Kinetics of ignition of saturated hydrocarbons by nonequilibrium plasma : C<SUB>2</SUB>H<SUB>6</SUB>- to C<SUB>5</SUB>H<SUB>12</SUB>-containing mixtures

International audienceThe kinetics of ignition in CnH2n 2:O2:Ar mixtures for n = 2 to 5 has been studied experimentally and numerically after a high-voltage nanosecond discharge. The ignition delay time behind a reflected shock wave was measured with and without the discharge. It was shown that the initiation of the discharge with a specific deposited energy of 1030 mJ/cm3 leads to an order of magnitude decrease in the ignition delay time. Discharge processes and following chain chemical reactions with energy release were simulated. The generation of atoms, radicals and excited and charged particles was numerically simulated using the measured time-resolved discharge current and electric field in the discharge phase. The calculated densities of the active particles were used as input data to simulate plasma-assisted ignition. The sensitivity of the results to variation in electron cross sections, reaction rates and radical composition was investigated. Good agreement was obtained between the calculated ignition delay times and the experimental data. The analysis of the simulation results showed that the effect of nonequilibrium plasma on the ignition delay is associated with faster development of chain reactions, due to atoms and radicals produced by the electron impact dissociation of molecules in the discharge phase. Finally, we studied the role of various hydrocarbon radicals in the plasma-assisted ignition of the mixtures under consideration

Numerical simulation of plasma-assisted ignition in CH4:air mixtures

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Mechanism of ignition by non-equilibrium plasma

International audienceThe kinetics of ignition in stoichiometric CnH2n 2:O2:Ar mixtures with 90% dilution for n = 15 has been studied experimentally and numerically under the action of a high-voltage nanosecond discharge. It was shown that the initiation of the discharge by a high-voltage pulse 115 kV in amplitude with a specific deposited energy of 1030 mJ/cm3 leads to more than an order of magnitude decrease in the ignition delay time. The generation of atoms, radicals and excited and charged particles by the discharge was numerically described. The role of different atoms and radicals (O, H and CnH2n 1) was analyzed. The temporal evolution of the densities of intermediate components in the plasma assisted ignition was discussed

Ignition with Low-Temperature Plasma : Kinetic Mechanism and Experimental Verification

International audienceThe results of experiments and calculations performed at the Laboratory of Physics of Nonequilibrium Systems, Moscow Institute of Physics and Technology from 1996 to 2008 to demonstrate the efficiency of low-temperature plasma in initiation of combustion of gas mixtures over a wide range of initial conditions are surveyed. In the studies reviewed, a method for quantitative analysis of kinetic processes during ignition of combustible gas mixtures by nonequilibrium plasma was developed

Simulation of the ignition of a methane-air mixture by a high-voltage nanosecond discharge

International audienceThe ignition dynamics of a CH4: O2: N2: Ar = 1: 4: 15: 80 mixture by a high-voltage nanosecond discharge is simulated numerically with allowance for experimental data on the dynamics of the discharge current and discharge electric field. The calculated induction time agrees well with experimental data. It is shown that active particles produced in the discharge at a relatively low deposited energy can reduce the induction time by two orders of magnitude. Comparison of simulation results for mixtures with and without nitrogen shows that addition of nitrogen to the mixture leads to a decrease in the average electron energy in the discharge and gives rise to new mechanisms for accumulation of oxygen atoms due to the excitation of nitrogen electronic states and their subsequent quenching in collisions with oxygen molecules. Acceleration of the discharge-initiated ignition is caused by a faster initiation of chain reactions due to the production of active particles, first of all oxygen atoms, in the discharge

Определение дефицита андрогенов при бесплодии и сниженном овариальном резерве по данным ВЭЖХ-МС/МС и ИХЛА

The androgen deficiency and associated states represent is an important problem that affects the quality of women live. The most widely the androgen influence has been studied in the reproductive period in relation to polycystic ovary syndrome; however about laboratory methods to determine the impact of androgen deficiency and its clinical manifestation in the case of young women with a reduced ovarian reserve and with infertility are still actively discussed. Clinical medicine still needs generally approved markers of androgen deficiency states and its lower reference values. In this work we illustrate the perspective of measurements of steroid hormones panel to verify the diagnosis on the basis of high performance liquid chromatography with tandem mass spectrometry and immunochemical methods.Дефицит андрогенов и ассоциированные состояния являются важной проблемой, влияющей на качество жизни женщин. Наиболее широко влияние андрогенов исследовано в репродуктивном периоде применительно к синдрому поликистоза яичников, но в случае сниженного овариального резерва у молодых женщин с бесплодием остается открытой дискуссия о лабораторных методах определения влияния дефицита андрогенов и его клинической манифестации. В настоящее время в клинической медицине нет однозначного мнения по поводу перечня маркеров данного состояния и нижних референсных значений. В данной работе показана перспективность использования панели стероидных гормонов для оценки уровня андрогенов у женщин репродуктивного возраста, а также проведено сравнение точности постановки диагноза на основе результатов измерений концентрации гормонов методом высокоэффективной жидкостной хроматографии в сочетании с тандемной масс-спектрометрией и иммунохимическим методом

Plasma decay in the afterglow of a high-voltage nanosecond discharge in air

International audienceThe decay of air plasma produced by a high-voltage nanosecond discharge at room temperature and gas pressures in the range of 110 Torr was studied experimentally and theoretically. The time dependence of the electron density was measured with a microwave interferometer. The initial electron density was about 10¹2 cm3. The discharge homogeneity was monitored using optical methods. The dynamics of the charged particle densities in the discharge afterglow was simulated by numerically solving the balance equations for electron and ions and the equation for the electron temperature. It was shown that, under these experimental conditions, plasma electrons are mainly lost due to dissociative and three-body recombination with ions. Agreement between the measured and calculated electron densities was achieved only when the rate constant of the three-body electronion recombination was increased by one order of magnitude and the temperature dependence of this rate constant was modified. This indicates that the mechanism for three- body recombination of molecular ions differs from that of the well-studied mechanism of atomic ion recombination

Plasma decay in air and O<SUB>2</SUB> after a high-voltage nanosecond discharge

International audienceThis paper presents the results of experimental and theoretical studies of an afterglow in room temperature air and O2 excited by a high-voltage nanosecond discharge for pressures between 1 and 10 Torr. We measured time-resolved electron density by a microwave interferometer for initial electron densities in the range (23) × 1012 cm&#8722;3. Discharge uniformity was investigated by optical methods. The balance equations for charged particles and electron temperature were numerically solved to describe the temporal evolution of the densities of electrons and ions in the discharge afterglow. It was shown that the loss of electrons is governed by dissociative and three-body electron recombination with \rm O₂^ ions under the conditions considered. Good agreement between the calculated and measured electron density histories could be obtained only when the rate of three-body recombination was increased by an order of magnitude and when the dependence of the recombination rate on electron temperature was changed. This could testify that the well-understood mechanism of three-body electron recombination with atomic ions could be noticeably modified in the case of molecular ions