So allover the world many countries have introduced strong legislation to prohibit the emission above
certain levels.Vehicle emission standard have been made very stringent during the last few years.US emission
have provided in impetus for the development of hybrid electric and fuel cell vehicles,which are close
to commercial production.In addition to development of alternative energy vehicles ,future challenge for research in IC engines are in the area of exhaust after treatment under lean engine operation ,and in the area
of further improvements in the control of engine breathing and fuel introduction.
Emission from IC engines:
Expected Products : CO2 and H2O
Undesirable Products :CO Unburned HC NOx PM SOx Pb
Major Emission Concerns : SI and CI engine has
different polluting emissions,which are responsible
foe atmospheric pollution.
SI Engines : CO, Unburned HC, NOx, Pb
CI Engines : PM, NOx, Unburned HC, SOx
Unburned HC : Major Concern for SI engines.
Could be as high as 6000 ppm, 1.5% of fuel
Constitutes of fuel itself and partially reacted components.
Causes of Formation : (a) Non-Stoichiometric AF ratios of combustion ,(b) Incomplete combustion, EGR
(c)Crevice volumes (d) Valve Overlap (e)Oil or deposition on combustion chamber wall
Carbon Monoxide (CO) : Major Concern for SI engines.Could be as high as 5% of exhaust volume.
Causes of Formation : Non-Stoichiometric AF ratios of combustion and Incomplete combustion, EGR
Nitrogen Oxides : Major Concern for both SI and CI engines. Could be as high as 2000 ppm
Constitutes of No and NO2
Causes of Formation : High temperature of combustion Availability of excess Oxygen at high temp .
Highest rate at slightly lean mixture (Φ=0.95)
Photo-Chemical Smog :
NO2 + Energy from Sunlight → NO + O → O + O2 → O3 (Ground level)
Particulate Matter (PM) : Major Concern for CI engines, may be in SI engines at high loads. High concentration effects the opacity of exhaust (smoke). Constitutes of Carbon Soot Particle, coated with SO3 and Soluble .Organic Fractions (SOF) of fuel. Average mean diameter – 10 µm (PM 10), 2.5 µm (PM 2.5)
Causes of Formation : (a) Near-Stoichiometric AF ratios of combustion (b) Presence of heavy components in the fuel (c)Richer burning at high loads (d)At higher temperatures : PM decrease but NOX increase.
Sulfur Oxides (SOx) : This is one of the major Concern for CI engines.
Formation : Sulfur in fuel SI (150-600 ppm), CI (5000 ppm-1%) LSD (low sulfur diesel), ULSD (Ultra low sulfur diesel < 50ppm)
Emission Standards :
Emission Standards may vary in different countries. The standards are getting stringent day by day.
EURO stand. CARB stand. FTP stand. EPA stand. Mode stand.
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