A numerical study of the effect of nozzle diameter on diesel combustion ignition and flame stabilization

Abstract

The role of nozzle diameter on diesel combustion is studied by performing computational fluid dynamics calculations of Spray A and Spray D from the Engine Combustion Network. These are well-characterized single-hole sprays in a quiescent environment chamber with thermodynamic conditions representative of modern diesel engines. First, the inert spray evolution is described with the inclusion of the concept of mixing trajectories and local residence time into the analysis. Such concepts enable the quantification of the mixing rate, showing that it decreases with the increase in nozzle diameter. In a second step, the reacting spray evolution is studied focusing on the local heat release rate distribution during the auto-ignition sequence and the quasi-steady state. The capability of a well-mixed-based and a flamelet-based combustion model to predict diesel combustion is also assessed. On one hand, results show that turbulence–chemistry interaction has a profound effect on the description of the reacting spray evolution. On the other hand, the mixing rate, characterized in terms of the local residence time, drives the main changes introduced by the increase of the nozzle diameter when comparing Spray A and Spray D.

Large-eddy simulation of n-dodecane spray flame: Effects of nozzle diameters on autoignition at varying ambient temperatures

“…Their results were consistent with experimental observation, which showed no significant effect on IDT across the three D noz at T am of 1000K. Comparison of Spray D and Spray A was carried out in the numerical study by Desantes et al [13]. It was shown that a reduction in D noz promotes faster mixing which shortens the time needed to reach ignitable equivalence ratio, therefore shorter IDT.…”

“…The equivalent diameter is calculated as d eq = D noz ρ f /ρ am , where ρ f denotes the density of fuel. It is also shown in [11,13] that the Z profiles for Spray A and Spray D collapse onto one another in normalized coordinates. It is hence possible to compare the Z fields for Spray A and Spray D against the experimental data for Spray A.…”

“…In addition, mixture fraction (Z) fields of Spray A and Spray D are compared with experimental data in Figure 1b in normalized radial (r * ) and axial (x * ) coordinates. The radial coordinate (r) and axial coordinate (x) are normalized by the equivalent diameter (d eq ) of each nozzle, i.e., r * = r/d eq and x * = x/d eq [11,13]. The equivalent diameter is calculated as d eq = D noz ρ f /ρ am , where ρ f denotes the density of fuel.…”

Effects of direct water injection and injector configurations on performance and emission characteristics of a gasoline direct injection engine: A computational fluid dynamics analysis

“…It generates a grid automatically during runtime at every time step. 34,35 To refine the mesh size, fixed embedding and adaptive mesh refinement (AMR) are used. Fixed embedding refines the grid at specific locations in the computational domain, such as at the location of injectors, spark plug, and intake valve seat, where finer resolution is needed to capture accurate in-cylinder conditions.…”

Engine combustion network special issue

“…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.…”