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

Magnotti Gina M, Atlanta GA

Investigators

Abstract

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.