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Analysis of turbulent transport characteristic in hydrogen diffusion flames using direct numerical simulation
Numerical Heat Transfer, Part A: Applications ( IF 2 ) Pub Date : 2020-07-02 , DOI: 10.1080/10407782.2020.1784678
Jieyu Jiang 1 , Tangqin Wu 2 , Hongxu Li 1 , Meng Sun 1 , Bin Zhang 1
Affiliation  

Abstract Non-premixed hydrogen flame is solved to investigate turbulent transport characteristic using direct numerical simulation with768 computing cores. Local and statistical transport behaviors are observed in nonbuoyant and buoyant flames. The absence of buoyancy results in a simplified flow field which can serve as a “cheaner” test to provide an improved understanding of transport process and assess the numerical models. Results show that a wider flame front and a lateral shift of temperature are observed in nonbuoyant flame, where diffusional transport is dominant to mixing process. While, both diffusion and convection are the principal factors in a buoyant flame, which makes flame wrinkle and results in a thinner flame. Besides, statistical information indicates that both gradient transport and counter-gradient transport are observed in hydrogen non-premixed flames, and a transition from gradient transport to counter-gradient transport is captured. A large pressure gradient associated with thermal expansion is responsible for counter-gradient transport in diffusion-controlled flames. However, convective transport is inferred to promote the occurrence of counter-gradient transport in buoyancy-driven flames. It is worth noting that traditional gradient transport model fails to completely describe the intricate scalar transport behaviors in non-premixed hydrogen flames, whether diffusion-driven or buoyancy-driven flames.

中文翻译:

基于直接数值模拟的氢扩散火焰湍流输运特性分析

摘要 采用768核直接数值模拟求解非预混氢火焰,研究湍流输运特性。在非浮力和浮力火焰中观察到局部和统计传输行为。没有浮力会导致简化的流场,可以作为“更简单”的测试,以提供对运输过程的更好理解和评估数值模型。结果表明,在非浮力火焰中观察到更宽的火焰前沿和温度的横向移动,其中扩散传输对混合过程起主导作用。而扩散和对流是产生浮力火焰的主要因素,它使火焰起皱并导致火焰变细。除了,统计信息表明,在氢非预混火焰中观察到梯度输运和反梯度输运,并捕获了从梯度输运到反梯度输运的转变。与热膨胀相关的大压力梯度是扩散控制火焰中逆梯度传输的原因。然而,推断对流传输促进了浮力驱动火焰中反梯度传输的发生。值得注意的是,传统的梯度输运模型未能完整描述非预混氢火焰中复杂的标量输运行为,无论是扩散驱动的还是浮力驱动的火焰。与热膨胀相关的大压力梯度是扩散控制火焰中逆梯度传输的原因。然而,推断对流传输促进了浮力驱动火焰中反梯度传输的发生。值得注意的是,传统的梯度输运模型未能完整描述非预混氢火焰中复杂的标量输运行为,无论是扩散驱动的还是浮力驱动的火焰。与热膨胀相关的大压力梯度是扩散控制火焰中逆梯度传输的原因。然而,推断对流传输促进了浮力驱动火焰中反梯度传输的发生。值得注意的是,传统的梯度输运模型未能完整描述非预混氢火焰中复杂的标量输运行为,无论是扩散驱动的还是浮力驱动的火焰。
更新日期:2020-07-02
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