A multispectral, extinction-based diagnostic for drop sizing in optically dense diesel sprays

Abstract

Diesel sprays present a challenging environment for detailed quantitative measurement of the liquid field, and to date, there have been only a few efforts to characterize drop sizes within the family of Engine Combustion Network (ECN) diesel sprays. Drop sizing diagnostics, including optical microscopy and Ultra-Small Angle X-ray Scattering (USAXS), have been recently demonstrated in Spray A/D ECN activities, but little data exist to validate these results. This work therefore seeks to extend the available ECN data on the liquid phase field and provide a new comparative data set for assessment of previous ECN drop sizing measurements. In particular, this work presents the development of a two-wavelength, line-of-sight extinction measurement to examine liquid volume fraction and the corresponding droplet field in high-pressure fuel sprays. Here, extinction of lasers emitting at 10.6 μm and 0.633 μm are used for the measurement. To enable quantification of the liquid field in optically dense regions of the spray, a transfer function is developed to account for the influence of multiple scattering. The developed diagnostic is then applied to n-dodecane sprays from the ECN Spray A and Spray D injectors at varying fuel rail pressures and atmospheric chamber condition. Overall, the results show a reasonable agreement with droplet sizes measured using USAXS, as well as from more recent measurements using a Scattering-Absorption Measurement Ratio (SAMR) technique also developed in our group. This is particularly the case near the spray periphery, where on average, less than 40% difference in the measured Sauter mean diameter is observed. Nonetheless, an apparent discrepancy is observed between drop sizes from different diagnostics close to the jet centerline (i.e. nearly 100% difference between available data for Spray D injector). Moreover, the presented diagnostic shows an improved capability in the dilute regions of the spray, where x-ray-based diagnostics are generally subject to high noise and low signal sensitivity.

Engine combustion network special issue

“…Going into details of what is included in this special issue, we have 16 new papers [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] covering all aspects of engine combustion network activities. There are 10 papers related to compression ignition engines [23][24][25][26][27][28][29][30][31][32] while there are 6 papers related to gasoline direct injection, [33][34][35][36][37] indicating that the research community is still trying to improve diesel engines even though the bad reputation they are facing lately.…”

“…Going into details of what is included in this special issue, we have 16 new papers 23–37 covering all aspects of engine combustion network activities. There are 10 papers related to compression ignition engines 23–32 while there are 6 papers related to gasoline direct injection, 33–37 indicating that the research community is still trying to improve diesel engines even though the bad reputation they are facing lately. Dividing the papers into experimental or CFD work, we have 5 papers 23–25,33,34 that deal with advance experimental diagnostics while 13 papers deal with CFD, 26–32,35–37 this is also a trend in the research community moving more and more into modeling work.…”

“…There are 10 papers related to compression ignition engines 23–32 while there are 6 papers related to gasoline direct injection, 33–37 indicating that the research community is still trying to improve diesel engines even though the bad reputation they are facing lately. Dividing the papers into experimental or CFD work, we have 5 papers 23–25,33,34 that deal with advance experimental diagnostics while 13 papers deal with CFD, 26–32,35–37 this is also a trend in the research community moving more and more into modeling work. The final division that could be performed is between internal nozzle flow and spray characteristics with 11 papers related to this field, and 5 papers related to combustion around the original n-dodecane Spray A case 6 and some variations.…”

Novel approach for adaptive coefficient tuning for the simulation of evaporating high-speed sprays injected into a high-temperature and high-pressure environment

“…The setup allows a high degree of optical access for advanced experimental diagnostics and well-characterised initial and boundary conditions for simulations, including detailed fuel injector characterisation. 1–3 Their experiments showed the effects of operating conditions like charge pressures, densities, temperatures and injection pressures or fuel injection equipment specifications like nozzle orifice diameter on spray, 4–9 jet, 1,10–13 combustion 12–20 and emission 21–26 characteristics. Siebers 4 outlines the effect of boundary conditions on liquid penetration.…”