Collaborative Research: NSF/DOE Advanced Combustion Engines: Radiation Heat Transfer and Turbulent Fluctuations in IC Engines - Toward Predictive Models to Enable High Efficiency

CBET-1258613Daniel C.宾夕法尼亚州立大学迈克尔F。ModestUniversity of California-MercedRadiation Heat Transfer在大多数燃烧系统中很重要，因为它们的温度很高。在实际应用中，燃烧通常发生在湍流环境中，其中组分和温度的湍流波动可以显著改变辐射传递速率。这些的重要性？放射性-辐射相互作用？(TRI)越来越多地被认可。忽略辐射和/或TRI的计算模型，或者以过于简化的方式处理它们，可能会对重要的量（包括传热速率，温度和污染物排放）做出不准确的预测。已知在压燃式内燃机中，在燃烧事件期间，辐射造成高达一半的缸内热损失。辐射传输率的精确测定是非常困难的，需要解决一个五维的辐射传输方程，并进一步加剧了强烈的光谱变化的辐射特性。当考虑到与湍流的相互作用时，问题达到了另一个困难程度。因此，迄今为止，发动机中的辐射和TRI很少受到关注。该研究项目的目的是量化辐射和TRI影响压燃式发动机效率和排放特性的程度，并开发可用于发动机燃烧系统开发和设计的预测计算模型。下一代高效率发动机的运行预计将接近稳定运行的极限，即使是对能量平衡的微小扰动也会对系统行为产生很大影响。预计辐射和TRI可能对这种发动机特别重要。为此，先进的多相光谱辐射模型和辐射传输方程求解方法将扩展到代表当前和下一代压燃式发动机的高度瞬态高压燃烧环境。将运用这些模型来确定辐射和/或TRI重要的条件，以及可以安全地忽略它们的条件。拟议项目的成果将包括高压多相系统中辐射传递的新物理模型和数值策略，对实际感兴趣的燃烧环境中辐射和TRI的新物理见解，在全球推进和发电应用中，涉及湍流燃烧过程的能量转换仍然很重要在可预见的未来。这包括道路车辆，已经制定了雄心勃勃的近期发动机效率目标，有可能大幅减少能源和化石燃料的消耗。辐射传热在大多数燃烧系统中是重要的，但由于其极端复杂性而受到相对较少的关注。该项目将提供先进的辐射模型，这些模型将成为开发高效发动机所需的预测计算工具的一部分。所开发的物理见解和模型将与其他先进的燃烧系统，包括燃气轮机燃烧室。

CBET-1258613Daniel C. HaworthThe Pennsylvania State UniversityMichael F. ModestUniversity of California-MercedRadiation heat transfer is important in most combustion systems, by virtue of their high temperatures. In practical applications, combustion usually occurs in a turbulent flow environment, where turbulent fluctuations in composition and temperature can significantly alter the radiative transfer rates. The importance of these ?turbulence-radiation interactions? (TRI) is increasingly being recognized. Computational models that neglect radiation and/or TRI, or that treat them in an over-simplified manner, can give inaccurate predictions of important quantities including heat transfer rates, temperatures, and pollutant emissions. Radiation is known to be responsible for up to half of the in-cylinder heat losses during the combustion event in compression-ignition internal combustion engines. Accurate determination of radiative transfer rates is exceedingly difficult, requiring the solution to a five-dimensional radiative transfer equation, and further exacerbated by strong spectral variations of radiative properties. The problem reaches another level of difficulty when interactions with turbulence are considered. Consequently, radiation and TRI in engines have received little attention to date. The purpose of this research project is to quantify the extent to which radiation and TRI influence the efficiency and emissions characteristics of compression-ignition engines, and to develop predictive computational models that can be used for engine combustion system development and design. Next-generation high-efficiency engines are expected to function close to the limits of stable operation, where even small perturbations to the energy balance can have a large influence on system behavior. It is expected that radiation and TRI may be particularly important for such engines. To this end, advanced multiphase spectral radiation models and radiative transfer equation solution methods will be extended to the highly transient, high-pressure combustion environments that are representative of current and next-generation compression-ignition engines. The models will be exercised to establish conditions where radiation and/or TRI are important, and where they may safely be neglected. Outcomes of the proposed project will include new physical models and numerical strategies for radiative transfer in high-pressure multiphase systems, new physical insight into radiation and TRI in combustion environments of practical interest, and validated models that have been connected to multiple underlying computational fluid dynamics codes.Energy conversion involving turbulent combustion processes will remain important in global propulsion and power generation applications for the foreseeable future. This includes road vehicles, where ambitious near-term engine efficiency targets have been established that have the potential to significantly reduce energy and fossil fuel consumption. Radiation heat transfer is important in most combustion systems, but has received relatively little attention because of its extreme complexity. This project will provide advanced radiation models that will be part of the predictive computational tools that are required to develop high-efficiency engines. The physical insight and models that are developed will be relevant for other advanced combustion systems, including gas-turbine combustors.