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

众所周知，雾化和燃油喷射过程对直喷发动机的燃烧和排放形成有很大的影响。为了加速清洁燃烧和节能燃烧技术的发展，必须开发基于物理和预测的喷雾模型。在这个项目中，我们计划通过比较计算流体动力学（CFD）模型预测的喷雾破碎结果（如液滴大小和数量密度）与定量喷雾测量结果，来评估液体燃料喷雾在发动机相关条件下破碎成更小液滴的物理机制。拟议的工作将促进与Michael Brear？他是澳大利亚墨尔本大学热力学实验室的研究员。Brear博士吗?S实验室在与我们合作这项提议方面具有独特的优势，因为他们擅长燃烧诊断，并将层析重建应用于层流火焰的光学发射测量。本文的目标是利用定量喷雾测量来评估液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。假设在全压缩的缸内条件下，空气动力诱导的不稳定性控制了喷雾破裂和随后的液滴大小。然而，对于早注射或晚注射，我们预计液体湍流诱导的破裂在喷雾破裂和液滴形成中发挥更主要的作用。在此之前，CFD喷雾模拟被用于评估和比较每一种喷雾破碎机制的预测喷雾形态。因此，需要一种可以量化喷雾破裂结果的测量方法，例如液滴大小和数量密度的联合分布，来评估这些破裂理论的物理有效性。在以前的工作中已经表明，液相激光消光和喷雾形态的预测之间存在直接关联，并且已经证明这种测量技术显示了评估初级喷雾破裂模型的希望。在本提案中，将采用二维激光消光测量的层析重建来产生有关局部喷雾结构和不对称性的三维空间信息，以进行鲁棒模型验证。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.