Numerical investigation of localised forced ignition of pulverised coal particle-laden mixtures: A Direct Numerical Simulation (DNS) analysis
Numerical investigation of localised forced ignition of pulverised coal particle-laden mixtures: A Direct Numerical Simulation (DNS) analysis
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DOI：
10.1016/j.fuel.2014.12.006
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发表时间：
2015-04
期刊：
影响因子：
7.4
通讯作者：
T. Brosh;D. Patel;D. Wacks;N. Chakraborty
中科院分区：
文献类型：
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作者：
T. Brosh;D. Patel;D. Wacks;N. Chakraborty
本文采用简化化学的三维直接数值模拟方法，分析了单分散煤粉颗粒混合物在挥发性气体燃烧过程中的局部强迫点火问题。将煤颗粒作为点源，用拉格朗日方法进行跟踪。欧拉气体相和拉格朗日粒子相之间的耦合是通过质量、动量、能量和物种守恒方程中适当的源项来实现的。进行了详细的参数分析，以分析颗粒等效ratioΦp（根据颗粒相中可用的初级挥发性燃料总量来定义）、湍流速度的均方根和颗粒直径对燃烧早期阶段的影响。非预混燃烧和预混燃烧两种燃烧模式已经在反应区观察到由局部点火引起的火焰。增加inΦpis被发现对维持燃烧是有害的，而颗粒大小的减小可能对燃烧的程度产生不利影响。已经发现，增加inu“增加了脱挥发燃料与周围空气的混合速率，这虽然有利于维持燃烧，但增加了热气体核的传热速率，从而导致高数值的火焰熄灭”。已经提供了详细的物理解释来解释观察到的影响ofΦp，均方根湍流速度波动u '和颗粒直径对煤颗粒负载混合物在成功的局部强制点火后燃烧的影响。
Localised forced ignition of mono-disperse pulverised coal particle-laden mixtures has been analysed based on three-dimensional Direct Numerical Simulations for the carrier phase with simplified chemistry for the combustion of volatile gases. The coal particles are treated as point sources and tracked in a Lagrangian manner. The coupling between Eulerian gaseous and Lagrangian particulate phases has been achieved by appropriate source terms in the mass, momentum, energy and species conservation equations. A detailed parametric analysis has been carried out to analyse the effects of particle equivalence ratioΦp(which is defined based on the total available primary volatile fuel in the particulate phase), root-mean-square of turbulent velocityu′ and particle diameterdpon the early stages of combustion. Both non-premixed and premixed modes of combustion have been observed in the reaction zone for the flames resulting from localised ignition. An increase inΦpis found to be detrimental for sustaining combustion, whereas a reduction in particle size may adversely affect the extent of burning. It has been found that an increase inu′ increases the rate of mixing of devolatilised fuel with the surrounding air, which, though beneficial for sustaining combustion, increases the heat transfer rate from the hot gas kernel, thus leading to flame extinction for high values ofu′. Detailed physical explanations have been provided to explain the observed effects ofΦp, root-mean-square turbulent velocity fluctuationu′ and particle diameterdpon combustion of coal particle-laden mixtures following successful localised forced ignition.