Examination of diesel spray combustion in supercritical ambient fluid using large-eddy simulations

Abstract

High-pressure conditions in diesel engines can often surpass the thermodynamic critical limit of the working fluid. Consequently, the injection of fuel at these conditions can lead to complex behaviors that remain only incompletely understood. This study is concerned with investigating the application of a diffuse-interface method in conjunction with a finite-rate chemistry model in large-eddy simulations of diesel spray injection and ignition in a supercritical ambient environment. The presented numerical approach offers the capability of simulating these complex conditions without the need for parameter tuning that is commonly employed in spray-breakup models. Numerical simulations of inert and reacting n-dodecane sprays — under the Engine Combustion Network Spray A and Spray D configurations — are studied, and results are compared with experimental data for liquid/vapor penetration lengths and ignition timing. In addition, parametric studies are performed to identify flow sensitivities arising from the variation in nozzle diameters between both injectors, along with the impact of low-temperature oxidation on ignition in Spray D simulations. Spray A simulations are found to be insensitive to turbulence, and predictions for penetration length and ignition behavior are in good agreement with experiments. In contrast, Spray D predictions for penetration length and ignition delay demonstrated significant sensitivities to in-nozzle turbulence, introducing uncertainty to the predicted results and stipulating the need for quantitative measurements for model evaluation.

Infrasound Radiation From Impulsive Volcanic Eruptions: Nonlinear Aeroacoustic 2D Simulations

“…CharLES X is an unstructured mesh, finite-volume, LES code that is widely used in studies of jet noise and other aeroacoustics applications (Khalighi et al, 2011;Nichols et al, 2012;Hickey & Ihme, 2014;Brès et al, 2016;Ma et al, 2018;Chung et al, 2019;Jaravel et al, 2019;Lyrintzis & Coderoni, 2019;Ma et al, 2019). The code solves the filtered compressible Navier-Stokes equations in fully conservative form:…”

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

“…This finding is of fundamental importance for this work because it justifies the use of the classical sub-models which usually account for surface tension effects and would potentially not be valid for flows entering the ‘transitional mixing’ regime or beyond. Recent attempts of simulations of supercritical flows can be found for example by Chung et al 63…”