Three-dimensional simulation and experiment for turbulent combustion system in a high-speed Direct-Injection diesel engine

To analyze exactly the three-dimensional turbulent combustion temperature field in direct-Injection (DI) diesel engine modification in the CFD (computational fluid dynamics)-code (KIVA-3V) is performed. Three coordinate transformations are carried out to deduce temperature equations. The mixture fracture space is used for the first transformation. Multi-step chemistry reactions using steady state assumptions are used in this phase. In order to describe the stability of diffusion flame, the stretched coordinate and instantaneous scalar dissipation rate are introduced and the temperature flame equation is changed as the second coordinate transformation. Lilian´s diffusion flame regime is taken into account and the boundary condition of the temperature flame equation is carried out for the third transformation. Instead of dealing with all the elementary reactions, one single overall reaction is considered to calculate ignition and extinction, which reduces computational cost. Since the shape of 4JB1 piston is not on the axis of symmetry, 360deg was modeled which corresponds x-offset 4 mm and y-offset 1 mm. Besides, schematic of the test bench configuration and engine specification are showed and the measured injection rate profiles corresponding to rail pressures of 600 bar, 800 bar, and 1000 bar are drawn as an important input for the simulation. Finally, cylinder pressures and the corresponding heat release rates with variation of injection timing are compared with experimental data. Spatial temperature distribution pictures at different crank angle are analyzed. It gives the new theory and method to understand the turbulent diffusion combustion temperature field in DI diesel engine.