AFTER TREATMENT MODELING TECHNIQUE FOR CI AND SI ENGINE TO CONTROL EMISSIONS BY USING 3WC, DPF, DOC AND SCR USING GT POWER TOOL

• List down for Gasoline vs Diesel engine
• the pollutants
• aftertreatment devices with catalyst materials
• the example files
• Strategies used for reducing tail pipe emissions
• The pollutants:-

Emissions from Petrol vehicles

Emissions from petrol cars have been dramatically reduced by the introduction of catalytic converters, which oxidise pollutants such as CO to less harmful gases such as CO2. When compared to petrol cars without catalysts, catalysts cars have much lower CO, HC and NOx emissions, at the expense of CO2 emissions, which increase due to the oxidation of carbon monoxide to CO2. As a consequence of this, a catalyst car will also use slightly more fuel and become less efficient. However, despite these improvements, petrol cars with catalysts still produce more CO and HC than diesel cars, although exhaust emissions of NOx and particulates are much lower than diesel cars. In fact particulate emissions from petrol cars are so low that they are not routinely measured.

Emissions from the Diesel Vehicles

Diesel fuel contains more energy per litre than petrol and coupled with the fact that engines are more efficient than petrol engines, diesel cars are more efficient to run. Diesel fuel contains no lead and emissions of the regulated pollutants (carbon monoxide, hydrocarbons and nitrogen oxides) are lower than those from petrol cars without catalysts. However , when compared to petrol cars with a catalysts, diesel have higher emissions of NOx and much higher emissions of particulate matter.

Emissions for road vehicles (per vehicle Km)

Vehicles	Carbon monoxide	Hydro-carbons	Oxides of nitrogen	Particulate matter	Carbon dioxide
Petrol car without a catalyst	100	100	100	----	100
Petrol car with catalyst	42	19	23	----	100
Diesel car without a catalyst	2	3	31	100	85

Petrol cars without catalysts have been given a relative value of 100 for comparison

Despite much debate over which car, petrol, or diesel, weighing up the advantages and disadvantages is not easy. For example, diesel cars have been promoted, as they produce less CO and HC on average, when compared to petro cars, and they have greater fuel economy producing less CO2 per Km. However recent health concerns about particulate matter have given diesels a less environmentally-friendly image, as have the higher emissions of nitrogen oxides compared with petrol cars. As a comparison, petrol cars produce virtually no particulate matter, take longer to warm up, produce more carbon dioxide per mile on average, and emissions of the regulated pollutants are higher.

• Aftertreatment devices with catalyst materials:-

SI engine

The three-way catalyst

Another catalytic converter configuration that is extremely important for modern emission control systems is called the three-way catalyst(TWC). It uses a specific catalyst formulation containing platinum, palladium, and rhodium to reduce NOx and oxidize HC and CO all at the same time. It is called three-way because it simultaneously reduces the concentration of all three major undesirable exhaust gases. The TWC uses a specific chemical design to reduce all three major emissions (HC, CO and NOx) by 90%

catalyst materials

• platinum - reduce NOx
• palladium and rhodium - oxidize HC and CO

CI engine

Pollution

1. NOx is in cylinder temprature dependent Controlling by

• EGR
• Electronic fuel injection

2. Soot is solid carbon:- Control air fuel mixing i,e by Swirl, Bowl design and Sufficient air availability by providing Turbocharging

And also we used

• SCR
• DPF
• DOC

• Strategies used for reducing tail pipe emissions:-

The NOx emitted from the engine is steady and there is no problem beacuse we can select the engine based on the NOx requirement But in the real case it is not impossible we are having the dynamic cconditions because of increasing speed decreasing speed in that cases output emissions from the engine is not steady in that case we are injecting the amonia in b/w the SCR and DPF we injecting the amonia as per the emission conditions and we can achive the required emission at the output but we are not able to inject the amonia below the temprature 180 degree otherwise it will deposited.

Tailpipe Emissions:-

The following are some of the tailpipe emissions

• Carbon dioxide (CO2)
• Nitrogen Oxides(NOx)
• Hydrocarbons(HC)
• Sulphur dioxide(SO2)
• Particulate matter(PM)
• Ozone(O3)

Following are the Strategies used for reducing tail pipe emissions:

• Nitrogen Oxides(NOx):-

Process controls typically used to control NOx emissions include Fuel switching and Fuel Denitrification.

NOx reduction mechanisms applied during the combustion process include controlling the rate of the fuel-air mixing, reducing oxygen availability in the initial combustion zone , and reducing peak flame temp. These include:

• Low NOx burners
• Reburn
• Stream injection
• Staged combustion
• Flue gas recirculation
• Low excess air
• Staged overfire air

• Sulphur dioxide(SO2):-

Process controls typically used to control SO2 emissions include:-

• Fuel switching
• Coal Washing
• Coal gasification and liquefaction
• Desulfurization of oil and natural gas
• Fluidized bed combustion

• Particulate matter(PM):-

Process controls typically used to control particulate matter emissions include:-

• Fuel switching
• Coal cleaning
• Good combustion practices

Four classes of control equipment are used to remove PM from gas stream:

• Mechanical collectors such as cyclones
• Electrostatic precipitators
• Fabric filters
• Wet PM scrubbers

• the example files:-

• The below figures shows CI engine aftertreatment

• The below figures shows SI engine aftertreatment

• List down one set of chemical reactions for TWC and SCR from example files :-

TWC:-

SCR:-

• Explore -Example-aftertreatment-DOC-sampara & Bisset and write a detailed report:-

The below figure shows that DOC-SAMPARA & Bisset from CI engine after-treatement

The above set up used in the CI engine after treatment i,e as shown in the below figure

In the above model we have following sub parts:

• Assembly24
• DOC_QS
• DOC_Explicit
• DOC_samp & Biss
• DOC_temp out
• DOC_Manitor_SA

• Assembly24:-

The below figure shows Assembly24

• After expansion process takes place in the engine Exhaust gasses are coming out from the Engine through exhaust valve after that it goes to the after treatement proces under that process we have different steps to reduce emissions i,e DOC,DPF and SCR.
• Now we consider only at the beganing process i,e DOC.
• In the Assembly24 We can sense with the following different elements: CO, CO2, H2, H2O, liqfuel, Massflow, NO, O2, Soot, Temp and vapour fule and than it passes to the DOC_QS.

• DOC_QS:-

• DOC_QS as a honey cone structure as shown in the above figure.

• The DOC is composed of inner layer (substrate layer) and outer layer. The substrate layer divides, into the washcoat and the substrate wall. The exhaust gas goes through the substrate and oxidation reactions occur on the substrate.

• Its having cell density 400 i,e 1*1 inch its having 400 square structure.
• It is having length of 6 inch.

• DOC_samp & Biss:-

This below fig shows the main page og the DOC sampara and bisset

Reactions:-

• In this we adding the different chemical Reactions after it has been connected to the DOC_QS as shown in the above Ckt.

• DOC_Manitor_SA:-

• The DOC_Monitor is connected with the two Elements i,e one temp from the inlet and other Temp from after DOC_QS.
• In the DOC_monitor we find out the difference b/w the inlet and oulet Temp i,e called conversion Efficiency and we do some mathamatics here.
• Afetr all doing above process than it supply to the line DOC through the Temp output.

The DOC is composed of inner layer (substrate layer) and outer layer. The substrate layer divides, into the washcoat and the substrate wall. The exhaust gas goes through the substrate and oxidation reactions occur on the substrate. The thermal dynamic of DOC is very complicated since it has thermal conduction, convection and chemical reactions. Fig below the Schematic diagram of DOC the chemical reactions in DOC are very complex.

The main reactions in DOC include oxidation reactions and hydrocarbon storage, as demonstrated in below table.

And finally in the DOC we reduce the CO and HC. After that DPF as been carried out for further.