Diesel Particulate Filter Breakdown and Operational Theory The Diesel Particulate Filter (DPF) is a ceramic filter that has thousands of tiny channels or honeycomb-shaped openings that trap the soot onto the channel walls and prevent the particulate matter (down to 1 micron) from leaving out the tail pipeline. The honeycombed inner structure is covered with a layer of a chemical catalyst that contains percentages of rare-earth elements, usually platinum or palladium.
To decrease the particulate matter or soot from the exhaust, you require to raise the combustion chamber temperature high enough to decrease the PM’s from forming. NOx is formed when the combustion temperature levels surpass 3,200 ° F(1,800 ° C), and the amount of oxide formed depends not only on the temperature, however likewise the length of time the heat is applied. Nevertheless, raising the combustion chamber temperature level greater inadvertently raises the amount of NOx that’s formed. This is even worse for the environment than the soot.
Diesel cars and trucks and trucks manufactured after 2009 must have a DPF, and in some cases, a Selective Drivers Decrease (SCR) system. These elements work together to decrease, and when working properly, get rid of all of the harmful NOx and soot from the exhaust. Less soot blended with the engine oil means less of that gritty carbon forming in the oil galleys and other moving parts.
The downside to all of this is that the DPF needs to be cleaned up frequently. The soot particles attach themselves to the lining of the DPF while the engine is running. At the same time, the filter is slowly clogging with the really particulates that it’s developed to remove from the exhaust. This procedure of cleaning up the DPF is done through a procedure called regrowth. There are numerous different techniques utilized by various producers to clean up the DPF.
Passive Regrowth Passive self-regeneration is entirely transparent to the operator and does not affect the machine’s operation or efficiency. The only indicator when a passive regeneration cycle has actually been triggered is either an exhaust temperature cautioning light indicating the exhaust temperature is higher than normal or a message specifying a regrowth cycle remains in process, or both.
Active Regeneration Active self-regeneration happens when there is not enough heat in the exhaust to transform the PM being collected in the DPF. The active regrowth is self-activated by the PCM based on different inputs.
Stationary (Parked) Regeneration Fixed, or parked, regrowth is the exact same as active regrowth however takes place while the car is not being driven. In some cases, the regeneration is “required” onto the motorist for disregarding an earlier demand to carry out a parked regrowth by causing the automobile to go into limp mode. A lot of times, a warning light or message will tell the chauffeur to pull over and start a parked regeneration.
Fixed (Parked) Regrowth Preventative Measures Due to the high heat produced during the regeneration cycle, when carrying out a parked regrowth or a scan tool-induced regrowth cycle, follow these simple guidelines to prevent any outdoors interference. Stay clear of combustibles and individuals.
Filter Failures Some diesel exhaust filter failures are an outcome of not allowing the regrowth to happen. This will accidentally clog the DPF to the point that replacement is the only choice. Although it can be cleaned to some degree, a portion of functionality is still lost due to the severity of the restriction. Another issue is when it is in regrowth and the excess heat combined with the obstruction triggers the metal case of the DPF to broaden and burst. Which, of course, suggests the only service is to replace the DPF. The DPF needs expert cleansing every 150,000– 250,000 miles or 5000 hours.
Regrowth Monitoring On some lorries, the monitoring is done by way of a pressure sensor that determines the input and output pressures of the DPF. Others use mileage or an engine hour counter. On a lot of cars, there is a method to shut off the regeneration process if you are in a circumstance where raising the exhaust system’s temperature might trigger a fire. Don’t leave it off or permanent damage can be caused to the DPF.
Regeneration Regeneration can just occur when the conditions are within the pre-programmed specs for that motor and producer’s requirements. In general, a lot of regeneration cycles are managed without the chauffeur knowing they are happening. The regrowth procedure happens by raising the temperature of the DPF to around 1,100 ° F( 600 ° C)and adequate oxygen is provided directly to the DPF. Some systems will inject additional fuel into the cylinder on the exhaust stroke which efficiently sends out hot gasses into the oxidation catalyst of the DPF, raising its temperature level sufficiently to trigger the carbon to react with the excess oxygen that was also provided. Other systems depend on a heating element just in front of the DPF to raise the temperature.
The regrowth procedure will continue up until the pressure differential throughout the DPF (input and output) drops to an appropriate level. When the regrowth has actually finished, the lorry will return to its regular idle, and the service light will go back off.
Regrowth Issues arise when succeeding regenerations are deserted, and the soot levels construct to a point where the DPF clogs and can’t be regenerated on its own. In limp mode, the lorry will not run over 5 or 10 miles per hour and will stay that way till it has actually been correctly serviced utilizing a scanner to carry out the regeneration procedure.
This system uses a solution of 32.5% urea and 62.5% denatured water called Diesel Exhaust Fluid (DEF). This blue fluid is included in a different holding tank that is injected into the exhaust. When the urea mixture satisfies the hot exhaust gasses, it breaks down to ammonia (NH3) and CO2.