Emission Control & After Treatment Systems Flashcards
What are the 4 most harmful emissions are?
CO
NOx
PM
SOx
Smog is the result of?
NOx’s mixed with HC’s in certain environmental conditions
What are the 3 main sources of particulate matter?
Unburnt fuel in the form of carbon
Ash from diesel fuel
Soluble organic fractions or heavy hydrocarbons from fuel and oil
Ultra-low sulphur diesel has a sulphur content of?
0.0015% or 15 PPM
Engine emissions are measured in what?
Grams per horse power hour
EGR is used to reduce what emission?
NOx
EGR Causes an increase in what?
CO
HC
What are the main components of a EGR system?
EGR valve, EGR cooler, Charge air mixer, VDT, EGR piping
EGR valve
Controls the flow of exhaust gases to the intake mixer. two basic types of valves are butterfly and poppet
EGR cooler
Cooler designs are air to water. Gas enters cooler around 700F and leaves at about 200F
Venturi
A specially shaped tube that has a restriction and creates a pressure drop when exhaust gas passes through the restriction. How the ECM measures the flow of EGR gas
Delta P valve
Sensor device that measures the pressure differential across Venturi. Has one sensor on inlet and one on restriction.
How does the turbo push more exhaust through ERG?
By closing the vanes increases the exhaust back-pressure, which creates a higher pressure in exhaust.
EGR flow depends primarily on?
Engine load and temperature
Diesel Oxidation Catalyst (DOC)
A canister placed in series with the exhaust system to purify the exhaust gases. Contains a catalyst the causes a chemical reaction with the exhaust gases. Is a flow through design
What is a catalyst?
A substance that makes a chemical reaction occur faster or at a lower temperature then is normally required
The catalyst material that is ideal for a DOC?
Precious metal elements such a platinum or palladium
The catalytic conversion process allows exhaust contaminants to oxidize at a temperature of?
600 - 700 F
What is converted in the DOC?
HC, CO, O2 come into contact with catalyst and heat, they combine to form CO2 and H2O
Diesel particulate filter (DPF)
Is designed to filter out the exhaust particulates by trapping soot. The ceramic core is made up of a honeycombed shaped, porous substrate.
What is order of exhaust flow for shop test?
Dosing valve DOC DPF Decomposition chamber SCR catalyst AMOX`
What are the two basic levels of regeneration?
Passive
Active
Passive regeneration
Occurs during normal engine operation when the engine exhaust temperatures are above 260C or 500 F. It does not require a hydrocarbon injection
Active regeneration
Requires hydrocarbons (diesel fuel) to be injected into the exhaust stream. The hydrocarbons react with the catalyst in the DOC core to produce heat. Temperature can reach 1100 F or 593 C
What are the 3 ways that active regeneration can be initiated?
The ECM during driving cycle
DPF dash switch - referred to as a parked or stationary regeneration
OEM diagnostic program
What are the two ways that HC’s are injected into the exhaust stream are?
A dosing valve and fuel lines located in the exhaust stream downstream of turbo
Pulsing the engines fuel injectors on the exhaust stroke, only works with HPCR or HEUI