CFD Combustion and Emission Formation Modeling for a HSDI Diesel Engine Using Detailed Chemistry

Abstract

In order to comply with current emissions regulations, a detailed analysis of the combustion and emission formation processes in the Diesel engines accounting for the effect of the main operating parameters is required. The present study is based both on 0D and 3D numerical simulations by compiling 0D chemical kinetics calculations for Diesel oil surrogate combustion and emission (soot, NOx) formation mechanisms to construct a φ-T (equivalence ratio - temperature) parametric map. In this map, the regions of emissions formation are depicted defining a possible optimal path between the regions by placing on the same map the engine operation conditions represented by the computational cells, whose parameters (equivalence ratio and temperature) are calculated by means of 3D engine modelling. Unlike previous approaches based on static parametric φ-T maps to analyze different combustion regimes and emission formations in Diesel engines, the present paper focuses on a construction of dynamic φ-T maps, in which the pressures and the elapsed times were taken in compliance with those calculated in the 3D engine simulations. The 0D chemical kinetics calculations have been performed by the SENKIN code of the Chemkin-2 library. In-cylinder conditions represented by computational cells with known φ and T are predicted using KIVA-3V code. When cells are plotted on the map, they identify the trajectories helping to navigate between the emissions regions by varying hardware and injection parameters. Sub-models of the KIVA-3V, rel. 2 code has been modified including spray atomization, droplet collision and evaporation, accounting for multi-component fuel vapor coupled with the improved versions of the chemistry/turbulence interaction model and new formulation of the combustion kinetics for the diesel oil surrogate (consisting in 70 species participating in 310 reactions). Simulations were performed for the HSDI 1.300 Fiat Diesel engine at optimized engine operating conditions and pilot injections. Finally, numerical results are compared with the experimental data on in-cylinder pressure, Rate of Heat Release, RoHR, and selected species distributions.

Combustion analysis of a light duty diesel engine using oxygen-enriched and humidified combustion air

“…The sub-models implemented into the customized version of the KIVA 3V code are listed in Table 2. These sub-models were previously implemented by the authors in the framework of the KIVA-3V codes and they are fully described in [16][17][18]. Moreover, the customized KIVA-3V code has been already applied by authors to the analysis of some current production Diesel engines and the results of calculations was found in very good agreement with experiments, as reported in [18][19][20].…”

“…Before application in EA combustion analysis, a 3D model of the engine has been built and validated by comparison with a set of available experimental data in terms of engine performance, indicated quantities (in-cylinder pressure traces, Rate of Heat), and pollutant emissions. Details of the engine model and its validation through comparison with experiments are fully reported in [10,18], thus, in the present paper, only a brief description of the model is reported. The computational grid for combustion simulations is a 60° sector grid in order to exploit the axial-symmetry of the combustion chamber and consists of about 70,000 cells at Top Dead Centre (TDC).…”

Advances in The Design of Two-Stroke, High Speed, Compression Ignition Engines

“…In the automobile project, the combustion patterns calculated for the optimized 2-Stroke configuration have been then compared to the features observed in a reference 4-Stroke engine [21], at the same operating conditions (see [20] for details). Figure 12 presents this comparison in terms of Heat Release Rate / Cumulative Heat Release, in-cylinder average pressure, in-cylinder average temperature at 4 different engine speeds.…”

“…For the sake of brevity, only two projects will be analyzed in this document: the former is the 1.05L automobile engine developed by the University of Modena and Reggio Emilia and described in [8], the latter is the aircraft engine of table 2, in both uniflow and loop versions [21,22].…”

“…The authors have applied this methodology in a number of studies [8,[12][13][14][20][21][22][23][24][25], comparing the simulation results to the experiments, whenever possible. CFD simulation was found to be a quite reliable tool, provided that the numerical models are always underpinned by some experimental evidence.…”