Application of CFD Modeling in Combustion Bowl Assessment of Diesel Engines Using DoE Methodology 2006-01-3330
The current paper describes a methodology for combustion bowl assessment for diesel engines. The methodology is based on the application of Computational Fluid Dynamics (CFD) following a Design of Experiments (DoE) procedure. In this work the 3D CFD simulation was performed by the commercial CFD code AVL-FIRE for different combustion bowls from intake valve closing (IVC) to exhaust valve opening (EVO). The initial conditions (at IVC) and boundary conditions were obtained from 1D simulation. Since the work was concentrated on the spray injection, mixing, combustion as well as bowl aerodynamics only a sector mesh was employed for the calculations. A DoE procedure was also used for this simulation work in order to minimize the number of simulation runs and at the same time maintaining the accuracy required assessing the influences of different bowl geometry, spray and intake air motion parameters. A “Fractional Factorial Res V” design was chosen to cover not only the individual parameter influences but also possible interactions between them. For one basic combustion bowl design configuration this resulted in a total of 9 individual bowl design variants varying the 3 most important geometry parameters, together with the variation of nozzle cone angle and swirl ratio at IVC. This resulted in 16+1 experiments (simulation runs) for one engine operating condition, i.e. C100. An optimal bowl was the outcome of the CFD simulation runs based on the DoE, while IMEP, NOx and emission index (a combination of specific NOx and specific soot) were used as measurable quantities. In addition the simulation was performed for the optimal bowl at two operating points A100 and A25.