CN113375890A - Thermal jet flow experimental device for shock tunnel - Google Patents
Thermal jet flow experimental device for shock tunnel Download PDFInfo
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- CN113375890A CN113375890A CN202110529968.3A CN202110529968A CN113375890A CN 113375890 A CN113375890 A CN 113375890A CN 202110529968 A CN202110529968 A CN 202110529968A CN 113375890 A CN113375890 A CN 113375890A
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Abstract
The invention discloses a hot jet flow experimental device for a shock tunnel, which comprises a hydrogen pipeline, an air pipeline, a combustion chamber and a Laval nozzle, wherein the hydrogen pipeline is arranged in the combustion chamber; the combustion chamber and the Laval nozzle are sequentially connected along the ejection direction of the hot jet flow, and the hydrogen pipeline and the air pipeline are respectively communicated with the combustion chamber; along the conveying direction of hydrogen, the hydrogen pipeline comprises a hydrogen source, a hydrogen pressure reducing valve and a hydrogen flow meter which are connected in sequence; along the conveying direction of air, the air pipeline comprises an air source, an air pressure reducing valve and an air flow meter which are connected in sequence; the hydrogen flow meter and the air flow meter are each independently sonic nozzle flow meters. The thermal jet flow experimental device solves the technical problems that the thermal jet flow experimental device in the prior art is complex in structure, limited in jet flow parameter ranges such as flow rate and temperature and difficult to control.
Description
Technical Field
The invention relates to the field of shock tunnels, in particular to a hot jet flow experimental device for a shock tunnel.
Background
During the flight of the hypersonic aircraft, the coupling of the internal flow and the external flow of an engine and the jet flow generated for realizing attitude and orbit control can generate strong shock wave/shock wave interference, shock wave/boundary layer interference, separation reattachment and other large-area unsteady and unsteady flow fields, thereby generating great interference on the aerodynamic force and the aerodynamic heat of the aircraft. And the aerodynamic thermal ground test is mainly carried out in shock tunnels of millisecond magnitude. The hot jet experiment of the shock tunnel has great difficulty due to the difficulties of the generation of a transient stable hot jet air source, the time sequence synchronization within millisecond magnitude, a small-scale model and the like.
In 2011, people in old snow winter, the people of the generation of the dynasty and the like perform shock tunnel thermal jet test in a mode of connecting a LodeWichs tube into a wind tunnel window; however, the method has the defects of complex structure, limited range of jet parameters such as flow rate, temperature and the like and difficult control.
Disclosure of Invention
The invention aims to provide a hot jet flow experimental device for a shock tunnel, which aims to solve the technical problems that the hot jet flow experimental device in the prior art is complex in structure, limited in jet flow parameter ranges such as flow rate and temperature and difficult to control.
In order to solve the technical problems, the invention provides the following technical scheme:
a hot jet flow experimental device for a shock tunnel comprises a hydrogen pipeline, an air pipeline, a combustion chamber and a Laval nozzle; the combustion chamber and the Laval nozzle are sequentially connected along the ejection direction of the hot jet flow, and the hydrogen pipeline and the air pipeline are respectively communicated with the combustion chamber; along the conveying direction of hydrogen, the hydrogen pipeline comprises a hydrogen source, a hydrogen pressure reducing valve and a hydrogen flow meter which are connected in sequence; along the conveying direction of air, the air pipeline comprises an air source, an air pressure reducing valve and an air flow meter which are connected in sequence; the hydrogen flow meter and the air flow meter are each independently sonic nozzle flow meters.
In a preferred embodiment of the present invention, at least one of the hydrogen pressure reducing valve and the air pressure reducing valve is an electronic pressure reducing valve.
As a preferred technical scheme of the invention, a pressure sensor behind the hydrogen pressure reducing valve is arranged between the hydrogen pressure reducing valve and the hydrogen flowmeter;
and a pressure sensor behind the air pressure reducing valve is arranged between the air pressure reducing valve and the air flow meter.
As a preferred technical scheme of the present invention, at least one of a hydrogen filter, a hydrogen source pressure gauge, a hydrogen stop main valve, a hydrogen electromagnetic stop valve, a hydrogen check valve, a hydrogen supply pressure sensor and a hydrogen supply temperature sensor is further disposed between the hydrogen pressure reducing valve and the hydrogen flow meter;
wherein the hydrogen check valve is capable of preventing gas flow within the combustion chamber from flowing in the hydrogen conduit.
As a preferred technical solution of the present invention, at least one of an air filter, an air source pressure gauge, an air stop main valve, an air electromagnetic stop valve, an air check valve, an air supply temperature sensor and an air supply temperature sensor is further disposed between the air pressure reducing valve and the air flow meter;
wherein the air check valve is capable of preventing air flow within the combustion chamber from flowing in the air duct.
As a preferred technical scheme of the invention, the hydrogen pipeline is externally connected with a hydrogen exhaust stop valve, and the air pipeline is externally connected with an air exhaust stop valve.
As a preferred technical scheme of the invention, the hot jet flow experimental device further comprises a wind tunnel test cabin and an aircraft model; the combustion chamber and the Laval nozzle are arranged in the aircraft model, and the aircraft model is arranged in the wind tunnel test cabin; the flow direction of the wind tunnel airflow in the wind tunnel test cabin is the same as the flow direction of the hot jet airflow sprayed out from the Laval nozzle.
As a preferred technical scheme of the invention, along the flowing direction of the wind tunnel airflow, a shock tube, a wind tunnel spray pipe and the wind tunnel test cabin are sequentially connected;
as a preferable technical solution of the present invention, a spark plug is provided in the combustion chamber;
in a preferred embodiment of the present invention, a combustion chamber pressure sensor and a combustion chamber temperature sensor are provided in the combustion chamber.
As a preferred technical solution of the present invention, the thermal jet flow experimental apparatus further includes an analog output signal isolation module, the analog output signal isolation module is electrically connected to a first element, an analog output signal output by the analog output signal isolation module can control on/off of the first element, and the first element is selected from at least one of the hydrogen pressure reducing valve and the air pressure reducing valve;
as a preferred technical solution of the present invention, the thermal spray experimental apparatus further comprises an analog quantity input signal isolation module, the analog quantity input signal isolation module is electrically connected with a second element, the analog quantity input signal input by the analog quantity input signal isolation module can collect information detected by the second element, and the second element is selected from at least one of the pressure sensor, the hydrogen gas supply temperature sensor, the hydrogen gas flow meter, the pressure sensor behind the air pressure reducing valve, the air supply temperature sensor and the air supply temperature sensor, the air flow meter, the combustion chamber pressure sensor and the combustion chamber temperature sensor;
as a preferable technical solution of the present invention, the thermal jet experimental apparatus further includes a digital output signal isolation module, the digital output signal isolation module is electrically connected to a third element, the digital output signal output by the digital output signal isolation module can control on/off of the third element, and the third element is selected from at least one of the hydrogen electromagnetic stop valve, the air electromagnetic stop valve, and the spark plug.
As a preferred technical solution of the present invention, the thermal jet experimental apparatus further includes a data control acquisition card and a computer, which are electrically connected, wherein the analog output signal isolation module, the analog input signal isolation module and the digital output signal isolation module are respectively electrically connected to the data control acquisition card, and the data control acquisition card can control the output or input signals of the analog output signal isolation module, the analog input signal isolation module and the digital output signal isolation module.
The thermal jet experiment device adopts a mode of mixed combustion of an oxidant and a fuel, generates high-temperature and high-pressure jet flow in a model, is used for researching force load and thermal load of the model under the action of coupling of inner and outer flows, and relates to a high-temperature gas dynamics experiment.
The hot jet flow experimental device generates supersonic speed hot gas jet flow through a hot jet flow experimental table, and the total indexes of the system are as follows: the flow rate is 0.18kg/s, the total temperature is 680K, the total pressure is 0.26MPa, the outlet flow rate is 1.84Ma, and the single experiment time is 5 s.
At present, the chemical equation (1) for releasing heat by combusting the oxidant with air and the fuel with hydrogen, hydrogen and air is as follows:
in the above formula, m and n are each hydrogen (H)2) And air (0.21O)2+0.79N2) The composition of air is 21% of oxygen and 79% of nitrogen, g represents a gaseous state, and H represents the heat of combustion reaction. By using the combustion reaction of hydrogen and air with different molar numbers, different heat can be released, and the heat is used for heating combustion products, so that high-temperature fuel gas is generated.
Generally, to express the fuel and oxidant mixture ratio, the oxygen-to-oil ratio O/F can be used. The oxygen to oil ratio, O/F, is the mass ratio of the oxidant (i.e., air) to the fuel (i.e., hydrogen). According to the chemical reaction equation, the oxygen-oil ratio can be calculated and obtained as shown in the formula (2):
the hydrogen air combustion conditions under different oxygen-oil ratios O/F calculated by using chemical equilibrium flow software CEA are shown in table 1 below: in table 1,% f is the oil content, i.e., mass percent of hydrogen; phi is a combustion equivalence ratio, t is the total temperature of the fuel gas, and the unit is K; rho is the density of the fuel gas in kg/m3(ii) a mw is the average molecular weight; cp is the specific heat at constant pressure of the fuel gas; gama is the specific heat ratio of the fuel gas; son is the sound velocity of gas in m/s.
TABLE 1
According to the data in the table, the fuel gas with any temperature can be designed by proportioning the mass flow of the hydrogen and the air. In order to ensure the safety of the experiment and prevent redundant hydrogen explosion, the hot jet flow device adopts the design of rich air and poor hydrogen, namely, a small amount of hydrogen and a large amount of air are adopted; therefore, the combustion equivalence ratio is less than 1, only residual water, oxygen and nitrogen are left in the product, hydrogen is completely combusted, and no hydrogen exists in fuel gas, so that safety is ensured. According to the data in the table, the equivalence ratio can be taken to be in the range of 0.05-0.9, the oxygen-oil ratio O/F is 685.9-38.1, and the total temperature is 470K-2335K.
In order to obtain the hot jet gas with set temperature, the mass flow of hydrogen and air needs to be accurately controlled, and the invention adopts a sonic nozzle flow meter to control and measure the gas flow. The principle of the sonic nozzle flowmeter is as follows: when the pressure at the downstream of the nozzle is lower than 1/2 of the upstream pressure, the airflow at the throat of the nozzle is at sonic speed, the Mach number is 1, and the mass flow of the airflow flowing through the flowmeter is only related to the total pressure, the total temperature, the throat area and the gas medium at the upstream of the flowmeter and is not related to the pressure at the downstream of the flowmeter. The flowmeter can prevent the pressure change of the downstream combustion chamber before and after ignition from influencing the upstream gas flow field. The flowmeter is applied to gas, assuming that the molecular weight of a medium in a pipeline is M, the mass flow rate is Q (unit kg/s), and the temperature is T1, according to quasi-one-dimensional gas dynamics knowledge, after the gas is subjected to isentropic compression and expansion of a spray pipe, if the relation of total pressure P1 in front of a sonic nozzle and back pressure P2 behind the sonic nozzle satisfies the formula (3):
P2＜0.5P1 (1)
the gas velocity at the throat is sonic. At this time, according to the quasi-one-dimensional gas dynamics knowledge, the mass flow calculation formula of the gas is easily obtained as formula (4):
in the above formula, α is a flow coefficient of the flowmeter and is a constant to be calibrated, γ is a specific heat ratio, an ideal gas value is 1.4, and the specific heat ratio of most gases at normal temperature and normal pressure is 1.4. R is a gas constant, and the calculation formula is shown as formula (5):
a is the throat area of the flowmeter and d is the throat diameter of the flowmeter, i.e.
From the above calculation, it can be known that the flow rate of the gas can be accurately controlled only by determining the molecular weight M of the gas, the diameter d of the throat of the flowmeter, the total temperature T of the gas and the total pressure P of the gas. In fact, the molecular weight M is a definite constant after the kind of gas is determined, the throat diameter is also a definite actual processing value, and the total temperature T of the gas is usually normal temperature, so that the required gas flow rate can be determined by only determining the total pressure P of the gas. And the total pressure P of the gas can be accurately adjusted by the pressure reducing valve, so that the accurate gas flow is obtained. After the flow of each path of gas is accurately obtained, the total temperature of the fuel gas can be accurately obtained by burning the hydrogen and the air, so that the effects of accurately controlling the flow and the temperature of the hot jet gas are achieved.
The above results are obtained by creative labor of the inventor, and on the basis of the results, the thermal jet flow experimental device for the shock tunnel is designed, and the working principle of the thermal jet flow experimental device is as follows: the hydrogen source is conveyed in the hydrogen pipeline, and the hydrogen pressure reducing valve can accurately control the pressure of hydrogen entering the hydrogen flow meter, so that the gas flow of the hydrogen passing through the hydrogen flow meter is accurately controlled; similarly, an air source is conveyed in an air pipeline, and the air pressure reducing valve can accurately adjust the pressure of air entering the air flow meter for timing, so that the air flow of the air passing through the air flow meter is accurately controlled; therefore, the flow rates of the air and the hydrogen in the combustion chamber can be accurately controlled, and the total temperature of the fuel gas in the combustion chamber can be accurately controlled, so that the effects of accurately controlling the flow rate and the temperature of the hot jet gas are achieved.
Therefore, the hot jet flow experimental device adopts the combination combustion of hydrogen and air to realize the ejection of high-temperature gas from the wind tunnel model at supersonic speed. Compared with the prior art, the invention has the following advantages: simple structure, safe and reliable, stability is good, and jet parameters such as flow and temperature wide range and can accurate control.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
Fig. 1 is a schematic structural diagram of a preferred embodiment of a thermal jet experimental apparatus for a shock tunnel according to the present invention.
The reference numerals in the drawings denote the following, respectively:
1. hydrogen source 2, hydrogen filter
3. Hydrogen source pressure gauge 4 and hydrogen stop main valve
5. Hydrogen exhaust stop valve 6 and hydrogen pressure reducing valve
7. Pressure sensor 8 behind hydrogen relief valve, hydrogen electromagnetism stop valve
9. Hydrogen check valve 10 and hydrogen supply pressure sensor
11. Hydrogen supply temperature sensor 12 and hydrogen flowmeter
13. Hydrogen gas pipe 14, air source
15. Air filter 16 and air source pressure gauge
17. Air exhaust stop valve 18 and air stop main valve
19. Air pressure reducing valve 20, and pressure sensor behind air pressure reducing valve
21. Air electromagnetic stop valve 22 and air one-way valve
23. Air supply temperature sensor 24, air supply temperature sensor
25. Air flow meter 26, air duct
27. Spark plug 28 and combustion chamber pressure sensor
29. Combustion chamber temperature sensor 30, combustion chamber
31. Laval nozzle 32 and aircraft model
33. Thermal jet stream 34, shock tube
35. Wind tunnel nozzle 36 and wind tunnel test cabin
37. Wind tunnel airflow 38, analog output signal
39. Analog input signal 40, digital output signal
41. Analog output signal isolation module 42 and analog input signal isolation module
43. Digital quantity output signal isolation module 44 and data control acquisition card
45. And (4) a computer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a hot jet flow experimental device for a shock tunnel, which comprises a hydrogen pipeline 13, an air pipeline 26, a combustion chamber 30 and a Laval nozzle 31, wherein the hot jet flow experimental device is shown in figure 1; the combustion chamber 30 and the laval nozzle 31 are sequentially connected along the ejection direction of the hot jet flow 33, and the hydrogen pipeline 13 and the air pipeline 26 are respectively communicated with the combustion chamber 30; along the hydrogen conveying direction, the hydrogen pipeline 13 comprises a hydrogen source 1, a hydrogen pressure reducing valve 6 and a hydrogen flow meter 12 which are connected in sequence; along the air conveying direction, the air pipeline 26 comprises an air source 14, an air reducing valve 19 and an air flow meter 25 which are connected in sequence; the hydrogen flow meter 12 and the air flow meter 25 are each independently a sonic nozzle flow meter.
The combustor 30 is used for mixing, igniting and combusting hydrogen and air to generate high-temperature and high-pressure fuel gas. The laval nozzle 31 is used to accelerate the high temperature and high pressure fuel gas to supersonic velocity. The hot jet flow 33 is a hot flow accelerated to supersonic speed through the Laval nozzle 31, and the hot flow is discharged from the tail of the model and enters the shock tunnel test chamber. The hydrogen flowmeter 12 adopts a sonic nozzle flowmeter which can measure the hydrogen flow and stably control the flow, so as to prevent the pressure change of a downstream combustion chamber from influencing the hydrogen flow. The air flow meter 25 also employs a sonic nozzle flow meter which can measure the air flow rate and stably control the flow rate to prevent the downstream combustion chamber pressure variation from affecting the air flow rate.
In the present invention, the structure of the hydrogen source 1 is not particularly limited, but in order to ensure stable supply of hydrogen, it is preferable that the hydrogen source 1 is a hydrogen cylinder group, and 1 to 2 40L hydrogen cylinders are generally used.
In the present invention, the specific structure of the hydrogen pipeline 13 is not particularly limited, but in order to ensure that hydrogen can be stably transported in the hydrogen pipeline 13, preferably, the hydrogen pipeline 13 includes a pipeline from the hydrogen source 1, which connects each valve and each sensor, the pipeline is a high-pressure pipeline, a stainless steel pressure-resistant pipe is adopted, the thickness of the pipeline is designed according to the requirements of the pressure pipeline, a phi 12 × 1.5-sized pipeline is adopted, the outer diameter is 12mm, and the wall thickness is 1.5 mm.
In the present invention, the specific structure of the hydrogen pressure reducing valve 6 is not particularly required, and may be a manual mechanical pressure reducing valve, or may be another valve with higher precision, and in order to further improve the precision, it is preferable that the hydrogen pressure reducing valve 6 is an electronic pressure reducing valve for reducing the high pressure of the hydrogen source 1 to a set pressure. The valve is connected with a collecting card of a computer, and can issue instructions through the computer to control the valve to regulate and output required pressure.
In the above embodiment, the air source 14 may be provided in various manners, but for convenience of transportation and replacement, it is preferable that the air source 14 is an air cylinder, typically a 4-cylinder 40L air cylinder.
In the above embodiment, the structure of the air pipe 26 may be various, but it is ensured that the air can be stably transported in the air pipe 26, and preferably, the air pipe 26 includes a pipe from the air source 14 to connect each valve and each sensor, and the pipe is a high-pressure pipe and is a stainless steel pressure-resistant pipe. The thickness of the pipeline is designed according to the requirements of the pressure pipeline, a phi 20 multiplied by 2 specification pipeline is adopted, the outer diameter is 20mm, and the wall thickness is 2 mm.
In the above embodiment, the specific structure of the air pressure reducing valve 19 is not particularly required, and may be a manual mechanical pressure reducing valve, or may be another valve with higher precision. The valve can be connected with a collecting card of a computer, and can issue instructions through the computer to control the valve to regulate and output required pressure.
In addition to the above, in order to measure the hydrogen pressure after the hydrogen pressure reducing valve 6, a hydrogen pressure after pressure reducing valve sensor 7 is preferably provided between the hydrogen pressure reducing valve 6 and the hydrogen flowmeter 12.
Similarly, in order to measure the air pressure after the air pressure reducing valve 19, a pressure sensor 20 after the air pressure reducing valve 19 and the air flow meter 25 are preferably disposed therebetween.
In addition to the above embodiments, in order to further ensure that hydrogen can be stably delivered in the hydrogen pipeline 13, at least one of the hydrogen source 1, the hydrogen filter 2, the hydrogen source pressure gauge 3, the hydrogen stop main valve 4, the hydrogen electromagnetic stop valve 8, the hydrogen check valve 9, the hydrogen supply pressure sensor 10, and the hydrogen supply temperature sensor 11 is preferably further provided between the hydrogen source 1 and the hydrogen flow meter 12.
The hydrogen check valve 9 can prevent the airflow in the combustion chamber 30 from returning to the hydrogen pipeline 13, and avoid the combustion explosion of the hydrogen in the hydrogen pipeline 13; the hydrogen filter 2 is used for protecting parts such as a stop valve, a pressure reducing valve and the like on a pipeline and preventing impurities in the gas from entering the valve and damaging the valve; the hydrogen source pressure gauge 3 is used for measuring the hydrogen pressure in the hydrogen source 1 in real time; the hydrogen stop main valve 4 is a main valve for hydrogen, is used for opening or cutting off hydrogen supply, and can be a manual valve or an electronic valve; the hydrogen electromagnetic stop valve 8 can be connected with a computer acquisition card and is used for accurately controlling the on-off of the valve by the computer, ensuring the ignition time sequence and preventing explosion, and the danger of manual operation in the experimental process can be avoided by adopting an electric signal to remotely control the valve; the hydrogen supply pressure sensor 10 is used to measure the total hydrogen pressure before the hydrogen flowmeter, and the hydrogen supply temperature sensor 11 is used to measure the total hydrogen temperature before the hydrogen flowmeter. Wherein, in order to better monitor the temperature and pressure before the hydrogen flowmeter, the hydrogen supply pressure sensor 10 and the hydrogen supply temperature sensor 11 are arranged between the hydrogen pressure reducing valve 6 and the hydrogen flowmeter 12.
On this basis, in order to better exert the functions of the respective components, it is preferable that, as shown in fig. 1, the hydrogen source 1, the hydrogen filter 2, the hydrogen source pressure gauge 3, the hydrogen shut-off main valve 4, the hydrogen pressure reducing valve 6, the hydrogen pressure reducing valve rear pressure sensor 7, the hydrogen electromagnetic shut-off valve 8, the hydrogen check valve 9, the hydrogen supply pressure sensor 10, the hydrogen supply temperature sensor 11, and the hydrogen flow meter 12 are arranged along the hydrogen gas conveying direction; the hydrogen supply pressure sensor 10 and the hydrogen supply temperature sensor 11 may be arranged in a stacked manner.
In the same way, in order to further ensure that the air can be stably conveyed in the air pipe 26, at least one of the air filter 15, the air source pressure gauge 16, the air stop main valve 18, the air electromagnetic stop valve 21, the air check valve 22, the air supply temperature sensor 23 and the air supply temperature sensor 24 is preferably further arranged between the air source 14 and the air flow meter 25.
Wherein the air check valve 22 is capable of preventing the flow of air within the combustion chamber 30 from returning into the air duct; the air filter 15 is used for protecting parts such as a stop valve and a pressure reducing valve on a pipeline and preventing impurities in gas from entering the valve and damaging the valve; an air source pressure gauge 16 for measuring the air pressure in the air source 14; the air stop main valve 18 is a main valve of air, is used for opening or cutting off air supply, and can be a manual valve or an electronic valve; the air electromagnetic stop valve 21 can be connected with a computer acquisition card and is used for accurately controlling the on-off of the valve by the computer, ensuring the ignition time sequence and preventing explosion, and the danger of manual operation in the experimental process can be avoided by adopting an electric signal to remotely control the valve; the air supply temperature sensor 23 is used for measuring the total hydrogen pressure before the air flow meter; the air supply temperature sensor 24 is used for measuring the total temperature of hydrogen gas before the air flow meter; wherein, in order to better monitor the temperature and pressure before the air flow meter, the air supply temperature sensor 23 and the air supply temperature sensor 24 are arranged between the air pressure reducing valve 19 and the air flow meter 25.
On this basis, in order to better exert the functions of the respective components, it is preferable that, as shown in fig. 1, the air source 14, the air filter 15, the air source pressure gauge 16, the air shutoff main valve 18, the air reducing valve 19, the air reducing valve rear pressure sensor 20, the air electromagnetic shutoff valve 21, the air check valve 22, the air supply temperature sensor 23, the air supply temperature sensor 24, and the air flow meter 25 are arranged along the air conveying direction; the air supply temperature sensor 23 and the air supply temperature sensor 24 may be arranged in a stacked manner.
In the present invention, in order to facilitate the discharge of hydrogen in the hydrogen pipe 13, it is preferable that the hydrogen pipe 13 is externally connected with a hydrogen exhaust stop valve 5, and after all other valves in the pipe are closed, the hydrogen exhaust stop valve 5 is opened to discharge the residual gas in the pipe.
In the present invention, in order to facilitate the air in the air duct 26 to be discharged, it is preferable that the air duct 26 is externally connected with an air exhaust stop valve 17, and after all other valves in the duct are closed, the air exhaust stop valve 17 is opened to discharge the residual air in the duct.
In the present invention, the installation positions of the combustion chamber 30 and the laval nozzle 31 can be selected within a wide range, but in order to further ensure the smooth performance of the thermal jet test of the shock tunnel, it is preferable that the thermal jet test apparatus further includes a tunnel test chamber 36 and an aircraft model 32; the combustion chamber 30 and the Laval nozzle 31 are arranged in the aircraft model 32, and the aircraft model 32 is arranged in the wind tunnel test cabin 36; the direction of the wind tunnel air flow 37 in the wind tunnel test chamber 36 is the same as the direction of the hot jet air flow 33 ejected from the laval nozzle 31. Therefore, the wind tunnel test cabin 36 is used for placing the aircraft model 32 and researching the stress and heating condition of the model in the shock tunnel flow field; the wind tunnel airflow 37 is generated by high-temperature and high-pressure gas in the shock tube after being accelerated by the spray pipe and acts on the aircraft model 32; the aircraft model 32 can be in a triangular layout in an airplane style, and can also be in a cylindrical layout similar to a missile, and the combustion chamber 30 for hot jet and the Laval nozzle 31 are installed in the interior of the aircraft.
In the present invention, the wind tunnel air flow 37 is provided in various manners, but in order to stably provide the wind tunnel air flow 37, it is preferable that the shock tube 34, the wind tunnel nozzle 35, and the wind tunnel test chamber 36 are connected in this order along the direction of the wind tunnel air flow 37; the shock tube 34 is used for generating high-temperature and high-pressure air flow and shock wave; the wind tunnel nozzle 35 is used for accelerating the airflow in the shock tube 34 to supersonic speed, and the airflow is sprayed into the wind tunnel test cabin 36 to blow the aircraft model 32.
In addition, in the present invention, the ignition mode of the fuel and the oxidant in the combustion chamber 30 may be various, and in order to safely achieve the ignition, it is preferable that a spark plug 27 is provided in the combustion chamber 30; the spark plug 27 can generate high frequency electric spark for ignition after mixing hydrogen and air, and more importantly, the spark plug 27 can be switched on and off by a computer in a remote control mode.
Meanwhile, in order to detect various parameters in the combustion chamber 30 in real time, it is preferable that a combustion chamber pressure sensor 28 and a combustion chamber temperature sensor 29 are provided in the combustion chamber 30. Thus, the combustion chamber pressure sensor 28 can measure the gas pressure in the combustion chamber in real time; the combustion chamber temperature sensor 29 can measure the temperature of the gas in the combustion chamber in real time.
As can be known from the above description, the hydrogen pressure reducing valve 6 and the air pressure reducing valve 19 may be mechanical valves or electronic valves, and in order to facilitate accurate control of the valves, preferably, the thermal jet flow experimental apparatus further includes an analog output signal isolation module 41, where the analog output signal isolation module 41 is electrically connected to a first element, an analog output signal 38 output by the analog output signal isolation module 41 can control on/off of the first element, and the first element is selected from at least one of the hydrogen pressure reducing valve 6 and the air pressure reducing valve 19; therefore, as long as the analog output signal isolation module 41 sends the analog output signal 38 to precisely control the operation of the pressure reducing valve, the gas pressure behind the valve is reduced to the set pressure value.
In the above embodiments, the pressure sensor 7, the hydrogen supply pressure sensor 10, the hydrogen supply temperature sensor 11, the hydrogen flow meter 12, the pressure sensor 20 after the air pressure reducing valve, the air supply temperature sensor 23, the air supply temperature sensor 24, the air flow meter 25, the combustion chamber pressure sensor 28, and the combustion chamber temperature sensor 29 are used for collecting pressure, temperature, and flow rate signals, and various signals can be collected in various ways, but in order to improve the efficiency and accuracy of collection, preferably, the thermal spray flow experimental apparatus further comprises an analog quantity input signal isolation module 42, the analog quantity input signal isolation module 42 is electrically connected with a second element, the analog quantity input signal 39 input by the analog quantity input signal isolation module 42 can collect information detected by the second element, and the second element is selected from the pressure sensor 7, the air pressure reducing valve, and the air supply temperature sensor 23, the air supply temperature sensor 24, the air flow meter 25, the combustion chamber pressure sensor 28, and the combustion chamber temperature sensor 29, At least one of a hydrogen gas supply pressure sensor 10, a hydrogen gas supply temperature sensor 11, the hydrogen gas flow meter 12, a post-air pressure-reducing-valve pressure sensor 20, an air supply temperature sensor 23, and an air supply temperature sensor 24, an air flow meter 25, a combustion chamber pressure sensor 28, and a combustion chamber temperature sensor 29; therefore, the pressure, temperature and flow signals collected by the pressure sensor 7, the hydrogen supply pressure sensor 10, the hydrogen supply temperature sensor 11, the hydrogen flowmeter 12, the pressure sensor 20 after the air pressure reducing valve, the air supply temperature sensor 23 and the air supply temperature sensor 24, the air flowmeter 25, the combustion chamber pressure sensor 28 and the combustion chamber temperature sensor 29 can be input into the analog input signal isolation module 42 for aggregation in the form of the analog input signal 39.
Similarly, the hydrogen electromagnetic cut-off valve 8, the air electromagnetic cut-off valve 21 and the spark plug 27 can be opened and closed manually, and can be controlled electronically and remotely, and in order to control the opening and closing more conveniently, the thermal jet experimental device preferably further comprises a digital output signal isolation module 43, the digital output signal isolation module 43 is electrically connected with a third element, the digital output signal 40 output by the digital output signal isolation module 43 can control the opening and closing of the third element, and the third element is selected from at least one of the hydrogen electromagnetic cut-off valve 8, the air electromagnetic cut-off valve 21 and the spark plug 27. Therefore, the digital output signal isolation module 43 is preset, so that the on-off of each component can be controlled by the digital output signal 40 finally.
In the above embodiment, the analog quantity output signal isolation module 41, the analog quantity input signal isolation module 42 and the digital quantity output signal isolation module 43 function as signal input or output, to facilitate the control of the signals of the analog quantity output signal isolation block 41, the analog quantity input signal isolation block 42 and the digital quantity output signal isolation block 43, preferably, the thermal jet experimental apparatus further comprises a data control acquisition card 44 and a computer 45 which are electrically connected, the analog quantity output signal isolation module 41, the analog quantity input signal isolation module 42 and the digital quantity output signal isolation module 43 are respectively electrically connected with the data control acquisition card 44, the data control acquisition card 44 can control the analog quantity output signal isolation module 41, the analog quantity input signal isolation module 42 and the digital quantity output signal isolation module 43 to output or input signals; for example, the analog output signal 38 is obtained by calculating the analog signal of 0-10V output by the data control acquisition card 44.
The design method of the thermal jet flow device is described by taking the typical working condition of the thermal jet flow in the shock tunnel test as an example.
The overall index of the thermal jet system is: through a hot jet experiment table, supersonic hot gas jet flow is generated, the flow rate is 0.18kg/s, the total temperature is 680K, the outlet is 1.84Ma, and the single experiment time is 5 s.
Calculated according to the chemical reaction, when the total flow rate is 0.18kg/s and the total temperature is 680K, the O/F is 290.
Then the hydrogen flow rate is
An air flow rate of
Molecular weight for hydrogen
Then the gas constant of hydrogen is
The throat diameter of the sonic nozzle flowmeter of the hydrogen is
The throat area of the flow meter is then
The flow coefficient of the sonic nozzle flowmeter is constant and can be obtained by calibration, and the flow coefficient of the hydrogen flowmeter is
Hydrogen is at normal temperature and total temperature is
Hydrogen can be regarded as ideal gas, and the specific heat ratio is
γ＝1.4 (13)
The total pressure of hydrogen required can thus be calculated as
Same calculation procedure, molecular weight for air
Mair＝29 (15)
Then the gas constant of air is
The throat diameter of the air sonic nozzle flowmeter is
The throat area of the flow meter is then
The flow coefficient of the sonic nozzle flowmeter is constant and can be obtained by calibration, and the flow coefficient of the air flowmeter is
αair＝0.98 (19)
Air is at normal temperature and total temperature is
T1air＝300 K (20)
Air can be regarded as ideal gas, and the specific heat ratio is
γ＝1.4 (21)
The total pressure of the air required can thus be calculated as
In summary, the desired flow rate and temperature of the hot jet stream can be obtained by obtaining a total pressure of hydrogen and air.
The total gas pressure of the hot jet flow can be obtained according to the sonic flow meter, because the jet pipe of the hot jet flow is a Laval jet pipe, the formula of the sonic flow meter is also met, and according to the chemical calculation, the total temperature of the hot jet flow is
T1＝680 K (23)
Total flow of
Q＝180g/s (24)
The molecular weight of the fuel gas can be obtained from the foregoing Table 1 of the chemical calculation as
M＝28.4 (25)
The gas constant of the combustion gas is then
The specific heat ratio of the fuel gas is obtained by looking up a table according to chemical calculation
γ＝1.36 (27)
After the hot jet combustor is finished, the throat diameter is determined and measured as
d＝24mm (28)
The throat area of the combustion chamber is
The nozzle of the hot jet combustion chamber is processed with high precision and efficiency
α＝0.99 (30)
The total pressure of the hot jets can be calculated
The gas is accelerated through the Laval nozzle, and the Mach number of the outlet can be obtained according to the quasi-one-dimensional flowing property of the Laval nozzle, namely
In the above formula, Ae is the area of the nozzle outlet and is a determined value after processing; a is the throat area of the nozzle, M is the Mach number of the nozzle outlet, and is the specific heat ratio of the fuel gas. The above formula is a transcendental equation, can not be obtained by an analytical method, can be solved by a numerical calculation method,
the diameter of the nozzle outlet is
de＝29.4mm (33)
According to the formula of the area of the circle, the area of the outlet of the spray pipe is
Thereby obtaining the Mach number of the outlet of the spray pipe as
M＝1.84 (35)
In conclusion, the total pressure and the flow rate of two paths of hydrogen and air for generating the hot jet flow, the total pressure, the total temperature, the flow rate and the jet Mach number of the hot jet flow are obtained through calculation; that is, according to the calculation results of the chemical reactions, when the O/F is 290, the time of a single experiment is 5s, the hydrogen flow rate is 0.618g/s, the air flow rate is 179.382g/s, the system flow rate is 0.18kg/s, and the total temperature is 680K, the outlet flow rate is 1.84 Ma.
The present invention is further illustrated by the following examples.
Example 1
1) Installing and fixing an aircraft model 32 with a combustion chamber 30 in a shock tunnel test cabin 36;
2) vacuumizing the shock tunnel test chamber 32, wherein the vacuum degree is 20 Pa;
3) an air inlet connecting the hydrogen line 13 and the air line 26 to the combustion chamber 30;
4) manually opening the hydrogen gas cylinder 1 and the air gas cylinder 14 to ensure that the pressure of the two gas cylinders is more than 10 MPa;
5) the hydrogen stop main valve 4 and the air stop main valve 18 are manually opened;
6) the input hydrogen pressure reducing valve 6 in the computer 45 is 1.3MPa, and the pressure of the air pressure reducing valve 19 is 2.0 MPa;
7) computer control, open the electromagnetic stop valve 8 of hydrogen and electromagnetic stop valve 21 of air at the same time, supply hydrogen and air to the combustion chamber;
8) computer control, turning on the power of the spark plug 27, and starting ignition of the spark plug;
9) the hydrogen and the air are ignited and combusted in the combustion chamber 30, and are sprayed out from the tail part of the model through the Laval nozzle 31 to form supersonic hot jet flow 33 which is sprayed into the wind tunnel test chamber 36;
10) starting a shock tunnel, generating high-pressure airflow and shock waves in a shock tube 34, accelerating the high-pressure airflow and the shock waves to supersonic speed through a wind tunnel nozzle 35, and entering a wind tunnel test cabin 36 to form wind tunnel airflow 37;
11) wind tunnel stream 37 blows against the surface of model aircraft 32, exerts a force and thermal load on the model aircraft, and interacts with hot jet stream 33;
12) in the test process, the computer acquires and records signals acquired by a hydrogen pressure reducing valve rear pressure sensor 7, a hydrogen supply pressure sensor 10, a hydrogen supply temperature sensor 11, an air pressure reducing valve rear pressure sensor 20, an air supply temperature sensor 23, an air supply temperature sensor 24, a combustion chamber pressure sensor 28, a combustion chamber temperature sensor 29 and the like in real time;
in the test process, the computer collects and records the pressure 7 behind the hydrogen pressure reducing valve to be 1.2MPa, the hydrogen supply temperature to be 300K, the pressure behind the air pressure reducing valve to be 1.9MPa, the air supply temperature to be 300K, the gas pressure to be 0.26MPa and the gas temperature to be 400 ℃ in real time, and the incomplete consistency of the experimental measured data and the theoretical calculated value can be caused by measurement errors and insufficient valve adjustment precision, so that necessary improvement can be carried out in subsequent experiments.
13) The shock tunnel experiment table is also provided with some experimental test means such as aerodynamic force measurement, heat flow measurement, optical measurement and the like, which are used for measuring the force and the heat load of the model in the experimental process and are not developed as the technical scheme of the invention.
14) After the experiment, various valves in the hydrogen gas circuit and various valves in the air gas circuit are closed, the gas supply is cut off, and the combustion chamber is flamed out.
The above embodiments are only exemplary embodiments of the present application, and are not intended to limit the present application, and the protection scope of the present application is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present application and such modifications and equivalents should also be considered to fall within the scope of the present application.
Claims (10)
1. A hot jet flow experimental apparatus for a shock tunnel is characterized in that: the hot jet flow experimental device comprises a hydrogen pipeline (13), an air pipeline (26), a combustion chamber (30) and a Laval nozzle (31); the combustion chamber (30) and the Laval nozzle (31) are sequentially connected along the ejection direction of the hot jet flow (33), and the hydrogen pipeline (13) and the air pipeline (26) are respectively communicated with the combustion chamber (30); along the conveying direction of hydrogen, the hydrogen pipeline (13) comprises a hydrogen source (1), a hydrogen pressure reducing valve (6) and a hydrogen flow meter (12) which are connected in sequence; along the air conveying direction, the air pipeline (26) comprises an air source (14), an air pressure reducing valve (19) and an air flow meter (25) which are connected in sequence; the hydrogen flow meter (12) and the air flow meter (25) are each independently a sonic nozzle flow meter.
2. The thermal jet experimental device for the shock tunnel according to claim 1, wherein: at least one of the hydrogen pressure reducing valve (6) and the air pressure reducing valve (19) is an electronic pressure reducing valve.
3. The thermal jet experimental device for the shock tunnel according to claim 1 or 2, wherein: a pressure sensor (7) behind the hydrogen pressure reducing valve is arranged between the hydrogen pressure reducing valve (6) and the hydrogen flowmeter (12);
and a pressure sensor (20) behind the air pressure reducing valve is arranged between the air pressure reducing valve (19) and the air flow meter (25).
4. The thermal jet experimental device for the shock tunnel according to claim 3, wherein: at least one of a hydrogen filter (2), a hydrogen source pressure gauge (3), a hydrogen stop main valve (4), a hydrogen electromagnetic stop valve (8), a hydrogen one-way valve (9), a hydrogen supply pressure sensor (10) and a hydrogen supply temperature sensor (11) is also arranged between the hydrogen source (1) and the hydrogen flow meter (12);
wherein the hydrogen check valve (9) is capable of preventing the flow of gas within the combustion chamber (30) in the hydrogen conduit (13).
5. The thermal jet experimental device for the shock tunnel according to claim 3, wherein: at least one of an air filter (15), an air source pressure gauge (16), an air stop main valve (18), an air electromagnetic stop valve (21), an air one-way valve (22), an air supply temperature sensor (23) and an air supply temperature sensor (24) is arranged between the air source (14) and the air flow meter (25);
wherein the air check valve (22) is capable of preventing the flow of air within the combustion chamber (30) in the air duct (26).
6. The thermal jet experimental device for the shock tunnel according to claim 1 or 2, wherein: the hydrogen pipeline (13) is externally connected with a hydrogen exhaust stop valve (5), and the air pipeline (26) is externally connected with an air exhaust stop valve (17).
7. The thermal jet experimental device for the shock tunnel according to claim 1, wherein: the hot jet flow experimental device also comprises a wind tunnel test cabin (36) and an aircraft model (32); the combustion chamber (30) and the Laval nozzle (31) are arranged in the aircraft model (32), and the aircraft model (32) is arranged in the wind tunnel test cabin (36); the direction of the wind tunnel airflow (37) in the wind tunnel test chamber (36) is the same as the direction of the hot jet flow (33) sprayed out of the Laval nozzle (31).
8. The thermal jet experimental device for the shock tunnel according to claim 7, wherein: along the direction of the wind tunnel airflow (37), a shock tube (34), a wind tunnel nozzle (35) and the wind tunnel test cabin (36) are connected in sequence;
preferably, a spark plug (27) is arranged in the combustion chamber (30);
preferably, a combustion chamber pressure sensor (28) and a combustion chamber temperature sensor (29) are arranged in the combustion chamber (30).
9. The thermal jet experimental device for the shock tunnel according to any one of claims 1 to 7, wherein: the thermal jet flow experimental device further comprises an analog quantity output signal isolation module (41), wherein the analog quantity output signal isolation module (41) is electrically connected with a first element, an analog quantity output signal (38) output by the analog quantity output signal isolation module (41) can control the on-off of the first element, and the first element is selected from at least one of the hydrogen pressure reducing valve (6) and the air pressure reducing valve (19);
preferably, the thermal spray flow experimental device further comprises an analog quantity input signal isolation module (42), the analog quantity input signal isolation module (42) is electrically connected with a second element, the analog quantity input signal (39) input by the analog quantity input signal isolation module (42) can collect information detected by the second element, and the second element is selected from at least one of the pressure sensor (7), the hydrogen supply pressure sensor (10), the hydrogen supply temperature sensor (11), the hydrogen flow meter (12), the pressure sensor (20) after the air pressure reducing valve, the air supply temperature sensor (23) and the air supply temperature sensor (24), the air flow meter (25), the combustion chamber pressure sensor (28) and the combustion chamber temperature sensor (29);
preferably, the thermal jet flow experimental device further comprises a digital output signal isolation module (43), the digital output signal isolation module (43) is electrically connected with a third element, the digital output signal (40) output by the digital output signal isolation module (43) can control the on-off of the third element, and the third element is selected from at least one of the hydrogen electromagnetic stop valve (8), the air electromagnetic stop valve (21) and the spark plug (27).
10. The thermal jet experimental device for the shock tunnel according to claim 9, wherein: the thermal jet flow experimental device further comprises a data control acquisition card (44) and a computer (45), wherein the data control acquisition card (44) and the computer are electrically connected, the analog output signal isolation module (41), the analog input signal isolation module (42) and the digital output signal isolation module (43) are respectively and electrically connected with the data control acquisition card (44), and the data control acquisition card (44) can control the output or input signals of the analog output signal isolation module (41), the analog input signal isolation module (42) and the digital output signal isolation module (43).
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