Overseas Travel Grant: Numerical Simulation and Modelling of Turbulent Premixed Flames with Detailed Chemistry

目前，世界上约85%的一次能源来自煤、石油或天然气的燃烧；燃烧要取代燃烧成为发电和运输的主要来源还需要几十年的时间，对飞机来说甚至更长时间。相关排放导致全球气候变化和城市中心空气质量变差，因此通过立法受到越来越严格的监管。替代燃料，特别是生物燃料，具有净减少碳排放的潜力，但也带来了替代挑战。这些问题加上对外国燃料进口的依赖，使能源价格和安全面临脆弱性。因此，迫切需要用于发电和运输的高效低排放燃烧器，能够燃烧传统和/或替代燃料。OTG提案要求资金访问美国的三个机构，以发展四个合作，其中一个是成熟的，三个将是新的。其中两项合作基于计算软件技术(劳伦斯伯克利实验室的戴/贝尔和佐治亚理工学院的梅农)，另外两项合作基于可用于与数值模拟进行比较的实验数据集(密歇根的Driscoll和佐治亚理工学院的Lieuwen)。所有四项合作将导致思想交流，并有助于理解湍流预混火焰，这些火焰可用于开发和验证湍流火焰建模方法，用于发电和运输的高效低排放燃烧设备应用。第一项合作涉及一种新的软件功能，旨在减少从实验数据集得出的模型中的不确定性。其想法是使用并行计算来测试具有不同参数的模型，并自动磨练最佳选择。这一新方法将被应用于一个工程模型，该模型可以用来理解湍流火焰的化学成分，以改进对排放形成的预测。第二个合作涉及能够研究暴露在极端湍流水平下的预混火焰的实验室燃烧器的实验数据集。这将允许对实验数据和计算数据进行直接比较，这些数据将用于改进工程应用中的湍流火焰模型。第三个合作涉及一个软件，该软件采用了一种成熟的建模方法，建议将其应用于高度湍流火焰，以与前两个合作中的建模方法进行比较。第二个软件功能也可以与第一个协作中的软件相结合，然后用于探索另一种特定的方法来弥合长度尺度之间的差距，该方法是通过在实验和工业应用中使用真实长度尺度进行模拟来实现的。第四个协作涉及另一个实验室实验，旨在重现可能严重损害工业燃烧器的火焰不稳定性的条件。同样，这种合作将提供对实验数据的直接访问，这些数据可以用于与数值模拟进行比较。

Currently, about 85\% of the world's primary energy is generated from burning coal, oil or gas; it will be decades before combustion is replaced as the main source of power generation and transport, and even longer for aircraft. The associated emissions are contributing to global climate change and to poor air quality in urban centres, and are therefore subject to increasingly stringent regulations through legislation. Alternative fuels, in particular biofuels, have the potential for net reduction in carbon emissions, but bring alternative challenges. These issues are coupled with a dependence on foreign fuel imports, exposing vulnerabilities to energy prices and security. Consequently, there is a critical need for efficient low-emission combustors for power generation and transport that are capable of burning conventional and/or alternative fuels.This OTG proposal requests funds to visit three institutions in the US to develop four collaborations, one of which is well-established and three will be new. Two of the collaborations are based around computational software technology (Day/Bell at Lawrence Berkeley Lab, and Menon at Georgia Tech), and the other two are based around experimental datasets that can be used for comparison with numerical simulation (Driscoll at Michigan, and Lieuwen at Georgia Tech).All four collaborations will result in an exchange of ideas, and contribute to the understanding of turbulent premixed flames that can be used for development and validation of turbulent-flame modelling approaches for applications in efficient low-emission combustion devices for power generation and transport.The first collaboration involves a new software capability that has been designed to reduce uncertainty in models derived from experimental datasets. The idea is to use parallel computing to test models with different parameters and automatically hone in on the optimal choice. This novel approach will be applied to a engineering model that can be used to understand the chemical composition of turbulent flames to improve the prediction of emission formation.The second collaboration involves an experimental dataset of a laboratory burner capable of investigating premixed flames exposed to extreme levels of turbulence. This will allow for direct comparison of experimental and computation data, which will be used to improve turbulent-flame models for engineering applications.The third collaboration involves a piece of software that takes a well-established modelling approach, which is being proposed to be applied to highly-turbulent flames for comparison with the modelling approach from the first two collaborations. This second software capability can also be coupled with the software from the first collaboration, and then used to explore another particular approach to bridge the gap between length scales that are achievable through simulation with realistic length scales in experiments and industrial applications.The fourth collaboration involves another laboratory experiment designed to recreate the conditions to explore flame instabilities that can severely damage industrial burners. Again, this collaboration will provide direct access to experimental data that can be used for comparison with numerical simulation.