how does a Diesel Particle Filter work in a car engine? Isn’t it pointless if it dumps the “particles” anyway?
In: Engineering
The filter does not “dump” the particles.
When diesel fuel burns in an engine, it doesn’t burn completely, leaving microscopic particles of soot. These particles are hazardous to health when inhaled and are an important cause of lung health problems like asthma, and can also trigger heart attacks. They are also suspected to be a cause long term lung damage and cardiovascular system damage.
The purpose of the filter is to collect the soot particles, but it can’t just dump them out. Thankfully, soot is carbon, which is flammable. If the exhaust gases get hot enough, and there is enough oxygen in the exhaust, then the soot will actually ignite and burn out of the filter.
Filters are usually made with expensive metals like platinum or palladium. When soot touches these metals it becomes easier to ignite. This means that during hard acceleration or hill climbing, that the exhuast will be hot enough to ignite the soot, and the filter becomes self cleaning.
Sometimes, if you only do town driving, the exhaust never gets hot enough to burn off the soot. In this case, the car’s electronics will detune the engine – this will cause the engine to work very hard but run very inefficiently, and produce extremely hot exhuast gas, which will be hot enough to ignite the soot in the filter. This will happen automatically, and usually the car will tell you that it is happening, and warn you not to switch the car off, because otherwise the filter cleaning won’t finish.
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