A Test Method for Gas / Liquid Fuel Laminar Flame Speed Based on the Heat Flux Method

Abstract

The present invention relates to fuel testing technology, aiming to provide a method for measuring the laminar flame speed of gas / liquid fuels based on the heat flux method. The method includes: various gaseous raw materials enter a premixer for sufficient mixing, and are then ignited by an ignition device above the disc to form a stable one-dimensional planar flame; measure the temperature distribution of the furnace disc at different premixed unburned gas flow rates, obtain the quadratic coefficient C through fitting calculation, perform a linear fit on the variation of C with the premixed unburned gas flow rate, and obtain the flow rate value at C = 0, which is the laminar flame speed value SL of the fuel. This device can obtain a one-dimensional adiabatic planar flame, and the flame combustion speed is not affected by factors such as flame stretching, flame curvature, and heat loss, thereby avoiding the experimental uncertainty introduced by the extrapolation method in traditional measurement methods and having higher accuracy; the laminar flame speed of liquid fuels can be measured using the liquid evaporation system.

Description

Technical Field

[0001] The present invention relates to fuel testing technology, and more particularly to a method for measuring laminar flame speed of fuel based on the heat flux method. Background Art

[0002] Laminar flow is a flow state of a fluid, which refers to the fluid flowing in layers. When the fluid flows slowly in a pipe, it presents laminar flow, and its particles move smoothly in a straight line along the direction parallel to the pipe axis. The flow velocity of the fluid is the largest at the center of the pipe and the smallest near the wall. When the stationary gas or the laminar flow gas (Re < 2100) in the pipe is ignited, the formed flame is called a laminar flame. The laminar flame speed excludes the influence of turbulent transport and is an important basic combustion parameter characterizing the fuel combustion reaction characteristics, which is the premise and basis of complex combustion phenomena, such as flame stability, flame height, and pollutant emissions. In addition, the laminar flame speed is also important basic data for verifying and optimizing chemical reaction kinetic models. Therefore, accurately measuring the laminar flame speed is the basis for studying the fuel combustion reaction characteristics.

[0003] The laminar flame speed is defined as the speed of the high-temperature combustion flame front relative to the incoming unburned gas in the normal direction in a one-dimensional infinite space. On this basis, a variety of testing techniques have been developed to measure the laminar burning speed of fuels, including the Bunsen burner method, the stagnation flow method, the counterflow flame method, the spherical explosion method, etc. In these common measurement methods, the flame shape will be distorted due to flame stretching, flame surface curvature, or heat loss, thereby affecting the accurate determination of the laminar flame speed. To eliminate the influence of flame stretching and heat loss, the extrapolation method is generally used to extrapolate to zero stretching rate and adiabatic state, but this method often introduces a large experimental uncertainty and affects the accuracy of the measurement results.

[0004] By definition, accurate measurements of laminar flame speed can be obtained from an ideal one-dimensional adiabatic planar flame. However, it is difficult to directly achieve an adiabatic planar flame. In 1993, de Goey and his collaborators introduced the so-called heat flux method to stabilize the adiabatic planar flame and measure the laminar flame speed. The basic principle of the heat flux method is that when a one-dimensional planar flame is stabilized on a disk, the heat obtained by the incoming gas passing through the furnace disk is balanced with the heat transfer from the flame to the furnace disk, that is, when all the heat transfer from the flame is used to heat the unburned gas, an adiabatic and stable planar flame can be obtained. Compared with general measurement techniques, the heat flux method can directly obtain an adiabatic and unstrained flame, thus avoiding the need to correct measurement data using extrapolation or other analytical means, and reducing the experimental uncertainty. Currently, the measurement objects of conventional heat flux method test systems are basically gaseous hydrocarbon fuels, and there is little research on the measurement of the laminar flame speed of liquid fuels. In addition, for new carbon-free fuels such as ammonia, whose combustion speed is much lower than that of hydrocarbon fuels, it is difficult to obtain a stable adiabatic planar flame using the conventional heat flux method. Therefore, it is necessary to upgrade and optimize the existing fuel laminar flame speed test methods and devices based on the heat flux method. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a fuel laminar flame speed test method and device based on the heat flux method.

[0006] To solve the technical problem, the solution of the present invention is:

[0007] Provide a gas / liquid fuel laminar flame speed test method based on the heat flux method, including the following steps:

[0008] (1) Use gas cylinders to provide the required inert carrier gas and oxidant, and use gaseous fuel or liquid fuel for testing; the computer controls the mass flow meters on the fuel delivery pipeline according to the set fuel blending ratio and fuel-oxidant equivalence ratio to adjust the flow rates of each raw material.

[0009] Among them, the gaseous fuel is provided by a gas cylinder, and the gaseous fuel is directly mixed with the inert gas and oxidant gas in the premixer; while the liquid fuel is provided by a liquid fuel storage tank pressurized by an inert gas, and the mixture composed of the liquid fuel and the inert gas is first vaporized in a controlled evaporation mixer and then sent to the premixer to be mixed with the oxidant gas.

[0010] (2) After all the gaseous raw materials enter the premixer for full mixing, the premixed unburned substances are sent to the bottom inlet of the heat flux furnace; after being evenly distributed by the air distribution plate at the bottom of the heat flux furnace, they pass through the furnace chamber, furnace head and furnace disk from bottom to top in turn, and are finally ignited by the ignition device above the disk to form a stable one-dimensional planar flame.

[0011] (3) By embedding multiple thermocouples at different radial distances from the center in the furnace plate, the temperature distribution T of the furnace plate is measured i , i = 1, 2, 3... n; perform a quadratic polynomial fitting on the temperature distribution of the furnace plate: T r = T0 + Cr 2 ;

[0012] In the formula, T r is the temperature at the disk radius r, T0 is the temperature at the center of the furnace plate, and r is the radial distance from the target point on the disk to the center of the furnace plate; the quadratic coefficient C is obtained through calculation;

[0013] (4) Adjust the flow rate of the premixed unburned substances, and repeat step (3) to obtain the quadratic coefficient C at different flow rates;

[0014] (5) Perform a linear fitting on the variation of the quadratic coefficient C with the flow rate of the premixed unburned substances to obtain the flow rate value at C = 0, which is the laminar flame speed value S of the fuel L .

[0015] As a preferred solution of the present invention, the step (5) further includes:

[0016] (5.1) Calculate the measurement sensitivity s according to the formula ;

[0017] (5.2) Calculate the error caused by the temperature measurement fluctuation of the thermocouple according to the formula where,

[0018]

[0019] In the formula, T i is the temperature value measured by the i-th thermocouple, r i is the radial distance from the i-th thermocouple to the center of the furnace plate, and N is the number of thermocouples; is the mean square of r i ;

[0020] Calculate the error caused by the flow rate fluctuation controlled by the flowmeter according to the formula where,

[0021] In the formula, ΔF i is the standard error of each flowmeter provided by the manufacturer, and F tot is the total flow rate of the unburned mixture;

[0022] [[ID=Z4]]According to obtain the experimental measurement laminar flame speed error ΔS L , which is used to correct the laminar flame speed value S obtained in step (5) L .

[0023] As a preferred embodiment of the present invention, the premixed unburned substances are provided by a fuel supply and premixing unit, which includes a premixer, an inert carrier gas cylinder, an oxidant cylinder, and at least one of a gaseous fuel cylinder or a liquid fuel storage tank; the inert carrier gas cylinder, the oxidant cylinder, and the gaseous fuel cylinder are respectively connected to the premixer through pipelines; alternatively, the oxidant cylinder is connected to the premixer through a pipeline, the inert carrier gas cylinder is respectively connected to the liquid fuel storage tank and a controlled evaporation mixer through pipelines, and the controlled evaporation mixer is connected to the premixer through a pipeline.

[0024] As a preferred embodiment of the present invention, the heat flux furnace is composed of a furnace chamber, a burner head, and a furnace plate; the furnace chamber is a cylindrical cavity structure with a wind distribution plate at the lower part, and the closed end at the bottom is provided with an inlet for premixed unburned substances and is connected to the premixer through a pipeline; the outer wall of the furnace chamber is surrounded by a constant temperature jacket and is connected to a constant temperature heat source through a pipeline; the hollow burner head is fixedly installed at the open end at the top of the furnace chamber, and the inner cavity edge thereof has a curve shape that tapers upward; an annular heating groove is provided at the edge of the open end on the upper side of the burner head and is connected to a constant temperature heat source through a pipeline; the furnace plate is nested and installed at the open end on the upper side of the burner head, and its side edge covers the annular heating groove and realizes the sealing of the burner head; a plurality of through combustion holes are densely arranged on the disc-shaped furnace plate, and a plurality of thermocouples are arranged at different radial distances.

[0025] As a preferred embodiment of the present invention, the constant temperature heat source is two independent constant temperature water / oil baths, which are respectively connected to the constant temperature jacket of the furnace chamber and the annular heating groove of the burner head through pipelines.

[0026] As a preferred embodiment of the present invention, a plurality of through holes are uniformly and densely arranged on the wind distribution plate and are fixedly installed on a fixed support member on the side wall of the furnace chamber.

[0027] As a preferred embodiment of the present invention, the lower edge of the burner head is provided with a concave counterbore, and a rubber sealing ring is embedded on the side edge of the counterbore. The open end at the top of the furnace chamber is sleeved in the counterbore of the burner head; the upper edge of the burner head is provided with a concave counterbore, and the furnace plate is nested and installed in the counterbore, and a ceramic ring is provided between the two to block heat transfer; the combustion holes on the furnace plate are uniformly arranged in a six-sided lattice manner.

[0028] As a preferred embodiment of the present invention, the thermocouple is inserted into the mounting hole on the furnace plate from bottom to top, and the signal line at the tail end of the thermocouple is arranged in the inner cavity of the burner head, passes through the lead hole provided on the side wall of the burner head, and is sequentially connected to a data acquisition instrument and an upper computer.

[0029] As a preferred embodiment of the present invention, flow meters are respectively provided on the outlet pipelines of the cylinders and the liquid fuel storage tank, and each flow meter and the controlled evaporation mixer are respectively connected to an upper computer through signal lines.

[0030] As a preferred embodiment of the present invention, the premixer is a tubular structure made of polytetrafluoroethylene.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The device of the present invention can obtain a one-dimensional adiabatic planar flame, and the flame burning speed is not affected by factors such as flame stretching, flame curvature, and heat loss, thereby avoiding the experimental uncertainty introduced by the extrapolation method in traditional measurement methods and having higher accuracy.

[0033] 2. The present invention provides a configuration of a liquid fuel storage tank and a controlled evaporation mixer, and the laminar flame speed of the liquid fuel can be measured by using the liquid evaporation system.

[0034] 3. The present invention has carried out a refined design on the structure of the disc, effectively solving the problem that the cellular flame phenomenon occurs when measuring the laminar flame speed of certain specific fuels and the accurate measurement cannot be carried out; the disc can adopt a higher disc temperature to improve the stability of the planar flame of fuels with low burning speeds. Description of the Drawings

[0035] Figure 1 Schematic diagram of the test device of the present invention (for gaseous fuel);

[0036] Figure 2 Schematic diagram of the test device of the present invention (for liquid fuel);

[0037] Figure 3 Schematic diagram of the structure of the heat flux furnace;

[0038] Figure 4 Schematic diagram of the furnace disc of the heat flux furnace.

[0039] Reference numerals: 1 high-purity gas cylinder, 2 gas mass flowmeter, 3 premixer, 4 heat flux furnace, 5 constant temperature water / oil bath, 6 constant temperature oil bath, 7 data acquisition instrument, 8 computer, 9 liquid fuel storage tank, 10 liquid mass flowmeter, 11 controlled evaporation mixer (CEM); 4-1 furnace disc, 4-2 heating tank, 4-3 signal wire of thermocouple, 4-4 furnace chamber, 4-5 constant temperature jacket, 4-6 air distribution plate. Detailed Embodiments

[0040] In this application, the serial numbers assigned to components themselves, such as "first", "second", etc., are only used to distinguish the described objects and do not have any sequential or technical meanings. The terms "connection" and "coupling" used in this application, unless otherwise specifically stated, both include direct and indirect connections (couplings). In the description of this application, it should be understood that the orientation or positional relationships indicated by terms such as "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application.

[0041] In this application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature is at a higher horizontal level than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature is at a lower horizontal level than the second feature.

[0042] The following will specifically describe the embodiments of the present invention in detail with reference to the drawings:

[0043] The present invention first constructs a fuel laminar flame speed test device based on the heat flux method, including a fuel supply and premixing unit, a combustion unit, and a control unit; wherein,

[0044] The fuel supply and premixing unit includes a premixer 3 and a high-purity gas cylinder 1, Figure 1 wherein the high-purity gas cylinder 1 includes an inert carrier gas cylinder, an oxidant gas cylinder, and a gaseous fuel cylinder, and the inert carrier gas cylinder, the oxidant gas cylinder, and the gaseous fuel cylinder are respectively connected to the premixer 3 through pipelines. Figure 2 The high-purity gas cylinder 1 in does not include a gaseous fuel cylinder, and instead uses a liquid fuel storage tank as the fuel source. The oxidant gas cylinder is connected to the premixer 3 through a pipeline, the inert carrier gas cylinder is connected to the liquid fuel storage tank 9 and the controlled evaporation mixer 11 through pipelines respectively, and the controlled evaporation mixer 11 is connected to the premixer 3 through a pipeline. In the present invention, the inert carrier gas can be nitrogen, and the oxidant can be oxygen. As an optional example, the premixer is a polytetrafluoroethylene tube about 3 meters long. After the liquid fuel flows through the flowmeter, it collides with nitrogen at the piston at the top of the controlled evaporation mixer CEM and breaks into small droplets; the aerosol composed of the small droplets and nitrogen descends to the CEM heating device and is completely vaporized in an environment of 200 °C.

[0045] The combustion unit includes a heat flux furnace 4 and a constant temperature heat source; the heat flux furnace 4 consists of a furnace chamber 4-4, a burner head, and a furnace disc; the furnace chamber 4-4 is a cylindrical cavity structure, with an air distribution plate 4-6 provided at the lower part, and a premixed unburned gas inlet provided at the closed end of the bottom and connected to the premixer 3 through a pipeline. A number of through holes are evenly and densely distributed on the air distribution plate 4-6, and it is fixedly installed on the fixed support member on the side wall of the furnace chamber. The air distribution plate 4-6 can make the premixed unburned gas reach a uniform distribution at the furnace chamber outlet within a certain speed range, and the fixed support member can be selected as a step or a support frame provided on the inner wall of the furnace chamber.

[0046] The outer wall of the furnace chamber 4-4 is surrounded by a constant temperature jacket 4-5, and is connected to the constant temperature heat source through a pipeline to ensure the constant temperature of the premixed unburned gas in the furnace chamber. The hollow burner head is fixedly installed at the top open end of the furnace chamber 4-4, and the edge of its internal cavity has a curve shape that tapers upward; an annular heating groove 4-2 is provided at the edge of the upper side opening end of the burner head, and is connected to the constant temperature heat source through a pipeline. The lower edge of the burner head is provided with a concave counterbore, and a rubber sealing ring is embedded on the side edge of the counterbore. The top open end of the furnace chamber 4-4 is sleeved in the counterbore of the burner head. The constant temperature heat source can be selected as two independent constant temperature water baths, for example, a constant temperature water / oil bath 5 is connected to the constant temperature jacket of the furnace chamber 4-4 through a pipeline, and a constant temperature oil bath 6 is connected to the heating groove 4-2 of the burner head through a pipeline.

[0047] The disc-shaped furnace disc 4-1 is nested and installed at the upper side opening end of the burner head, and its side edge covers the heating groove 4-2 and realizes the sealing of the burner head; a number of through combustion holes are densely distributed on the furnace disc 4-1 and are evenly arranged in a six-sided lattice manner. A plurality of thermocouples are arranged on the furnace disc at different radial distances, and the thermocouples are inserted into the mounting holes on the furnace disc 4-1 from bottom to top. The signal wires at their tails are arranged in the inner cavity of the burner head and pass through the lead holes provided on the side wall of the burner head. The upper edge of the burner head is provided with a concave counterbore, and the furnace disc 4-1 is nested and installed in the counterbore, and a ceramic ring is provided between the two to block heat transfer.

[0048] The control unit includes a data acquisition instrument 7 and a computer 8 at the upper level. The former is connected to the thermocouples on the furnace disc 4-1 through signal wires, and the latter is connected to the data acquisition instrument 7 through signal wires. Gas mass flow meters 2 or liquid mass flow meters 10 are respectively provided on the outlet pipelines of the inert gas cylinder, the oxidant gas cylinder, the gaseous fuel cylinder, and the liquid fuel storage tank 9. Each flow meter and the controlled evaporation mixer 11 are respectively connected to the computer 8 through signal wires, and operations such as flow control, temperature data reading, and emergency stop in case of danger can be realized.

[0049] Using this test device, the present invention proposes a method for realizing the measurement of the laminar flame speed of fuel by the heat flux method, including the following steps:

[0050] (1) An inert carrier gas and an oxidant are provided by gas cylinders. The gaseous fuel is provided in the form of high-pressure gas cylinders, and the liquid fuel is provided by a liquid fuel storage tank 9 pressurized with an inert gas. The gaseous fuel is directly mixed with the inert gas and the oxidant gas in a premixer 3. The mixture of the liquid fuel and the inert gas is first vaporized in a controlled evaporation mixer 11 and then sent to the premixer 3 to be mixed with the oxidant gas. A computer 9 controls the mass flow meters on each pipeline according to the given fuel-oxidant equivalence ratio and fuel blending ratio to adjust the flow rates of the respective raw materials.

[0051] (2) After the gaseous raw materials in each branch enter the premixer 3 for thorough mixing, the premixed unburned substances are sent to the bottom inlet of a thermal flow furnace 4, evenly dispersed by a wind distribution plate 4-6, and then sequentially pass through a furnace chamber 4-4, a burner head, and a furnace plate 4-1. Finally, they are ignited by an ignition device above the plate to form a one-dimensional planar flame.

[0052] (3) The temperature distribution T of the furnace plate 4-1 is measured by multiple thermocouples embedded at different radial distances in the furnace plate 4-1 i , where i = 1, 2, 3... n. A quadratic polynomial fitting is performed on the furnace plate temperature distribution: T r = T0 + Cr 2 ; In the formula, T r is the temperature at the disk radius r, T0 is the temperature at the center of the furnace plate, and r is the radial distance from the target point on the disk to the center of the furnace plate. The quadratic coefficient C is obtained through calculation.

[0053] (4) Adjust the flow rate of the premixed unburned substances, and repeat step (3) to obtain the quadratic coefficient C at different flow rates.

[0054] (5) Perform a linear fitting on the variation of the quadratic coefficient C with the flow rate of the premixed unburned substances to obtain the flow rate value at C = 0, which is the laminar flame speed value S of the fuel L .

[0055] Further, (5.1) Calculate the measurement sensitivity s according to the formula .

[0056] (5.2) Calculate the error caused by the temperature measurement fluctuation of the thermocouple according to the formula where

[0057]

[0058] In the formula, T i is the temperature value measured by the i-th thermocouple, r i is the radial distance from the i-th thermocouple to the center of the furnace plate, and N is the number of thermocouples; is the mean square value of r i . ​

[0059] According to the formula calculate the error caused by the flow rate fluctuation of the flowmeter control In the formula, ΔF i is the standard error of each flowmeter provided by the manufacturer, and F tot is the total flow rate of the unburned mixture;

[0060] According to obtain the experimental measurement error AS of the laminar flame speed L , which is used to correct the laminar flame speed value S obtained in step (5) L for correction.

[0061] A more specific description and exemplary embodiments are as follows:

[0062] Through theoretical analysis, it can be known that the temperature distribution of the disc of the furnace plate after being heated by the flame is a parabolic function of the radius. Specifically, it can be measured by a thermocouple and the quadratic coefficient C can be obtained through fitting calculation. Its numerical value is related to the flow rate of the premixed unburned matter. The computer controls the mass flowmeter to adjust the speed of the premixed unburned matter, and the values of the quadratic coefficient C at different flow rates are obtained by fitting. According to theoretical analysis, when the flow rate of the unburned matter is not much different from the laminar flame speed, the quadratic coefficient C changes approximately linearly with the flow rate. Perform a linear fit on the change of the quadratic coefficient C value with the flow rate of the premixed gas, and finally the flow rate of the premixed gas when C = 0 can be obtained by interpolation. At this time, the temperature distribution of the entire furnace plate tends to be uniform, and the heat loss of the flame can be compensated by the heat gain of the unburned gas mixture, thereby obtaining a one-dimensional adiabatic planar flame. According to the definition, the fuel laminar flame speed at this time is equal to the speed of the premixed incoming gas.

[0063] When the liquid fuel is used in the present invention, a liquid evaporation platform needs to be incorporated into the gas supply system to completely vaporize the liquid fuel before entering the combustion system, and at the same time replace the gas flowmeter with a liquid flowmeter. The core component of the liquid evaporation platform is the Controlled Evaporator Mixer (CEM for short). During operation, the liquid fuel collides with an inert gas (such as N2) at the top piston of the CEM and breaks into small droplets; the nitrogen aerosol carrying the small droplets is completely vaporized under the condition of 200 °C and finally sent into the premixer to mix with the oxidant gas.

[0064] The temperature of the constant temperature water bath / oil bath 5 is set to the initial experimental temperature T u , and sufficient heat exchange is carried out through the constant temperature jacket to keep the initial temperature of the unburned matter constant. The constant temperature oil bath 6 maintains the temperature T of the disc edge p of the disc edge constant through the heating tank around the furnace plate to avoid errors caused by external temperature changes. The temperature T of the constant temperature bath connected to the furnace jacket uSet the initial temperature according to the experiment, usually set to 25℃. If the initial temperature is greater than 100℃, the medium water in the bath needs to be replaced with dimethyl silicone oil, which can work at a maximum of 300℃. The temperature of the constant temperature oil bath connected to the heating tank of the furnace is T p Generally speaking, it is better than T u For example, when the measurement object is a conventional hydrocarbon fuel at 1 atm and 25°C, T p It is usually set to 90℃. When measuring the laminar flame speed of NH3+air at room temperature and pressure, the disc temperature T p To ensure that the flat flame is stable above the furnace plate, the plate temperature can be selected as 140℃.

[0065] The furnace plate 4-1 is a perforated brass disc, 2-3 mm thick and 20-30 mm in diameter. The holes are evenly distributed in a six-sided lattice pattern. The holes are 0.3-0.5 mm in diameter, and the spacing between them is 0.4-0.7 mm. Refined processing of the disc structure effectively suppresses the generation of cell flames. Eight thermocouples are embedded in the eight holes at different radii from the center of the disc to measure the temperature distribution on the disc. Figure 4 Several mounting holes for installing thermocouples are exemplarily indicated in the figure. The distances shown in the figure represent the installation positions of the thermocouples. Of course, the insertion positions of the thermocouples can also be changed according to the test plan. The combustion holes of the furnace plate are not shown in the figure.

Claims

1. A method for measuring the laminar flame speed of gas / liquid fuel based on the heat flux method, characterized in that it includes the following steps: (1) Use gas cylinders to provide the required inert carrier gas and oxidant, and use gas fuel or liquid fuel for testing; the computer controls the mass flowmeter on the fuel delivery pipeline according to the set fuel blending ratio and fuel-oxidant equivalence ratio to adjust the flow rate of each raw material. Among them, the gas fuel is provided by a gas cylinder, and the gas fuel is directly mixed with the inert gas and oxidant gas in the premixer; while the liquid fuel is provided by a liquid fuel storage tank pressurized by an inert gas. The mixture composed of the liquid fuel and the inert gas is first vaporized in a controlled evaporation mixer and then sent to the premixer to be mixed with the oxidant gas. (2) After all the gaseous raw materials enter the premixer for full mixing, the premixed unburned substances are sent to the bottom inlet of the heat flux furnace; after being evenly distributed by the air distribution plate at the bottom of the heat flux furnace, they pass through the furnace chamber, furnace head and furnace plate from bottom to top in sequence, and are finally ignited by the ignition device above the disc to form a stable one-dimensional planar flame. The heat flux furnace is composed of a furnace chamber, a furnace head and a furnace plate; the furnace chamber is a cylindrical cavity structure with an air distribution plate at the lower part, and its bottom closed end is provided with an inlet for premixed unburned substances and is connected to the premixer through a pipeline; the outer wall of the furnace chamber is surrounded by a constant temperature jacket and is connected to a constant temperature heat source through a pipeline; the hollow furnace head is fixedly installed at the top open end of the furnace chamber, and the inner cavity edge thereof has a curve shape that tapers upward; an annular heating groove is provided at the edge of the upper side opening end of the furnace head and is connected to a constant temperature heat source through a pipeline; the furnace plate is nested and installed at the upper side opening end of the furnace head, and its side edge covers the annular heating groove and realizes the sealing of the furnace head; a number of through combustion holes are densely arranged on the disc-shaped furnace plate, and a plurality of thermocouples are arranged at different radial distances. The lower edge of the furnace head is provided with a concave counterbore, and a rubber sealing ring is embedded on the side edge of the counterbore. The top open end of the furnace chamber is sleeved in the counterbore of the furnace head; the upper edge of the furnace head is provided with a concave counterbore, and the furnace plate is nested and installed in the counterbore, and a ceramic ring is provided between the two to block heat transfer; the combustion holes on the furnace plate are evenly arranged in the manner of a six-sided lattice. The thermocouple is inserted into the mounting hole on the furnace plate from bottom to top, and the signal line at the tail end of the thermocouple is arranged in the inner cavity of the furnace head, passes through the lead hole provided on the side wall of the furnace head, and is sequentially connected to a data acquisition instrument and an upper computer. (3) By embedding multiple thermocouples at different radial distances from the center in the furnace plate, the temperature distribution T of the furnace plate is measured i , where i = 1, 2, 3... n; perform a quadratic polynomial fitting on the temperature distribution of the furnace plate: T r = T0 + Cr 2 ; where T r is the temperature at the disk radius r, T0 is the temperature at the center of the furnace disk, and r is the radial distance from the target point on the disk to the center of the furnace disk; the quadratic coefficient C is obtained by calculation; (4) Adjust the flow rate of the premixed unburned substances, and repeat step (3) to obtain the quadratic coefficient C at different flow rates. (5) Perform a linear fit on the variation of the quadratic term coefficient C with the velocity of the premixed unburned flow to obtain the magnitude of the velocity at C = 0, which is the laminar flame speed value S of the fuel. L 。 2. The method according to claim 1, wherein The step (5) further includes: (5.1) Calculate the measurement sensitivity s according to the formula ​ (5.2) According to the formula Calculate the error caused by the temperature measurement fluctuation of the thermocouple where where T i is the temperature value measured by the i-th thermocouple, and r i is the radial distance from the i-th thermocouple to the center of the stove top. N is the number of thermocouples; is r i the mean square value of; According to the formula Calculate the error caused by the flow rate fluctuation of the flowmeter control In the formula, ΔF i is the standard error of each flowmeter provided by the manufacturer, and F tot is the total flow rate of the unburned mixture; According to the experimental measurement error ΔS of the laminar flame speed is obtained L , which is used to correct the laminar flame speed value S obtained in step (5) L for correction.

3. The method according to claim 1, wherein The premixed unburned substances are provided by a fuel supply and premixing unit, and the fuel supply and premixing unit includes at least one of a premixer, an inert carrier gas cylinder, an oxidant cylinder, and a gas fuel cylinder or a liquid fuel storage tank; the inert carrier gas cylinder, the oxidant cylinder and the gas fuel cylinder are respectively connected to the premixer through pipelines; or, the oxidant cylinder is connected to the premixer through a pipeline, the inert carrier gas cylinder is connected to the liquid fuel storage tank and the controlled evaporation mixer through pipelines respectively, and the controlled evaporation mixer is connected to the premixer through a pipeline.

4. The method according to claim 1, wherein The constant temperature heat source is two independent constant temperature water / oil baths, which are respectively connected to the constant temperature jacket of the furnace chamber and the annular heating groove of the burner head through pipelines.

5. The method according to claim 1, wherein A number of through holes are evenly distributed on the air distribution plate, and the air distribution plate is fixedly installed on the fixed support member on the side wall of the furnace chamber.

6. The method according to claim 1, characterized in that, Flow meters are respectively arranged on the outlet pipelines of the gas cylinder and the liquid fuel storage tank, and each flow meter and the controlled evaporation mixer are respectively connected to the upper computer through signal lines.

7. The method according to claim 1, wherein The premixer is a tubular structure made of polytetrafluoroethylene.

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