During the study of premixed NH3/CH4 fuel mixtures, flame separation into two reaction zones was observed upon flashback into a Bunsen burner. Stable combustion regimes were obtained, with a gap between the burner rim and the upper luminous region, the size of which depended on the mixture composition and the position of the combustion zone inside the burner. The work examines combustion regimes of NH3/CH4 mixtures with an ammonia content of 10–60% in the fuel blend. The equivalence ratio was varied in the range of 0.95–1.1. The Reynolds number was maintained in the range of 270–300, ensuring laminar flow conditions. At the burner exit, temperature and gas composition profiles were measured. Flame emission was recorded at the chemiluminescence bands of OH* (308 nm) and CH* (431 nm), and emission spectra were acquired both inside and outside the burner. Spectra in the range of 190–1080 nm were recorded. Spectral analysis revealed a band corresponding to NO2 emission in the upper part of the luminous region. It is most likely that nitrogen dioxide is formed through low-temperature reactions occurring when the combustion products mix with atmospheric air.

This paper investigates the combustion characteristics of promising decarbonized fuel mixtures—methane/hydrogen (CH4/H2) and ammonia/hydrogen (NH3/H2)—with a focus on how they interact with external electric fields. The key findings are that these flames possess significant electrochemical properties, allowing for non-intrusive control over their stabilization, shape, and structure using relatively weak electric fields. The research combines experimental techniques like volt-ampere characteristic (VAC) measurement and advanced Hilbert visualization to analyze flame deformation, temperature distribution, and species concentration. Two orientations of the electric field were considered: transverse and longitudinal. For the transverse field, an assessment of the degree of flame deformation was made, indicating the preservation of the laminar combustion regime. In the longitudinal electric field, a change in the combustion stabilization mode was observed, which was detected through visualization and current-voltage characteristics (CVC).

The influence of an electric field on the plasma of an optical discharge in subsonic and supersonic air flows has been studied experimentally. The presence of a weak electric field practically does not affect the size of the plasma formation, but, regardless of the configuration of the field lines and the polarity of the applied voltage, it leads to a decrease in the probability of optical breakdown. The experiment has shown that the plasma created by focused laser radiation is very sensitive to the presence of an electric field. When a voltage exceeding 22 kV was applied to the ring electrodes, powerful quasi-stationary streamers were formed in the flow. The presence of an optical discharge plasma made it possible to create an electric discharge in fields with an intensity below the breakdown threshold of the medium. The effect of quenching and the processes of development of an optical discharge were studied depending on the speed and characteristics of the electric field. Quenching of the optical discharge was observed when a voltage of 22 kV and higher was applied. Despite the preservation of the geometric dimensions of the optical discharge, the high-temperature region in the flow can be increased by using electric streamers. This leads to an increase in the energy supplied to the flow, and thus allows combustion to be initiated and flame stabilized at higher flow rates.

В данной работе представлены результаты изучения влияния разбавления метана водородом на физико-химические и электрические характеристики пламени диффузионной струи СН4/Н2. Было обнаружено, что для смесей с молярной долей метана выше 40% величина протекающего тока линейно зависит от состава. Разбавление водородом при молярной доле метана в смеси менее 40% приводит к тому, что зависимость тока от состава становится нелинейной. В этом случае граница перехода от линейной зависимости к нелинейной не зависит от скорости потока и формы электрода. Результаты измерений хемолюминисценции радикала СН* выявили совершенно аналогичную зависимость свечения от объёмной доли водорода. Полученные результаты указывают на существование двух режимов, в которых возможно существенное различие в кинетических механизмах диффузионного горения смеси СН4/Н2.

This paper describes an experimental study of combustion initiation in a supersonic flow of a hydrogen–air mixture under the simultaneous action of focused pulse-periodic CO2 laser radiation and an external electric field. Combustion in a supersonic jet is studied on the basis of data on the intrinsic glow of a flame at the radiation wavelengths of excited OH* radicals. Mixture combustion initiation depends on the shape of electrodes and electrical signals. The flame that occupies the entire cross section of an air–fuel jet is observed only under the conditions of simultaneous action of laser radiation and an electric field. Thus, the combined use of optical and electrical discharges makes it possible to initiate combustion and stabilize the flame of a hydrogen–air mixture in a supersonic flow without mechanical stabilizers.

Results of studying stabilization of a homogeneous hydrogen–air flame on an optical discharge plasma in a high-velocity flow are reported. The main aspect of experiments is providing stable combustion behind the region of laser beam focusing without any mechanical flame holders. The laser radiation parameters are sufficient for creating a quasi-steady plasma in the flow. It is shown that the optical discharge stabilizes the flame front in a wide range of equivalence ratios for flow velocities up to u = 200 m/s. The laser radiation parameters within the range of their variation from one experiment to another exert a minor effect on the turbulent flame velocity. Flame stabilization behind the optical discharge region has some specific features. An important parameter is heat release due to hydrogen combustion. A dimensionless criterion is derived: the turbulent flame velocity is a linear function of this criterion.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation P. K. Tretyakov, A. V. Tupikin, V. M. Abashev; Modeling the effect of wave structures arising during the deformation of the channel wall on the supersonic flow with heat supply. AIP Conference Proceedings 16 February 2023; 2504 (1): 030104. https://doi.org/10.1063/5.0132369 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Experimental data on the effect of an electric field on the plasma of an optical discharge in an air flow have been obtained. Two configurations of an external electric field under the action of an optical discharge on the plasma are considered. To create an electric field, flat (the field along the beam and across the flow) and ring electrodes (the field across the laser beam and along the flow) were used. It was found that there are two modes of combined discharge (optical and electrical). When the field was created symmetrically with respect to the flow axis, an electrical breakdown was observed from the nozzle exit (positively charged electrode) to the focusing point of the laser beam, while no streamers were observed in the optical discharge wake. In another case, an electric discharge is realized between flat electrodes simultaneously with optical breakdown. In a field of constant strength above 3 kV/cm, the presence of an optical discharge plasma promoted electrical breakdown of the medium. In this case, the parameters of the electrical breakdown depended on the shape of the electrodes, the polarity of the applied voltage, and the air flow rate.

Проведено экспериментальное исследование инициирования горения в сверхзвуковом потоке водородно-воздушной смеси при одновременном воздействии сфокусированного импульсно-периодического излучения СО2-лазера и внешнего электрического поля. На основе данных о собственном свечении пламени на длинах волн излучения возбужденных радикалов ОН* исследовано горение в сверхзвуковой струе.

The aim of this work is to adapt the methods of optical Hilbert diagnostics for the visualization and study of inverse diffusion H2/O2 flame. The diagnostic complex is implemented on the basis of the IAB-451 device with modified optical filtering. Visualization of phase perturbations induced by the studied medium in a probing multiwave light field is performed via polychromatic Hilbert and Foucault-Hilbert transformations in combination with registration and RGB-per-pixel processing of the dynamic structure of the images. From solution to the inverse problem of Hilbert optics using a physically justified initial approximation of the problem under consideration, the temperature field of the flame is reconstructed and the value of the H2, H2O, O2 and N2 concentrations may be restored.

Results of studying kerosene combustion in a pseudoshock with varied temperature and velocity in a supersonic ramjet combustor model are presented. Thermodynamic estimates show that either a supersonic or transonic flow can be retained over the combustor duct at parameters corresponding to the Mach number at the engine entrance M0 ≈ 4.5. The possibility of the pseudoshock regime in the constant-section part of the combustor is experimentally studied in the case where the Mach number behind the inlet (at the combustor entrance) is M $$_c$$   $$>$$  1. Conditions of initiation and evolution of this combustion mode under a pulsed-periodic action on the flow are determined.

Results of studying kerosene combustion in constant-section channels for the Mach number at the channel entrance M = 1.7 are reported. The experiments are performed in channels with variations of the duct shape. The existence of flow regimes with wave structures that do not lead to the development of the pseudoshock mode of combustion is demonstrated. Critical conditions that have to be satisfied for initiation and realization of pre-detonation quasi-stationary combustion are determined.

The influence of an electric field on the plasma of an optical discharge in subsonic and supersonic air flows has been studied experimentally. The presence of a weak electric field practically does not affect the size of the plasma formation, but, regardless of the configuration of the field lines and the polarity of the applied voltage, it leads to a decrease in the probability of optical breakdown. The experiment has shown that the plasma created by focused laser radiation is very sensitive to the presence of an electric field. When a voltage exceeding 22 kV was applied to the ring electrodes, powerful quasi-stationary streamers were formed in the flow. The presence of an optical discharge plasma made it possible to create an electric discharge in fields with an intensity below the breakdown threshold of the medium. The effect of quenching and the processes of development of an optical discharge were studied depending on the speed and characteristics of the electric field. Quenching of the optical discharge was observed when a voltage of 22 kV and higher was applied. Despite the preservation of the geometric dimensions of the optical discharge, the high-temperature region in the flow can be increased by using electric streamers. This leads to an increase in the energy supplied to the flow, and thus allows combustion to be initiated and flame stabilized at higher flow rates. Key words: experimental modeling, laser radiation, optical breakdown, electric field, electric discharge, sub- and supersonic air flow.

The work is devoted to the study of stabilization of a diffusion torch by an electric field with a time-varying field line configuration. The stability of combustion was studied using this method of stabilization of the flame, namely the position of the ignition points in the presence and absence of an electric field. The experiments proved that the stabilizing effect of an electric field with a time-varying field line configuration is observed when the torch is stabilized near and above the plane of the electrodes. When the direction of electric forces coincides with the direction of the fuel jet, the effect of the field will strengthen the fluctuation of flame.

Abstract The results of a study on the dynamics of initiation of a pseudo-shock combustion mode in a channel of constant cross section under pulsed action on the flow are presented. Various conditions are considered (kerosene flow rate, change in channel length and working gas in control pulses). Pulsating combustion mode is implemented. It is shown that the reduction of the length of the constant section leads to a decrease in combustion stability. When applying control pulses, two scenarios of the development of disturbances can be implemented: with intensification of combustion and the formation of wave structures, or with attenuation without intensification of combustion. In case of combustion, the motion of the disturbance along the channel can conditionally be divided into two stages: 0 4 ms. The duration of the first stage can be interpreted as a delay in the ignition of kerosene; in the second stage, the perturbation velocity relative to the channel walls is almost constant. The use of kerosene (synthesis gas) conversion products in pulses accelerates the transition from diffusion to pseudo-shock combustion, and the rate of disturbance propagation increases by about 2 times.

An approach to studying the influence of the electric field on the flame with separate consideration of the effects of curving and extending of the plane flame is proposed. The degree of deformation can be used as a factor determining the action efficiency. Based on the results obtained by combined application of particle image velocimetry and spectral zonal registration, the change in the degree of deformation of the flame of a Bunsen-type burner located between flat electrodes is estimated.