ХИМИЧЕСКАЯ ФИЗИКА, 2012, том 31, № 2, с. 48-60
ВЛИЯНИЕ ВНЕШНИХ ФАКТОРОВ НА ФИЗИКО-ХИМИЧЕСКИЕ ПРЕВРАЩЕНИЯ
УДК 534.537.551
NON-SELFMAINTAINED GAS DISCHARGE FOR FLAMMABLE GASES IMPACT
© 2012 г. N. V. Ardelyan, V. L. Bychkov*, D. V. Bychkov, S. V. Denisiuk, K. V. Kosmachevskii
Moscow Radiotechnical Institute RAS *E-mail: bychvl@orc.ru, bychvl@gmail.com Received 26.01.2011
Investigations on creation of a non-selfmaintained discharge based on electron beam from the electron accelerator EOL-400M for impact on propane-air mixture have been made. Experiments on detection of some plasma and gas parameters have been realized. Works on modeling of electron-molecule processes in propane-air mixture in external electric field and E-beam at different values of stoichiometricity have been realized.
1. INTRODUCTION
This paper is devoted to investigations on application of non-selfmaintained discharge with a help of the electron accelerator for an irradiation of propane-air mixture. We have created an experimental chamber, controlling devices and the diagnostic complex. All the equipment has been designed, manufactured and assembled. First experiments on inflammation of the flammable mixture in the chamber and injection of the beam into air and flammable mixture have been fulfilled. Temperature of the gaseous mixture and ion currents to electrodes has been measured at combustion of propane-air mixture flow in the chamber and without it. Experiments with the electron beam device based on the industrial electron accelerator EOL-400M have been made. Plasma of non-selfmaintained discharge has been realized in conditions without ignition of propane-air flow and with it. Experiments on inflammation of the flammable mixture in the chamber and injection of the beam into air and flammable mixture have been fulfilled. Experiments have shown sharp increase in the temperature at application of the non-selfmaintained discharge. Gas temperature and ion currents to electrodes in the mixture have been measured at action of the non-selfmaintained discharge under combustion conditions and without them.
At application of simplified chemical model for inflammation of propane-air mixture, our model of air plasmas and addition of detailed water-vapor kinetics we created joint model and the code for determination of plasmas parameters at combined action of the electron beam and the external electric field. In [1, 2] we developed our modeling approach to propane-air mixture with accounting of water vapor concentration that can be increased in the process of combustion. In this paper we consider properties of combustion in condi-
tions of non-stoichiometric mixture propane-air mixture.
1.1. Experimental complex for undertaking of experiments
Experimental works were carried out with a help of a complex created specially for undertaking them. Functioning scheme of the experimental scheme is represented in fig. 1. An industrial electron accelerator of direct action EOL-400M (voltage E = 300-350 kV and current I up to 20 mA) consists of: the accelerating tube with an injector of electrons (1); a high voltage rectifier (2); a high voltage cable (3); a scanning system of the accelerated beam (4); a vacuum window for out-letting of the beam into the atmosphere at undertaking of experimental investigations (5); a vacuum window for outletting of the beam into the atmosphere at accelerator's work (6); an experimental chamber (7), a receiver of the working current of the accelerator (8); diagnostic devices (9); and a system of synchronizing and ensuring of experiments (10).
Since the industrial accelerator E0L-400M does not completely fit requirements of investigations we have undertaken its partial modernization. The modernization mainly was connected with change of the accelerated beam scanning system work. The accelerated beam with a given periodicity was directed to both outlet windows at exploitation of the accelerator in the normal mode, and the scanning system of the beam ensured the beam scan so, that the heat load to the outlet vacuum foils was minimal.
Since in our case one does not require large current value of the electron beam lead into the atmosphere, then, after the modernizing of the scanning system, the continuous beam from the accelerator was constantly
3
directed to one working window (6, see fig. 1), and only for a short time it was moved to the investigation window (5). The modernized scanning system allowed to ensure the maximal possible density of the electron beam in the area of experiments undertaking at necessary time moment through the experimental window.
In fig. 2 one can see a draft of the experimental chamber. The experimental chamber represents a volume with a transversal cross section 30 x 50 mm2 and length of 500 mm. From sides it is limited by two transparent glass plates (1, 2) necessary for visual observation ensuring of processes taking place during the experiments. Upper metallic plates (3, 4) and a foil between them (5) allow the accelerated electrons to get into the experimental volume. During experiments it is possible to apply a high voltage of U = 7—10 kV to these plates.
The lower metallic plate (6) is aimed for collection of the accelerated electrons that pass through the experimental volume. Also on it there is a device of a fuel mixture delivery (7), a device of ignition (8) and a temperature sensor (13).
End faces of the experimental volume are closed by an inlet (11) and outlet (12) flanges at application of the isolation gaskets (9, 10). All the elements of the ex-
perimental chamber are connected very tightly in order to ensure absence of environment influence on experimental results. An air line from a fan is connected to the inlet flange (11) of the experimental chamber; it ensures an air stream for undertaking of investigations. The outlet flange (12) is connected with a device of the combustion products withdrawal from the experimental volume into the ventilation system of the accelerating setup. Parameters of the electron beam are ensured by the accelerator E0L-400M control system. The system of synchronization and experiment support is created on the basis of logic module LOGOl of Company SIEMENS.
1.2. Diagnostic system
Into the diagnostics system enter: the device for measurements of the basic characteristics of the electron flux, sensors of gas flame characteristics measurements and a system of visual supervision over the processes occurring in the experimental chamber in the course of researches. Parameters of the electron beam at the outlet window of the accelerator are measured by means of used industrial accelerator EOL-400M. The set of the targets is applied to carrying out of the elec-
Fig. 2. A draft of the experimental chamber. Upper figure — a side view. Lower figure — a view from above.
tron flux current characteristics measurements in the course of experiments which scheme is represented in fig. 3.
The electron flux from the accelerator, through the foil of the target window F1, gets to the experimental chamber through the foil F2. The part of the beam current, getting to plates Pl, and P2, is measured by means of an oscilloscope by a level of a signal from corresponding resistors. By a signal from the plate Pl an ad-
Fig. 3. A scheme of the electric current characteristic measurements.
justment of an irradiation area of a gas mixture required at carrying out of experiments takes place.
The signal from the plate P2 shows a current value of the beam propagating through the experimental volume. According to the experimental conditions the constant high voltage can be applied to the plate P2. For ensuring of current measurements from this plate a key K1 is foreseen, which, at shut down of a high-voltage source, switches the current-measuring circuit of the given plate.
For measurement of gas characteristics a flame temperature sensors are provided. Sensors are located in various places of the experimental chamber, and by signals from them temperature of a gas flame under various conditions of experiment is determined.
The temperature sensor represents a copper tube with a carving on an external surface. In a tube the thermocouple is located. The place of the thermocouple joint is out of limits of the copper tube for 5—7 mm.
Since experiments on influence of an electron flux on processes of the fuel activation are carried out in the conditions of higher radiation, the direct visual observation is not possible. For carrying out of visual supervision in the conditions of our experiment the system based on use of the IP-camera and the computer is created. The system allows to write down, reproduce and
F1
P1 + F2
process results of the visual supervision of the processes occurring in the experimental chamber.
2. RESULTS OF EXPERIMENTS
At the initial stage of researches measurements of dependence of a gas-air (propane) mixture flame temperature has been carried out at some distance from the ignition place. Adjustment of the created measuring equipment and determination of optimum temporal characteristics ofprocesses was the purpose of the given experiment, along with measurements of a flame temperature.
In fig. 4 a dependence of a flame temperature in the process of the temperature sensor removal from a place of the gas-air mixture ignition is presented. It is seen, that the flame temperature, at the chosen parameters of the experiment, increases in the course of removal of the sensor from the place of the ignition. It can be also seen that the combustion temperature is not equal to T = 1000°C over the whole chamber length.
Analyzing of an obtained waveform shows that the temperature sensor time constant of getting to the stationary mode of measurements does not exceed t = 1 s. Starting from this it is possible to conclude, that the gas mixture delivery duration in the experimental chamber can be no greater than 2 s. This fact has been accounted at the synchroni
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