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Introduction
Published in Ajoy K. Bose, Military Pyrotechnics, 2021
Deflagration and detonation depend upon the rate of combustion with respect to speed of sound. Detonation occurs when the rate of combustion is higher than the speed of sound, while deflagration occurs when the rate of combustion is lower than speed of sound. Deflagration moves layer by layer while detonation involves shockwaves in the explosive.
Computational fluid dynamics analysis and extended adaptive hybrid functions model-based design optimization of an explosion-proof safety valve
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Chaoyong Zong, Qingye Li, Kunpeng Li, Xueguan Song, Dianjing Chen, Xiaofeng Li, Xuebin Wang
The explosion of a large diesel engine is one type of deflagration phenomenon caused by the ignition of a high-concentration oil mist. Unlike conventional explosions such as detonation, deflagration is a subsonic combustion wave in which the pressure increases rapidly but not drastically. The pressure increase in the vessel will cause the valve disc to be lifted to release the excess fluid medium, so as to prevent catastrophic consequences; when the fuel in the container burns out, the explosion-proof safety valve will be closed because there is not enough fluid force to balance the valve spring force. To simulate the valve opening process, the rate of pressure rise v (Equation 1) of the pressure vessel is defined as 3 MPa/s, and the duration of the explosion is defined as 33 ms to ensure that the valve disc can be lifted to a certain level. For the valve reclosure process, the rate of pressure rise v is set to be 0, namely, no pressure/energy will be generated and the pressure of the vessel will be updated according to the transient flux through the valve inlet, as shown in Equation (1).
Explosion characteristics and energy utilisation of coal mine ultra-lean methane
Published in Combustion Theory and Modelling, 2021
Baisheng Nie, Chao Peng, Jie Gong, Feifei Yin, Kedi Wang
The deflagration explosion index is a characteristic index that measures the destructiveness of a material explosion. It can reflect the impact of the explosion on the container. Kg, the gas or vapour deflagration index, which represents the danger of explosion, is calculated from (dP/dt)max and the spherical explosion apparatus volume by means of the cubic law [51]: where V is the explosion device volume. In this study, the experimental device is 20L spherical explosion apparatus, the unit volume is constant, thus the change trend of Kg is consistent with the change of (dP/dt)max.
Characteristics Analysis of Post-Explosion Coal Dust Samples by X-ray Diffraction
Published in Combustion Science and Technology, 2018
Jifa Qian, Zhentang Liu, Song Lin, Xuelong Li, Sen Hong, Dexing Li
The parameters assessed during explosion trials consisted of the maximum pressure, Pmax, the maximum rate of pressure rise, (dP/dt)max, the ignition time, t, and the deflagration index, Kst. The ignition time is defined as the time span from the initial internal pressure of zero to the maximum pressure (Li et al., 2012; Li et al., 2011). The deflagration index eliminates the effects of the experimental device on the explosion parameters and is defined as the maximum rate of pressure rise in a 1 m3 space (Abbasi and Abbasi, 2007).