the liquid nitrogen pressure is within a set range;
the control system performs self-checking to determine that the liquid level in the trace particle generator is in a set range;
the control system performs self-checking to determine that the temperature of the liquid in the trace particle generator is within a set range;
The control system is ready to complete;
S30, performing PIV test;
s301, controlling a system to dry and purge;
Clicking a drying purge start button on an operation interface of the upper computer;
The control system starts a medium-pressure nitrogen source main valve;
the control system opens the regulating valve of the medium-pressure nitrogen source by 50%;
the control system opens the regulating valve of the low-temperature nitrogen source by 50%;
the control system starts an electric gate valve of the particle transmission pipeline to dry and purge the particle transmission pipeline;
After the drying and purging time reaches the set time, the control system closes the electric gate valve of the particle transmission pipeline, and then delays to close the medium-pressure nitrogen source main valve and the regulating valve of the medium-pressure nitrogen source;
Ending the drying and blowing;
s302, PIV test preparation;
The control system starts an electric heater of the trace particle generator, heats the water temperature to 60 ℃ and keeps the temperature continuously;
The control system adjusts the pressure at the rear end of the trace particle generator to 0.6MPa through an adjusting valve of a medium-pressure nitrogen source;
The control system adjusts the pressure at the rear end of the cooling tank to 0.55MPa through a regulating valve of a medium-pressure nitrogen source;
the control system opens an electric gate valve of the particle transmission pipeline;
S303, opening liquid nitrogen;
the control system opens an electric regulating valve of a liquid nitrogen tank conveying pipeline;
the control system determines that the temperature, the pressure and the flow of the liquid nitrogen tank conveying pipeline are within a design range;
the control system determines that the temperature and the pressure of the cooling airflow pipeline are within a design range;
The cryogenic dry nitrogen enters a cooling mixing device through a cooling airflow pipeline, and the flow stability of the cryogenic dry nitrogen is ensured;
S304, opening a Laskin nozzle;
the temperature of the cooling air flow pipeline is reduced to be within a set range, and the control system opens the electric regulating valve;
The control system starts an electric valve of a Laskin nozzle pipeline, dry nitrogen generates a humid air flow in a trace particle generator container through the Laskin nozzle, and the humid air flow contains air of water vapor particles with the average diameter of l mu m to 3 mu m or normal-temperature near-saturated water vapor;
Mixing the wet air flow generated by the trace particle generator subsystem and the cryogenic dry nitrogen generated by the cooling air flow pipeline subsystem in a cooling tank of a cooling mixing device, and instantly condensing water vapor particles in the wet air flow into ice particles with the average diameter of l mu m-3 mu m;
the control system detects whether the particle size and the concentration of the ice particles meet the PIV test requirements, and adjusts all sub-systems of the basic sensing layer until PIV trace particles meeting the PIV test requirements are obtained;
s305, the control system generates stable PIV trace particles;
After the control system reaches a steady state, continuously generating PIV tracer particles meeting PIV test requirements, and simultaneously, automatically adjusting the opening of an electric regulating valve of each subsystem of the basic sensing layer to ensure that stable PIV tracer particles are generated;
S306, controlling the treatment before the shutdown of the system;
after the PIV test is finished, the upper computer operation interface clicks a shutdown button;
The control system closes the regulating valve of the medium-pressure nitrogen source;
the control system closes the regulating valve of the low-temperature nitrogen source;
The control system automatically starts an electric tracing band of the particle transmission pipeline, heats the particle transmission pipeline, and keeps the particle transmission pipeline for 10 minutes;
The control system automatically turns on an electric heater in the liquid nitrogen flash tank to heat and raise the temperature of residual liquid nitrogen, and the residual liquid nitrogen is kept for 10 minutes;
drying and purging for 10 minutes by a control system;
The control system closes an electric gate valve at the rear end of the particle transmission pipeline, an electric valve of the medium-pressure nitrogen source, an electric tracing band of the particle transmission pipeline and an electric heater in the liquid nitrogen flash tank;
the upper computer operation interface displays the shutdown completion;
manually closing all manual valves to full closure;
s40, controlling the system to be shut down;
Closing an upper computer of the control system;
closing a power supply in the PLC control cabinet, and closing a power supply of a control system;
Turning off a UPS host in the PLC control cabinet, and turning off the UPS;
s50, controlling the system to stop in an emergency;
An emergency stop button is respectively arranged on an operation interface of the upper computer and a cabinet door of the control cabinet, and the control system simultaneously closes all the electric valves, the electric regulating valves and all auxiliary devices when in emergency stop by one key under the emergency condition;
After the control system is in emergency stop, an administrator restores and checks the control system, and after confirming that the error is free, the right password is input again on the operation interface of the upper computer, so that the emergency stop instruction is released.
The control system and the method for the low-temperature environment PIV clean particle generation and transmission system utilize purified water as a trace particle material, so that the pollution problem of conventional oily trace particles and solid trace particles to a low-temperature test environment heat insulation material is avoided, the generated ice particles are uniform in particle diameter, good in light scattering property, low in cost and controllable in concentration, the environment temperature of less than 180K can be met, and meanwhile, the low-temperature environment PIV test requirement with higher requirements on the trace particle pollution problem is met.
Drawings
FIG. 1 is a control system topology of a low temperature ambient PIV clean particle generation and delivery system;
FIG. 2 is a flow chart of a method for controlling a PIV clean particle generation and delivery system in a low temperature environment.
Detailed Description
The invention is described in detail below with reference to the drawings and examples.
The control system of the PIV clean particle generation and transmission system in the low-temperature environment comprises a basic sensing layer, a basic control layer, a network transmission layer and an application service layer which are arranged from bottom to top, wherein the layers are connected through pipelines, cables and networks;
The basic sensing layer comprises a normal pressure pipeline subsystem, a cooling air flow pipeline subsystem, a trace particle generator subsystem, a cooling mixing device and a particle transmission pipeline subsystem;
The basic control layer comprises a programmable controller CPU, a programmable controller expansion module, a touch screen, a switch, a signal isolator, an intermediate relay, a low-voltage circuit breaker, a button indicator light and an uninterruptible power supply;
the network transmission layer comprises an industrial electric port switch and a network cable;
The application service layer comprises an upper computer, system software, monitoring software and a database.
The normal pressure pipeline subsystem is connected with a medium pressure nitrogen source and a trace particle generator through a normal pressure gas source pipeline, and a manual valve, a filter, an electronic pressure regulating valve, a check valve, a temperature sensor and a pressure sensor are arranged on the normal pressure gas source pipeline;
The normal pressure pipeline subsystem introduces the medium pressure nitrogen of the medium pressure nitrogen source into the trace particle generator through the interface reserved in the test hall, is used for driving the trace particle generator and simultaneously is also used as driving airflow of PIV trace particle flow, and is also used for monitoring the medium pressure nitrogen at the front end of the particle generator, so that the temperature and the pressure of the medium pressure nitrogen entering the particle generator are both within the design range.
The cooling air flow pipeline is provided with a safety valve, a filter, an electric pressure regulating valve, a temperature sensor, a pressure sensor, a flow sensor and a liquid nitrogen flash tank;
the cooling air flow pipeline converts liquid nitrogen from a test site into cryogenic dry nitrogen and transmits the cryogenic dry nitrogen to the cooling mixing device as a cooling air source, and the specific process is as follows:
The liquid nitrogen of the cooling air flow pipeline is provided by a low-temperature nitrogen source of a test site, namely a liquid nitrogen tank, the pressurized gas of the cooling air flow pipeline is provided by a medium-pressure nitrogen source in a factory building, the cooling air flow pipeline sprays the liquid nitrogen into a liquid nitrogen flash tank to cool the normal-temperature medium-pressure nitrogen, the liquid nitrogen is mixed with the medium-pressure nitrogen in the liquid nitrogen flash tank to form the cryogenic dry nitrogen, and the cryogenic dry nitrogen enters a cooling mixing device through the cooling air flow pipeline.
The tracer particle generator subsystem is characterized in that a main body of the tracer particle generator subsystem is a tracer particle generator, a pressure sensor, a temperature transmitter, a check valve, an electric heater and a manual valve are arranged on the tracer particle generator, and the tracer particle generator subsystem generates a humid air flow in a tracer particle generator container through a Laskin nozzle, wherein the humid air flow contains air with average diameter of l mu m-3 mu m or normal-temperature near-saturated water vapor.
Further, the main body of the cooling mixing device is a cooling tank, and a temperature transmitter and a regulating valve are arranged on the cooling tank;
The wet air flow generated by the trace particle generator subsystem and the cryogenic dry nitrogen generated by the cooling air flow pipeline subsystem are mixed in a cooling tank of the cooling mixing device, water vapor particles in the wet air flow are instantaneously condensed into ice particles with the average diameter of l mu m to 3 mu m, and the ice particles are injected into an inner runner of the particle transmission pipeline subsystem as PIV trace particles through a heat insulation pipeline.
The particle transmission pipeline subsystem comprises a particle transmission pipeline, wherein a manual valve and an electric valve are arranged on the particle transmission pipeline, and the particle transmission pipeline subsystem transmits PIV trace particles generated by the cooling mixing device into an inner flow path of the low-temperature test device.
As shown in fig. 2, the control method of the low-temperature environment PIV clean particle generation and transmission system of the present embodiment includes the following steps:
S10, checking by a control system;
the administrator checks and confirms that the instrument cable, the control cable, the power cable and the aviation plug are connected correctly and have perfect functions;
After an administrator checks that all the electric valves are closed, all the manual valves needing to be opened in advance are opened to be fully opened manually;
the administrator checks all the mechanical pointer tables to ensure that the mechanical pointer tables are intact and the readings are within the set normal range;
manually recording an inspection result after the inspection of the manager is completed;
s20, self-checking by a control system;
powering up a control system;
starting up an upper computer of the control system, logging in a correct user name, and entering an operation interface;
the control system performs self-checking to determine that the medium-pressure nitrogen pressure is within a set range;
the control system performs self-checking to determine that the medium-pressure nitrogen temperature is within a set range;
The control system self-tests to determine that the liquid nitrogen pressure is within a set range;
the control system performs self-checking to determine that the liquid level in the trace particle generator is in a set range;
the control system performs self-checking to determine that the temperature of the liquid in the trace particle generator is within a set range;
The control system is ready to complete;
S30, performing PIV test;
s301, controlling a system to dry and purge;
Clicking a drying purge start button on an operation interface of the upper computer;
The control system starts a medium-pressure nitrogen source main valve;
the control system opens the regulating valve of the medium-pressure nitrogen source by 50%;
the control system opens the regulating valve of the low-temperature nitrogen source by 50%;
the control system starts an electric gate valve of the particle transmission pipeline to dry and purge the particle transmission pipeline;
After the drying and purging time reaches the set time, the control system closes the electric gate valve of the particle transmission pipeline, and then delays to close the medium-pressure nitrogen source main valve and the regulating valve of the medium-pressure nitrogen source;
Ending the drying and blowing;
s302, PIV test preparation;
The control system starts an electric heater of the trace particle generator, heats the water temperature to 60 ℃ and keeps the temperature continuously;
The control system adjusts the pressure at the rear end of the trace particle generator to 0.6MPa through an adjusting valve of a medium-pressure nitrogen source;
The control system adjusts the pressure at the rear end of the cooling tank to 0.55MPa through a regulating valve of a medium-pressure nitrogen source;
the control system opens an electric gate valve of the particle transmission pipeline;
S303, opening liquid nitrogen;
the control system opens an electric regulating valve of a liquid nitrogen tank conveying pipeline;
the control system determines that the temperature, the pressure and the flow of the liquid nitrogen tank conveying pipeline are within a design range;
the control system determines that the temperature and the pressure of the cooling airflow pipeline are within a design range;
The cryogenic dry nitrogen enters a cooling mixing device through a cooling airflow pipeline, and the flow stability of the cryogenic dry nitrogen is ensured;
S304, opening a Laskin nozzle;
the temperature of the cooling air flow pipeline is reduced to be within a set range, and the control system opens the electric regulating valve;
The control system starts an electric valve of a Laskin nozzle pipeline, dry nitrogen generates a humid air flow in a trace particle generator container through the Laskin nozzle, and the humid air flow contains air of water vapor particles with the average diameter of l mu m to 3 mu m or normal-temperature near-saturated water vapor;
Mixing the wet air flow generated by the trace particle generator subsystem and the cryogenic dry nitrogen generated by the cooling air flow pipeline subsystem in a cooling tank of a cooling mixing device, and instantly condensing water vapor particles in the wet air flow into ice particles with the average diameter of l mu m-3 mu m;
the control system detects whether the particle size and the concentration of the ice particles meet the PIV test requirements, and adjusts all sub-systems of the basic sensing layer until PIV trace particles meeting the PIV test requirements are obtained;
s305, the control system generates stable PIV trace particles;
After the control system reaches a steady state, continuously generating PIV tracer particles meeting PIV test requirements, and simultaneously, automatically adjusting the opening of an electric regulating valve of each subsystem of the basic sensing layer to ensure that stable PIV tracer particles are generated;
S306, controlling the treatment before the shutdown of the system;
after the PIV test is finished, the upper computer operation interface clicks a shutdown button;
The control system closes the regulating valve of the medium-pressure nitrogen source;
the control system closes the regulating valve of the low-temperature nitrogen source;
The control system automatically starts an electric tracing band of the particle transmission pipeline, heats the particle transmission pipeline, and keeps the particle transmission pipeline for 10 minutes;
The control system automatically turns on an electric heater in the liquid nitrogen flash tank to heat and raise the temperature of residual liquid nitrogen, and the residual liquid nitrogen is kept for 10 minutes;
drying and purging for 10 minutes by a control system;
The control system closes an electric gate valve at the rear end of the particle transmission pipeline, an electric valve of the medium-pressure nitrogen source, an electric tracing band of the particle transmission pipeline and an electric heater in the liquid nitrogen flash tank;
the upper computer operation interface displays the shutdown completion;
manually closing all manual valves to full closure;
s40, controlling the system to be shut down;
Closing an upper computer of the control system;
closing a power supply in the PLC control cabinet, and closing a power supply of a control system;
Turning off a UPS host in the PLC control cabinet, and turning off the UPS;
s50, controlling the system to stop in an emergency;
An emergency stop button is respectively arranged on an operation interface of the upper computer and a cabinet door of the control cabinet, and the control system simultaneously closes all the electric valves, the electric regulating valves and all auxiliary devices when in emergency stop by one key under the emergency condition;
After the control system is in emergency stop, an administrator restores and checks the control system, and after confirming that the error is free, the right password is input again on the operation interface of the upper computer, so that the emergency stop instruction is released.
Although embodiments of the invention have been disclosed in the foregoing description and illustrated in the drawings, it will be understood by those skilled in the art that the present invention is not limited to the specific details and illustrations of features and steps set forth herein, and that all features of the invention disclosed, or steps of the method or process, except for mutually exclusive features and/or steps, may be combined in any manner without departing from the principles of the invention.