Combined application of CFD modeling and pressure-based combustion diagnostics for the development of a low compression ratio high-performance diesel engine

The simulation activity for the piston bowl development in a low compression ratio (CR) high-performance diesel engine is described, starting from the calibration of a 3-D CFD commercial code by pressure-based combustion diagnostics data. Calibration was made for the baseline engine built by GMPT-E, matching experimental pressure traces and heat release rates derived from these through the diagnostic tool. Measured pollutant emissions were also applied for calibration at this stage. The engine was susceptible to modifications, according to the outcomes of combined simulation and experimental investigations. The validated CFD model was used for the screening of three new piston bowls featuring a reduced compression ratio. The 3-D code has been integrated with a robustly calibrated 1-D hydraulic model for the injection system simulation and with a 1-D fluidynamic tool for modeling engine flow processes external to the cylinder to provide quite accurate boundary conditions. Such an optimization involved the assessment of performance and pollutant formation for the baseline prototype chambers at engine working conditions of partial and full loads, where walls impingement and air utilization are critical, respectively. As simulation result, the bowl-in-piston showing the best compromise between the abovementioned phenomena was selected and will be subjected to further assessment and optimization by testing.