Analysis of variable geometry turbine and variable valve timing combined potential in a GTDI engine using 1D simulation

摘要

A combination of modelling and experimental tools is an appropriate approach in engines R&D. A 1D model for a 4 cylinder SI direct injection turbocharged engine has been developed and validated with experimental data from a multicylinder engine test bench. In addition, for 1D model setup, turbocharging system information such as compressor and turbine maps, and WG performance were acquired in specific gas stands. Once the 1D engine model is validated in full and part load conditions, the potential of a variable geometry turbine (VGT) together with variable valve timing (VVT) strategy is explored. VGT model was developed based on extrapolation of original FGT experimental data and background expertise. The analysis was performed using modelling tools since VGT + VVT combination provides many degrees of freedom for an experimental approach, in addition to extremely high exhaust temperatures. Optimal solutions for both steady and transient engine performance were found. Torque gains of 10% were seen at 1500 rpm, and an overall of 5% of gains on the other engine speeds. Pumping losses reduction at part loads leads to a decrease in consumption of 0.2-0.4 l/100km on an average 1400 kg vehicle. The use of a VGT also improves over 1 second to arrive at maximum boost pressure on transient response at lower engine speeds.