What's new in diesel exhaust after-treatment systems?
Responding to EU regulations to reduce emissions of nitrogen oxides and particulate matter, truck manufacturers have introduced new diesel exhaust after-treatment systems. In some cases, trucks now have a new selective catalytic reduction (SCR) catalyst and AdBlue ® tank positioned in the central-chassis position.
Do diesel aftertreatment systems reduce tailpipe emissions?
While diesel aftertreatment systems could contribute significantly to reduce tailpipe emissions, the design of cleaner diesel combustion system is the ultimate goal of powertrain system providers worldwide. C.S. Hardy, ... D.M. Ainsworth, in Fuel Systems for IC Engines, 2012
What is an after-treatment diesel exhaust fluid quality sensor?
The after-treatment diesel exhaust fluid quality sensor is used to measure the concentration of the after-treatment diesel exhaust fluid in the tank. This sensor essentially measures the quality of the DEF fluid to see if the fluid is not contaminated.
What is Diesel Exhaust Fluid (DEF)?
In the modern diesel exhaust aftertreatment system, diesel exhaust fluid (DEF) solution is injected into the exhaust stream in a spray of tiny droplets. The diameter of these droplets range from 100 to 200 µm. (For reference, a human hair ranges from about 25 to 181 μm in diameter.)
What is after treatment exhaust system?
An aftertreatment system is a method or device for reducing harmful exhaust emissions from internal-combustion engines. In other words, it is a device that cleans exhaust gases to ensure the engines meet emission regulations.
Is DEF part of emissions?
Diesel Exhaust Fluid (DEF) is a solution of urea and water that's injected into the exhaust stream of diesel vehicles to turn NOx gases (harmful emissions) into nitrogen and water. This system is called a Selective Catalytic Reduction (SCR) implemented by vehicle manufacturers to meet EPA emissions standards in 2010.
What emission does DEF reduce?
DEF, a combination of synthetic, vehicle-grade urea, and de-ionized water, are injected into your truck or big equipment's exhaust stream. Here, it breaks down harmful emissions into non-hazardous nitrogen and water, reducing emissions by up to 90%.
How do diesel emissions systems work?
Small quantities of diesel exhaust fluid (DEF) are injected into the exhaust upstream of a catalyst, where it vaporizes and decomposes to form ammonia and carbon dioxide. The ammonia (NH3) is the desired product which in conjunction to the SCR catalyst, converts the NOx to harmless nitrogen (N2) and water (H2O).
Does DEF reduce carbon emissions?
DEF then combines with the NOx gases, setting off a chemical reaction that converts nitrogen oxides into nitrogen, water, and small amounts of CO2. NOx emissions are reduced by an average of 80% through this process. It also reduces CO2 emissions and particulate matter.
Does DEF go through the engine?
It's contained in a reservoir separate from the fuel tank and is metered into the engine's exhaust stream to control certain emissions. Inside the exhaust pipe, the DEF vaporizes and decomposes into ammonia and carbon dioxide.
Where is DEF injected?
Small quantities of diesel exhaust fluid (DEF) are injected into the exhaust upstream of a catalyst, where it vaporizes and decomposes to form ammonia and carbon dioxide. The ammonia (NH3) is the desired product which in conjunction to the SCR catalyst, converts the NOx to harmless nitrogen (N2) and water (H2O). Q.
How do you delete a system DEF?
1:368:14DEF delete... - YouTubeYouTubeStart of suggested clipEnd of suggested clipI had to disconnect that that's the fill tube that goes all the way up by the gas tank or excuse meMoreI had to disconnect that that's the fill tube that goes all the way up by the gas tank or excuse me the fuel tank fill up. And then disconnect.
Can you bypass DEF system?
If you're thinking of bypassing any of your diesel's emission controls, remember that that it's highly illegal and the fines can be steep. The chances of getting caught may be low, but the consequences are costly.
How does diesel after treatment work?
What is an aftertreatment system? It is a series of components that cleans the diesel exhaust emitted by the engine prior to releasing it through the tailpipe to the outside air. Its purpose is to reduce the emission of harmful pollutants into the environment.
Where does DEF fluid come from?
Contrary to popular myth, cow and bat urine and DEF are not a thing. The urea used in the manufacture of DEF is synthetically derived from ammonia and carbon dioxide, and urea production plants are often adjacent to other sites where ammonia is produced, such as coal and natural gas refineries.
What is the sequence of after treatment components that the diesel exhaust passes before exiting the system into the atmosphere?
The DPF comes after the DOC in the exhaust aftertreatment system. The DPF removes most of the particles (more than 99 %) from the exhaust gases. The exhaust gases pass through the filter, which collects particles from the gases. The particles eventually turn into a soot cake.
What is DOC in diesel exhaust?
Instead, diesel exhaust aftertreatment systems reduce pollutants after they have been produced. The exhaust enters the diesel oxidizing catalyst (DOC) where HC and CO emission levels are reduced. This oxidizing process is similar to what occurred in the two-way catalysts on gas-powered cars of the mid-1970s.
How long does def last?
At room temperature, DEF can be stored for two years. Keep it between -12 degrees C and 32 degrees C and it will last at least a year. Let that temperature rise above 32 C and the DEF shelf-life drops.
What is the diameter of a def tank?
To keep someone from putting diesel in the DEF tank, the standard nozzle diameter for dispensing DEF has been designed at 19mm versus the standard diesel fuel nozzle diameter of 22mm. In addition, the cap for the DEF tank is blue to further differentiate it from the diesel tank.
What is EGR in combustion?
They are not preventive systems like exhaust gas recirculation (EGR) which reduces the formation of pollutants during the combustion process, or crankcase ventilation systems which prevent crankcase vapours from reaching the environment. Instead, diesel exhaust aftertreatment systems reduce pollutants after they have been produced.
How is particulate matter reduced?
Some of the particulates are reduced by precise control of fuel mixture, injection timing, and exhaust temperature. But any PM that makes it past everything else hits the diesel particulate filter (DPF). That amazing piece of engineering can remove more than 90% of particulate matter carried in the exhaust gases.
How to terminate service regeneration?
The service regeneration can be terminated by applying the brake pedal, turning it off using the scan tool, or by simply disconnecting the scan tool from the vehicle. Diesel exhaust aftertreatment systems have been a reality for more than a decade.
What is the reaction of DEF?
DEF is the reactant necessary for the functionality of the SCR system.
What is a heavy duty diesel aftertreatment system?
“Heavy duty diesel engine aftertreatment systems were introduced as a solution to aid in reducing both PM and NOx emissions… Generally speaking, the heavy duty diesel engine aftertreatment system has two primary components: the exhaust aftertreatment technology — which includes the diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) — to reduce and mitigate PM; and a select catalytic reduction (SCR) system to reduce NOx emissions.”
What is a DES?
Diesel Emissions Service (DES) began its operations in 2006 as the emissions division of parent company North State Truck Equipment, Inc., which has been serving the heavy duty truck market since 1978. DES was established to help California businesses meet and exceed the strict CARB and EPA emissions regulations placed on diesel trucks. Since 2006, DES has sold and/or installed over 15,000 emission control devices, and is now an industry leader in diesel emissions on the west coast and beyond.
What is CAE in automotive?
CAE (computer assisted engineering) has become a popular tool for development of both the automotive catalyst and the total after-treatment system . This paper reports on using the CAE approach for modeling the DOC (diesel oxidation catalyst) + CSF (catalyzed soot filter) system. Two cases of modeling are shown here. One case is a modeling of DOC pre-cat in which the transient HC (and CO) gas performance is required. In this model, the parameters shown below are used; the random pore model for a gas diffusion, HC adsorption capacity as a function of temperature, HC desorption rate and HC reaction rate. Calculated catalyst performance correlated to the experimental results, thus validating the model. Another case is a modeling of DOC + CSF in which active regeneration of CSF is required. The CSF is used for diesel exhaust soot filtering, and the accumulated soot is periodically combusted to regenerate the CSF. Additional fuel is supplied to the DOC by post injection and/or fuel dosing into the exhaust pipe upstream of DOC and the resulting exotherm provides the heat for soot combustion on the CSF. In this study the uniformity of soot regeneration in the CSF was investigated as a function of fuel supply uniformity to the DOC.
Why is the exhaust gas temperature higher than the gas temperature at the catalyst?
The engine-out exhaust gas temperature is normally higher than the gas temperature at the catalyst because of expansion through the turbocharger turbine and heat loss from the exhaust system. The transient nature of most emission cycles, including cold start, exacerbates the problem.
How does EGR reduce NOx?
However, while these are proven paths to reducing NOx emissions, there are trade-offs associated with each approach. EGR limits combustion temperature by introducing cooled exhaust gas into the intake system, reducing NOx. EGR has the advantage of causing a relatively small change in the amount of ancillary hardware.
What is selective catalytic reduction?
Selective Catalytic Reduction (SCR) is another method, in addition to EGR, to reduce the level of NOx emissions. Rather than engine-out, SCR reduces tailpipe NOx emissions. In the presence of a catalyst, urea turns into ammonia and carbon dioxide, which then reacts with the NOx to create nitrogen and water vapour.
Does running the exhaust system too often increase CO2?
All on-board active systems use extra fuel through burning to heat the DPF, therefore running the cycle too often while keeping the back pressure in the exhaust system low will result in increased fuel consumption and hence increased levels of CO 2.
Is biodiesel a fuel injection system?
In addition, the introduction of bio-diesels is a cause of concern for fuel injection systems. The first generation of bio-diesels based on the esterisation of plant oils are subject to oxidation and deterioration with time.
Does exhaust throttling reduce air-fuel ratio?
Intake or exhaust throttling may reduce air–fuel ratio and increase the exhaust temperature for the aftertreatment system (e.g., DPF regeneration, SCR, LNT). Exhaust throttling generally produces less BSFC penalty than the pre-compressor intake throttling. However, any throttle valves placed in any part of the engine air system increase BSFC significantly, and their use should be avoided or minimized in engine system design. Although all the air control valves can achieve a wide range of controls of exhaust temperature and space velocity by adjusting the air flow rate, only VVA (e.g., early or late IVC, or cylinder deactivation) can achieve them without BSFC penalty. Early EVO and the valve events to obtain internal EGR may also increase the exhaust temperature. The benefit of exhaust temperature increase by VVA is especially important at light loads and during warm-up.
How does Cummins exhaust work?
On the Cummins system, the Diesel Particulate Filter (DPF) collects and oxidizes carbon to remove particulate matter (PM) by more than 90 percent ; The Diesel Oxidation Catalyst (DOC) aids in this process and is also contained within the DPF. The exhaust passes from the turbo through the DOC and enters the DPF. After collecting the particles from the gases in the DOC and DPF, there is still nitric oxide (NO) and nitrogen dioxide (NO2) left in the exhaust. To reduce the NOx levels, a light mist of urea or Diesel Exhaust Fluid (DEF) is injected into the hot exhaust stream in the Decomposition Reactor. The exhaust progresses from the Decomposition Reactor into the Selective Catalyst Reduction (SCR) system. This converts the toxic NOx and urea mixture into harmless nitrogen gas (N2) and water vapor (H2O). This effectively eliminates harmful emissions, resulting in near-zero emissions from the exhaust.
What is the biggest challenge for a technician working on these types of systems?
The biggest challenge for a technician working on these types of systems is the lack in understanding of how these systems work, what components are in these systems and where to start their diagnostic process.