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As a multiple-start ignition method for liquid-fuel rocket engines, the gas-dynamic igniter has many advantages, such as a simple configuration, low weight and high structural strength. However, because of the complexity of the flow of the working fluid, the details of the thermal processes involved are not clearly understood. In this study, the thermal and flow characteristics of a gas-dynamic igniter are investigated through numerical simulations using the software OpenFOAM. The simulation results show that the pressure within the igniter undergoes oscillations. The axial flow velocity decreases across the pressure wave front so that the kinetic energy of the flow is converted to thermal energy. The temperature increase within the oscillation tube of the igniter is strongly correlated with the entry mass flow. Therefore, the tube inlet area should be designed according to the igniter nozzle flow to achieve the best performance from a gasdynamic igniter. [ABSTRACT FROM AUTHOR]

An electric igniter for engine/hybrid vehicles is presented.The igniter comprises a flyback converter, a voltage-stacked capacitor, a PIC-based controller, a differential voltage detector, and an ignition coil, of which structure is non-contact type. Since the electric igniter adopts a capacitor to accumulate energy for engine ignition instead of traditional contacttype approach, it enhances the igniting performance of a spark plug effectively. As a result, combustion efficiency is promoted, fuel consumption is saved, and exhaust emission is reduced.The igniter not only is good for fuel efficiency but also can reduce HC and CO emission significantly, which therefore is an environmentally friendly product.The control core of the igniter is implemented on a single chip, which lowers discrete component count, reduces system volume, and increases reliability. In addition, the ignition timing can be programmed so that a timing regulator can be removed fromthe proposed system, simplifying its structure. To verify the feasibility and functionality of the igniter, key waveforms are measured and real-car experiments are performed as well. [ABSTRACT FROM AUTHOR]

The essentially nonstationary explosivelike character of erosion–emission processes was revealed by analyzing the plasma action onto a nanostructured W-fuzz surface. It was found that such a fine structure of the surface promotes a local ecton-process ignition by plasma action. The dense W-plasma production time is much less than that of a typical fusion-device first-wall transient-event edge localized mode (ELM) power load. The W-plasma density substantially exceeds that of the incident plasma and leads to intense growth of the electric field and strong emission buildup. Therefore, at the ELM power load, the electric field and emission current density (in the W-plasma–wall sheath) can achieve tens of megavolts per centimeter and 100 \MA/cm^2 or higher due to collective processes driven by an intense emission beam. The strong volume heating by Joule energy release occurs due to the intense emission current density that leads to electric explosion of other W-fuzz nanowire layers. [ABSTRACT FROM PUBLISHER]

On the example of modernizing an SRU catalytic reactor of the elemental sulfur production workshop of the Copper Plant of Norilsk Nikel Mining and Metallurgical Company, the possibility is demonstrated of temperature regime optimization for a Claus industrial reactor. Data are presented for two years of inspection before and after catalytic reactor modernization, indicating that due to a change in the scheme for introducing processing gas there is a reduction by an order of magnitude of the temperature gradient within the catalytic reactor and an almost twofold reduction in its overall gas dynamic resistance. [ABSTRACT FROM AUTHOR]

Electrical thermal chemical guns have so far been investigated in energy regimes where electrical energy has been used to compensate for temperature and add energy to the propellant. This paper presents results where the electrical energy is at levels of, or below, typical chemical igniters for a plasma igniter (PI). The aim of this study is to verify if ignition can be asserted by a PI at these low energies. [ABSTRACT FROM AUTHOR]

Flame transfer function measurements of turbulent premixed flames are made in a model lean-premixed, swirl-stabilized, gas turbine combustor OH*, CH*, and CO2* chemiluminescence emissions are measured to determine heat release oscillation from a whole flame, and the two-microphone technique is used to measure inlet velocity fluctuation. 2D CH* chemiluminescence imaging is used to characterize the flame shape: the flame length (LCH*max) and flame angle (a). Using H2-natural gas composite fuels, XH2 = 0.00-0.60, a very short flame is obtained and hydrogen enrichment of natural gas is found to have a significant impact on the flame structure and flame attachment points. For a pure natural gas flame, the flames exhibit a "V" structure, whereas H2-enriched natural gas flames have an "M" structure. Results show that the gain of M flames is much smaller than that of V flames. Similar to results of analytic and experimental investigations on the flame transfer function of laminar premixed flames, it shows that the dynamics of a turbulent premixed flame is governed by three relevant parameters: the Strouhal number (St = LCH*max/Lconv) the flame length (LCH* max), and the flame angle (a). Two flames with the same flame shape exhibit very similar forced responses, regardless of their inlet flow conditions. This is significant because the forced flame response of a highly turbulent, practical gas turbine combustor can be quantitatively generalized using the nondimensional parameters, which collapse all relevant input conditions into the flame shape and the Strouhal number. [ABSTRACT FROM AUTHOR]

The counterflow ignition of methane was investigated, with particular interest in the role of radical versus thermal runaway. Simulation with different kinetic mechanisms showed that the ignition response is qualitatively sensitive to the kinetic mechanism adopted, either exhibiting or not exhibiting two ignition turning points in the S-curve response. For the former situation, ignition could take place in a staged manner with either increasing temperature or decreasing strain rate of the counterflow, characterized by the first ignition event being radical induced with negligible thermal effect and the second ignition event requiring thermal feedback. Sensitivity analysis and a recently developed chemical explosive mode analysis were performed to identify the dominant reactions in the radical runaway stage, revealing the importance of branching pathways involving the HO2 radical. Counterflow experiments were also conducted, yielding useful information on the ignition response. The study identifies items of further research to sharpen the comprehensiveness and accuracy of the methane oxidation mechanism. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 764–776, 2009 [ABSTRACT FROM AUTHOR]

Abstract: The timing and location of autoignition can be highly sensitive to turbulent fluctuations of composition. Second-order Conditional Moment Closure (CMC) provides transport equations for conditional (co)variances in turbulent reacting flows. CMC equations accounting for compressibility and differential diffusion are analyzed using data from direct numerical simulation of an autoignitive lifted turbulent hydrogen jet flame [C.S. Yoo, R. Sankaran, J.H. Chen, Three-dimensional direct numerical simulation of turbulent lifted hydrogen/air jet flame in a heated coflow. Part 1. J. Fluid. Mech., (2008)]. At the flame base, second-order moments were required to accurately model the conditional reaction rates. However, over 80% of the second-order reaction rate component was obtainable with a small subset (16%) of the species-temperature covariances. The balance of the second-order CMC equation showed that turbulent transport across spatial composition gradients initiates generation of conditional variances. [Copyright &y& Elsevier]

A three-component particle-dynamics anemometer is used to measure, in the near-burner region, the characteristics of gas/particle two-phase flows with a centrally fuel rich swirl coal combustion burner and enhanced ignition–dual register burner, on a gas/particle two-phase test facility. Velocities, RMS velocities, particle mean diameters and particle volume flux profiles were obtained. For the centrally fuel rich burner, particles penetrate the central recirculation zone partially, and are then deflected radially. For the enhanced ignition–dual register burner, particles completely penetrate the central recirculation zone. Compared with the enhanced ignition–dual register burner, in the same cross-section, the particle volume flux peak value for the centrally fuel rich burner is much closer to the chamber axis and much larger near the chamber axis. In six cross-sections from x/d =0.3 to 2.5, the particle volume flux in the central recirculation zone for the centrally fuel rich burner is much larger than that for the enhanced ignition–dual register burner. For the centrally fuel rich burner, most of bigger particles are resident in the region near the chamber axis and the residence time is prolonged. The influence of gas/particle flow characteristics on combustion has been analyzed. [Copyright &y& Elsevier]

The structure of the density profiles in stationary plane shock waves in a vibrationally excited gas is investigated. For self-similar solutions a bifurcation diagram is plotted in the parametric “traveling wave velocity—degree of nonequilibrium” plane. The bifurcation boundaries of the domains of existence of the structures of different types are analytically derived. It is shown that weak plane shock waves are unstable, accelerate, and break down into a sequence of pulses or-at a fairly high pumping rate-waves with nonzero asymptotics, whose amplitude and propagation velocity are independent of the initial disturbance and are determined by the parameters of the medium itself. [ABSTRACT FROM AUTHOR]

The aim of this work was to explore the feasibility of the shaft-free UCG technique in strip mines or coal layers in a shallow depth, and to study the dependability of pushing through the gasification gallery with low-pressure fire seepage. In this article, the conditions of the model test are introduced, and the firepower seepage method is explained. The blind-hole electric ignition technique in the underground gasifier, the push-through technology for gasification gallery with intermittent forward-flow and counter-flow fire seepage combustion, and the underground gasification craft of the small-shaft gasifier are studied. On the basis of the above works, the results of the experiment were analyzed. The characteristics of forward-flow and counter-flow combustion seepage and influence law on coal gas quality are pointed out. Test results showed that the gas heat value heightened in a stepwise way with the rise in the wind-blasting volume, approaching stability. [ABSTRACT FROM AUTHOR]

There is a general consensus that planets form within disks of dust and gas around newly born stars. Details of their formation process, however, are still a matter of ongoing debate. The timescale of planet formation remains unclear, so the detection of planets around young stars with protoplanetary disks is potentially of great interest. Hitherto, no such planet has been found. Here we report the detection of a planet of mass (9.8±3.3)MJupiter around TW Hydrae (TW Hya), a nearby young star with an age of only 8–10 Myr that is surrounded by a well-studied circumstellar disk. It orbits the star with a period of 3.56 days at 0.04 au, inside the inner rim of the disk. This demonstrates that planets can form within 10 Myr, before the disk has been dissipated by stellar winds and radiation. [ABSTRACT FROM AUTHOR]

The recovery of the gas density and the hold-off voltage of a spark gap after breakdown were investigated with Mach–Zehnder interferometry and two-pulse method, respectively. It was shown that the gas density in a 2.7 mm gap filled with atmospheric nitrogen almost fully recovers at t=50 ms but the breakdown voltage of the gap only recovers to its static hold-off voltage, about 21.4% of its original overvolted breakdown voltage. The mechanisms for the delayed recovery of the ability to be overvolted were discussed. [ABSTRACT FROM AUTHOR]

Ignition energy is one of the important parameters of flammable materials, and evaluating ignition energy precisely is essential to the safety of process industry and combustion science and technology. By using electric spark discharge test system, a series of electric spark discharge experiments were conducted with the capacitor-stored energy in the range of 10 J, 100 J, and 1000 J, respectively. The evaluation method for energy consumed by electric spark, wire, and switch during capacitor discharge process has been studied respectively. The resistance of wire, switch, and plasma between electrodes has been evaluated by different methods and an optimized evaluation method has been obtained. The electric energy consumed by wire, electric switch, and electric spark-induced plasma between electrodes were obtained and the energy structure of capacitor-released energy was analyzed. The dynamic process and the characteristic parameters (the maximum power, duration of discharge process) of electric spark discharge process have been analyzed. Experimental results showed that, electric spark-consumed energy only accounts for 8%–14% of the capacitor-released energy. With the increase of capacitor-released energy, the duration of discharge process becomes longer, and the energy of plasma accounts for more in the capacitor-released energy. The power of electric spark varies with time as a damped sinusoids function and the period and the maximum value increase with the capacitor-released energy. [ABSTRACT FROM AUTHOR]

A comparative analysis of the kinetic mechanisms that proceed in CO-O2 and syngas-air mixtures when CO molecule vibrations are excited by laser radiation with a wavelength of 4.7 um and when the laser radiation energy supplied to the gas is spent on heating the mixture is conducted. The efficiencies of both methods of combustion initiation are compared. The simulation shows that the excitation of CO molecule vibrations by laser photons allows significant intensification of the chain processes both in CO-O2(air) and in syngas-air mixtures. This method is much more effective in shortening the induction time and in decreasing the ignition temperature than the method of laser-induced thermal ignition. It was found that in order to ensure the identical delay time it is necessary to add a noticeably higher energy in the case of heating the gas by laser radiation than when exciting the CO molecule vibrations. In addition, a low temperature ignition of the mixture with laser-excited CO molecules makes it possible to raise the efficiency of conversion of the reactant chemical energy to the thermal energy released during combustion compared with the method of heating the mixture by laser radiation. [ABSTRACT FROM AUTHOR]

Microplasma stamps based upon the principle of dielectric barrier discharges are applied to a new type of area-selective surface modification process at atmospheric pressure. This process integrates the surface treatment and lateral microstructuring within one process step. For this purpose the plasma is ignited in cavities which are formed temporarily by compressing the microplasma stamp and the substrate to be treated. In this work we compare different microplasma stamp designs with the objective of minimizing the ignition voltage to the smallest possible value. Several experiments with regard to the ignition voltage have been conducted, operating in air at atmospheric pressure with medium frequency excitation (33 kHz). They contrast the influence of different types of electrical contacts as well as different electrode types and cavity sizes (diameter 100-500 µm) on the ignition voltage. Furthermore the influence of different substrates to be treated and the compression force have been analysed. [ABSTRACT FROM AUTHOR]

A new microwave plasma source concept, particularly for use in the atmospheric pressure region, is presented where impedance matching is realized by a quarter-wavelength waveguide resonator structure. The waveguide is formed by a slot of 100 µm width machined into a copper sheet of 50 mm × 10 mm with a thickness of 200 µm. The slot length for a resonance frequency of 2 GHz is approximately 37.5 mm. This allows generating voltages high enough for ignition of an atmospheric plasma by this very small, simple and easy-to-fabricate structure. After ignition, the plasma extends over approximately 12 mm length of the slot, so a high electrode lifetime can be expected. Furthermore, the planar geometry of this source facilitates up-scaling to array configurations, which allows realization of a distributed source for treating large areas. Basic ignition parameters are investigated. Statistics for multiple ignitions are presented and the resulting Paschen characteristics are shown in the pressure region from 100 Pa to atmospheric pressure. [ABSTRACT FROM AUTHOR]