Experimental study of spark-discharge initiation of detonation

Journal of Electrostatics, 2017

The applied experimental setup enabling measurements of current waveforms and charge transferred during direct ignition tests with brush discharges, was presented in the paper. Tests were conducted with ignition probe designed according to the IEC 60079-32-2 Standard for methane-air gas and propane-air gas mixtures. In the experiment 100 trials were conducted using sample consisted of fluorinated polyethylene. The sample was rubbed with sheep felt cloth. Charge transfer measured rates ranged from 50 nC to 260 nC and the current peak magnitude ranged from 0.5 A to 3.5 A. Magnitude of the current peak as a function of the transferred charge, recorded in the experiment, was presented in the paper. Two regions can be distinguished on the Q ¼ f(dQ/dt) characteristic. There is a region where discharges do not cause ignition and the other one, where the results indicate ignition of gas mixture.

Plasma Physics Reports, 2009

Results are presented from experimental studies and numerical calculations of the ignition of a stoichiometric CH 4 : O 2 gas mixture by a high current gliding discharge. It is shown that this type of discharge generates an axially propagating thermal wave (precursor) that penetrates into the gas medium and leads to fast gas heating. This process is followed by an almost simultaneous ignition of the gas mixture over the entire reactor volume.

IEEE Transactions on Plasma Science, 2000

Results of an experimental study of the efficiency of the ignition of propane-air mixtures by a high voltage repetitively pulsed nanosecond gas discharge (10 kV, 10 ns, 30 kHz) are presented for the pressure range 0.35-2.0 bar. The measured minimal energy for ignition is found to decrease with the pressure. A significant reduction of the ignition delay and a decrease of the overall combustion duration were obtained by using a train of high-voltage pulses. Spectroscopic measurements in a 1-bar air just after a 10-pulse train (300 µs) of about 10 mJ in total energy show the presence of N, N + ,O,andO + atomic species and a gas temperature increase up to 3000 K.

Shock Waves, 2005

Experiments of direct initiation of hydrogen-oxygen by means of a hot turbulent jet were made. Results indicate that the length of ignition tube is the dominant factor in determining the ignition capability of hot turbulent jet, and that the ignition capability of turbulence jet increases with the length of ignition tube. Because this ignition capability can meet the demands of a gas-detonation-driver shock tunnel and it doesn't require additional facilities, the hot turbulent jet initiation method can be applied to large hydrogen-oxygen detonationdriver shock tunnels. Influences of obstacles on the ignition capability were also studied. It was found that the presence of obstacles weakens the ignition capability of a hot turbulent jet.

Journal of Physics: Conference Series, 2019

This paper presents a 0-D kinetic model of electrostatic spark discharges consisting of the time-dependent Boltzmann equation of electrons, a discharge-circuit equation, and heavy particles’ kinetic equations to investigate the energy-transfer mechanisms from the electrostatic energy given to the energy of gases by the spark discharge. In this report, the model is applied to the discharges in atmospheric-pressure air under optimum conditions corresponding for the minimum ignition energies of the typical flammable gases, hydrogen, ethylene and propane, in three types of explosion groups for gases.

Proceedings of the Combustion Institute, 2019

This work aims to provide a better understanding of the cumulative effect of successive nanosecond repetitively pulsed (NRP) discharges on the ignition process. Fast chemiluminescence imaging of both the postdischarge and the following flame was used to analyze the ignition of a lean propane/air mixture (φ = 0.7) by a train of 82 NRP discharges at a pulse repetition frequency (PRF) of 30 kHz, in comparison with the traditional spark ignition. The transition from the non-equilibrium plasma to the ignition kernel has been imaged. It has been found that, differently from traditional spark ignition and despite similar experimental conditions, each NRP ignition develops in a unique way. NRP discharges generate both highly reactive species and thermal instabilities in the gap: the multi-pulse strategy produce a gas motion resulting in a jetting phenomenon, reported here for the first time. An algorithm within ImageJ software was used to quantitatively describe the observed jetting phenomenon. The results presented in this work suggest that jetting is the driver of the ignition initiated by NRP discharges, at least in the experimental conditions investigated here.

Czechoslovak Journal of Physics, 2006

The spark that ignites the combustible mixtures is a glow discharge produced between the electrodes of a spark plug, connected to the secondary of a coil at the high voltage. A good combustion require a frank spark, in a volume as large is as possible and with a maximum of energy. We propose a solution to increase the plasma volume and present electrical discharge parameters as function of inter-electrode distances, pressures in the test-reactor and the electrical pulses width of the power supply.

Proceedings of the Combustion Institute, 2000

A detailed understanding of the processes associated with spark ignition, as a first step during combustion, is of great importance for clean operation of spark ignition engines. In the past 10 years, a growing concern for environmental protection, including low emission of pollutants, has increased the interest in the numerical simulation of ignition phenomena to guarantee successful flame kernel development even for lean mixtures. However, the process of spark ignition in a combustible mixture is not yet fully understood. The use of detailed reaction mechanisms, combined with electrodynamical modeling of the spark, is necessary to optimize spark ignition for lean mixtures. This work presents the simulation of the coupling of flow, chemical reactions, and transport with discharge processes including ionization in order to investigate the development of a stable flame kernel initiated by an electrical spark in methane/air mixtures. A transport model taking into account the interactions of charged particles has been incorporated in the flow model. This model is based on the Chapman-Enskog theory with an extension for polyatomic gases and considers resonant charge transfer and ambipolar diffusion for the computation of the transport coefficients. A two-dimensional code to simulate the early stages of flame development, shortly after the breakdown discharge, has been developed. The modeling includes an equation for the electrical field. The spark plasma channel left behind by the breakdown is incorporated into the initial conditions. Due to the fast expansion of the plasma channel, a complicated flowfield develops after the emission of a shock wave by the expanding channel. The second phase, that is, the development of a propagating flame and the flame kernel expansion, can last up to several milliseconds and is dominated by diffusive processes and chemical reactions.

2020

In a former work, the effect of a volumetric nanosecond discharge at decreasing the detonation cell size was demonstrated experimentally. The experiments were performed under non-optimal conditions for plasma homogeneity. The present work is a paremetric study that aims at optimizing these experimental conditions. An electrode system was installed in a tube to produce a double-pulse discharge with high deposited energy ahead of the detonation front. The amplitude of the high-voltage pulses, the gas mixture and pressure were optimized so that the plasma filled the entire interelectrode space. The analysis of the detonation cell size with and without plasma generation was performed via the sooted-plate technique. Production of atoms and radicals in the discharge triggered combustion chemistry and decreased the ignition delay time. At these optimal conditions, the detonation cell size was thus reduced by a factor of 2, while passing through the region of the discharge.