EAPSI: Using Tomographic Reconstruction of Liquid-Phase Extinction Measurements to Assess Fuel Spray Breakup Outcomes in Internal Combustion Engines

众所周知，雾化和燃油喷雾过程对直喷式发动机的燃烧和排放形成有很大影响。为了加快清洁燃烧和节油燃烧技术的发展，必须开发基于物理和预测的喷雾模型。在这个项目中，我们计划通过将计算流体动力学(CFD)模型对喷雾分解结果的预测(如液滴大小和数密度)与定量喷雾测量进行比较，来评估液体燃料喷雾在发动机相关条件下分解为更小液滴的物理机制。这项拟议的工作将促进目前和未来与澳大利亚墨尔本大学迈克尔·布里尔·S热力学实验室的合作。S博士的实验室专门从事燃烧诊断，并已将层流火焰的光学发射测量应用到层流火焰的光学发射测量中。拟议工作的目标是使用定量喷雾测量来评估流体动力不稳定性和液体湍流对直喷式内燃机液体燃料喷雾破裂的相对重要性。假设在完全压缩的气缸内条件下，空气动力诱导的不稳定性控制着喷雾的破碎和随后的液滴尺寸。然而，对于早期或晚期喷射，我们预计液体湍流诱导的破碎将在喷雾破碎和液滴形成中发挥更主要的作用。以前，CFD喷雾模拟被用来评估和比较孤立地预测的每种喷雾破碎机制的喷雾形态。因此，需要一种能够量化雾化结果的测量方法，例如液滴大小和数密度的联合分布，以评估这些雾化理论的物理有效性。以前的工作已经表明，液体激光消光的预测与喷雾形态之间存在直接的相关性，并且已经证明，这种测量技术在评估主要的喷雾破碎模型方面是有希望的。在这个方案中，将使用对二维激光消光测量的层析重建来产生关于局部喷雾结构和不对称性的三维空间信息，以用于稳健的模型验证。该NSF EAPSI奖是与澳大利亚科学院合作资助的。

Atomization and fuel spray processes are known to largely impact combustion and emissions formation in direct injection engines. In order to accelerate the development of clean-combusting and fuel-efficient combustion technologies, physically-based and predictive spray models must be developed. In this project, we plan to assess the physical mechanism by which a liquid fuel spray breaks up into smaller droplets under engine-relevant conditions by comparing computational fluid dynamics (CFD) model predictions of spray breakup outcomes, such as droplet size and number density, with quantitative spray measurements. The proposed work will foster current and future collaboration with Dr. Michael Brear?s Thermodynamics Laboratory at the University of Melbourne, Australia. Dr. Brear?s lab is uniquely positioned to collaborate with us on this proposal as they specialize in combustion diagnostics and have applied tomographic reconstruction to optical emission measurements of laminar flames.The goal of the proposed work is to assess the relative importance of hydrodynamic instabilities and liquid turbulence on the breakup of a liquid fuel spray in direct injection internal combustion engines using quantitative spray measurements. It is hypothesized that under in-cylinder conditions at full compression, aerodynamically-induced instabilities govern spray breakup and subsequent droplet sizes. However, for early or late injections, we expect liquid turbulence-induced breakup to play a more dominant role in spray breakup and droplet formation. Previously, CFD spray simulations were employed to evaluate and compare the predicted spray morphology for each of these spray breakup mechanisms in isolation. A measurement that can quantify spray breakup outcomes, such as joint distributions of droplet size and number density, is therefore needed to assess the physical validity of these breakup theories. It has been shown in previous work that there is a direct correlation between predictions in liquid-phase laser extinction and spray morphology, and have demonstrated that this measurement technique shows promise of assessing primary spray breakup models. In this proposal, tomographic reconstruction to 2-D laser extinction measurements will be employed to yield 3-D spatial information regarding local spray structure and asymmetry for robust model validation. This NSF EAPSI award is funded in collaboration with the Australian Academy of Science.