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Emissions in engines
This document discusses different types of emissions from engines, including exhaust and non-exhaust emissions. It describes the key pollutants like unburnt hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), particulate matter, and sulfur dioxide. The document explains the factors that influence emissions formation in spark ignition and compression ignition engines, such as fuel-air mixture, combustion temperature, and engine operating conditions. It also discusses the limitations of hydrocarbons and the processes that lead to HC and CO emissions from spark ignition engines.
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Emissions in engines
- 1. Emissions in engines RampalSingh B.E. (Mechanical), M.Tech (Production Engineering), Thrice GATE Qualified
- 2. Engine emission Exhaust emission UnburntHC Oxides of carbon (CO,CO2) Oxides of nitrogen Oxides of sulpher Particulate/sort/smoke Non exhaust emission Evaporative losses Crankcase blowing
- 3. comnustion • Ideal combustion– CO2 +H2O+N2+O2+SOX • Ideal combustion – CO2 +H2O+N2+O2+SOX + UHC +CO+Csoot+NO+NO2
- 4. Emission from SIEngine • Rich fuel air mixture would have HC and CO since there is insufficient oxygen for complete oxidation • NO and Nox produced at higher temperature • Nox emission depends on combustion temperature and hence highest near stoichiometric condition • Typically max Nox emission happens at slightly lean mixture at this condition cylinder temperature is sufficiently high and excess oxygen also
- 5. What happens intwo stroke engine • Process of scavenging results in unburnt fuel escaping with exhaust • Lubricant (higher molecular weight)with fuel will also undergo incomplete combustion that further add to emission HC Unburnt fuel Partially reacted components
- 6. Limitation with HC •Acts as irritant and oderants • HC reacts with atmospheric gases to form photochemical smog (very harmful) • Higher content can be present in rich mixture, they have less oxygen • Too lean mixture very less fuel to sustain combustion • Process and causes of HC Emission in SI ENGINE
- 7. Incomplete combustion Due to improper mixing Flame quenching(closerto wall it may get quench) Contamination of exhaust gases During expansion of burnt gases P,T Decrease
- 8. 2. Fuel trappedin compression and oil rings • During compression stroke, the fuel air mixture may be forced into crevices, during expansion this may back into cylinder known as reverse blow by effect
- 9. 3. Valve overlap •Two thing fuel air mixture escape by simultaneous opening of inlet and exhaust valve, fuel air mixture may directly flow into exhaust • More severe at idling and low speed
- 10. • 4. leakagepast exhaust valve • 5. absorption by wall deposits and lubrication oil
- 11. CO Emission • Incompletecombustion, not fully oxidized to CO2 • Colorless and odorless gas • Formation happens with rich mixture • CO Is detrimental to engine performance • Lower in CI engine as operates on lean mixture • Represents chemical energy could have been converted into thermal energy
- 12. NOX Emissions • NOand NO2 • At high temperature NOX production occurs, it reacts with 02 to form o3 which harmful for environment • Nox + sun NO +O +Smog and O2+O O3 • BY decreasing temperature NOX Decreases • Trade off between reduced NOX and engine performance
- 13. Particulate • Solid carbonsoot particle contained predominantly in exhaust of CI Engine • Commonly seen as heavy exhaust smoke when vehicle accelerates at higher load
- 14. sulpher • Part offuel • Oxidise to form SO2 and SO3 Which will combine with water to form sulphuric
- 15. Lead • TEL toincrease octane number to reduce knocking