Method for measuring the work function of the emitter of a thermionic energy converter

Abstract

This invention discloses a method for measuring the work function of the emitter in a thermionic converter, enabling convenient and efficient determination of the emitter's work function. The method includes: acquiring the current-voltage characteristic curves of the emitter electrode material at multiple different emitter temperatures; determining the inflection point current density at the inflection point of each current-voltage characteristic curve; determining the effective electron transport coefficient of the emitter surface at each emitter temperature based on the inflection point current density and the multiple current-voltage characteristic curves; and determining the work function of the emitter at multiple different emitter temperatures based on the multiple different emitter temperatures and the corresponding effective electron transport coefficients. In a real-world operating environment close to that of the thermionic converter emitter material, accurate current-voltage characteristic data can be easily obtained, allowing for the determination of the emitter's work function under real-world operating conditions.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of thermionic power generation technology, specifically to a method for measuring the emitter work function of a thermionic energy converter. Background Technology

[0002] A thermionic energy converter (TEC) is a device that directly converts thermal energy into electrical energy based on the principle of thermionic emission. Under electric arc conditions, the emitter of the TEC absorbs heat and emits electrons. The emitted electrons pass through cesium plasma and reach the surface of the receiver. When a load is connected between the emitter and receiver, a circuit is formed to perform work and generate electricity.

[0003] As one of the core components of a thermionic energy converter, the electrode material of the emitter has a significant impact on power generation efficiency and operational life. The work function of the electrode material is an important parameter for evaluating the material. In TEC, due to the adsorption of cesium on the electrode surface, studying the work function of the electrode material after cesium adsorption (i.e., the effective work function) is more important than its vacuum work function. Summary of the Invention

[0004] According to one aspect of the present invention, a method for measuring the work function of the emitter of a thermionic energy converter is provided to conveniently and efficiently determine the work function of the emitter. The thermionic energy converter includes an emitter, a receiver, and a plasma, wherein the plasma is disposed between the emitter and the receiver, and electrons emitted from the emitter reach the receiver via the plasma. The measurement method includes: acquiring the work function of the emitter electrode material at multiple different emitter temperatures T. E The current-voltage characteristic curves are obtained; based on each current-voltage characteristic curve, the inflection point current density j at the inflection point of each curve is determined. b Based on the current density at each inflection point and multiple current-voltage characteristic curves, the emitter temperature T is determined. E The effective electron transport coefficient of the corresponding emitter surface Based on multiple different emitter temperatures T E and the corresponding effective electron transport coefficient Determine the emitter at multiple different emitter temperatures T E Work function under

[0005] The measurement method in this embodiment of the invention only requires obtaining the current-voltage characteristic curve of the emitter of the thermionic energy converter. Combined with the theoretical basis of the thermionic energy converter, the work function of the emitter of the thermionic energy converter under near-real operating conditions can be calculated based on the obtained current-voltage characteristic data. The method is simple and convenient to use. Attached Figure Description

[0006] Other objects and advantages of the invention will become apparent from the following description of embodiments of the invention with reference to the accompanying drawings, and will help to provide a comprehensive understanding of the invention.

[0007] Figure 1 This is a schematic diagram illustrating the working principle of a thermionic energy converter according to an embodiment of the present invention.

[0008] Figure 2 This is a flowchart illustrating a method for measuring the emitter work function according to an embodiment of the present invention.

[0009] Figure 3 This is a graph showing the current-voltage characteristics of a thermionic energy converter at different emitter temperatures according to an embodiment of the present invention.

[0010] Figure 4 This is a schematic flowchart illustrating the determination of the effective electron transport coefficient according to an embodiment of the present invention.

[0011] Figure 5 This is a schematic diagram illustrating the principle of electron movement in a thermionic energy converter according to an embodiment of the present invention.

[0012] Figure 6 This is under different target current densities according to an embodiment of the present invention. Value scatter plot.

[0013] It should be noted that the accompanying drawings are not necessarily drawn to scale, but are shown only in a schematic manner without affecting the reader's understanding. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only one embodiment of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0015] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person with ordinary skill in the art to which this application pertains. Where the terms "first," "second," etc., are used throughout the text, they are used only to distinguish similar objects and should not be construed as indicating or implying their relative importance, order of precedence, or implicitly specifying the number of technical features indicated. It should be understood that the data described by "first," "second," etc., can be interchanged where appropriate. Where "and / or" appears throughout the text, it means including three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution that satisfies both A and B. Furthermore, for ease of description, spatial relative terms such as "above," "below," "top," "bottom," etc., may be used here, only to describe the spatial positional relationship between one device or feature as shown in the figure and other devices or features. It should be understood that this also includes different orientations in use or operation besides those shown in the figure.

[0016] Thermionic energy converters can be combined with various heating devices; for example, they can be combined with nuclear reactor fission energy to create a thermionic reactor power source. Figure 1 As shown, the thermionic energy converter includes an emitter 10, a receiver 20, and a cesium source 30. The cesium source 30 fills the electrode gap between the emitter 10 and the receiver 20 with cesium vapor. The cesium vapor is ionized by electron collisions between the emitter 10 and the receiver 20, forming plasma 31, thus eliminating the potential barrier for electron transport. The nuclear reactor 100 can supply heat to the emitter 10. When the emitter 10 is heated to a high temperature, it emits electrons 40. The electrons 40 pass through the plasma 31 and reach the surface of the receiver 20. The emitter 10 and the receiver 20 serve as the two poles of a power source. When a load 50 is connected between the emitter 10 and the receiver 20, a closed loop is formed to perform work.

[0017] For the work function of emitter and receiver electrode materials, conventional measurement methods are mainly divided into two categories: absolute measurement methods and relative measurement methods. Absolute measurement methods include ultraviolet photoelectron spectroscopy (UPS), electron beam blocking potential method, and field emission blocking potential method; relative measurement methods include Kelvin probe force microscopy (KPFM) method and hot cathode emission blocking potential method. Currently, the most widely used and mature measurement methods are the UPS and Kelvin probe methods.

[0018] The inventors of this invention discovered that the work function of electrode materials is particularly sensitive to changes in material structure and composition, as well as surface physical and chemical properties. Therefore, work function testing of the emitter should closely approximate its actual operating environment. However, under arc conditions, the operating environment of the emitter in a thermionic energy converter is harsh. The emitter temperature is typically above 1500K, and cesium vapor at 100–400 Pa is filled between the emitter and receiver electrodes, resulting in the adsorption of a certain amount of cesium atoms on the emitter surface. Therefore, it is difficult to accurately measure the emitter work function under these real-world operating conditions using the conventional work function measurement methods described above.

[0019] Specifically, the temperature of the emitter in a thermionic energy converter is usually above 1500K. However, the cost of in-situ heating of the electrode material in UPS and Kelvin probe testing devices is very high, and the UPS probe is difficult to operate normally at ultra-high temperatures. In the Kelvin test, the melting point of the Au probe is below 1400K, which means that the work function results of UPS and Kelvin probe tests cannot match the actual service environment of the emitter electrode material.

[0020] UPS testing requires the sample to be in a high vacuum environment. Cesium adsorption can be addressed to some extent by pre-adsorbing cesium atoms onto the electrode material sample before measurement. However, the uncertainty of cesium atom desorption during sample transfer, the amount of adsorbed cesium atoms, and the surface state means this method is not entirely suitable for measuring the work function of the emitter in a thermionic converter. Furthermore, the Au probe is severely corroded by cesium vapor during Kelvin probe testing, affecting calibration values. Therefore, the Kelvin probe method cannot be used to accurately measure the work function of an emitter with cesium adsorption.

[0021] Furthermore, the emitter surface has a plasma sheath, and existing measurement devices, such as the UPS and Kelvin probe test devices, struggle to create a similar plasma boundary environment as the emitter surface. Moreover, setting up such measurement devices is costly and time-consuming.

[0022] In summary, there is currently no suitable method for measuring the work function of a thermionic converter emitter under service conditions close to those of a real-world service environment. Therefore, embodiments of the present invention provide a method for measuring the work function of a thermionic converter emitter under conditions close to actual service conditions.

[0023] like Figure 2 As shown, the method for measuring the emitter work function of the thermionic energy converter in this embodiment of the invention includes the following steps S10 to S40.

[0024] Step S10: Obtain the electrode material of the emitter at multiple different emitter temperatures T. E The current-voltage characteristic curve is shown below.

[0025] Step S20: Determine the inflection point current density j at the inflection point of each current-voltage characteristic curve based on the curves. b .

[0026] Step S30: Determine the emitter temperature T based on the current density at each inflection point and multiple current-voltage characteristic curves. E The effective electron transport coefficient of the corresponding emitter surface

[0027] Step S40, based on multiple different emitter temperatures T E and the corresponding effective electron transport coefficient Determine the emitter at multiple different emitter temperatures T E Work function under

[0028] Using the measurement method described in this invention, only the current-voltage characteristic curve of the emitter electrode material of the thermionic converter needs to be obtained. Combined with the theoretical basis of the thermionic converter, the work function of the emitter can be determined based on the obtained current-voltage characteristic curve. Furthermore, accurate current-voltage characteristic data can be easily obtained under conditions close to the actual service environment of the thermionic converter emitter material, allowing for the determination of the work function of the emitter under real service conditions. In addition, this embodiment can determine the work function of the emitter at different emitter temperatures, resulting in more comprehensive work function data.

[0029] In some embodiments, in step S10, a current-voltage characteristic power generation experiment can be performed on the thermionic energy converter at different emitter temperatures T. E Tests were conducted to obtain the emitter electrode material at different emitter temperatures T. E The volt-ampere characteristic power generation data is obtained; and based on the volt-ampere characteristic power generation data, the electrode material of the emitter is plotted at different emitter temperatures T. E The current-voltage characteristic curve is shown below.

[0030] In this embodiment, a conventional flat-plate thermionic energy conversion experimental platform can be used to test the receiver and emitter to obtain current-voltage characteristic power generation data, eliminating the need to build a complex testing platform. Furthermore, testing can be conducted under the operating conditions of the emitter, allowing for in-depth analysis of experimental data on the power generation of the emitter electrode material. This data can be combined with theoretical calculations to conveniently, efficiently, and more accurately determine the work function of the emitter under high-temperature, cesium-adsorbed operating conditions.

[0031] In some embodiments, during the current-voltage characteristic power generation experiment, the work function of the emitter can be calculated online in real time based on the current-voltage characteristic power generation data obtained in the experiment. The method is simple and convenient to use.

[0032] In some embodiments, in the current-voltage characteristic power generation experiment, the receiving electrode temperature T of the thermionic energy converter is controlled. C The electrode gap d between the receiver and emitter, and the plasma vapor pressure P Cs Keep it constant, only change the emitter temperature T E To test and obtain different emitter temperatures T E The current-voltage characteristic power generation data is shown below. For example, the emitter temperature T... E The range of temperature variation can be from 1450K to 1830K, thus making the emitter temperature close to the actual service environment.

[0033] In some embodiments, a tungsten electrode can be used as the emitter and a molybdenum electrode as the receiver. During the current-voltage characteristic power generation experiment, the emitter and receiver are installed in a heating chamber. After the heating chamber is evacuated and preheated, the two electrodes are gradually heated until they reach the required experimental temperature. Then, cesium vapor is introduced into the heating chamber, and after a period of equilibration, the power generation test is performed.

[0034] During power generation testing, the current magnitude is controlled and voltage data is measured. For example, an electronic load can be used to control the current magnitude to obtain the volt-ampere characteristic power generation data. The volt-ampere characteristic curve can then be plotted based on the volt-ampere characteristic power generation data.

[0035] Furthermore, after obtaining the current-voltage characteristic curve at a certain emitter temperature, the receiver temperature is kept constant, and the emitter temperature is increased along the gradient to obtain current-voltage characteristic curves at different emitter temperatures.

[0036] In the current-voltage characteristic power generation experiment, the power generation conditions affect the work function of the emitter; different emitter temperatures result in different work functions. In this embodiment, the current-voltage characteristic power generation experiment is conducted at different emitter temperatures. The work function of the emitter at each temperature can be determined based on the obtained current-voltage characteristic curves, resulting in more comprehensive data.

[0037] Figure 3 The figure shows the current-voltage characteristics of a W-Mo electrode pair at different emitter temperatures according to an embodiment of the present invention, wherein the electrode gap d of the W-Mo electrode pair is 0.4 mm, and the vapor pressure P of the plasma is... Cs The value is 2 Torr, and the receiving electrode temperature is 850 K.

[0038] In some embodiments, in step S20, the inflection point current density j at the inflection point of each current-voltage characteristic curve is determined.b At this time, the current density j at the inflection point can be read from the current-voltage characteristic curve. b .

[0039] For example, such as Figure 3 As shown, the emitter temperature T E The current density at the inflection point A1 of the current-voltage characteristic curve at 1830K is T. E The inflection point current density at 1830K; emitter temperature T E The current density at the inflection point A2 of the current-voltage characteristic curve at 1810K is T. E The inflection point current density at 1810 K; emitter temperature T E The current density at the inflection point A3 of the current-voltage characteristic curve at 1790K is T. E This is the inflection point current density at 1790K.

[0040] The current-voltage characteristic curve is a dynamic power generation result; the work function of the emitter differs at different current densities. In some embodiments, the actual current density of interest can be selected as the target current density within the current density range of the current-voltage characteristic curve to determine the work function of the emitter at the target current density.

[0041] In some embodiments, the target current density can be selected according to actual needs. For example, such as Figure 3 As shown, the actual current density j1 can be selected as the target current density. In some embodiments, different target current densities can be selected to determine the work function of the emitter under multiple different target current densities, thereby obtaining more comprehensive work function data.

[0042] In some embodiments, step S30 includes: step S31, determining the output voltage corresponding to the target current density in the current-voltage characteristic curve based on the current-voltage characteristic curves at multiple different emitter temperatures. Step S32, for each emitter temperature T E According to the emitter temperature T E The corresponding inflection point current density j b The output voltage corresponding to the target current density Determine the effective electron transport coefficient In this embodiment, key data, such as the inflection point current density, are extracted from the current-voltage characteristic curve. These values ​​allow for theoretical reasoning and calculations based on key data to determine the work function of the emitter at various emitter temperatures and target current densities under near-real service conditions.

[0043] In some embodiments, the output voltage corresponding to the target current density in the current-voltage characteristic curve is determined. At this time, the output voltage corresponding to the target current density at each emitter temperature can be obtained from the current-voltage characteristic curve, and the target current density can be determined based on the emitter temperature and the corresponding output voltage. Furthermore, since the data points in the current-voltage characteristic curve are discrete, this embodiment can perform interpolation processing on the current-voltage characteristic power generation data to obtain the corresponding output voltage under the same current density.

[0044] In some embodiments, multiple different emitter temperatures can be determined. The average value is used as the target current density. To improve the acquisition Data accuracy. For example, it can be based on the emitter temperature T. E1 and the closest emitter temperature T E2 The corresponding output voltages U1 and U2 are used to calculate the temperature of each emitter. Then calculate its average value. Optionally, it can be based on the emitter temperature T. E Plot the output voltage versus emitter temperature curve under the target current density, i.e., UT, and the corresponding output voltage U. E The curve is then fitted to obtain UT. E The slope of the curve is the value at the target current density.

[0045] like Figure 4 As shown, in some embodiments, in step S32, based on the emitter temperature T E The corresponding inflection point current density j b The output voltage corresponding to the target current density Determine the effective electron transport coefficient This may include the following steps S321 to S324.

[0046] Step S321, set the electron transport coefficient D respectively E And the range of values ​​for the electron reflection coefficient r1 at the plasma boundary.

[0047] Step S322, based on the inflection point current density j b Given the target current density, determine the electron transport coefficient D within the specified range. E The effective electron transport coefficient at the emitter surface corresponding to the electron reflection coefficient r1

[0048] Step S323, based on the target current density and electron transport coefficient D E And the electron reflection coefficient r1 and the corresponding effective electron transport coefficient Determine the electron transport coefficients D E The electron reflection coefficient r1 corresponds to

[0049] Step S324, Compare and various Choice and closest Corresponding effective electron transport coefficient

[0050] In this embodiment, in order to determine the effective electron transport coefficient Theoretical analysis was conducted on the emitter of the thermionic energy converter to determine the corresponding electron transport coefficients and electron reflection coefficients. Based on the current-voltage characteristic curve, With numerical computation By comparing and selecting, the effective electron transport coefficient of the emitter surface under the operating conditions of the current-voltage characteristic power generation process is determined. The results are reliable.

[0051] In some embodiments, the effective electron transport coefficient at the emitter surface can be determined based on the energy balance equation of the thermionic energy converter. and the work function of the emitter

[0052] The effective electrical power of the thermionic energy converter is equal to the energy Q of the electrons emitted from the emitter. E And the energy Q carried by the receiving electron. C The difference, i.e., P = Q E -Q C Electrons escaping from the emitter carry away heat; the heat carried away by electrons from the emitter at a unit current density is defined as the electron cooling rate q. E (Dimensionless, V); Correspondingly, electrons bring heat when they reach the receiving electrode. The heat brought in by electrons when they reach the receiving electrode at a unit current density is defined as the electron heating amount q. C (Dimensional: V). The energy balance equations for the thermionic energy converter are shown in expressions (1) to (3) below.

[0053]

[0054]

[0055] U = q E -q C (3)

[0056] in, The effective work function of the emitter; is the effective work function of the receiving electrode; k is the Boltzmann constant; e is the electron constant. For example... Figure 5 As shown, T E T is the emitter temperature. C T represents the receiving electrode temperature. eE T represents the electron temperature at the plasma boundary near the emitter, i.e., the near-emitter plasma boundary temperature; eC J is defined as the electron temperature at the plasma boundary near the receiving electrode, i.e., the near-receiving electrode plasma boundary temperature. E =j E / j、J C =j C / j、J iE =j iE / j、J iC =j iC / j, J E J C J iE and J iC All are dimensionless currents; j E It is the emission current at the emitter surface, j C It is the emission current on the surface of the receiving electrode, j iE j iC These are the absolute ion currents on the emitter and receiver surfaces, respectively, and j is the actual current density, which in this embodiment can be the current density measured in the current-voltage characteristic power generation experiment. These are the potentials at the emitter and receiver surfaces, respectively, and their relationship to the plasma ionization, average plasma potential, and T. eE T eC It is related to the size.

[0057] Based on the energy flow calorimetry experiment and theoretical analysis of the emission behavior of the electron electrode surface in the thermionic energy converter, it can be known that q C Independent of emitter temperature T E The changes in the emitter material and its surface electron emission behavior. Therefore, in this embodiment, the energy balance equation can be combined with the current-voltage characteristic curve data to determine the work function that reflects the actual power generation performance of the emitter material under real service conditions.

[0058] In step S322, in order to determine the effective electron transport coefficient The emitter is theoretically analyzed. For example... Figure 5 As shown, electron 40 is emitted from the emitter surface, jumps over the emitter surface potential barrier, and reaches the plasma boundary, where it undergoes collisional scattering. After a series of elastic collisions and scattering, some of the electrons 40 enter the plasma, while others are reflected at the plasma boundary. The electron flux density j entering the plasma is...e The following expression (4) can be used to represent it:

[0059]

[0060] Where j0 is the emission current density at the emitter surface; D E is the electron transport coefficient, which does not consider the potential barrier at the emitter surface or the collisional scattering process of electrons at the plasma boundary; r1 is the kinetic reflection coefficient at the plasma boundary; This is the potential barrier at the emitter surface.

[0061] In some embodiments, the effective transparency coefficient at the inflection point is Current density j at the inflection point b On both sides, the direction of the potential barrier sheath on the emitter surface changes. At the inflection point, all the electron flow enters the plasma, and the reverse electron flow j at the plasma boundary... pl =0, the actual current density is equal to the electron flow density entering the plasma, that is, j′ e =j e =j b Therefore, at the inflection point, j′ e / j b =j e / (j b -j pl )=j e / j e，b Among them, j′ e The target current density is the actual current density obtained from the volt-ampere characteristic curve; j e，b j at the inflection point e .

[0062] Based on expression (4) and Richardson's emission equation (5), the inflection point j can be determined. e，b The expression and j at non-inflection points e The ratio is shown in the following expression (6).

[0063]

[0064]

[0065] Where A0 is Richardson's constant; It is the effective transport coefficient of electrons on the emitter surface, which takes into account the potential barrier on the emitter surface and the collision scattering process of electrons at the plasma boundary, and can truly reflect the electron emission performance of the emitter electrode material. This is the effective work function of the emitter.

[0066] In some embodiments, It can be determined based on the following expression (7).

[0067]

[0068] By combining expression (7) with expression (6), the potential barrier at the unknown emitter surface can be eliminated. The following expression (8) is obtained, which can be used to determine the target current density, inflection point current density, and electron transport coefficient D. E The effective electron transport coefficient is determined by the electron reflection coefficient r1.

[0069]

[0070] In step S322, the electron transport coefficient D within the range of values ​​can be determined based on expression (8). E The effective electron transport coefficient at the emitter surface corresponding to the electron reflection coefficient r1 According to expression (8), Only by r1, D E and target current density j′ e and the inflection point current j b Decide.

[0071] In some embodiments, in step S323, in order to determine Theoretical calculations can be performed using the energy balance equation of the thermionic energy converter. When the current density exceeds the inflection point, the electron cooling rate q... C With the temperature T of the emitter E Regardless, according to expressions (1) to (3), it can be determined that only the emitter temperature T is changed. E The differential of the output voltage U is:

[0072]

[0073] Among them, J e The dimensionless current represents the electron flux density j entering the plasma. e With the target current density j′ e The ratio, i.e., J e =j e / j′ e .

[0074] In expression (9), It is approximately 0. And the logarithmic term... The value, relative to The value of is relatively small and can be approximated as negligible. Based on expression (7), the value in expression (9) can be determined. The following expression (10) is obtained.

[0075]

[0076] Based on expressions (9), (10), and (8), the output voltage U and emitter temperature T of the current-voltage characteristic curve can be determined. E The differential relation satisfies the following expression (11).

[0077]

[0078] In some embodiments, in step S323, each electron transport coefficient D can be determined based on expression (11). E The electron reflection coefficient r1 corresponds to

[0079] In expression (11), It is the emitter temperature T E The vacuum work function of the lower emitter, typically for metallic materials, satisfies the following linear relationship with temperature: in, Let be the vacuum work function at 0 K, and α be a constant that depends only on the material. Therefore, we can obtain the following expressions (12) and (13), where the emitter material... The values ​​for α and α can be found in the literature.

[0080]

[0081]

[0082] In some embodiments, the ratio J in expression (11) can be determined based on the electrode gap and vapor pressure. e Specifically, the ratio J can be determined based on the following expression (14). e .

[0083]

[0084] Among them, P Cs d is the vapor pressure of the plasma during the current-voltage characteristic power generation process, and d is the electrode gap between the emitter and receiver during the current-voltage characteristic power generation process.

[0085] In this embodiment, based on the energy balance equation and combined with the current-voltage characteristic curve data of the thermionic energy converter, the effective electron transport coefficient can be determined. This enables real-time, online calculation of the effective work function of the emitter material under service conditions. This embodiment delves into experimental data on the volt-ampere power generation of the emitter electrode material, combining it with numerical calculation results to conveniently and efficiently solve for the effective electron transport coefficient of the emitter surface. This allows for the efficient solution of the emitter's work function.

[0086] In some embodiments, in step S321, the electron transport coefficient D can be set. E The range of values ​​for the electron reflection coefficient r1 can be set, for example, to 0 to 0.8, and the range of values ​​for the electron transport coefficient D... E The value range is 0 to 1, thus determining D can be dynamically set within the above value range. E The value of r1 is used to select the current-voltage characteristic of the power generation process. closest The corresponding D E Compared with r1, improve the certainty of D E The accuracy of r1.

[0087] In some embodiments, the effective electron transport coefficient is determined. At that time, you can first keep D E Keeping it constant, gradually changing r1, and determining D based on expression (8). E Different r1 corresponding Then, based on expression (11), determine the D. E Different r1 corresponding For example, when D E When the value is 0.55, setting r1 from 0 to 0.8 yields the following result: With current density j′ e A scatter plot of changes, such as Figure 6 As shown. Then, change D. E Repeat the above process to determine different D E Different r1 corresponding

[0088] In step S31, the specific emitter temperature, plasma vapor pressure, and target current density can be obtained based on the current-voltage characteristic curve. In step S324, With each different D E r1 corresponds to Compare and choose closest Corresponding effective electron transport coefficient This is the final effective electron transport coefficient.

[0089] Furthermore, in some embodiments, the effective electron transport coefficient at the emitter surface can be established. The calculation model is used to implement step S32. The experimental data obtained in steps S10, S20, and S31, as well as the operating conditions of the current-voltage characteristic power generation process in step S10 (e.g., emitter temperature, electrode gap, plasma vapor pressure), are input into the calculation model to calculate the effective electron transport coefficient. It is easy to use and saves costs and manpower.

[0090] In some embodiments, step S40 includes: for each emitter temperature T E According to the emitter temperature T E Target current density and selected effective electron transport coefficient Determine the emitter temperature T at the target current density. E Work function under Specifically, after determining the effective electron transport coefficient on the emitter surface under the operating conditions of the current-voltage characteristic power generation process, the work function of the emitter can be determined based on the following expression (15).

[0091]

[0092] The measurement method described in this invention combines the theoretical basis of the thermionic energy converter under arc conditions with the functional characteristics of the flat plate electrode thermionic experimental device. It can calculate the work function of the emitter material of the thermionic energy converter in real time online. It is convenient to use and can obtain the work function under different emitter temperatures and different target current densities. The data obtained is comprehensive and can reflect the work function under real service conditions, avoiding the problem that there is a large difference between the test process and the real harsh service environment of the emitter.

[0093] Regarding the embodiments of the present invention, it should also be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments.

[0094] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for measuring the emitter work function of a thermionic energy converter, characterized in that, The thermionic energy converter includes an emitter, a receiver, and plasma. The plasma is disposed between the emitter and the receiver, and electrons emitted by the emitter reach the receiver via the plasma. The method includes: The electrode material of the emitter was obtained at multiple different emitter temperatures. The current-voltage characteristic curve is shown below. Based on the current-voltage characteristic curves, determine the inflection point current density at the inflection point of each current-voltage characteristic curve. ; The emitter temperature is determined based on the inflection point current density and the multiple current-voltage characteristic curves. The corresponding effective electron transport coefficient of the emitter surface ; Based on multiple different emitter temperatures and the corresponding effective electron transport coefficient Determine the emitter at multiple different emitter temperatures. Work function under ; The emitter temperature is determined based on the inflection point current density and the multiple current-voltage characteristic curves. The corresponding effective electron transport coefficient of the emitter surface ,include: Based on the current-voltage characteristic curves at multiple different emitter temperatures, determine the output voltage corresponding to the target current density in the current-voltage characteristic curves. ; For each of the aforementioned emitter temperatures According to the emitter temperature The corresponding inflection point current density The output voltage corresponding to the target current density Determine the effective electron transport coefficient ; According to the emitter temperature The corresponding inflection point current density The output voltage corresponding to the target current density Determine the effective electron transport coefficient ,include: Set the electronic transport coefficient separately and the electron reflection coefficient at the plasma boundary The range of values ​​for; According to the inflection point current density Based on the target current density, determine the electron transport coefficient within the specified range. and electron reflectance The corresponding effective electron transport coefficient on the emitter surface ; Based on the target current density and the electron transport coefficient and electron reflectance and the corresponding effective electron transport coefficient Determine the electron transport coefficients of each of the above. and electron reflectance corresponding ; Comparison and various Select with the above closest Corresponding effective electron transport coefficient .

2. The method according to claim 1, characterized in that, The electron transport coefficients within the specified range are determined based on the following expression. and electron reflectance The corresponding effective electron transport coefficient on the emitter surface : ； in, The target current density is given.

3. The method according to claim 1, characterized in that, The electron transport coefficients are determined based on the following expressions. and electron reflectance corresponding : ； in, The ratio of the electron flux density entering the plasma to the target current density; The target current density, Richardson's constant, It is the electron constant. Boltzmann's constant, Emitter temperature Vacuum work function of the lower emitter.

4. The method according to claim 1, characterized in that, The above is based on multiple different emitter temperatures and the corresponding effective electron transport coefficient Determine the emitter at multiple different emitter temperatures. Work function under ,include: For each of the aforementioned emitter temperatures According to the emitter temperature The target current density and the selected effective electron transport coefficient Determine the emitter temperature at the target current density. Work function under .

5. The method according to claim 4, characterized in that, The work function is determined based on the following expression. : ； in, The target current density, Richardson's constant, It is the electron constant. is the Boltzmann constant.

6. The method according to claim 3, characterized in that, A current-voltage characteristic power generation experiment was conducted on the aforementioned thermionic energy converter at multiple different emitter temperatures. Tests were conducted to obtain the electrode material of the emitter at different emitter temperatures. Current-voltage characteristic power generation data under the following conditions; Based on the current-voltage characteristic power generation data, plot the electrode material of the emitter at different emitter temperatures. The current-voltage characteristic curve is shown below.

7. The method according to claim 6, characterized in that, In the current-voltage characteristic power generation experiment, the temperature of the receiving electrode, the electrode gap between the receiving electrode and the transmitting electrode, and the vapor pressure of the plasma are kept constant.

8. The method according to claim 7, characterized in that, The ratio is determined based on the electrode gap and the vapor pressure. .

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