This paper presents a cylinder pressure-based control (CPBC)
system for conventional diesel combustion with high EGR levels.
Besides the commonly applied heat release estimation, the CPBC
system is extended with a new virtual NOx and PM sensor.
Using available cylinder pressure information, these emissions are
estimated using a physically based combustion model. This opens the
route to advanced On-Board Diagnostics and to optimized fuel
consumption and emissions during all operating conditions.
The potential of closed-loop CA50 and IMEP control is
demonstrated on a multi-cylinder heavy-duty EGR engine. For
uncalibrated injectors and fuel variations, the combustion control
system makes the engine performance robust for the applied
variations and reduces the need for a time-consuming calibration
process. Cylinder balancing is shown to enable auto-calibration of
fuel injectors and to enhance fuel flexibility. For both Biodiesel
and US diesel, the effects on NOx and PM emissions are
partly compensated for by combined CA50 and IMEP control. This can
be further improved by application of (virtual) emission sensors.
Furthermore, it is shown that this combustion controller shows good
transient performance during load changes.
The virtual emission sensor is successfully implemented for
real-time control. For operating conditions with high EGR rates and
varying injection timing, the predictions of the virtual
NOx and PM sensor are compared with measurements.
NOx emission prediction inaccuracy is typically on the
order of 12%, which is comparable to commercially available
sensors. The predicted PM emissions show good qualitative
agreement, but need further improvement for application in DPF
regeneration and PM emission control strategies. Robust emission
control is essential to meet future requirements for On-Board
Diagnostics and In-Use Compliance.