CN106950031B - Liquid nitrogen jetting device of continuous high-speed wind tunnel cooling system - Google Patents
Liquid nitrogen jetting device of continuous high-speed wind tunnel cooling system Download PDFInfo
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Abstract
The invention provides a liquid nitrogen injection device of a continuous high-speed wind tunnel cooling system, which comprises a liquid collecting ring, an upstream liquid nitrogen nozzle group and a downstream liquid nitrogen nozzle group, wherein the upstream liquid nitrogen nozzle group is connected with the downstream liquid nitrogen nozzle group; the liquid nitrogen injection device is arranged in the liquid nitrogen injection experimental section; the liquid collecting ring is an annular low-temperature-resistant stainless steel pipeline, the inner diameter of the liquid collecting ring is the same as the outer diameter of the experimental section hole wall at the installation position, and the liquid collecting ring is annularly arranged on the experimental section hole wall and used for receiving low-temperature liquid nitrogen from the main pipeline and conveying the liquid nitrogen to the liquid nitrogen nozzle group; the upstream liquid nitrogen nozzle group and the downstream liquid nitrogen nozzle group are distributed in parallel along the axis of the wind tunnel airflow, the distance between the upstream liquid nitrogen nozzle group and the upstream end face of the experimental section is 0.61d, the distance between the downstream liquid nitrogen nozzle group and the upstream end face of the experimental section is 1.72d, and d is the inner diameter of the upstream end face of the experimental section. The liquid nitrogen injection device provided by the invention is well matched with the whole cooling system of the wind tunnel, and by adopting the technical scheme, a support is provided for building the first continuous high-speed wind tunnel cooling system in China.
Description
Technical Field
The invention relates to the field of design of a low-temperature liquid injection technology of a closed container, in particular to a liquid nitrogen injection device for a continuous high-speed wind tunnel cooling system.
Background
The Reynolds number is an important similar parameter for simulating the actual flight capability of the aircraft in the wind tunnel experiment. The difference between the experimental Reynolds number and the flying Reynolds number can cause the aerodynamic characteristics such as transition, separation position, shock wave position and strength of the boundary layer obtained by the experiment to form obvious difference with the actual flying state, so that the engineering application value of the experimental data is greatly reduced, and the experimental data can not be used even under certain conditions. Theoretically, in order to make a wind tunnel experiment completely simulate a real flight state, the reynolds numbers of the wind tunnel experiment and the actual flight must be kept consistent. However, due to the limitation of factors such as model size, wind tunnel power equipment, energy system and the like, the Reynolds number of the current wind tunnel experiment cannot reach the actual Reynolds number, and the development of the wind tunnel with the high Reynolds number has important strategic significance and engineering application value for the development of the aviation industry and the national defense science and technology in China.
The continuous high-speed wind tunnel is a backflow high-speed aerodynamic experiment platform driven by an axial flow compressor and capable of continuously operating for a long time, and the flow field quality and the experiment efficiency of the continuous high-speed wind tunnel are far higher than those of the conventional temporary-rush wind tunnel. However, the continuous high-speed wind tunnel is driven by a high-power motor and limited by an energy system, and the Reynolds number of an experimental section and the actual Reynolds number of flight have a certain difference, so that the requirements of model experiments of fighters and large high-speed civil aircrafts cannot be well met. The Reynolds number is determined by the density, the temperature, the speed and the model size of the fluid, and the speed and the model size of the fluid are not easy to change under the restriction of the inherent conditions of the wind tunnel; supercharging is a feasible way to increase the number of reynolds, but the demand on power is higher; the fluid density can be increased and the viscosity coefficient can be reduced by cooling, and the method is an effective way for improving the experimental Reynolds number. At present, china has precedent in the aspect of low-temperature temporary-rush wind tunnels, but is blank in the aspect of low-temperature continuous high-speed wind tunnels. Therefore, in order to further widen the range of the experimental Reynolds number of the wind tunnel, aiming at the structural characteristics and the operation mode of the continuous high-speed wind tunnel, the cooling operation of the continuous high-speed wind tunnel can be realized by spraying liquid nitrogen in a mode of not changing the size of an experimental section, fluid media and pressure and utilizing the gasification heat absorption effect of the liquid nitrogen, thereby achieving the purpose of improving the experimental Reynolds number.
The continuous high-speed wind tunnel cooling system consists of five subsystems, namely a liquid nitrogen storage device, a gas supply and distribution system, a measurement system, a control system and a liquid nitrogen injection device, wherein the liquid nitrogen injection device is a key component of the whole cooling system and is used for uniformly and controllably injecting liquid nitrogen from a main pipeline into the wind tunnel. The liquid nitrogen has the characteristics of ultralow temperature, fast evaporation and large expansion coefficient, the continuous high-speed wind tunnel is a steel closed container, and the problems of frost cracking, overpressure and the like of metal materials are easily caused in the spraying process of the liquid nitrogen, so that a set of liquid nitrogen injection device suitable for a continuous high-speed wind tunnel cooling system needs to be developed, and safe and efficient technical guarantee is provided for the liquid nitrogen spraying link of the cooling system.
Disclosure of Invention
Aiming at the physical characteristics of ultralow temperature, quick evaporation and large expansion coefficient of liquid nitrogen, aiming at solving the technical problems of easy frost cracking, overpressure and the like of metal materials of a wind tunnel body in the process of spraying the liquid nitrogen, establishing a safe and efficient liquid nitrogen spraying technical means for a cooling system, and providing a set of liquid nitrogen injection device for a continuous high-speed wind tunnel cooling system according to the structural characteristics and the operation mode of the continuous high-speed wind tunnel.
The technical scheme of the invention is as follows:
the liquid nitrogen injection device of the continuous high-speed wind tunnel cooling system is characterized in that: the liquid collecting ring is arranged on the upstream liquid nitrogen nozzle group; the liquid nitrogen injection device is arranged in the liquid nitrogen injection experimental section; the liquid collecting ring is an annular low-temperature-resistant stainless steel pipeline, the inner diameter of the liquid collecting ring is the same as the outer diameter of the experimental section hole wall at the installation position, and the liquid collecting ring is annularly arranged on the experimental section hole wall and used for receiving low-temperature liquid nitrogen from the main pipeline and conveying the liquid nitrogen to the liquid nitrogen nozzle group;
the upstream liquid nitrogen nozzle group comprises a plurality of upstream ultralow-temperature high-pressure tail end electromagnetic valves, a plurality of upstream liquid nitrogen nozzles and a plurality of upstream support pipelines, and the number of the upstream ultralow-temperature high-pressure tail end electromagnetic valves, the number of the upstream liquid nitrogen nozzles and the number of the upstream support pipelines are the same; the plurality of upstream liquid nitrogen nozzles are uniformly distributed along the outer circumference of the experimental section hole wall, receive liquid nitrogen from the liquid collecting ring through an upstream support pipeline and spray the liquid nitrogen into the wind tunnel under the control of an upstream ultralow-temperature high-pressure tail end electromagnetic valve;
the downstream liquid nitrogen nozzle group comprises a plurality of downstream ultralow-temperature high-pressure tail end electromagnetic valves, a plurality of downstream liquid nitrogen nozzles and a plurality of downstream support pipelines, and the number of the downstream ultralow-temperature high-pressure tail end electromagnetic valves, the number of the downstream liquid nitrogen nozzles and the number of the downstream support pipelines are the same; the downstream liquid nitrogen nozzles are uniformly distributed along the outer circumference of the experimental section hole wall, receive liquid nitrogen from the liquid collecting ring through a downstream support pipeline and spray the liquid nitrogen into the wind tunnel under the control of a downstream ultralow-temperature high-pressure tail end electromagnetic valve;
the upstream liquid nitrogen nozzle group and the downstream liquid nitrogen nozzle group are distributed in parallel along the axis of the air flow of the wind tunnel, the distance between the upstream liquid nitrogen nozzle group and the upstream end face of the experimental section is 0.61d, the distance between the downstream liquid nitrogen nozzle group and the upstream end face of the experimental section is 1.72d, and d is the inner diameter of the upstream end face of the experimental section.
Further preferred scheme, the liquid nitrogen injection device of the continuous high-speed wind tunnel cooling system is characterized in that: the upstream liquid nitrogen nozzle group consists of 16 upstream ultralow-temperature high-pressure tail end electromagnetic valves, 16 upstream liquid nitrogen nozzles and 16 upstream support pipelines, and the 16 upstream liquid nitrogen nozzles are uniformly distributed along the outer circumference of the experimental section hole wall; the flow rate of the 16 upstream liquid nitrogen nozzles is 0.02kg/s, the flow rate of the 3 upstream liquid nitrogen nozzles is 0.12kg/s, the flow rate of the 6 upstream liquid nitrogen nozzles is 0.6kg/s, and the flow rate of the 4 upstream liquid nitrogen nozzles is 0.73kg/s under the pressure difference of 0.5 Mpa; 3 upstream liquid nitrogen nozzles with a flow rate of 0.02kg/s are respectively arranged at the positions of 0 degree, 135 degree and 225 degree of the upstream injection section observed along the reverse air flow direction, 3 upstream liquid nitrogen nozzles with a flow rate of 0.12kg/s are respectively arranged at the positions of 45 degrees, 180 degrees and 315 degrees of the upstream injection section observed along the reverse air flow direction, 6 upstream liquid nitrogen nozzles with a flow rate of 0.6kg/s are respectively arranged at the positions of 67.5 degrees, 112.5 degrees, 157.5 degrees, 247.5 degrees, 292.5 degrees and 337.5 degrees of the upstream injection section observed along the reverse air flow direction, and 4 upstream liquid nitrogen nozzles with a flow rate of 0.73kg/s are respectively arranged at the positions of 22.5 degrees, 90 degrees, 202.5 degrees and 270 degrees of the upstream injection section observed along the reverse air flow direction.
Further preferred scheme, the liquid nitrogen injection device of continuous high-speed wind tunnel cooling system is characterized in that: the downstream liquid nitrogen nozzle group consists of 16 downstream ultralow-temperature high-pressure tail end electromagnetic valves, 16 downstream liquid nitrogen nozzles and 16 downstream support pipelines, and the 16 downstream liquid nitrogen nozzles are uniformly distributed along the circumferential direction of the outer side of the experimental section hole wall; the 16 downstream liquid nitrogen nozzles are controlled by 0.5Mpa differential pressure, wherein the flow rate of 3 downstream liquid nitrogen nozzles is 0.02kg/s, the flow rate of 2 downstream liquid nitrogen nozzles is 0.12kg/s, the flow rate of 8 downstream liquid nitrogen nozzles is 0.6kg/s, and the flow rate of 3 downstream liquid nitrogen nozzles is 0.73kg/s;3 downstream liquid nitrogen nozzles with the flow rate of 0.02kg/s are respectively arranged at the positions of 45 degrees, 180 degrees and 315 degrees of the downstream injection section observed along the reverse air flow direction, 2 downstream liquid nitrogen nozzles with the flow rate of 0.12kg/s are respectively arranged at the positions of 90 degrees and 270 degrees of the downstream injection section observed along the reverse air flow direction, 8 downstream liquid nitrogen nozzles with the flow rate of 0.6kg/s are respectively arranged at the positions of 22.5 degrees, 67.5 degrees, 112.5 degrees, 157.5 degrees, 202.5 degrees, 247.5 degrees, 292.5 degrees and 337.5 degrees of the downstream injection section observed along the reverse air flow direction, and 3 downstream liquid nitrogen nozzles with the flow rate of 0.73kg/s are respectively arranged at the positions of 0 degrees, 135 degrees and 225 degrees of the downstream injection section observed along the reverse air flow direction.
Further preferred scheme, the liquid nitrogen injection device of the continuous high-speed wind tunnel cooling system is characterized in that: the front end of the support pipeline is connected to the liquid collecting ring through an expansion joint, the front end of the liquid nitrogen nozzle is connected to the tail end of the support pipeline through an ultralow-temperature high-pressure tail end electromagnetic valve, and the tail end of the liquid nitrogen nozzle is arranged on the wall of the experimental section hole; the ultralow temperature high-pressure tail end electromagnetic valve controls the opening and closing of the liquid nitrogen nozzle.
Advantageous effects
The liquid nitrogen injection device of the continuous high-speed wind tunnel cooling system is reasonable in design, fast atomization and uniform injection of liquid nitrogen are realized according to the inherent properties of ultralow temperature, fast evaporation and large expansion coefficient of the liquid nitrogen, and the problem that the ultralow temperature liquid nitrogen freezes and cracks a wind tunnel wall metal material is solved; by the integrated design of the annular distribution of the injection device and the nozzle of the electromagnetic valve, the accurate control of the flow and the pressure of the liquid nitrogen is realized, and the problems of over-temperature and over-pressure of the air flow in the wind tunnel are solved. The liquid nitrogen injection device is well matched with the whole cooling system of the wind tunnel, and by adopting the technical scheme, a support is provided for building the first continuous high-speed wind tunnel cooling system in China.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is an assembled relationship of a liquid nitrogen injection device;
1-a liquid collecting ring, 2-an upstream liquid nitrogen nozzle group, 3-a downstream liquid nitrogen nozzle group, 4-an expansion joint, 5-a support pipeline and 6-a wind tunnel wall.
FIG. 2 is an upstream liquid nitrogen nozzle distribution;
FIG. 3 is a downstream liquid nitrogen nozzle distribution;
FIG. 4 is a schematic view of the installation position of the liquid nitrogen nozzle group in the wind tunnel;
2-an upstream liquid nitrogen nozzle group, 3-a downstream liquid nitrogen nozzle group, 6-a wind tunnel wall, 7-a downstream section, 8-an upstream section and 9-an upstream end surface of the wind tunnel wall.
FIG. 5 is a schematic diagram of a liquid nitrogen nozzle assembly;
1-liquid collecting ring, 4-expansion joint, 10-ultralow temperature high-pressure tail end electromagnetic valve, 11-nozzle, 6-wind tunnel wall and 5-support pipeline.
FIG. 6 is a NF-6 continuous high-speed wind tunnel cooling system;
12-a wind tunnel body, 13-a liquid nitrogen storage device, 14-a gas supply and distribution system, 15-a control system and 16-a liquid nitrogen injection device.
FIG. 7 shows the variation of the wind tunnel airflow and tunnel wall temperature during the cooling test;
FIG. 8 is a graph showing the variation of parameters during a liquid nitrogen spray cooling test;
FIG. 9 is a graph showing the total temperature change during the cooling test.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on those shown in the drawings, merely for convenience of description and simplification of the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.
The embodiment is a set of liquid nitrogen injection device for an NF-6 continuous high-speed wind tunnel cooling system, wherein the NF-6 wind tunnel is the first continuous high-speed wind tunnel in China and is the only continuous high-speed wind tunnel which is put into operation at present in China. The overall performance of the wind tunnel reaches the advanced domestic and international levels. In order to verify the feasibility and the beneficial effects of the invention, a liquid nitrogen injection device of the NF-6 continuous high-speed wind tunnel cooling system is designed and developed by taking the NF-6 continuous high-speed wind tunnel as an implementation platform according to the overall scheme and the main technical requirements of the wind tunnel cooling system, and an operation test is carried out.
The liquid nitrogen injection device of the continuous high-speed wind tunnel cooling system in the embodiment comprises a liquid collecting ring 1, an upstream liquid nitrogen nozzle group 2 and a downstream liquid nitrogen nozzle group 3. The liquid nitrogen injection device is arranged in the liquid nitrogen injection experimental section; the liquid collecting ring is an annular low-temperature-resistant stainless steel pipeline, the inner diameter of the liquid collecting ring is the same as the outer diameter of the experimental section hole wall at the installation position, and the liquid collecting ring is annularly arranged on the experimental section hole wall and used for receiving low-temperature liquid nitrogen from the main pipeline and conveying the liquid nitrogen to the liquid nitrogen nozzle group, as shown in figure 1.
The upstream liquid nitrogen nozzle group consists of 16 upstream ultralow-temperature high-pressure tail end electromagnetic valves, 16 upstream liquid nitrogen nozzles and 16 upstream support pipelines, wherein the 16 upstream liquid nitrogen nozzles are uniformly distributed along the outer circumference of the experimental section hole wall, receive liquid nitrogen from the liquid collecting ring through the upstream support pipelines, and spray the liquid nitrogen into the wind tunnel under the control of the upstream ultralow-temperature high-pressure tail end electromagnetic valves. The 16 upstream liquid nitrogen nozzles are controlled by 0.5Mpa differential pressure, wherein the flow rate of 3 upstream liquid nitrogen nozzles is 0.02kg/s, the flow rate of 3 upstream liquid nitrogen nozzles is 0.12kg/s, the flow rate of 6 upstream liquid nitrogen nozzles is 0.6kg/s, and the flow rate of 4 upstream liquid nitrogen nozzles is 0.73kg/s; as shown in FIG. 2, 3 upstream liquid nitrogen nozzles with a flow rate of 0.02kg/s were respectively installed at the 0 °, 135 °, 225 ° positions of the upstream injection section viewed in the counter-air flow direction, 3 upstream liquid nitrogen nozzles with a flow rate of 0.12kg/s were respectively installed at the 45 °, 180 °, 315 ° positions of the upstream injection section viewed in the counter-air flow direction, 6 upstream liquid nitrogen nozzles with a flow rate of 0.6kg/s were respectively installed at the 67.5 °, 112.5 °, 157.5 °, 247.5 °, 292.5 °, 337.5 ° positions of the upstream injection section viewed in the counter-air flow direction, and 4 upstream liquid nitrogen nozzles with a flow rate of 0.73kg/s were respectively installed at the 22.5 °, 90 °, 202.5 °, 270 ° positions of the upstream injection section viewed in the counter-air flow direction.
The downstream liquid nitrogen nozzle group consists of 16 downstream ultralow-temperature high-pressure tail end electromagnetic valves, 16 downstream liquid nitrogen nozzles and 16 downstream support pipelines, wherein the 16 downstream liquid nitrogen nozzles are uniformly distributed along the circumferential direction of the outer side of the experimental section hole wall, receive liquid nitrogen from the liquid collecting ring through the downstream support pipelines, and spray the liquid nitrogen into the wind tunnel under the control of the downstream ultralow-temperature high-pressure tail end electromagnetic valves. The 16 downstream liquid nitrogen nozzles are controlled by 0.5Mpa differential pressure, wherein the flow rate of 3 downstream liquid nitrogen nozzles is 0.02kg/s, the flow rate of 2 downstream liquid nitrogen nozzles is 0.12kg/s, the flow rate of 8 downstream liquid nitrogen nozzles is 0.6kg/s, and the flow rate of 3 downstream liquid nitrogen nozzles is 0.73kg/s; as shown in FIG. 3, 3 downstream liquid nitrogen nozzles with a flow rate of 0.02kg/s were respectively installed at 45 °, 180 °, 315 ° positions of the downstream injection section viewed in the counter-air flow direction, 2 downstream liquid nitrogen nozzles with a flow rate of 0.12kg/s were respectively installed at 90 °, 270 ° positions of the downstream injection section viewed in the counter-air flow direction, 8 downstream liquid nitrogen nozzles with a flow rate of 0.6kg/s were respectively installed at 22.5 °, 67.5 °, 112.5 °, 157.5 °, 202.5 °, 247.5 °, 292.5 °, 337.5 ° positions of the downstream injection section viewed in the counter-air flow direction, and 3 downstream liquid nitrogen nozzles with a flow rate of 0.73kg/s were respectively installed at 0 °, 135 °, 225 ° positions of the downstream injection section viewed in the counter-air flow direction.
The upstream liquid nitrogen nozzle group and the downstream liquid nitrogen nozzle group are distributed in parallel along the axis of the air flow of the wind tunnel, the distance between the upstream liquid nitrogen nozzle group and the upstream end face of the experimental section is 0.61d, the distance between the downstream liquid nitrogen nozzle group and the upstream end face of the experimental section is 1.72d, and d is the inner diameter of the upstream end face of the experimental section. In this embodiment, d =1800mm, as shown in fig. 4, the upstream liquid nitrogen nozzle group is 1100mm away from the upstream end face of the wind tunnel wall, and the downstream liquid nitrogen nozzle group is 3100mm away from the upstream end face of the wind tunnel wall.
The assembly relationship of the liquid collecting ring, the ultralow temperature high pressure tail end electromagnetic valve, the liquid nitrogen nozzle, the expansion joint and the support pipeline is shown in figure 5. The front end of the support pipeline is connected to the liquid collecting ring through an expansion joint, and the expansion joint is used for adjusting the positions of the nozzle device and the experimental section hole wall mounting hole; the front end of a liquid nitrogen nozzle is connected to the tail end of the support pipeline through an ultralow-temperature high-pressure tail end electromagnetic valve, and the tail end of the liquid nitrogen nozzle is arranged on the wall of the experimental section hole; the ultralow temperature high-pressure tail end electromagnetic valve is used for controlling the opening and closing of the liquid nitrogen nozzle, the highest working pressure is 3MPa, and single-action or combined group action at will can be completed, so that the regulation of liquid nitrogen injection flow is realized.
As shown in FIG. 6, the NF-6 continuous high-speed wind tunnel cooling system is composed of a wind tunnel body 12, a liquid nitrogen storage device 13, a gas supply and distribution system 14, a control system 15 and a liquid nitrogen injection device 16, wherein the liquid nitrogen injection device is used for supplying and injecting liquid nitrogen. The liquid nitrogen injection device is arranged on 2 annular sections of a fourth diffusion section (downstream of the axial flow compressor) of the wind tunnel, the number of the two groups of nozzles is 32, the pressure drop of the nozzles is 0.5-2.5 MPa, the tail end ultralow temperature electromagnetic valve group is used for accurately controlling the flow of liquid nitrogen injected into the wind tunnel, and when the front-back pressure difference of the nozzles is higher than 0.6MPa, the injection amount of the liquid nitrogen can be larger than 16.0kg/s. The test results of the operation of the liquid nitrogen injection device and the integral cooling system are as follows:
and (3) running and testing of a liquid nitrogen injection device:
tests show that all 32 ultralow-temperature electromagnetic valves are opened and closed quickly, and single-action or combined action in any combination can be completed. The selection and grouping of the nozzles are shown in tables 1 and 2, and the injection amount of liquid nitrogen under different pressure differences is shown in table 2. It can be seen that when the pressure difference between the front and the rear of the nozzle is more than 8bar, the liquid nitrogen injection amount injected into the wind tunnel by the injection device is more than 18.0kg/s, and the liquid nitrogen injection amount requirement of the NF-6 continuous high-speed wind tunnel cooling system is met.
TABLE 1 selection and grouping of liquid nitrogen nozzles
| Serial number | Flow (kg/s) | Design point pressure difference (Bar) | Number of |
| 1# | 0.02 | 5 | 6 |
| 2# | 0.12 | 5 | 5 |
| 3# | 0.6 | 5 | 14 |
| 4# | 0.73 | 5 | 7 |
TABLE 2 amount of injected liquid nitrogen at different differential pressures
Fig. 7 shows the variation of the temperature of the wind tunnel airflow and the tunnel wall during the temperature drop test, when the temperature of the airflow in the stable section is lower than-20 ℃, the temperature of the tunnel wall of the wind tunnel at the injection ring is still near 20 ℃ of the normal temperature, and although the temperature of the tunnel wall has a downward trend within a time period of 90s, the temperature is about 1 ℃, which indicates that no liquid nitrogen drips on the wind tunnel wall, thereby realizing the rapid atomization and uniform injection of the liquid nitrogen and effectively solving the ultralow temperature frost cracking problem of the material of the tunnel wall.
And (3) overall operation test of the wind tunnel cooling system:
after the construction of other subsystems is completed, the overall operation and test of the wind tunnel cooling system are carried out, the total pressure of the wind tunnel adopts closed-loop control, and the incoming flow wind speed is set to be M =0.5. Fig. 8 shows the change curves of the total temperature, the total pressure and the mach number in the whole cooling test process, fig. 9 shows the change situation of the total temperature of the stable section of the wind tunnel, and the test result shows that:
1) The liquid nitrogen injection device is well matched with other subsystems, and the wind tunnel cooling system works normally and runs stably;
2) The cooling system is well compatible with the original measuring and controlling system of the wind tunnel, and the total pressure and Mach number control of the wind tunnel is not obviously influenced;
3) The average value of 9 total temperature measuring points in the test section reaches-20 ℃, and the requirement is met
4) The average value of the number of the test section Ma reaches 0.5, the Mach number deviation is | Delta Ma | < 0.003, and the requirement of sigma is met Ma ≤0.003；
5) The average value of the total pressure of the stable section is 1.022bar, and the variation amplitude of the total pressure of the stable section meets the requirement
6) The effective time of the cooling operation of the wind tunnel exceeds 90s, and the design requirement is met.
Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are exemplary and not to be construed as limiting the present invention, and that those skilled in the art may make variations, modifications, substitutions and alterations within the scope of the present invention without departing from the spirit and scope of the present invention.
Claims (2)
1. A liquid nitrogen injection device of a continuous high-speed wind tunnel cooling system is characterized in that: the liquid collecting ring is arranged on the upstream liquid nitrogen nozzle group; the liquid nitrogen injection device is arranged in the liquid nitrogen injection experimental section; the liquid collecting ring is an annular low-temperature-resistant stainless steel pipeline, the inner diameter of the liquid collecting ring is the same as the outer diameter of the experimental section hole wall at the installation position, and the liquid collecting ring is annularly arranged on the experimental section hole wall and used for receiving low-temperature liquid nitrogen from the main pipeline and conveying the liquid nitrogen to the liquid nitrogen nozzle group;
the upstream liquid nitrogen nozzle group comprises a plurality of upstream ultralow-temperature high-pressure tail end electromagnetic valves, a plurality of upstream liquid nitrogen nozzles and a plurality of upstream support pipelines, and the number of the upstream ultralow-temperature high-pressure tail end electromagnetic valves, the number of the upstream liquid nitrogen nozzles and the number of the upstream support pipelines are the same; the upstream liquid nitrogen nozzles are uniformly distributed along the outer circumference of the experimental section hole wall, receive liquid nitrogen from the liquid collecting ring through an upstream support pipeline and spray the liquid nitrogen into the wind tunnel under the control of an upstream ultralow-temperature high-pressure tail end electromagnetic valve;
the downstream liquid nitrogen nozzle group comprises a plurality of downstream ultralow-temperature high-pressure tail end electromagnetic valves, a plurality of downstream liquid nitrogen nozzles and a plurality of downstream support pipelines, and the number of the downstream ultralow-temperature high-pressure tail end electromagnetic valves, the number of the downstream liquid nitrogen nozzles and the number of the downstream support pipelines are the same; the downstream liquid nitrogen nozzles are uniformly distributed along the outer circumference of the experimental section hole wall, receive liquid nitrogen from the liquid collecting ring through a downstream support pipeline and spray the liquid nitrogen into the wind tunnel under the control of a downstream ultralow-temperature high-pressure tail end electromagnetic valve;
the upstream liquid nitrogen nozzle group and the downstream liquid nitrogen nozzle group are distributed in parallel along the axis of the wind tunnel airflow, and the distance between the upstream liquid nitrogen nozzle group and the upstream end surface of the experimental section is 0.61dAnd the upstream end face of the downstream liquid nitrogen nozzle group spacing experimental section is 1.72dWhereindThe inner diameter of the upstream end face of the experimental section;d=1800mm；
the upstream liquid nitrogen nozzle group consists of 16 upstream ultralow-temperature high-pressure tail end electromagnetic valves, 16 upstream liquid nitrogen nozzles and 16 upstream support pipelines, and the 16 upstream liquid nitrogen nozzles are uniformly distributed along the circumferential direction of the outer side of the experimental section hole wall; the 16 upstream liquid nitrogen nozzles are controlled by 0.5Mpa differential pressure, wherein the flow rate of 3 upstream liquid nitrogen nozzles is 0.02kg/s, the flow rate of 3 upstream liquid nitrogen nozzles is 0.12kg/s, the flow rate of 6 upstream liquid nitrogen nozzles is 0.6kg/s, and the flow rate of 4 upstream liquid nitrogen nozzles is 0.73kg/s;3 upstream liquid nitrogen nozzles with a flow rate of 0.02kg/s were respectively installed at 0 of upstream jet cross section viewed in the counter-airflow direction o 、135 o 、225 o At the position, 3 upstream liquid nitrogen nozzles with a flow rate of 0.12kg/s were respectively installed at 45 of the upstream jet section viewed in the counter-air flow direction o 、180 o 、315 o At the position, 6 upstream liquid nitrogen nozzles with a flow rate of 0.6kg/s were respectively installed at 67.5 of the upstream jet section viewed in the counter-airflow direction o 、112.5 o 、157.5 o 、247.5 o 、292.5 o 、337.5 o At the position, 4 upstream liquid nitrogen nozzles with the flow rate of 0.73kg/s are respectively arranged at 22.5 of the upstream jet section observed along the reverse airflow direction o 、90 o 、202.5 o 、270 o A location;
the downstream liquid nitrogen nozzle group consists of 16 downstream ultralow-temperature high-pressure tail end electromagnetic valves, 16 downstream liquid nitrogen nozzles and 16 downstream support pipelines, and the 16 downstream liquid nitrogen nozzles are uniformly distributed along the circumferential direction of the outer side of the experimental section hole wall; the flow rate of 3 downstream liquid nitrogen nozzles is 0.02kg/s, the flow rate of 2 downstream liquid nitrogen nozzles is 0.12kg/s, the flow rate of 8 downstream liquid nitrogen nozzles is 0.6kg/s, and the flow rate of 3 downstream liquid nitrogen nozzles is 0.73kg/s;3 downstream liquid nitrogen nozzles with a flow rate of 0.02kg/s were respectively installed at 45 downstream injection cross-sections viewed in the counter-airflow direction o 、180 o 、315 o At the position, 2 downstream liquid nitrogen nozzles with the flow rate of 0.12kg/s are respectively arranged on 90 downstream injection cross sections observed along the reverse airflow direction o 、270 o At the position, 8 downstream liquid nitrogen nozzles with the flow rate of 0.6kg/s are respectively arranged at 22.5 downstream injection cross sections observed along the reverse airflow direction o 、67.5 o 、112.5 o 、157.5 o 、202.5 o 、247.5 o 、292.5 o 、337.5 o At the position, 3 downstream liquid nitrogen nozzles with flow rate of 0.73kg/s were respectively installed at 0 of downstream spray cross section viewed along the counter-gas flow direction o 、135 o 、225 o Location.
2. The liquid nitrogen injection device of the continuous high-speed wind tunnel cooling system according to claim 1, wherein: the front end of the support pipeline is connected to the liquid collecting ring through an expansion joint, the front end of the liquid nitrogen nozzle is connected to the tail end of the support pipeline through an ultralow-temperature high-pressure tail end electromagnetic valve, and the tail end of the liquid nitrogen nozzle is arranged on the wall of the experimental section; the ultralow temperature high-pressure tail end electromagnetic valve controls the opening and closing of the liquid nitrogen nozzle.
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