Effect of mass concentration and apparent morphology of coal particle on the detonation onset of coal/ethylene/oxygen mixture

Abstract

In order to realize the reliable ignition of coal particle continuous rotating detonation engine, this study investigated the influence mechanism of coal particle concentration and apparent morphology on the initiation characteristics of coal/ethylene/oxygen mixture. Under the ethylene atmosphere (Initial total pressure is 100 kPa, equivalent ratio 0.5), a high-energy electric ignition device was used to carry out the direct initiation experiments on the coal-oxygen mixture under different coal particle equivalent ratios and apparent morphologies. The experimental results are as follows: after adding a small amount of 5PA coal particle(the two kinds of coal particle used in the experiment are recorded as PA and FA respectively. PA and FA are the abbreviations of porous anthracite and flaky anthracite respectively, such as 5 μm porous coal particle can be shortened to 5PA coal particle), the critical initiation energy of the ethylene/oxygen mixture decreases rapidly, reaching its minimum value of 2.53 J at the global equivalent ratio of 0.7, and the critical initiation energy of the coal/ethylene/oxygen mixture gradually increases as the equivalent ratio continues increasing. The critical initiation energy (5.20 J) of 5FA coal particle at the global equivalent ratio of 1.0 is higher than the critical initiation energy of 5PA(2.95 J). Under the ignition energy of 5.8 J, the 5PA coal particle and 5FA coal particle can be directly detonated in the range of global equivalent ratio 0.7−1.5. Under the ignition energy of 4.10 J, the 5PA coal particle can be directly detonated in the range of global equivalent ratio 0.7−1.5, but the 5FA coal particle can only be directly detonated at the global equivalent ratio of 0.7, and cannot be detonated after further increasing the global equivalent ratio. The research results show that, for lean fuel ethylene/oxygen(equivalent ratio less than 1), coal particle can promote the formation and self-sustaining propagation of the detonation wave within a certain mass concentration range of coal particle, but the high concentration of coal particle would inhibit the formation and self-sustaining propagation of the detonation wave. The apparent morphology of coal particle would affect the detonation initiation characteristics of coal particle mixture. Compared with the flaky coal particle, the porous coal particle has a higher chemical reaction rate leading to a lower critical initiation energy, so it is easier to be detonated.

Keywords

• power machinery and engineering
• critical initiation energy
• detonation bomb experiment
• direct initiation
• coal particle detonation engine