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NON-TRADITIONAL DEVICES AND METHODS OF OBTAINING ELECTRIC ENERGY
INVENTION
Patent of the Russian Federation RU2226737

MAGNETOHYDRODYNAMIC METHOD OF CONVERSION OF THERMAL ENERGY TO ELECTRIC CLOSED CYCLE

MAGNETOHYDRODYNAMIC METHOD OF CONVERSION OF THERMAL ENERGY TO ELECTRIC CLOSED CYCLE

The name of the inventor: Slavin VS; Kinnikov Finnikov; Milovidova TA
The name of the patent holder: Krasnoyarsk State Technical University
Address for correspondence: 660074, г.Красноярск, ул. Kirensky, 26, KSTU, Patent and Information Department
The effective date of the patent: 2002.03.29

The invention relates to the production of electrical energy and can be used in electric power plants that convert thermal energy into electrical energy. The method includes accelerating the flow of an inert gas, creating high-energy electrons and high-current electrical discharges of time-periodic conductive layers moving in a gas flow in a transverse magnetic field in the flow before the entrance to the channel of the MHD generator by means of pulsed electron beams. In this case, the self-supporting mode of the electrically conductive layers in the channel of the MHD generator is realized due to the energy of the flow and the generation of the useful power. In electrically conducting plasma layers, a state of "frozen ionization" is created, for which electron beams are used only for initial ionization, and the final ionization is carried out by means of a pulsed high-current discharge with a characteristic discharge time of no more than 2 · 10 -6 s . The high-current discharge uniformly increases the concentration of electrons in the pre-ionized electrically conductive layer, and the discharge voltage is selected so that the electron concentration at the moment of discharge current shutdown is (0.8-1.5) × 10 15 cm -3 . The technical result is the creation of conditions under which the phenomenon of "frozen ionization" will persist in an inhomogeneous gas-plasma flow in a plasma.

DESCRIPTION OF THE INVENTION

The invention relates to the production of electrical energy and can be used in electric power plants that convert thermal energy into electrical energy. Of particular importance is this invention can be found when creating a powerful space power plant, where the closed cycle for the working body installation is of fundamental importance.

[1], a method for converting thermal energy in a closed-cycle MHD generator using as a working fluid an inert gas stream without an alkali metal additive, including accelerating the flow of an inert gas, creating time-periodic layers in the flow before the channel entrance of the MHD generator Electrical conductivity. Movement and self-maintenance of the specified layers in the channel of the MHD generator due to the energy of the flow, the removal of the useful power. This method involves the periodic use of a pulsed electric discharge system with a characteristic pulse time of ~ 10 -4 s , during which the electron concentration in the electrically conductive plasma layer should increase to ~ 10 14 cm -3 .

With this "slow" ionization, the electron gas manages to transfer a significant part of its thermal energy to the atomic gas, as a result of which the gas in the volume of the electrically conductive layer heats up and raises the pressure. The high-pressure region starts a gas-dynamic expansion, at which the density of the gas falls. In regions with a lower density (that is, where an increased concentration of electrons has led to a strong heat release), the electron temperature will be increased, which will further enhance the ionization and release of heat. In fact, the ionization instability will develop, because of which the discharge becomes inhomogeneous, ionization turbulence develops in it, and the effective electrical conductivity decreases sharply.

A method is known [2] for converting thermal energy in a closed-cycle MHD generator , including accelerating the flow of an inert gas, creating time-periodic layers with increased conductivity in the flow before the entrance of the MHD generator, moving and self-maintaining these layers in the MHD generator channel Due to the energy of the flow, the removal of useful power. In this method, for the creation of layers with increased electrical conductivity, it is proposed to use pulsed high energy electron beams to form nonequilibrium ionized plasma clusters in an inert gas stream. The power of the electron beams is determined by the condition

N e > n Saha (T ion ),

Where n e is the electron concentration in electrically conductive bunches;

N Sakh is the equilibrium electron concentration determined from the Saha equation;

T ion is the threshold temperature of electrons with which avalanche-like ionization begins (for example, for neon T ion ~ 18000K) .

If the condition 4000K <T <T , Where T e is the temperature of the electrons in the plasma layers, in inert gases there is a significant decrease in the rate of recombination in triple collisions. The plasma is in a state of "frozen ionization", at which a high electron concentration (n e ~ 10 14 cm -3 ) is retained, which on the one hand provides an effective magnetohydrodynamic process in the channel of the MHD generator, and on the other hand in such a plasma the electrical conductivity depends on the electron Temperature as ~ T -12e , which prevents the development in the plasma of dissipative instabilities, such as ionization and overheating.

The drawback of the method is that achieving an electron density of 10 14 cm -3 only due to ionization by an electron beam is a problematic problem (as a rule, existing devices form electron beams that make it possible to obtain n e ~ 10 10 cm -3 in the gas flow). In addition, ionization by an electron beam leaves the gas cold in the volume of a nonequilibrium plasma bunch, which should lead to the formation of molecular ions in this volume. In turn, molecular ions rapidly recombine in binary collisions with electrons, the concentration of free electrons decreases sharply and the effect of "frozen ionization" disappears.

The invention is based on the task of creating conditions under which the phenomenon of "frozen ionization" will persist in an inhomogeneous gas-plasma flow in a plasma.

The task is achieved by the fact that in a magnetohydrodynamic method of converting thermal energy into an electrical closed cycle involving acceleration of the flow of an inert gas, the creation in the flow in front of the channel of an MHD generator by pulsed electron beams of high energy of time-periodic conducting layers, displacement and self-maintenance of electrically conductive Layers in the channel of the MHD generator due to the energy of the flow, the removal of the useful power according to the present invention, for the creation of electrically conductive plasma layers in a state of "frozen ionization," electron beams are used only for initial ionization, and the final ionization is carried out by means of a pulsed high-current discharge With a characteristic discharge time of no more than 2 × 10 -6 s , which uniformly increase the concentration of electrons in the pre-ionized conductive layer, while the discharge voltage is selected so that the electron concentration at the moment of discharge current shutdown is (0.8-1.5) 10 15 cm -3 .

"Fast" ionization in a high-current discharge with a characteristic action time of no more than 2 • 10 -6 s (the condition is established in the course of a numerical experiment on a mathematical model) dramatically increases the concentration of electrons that do not have time to exchange energy with a neutral gas, Gas temperatures and pressures. In this case, in regions with a high electron concentration, due to the predominance of electron-ion collisions over collisions, the electron-neutral atom reduces the mean free path of an electron and, correspondingly, the electron temperature decreases. Thus, in a "fast" high-current discharge, in contrast to a "slow" discharge, the electron temperature will decrease in regions with increased ionization, which suppresses the ionization instability and makes the discharge uniform throughout the region previously ionized by the electron beam. After the electric field is turned off, recombination in triple collisions, proportional to n 3e , occurs fairly rapidly (with a characteristic time of ~ 10 -4 s ) to a concentration level n e ~ 10 14 cm -3 , after which the recombination rate decreases sharply. The gas flow introduces a plasma bunch into the magnetic field of the MHD generator , where the electron temperature at the level of ~ 10 4 K is established by the induced electric field in the plasma. Realization of the regime with "frozen ionization" in this case was possible due to excessive ionization ( 0.8 · 10 15 cm -3 - 1.5 · 10 15 cm -3 ) of plasma in a high-current discharge. Subsequent recombination up to the level n e ~ 10 14 cm -3 leads to the release of energy expended for ionization in the form of heat, which raises the temperature of heavy particles (neutral atoms and ions) in the plasma to 3500K-4000K . The boundaries of this temperature range were determined during the numerical modeling of the plasma recombination process, for which the ionization level was set from the interval (0.8-1.5) · 10 15 cm -3 . At a temperature of 3500K - 4000K molecular ions are not formed, and the recombination process can be carried out only by a slow three-particle collision mechanism. If, at the end of a pulsed high-current discharge, the electron concentration is less than 0.8 × 10 15 cm -3 , then the temperature of the heavy particles in the plasma will be lower than 3500 K, and molecular ions will form in the plasma. At a concentration above 1.5 × 10 15 cm -3, the temperature will exceed 4000K , which does not prevent the "frozen ionization" regime, but this regime requires unjustified energy expenditure.

In the drawing, an apparatus for implementing the proposed method is shown.

The device comprises a supersonic nozzle 1, an electron beam injection system 2, a pulse high-current discharge system 3, electrodes of an MHD generator channel 4, an electromagnet coil 5, electrically conductive plasma layers 6, an MHD generator channel 7, a load supply system 8, a load 9.

THE METHOD IS PROVIDED AS FOLLOWS:

A heated inert gas (for example, neon), whose temperature can be selected from the range 1500 K <T < 3000 K , is accelerated in a supersonic nozzle 1. Before entering the MHD generator channel, a high energy electron beam is periodically injected through system 2, A local region appears with the initial electron concentration ~ 10 10 cm -3 . Then, by switching on the system 3 of a pulsed high-current discharge, a plasma clot with an electron concentration of ~ 10 15 cm -3 is formed from the initial ionization region. Further, the gas flow introduces into the MHD channel 7 an electrically conductive plasma bunch 6 in which, due to a decrease in the electron concentration to ~ 10 14 cm -3, the temperature of heavy particles increases to 3500K-4000K . Here, the plasma is closed to the electrodes 4. Induced by the motion of the plasma in the transverse magnetic field created by the electromagnet winding 5, the electric current is converted by the load power system 8. The useful power is released in load 9. The same electric current flowing through the plasma is maintained at an electron temperature of ~ 10 4 K and thus, the conditions for maintaining the plasma in the state of "frozen ionization" are fulfilled.

In order to numerically study the process of initiating a plasma bunch in an inert gas flow, a calculation model was created in which, together with the equations of magnetic gas dynamics, the equations of multilevel ionization kinetics were solved, which included the following elementary processes: the collision of excited atoms with electrons, radiation transitions, deactivating collisions with atoms, the formation of molecular Ions, recombination processes in a double collision of a molecular ion and an electron, and a triple collision of an atomic ion and two electrons. The rate constant of the excitation reaction from the ground state was determined as a result of a numerical solution of the Boltzmann kinetic equation, taking into account the nonequilibrium population of the first excited state. The kinetic model was tested by comparing the calculated results with the experimental data on the values ​​of the Townsend coefficients and with experimental data on the properties of the contracted discharge in neon. The fact of a good coincidence of the calculated and experimental results indicates the adequacy of the model to the real process.

Numerical simulation of the generator process realizing the described method showed that in the neon flow with the parameters of braking Г = 2000К, Р = 1 MPa, the process of conversion of thermal energy into electric energy with efficiency indicators can be performed: the enthalpy conversion degree is 39% , the adiabatic efficiency is 78 % .

The installation with such parameters will make it possible to create a MHD power plant including a combined-cycle plant with a total efficiency of about 60% for terrestrial power engineering, and in the case of space applications together with solar radiation concentrators as a thermal source, an on-board closed-cycle power plant with a specific power level of 600 W / Kg , which is approximately twenty times higher than that of the currently used solar cell panels.

INFORMATION SOURCES

1. Slavin VS, Zelinsky NI, Lazareva NN, Persianov PG, "Disk Closed Cycle MHD Generator with Faraday Type Channel Working on Pure Noble Gas" (Disk MHD generator of a closed loop with a Faraday type channel operating on pure inert gas), article In the collection of proceedings of the International Conference "11 th International Confederation on MHD Electrical Power Generation", Vol. 4, pp. 1190-1198., Academy of Sciences of China. - Beijing, 1992.

2. Slavin VS, Danilov VV Magnetohydrodynamic method of conversion of thermal energy into an electrical closed cycle, Patent of the Russian Federation No. 21110131, 1998.

CLAIM

A magnetohydrodynamic method for converting thermal energy into an electrical closed cycle, including accelerating the flow of an inert gas, creating in the flow in front of the input of an MHD generator by pulsed electron beams of high energy periodic in time conductive layers, the movement and self-maintenance of the energy of the electrically conductive layers in the channel of the MHD generator Due to the energy of the flow, the removal of useful power, characterized in that for the creation of electrically conductive plasma layers in the state of "frozen ionization," electron beams are used only for initial ionization, and the final ionization is carried out by means of a pulsed high-current discharge with a characteristic discharge time of not more than 2 · 10 -6 s , which uniformly increase the concentration of electrons in the pre-ionized electrically conductive layer, and the discharge voltage is selected so that the electron density at the moment of discharge current shutdown is (0.8-1.5) · 10 15 cm -3 .

print version
Date of publication 29.11.2006гг