NUMERICAL AND EXPERIMENTAL INVESTIGATION OF METHANE-OXYGEN DETONATION IN A 9 M LONG TUBE
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In advanced detonation engines for propulsion and in strong accidental explosions with detonation development, spatially inhomogeneous mixtures may occur which can greatly affect the detonation propagation. In this study, detonation propagation in spatially inhomogeneous mixtures is investigated via numerical simulation considering detailed chemistry. The two-dimensional (2D) periodic sinusoidal distribution of reactant concentration is introduced in the inhomogeneous region. The emphasis is on assessing the effects of such spatially inhomogeneous mixture on local explosion and subsequent detonation development. It is found that successful detonation propagation always occurs in the spatially inhomogeneous mixtures with 2D periodic sinusoidal distribution of reactant concentration. This is interpreted through the formation and collision of curved shocks, local autoignition, and explosions happened in the first sinusoidal period. Moreover, the effects of wavelength and amplitude of sinusoidal distribution on the cellular structure and detonation speed are assessed. It is found that the detonation speed decreases as both the wavelength and amplitude increase. Unlike the detonation speed, three modes of the cellular structure, respectively, from the original cellular structure and local explosion are identified depending on the values of wavelength and amplitude. Furthermore, the position of the first local explosion is always found to be located in the high reactivity zones of the second half of first sinusoidal period. Furthermore, comparison between simulation results for one-dimensional (1D) and 2D periodic sinusoidal distribution of reactant concentration indicates that the formation of curved shocks and their collision caused by 2D sinusoidal distribution are crucial for successful detonation propagation in the inhomogeneous region. The present study helps to understand the detonation propagation in inhomogeneous mixtures.
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Abstract As a promising method for synthesizing nanosized materials, detonation method was used to prepare TiO 2 nanoparticles. A new method for predicting the Chapman‐Jouguet (C‐J) detonation parameters of C a H b O c N d Ti e explosives, such as detonation heat, detonation temperature, and detonation pressure, was introduced according to the approximate reaction equations of detonation. The coefficient of oxygen balance of explosive was also calculated according to the specific detonation synthesis experiment. The calculation method was more useful in predicting the formation processes of detonation products and optimizing the experimental procedure. It could also support theory foundation for further experiments to some extent.
Nanocrystalline material
Oxygen balance
Detonation velocity
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Reflection
Mach reflection
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Nonstationary propagation of detonation is frequently observed in charges encapsulated in shells or located in blastholes and boreholes when explosives are used for crushing rocks or intensifying oil extraction. It is also observed in charges with elongated cavities. This effect is related to the appearance and propagation of wave disturbances and jets moving ahead of the detonation front. This can lead both to the interruption of detonation and to its accelerated propagation. Under certain conditions, a pulsating behavior can occur when the detonation velocity is changing periodically. The chapter discusses some examples of these processes. Nonstationary detonation processes, which are caused by specific channel effects, may be observed in elongated explosive charges with cavities. Another class of nonstationary detonation propagation processes may be observed in experiments when the charge is in contact with shells or walls made of materials in which the sound velocity exceeds the detonation velocity.
Detonation velocity
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WT5”BZ]The comparative experimental study on the single detonation wave of an ethyne air mixture under various conditions was made.The effect of the detonation chamber closeness on the detonation wave formation was studied.It was found that the developed detonation wave (CJ detonation) was produced when the detonation chamber was completely closed,but the strength of the detonation wave was obviously decreased when one end of the detonation chamber was closed and the other end was open. [WT5”HZ]
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Abstract For the experimental determination of detonation parameters (such as detonation velocity, detonation pressure, detonation products mass velocity, detonation temperature, etc.) of an explosive, various dynamic methods, based on different physical principles, are applied. For this purpose, various experimental methods, as well as testing apparatuses and procedures, are used. At the same time, due to unusual (extreme) values of detonation parameters (detonation velocity reaches 10 mm/μs, detonation pressure up to 400 kbar, detonation temperature ranges from 2000 to 5000 K, duration time of the chemical reactions in the reaction zone is of the order of microseconds, and the width of the chemical reaction zone ranges from tenths of a micrometer to several millimetres), it is very difficult to achieve an entirely reliable experimental determination of some detonation parameters. Detonation velocity is one of the most important parameters of an explosive, which nowadays can be measured very accurately. Its measurement is based on the application of some detonation wave properties and various ultrafast signal recording techniques. This paper summarises research work done in this field.
Detonation velocity
Microsecond
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Equivalence ratio
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Calculations of the interaction of plane (one-dimensional) and cellular (two-dimensional) detonation waves in hydrogen-air mixture with inert filters were carried out on the basis of the proposed physical and mathematical models, based on the detailed and reduced kinetics, describing such processes. The realized detonation regimes of attenuation and suppression of detonation were revealed. Comparison of results obtained by detailed and reduced kinetics showed that reduced kinetics gives overestimated detonation velocities compared to the detailed kinetics. But the obtained concentration limits of detonation practically equal to each other for both kinetics models. Comparison of processes of attenuation and suppression of plane and cellular detonation showed that the suppression of cellular detonation is more difficult to achieve compared to a plane detonation wave. Detonation failure criterion that shows that at the increasing the filter particles diameter, it is necessary to increase the volume concentration proportionally in order to successfully suppress detonation both in the case of a plane detonation wave and in the case of cellular detonation, was obtained.
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Point source
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Rotating detonation engines are studied more and more widely because of high thermodynamic efficiency and high specific impulse. Rotating detonation of hydrogen and oxygen was achieved in this study. Rotating detonation waves were observed by high speed cameras and detonation pressure traces were recorded by PCB pressure sensors. The velocity of rotating detonation waves is fluctuating during the run. Low frequency detonation instabilities, intermediate frequency detonation instabilities and high frequency detonation instabilities were discovered. They are relevant to unsteady heat release, acoustic oscillations and rotating detonation waves.
Detonation velocity
Specific impulse
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