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"Termotron" - thermionic GENERATOR ...
Direct conversion of thermal energy into electricity
Author: Sedunov IP
Passed 15 years since the last time I looked at the results of their work, decided not to open the subject, and do not spend more wasted your own time ... but today, when the whole country turned into a buy-sell "creative place freedom "is a world Wide web of the Internet. But here, everyone is trying to sell prepaid, palming often poor-quality goods. It will not be like them.
Sedunov IP
introduction
I believe that the available form of presentation, for the majority of readers who do not have even minimal training, and help them, and all of us to better understand the prospects of electric power by direct conversion of heat into electricity. Realize that this thermionic generators, what are their advantages and disadvantages, which hide the basic contradictions, preventing thermionic generators to take their rightful leadership position in the energy sector.
Thermionic emission was discovered by Edison in 1884.
Several post in 1897.
Thomson showed that a heated cathode emitted electrons. This effect is known as "electron emission" - electron emission phenomenon outside of the conductor.
In the metal even at low ambient temperature, there are a large number of free electrons in the random thermal motion. Speed free electrons at any fixed point in time and vary vary over time due to the interaction between electrons and a crystal lattice of the metal ions. When the speed of the metal is heated electrons and their kinetic energy increases.
From the chaotic thermal motion of the electrons reaching the metal surface. Not all of them can cross the surface of the metal and go into the environment. On the electrons approaching the surface, begin to operate the electrical power is drawn back into the metal. At the surface of the metal formed two layers of opposite electrical charges, which are determined to overcome the electron energy is spent. To exit the electron outside the metal, they must have a sufficient amount of kinetic energy, and even to overcome the retention force of the metal. Such work is called work function. It is a characteristic quantity, and is different for each metal. As mentioned inhibitory effect, which has a metal on leaving its electron, it does not end at the moment of crossing the boundary of the metal electron. As a result, the output is a positively charged electron. Moving away from the metal, it moves in a retarding electric field.
At room temperature, only a few electrons in a metal have a reserve of energy, sufficient to yield metal. Therefore, almost negligible under these conditions the emission of electrons. Increase the number of electrons leaving the metal posts can be achieved by additional energy electrons or decrease the work function of the metals. In practice, use both of these tools.
Additional energy Q reported electrons by heating the cathode, which causes an increase in electron emission current (Figure 1). If heated cathode (1) to a temperature (TC) equal to 1100 - 2500 ° K, with a metal cathode surface will fly toward the anode the electrons in (Fig.1) having a lower temperature (TA) equal to 700-1100 ° K. If the external TEmG circuit is closed, electrons from the anode, through an external load (R) back to the cathode. The directional movement of electrons will last as long as the temperature difference (delta T) is maintained between the cathode and the anode.
Thus, part of the thermal energy (Q), supplied to the cathode is directly converted into direct electric current. When you open the external circuit TEmG voltage across its terminals is equal to the EMF.
The dependence of the emission current density of the temperature within the operating range of its measurement exactly follows the law
established as a result of investigations Richardson and Dushman. In the formula, Je - current density thermionic emission in amperes per square centimeter (A / cm2); T is the temperature in degrees cathode absolute scale. A and b - constants depending on the cathode material.
The formula shows that the strongest emission current depends on the value of b, which is proportional to the electron from the metal. The larger the value b, and hence the work output, the lower temperature specified in the emission current density. The value of A for the majority of pure metals, which are made from cathodes vary relatively little.
Table 1
It is easy to notice that most thermionic capability has cesium, followed by barium, etc., the lowest - tungsten, cesium, but is volatile, tungsten, on the contrary tolerates heating to 2700 ° K. In incandescent lamps such as tungsten cathode for a long time I had a specific issue of up to 300 mA / cm2. Cost is such a tungsten cathode was very low and amounted to only 5 mA / W. Features left much to be desired, because then there were activated cathodes for lamps, which are usually the basis of tungsten coated with a thin (atomic) layer of thorium, barium, or other metal with a low work function. In this way, we managed to reduce the work function of 1.7 times at the thorium coating, 3.1 - with barium coating, and as a logical conclusion - the appearance of activated cathodes, reducing even more the electron work function. Among them, the most widely used oxide cathodes, covering the same tungsten atomic layer of a mixture of barium and strontium. And although today the lamp, can be said to have disappeared from our field of view, as had once locomotives with railways, the principles produce thermionic current remained intact.
Classification of thermionic converters
Prior to the classification clarify for themselves the basic essence of thermionic energy. And it is quite simple - and is to carry the maximum number of electrons from a hot cathode to cool the anode with minimal loss of heat. And this did not escape, because the heating of the cathode with subsequent separation of electrons from their nuclei accompanied by the emission of photons (and this is heat transfer by radiation). Trying to move the anode from the cathode, we reduce the thermal impact on the anode, pulling him to the cathode, increasing emissions - current, but the anode starts to overheat. And if the electron as a carrier of negative elementary charge is stable and has a lot of rest, the photon can only be in motion, it can not be stopped, or use the field turn, with "collision" with the material he can only experience the "elastic or inelastic collisions." Themselves to the same atom and photons in the core of the shelf not, they are born at the moment of adjustment of atomic structure, in this case, when it is heated. The farther the photon flow from the anode, the easier it is to return to the cathode via an "elastic collision" due to "mechanical" photon reflection mirrors.
That's the point. The gap between the cathode and the anode is not necessary to determine, without electrons from a hot cathode is easy to "jump" to the cold plate. But their proximity leads to heating of the anode and nullifies the benefits of the free electron transition. The problem lies in the fact to separate the "wheat from the chaff - photons right, left electrons." Once the problem is not solved directly, trying to go around .... Hence, a large number of areas in which develops thermionic energy. No single point of view and even on how to name the device for the thermionic current TEmG who calls and who and TEP (thermionic converter).
It remains only to classify them (Table 2):
In the basic version, all or almost all of thermionic generators (TEmG) as has been shown in Figure 1 is made up of two flat (or coaxial) electrodes separated by a small vacuum gap with h = 0.1 ÷ 0.001 mm.
c included in the circuit load resistance.
1. Vacuum with a small inter-electrode distance to 0.01 mm.
Vacuo commonly understood gas, in particular air having such a high degree of vacuum (pressure of about 10-6 - 10-7 pm.sm. mm) at which the motion of electrons occurs practically without collision with the remaining gas molecules in the vacuum case is not heat-conducting medium;
2. The three-electrode, which requires an auxiliary source of high voltage power supply (performing volumetric ionization);
3. The gas-filled (Gs), in which the surface, or the cathode contact ionization.
4. The transducer with volume ionization - where a stable arc discharge is carried out at a low voltage and current, significant in strength.
In tabular form, it will look as follows:
Vacuum TEmG
In it, and in all the thermionic converter and the principle of leaving the free electrons of the metal by giving them the kinetic energy from the heat input so strong that they begin to fly over the surface of the electronic film (Figure 2) in the direction towards the anode, forming a cloud of electrons between the cathode and the anode with a certain space charge have volumetric potential - 
. Volumetric clouds of electrons reaches a height of about 10-5 - 10-6 m.
Having overcome the surface barrier 
and volume potential 
, The electrodes reach the anode, if it is located on the cathode at the same distance - 10-5 -10-6 m.
At large gaps between the cathode and the anode collision between electrons in the electron cloud does not allow electrons to reach the anode. Therefore vacuum TEmG may not work at large distances between the electrodes and the current value of the gaps in the electrode space are difficult constructively.
And that's what they write on this topic (for energy conversion sources) in the publication, edited by AF Bertinova of 1982 in the "Special electric cars." We quote verbatim: "... in order to reduce the impact of the volume of the potential barrier two possible ways: a) reduction of the electrode distance to 6.10 m; b) the creation of external electric or magnetic fields to compensate . Both these methods are difficult to implement and therefore the vacuum TEmG maloperspektiven. The main drawback - the difficulty of manufacturing and preservation at high temperatures (warping and swelling of the surface) small interelectrode distances, but also the lack of materials for cathodes, able to work for a long time at high temperatures. "
By this paragraph, we will definitely return. Since it is difficult to understand what is really meant (conducted carefully patent search came to nothing lead). With an abundance of material on this subject (take lectures V. Korchagin for the 5th year in the MSTU. Bauman *), there is no clarity on this issue.
In the meantime, we will continue. The higher the temperature of the cathode, the higher the emission current but the intense evaporation and cathode of the crystal lattice, reaching up to 0.1 mm.
for 1000 hours at an operating temperature of the cathode about 2800 K. This is significantly higher vacuum TEmG interelectrode distance where the transfer of material from the cathode to the anode eventually closes the interelectrode space and the installation stops working.
Gas-filled TEmG.
The gas-generators, space charge compensation is achieved by the introduction of positive ions in the inter-electrode space, which is generated by surface or volume ionization. For these purposes, generally use cesium.
Figure 3 shows a three-electrode gas-filled volume ionization generator.
made auxiliary discharge to the cathode with an additional third electrode. On it consumes from 10 to 20% of the total power TEmG. Used at low cathode temperatures not exceeding 1500 ° K. Plant efficiency and does not reach up to 10%.
The next type of gas-filled TEmG, received the most widespread, is based on the effect of surface ionization of neutral gas at the cathode. Upon impact of the atoms of the hot metal surface they give up their electrons, becoming positively charged ions. Thus there is a space charge neutralizing electrons are above the cathode surface. Cesium, filling the space between electrodes and having a low ionization potential (φ = 3.89V) neutralizes surround the space charge of electrons. Number of cesium ions is relatively small, and the ionized gas at a pressure of 2.10 is enough that the electric field in the electrode gap becomes equal to zero. The higher the vapor pressure of cesium, the more the emission of electrons from the cathode to the anode. In general, the partially condensed cesium on the electrodes increases the voltage output element.
The density of the "electron gas" between electrons is not uniform, at the cathode there is an excess of electrons, and in the area of the anode is a thin insulating barrier of relatively cold ionized vapor of cesium (Cs).
Their electrons do without too much difficulty. This barrier acts as a thermoelectric material with a high Seebeck coefficient (α), so in this field may be generated a significant fraction of the cell voltage.
Another common class TEmG - with volumetric arc neutralization.
While working in it under certain conditions, long-term low-voltage cold arc can occur between the electrodes. The voltage of the cell manages to take up to 6 volts (all thermionic generators low-voltage). ionisation current increases by about an order of magnitude increase as a consequence and power. With the unit area (S) in 1m2 of such a generator can be removed up to 250 kW of power (P) and to raise the efficiency of the (n) to install up to 17% with TC = 2000 K and 1000 K = TA.
Efficiency
As with any heat engine TEmG have a certain efficiency.
Table 3 shows the values excluding the real efficiency losses. The obtained values substantially lower and is approximately 10 ~ 15%. (Table 4).
Supplied to the cathode of the power of the heat source (Pm) is spent on electronic cooling of the cathode (Rais), common heat radiation (Ri), with the loss of thermal conductivity (PK) and losses in the leads. (PSC), ie .:
Rt = Ri + Re + Pk + Pm.
According to some experts in the existing TEmG best performance can become generators placed directly in a nuclear reactor with uranium containing cesium cathode. At a temperature of about 2000 degrees is expected of them up to 40% efficiency at the power density of the cathode (Rais), reaching up to 1000 kW / m2.
Such installations may be used only in a space flight.
We stopped at the place where today marking all science, and with it the rest of progressive mankind. And then what .... "Termotron"
"Termotron" - but what is it?
Amplitron - we know magnetron - know even klystron know Termotron not know. And no wonder, it will be about the converter, or more precisely about TEmG that was made 15 years ago as an amateur laboratory setup and lived 3 minutes. True, it showed promising results.
But love will again have to step back a little into history.
Consider for the beginning of the microwave oscillator - amplitron (magnetron). It converts DC power to RF power. Amplitron allows to obtain high values of microwave power at high efficiency, reaching up to 85-90%.
Spinning spokes space charge amplitron (magnetron) as shown in Figure 4, induce currents in the microwave circuit and provide gain. The main purpose: magnetron radar, and of course the space - or rather the solar orbital space power (SEU). This is a program that provides coverage of solar energy to Earth. According to the "plan" in a geostationary orbit (35,800 km), a large solar panel battery (SB), which generate direct electric current feeding the powerful microwave generators (klystrons), and they in turn translate the energy of the Earth beam of electromagnetic waves. This integrated and amplitron. On Earth reaktenna a magnetron with equal efficiency receives direct or alternating current and converts it into an industrial current. That's all. We have come close to the physical model Termotron. For convenience of presentation, consider first prototype - a model plane, the same as the once-made laboratory model.
For a current generator in such a thermionic cathode and anode must be positioned parallel to the working surfaces of the one hand an imaginary plane having a, relatively speaking a "common energy level" and place them in a mutually crossed electric and magnetic fields, as shown in Fig.5. When heated, the cathode electron emission from the surface and the movement of electrons to the anode will be carried out in an electromagnetic field. The trajectory of the motion of the electrons will be similar when using a magnetron - a cycloid.
When creating an electric field between the source connected between the collector of the anode and the cathode with a heated cathode to the collector will move with uniform acceleration electrodes, testing by the electric field effect of constantly accelerating force, due to which the kinetic energy of the electrons increases continuously, reaching its maximum at the surface of the collector. If now in this area begin to enter the growing importance of the magnetic field, increasing the magnetic induction, the trajectory of the motion of the electrons begin to change significantly, become bent the more, the greater the magnitude of the magnetic induction. Upon reaching a certain value of the magnetic induction acting centripetal force with respect to the moving electrons, their trajectory was bent so much that they can not fall on the collector and, describing a curve in the space complex, in this case the cycloid will sink to the anode. The latter will be a considerable distance from the cathode, heated by an external heat source.
Depending on the distance between the electrodes can be adjusted for the magnitude of the electromagnetic field reaching all the electrons of the anode body. Consider the interaction of an electron moving with the specified field double. It is understood that the magnetic field of the electron energy is not exchanged, it only bends its trajectory. Therefore, the kinetic energy of the electron is entirely determined by the difference of potentials, which flew electron in an electric field. Leaving the cathode, the electron is accelerated by the electric field, their kinetic energy increases, while moving along an ascending cycloid branches. On top of the electron curve crosses electric lines of force at right angles, having a maximum kinetic energy. Get more energy from the electric field does not allow a magnetic field that bends its trajectory, causing the reverse motion of the electron at the same energy level, with which he started his movement. If the distance is longer cathode electron flying length, its "landing" occurs at the anode at a speed equal to or close to a "thermal velocity". So, how much energy an electron selected from the electric field when moving up the cycloid, the same number and returned to this field, falling on the descending branch of the cycloid. And in some cases even more, as is shown in Figure 6, the anode is disposed below the cathode by an amount not exceeding the difference between the work function of the cathode and anode. In this case
electric power can not withdraw from the anode, and a source of creating an electric field between the cathode and the anode. What is very important.
In both cases, the electron, which has all the kinetic energy is given to the field, will not cause significant heating of any collector or anode. To significantly improve the efficiency of the installation surface of the anode and the collector must possess high light reflecting properties to return "scattered cathode heat" back to work. These requirements satisfy anodes polished with a surface roughness not lower than 12-14 class microroughness height they should be at half-wave length of the photon, coated with silver, chromium or the same cesium. Then their reflectivity may reach 99.5%. This does not even need to doubt. Thus, it is possible to obtain thermionic generator with outstanding performance and highest efficiency. Further, any short circuiting between the electrodes is eliminated here lattice atoms will act negative electrical field strength.
By varying intensity of the electromagnetic field can be changed from the cathode emission current per unit area, similar to that used in vacuum tubes filament 3/2 law where voltage increases and between electrons and the emission current increases. At the time of the full issue occurs field emission mode, for which will have the following equation of thermodynamics:
Figure 7 shows a coaxial type Termotron. In the circular embodiment possible to use several anodes in this scheme can be clearly seen "paired anodes". The trajectories of electron motion is exactly as in the flat model - cycloid (path A - A '). What is some of the electrons will certainly not be the first time exposed to the anode (trajectory b - b '), but in the case of failure the "flight" of the energy of the electrons is lost. All the electrons return to the "energy level", with which they began their journey. To control the power of the thermionic generator in addition to changing the electromagnetic field characteristics and the load (R), there is the possibility of purely physical effect on the anodes. Way - mechanical adjustment protrusion anodes above the cathode surface within a difference of work function.
Temperature freely anodes can be maintained at 300 ° K.
This will further increase the capacity of the "cold anodes" to capture in his field flies electrons. Accordingly, between the anode and cathode must be provided as thermal insulation, and the proper cooling of the anodes.
Whatever annoy experts describing the benefits discussed thermionic generators focus on that optimistic note, and even as they say, each for himself think out what he wants, the country is waiting for his slaves to perform labor feats, because not soon grow those geeks , which today are looking for in kindergarten!
Literature
1. VF Vlasov "radio course." Gosenergoizdat. 1962.
2. N.I.Karyakin, K.N.Bystrov, P.S.Kireev. "Brief reference book on physics" Gosizdanie "High School. 1962.
3. IP "Radio" Stallions. Publisher "Communication" 1964.
4. GN Alekseev. "Overall the heating engineer". Moscow, "High School" 1980.
5. "Special electric cars." Sources of energy conversion.
Edited by prof. A.I.Bertinova. Moscow. Energoizdat. 1982
6. VD Levenberg "Power plants without fuel." Publisher "Shipbuilding" 1987
7. VI Kozlov. "Electricity and Magnetism" M. Moscow State University Press, 1987.
8. IV Saveliev "Course of general physics" M: Science 1998
print version
Russia Phone / Fax: (812) 379-17-32
Author: Sedunov IP
PS material is protected.
Publication date 23.09.2004gg
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