Regeneration plays a very important role, since an overfilled filter can cause engine damage due to excessively high exhaust back pressure, and the filter itself can break or be destroyed. The products captured by the filter are mainly carbon particles with adsorbed hydrocarbons.
| Pos. | spare part no | Name |
| A | - | Front side with alternating closed cells |
| B | - | Side view showing the exhaust gas flow through the filter and the particulate matter collected in the filter |
| C | - | Back side with alternating closed cells |
DPF uses filtration technology based on a catalytic coated filter. The DPF is made of silicon carbide encased in a steel container, which has excellent thermal shock resistance and thermal conductivity characteristics. The DPF is designed with operational needs in mind to maintain optimum back pressure.
The porous surface of the filter is made up of thousands of small parallel channels arranged longitudinally with respect to the exhaust system. Adjacent channels in the filter are alternately closed at the end. This design forces the exhaust gas to pass through the porous filter walls, which act as a filter medium. Solids too large to pass through the porous surface are collected and stored in the channels.
If the solids that collect on the filter are not removed, the passage of exhaust gases may be obstructed. The particulate matter is removed by a regeneration process in which the particulate matter is burned.
The regeneration process uses NO2 to remove particulate matter from the DPF. NO2 is generated by the catalytic converter before the DPF. The catalytic converter generates temperatures in excess of 250°C (482°F) - the level at which the regeneration process begins.
DPF regeneration is controlled by exhaust gas temperature and DPF. The DPF has a filter surface treated "wash coat", which includes platinum and other active components and is similar to the processing of a catalytic converter. At certain exhaust gas and DPF temperatures "wash coat" activates the combustion of particulate matter in addition to the oxidation of carbon monoxide and hydrocarbons.
Exhaust gas and DPF temperatures are controlled by the DPF software in the ECM. The DPF software monitors DPF load based on driving style, distance traveled, and signals from differential pressure sensors and temperature sensors. When the predetermined level of solids volume is reached, the DPF is actively regenerated. It is carried out in cooperation with the ECM through the regulation of various engine management functions, such as:
- fuel injection
- intake air flow control with throttle
- exhaust gas recirculation
- boost pressure control
The regeneration process is possible thanks to the elasticity of the injection engine "common-rail", which provides precise control of fuel delivery, fuel pressure and injection. These parameters are fundamental to ensure an efficient regeneration process.
Two filters are used for DPF regeneration - active and passive.
Passive regeneration
Passive regeneration does not require special intervention from the engine management system and occurs during normal engine operation. Due to passive regeneration, solid particles deposited in the DPF are slowly converted into carbon dioxide. This process is active when the DPF temperature reaches 250°C (482°F). At high speeds and heavy load on the engine, this process becomes continuous.
During passive regeneration, only part of the particulate matter is converted into carbon dioxide. This is because the chemical reaction process is only effective within the normal operating temperature range of 250°C to 500°C (482°F to 932°F).
Above this temperature range, the efficiency of converting particulate matter to carbon dioxide increases with increasing DPF temperature. These temperatures can only be achieved with an active regeneration process.
Active regeneration
Active regeneration begins when the amount of particulate matter in the DPF reaches a threshold level that is monitored or determined by the DPF control software. The threshold calculation takes into account driving style, distance traveled and backpressure signals from the differential pressure sensor.
As a rule, active regeneration occurs every 725 km, but the frequency of regeneration depends on the driving conditions of the vehicle. For example, when driving a car with a small load in city traffic, active regeneration will occur more often. This is caused by a faster accumulation of particulate matter in the DPF compared to modes where the vehicle is driven at high speed and passive regeneration occurs.
The DPF software contains an odometer that initiates the regeneration and serves to back up the active regeneration. Regeneration is requested based on distance travelled, unless initiated by a backpressure signal from a differential pressure transmitter.
Active DPF regeneration starts when the DPF temperature rises to the particulate combustion temperature. The DPF temperature is increased by increasing the exhaust gas temperature. This is achieved by introducing an additional injection after the pilot and main injection.
The DPF software monitors the signals from the two DPF temperature sensors to determine the DPF temperature. Depending on the DPF temperature, the DPF software will request the ECM to perform one or two post-fuel injection cycles:
- The first after-injection of fuel slows down the combustion inside the cylinder, which increases the exhaust gas temperature.
- The second post-fuel injection occurs later in the power stroke cycle. The fuel partially burns in the cylinder; some of the unburned fuel enters the exhaust system, where it initiates an exothermic reaction in the catalytic converter, further increasing the temperature of the DPF.
The active regeneration process takes approximately 20 minutes. The first phase increases the DPF temperature to 500°C (932°F). The second phase further increases the DPF temperature to 600°C (1112°F), which is the optimum temperature for the combustion of particulate matter. This temperature is maintained for 15-20 minutes for complete combustion of particulate matter in the DPF. The combustion process converts carbon particles into carbon dioxide and water.
The active regeneration temperature of the DPF is carefully controlled by the DPF software to maintain the required temperature of 600°C (1112°F) at the DPF inlet. The temperature control system prevents the turbocharger and catalytic converter from exceeding operating temperature limits. Turbocharger inlet temperature must not exceed 830°C (1526°F), the temperature of the catalytic converter must not exceed 800°C (1472°F), and the outlet temperature must remain below 750°C (1382°F).
During active regeneration, the following processes take place, controlled by the ECM:
- The turbocharger is maintained in the fully open position. This minimizes heat transfer from the exhaust gas to the turbocharger and reduces the exhaust gas flow rate to achieve optimum DPF warm-up. If the driver wishes to increase the torque, if necessary, the turbocharger vanes can be closed.
- The throttle valve closes as this helps increase the exhaust gas temperature and reduces the exhaust gas flow rate, which shortens the time for the DPF to warm up to the optimum temperature.
- The exhaust gas recirculation valve closes (EGR). The use of EGR reduces the exhaust gas temperature and therefore does not achieve the optimum DPF temperature.
If, due to vehicle use and/or driving style, an active regeneration process cannot be performed or it is not possible to regenerate the DPF, the dealer may perform a forced DPF regeneration. This can be done by either driving the vehicle until the engine has warmed up to normal operating temperature and then continuing to drive at a speed of at least 48 km/h for 20 minutes, or by connecting the vehicle to a Land Rover approved diagnostic system that will help Have a professional perform a regeneration procedure to clean the DPF.
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