CN112407346A

CN112407346A - Thermal test method and device for metal fiber surface combustion structure

Info

Publication number: CN112407346A
Application number: CN202011265031.1A
Authority: CN
Inventors: 齐玢; 阿嵘; 董素君; 王日; 侯砚泽
Original assignee: China Academy of Space Technology CAST
Current assignee: China Academy of Space Technology CAST
Priority date: 2020-11-12
Filing date: 2020-11-12
Publication date: 2021-02-26
Anticipated expiration: 2040-11-12
Also published as: CN112407346B

Abstract

The invention relates to a thermal test method and a device for a metal fiber surface combustion structure, wherein the method comprises the following steps: a. mixing fuel gas and a gas combustion improver to form mixed gas, and conveying the mixed gas along at least one gas path; b. igniting the mixed gas at the tail end of the gas path, and enabling the combustion flame to pass through the attachment, wherein each point of at least one surface of the attachment corresponds to each point of the heated surface of the test piece, so that the fuel gas formed by combustion is sprayed to the heated surface of the test piece to heat the heated surface; c. and measuring the heat load parameters of the heated surface of the test piece corresponding to each gas path in real time, and controlling the flow of the mixed gas in the corresponding gas path in real time according to the heat load parameters. In the invention, the attachment formed by weaving the metal fibers is used as the attachment of the mixed gas combustion flame, so that the combustion surface can adapt to the complex appearance of the test piece, and full-scale simulation is realized.

Description

Thermal test method and device for metal fiber surface combustion structure

Technical Field

The invention relates to the technical field of thermal tests, in particular to a structural thermal test method and a structural thermal test device based on metal fiber surface combustion.

Background

With the development of aerospace technology, hypersonic aircrafts are becoming important development directions in all aerospace big countries. Such aircraft are subjected to thermal loads from hypersonic airflows during flight, and thermal protection structures must be employed to ensure safety of the aircraft and to maintain the interior of the aircraft within allowable temperature and pressure ranges. The front edge of the aircraft, the wing rudder structure, the air inlet channel, the spray pipe and other key parts adopt complex profile design, the distribution gradient of the surface heat load is large in the hypersonic flight process, the size is often large, and meanwhile, the heat load has the characteristics of high impact rate and strong nonlinearity because the maneuvering or hypersonic orbit transfer is often carried out in the flight process. Such extreme conditions make it very difficult for ground tests to accurately simulate the aerodynamic thermal environment.

For many years, various ground test systems which use radiation or convection as a heat source to simulate pneumatic heat, such as quartz lamp heating equipment, electric arc wind tunnels, high-temperature gas wind tunnels and the like, have been developed at home and abroad. However, the conventional thermal test method has many disadvantages in view of the new requirements of the pneumatic thermal simulation of the above-described complex structure. For example, the current test system has difficulty in combining the surface large gradient heat flow distribution simulation capability with the high impact rate nonlinear time-varying heat flow simulation capability. From the traditional test method, the high-temperature wind tunnel mostly adopts a step thermal power lifting mode to realize the non-steady thermal environment simulation, so that the complex non-linear thermal environment process with rapid change is difficult to accurately simulate; while radiant heating equipment such as quartz lamps and the like has excellent control and electric control performance and can realize nonlinear time-varying heat flow simulation with high impact rate, the large-gradient heat flow distribution on the surface of the structure is difficult to accurately simulate. And the current system is difficult to adapt to the surface heat flow loading of a large-size complex structure due to the installation form of the test system. The traditional high-temperature wind tunnel test piece has limited size, and the full-size simulation of a component assembly is difficult to realize; while radiant heating devices such as quartz lamps are installed in zones, they are difficult to adapt to complex aerodynamic profiles.

Disclosure of Invention

The invention aims to provide a thermal test method and a thermal test device for a metal fiber surface combustion structure, which can adapt to a test piece with a complex appearance.

In order to achieve the aim, the invention provides a thermal test method for a metal fiber surface combustion structure, which comprises the following steps:

a. mixing fuel gas and a gas combustion improver to form mixed gas, and conveying the mixed gas along at least one gas path;

b. igniting the mixed gas at the tail end of the gas path, and enabling the combustion flame to pass through the attachment, wherein each point of at least one surface of the attachment corresponds to each point of the heated surface of the test piece, so that the fuel gas formed by combustion is sprayed to the heated surface of the test piece to heat the heated surface;

c. and measuring the heat load parameters of the heated surface of the test piece corresponding to each gas path in real time, and controlling the flow of the mixed gas in the corresponding gas path in real time according to the heat load parameters.

According to an aspect of the present invention, in the step (b), a porous structure woven by metal fibers is used as an adherent of the mixed gas combustion flame.

According to an aspect of the present invention, in step (c), a heat load parameter threshold value of the heated surface of the test piece corresponding to each gas path in each time period is set, and when the measured heat load parameter exceeds the threshold value, the flow rate of the mixed gas in the corresponding gas path is reduced.

According to one aspect of the invention, in step (c), the heat load parameter comprises temperature or surface heat flow.

The metal fiber surface combustion structure heat test device includes: the device comprises a gas supply system, a combustion improver supply system, a combustion system, a measuring system and a control system, wherein the combustion system comprises an igniter, the combustion system further comprises an attachment, and at least one surface of the attachment is parallel or approximately parallel to a heated surface of a test piece.

According to one aspect of the invention, the attachment is a porous structure woven by metal fibers, and the surface of the attachment parallel or approximately parallel to the heated surface of the test piece is a cylindrical surface, a curved surface or a plane.

According to one aspect of the invention, the combustion system further comprises a transition duct comprising a main duct and at least one branch duct connected to an outlet end of the main duct;

the attachment body is communicated with the outlet end of the branch pipe of the transition pipe.

According to one aspect of the invention, the combustion system further comprises a proportioning valve and a mixer;

the proportional valve is positioned at the inlet end of the main pipe of the transition pipe and is respectively connected with the fuel gas supply system and the combustion improver supply system;

the mixer is disposed on the trunk pipe of the transition pipe.

According to one aspect of the invention, the gas supply system comprises a gas source and a gas supply pipe with an inlet end connected with the gas source;

and a first switch valve, a first pressure reducing valve, a first pressure gauge, a first flowmeter and a flame arrester are sequentially arranged on the fuel gas supply pipe from the inlet end to the outlet end. The first pressure gauge and the first flow meter may also be interchangeable in position.

According to one aspect of the invention, the oxidant supply system comprises a source of oxidant gas and an oxidant supply pipe connected at its inlet end to the source of oxidant gas;

and a second switch valve, a second pressure reducing valve, a second pressure gauge, a second flowmeter and a check valve are sequentially arranged on the combustion improver supply pipe from the inlet end to the outlet end. The second pressure gauge and the second flow meter may also be interchangeable in position.

According to one aspect of the invention, the measurement system comprises a sensor and a data collector, the data collector being connected to the control system.

According to one aspect of the invention, the control system comprises a computer and a flow controller, the computer being connected to the measurement system;

the flow controller is arranged on the branch pipe of the transition pipe.

According to one aspect of the present invention, the flexible feature of the attachment body woven by metal fibers as the attachment body of the mixed gas combustion flame enables the attachment body to be made into any shape. Thereby enabling the combustion surface to adapt to the complex shapes of various test pieces.

According to one scheme of the invention, the transition pipe is divided into the main trunk pipe and the branch pipes, and at least one branch pipe is arranged, so that more than one gas path for circulating the mixed gas can be provided, and the thermal test can be respectively carried out on the test pieces with different heat flow gradient requirements.

According to one aspect of the invention, a sensor is provided on the heated surface of the test piece to perform a measurement of a heat load parameter of the heated surface. Setting heat load parameter threshold values in each time period according to different time nodes, and if the heat load parameter detected by the sensor is greater than the threshold value, controlling a flow controller on each branch pipe through a computer to reduce the flow of the mixed gas in each branch pipe; if the heat load parameter detected by the sensor is less than the target value, the flow controller located on the branch pipes is controlled via the computer to increase the flow of the mixed gas in each branch pipe. Therefore, each branch pipe is independently controlled and fed back in time, the target value of the heat load is automatically tracked, and the loading of the time-varying heat load with high impact rate and strong nonlinearity is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 schematically shows a schematic view of a thermal test apparatus for a metal fiber surface combustion structure according to an embodiment of the present invention;

FIGS. 2 and 3 are schematic diagrams schematically illustrating the fitting of an adherend to a test piece according to two embodiments of the present invention;

fig. 4 schematically shows a schematic view of a thermal test apparatus for a metal fiber surface combustion structure according to another embodiment of the present invention.

Detailed Description

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 embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship that is based on the orientation or positional relationship shown in the associated drawings, which is for convenience and simplicity of description only, and does not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, the above-described terms should not be construed as limiting the present invention.

The present invention is described in detail below with reference to the drawings and the specific embodiments, which are not repeated herein, but the embodiments of the present invention are not limited to the following embodiments.

The thermal testing method of the present invention can be seen in the apparatus diagram shown in FIG. 1. In the method, firstly, fuel gas and combustion improver are mixed and conveyed. The method and the device of the invention accurately simulate the pneumatic thermal environment, so the combustion improver also can be gas, such as oxygen or directly use air. The mixture of fuel gas and combustion improver needs to be in a certain proportion. The mixed gas is conveyed downstream along the gas path, and for the heat flow distribution condition that a large gradient exists on the surface of some test pieces, more than one gas path for conveying the mixed gas can be provided, for example, as shown in fig. 4. The mixed gas is then ignited at the end of the gas path, and in order to adapt to the complex shape of the test piece, the invention provides an attachment for the flame of the mixed gas combustion. The attachment is a porous structure woven from metal fibers. Thus, a minute mesh-like structure is formed on the surface thereof, and the mixed gas passes through the pores thereof and burns on the surface thereof to form a flame, achieving an adhesion-like effect. Due to the special properties of the metal fibers, the attachment body is of a flexible structure, so that the attachment body can be designed into any shape, and can be adapted to different test piece shapes. Of course, no matter what shape the attachment itself has, at least one of the points on the surface thereof should correspond to a respective point on the heated surface of the test piece, it can be understood that at least one of the surfaces of the attachment is parallel or approximately parallel to the heated surface of the test piece, so that the combustion gas formed by the combustion is sprayed onto the heated surface of the test piece, which ensures effective heating thereof.

In the method, the heat load parameters of the heated surface of the test piece are measured in real time in the heating process, and the flow of the mixed gas in the gas path is adjusted in real time according to the heat load parameters. Specifically, the heat load parameter thresholds in different time periods are respectively set according to different time nodes. The measured heat load parameters in the method comprise temperature and surface heat flow. When the measured heat load parameter is larger than the corresponding threshold value, controlling the gas flow in the corresponding gas path to reduce; when the measured heat load parameter is smaller than the corresponding threshold value, the gas flow in the corresponding gas path is controlled to increase, so that the heat load loading capacity is controlled to be close to the target values in different time periods, and the loading of the time-varying heat load with high impact rate and strong nonlinearity is realized.

With continued reference to fig. 1, the thermal test device for the metal fiber surface combustion structure of the present invention includes a gas supply system 1, a combustion improver supply system 2, a combustion system 3, a measurement system 4, and a control system 5. The gas supply system 1 comprises a gas supply pipe 12, the inlet end of which is connected to a gas source 11. A first switch valve 13, a first pressure reducing valve 14, a first pressure gauge 15, a first flow meter 16 and a flame arrester 17 are sequentially arranged on the pipe body of the gas supply pipe 12 from the inlet end to the outlet end. Wherein the first on-off valve 13 is a hand valve. The first pressure gauge 15 and the first flow meter 16 may also be interchanged. The gas supply system 1 forms a gas path for supplying gas, and provides the specified flow of gas for the subsequent thermal test.

The oxidant supply system 2 includes an oxidant supply pipe 22, the inlet end of which is connected to a source of oxidant 21. The second on-off valve 23, the second pressure reducing valve 24, the second pressure gauge 25, the second flowmeter 26, and the check valve 27 are provided in this order from the inlet end toward the outlet end of the oxidant supply pipe 22. The oxidizer used in the apparatus of the present invention is oxygen or air, and thus the source of oxidizer gas 21 may be an oxygen cylinder or an air pump, as described above with respect to the method of the present invention. The second pressure gauge 25 and the second flow meter 26 may also be interchanged. Therefore, the combustion improver supply system 2 also forms a gas path which can provide combustion improver with specified flow for a subsequent thermal test.

The gas supply system 1 and the oxidizer supply system 2 described above provide a gas and a gaseous oxidizer, which are mixed and combusted in the combustion system 3. Specifically, combustion system 3 includes transition duct 34, upstream of main duct 34a and downstream of branch duct 34 b. Wherein, the inlet end (i.e. left end) of the main pipe 34a is provided with a proportional valve 33, and the pipe body is provided with a mixer 35. As shown in fig. 1, the proportional valve 33 is connected to both the fuel gas supply pipe 12 of the fuel gas supply system 1 and the oxidant supply pipe 22 of the oxidant supply system 2, and functions to allow the fuel gas and the oxidant to enter the combustion system 3 in a certain ratio. The mixer 35 is intended to mix the combustion gases and the oxidizer in a confined space for subsequent ignition. Because the device needs to ignite the mixed gas, the igniter 31 is arranged at the tail end of the transition pipe 34, the igniter 31 is started when the whole system is started, and the igniter is automatically closed after ignition. This step can be performed by an automated program or manually. In addition, an attachment body 32 is provided at the outlet end of the branch pipe 34b to provide attachment for the combustion flame of the mixed gas so that the surface shape thereof can be adapted to the surface shape of the heated surface of the specimen. In this embodiment, since there is only one branch tube 34b, it can also be understood that the transition tube 34 is a complete tube without distinguishing between trunk and branch portions thereof.

Specifically, the attachment 32 is a porous structure woven from metal fibers, and the principle of the structure as a flame attachment is described in detail in the above-mentioned method, and therefore, the description thereof is omitted. By utilizing the special flexibility of the metal fiber structure, the metal fiber can be made into any shape. The porous structure is used to communicate with the branch pipe 34b to receive the mixed gas conveyed by the branch pipe. Referring to fig. 1 to 3, the specimen a in fig. 1 has a flat plate shape, and thus the attachment 32 also has a flat plate shape. Thus, the mounting was made with its right side plane parallel to the heated surface of test piece a. The test piece a in fig. 2 is cylindrical, and its heated surface is the inner sidewall, so the attachment 32 is cylindrical in shape, and both are nested when installed, again in order to make the two cylindrical surfaces parallel. The test piece a in fig. 3 is a curved plate whose heated surface is a regular or irregular curved surface. Therefore, the attachment 32 is also a curved plate, and is mounted so that its right curved surface is parallel to the heat receiving curved surface of the test piece a. If the curved surface shape of the heated surface of the test piece a is too complex, the curved surface shape of the attachment 32 can be simplified to a certain extent and is approximately parallel to the heated curved surface of a, so that the processing cost of the attachment 32 is reduced, and the heating effect is not influenced. When the above embodiment is installed, a proper distance should be ensured between the attachment 32 and the test piece a, and the closer the attachment is, the better the distance is, but the heating effect and the heat flow instability caused by the contact between the inner flame of the flame and the test piece a are also avoided, and meanwhile, the collision generated in the installation process is avoided. Since the edges of the attachment body 32 may be close to the air and cause heat loss, the attachment body 32 should also be sized to ensure that the heat transfer to the heated surface of the test piece A is uniform. In particular, the area of the corresponding surface may be set to be greater than or equal to the area of the heated surface of the test piece, i.e., the projection of the attachment body 32 toward the test piece a is preferably able to completely cover the heated surface thereof, so that the heat loss at the edge position in contact with the air does not affect the thermal test. In the above embodiment, the surface of the heated surface of the test piece a has a single surface, and thus one surface of the attachment body 32 is parallel to the heated surface. However, if the surface of the heated surface of the test piece a is complex, then according to the concept of the present invention, a plurality of surfaces on the attachment 32 may be parallel or nearly parallel to the heated surface, but this approach is suitable for the case where the heated surface of the test piece is complex but has no thermal flow gradient distribution requirement. In addition, in the embodiment shown in fig. 1 to 3, the attachment body 32 has the shape of a flat plate, a cylinder, and a curved plate, respectively. However, according to the concept of the present invention, the correspondence of the attachment body to the test piece is most important to the correspondence between the faces. In the present invention, it is defined that the two surfaces are parallel or approximately parallel, that is, each point of the two surfaces corresponds to each point, so long as at least one surface of the attachment 32 can be parallel or approximately parallel to the heated surface of the test piece, and the shape of the attachment 32 can be designed according to the actual use condition (the plate in the above description about the attachment 32 is a porous plate).

With continued reference to FIG. 1, the measurement system 4 includes a sensor 41 and a data collector 42, wherein the sensor 41 is disposed on the heated surface of the test piece A to detect a heat load parameter thereon in real time. The sensor 41 is a broad concept, and is not specific to a certain sensor, and the heat load parameters to be detected in the present invention include temperature, surface heat flow, and other information. Therefore, appropriate sensing components should be selected as the sensor 41 of the present invention to detect these thermal load parameters separately. The information collected by the sensor 41 is transmitted to the control system 5 via the data collector 42. The control system 5 comprises a computer 51 and a flow controller 52, wherein the computer 51 is connected with the data collector 42 and receives the real-time information transmitted by the data collector. The flow controller 52 is provided in the branch pipe 34b of the transition pipe 34, and is controlled by the computer 51 to adjust the flow rate of the mixed gas in the branch pipe 34b in real time. The specific adjustment manner is as described in the above method description, corresponding heat load parameter thresholds can be set according to different time nodes, and when the sensor 41 detects that the surface heat load parameter is greater than or less than the threshold, the computer 51 controls the flow controller 52 to adjust the flow inside the branch pipe 34b, and the change of the flow simultaneously causes the changes of the temperature and the load, thereby realizing the function of adjusting the gas heat load. Thus, the measuring system 4 and the control system 5 act together to form an effect of automatically tracking a preset heat load target value (namely, a threshold), and the loading of the time-varying heat load with high impact rate and strong nonlinearity is realized.

The examples shown in fig. 1 to 3 are all the cases of no heat flow gradient distribution on the surface of the test piece a. While figure 4 shows an embodiment where three heat flow gradient zones are required for the heated surface of test piece a, these three gradient zones are shown as dashed rectangles in figure 4. Since the heat flow distribution has no obvious relationship with the shape of the test piece, fig. 4 illustrates a flat-plate-shaped test piece a as an example, and thus it can also be understood that three heated surfaces exist on the test piece a and are all flat. In this embodiment, the number of branch pipes 34b in the transition pipe 34 of the present invention is also three, i.e., corresponding to each heat flow gradient distribution region, which is heated separately. Of course, one adherend 32 is provided at the end of each branch pipe 34 b. Accordingly, a sensor 41 is provided on each distribution area, which is only the embodiment of fig. 4, but one sensor can be provided to measure the surface thermal load parameters of the three gradient regions, respectively, if the technical conditions permit. In addition, since there are three branch pipes 34b and the distribution areas corresponding to each branch pipe 34b have different heat flow requirements, it is necessary to provide one flow controller 52 for each branch pipe 34b to control the gas flow rate in each branch pipe 34 b. The control mode of each branch pipe 34b may be controlled according to the embodiment of fig. 1, and the time nodes of different branch pipes 34b may be different. Therefore, each branch pipe 34b is independently controlled according to the respective preset heat load target value, and the branch pipes do not interfere with each other, so that the device adapts to the condition that the surface of the test piece A has heat flow gradient distribution. Of course, since the specimen a in the embodiment shown in fig. 4 is a flat plate, the adherend 32 at the end of each of the branch pipes 34b is also a flat plate. However, if the surface of the test piece a has an irregular shape and the area of the heat flow gradient distribution is irregular, the shape of the attachment 32 at the corresponding position may be designed to correspond to the irregular shape.

In summary, the method and the device of the invention provide adhesion for mixed gas combustion flame by using the attachment body woven by metal fibers, and the flexibility of the attachment body enables the attachment body to be suitable for the surface type of the heated surface of any test piece, thereby realizing full-scale thermal test. The way of arranging the branch pipes also ensures that more than one air passage can be arranged in the method and the device, so that the thermal test can be carried out on the test piece with larger surface heat flow gradient. The method and the device can carry out accurate thermal test and force-heat coupling test on the heat-insulating material prevention and insulation structure components and the whole high-speed aircraft, particularly large-size complex structures with large surface heat load distribution gradient, high impact rate and strong nonlinearity.

The above description is only one embodiment of the present invention, and is not intended to limit the present invention, and it is apparent to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermal test method for a metal fiber surface combustion structure comprises the following steps:

b. igniting the mixed gas at the tail end of the gas path, and enabling combustion flame to penetrate through the attachment, wherein each point of at least one surface of the attachment corresponds to each point of the surface to be detected of the test piece, so that the fuel gas formed by combustion is sprayed to the heated surface of the test piece to heat the heated surface;

c. and measuring the heat load parameters of the to-be-detected surface of the test piece corresponding to each gas path in real time, and controlling the flow of the mixed gas in the corresponding gas path in real time according to the heat load parameters.

2. The thermal test method according to claim 1, wherein in the step (b), a porous structure woven from metal fibers is used as an attachment of the mixed gas combustion flame.

3. The thermal testing method according to claim 1, wherein in the step (c), a heat load parameter threshold value of the heated surface of the test piece corresponding to each gas path of each time period is set, and when the measured heat load parameter is greater than the threshold value, the flow rate of the mixed gas in the corresponding gas path is reduced; and when the measured heat load parameter is smaller than the threshold value, increasing the flow of the mixed gas in the corresponding gas path.

4. A thermal testing method according to claim 3, wherein in step (c) said heat load parameters include temperature, surface heat flow.

5. A metal fiber surface combustion structure thermal test apparatus for carrying out the thermal test method of any one of claims 1 to 4, comprising: the device comprises a gas supply system (1), a combustion improver supply system (2), a combustion system (3), a measuring system (4) and a control system (5), wherein the combustion system (3) comprises an igniter (31), and the device is characterized in that the combustion system (3) further comprises an attachment body (32), and at least one surface of the attachment body (32) is parallel or approximately parallel to the heated surface of a test piece.

6. The thermal test device according to claim 5, wherein the attachment (32) is a porous structure woven from metal fibers, and the surface shape of the attachment parallel or approximately parallel to the heated surface of the test piece is a cylindrical surface, a curved surface or a plane surface.

7. The thermal testing apparatus of claim 6, wherein the combustion system (3) further comprises a transition duct (34), the transition duct (34) comprising a main duct (34a) and at least one branch duct (34b) connected to an outlet end of the main duct (34 a);

the attachment body (32) is in communication with an outlet end of a branch pipe (34b) of the transition pipe (34).

8. The thermal testing device according to claim 7, characterized in that the combustion system (3) further comprises a proportional valve (33) and a mixer (35);

the proportional valve (33) is positioned at the inlet end of a main pipe (34a) of the transition pipe (34) and is respectively connected with the fuel gas supply system (1) and the combustion improver supply system (2);

the mixer (35) is arranged on a main pipe (34a) of the transition pipe (34).

9. The thermal testing device according to claim 5, characterized in that said gas supply system (1) comprises a gas source (11) and a gas supply pipe (12) connected at its inlet end to said gas source (11);

the gas supply pipe (12) is provided with a first switch valve (13), a first pressure reducing valve (14), a first pressure gauge (15), a first flow meter (16) and a flame arrester (17) in sequence from the inlet end to the outlet end, and the first pressure gauge (15) and the first flow meter (16) can also be exchanged in position.

10. The thermal test device according to claim 5, characterized in that said oxidant supply system (2) comprises an oxidant gas source (21) and an oxidant supply pipe (22) connected at its inlet end to said oxidant gas source (21);

and a second switch valve (23), a second pressure reducing valve (24), a second pressure gauge (25), a second flowmeter (26) and a check valve (27) are sequentially arranged on the combustion improver supply pipe (22) from the inlet end to the outlet end, and the second pressure gauge (25) and the second flowmeter (26) can also be exchanged in position.

11. A thermal testing device according to claim 5, characterized in that the measuring system (4) comprises a sensor (41) and a data collector (42), the data collector (42) being connected to the control system (5).

12. The thermal testing device according to claim 7, characterized in that said control system (5) comprises a computer (51) and a flow controller (52), said computer (51) being connected to said measuring system (4);

the flow controller (52) is provided on a branch pipe (34b) of the transition pipe (34).