Module 1: An Overview of Engine Emissions and Air Pollution
  Lecture 2: Engine Emissions and Air Pollution
 


Historical Overview: Engine and Vehicle Emission Control

Beginning with the identification during early 1950s that  mainly the unburned hydrocarbons and nitrogen oxides emitted by vehicles are responsible for formation of photochemical smog in Los-Angeles region in the US,  the initiatives and milestones in pursuit of vehicle/ engine emission control are given in Table 1.6

Table 1.6

Engine Emission Control – A Historical Perspective

Year
Event and Milestone
1952 Prof A. J. Haagen- Smit of Univ. of California demonstrated that the  photochemical reactions between  unburned hydrocarbons (HC) and nitrogen oxides (NOx) are responsible for smog (brown haze) observed in Los- Angeles basin
1965  The first vehicle exhaust emissions standards were set in California, USA
1968 The exhaust emission standards set for the first time throughout the USA
1970 Vehicle emission standards set in European countries
1974 Exhaust catalytic converters for oxidation of carbon monoxide (CO) and HC were needed in the US for meeting emission targets.   Phasing-out of tetra ethyl lead (TEL), the antiknock additive from gasoline begins to ensure acceptable life of the catalytic converters
1981 Three-way catalytic converters and closed-loop feedback air-fuel ratio control for simultaneous conversion of CO, HC and NOx introduced on production cars
1992 Euro 1 emission standards needing catalytic emission control on gasoline vehicles implemented in Europe
1994 Catalytic emission control for engines under lean mixture operation introduced
1994 US Tier -1 standards needing  reduction in CO by nearly 96%, HC by 97.5% and NOx by 90%
2000-2005 Widespread use of diesel particulate filters and lean de-NOx catalyst systems on heavy duty vehicles
2004 US Tier -2 standards needing  reduction in CO by nearly 98 %, HC by 99% and NOx by 95%