Browse Publications Technical Papers 2010-01-1530

Acidic Condensation in HP EGR Systems Cooled at Low Temperature Using Diesel and Biodiesel Fuels 2010-01-1530

In order to further reduce NOx emissions in increasing HP EGR cooler performance, several OEMs have decided to use a secondary cooling loop dedicated to bring cold water (around 35°C) to the HP EGR heat exchanger. Nevertheless, strongly cooled EGR gases can condensate in the cooler-producing acidic liquids which can corrode some parts in the loop. It is therefore necessary to define EGR components compatible with such kind of environment and constraints.
Testing was performed on a 2.0-liter EU4 diesel engine, using a large panel of current fuels including neat biodiesels from soybean, rapeseed or palm, as well as low and high sulfur petroleum-based diesels. In order to cover all existing cycle conditions, the HP EGR is cooled from 20°C to 90°C independently from the engine coolant circuit. In the aim to perform a fair comparison among biodiesels and diesels, injection and air mass flow setpoints coming from the serial EU4 calibration were adapted to achieve same torque and similar NOx emissions for all fuels.
As expected, at a constant air mass flow setpoint, a strong EGR cooling allows a noticeable reduction of NOx emissions due to a significant increase of the EGR rate. Volumes and acidity of condensates were measured: as calculated and correlated by means of psychrometric charts, and depending on the calibration, tests show that condensation occurs for gas temperatures below 50°C and represent up to 400 ml/h at 20°C ambient temperature. Condensate acidity is similar for all tested fuels and stays within an acceptable range for products in series.


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