Test device and test method for controlling high enthalpy flow by magnetic field

Abstract

The invention provides a test device and a test method for controlling high-enthalpy flow by a magnetic field, a magnetic field generating device in the test device is installed in an inner cavity of a test model, and the test model is installed in a test section of a pulse type high-enthalpy high-speed wind tunnel; the magnetic field generating device is a permanent magnet or pulse magnet device; the high-frequency pressure sensor is mounted on the shock tube and is connected with the pulse magnet equipment, the thermal infrared imager and the transient schlieren system through the sequential control device; after airflow in the shock tube passes through the high-frequency pressure sensor, a voltage signal of the high-frequency pressure sensor is transmitted to the pulse magnet equipment, the thermal infrared imager and the transient schlieren system through the time sequence control device, and the pulse magnet equipment is started to generate a pulse magnetic field; after the thermal infrared imager is controlled to be started, the surface temperature and heat flow of the model are measured; after the transient schlieren system is controlled to be started, a flow field structure is observed; and if the flow field structure and the heat flow do not meet the required values, the magnetic field generation device is adjusted to change the magnetic field intensity until the requirements are met.

Description

Technical Field

[0001] The invention belongs to the technical field of flow control tests, and in particular relates to a test device and a test method for controlling high enthalpy flow with a magnetic field. Background Art

[0002] When a high-speed aircraft flies at ultra-high speed, the gas around the aircraft will generate thousands or even tens of thousands of degrees of high temperature through shock wave compression and viscous retardation, causing the gas molecules to vibrate, dissociate, recombine and ionize, causing the so-called high-temperature real gas effect. For example, this flow phenomenon exists in space shuttles, spacecraft, Mars or other interstellar probes. For high-speed flight including high-temperature real gas effect, the high-temperature gas after the shock wave forms a weakly conductive plasma flow field, and the ionized gas environment also provides a direct working environment for the application of magnetic fields. The new round of high-speed technology also poses new challenges to the flight of aircraft in "extreme" environments and "extreme" power conditions. It faces a series of problems such as heat reduction, drag reduction, and control. As a new application in the field of thermal protection, magnetic control thermal protection technology has received much attention. However, magnetic field control of high enthalpy flow technology faces many complexities, including the complexity of magnetic field generation and control, the mechanism of interaction between magnetic field and fluid, and engineering implementation problems in practical applications.

[0003] The temperature of the area behind the shock wave at the leading edge of the head of a high-speed aircraft can reach thousands or even tens of thousands of degrees. The high-temperature gas behind the shock wave forms a weakly conductive plasma flow field. The ionized gas environment also provides a direct working environment for the application of magnetic fields. The conductive plasma flow field has a serious impact on the thermal environment and target characteristics of the aircraft. Traditional thermal management methods, such as passive thermal protection layers or limited active cooling systems, are effective to a certain extent, but they still have performance limitations under extreme conditions. Summary of the invention

[0004] In order to overcome the deficiencies in the prior art, the inventors have conducted intensive research and provided an experimental device and method for controlling high enthalpy flow with a magnetic field. The device and method create a desired magnetic field environment by generating a magnetic field outside the test model and changing the presence and size of the magnetic field. The characteristics of the flow field are precisely controlled by adjusting the intensity of the magnetic field. The characteristics of the high-temperature gas flow are improved and controlled by applying a magnetic field.

[0005] The technical solution provided by the present invention is as follows:

[0006] In a first aspect, an experimental device for controlling high enthalpy flow by magnetic field includes a high-frequency pressure sensor, a timing control device, an infrared thermal imager, a heat flow sensor, a transient schlieren system, and a magnetic field generating device;

[0007] The magnetic field generating device is installed in the inner cavity of the test model, and the test model is installed in the test section of the pulsed high-enthalpy high-speed wind tunnel; the magnetic field generating device is a permanent magnet or a pulsed magnet device, the permanent magnet is used to generate a constant magnetic field, and the pulsed magnet device is used to generate a pulsed magnetic field;

[0008] The high-frequency pressure sensor is installed on the shock tube of the pulsed high-enthalpy and high-speed wind tunnel, and is connected to the pulsed magnet equipment, infrared thermal imager and transient schlieren system through a timing control device; after the airflow in the shock tube passes through the high-frequency pressure sensor, the voltage signal of the high-frequency pressure sensor is transmitted to the pulsed magnet equipment, infrared thermal imager and transient schlieren system through the timing control device, and the pulsed magnet equipment is started to generate a pulsed magnetic field; after the infrared thermal imager is started under control, the surface temperature and heat flow of the model are measured; after the transient schlieren system is started under control, the flow field structure is observed; if the flow field structure and heat flow do not meet the required values, the magnetic field generating device is adjusted to change the magnetic field strength, and the test device is restarted until the requirements are met.

[0009] Furthermore, the pulse magnet device is a multi-coil structure, where dense coils are arranged at locations in the test model where strong magnetic fields are required; sparse coils are arranged at locations in the test model where weak magnetic fields are required; and where magnetic fields are not required, magnetic field shielding devices are used for shielding.

[0010] Furthermore, the pulse magnet device is a multi-coil structure wound with a copper-niobium alloy, and the pulse magnet device adopts a battery power supply.

[0011] Furthermore, the magnetic field shielding device is a shell structure made of non-magnetic material, which is fixed in the test model to shield the magnetic field.

[0012] Furthermore, when the magnetic field strength required by the test device is greater than 0.8-1T, a pulse magnet device is used as the magnetic field generating device; when the magnetic field strength required by the test device is less than 0.8-1T, a permanent magnet is used as the magnetic field generating device.

[0013] Furthermore, when the magnetic field generating device is a pulse magnet device, within the effective test time of 0.1ms to 10ms in a pulsed high-enthalpy high-speed wind tunnel, the steady-state magnetic field waveform generated by the pulsed magnetic field is stable, the magnetic field pulse width time is greater than 2ms, and the magnetic field change rate is less than 0.5%.

[0014] Furthermore, a heat flow sensor is installed on the test model to measure the surface temperature and heat flow of the test model.

[0015] Furthermore, the transient schlieren system includes a transient laser source, a high-speed camera and an image processing unit. The transient laser source is used to illuminate the self-luminous flow field, the high-speed camera is used to capture the flow field image, and the image processing unit is used to process the flow field image to extract the flow field velocity and density information.

[0016] In a second aspect, a test method for controlling high enthalpy flow by a magnetic field is provided, using the test device for controlling high enthalpy flow by a magnetic field as described in the first aspect, comprising:

[0017] A magnetic field generating device is selected according to the required magnetic field strength and installed in the inner cavity of the test model;

[0018] When the magnetic field generating device is a pulse magnet device, after the high-pressure and high-speed airflow in the shock tube passes through the high-frequency pressure sensor, the voltage signal of the high-frequency pressure sensor is transmitted to the pulse magnet device through the timing control device, and the pulse magnet device is started to generate a pulse magnetic field;

[0019] When the magnetic field generating device is a permanent magnet, a constant magnetic field is generated;

[0020] At the beginning of the test, the infrared thermal imager and the transient schlieren system are started under control. The infrared thermal imager and the heat flux sensor installed on the test model measure the surface temperature and heat flux of the model; the transient schlieren system observes the flow field structure; if the flow field structure and heat flux do not meet the required values, the magnetic field generating device is adjusted to change the magnetic field strength until the requirements are met.

[0021] The test device and test method for controlling high enthalpy flow by magnetic field provided by the present invention have the following beneficial effects:

[0022] (1) The present invention provides a test device and test method for controlling high enthalpy flow by magnetic field. A magnetic field generating device is installed in the inner cavity of the test model, a heat flow sensor is installed on the test model, and an infrared thermal imager and a transient schlieren system are arranged outside the magnetic field as flow field detection devices. A uniform magnetic field strength can be obtained within milliseconds. The flow field structure and the temperature and heat flow on the surface of the test model can be used to feedback whether the magnetic field strength is required, which is convenient for adjusting the test.

[0023] (2) The present invention provides a test device and test method for controlling high enthalpy flow by magnetic field. The magnetic field generating device is a pulse magnet device or a permanent magnet. The pulse magnet device is a multi-coil structure wound with a copper-niobium alloy. In the test model, dense coils are arranged at locations where a strong magnetic field is required; in the test model, sparse coils are arranged at locations where a weak magnetic field is required; and in locations where a magnetic field is not required, a magnetic field shielding device is used for shielding. According to the incoming flow environment, different magnetic field control technologies can be selected, and model locations with magnetic fields of different strengths can be selected to ensure that the required flow control effect is obtained.

[0024] (3) The present invention provides an experimental device and method for controlling high enthalpy flow with a magnetic field. Through a specific structural combination, it is possible to change the presence and size of a magnetic field in milliseconds to create a desired magnetic field environment, so as to improve and control the characteristics of a high-temperature gas flow by applying a magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of the experimental device for controlling high enthalpy flow by magnetic field;

[0026] Figure 2 A schematic diagram of the structure of the test model when the magnetic field generating device adopts a permanent magnet;

[0027] Figure 3 A schematic diagram of the structure of the test model when a pulse magnet device is used as the magnetic field generating device. DETAILED DESCRIPTION

[0028] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0029] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0030] The present invention provides a test device for controlling high enthalpy flow by magnetic field, such as Figure 1 As shown, it includes a high-frequency pressure sensor, a timing control device 5, an infrared thermal imager, a heat flow sensor, a transient schlieren system and a magnetic field generating device;

[0031] The magnetic field generating device is installed in the inner cavity of the test model 3, and the test model 3 is installed in the test section 4 of the pulse type high enthalpy high speed wind tunnel; the pulse type high enthalpy high speed wind tunnel is a wind tunnel with a nozzle outlet airflow velocity greater than 3 km / s and an effective test time greater than 10 microseconds and less than 100 milliseconds; the magnetic field generating device is a permanent magnet 7 or a pulse magnet device 8, the permanent magnet 7 is used to generate a constant magnetic field, and the pulse magnet device 8 is used to generate a pulse magnetic field, see Figure 2 and Figure 3 ;

[0032] The high-frequency pressure sensor is installed on the shock tube 1 of the pulsed high-enthalpy and high-speed wind tunnel, with a frequency greater than 2MHz, and is connected to the pulsed magnet device 8, the infrared thermal imager and the transient schlieren system through the timing control device 5; the heat flux sensor is installed on the test model 3; after the high-pressure and high-speed airflow in the shock tube 1 passes through the high-frequency pressure sensor, the voltage signal of the high-frequency pressure sensor is transmitted to the pulsed magnet device 8, the infrared thermal imager and the transient schlieren system through the timing control device 5, and the pulsed magnet device 8 is started to generate a pulsed magnetic field; after the infrared thermal imager is controlled to be started, the surface temperature and heat flux of the test model are measured with the heat flux sensor installed on the test model 3; after the transient schlieren system is controlled to be started, the flow field structure is observed; if the flow field structure and the heat flux do not meet the required values, the magnetic field generating device is adjusted to change the magnetic field strength, and the test device is restarted until the requirements are met.

[0033] In the present invention, the pulse magnet device 8 is a multi-coil structure, and the coil material is a high-strength, high-conductivity copper-niobium alloy. In order to obtain a long magnetic field pulse width, the magnetic field power supply adopts a battery power supply. The multi-coil structure is arranged in the test model 3 and fixed in the test model 3 by a polytetrafluoroethylene ring. Furthermore, the electromagnetic coils installed in the test model 3 have different densities. In the test model 3, where a strong magnetic field is required, a dense coil is arranged; in the test model 3, where a weak magnetic field is required, a sparse coil is arranged; and in the place where a magnetic field is not required, a magnetic field shielding device 6 is used for shielding.

[0034] The magnetic field shielding device is a shell with high magnetic permeability and high resistance, and the material is non-magnetic material, such as aluminum alloy or high molecular polymer. The shell is fixed to the model by non-magnetic buckles.

[0035] If the magnetic field strength required for the test is greater than (0.8~1)T, a pulse magnet device 8 is used. After the pulse high enthalpy and high-speed wind tunnel is started, the high-frequency pressure sensor installed on the shock tube 1 transmits a trigger signal to the pulse magnet device 8. The pulse magnet device 8 is started to generate a pulse magnetic field, and the airflow flows through the test model 3 with a strong magnetic field to carry out the test.

[0036] If the magnetic field strength required for the test is less than (0.8-1) T, a permanent magnet 7 is used. After the pulsed high-enthalpy and high-speed wind tunnel is started, the airflow flows through the test model 3 equipped with the permanent magnet 7 to carry out the test.

[0037] The pulse magnet device 8 / permanent magnet 7 is installed inside the test model 3. It is necessary to use an electromagnetic field measuring device to measure the magnetic field intensity on the surface of the test model 3 and its change over time after the pulse magnet device 8 is started; or use an electromagnetic field measuring device to measure the magnetic field intensity on the surface of the test model 3 after the permanent magnet 7 is installed. In order to accurately capture and analyze the dynamic changes of the electromagnetic field, the time resolution of the electromagnetic field measuring device is nanoseconds.

[0038] In the present invention, when the magnetic field generating device is a pulse magnet device 8, the pulse magnetic field time needs to match the test time of the pulse-type high-enthalpy high-speed wind tunnel. Within the effective test time of 0.1ms to 10ms of the pulse-type high-enthalpy high-speed wind tunnel, the steady-state magnetic field waveform generated by the pulse magnetic field is stable, the magnetic field pulse width time is greater than 2ms, and the magnetic field change rate is less than 0.5%.

[0039] In the present invention, the heat flow sensor is a resistance type heat flow sensor, the principle of which is that the change of ambient temperature causes the change of resistance R(T), generates an electrical signal, and obtains the heat flow q(t).

[0040] The temperature change around the heat flow sensor causes the resistance R(T) to change:

[0041] R(T)=R O [1+α CR(T(t)-T O )] (1)

[0042] Among them, α CR is the resistance temperature coefficient, R0 is the initial resistance, T(t) is the real-time temperature at time t, and T0 is the initial temperature.

[0043] During the measurement process, a constant current is passed through the heat flow sensor, and the potential difference across the resistor is:

[0044] E(t)=α CR E0T(t) (2)

[0045] Where E0 is the initial potential;

[0046] The heat flux q(t) on the surface of the test model is:

[0047]

[0048] Where ρ is the density, c is the specific heat, k is the thermal conductivity, and τ is the time variable.

[0049] In the present invention, an optical window is opened on the test section 4 and sealed by glass. The infrared thermal imager and the transient schlieren system are located outside the optical window to monitor the temperature, heat flow and flow field structure of the surface of the test model 3 respectively.

[0050] The present invention adopts the method of infrared thermal imager to measure the surface temperature and heat flow of the test model. The start signal comes from the high-frequency pressure sensor on the shock tube and is transmitted to the infrared thermal imager through the timing control device. The acquisition frequency of the infrared thermal imager is greater than 1kHz. In order to accurately measure the surface temperature of the test model, when the infrared thermal imager is calibrated, if the measurement area is a circular area, the entire display interface of the infrared thermal imager is divided into an annular equivalent area; if the measurement area is a columnar area, the entire display interface of the infrared thermal imager is divided into a strip equivalent area.

[0051] In the present invention, a transient schlieren system observes the flow field structure, and a start signal comes from a high-frequency pressure sensor on a shock tube and is transmitted to the transient schlieren system through a timing control device; the transient schlieren system includes: a transient laser source, a high-speed camera and an image processing unit, wherein the transient laser source is used to illuminate the self-luminous flow field, a high-speed camera is used to capture the flow field image, and the image processing unit is used to process the flow field image to extract the flow field velocity and density information.

[0052] The optical flow algorithm is used to estimate the movement of feature points in the image over time. The optical flow algorithm is based on the principle of brightness conservation and calculates the flow field velocity by comparing the position changes of feature points in consecutive image frames. The brightness conservation principle in the optical flow algorithm can be expressed by the following formula:

[0053] L(x,y,t)=L(x+Δ(x),y+Δ(y),Δt) (4)

[0054] Among them, L(x,y,t) is the pixel brightness at position (x,y) and time t in the image sequence, Δx and Δy are the displacement of the feature point in space, and Δt is the displacement in time.

[0055] The flow field velocity is: Vx=Δx / Δt, Vy=Δy / Δt.

[0056] The present invention also provides an experimental method for controlling high enthalpy flow by a magnetic field, comprising the following steps:

[0057] A magnetic field generating device is selected according to the required magnetic field strength and installed in the inner cavity of the test model 3;

[0058] When the magnetic field generating device is a pulse magnet device 8, after the high-pressure and high-speed airflow in the shock tube 1 passes through the high-frequency pressure sensor, the voltage signal of the high-frequency pressure sensor is transmitted to the pulse magnet device 8 through the timing control device 5, and the pulse magnet device 8 is started to generate a pulse magnetic field;

[0059] When the magnetic field generating device is a permanent magnet 7, a constant magnetic field is generated;

[0060] At the beginning of the test, the infrared thermal imager and the transient schlieren system are started under control. The infrared thermal imager and the heat flux sensor installed on the test model 3 measure the surface temperature and heat flux of the model; the transient schlieren system observes the flow field structure; if the flow field structure and heat flux do not meet the required values, the magnetic field generating device is adjusted to change the magnetic field strength until the requirements are met.

[0061] The functions and technical parameters of each structural component in the test method are consistent with those in the experimental device and will not be repeated here.

[0062] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0063] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A test device for controlling high enthalpy flow by magnetic field, characterized in that: It includes a high-frequency pressure sensor, a timing control device, an infrared thermal imager, a heat flow sensor, a transient schlieren system and a magnetic field generating device; The magnetic field generating device is installed in the inner cavity of the test model, and the test model is installed in the test section of the pulsed high-enthalpy high-speed wind tunnel; the magnetic field generating device is a permanent magnet or a pulsed magnet device, the permanent magnet is used to generate a constant magnetic field, and the pulsed magnet device is used to generate a pulsed magnetic field; The high-frequency pressure sensor is installed on the shock tube of the pulsed high-enthalpy high-speed wind tunnel, and is connected to the pulsed magnet device, infrared thermal imager and transient schlieren system through a timing control device; after the airflow in the shock tube passes through the high-frequency pressure sensor, the voltage signal of the high-frequency pressure sensor is transmitted to the pulsed magnet device, infrared thermal imager and transient schlieren system through the timing control device, and the pulsed magnet device is started to generate a pulsed magnetic field; after the infrared thermal imager is controlled to start, the surface temperature and heat flow of the model are measured; After the transient schlieren system is started under control, the flow field structure is observed; if the flow field structure and heat flux do not meet the required values, the magnetic field generating device is adjusted to change the magnetic field strength, and the test device is restarted until the requirements are met.

2. The test device for controlling high enthalpy flow by magnetic field according to claim 1, characterized in that: The pulse magnet device is a multi-coil structure. In the locations where a strong magnetic field is required in the test model, dense coils are arranged; in the locations where a weak magnetic field is required in the test model, sparse coils are arranged; and in the locations where a magnetic field is not required, a magnetic field shielding device is used for shielding.

3. The test device for controlling high enthalpy flow by magnetic field according to claim 2, characterized in that: The pulse magnet device is a multi-coil structure wound with a copper-niobium alloy.

4. The test device for controlling high enthalpy flow by magnetic field according to claim 2, characterized in that: The pulse magnet device is powered by a battery.

5. The test device for controlling high enthalpy flow by magnetic field according to claim 2, characterized in that: The magnetic field shielding device is a shell structure made of non-magnetic material and is fixed in the test model to shield the magnetic field.

6. The test device for controlling high enthalpy flow by magnetic field according to claim 1, characterized in that: When the magnetic field strength required by the test device is greater than 0.8-1T, a pulse magnet device is used as the magnetic field generating device; when the magnetic field strength required by the test device is less than 0.8-1T, a permanent magnet is used as the magnetic field generating device.

7. The test device for controlling high enthalpy flow by magnetic field according to claim 1, characterized in that: When the magnetic field generating device is a pulse magnet device, within the effective test time of 0.1ms to 10ms in a pulsed high-enthalpy high-speed wind tunnel, the steady-state magnetic field waveform generated by the pulsed magnetic field is stable, the magnetic field pulse width time is greater than 2ms, and the magnetic field change rate is less than 0.5%.

8. The test device for controlling high enthalpy flow by magnetic field according to claim 1, characterized in that: A heat flow sensor is installed on the test model to measure the surface temperature and heat flow of the test model.

9. The test device for controlling high enthalpy flow by magnetic field according to claim 1, characterized in that: The transient schlieren system includes a transient laser source, a high-speed camera and an image processing unit. The transient laser source is used to illuminate the self-luminous flow field, the high-speed camera is used to capture the flow field image, and the image processing unit is used to process the flow field image to extract the flow field velocity and density information.

10. An experimental method for controlling high enthalpy flow by magnetic field, characterized in that: An experimental device for controlling high enthalpy flow using a magnetic field according to any one of claims 1 to 9, comprising: A magnetic field generating device is selected according to the required magnetic field strength and installed in the inner cavity of the test model; When the magnetic field generating device is a pulse magnet device, after the high-pressure and high-speed airflow in the shock tube passes through the high-frequency pressure sensor, the voltage signal of the high-frequency pressure sensor is transmitted to the pulse magnet device through the timing control device, and the pulse magnet device is started to generate a pulse magnetic field; When the magnetic field generating device is a permanent magnet, a constant magnetic field is generated; At the beginning of the test, the infrared thermal imager and the transient schlieren system are started under control. The infrared thermal imager and the heat flux sensor installed on the test model measure the surface temperature and heat flux of the model; the transient schlieren system observes the flow field structure; if the flow field structure and heat flux do not meet the required values, the magnetic field generating device is adjusted to change the magnetic field strength until the requirements are met.

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