Hydrogen may become a substitute for liquid fossil fuels, contributing to greenhouse gas emissions reductions in internal combustion engines. Numerical simulations play a critical role in the advancement of these engines, with laminar flame speed being the main input. Experimental data of hydrogen flame speed at elevated pressures are scarce, due to the instability of the flames. Nonetheless, stable hydrogen flames can be predicted using chemical kinetics models. Moreover, the injection of water into the hydrogen fuelled engine could offer several benefits to engine combustion and emission performance, as it modulates the laminar flame speed within the combustion chamber and this effect has not been completely understood. Currently, no correlation exists to predict the laminar flame speed of hydrogen-air combustion with water addition under lean mixture engine operating conditions. In this study, we have extended the newly developed laminar flame speed correlation of hydrogen-air combustion to account for the effects of water addition under engine relevant conditions by using chemical kinetic laminar flame speed values. The laminar flame speed correlation was derived for pressures from 10 to 70 bar, temperatures from 400 to 800 K, equivalence ratios from 0.35 to 1 and water addition by mole from 0 to 20%. The hydrogen laminar flame speed correlation was expressed using polynomial forms with reduced order and number of terms with optimized values of coefficients. Additionally, a new exponential term was proposed to the power term α of the laminar flame speed correlation to capture the coupled effects of pressure and temperature on laminar flame speeds under engine-relevant lean burn water-diluted operating conditions.

中文翻译：

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高压条件下加水的氢气燃烧贫混合物的新层流火焰速度相关性

氢可能成为液体化石燃料的替代品，有助于减少内燃机中的温室气体排放。数值模拟在这些发动机的进步中发挥着关键作用，层流火焰速度是主要输入。由于火焰不稳定，高压下氢火焰速度的实验数据很少。尽管如此，可以使用化学动力学模型来预测稳定的氢火焰。此外，将水注入氢燃料发动机可以为发动机燃烧和排放性能带来多种好处，因为它可以调节燃烧室内的层流火焰速度，但这种效果尚未完全了解。目前，在稀混合气发动机运行条件下，不存在预测加水的氢-空气燃烧的层流火焰速度的相关性。在这项研究中，我们扩展了新开发的氢气-空气燃烧层流火焰速度相关性，通过使用化学动力学层流火焰速度值来解释发动机相关条件下加水的影响。层流火焰速度相关性是在压力为 10 至 70 bar、温度为 400 至 800 K、当量比为 0.35 至 1 以及加水摩尔量为 0 至 20% 时得出的。氢层流火焰速度相关性使用具有降阶和项数优化系数值的多项式形式来表达。此外，还为层流火焰速度相关性的幂项α提出了一个新的指数项，以捕获在发动机相关的稀薄燃烧水稀释工况下压力和温度对层流火焰速度的耦合影响。