甲烷掺氢射流火焰自适应超大涡模拟

Very-large eddy simulation of blended methane/hydrogen jet flame

摘要:

掺氢燃烧作为一种新型的燃烧方式在动力装备低碳化方面具有很高的应用潜力。发展并验证掺氢燃烧的高精度数值模拟方法对于深入理解掺氢燃烧过程、开发工程燃烧技术具有重要的意义。针对甲烷/氢气掺混燃烧高速射流的场景特点，发展基于 k-ε 模型的自适应超大涡模拟方法（VLES），进一步结合涡耗散概念（EDC）、增厚燃烧（TF）有限速率燃烧模型及小火焰建表燃烧模型，对掺氢燃烧的高精度湍流燃烧数值模拟方法进行验证；针对两类差异显著的经典掺氢燃烧火焰开展数值模拟研究，并与实验及相关数值模拟结果进行详细对比。结果表明：VLES-EDC 方法可以较为准确地预测甲烷/氢气掺混火焰的强烈非定常燃烧过程，两类燃烧特性下流场、温度场等预测结果精度较高；针对掺氢燃烧，小火焰建表燃烧模型相比于有限速率燃烧模型的预测精度有所降低，不同燃烧场景下的预测精度需要进行针对性地校核。

Abstract:

As a new type of combustion, hydrogen-enriched combustion has high potential for the application of the decarbonization in power equipment. The development and assessment of high-fidelity numerical simulation methods for hydrogen-enriched combustion is of great significance for better understanding of hydrogen-enriched combustion process and the development of engineering technology. In the present study, an adaptive Very-Large Eddy Simulation method (VLES) based on the k-ε model is developed according to the scenario characteristics of methane/hydrogen blended combustion using high-speed jet. On the basis, combining the Eddy Dissipation Concept (EDC), Thickened Flame method (TF), i.e. finite rate combustion model and flamelet tabulated combustion model, a high-fidelity turbulent combustion numerical method for hydrogen-blended combustion is developed and verified in detail. Numerical simulations were carried out for two different types of classical hydrogen-enriched flames, namely the JHC hot coflow jet flame with the low reaction rate MILD combustion, and the Sydney bluff-body stabilized high-speed jet flame HM1 with high reaction rate. The simulation predictions were compared with the available experimental and numerical data. The results show that the developed VLES-EDC method can accurately predict the strong unsteady combustion process of methane/hydrogen blended flames, and the prediction results of velocity, temperature, etc., under the two types of combustion conditions have satisfactory accuracy. For the hydrogen enriched combustion, compared with the finite-rate turbulent combustion model, the prediction accuracy of the flamelet combustion model is reduced, and the prediction accuracy under different combustion scenarios needs to be verified accordingly.