Journal articles: 'Acoustic igniter'

1

Pearson, Nicholas, and William E. Anderson. "Acoustic Response of a Resonant Igniter with Confuser Inlet." AIAA Journal 46, no. 4 (April 2008): 1013–15. http://dx.doi.org/10.2514/1.22340.

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2

Ahmed, Umair, Fakhre Ali, and Ian Jennions. "Signal Processing of Acoustic Data for Condition Monitoring of an Aircraft Ignition System." Machines 10, no. 9 (September 19, 2022): 822. http://dx.doi.org/10.3390/machines10090822.

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Degradation of the ignition system can result in startup failure in an aircraft’s auxiliary power unit. In this paper, a novel acoustics-based solution that can enable condition monitoring of an APU ignition system was proposed. In order to support the implementation of this research study, the experimental data set from Cranfield University’s Boeing 737-400 aircraft was utilized. The overall execution of the approach comprised background noise suppression, estimation of the spark repetition frequency and its fluctuation, spark event segmentation, and feature extraction, in order to monitor the state of the ignition system. The methodology successfully demonstrated the usefulness of the approach in terms of detecting inconsistencies in the behavior of the ignition exciter, as well as detecting trends in the degradation of spark acoustic characteristics. The identified features proved to be robust against non-stationary background noise, and were also found to be independent of the acoustic path between the igniter and microphone locations, qualifying an acoustics-based approach to be practically viable.

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PONCE, M., A. LÓPEZ, J. CORREA, J. ARAU, and J. M. ALONSO. "ELECTRONIC BALLAST FOR HID LAMPS WITH HIGH FREQUENCY SQUARE WAVEFORM TO AVOID ACOUSTIC RESONANCES." Journal of Circuits, Systems and Computers 13, no. 03 (June 2004): 651–63. http://dx.doi.org/10.1142/s0218126604001623.

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This paper presents a driver for a HID lamp based on the application of a high frequency current square waveform through the lamp with the goal of avoiding acoustic resonances. The proposed ballast is fed from a 12-V dc input voltage and is intended to be used in systems supplied from nonconventional sources, such as back-up batteries, photovoltaic generators and automotive applications. In order to initiate the discharge in the lamp, a specially-designed igniter supplied from the 12-V dc voltage is used to apply high voltage ignition peaks to the lamp. Experimental results obtained from a laboratory prototype for a 70-W Metal Halide lamp supplied at 30 kHz are also shown to evaluate the possibilities of the proposed topology.

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4

Dixon, S., C. Edwards, S. B. Palmer, and J. Reed. "Ultrasonic generation using a plasma igniter." Journal of Physics D: Applied Physics 34, no. 7 (March 20, 2001): 1075–82. http://dx.doi.org/10.1088/0022-3727/34/7/309.

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5

Ma, Xiaochi, Yifei Zhu, Yun Wu, Xiancong Chen, and Bingxuan Lin. "Multi-physics modeling of a spark plasma jet igniter." Journal of Physics D: Applied Physics 55, no. 3 (October 18, 2021): 035201. http://dx.doi.org/10.1088/1361-6463/ac2b65.

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6

Torregrosa, A. J., A. Broatch, A. Gil, and J. Gomez-Soriano. "Numerical approach for assessing combustion noise in compression-ignited Diesel engines." Applied Acoustics 135 (June 2018): 91–100. http://dx.doi.org/10.1016/j.apacoust.2018.02.006.

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7

Tokharski, J., C. West, and P. R. Smy. "Use of a plasma jet igniter as a gas pump." Journal of Physics D: Applied Physics 21, no. 12 (December 14, 1988): 1830–32. http://dx.doi.org/10.1088/0022-3727/21/12/029.

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8

Barkhudarov, E. M., N. K. Berezhetskaya, V. A. Kop'ev, I. A. Kossyi, N. A. Popov, M. I. Taktakishvili, and S. M. Temchin. "Ring-shaped electric discharge as an igniter of gas mixtures." Journal of Physics D: Applied Physics 43, no. 36 (August 25, 2010): 365203. http://dx.doi.org/10.1088/0022-3727/43/36/365203.

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9

Broatch, A., R. Novella, J. García-Tíscar, and J. Gomez-Soriano. "On the shift of acoustic characteristics of compression-ignited engines when operating with gasoline partially premixed combustion." Applied Thermal Engineering 146 (January 2019): 223–31. http://dx.doi.org/10.1016/j.applthermaleng.2018.09.089.

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10

Jafari, S. M., H. Mehdigholi, and M. Behzad. "Valve Fault Diagnosis in Internal Combustion Engines Using Acoustic Emission and Artificial Neural Network." Shock and Vibration 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/823514.

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This paper presents the potential of acoustic emission (AE) technique to detect valve damage in internal combustion engines. The cylinder head of a spark-ignited engine was used as the experimental setup. The effect of three types of valve damage (clearance, semicrack, and notch) on valve leakage was investigated. The experimental results showed that AE is an effective method to detect damage and the type of damage in valves in both of the time and frequency domains. An artificial neural network was trained based on time domain analysis using AE parametric features (AErms, count, absolute AE energy, maximum signal amplitude, and average signal level). The network consisted of five, six, and five nodes in the input, hidden, and output layers, respectively. The results of the trained system showed that the AE technique could be used to identify the type of damage and its location.

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11

Bauwens, Luc, C. Regis L. Bauwens, and Ida Wierzba. "Oscillating flames: multiple-scale analysis." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2107 (April 15, 2009): 2089–110. http://dx.doi.org/10.1098/rspa.2008.0388.

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A complete multiple-scale solution is constructed for the one-dimensional problem of an oscillating flame in a tube, ignited at a closed end, with the second end open. The flame front moves into the unburnt mixture at a constant burning velocity relative to the mixture ahead, and the heat release is constant. The solution is based upon the assumption that the propagation speed multiplied by the expansion ratio is small compared with the speed of sound. This approximate solution is compared with a numerical solution for the same physical model, assuming a propagation speed of arbitrary magnitude, and the results are close enough to confirm the validity of the approximate solution. Because ignition takes place at the closed end, the effect of thermal expansion is to push the column of fluid in the tube towards the open end. Acoustics set in motion by the impulsive start of the column of fluid play a crucial role in the oscillation. The analytical solution also captures the subsequent interaction between acoustics and the reaction front, the effect of which does not appear to be as significant as that of the impulsive start, however.

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12

Smy, P. R., J. Santiago, and D. Way-Nee. "Momentum imparted by plasma igniters to the surrounding gas." Journal of Physics D: Applied Physics 18, no. 5 (May 14, 1985): 827–33. http://dx.doi.org/10.1088/0022-3727/18/5/007.

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13

IKARI, Motonobu, Keisuke SUGIURA, Yojiro ISINO, and Norio OHIWA. "Experimental Study on Flame Propagation Characteristics of Spark Ignited Premixed Flame in a Plane Sheer Layer with Acoustic Excitation." Proceedings of the Symposium on Environmental Engineering 2001.11 (2001): 379–82. http://dx.doi.org/10.1299/jsmeenv.2001.11.379.

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14

Ekici, O., R. D. Matthews, and O. A. Ezekoye. "Geometrical and electromagnetic effects on arc propagation in a railplug ignitor." Journal of Physics D: Applied Physics 40, no. 24 (November 30, 2007): 7707–15. http://dx.doi.org/10.1088/0022-3727/40/24/018.

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15

Brooker, E., T. Plewa, and D. Fenn. "Type Ia supernovae deflagration-to-detonation transition explosions powered by the Zel’dovich reactivity gradient mechanism." Monthly Notices of the Royal Astronomical Society: Letters 501, no. 1 (December 15, 2020): L23—L27. http://dx.doi.org/10.1093/mnrasl/slaa141.

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ABSTRACT Our aim in this work is to identify and explain the necessary conditions required for an energetic explosion of a Chandrasekhar-mass white dwarf. We construct and analyse weakly compressible turbulence models with nuclear burning effects for carbon/oxygen plasma at a density expected for the deflagration-to-detonation transition (DDT) to occur. We observe the formation of carbon deflagrations and transient carbon detonations at early times. As turbulence becomes increasingly inhomogeneous, sustained carbon detonations are initiated by the Zel’dovich reactivity gradient mechanism. The fuel is suitably preconditioned by the action of compressive turbulent modes with wavelength comparable to the size of resolved turbulent eddies; no acoustic wave is involved in this process. Oxygen detonations are initiated, aided either by reactivity gradients or by collisions of carbon detonations. The observed evolutionary time-scales are found to be sufficiently short for the above process to occur in the expanding, centrally ignited massive white dwarf. The inhomogeneous conditions produced prior to the DDT might be of consequence for the chemical composition of the outer ejecta regions of Type Ia supernovae from the single degenerate channel, and offer the potential for validation of the proposed model.

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16

Chebotnyagin, L. M., V. V. Potapov, N. A. Ivanov, and N. N. Ivanchik. "Compacting nanopowder materials by a pulse pressure generated by expanding plasma channel of a spark ignited by wire electrical explosion." Proceedings of Irkutsk State Technical University 24, no. 6 (January 13, 2021): 1297–310. http://dx.doi.org/10.21285/1814-3520-2020-6-1297-1310.

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The purpose of the article is to explore the possibilities of powder material compaction by the pressure pulse of an electric explosion of a conductor, establish a functional relationship between the parameters of the pressure pulse and an electrical technological installation for powder material compaction, select the parameters for pulse pressure amplitude and duration adjustment, and specify the design options of the working tool for powder material compaction. Analytical studies have been carried out on the basis of the method of formalized representation of the development of the process of pulse pressure wave formation and propagation where the latter is created by an expanding plasma channel of an electric spark in a transmitting medium initiated by an electric explosion of a wire. The simulation of high-speed de formation of the pipe wall under the action of the pulse pressure is carried out in the MATLAB software package. A scanning electron microscope is used to study the microstructure of the breakage of the compacted material with nanomodifiers. Based on the experimental studies on powder material compaction by the pulse pressure created by the expanding plasma channel of a spark initiated by an electric explosion of a wire when the current pulse f rom an electrotechnological installation is supplied to it, it has been determined that the magnitude and shape of the pressure pulse are most influenced by the parameters of this installation. Based on the obtained model studies, the optimal modes for compaction of nanomodified powders have been selected. The relationship is obtained between the parameters of the pulse pressure (Pm amplitude and pressure wave propagation form) and the electrotechnological installation (voltage, inductance, capacitance). It is proposed to use an acoustic-electric wave model to estimate the pressure that provides high-speed deformation of metal pipes, and to plot a deformation profile of metal pipes used for compaction. Analysis of SEM images of the fractures obtained in compact experiments has showed a high degree of particle compaction with the formation of a solid composite.

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17

ISHINO, Yojiro, Takeshi SANO, Keisuke SUGIURA, and Norio OHIWA. "Vortex-Flame Interaction of Spark-Ignited Flame with Coherent Structure in the Plane Premixed Shear Flows. Active Control of Coherent Structure Property by Acoustic Excitation." Transactions of the Japan Society of Mechanical Engineers Series B 67, no. 664 (2001): 3183–88. http://dx.doi.org/10.1299/kikaib.67.3183.

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18

Kataria, Aman, Smarajit Ghosh, Vinod Karar, Takshi Gupta, Kathiravan Srinivasan, and Yuh-Chung Hu. "Improved Diver Communication System by Combining Optical and Electromagnetic Trackers." Sensors 20, no. 18 (September 7, 2020): 5084. http://dx.doi.org/10.3390/s20185084.

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The increasing need for observation in seawater or ocean monitoring systems has ignited a considerable amount of interest and the necessity for enabling advancements in technology for underwater wireless tracking and underwater sensor networks for wireless communication. This type of communication can also play an important role in investigating ecological changes in the sea or ocean-like climate change, monitoring of biogeochemical, biological, and evolutionary changes. This can help in controlling and maintaining the production facilities of outer underwater grid blasting by deploying unmanned underwater vehicles (UUVs). Underwater tracking-based wireless networks can also help in maintaining communication between ships and divers, submarines, and between multiple divers. At present, the underwater acoustic communication system is unable to provide the data rate required to monitor and investigate the aquatic environment for various industrial applications like oil facilities or underwater grit blasting. To meet this challenge, an optical and magnetic tracking-based wireless communication system has been proposed as an effective alternative. Either optical or magnetic tracking-based wireless communication can be opted for according to the requirement of the potential application in sea or ocean. However, the hybrid version of optical and wireless tracking-based wireless communication can also be deployed to reduce the latency and improve the data rate for effective communication. It is concluded from the discussion that high data rate optical, magnetic or hybrid mode of wireless communication can be a feasible solution in applications like UUV-to-UUV and networks of aquatic sensors. The range of the proposed wireless communication can be extended using the concept of multihop.

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19

Firak, Mihajlo. "Comparative analysis of the solar dish electricity production." Thermal Science 9, no. 3 (2005): 69–83. http://dx.doi.org/10.2298/tsci0503069f.

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Round parabolic solar mirror is of ten called the solar or sun dish. Even when the dish is faceted into several smaller dishes (facets) which are all focusing the sunlight in the single point (focus), it is called a solar dish. When solar radiation to electricity converter is mounted into the dish focus and the sun-tracking system is provided, it could be named solar dish/converter system. Depending on the sort of the converter, two promising systems which are approaching the commercialization could be mentioned. These are solar dish/Sterling system and solar dish/photo voltaic system. In this paper, majority of the technical and economical aspects of the two systems are examined and compared. Two systems are chosen to represent this: SAIC/STM Sun Dish TM, solar dish with Sterling heat engine/generator, and Solar Systems SS20TM representing solar dish with concentrating photovoltaic converter. It is concluded that solar dish with concentrated photovoltaic converter can have much better cost/performance ratio. It is also concluded that recently introduced thermo acoustical converter and photovoltaic cavity converter, probably des ignites future development of the solar dish systems. World?s potential of in stalling solar dish systems according to geographic and climate conditions wisest mated. Also, the number of solar dishes which could, in stalled in Croatia cover yearly state?s electricity consumption was calculated.

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20

Zhong, Yujie, Hao Wu, Xiandi Li, Jiamao Gao, Wei Jiang, Ya Zhang, and Giovanni Lapenta. "Numerical characterization of the breakdown process of dc-driven micro-discharges sustained by thermionic emission." Journal of Physics D: Applied Physics 55, no. 21 (February 25, 2022): 215203. http://dx.doi.org/10.1088/1361-6463/ac4fd4.

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Abstract Because of the larger surface-area-to-volume ratio, micro-discharges can be sustained by surface emission processes. If the cathode is heated, a micro-discharge can be sustained mainly by thermionic emission. However, we still know little about how this kind of plasma is ignited and sustained. In order to explore the breakdown process of dc-driven micro-discharge sustained by thermionic emission, a one-dimensional implicit particle-in-cell/Monte Carlo collision method is adopted, coupled with the external circuit and thermionic emission model. The breakdown process of micro-discharge lasts about 8 μ s , and this process can be roughly divided into two phases, i.e. pre-breakdown and breakdown phase. The dynamic plasma parameters during the evolution process are analyzed, such as particle density, electron energy distribution function, electric potential, average particle temperature, and particle current density. The plasma electrical characteristics as well as the article and power balance, are also presented to show the evolutionary features of the whole gas breakdown process.

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21

Yao, Xiaomei, Nan Jiang, Bangfa Peng, He Guo, Na Lu, Kefeng Shang, Jie Li, and Yan Wu. "Characteristics of a corona discharge ignited by a MgO/NiO/Ni sandwich cathode with high secondary electron emission for VOC degradation." Journal of Physics D: Applied Physics 51, no. 43 (September 18, 2018): 435201. http://dx.doi.org/10.1088/1361-6463/aadddd.

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22

Deheuvels, S., and K. Belkacem. "Seismic characterization of red giants going through the helium-core flash." Astronomy & Astrophysics 620 (December 2018): A43. http://dx.doi.org/10.1051/0004-6361/201833409.

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Context. First-ascent red giants in the approximate mass range 0.7 ≲ M/M⊙ ≲ 2 ignite helium in their degenerate core as a flash. Stellar evolution codes predict that the He flash consists of a series of consecutive subflashes. Observational evidence of the existence of the He flash and subflashes is lacking. The detection of mixed modes in red giants from space missions CoRoT and Kepler has opened new opportunities to search for such evidence. Aims. During a subflash, the He-burning shell is convective, which splits the cavity of gravity modes in two. We here investigate how this additional cavity modifies the oscillation spectrum of the star. We also address the question of the detectability of the modes, to determine whether they could be used to seismically identify red giants passing through the He flash. Methods. We calculate the asymptotic mode frequencies of stellar models going through a He subflash using the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation. To predict the detectability of the modes, we estimate their expected heights, taking into account the effects of radiative damping in the core. Our results are then compared to the oscillation spectra obtained by numerically calculating the mode frequencies during a He subflash. Results. We show that during a He subflash, the detectable oscillation spectrum mainly consists of modes trapped in the acoustic cavity and in the outer g-mode cavity. The spectrum should thus at first sight resemble that of a core-helium-burning giant. However, we find a list of clear, detectable features that could enable us to identify red giants passing through a He subflash. In particular, during a He subflash, several modes that are trapped in the innermost g-mode cavity are expected to be detectable. We show that these modes could be identified by their frequencies or by their rotational splittings. Other features, such as the measured period spacing of gravity modes or the location of the H-burning shell within the g-mode cavity could also be used to identify stars going through a He subflash. Conclusions. The features derived in this study can now be searched for in the large datasets provided by the CoRoT and Kepler missions.

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23

Ghimire, Bhagirath, Bethany L. Patenall, Endre J. Szili, Nishtha Gaur, Pradeep Lamichhane, Naing T. Thet, Dhruv Trivedi, Andrew Toby A. Jenkins, and Robert D. Short. "The influence of a second ground electrode on hydrogen peroxide production from an atmospheric pressure argon plasma jet and correlation to antibacterial efficacy and mammalian cell cytotoxicity." Journal of Physics D: Applied Physics 55, no. 12 (December 28, 2021): 125207. http://dx.doi.org/10.1088/1361-6463/ac43d9.

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Abstract This study investigates how addition of a 2nd ground electrode in an argon plasma jet influences the production of hydrogen peroxide (H2O2) in deionised water (DIW). Briefly, plasma is ignited by purging argon gas through a quartz tube at 1 l min−1 and applying a sinusoidal voltage of 7 kV (peak–peak) at 23.5 kHz to a high voltage stainless steel needle electrode sealed inside the quartz tube surrounded by one or two copper ring(s) that served as the ground electrode(s) situated downstream of the high voltage electrode. The mechanisms of H2O2 production are investigated through the electrical and optical plasma properties and chemical analysis of the treated DIW. We discover that the addition of a 2nd ground electrode results in higher accumulation of charges on the inner wall surface of the quartz tube of the plasma jet assembly resulting in an increase in the discharge current and dissipated power. This further leads to an increase in the electron temperature that more than doubles the H2O2 production through dissociative recombination of water vapour molecules, whilst still maintaining a biological tissue tolerable gas temperature. The double ground electrode plasma jet is shown to be highly effective at reducing the growth of common wound pathogens (Pseudomonas aeruginosa and Staphylococcus aureus) in both planktonic and biofilm states whilst inducing a low level of cytotoxicity in HaCaT keratinocyte skin-like cells under certain conditions. The information provided in this study is useful in understanding the complex physicochemical processes that influence H2O2 production in plasma jets, which is needed to optimise the development of plasma sources for clinical applications.

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24

Schücke, Lars, Arisa Bodnar, Niklas Friedrichs, Alexander Böddecker, Niklas Peters, Kevin Ollegott, Christian Oberste-Beulmann, et al. "Optical absorption spectroscopy of reactive oxygen and nitrogen species in a surface dielectric barrier discharge." Journal of Physics D: Applied Physics 55, no. 21 (February 28, 2022): 215205. http://dx.doi.org/10.1088/1361-6463/ac5661.

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Abstract A twin surface dielectric barrier discharge (SDBD) ignited in a dry synthetic air gas stream is studied regarding the formation of reactive oxygen and nitrogen species (RONS) and their impact on the conversion of admixed n-butane. The discharge is driven by a damped sinusoidal voltage waveform at peak-to-peak amplitudes of 8 kVpp–13 kVpp and pulse repetition frequencies of 250 Hz–4000 Hz. Absolute densities of O3, NO2, NO3, as well as estimates of the sum of the densities of N2O4 and N2O5 are determined temporally resolved by means of optical absorption spectroscopy using a laser driven broadband light source, suitable interference filters, and a photodiode detector. The measured densities are acquired across the center of the reactor chamber as well as at the outlet of the chamber. The temporal and spatial evolution of the species’ densities is correlated to the conversion of n-butane at concentrations of 50 ppm and 400 ppm, measured by means of flame ionization detectors. The n-butane is admixed either before or after the reactor chamber, in order to separate the impact of short- and long-lived reactive species on the conversion process. It is found that, despite the stationary conversion at the selected operating points, at higher voltages and repetition frequencies the densities of the measured species are not in steady state. Based on the produced results it is presumed that the presence of n-butane modifies the formation and consumption pathways of O3. At the same time, there is no significant impact on the formation of dinitrogen oxides (N2O4 and N2O5). Furthermore, a comparatively high conversion of n-butane, when admixed at the outlet of the reactor chamber is observed. These findings are discussed together with known rate coefficients for the reactions of n-butane with selected RONS.

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25

Flores-Montoya, Enrique, Victor Muntean, Mario Sánchez-Sanz, and Daniel Martínez-Ruiz. "Non-adiabatic modulation of premixed-flame thermoacoustic frequencies in slender tubes." Journal of Fluid Mechanics 933 (January 6, 2022). http://dx.doi.org/10.1017/jfm.2021.1092.

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This paper presents an experimental study of the influence of heat losses on the onset of thermoacoustic instabilities in methane–air premixed flames propagating in a horizontal tube of diameter, $D = 10$ mm. Flames are ignited at the open end of the tube and propagate towards the closed end undergoing strong oscillations of different features owing to the interaction with acoustic waves. The frequency of oscillation and its axial location are controlled through the tube length $L$ and the intensity of heat losses. These parameters are respectively modified in the experiments by a moveable piston and a circulating thermal bath of water prescribing temperature conditions. Main experimental observations show that classical one-dimensional predictions of the oscillation frequency do not accurately describe the phenomena under non-adiabatic real scenarios. In addition to the experimental measurements, a quasi-one-dimensional analysis of the burnt gases is provided, which introduces the effect of heat losses at the wall of the tube on the interplay between the acoustic field and the reaction sheet. As a result, this analysis provides an improved description of the interaction and accurately predicts the excited flame-oscillation harmonics through the eigenvalues of the non-adiabatic acoustics model. Unlike the original one-dimensional analysis, the comparison between the flame oscillation frequency provided by the non-adiabatic extended theory and the frequencies measured in our experiments is in excellent agreement in the whole range of temperatures considered. This confirms the importance of heat losses in the modulation of the instabilities and the transition between different flame oscillation regimes.

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Broatch, Alberto, J. Javier Lopez, Jorge García-Tíscar, and Josep Gomez-Soriano. "Experimental Analysis of Cyclical Dispersion in Compression-Ignited Versus Spark-Ignited Engines and Its Significance for Combustion Noise Numerical Modeling." Journal of Engineering for Gas Turbines and Power 140, no. 10 (June 25, 2018). http://dx.doi.org/10.1115/1.4040287.

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As noise pollution remains one of the biggest hurdles posed by thermal engines, increasing efforts are made to alleviate the generation of combustion noise from the early design stage of the chamber. Since the complexity of both modern chamber geometries and the combustion process itself precludes robust analytic solutions, and since the resonant, highly three-dimensional pressure field is difficult to be measured experimentally, focus is put on the numerical modeling of the process. However, in order to optimize the resources devoted to this simulation, an informed decision must be made on which formulations are followed. In this work, the experimental cyclic dispersion of the in-cylinder pressure is analyzed in two typical compression-ignited (CI) and spark-ignited (SI) engines. Acoustic signatures and pressure rise rates (PRRs) are derived from these data, showing how while the preponderance of flame front propagation and dependency of previous cycle in SI engine noise usually calls for multicycle, more complex turbulence modeling such as large Eddy simulation (LES), simpler unsteady Reynolds-averaged Navier-Stokes (URANS) formulations can accurately characterize the more consistent pressure spectra of CI thermal engines, which feature sudden autoignition as the main noise source.

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27

Kang, Xiaoli, Chunhong Li, Wen Cui, Hao Yuan, Zhengshang Wang, Zhou Zheng, and Xudong Cui. "Facile electro-thermal igniters based on freestanding CNTs films for ignition of energetic materials." Journal of Physics D: Applied Physics, September 23, 2022. http://dx.doi.org/10.1088/1361-6463/ac9486.

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Abstract Facile electro-thermal igniters based on freestanding CNTs films are studied for the use of igniting energetic materials. Electro-thermal temperature rises, dynamic pictures of ignition process, temporal changes of voltage, current and resistance as well as ignition ability of freestanding CNTs film-based igniters with different film thickness are compared with their counterparts which have paper-like substrate. Results showed that freestanding CNTs film-based igniters had faster electro-thermal temperature rises and better ignition ability than their counterparts. Ignition delay of loaded energetic materials employing freestanding CNTs film based-igniters was only 40%~67% of their counterparts depending on the film thickness. Freestanding CNTs film-based igniters with larger thickness were more suitable for rapid ignition of energetic materials. The shortest ignition delay for igniters of 8×8 mm bridge area under 20 V was less than 80 ms. The initial temperature rise rate of igniters was the key that decided the ignition delays of loaded energetic materials. The existence of substrate in CNTs film-based igniters impeded their temperature rise rate and thus increased ignition delay of loaded energetic materials. Besides, owing to the property of negative resistance-temperature coefficient, freestanding CNTs film-based igniters are favourable for realization of low voltage ignition of energetic materials.

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28

Novella, Ricardo, Benjamín Pla, Pau Bares, and Irina Jiménez. "Acoustic characterization of combustion chambers in reciprocating engines: An application for low knocking cycles recognition." International Journal of Engine Research, December 22, 2020, 146808742098056. http://dx.doi.org/10.1177/1468087420980565.

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In this paper the acoustic response of a combustion chamber is studied by assuming different pressure field excitation. The viscous effects on the combustion chamber and the finite impedance of the walls have been modeled with a first order system, which damps the resonance oscillation created by combustion. The characterization of the acoustic response of the combustion chamber has been used to identify the source of the excitation in order to distinguish normal combustion from knock. Two engines, a conventional spark ignited (SI) and a turbulent jet ignition (TJI) engine, were used, fueled with gasoline and compressed natural gas (CNG), respectively. The pressure fluctuations in the combustion chambers are analyzed and a pattern recognition system identifies the most likely source of excitation. This new criteria for knock identification permits a more consistent differentiation between knocking and no-knocking cycles, independent on the amplitude of the phenomenon, thus allowing the improvement for knock control algorithms, specially with combustion modes which heavily excite resonance, such as turbulent jet ignition or homogeneous charge compression ignition (HCCI).

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29

Cai Banghuang, Cai Banghuang, Huimin Song, Zhibo Zhang, Min Jia, Wei zhen Wang, and Dong Lin. "Experimental investigation of C-shape embedded multi-channel plasma igniter in a single-head swirl combustor." Journal of Physics D: Applied Physics, December 21, 2020. http://dx.doi.org/10.1088/1361-6463/abd585.

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30

Bothien, Mirko, Demian Lauper, Yang Yang, and Alessandro Scarpato. "Reconstruction and Analysis of the Acoustic Transfer Matrix of a Reheat Flame From Large-Eddy Simulations." Journal of Engineering for Gas Turbines and Power 141, no. 2 (October 4, 2018). http://dx.doi.org/10.1115/1.4041151.

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Lean premix technology is widely spread in gas turbine combustion systems, allowing modern power plants to fulfill very stringent emission targets. These systems are, however, also prone to thermoacoustic instabilities, which can limit the engine operating window. The thermoacoustic analysis of a combustor is thus a key element in its development process. An important ingredient of this analysis is the characterization of the flame response to acoustic fluctuations, which is straightforward for lean-premixed flames that are propagation stabilized, since it can be measured atmospherically. Ansaldo Energia's GT26 and GT36 reheat combustion systems feature a unique technology where fuel is injected into a hot gas stream from a first combustor, which is propagation stabilized, and auto-ignites in a sequential combustion chamber. The present study deals with the flame response of mainly auto-ignition stabilized flames to acoustic and temperature fluctuations for which a computational fluid dynamics system identification (SI) approach is chosen. The current paper builds on recent works, which detail and validate a methodology to analyze the dynamic response of an auto-ignition flame to extract the flame transfer function (FTF) using unsteady large-Eddy simulations (LES). In these studies, the flame is assumed to behave as a single-input single-output (SISO) or a multi-input single-output (MISO) system. The analysis conducted in GT2015-42622 qualitatively highlights the important role of temperature and equivalence ratio fluctuations, but these effects are not separated from velocity fluctuations. Hence, this topic is addressed in GT2016-57699, where the flame is treated as a multiparameter system and compressible LES are conducted to extract the frequency-dependent FTF to describe the effects of axial velocity, temperature, equivalence ratio, and pressure fluctuations on the flame response. For lean-premixed flames, a common approach followed in the literature assumes that the acoustic pressure is constant across the flame and that the flame dynamics are governed by the response to velocity perturbations only, i.e., the FTF. However, this is not necessarily the case for reheat flames that are mainly auto-ignition stabilized. Therefore, in this paper, we present the full 2 × 2 transfer matrix of a predominantly auto-ignition stabilized flame, and hence, describe the flame as a multi-input multi-output (MIMO) system. In addition to this, it is highlighted that in the presence of temperature fluctuations, the 2 × 2 matrix can be extended to a 3 × 3 matrix relating the primitive acoustic variables as well as the temperature fluctuations across the flame. It is shown that only taking the FTF is insufficient to fully describe the dynamic behavior of reheat flames.

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Suhaimi, Mohd Suardi, Aminuddin Saat, Mazlan A. Wahid, and Mohsin Mohd Sies. "FLAME PROPAGATION AND BURNING RATES OF METHANE-AIR MIXTURES USING SCHLIEREN PHOTOGRAPHY." Jurnal Teknologi 78, no. 10-2 (October 4, 2016). http://dx.doi.org/10.11113/jt.v78.9664.

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Different methodology have been shown to produce different results for Markstein length and laminar burning velocity of methane-air mixture.This study attempts to determine the aforesaid parameters using the newly developed closed vessel combustion chamber with Schlieren photography. Markstein length and burning rate of methane-air mixture was determined under the initial pressure of 1 atm, temperature range of 298-302K and equivalence ratio range of 0.7-1.3. Experiments were performed in a centrally ignited 29.16L cylindrical constant volume combustion chamber. Ignition energy was set at 25mJ for each experiment. The images of spherically expanding flame were recorded using Schlieren photography technique at a speed of 2000 frame per second. Analysis of the flame area yield flame radii from which the flame speed and stretch rate could be obtained. These parameters would allow the determination of Markstein length and burning rate of the flame. Results show that Markstein length magnitude increases proportionally with equivalence ratio with a magnitude ranging from 0.125cm to 0.245cm. Maximum burning rate occurs at equivalence ratio of 1.1 with a magnitude of 0.366 m/s. Flame of each equivalence ratio also exhibits fluctuation arising from acoustic disturbance. This disturbance becomes more apparent at higher equivalence ratio.

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He, Xiaojian, Xiangyang Liu, and Jianping Wang. "Numerical study of the mechanisms of the longitudinal pulsed detonation in two-dimensional rotating detonation combustors." Physics of Fluids, March 2, 2023. http://dx.doi.org/10.1063/5.0136290.

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A numerical study of the longitudinal pulsed detonation (LPD) is conducted in the present paper. The occurrence mechanism of the LPD, called shock wave amplification by coherent energy release (SWACER) is verified preliminarily in this study. To be specific, upstream propagating shock waves, which originate from the outlet, induce a specific gradient of reactant distribution and then detonation waves are ignited and evolve along the gradient in close succession. It is worth noting that the occurrence of LPD does not mean that the LPD will necessarily be sustained. The low injection pressure ratio PR (i.e. the ratio of inlet pressure to outlet pressure) = 1.3 is found to be conducive to the sustenance of the LPD instability in the baseline model. A lower PR (PR {less than or equal to} 1.2) or a slightly higher PR (1.4 {less than or equal to} PR {less than or equal to} 1.8) shall lead to an unstable detonation or a quenching of detonations, while a much higher PR (PR > 1.8) contributes to the formation of stable canonical rotating detonation waves. In addition, the combustion regimes of five combustors of different heights at different PR are explored. As the combustion chamber height increases, the PR of the sustainable LPD is nearly linearly increasing and its operating frequency decreases gradually. The calculation formula between the sustainable LPD propagating frequency and natural acoustic resonance frequency of the combustor is employed and discussed, but in consideration of its imperfection further investigation is required.

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KHAN, JAVED ALAM, Ramakant Sharma, Ajay Singh Panwar, and Dipti Gupta. "Impact of non-fullerene acceptors and solvent additive on the nanomorphology, device performance, and photostability of PTB7-Th polymer based organic solar cells." Journal of Physics D: Applied Physics, October 5, 2022. http://dx.doi.org/10.1088/1361-6463/ac97a3.

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Abstract Non-fullerene acceptors have recently ignited extensive interest in organic solar cells (OSCs) because of their higher power conversion efficiency (PCE) than their fullerene counterparts. Though the effect of solvent additive 1, 8-diiodooctane (DIO) has been studied extensively for fullerene-based acceptor OSCs, not much is known for non-fullerene acceptors OSCs. In our work, bulk-heterojunction (BHJ) OSCs were fabricated by blending fullerene (PC71BM) and non-fullerene (ITIC and IEICO-4F) acceptors with low bandgap polymer donor (PTB7-Th). Further, the effects of non-fullerene acceptors on the nanomorphology, performance, and photostability of the devices were investigated. In the absence of DIO, devices with IEICO-4F acceptor showed higher PCE than PTB7-Th: ITIC and PTB7-Th: PC71BM BHJ-OSCs due to their absorption in near IR along with high Jsc. The addition of DIO increased PCE in PTB7-Th: PC71BM BHJ-OSCs due to improved miscibility of fullerene molecules, higher donor/acceptor interface area, and improved phase separation. However, DIO adversely affected the overall device performance in PTB7-Th: IEICO-4F and PTB7-Th: ITIC BHJ-OSCs. Furthermore, devices processed with DIO were less photostable and exhibited faster degradation due to the photoacid effect of the DIO additive.

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Journal articles on the topic 'Acoustic igniter'

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