OTMT2015 CH3 - SU HINH THANH KHI THAI DCDT

Automotive and Air pollution Spring Semester 2015-2016 CHAPTER FORMATION OF EXHAUST EMISSION Huynh Thanh Cong Ho Chi Minh City University of Technology Combustion – Exhaust - Emissions H H O H2O - Water Complete 14,7 kg Air Combustion O O N N H C h kg Fuel C O O CO2 – Carbon dioxide O O O2 - Oxygen N N N2 - Nitrogen C Soot -> Particulates C O CO – Carbon monoxide c H C Un-complete Combustion x y HC – Hydro Carbons N O NOx – Nitrogen Oxides N O O Combustion – Exhaust - Emissions Examples Gasoline Diesel N2 - Nitrogen N N H H O H2O - Water C O O CO2 – Carbon dioxide O2 - Oxygen O O 72 % 72 % 8% 8% 20 % 20 % 1% 1% 0,005 % C Soot -> Particulates C O CO – Carbon monoxide 0,258 % 0,025 % HC – Hydrocarbons 0,018 % 0,005 % NOx – Nitrogen Oxides 0,020 % 0,061 % H C x y N O N O O Exhaust Gas Components Diesel Engines Gasoline Engines 14% SO2 7% HC CO2 PM CO2 NOx HC 6% 13% H2O H2O 1% 0,3% O2 N2 CO N2 10% NOx 76% 72% CO (l =1, constant load) (l = 2, constant load) Source: Intern Exhaust Gas and Particualte Emissions Forum, AVL, 2002 untreated emissions in percent by volume pollutants 0,09% nitrogen (N2) 75,2% oxygen (O2) 15,0% carbon monoxide (CO) nitrogen oxides (NOX) nitrogen (N2) 68,8% hydrocarbons (HC) carbon monoxide (CO) sulfate nitrogen oxides (NOX) solids Pariculte Matter (PM) oxygen (O2) 0,8% aldehyde water (H2O) 2,6% carbon dioxide (CO2) 7,1% untreated emissions in percent by weight pollutants 0,9% water (H2O) 8,5% hydrocarbons (HC) carbon dioxide (CO2) 21,0% Source: Diss Th Mayer, Uni Kaiserslautern, 2005 Air to Fuel Ratio N N H H O 14,7 kg Air C O O O O O O N N C C O H C h kg Fuel c Air / Fuel Ratio H C x y N O N O O Air to Fuel Ratio Rich Stoichiometric Lean Stoichiometric (Ideal) Combustion Atoms Fuel Air Exhaust Molecules C H CH4 O2 N2 10 20 80 10 40 CO2 H2O N2 10 20 80 10 O N 40 160 40 20 20 160 For 10 Molecules CH4 we need 20 Molecules O2, which is 100 Molecules Air Lambda = Actual Air / Stoichmioetric Air Phi = Stoichiometric Air / Actual Air N x O C H Concentration Lambda CO Lambda NO x HC Concentration Diesel - Combustion CO Lambda Diesel Engine Diesel - Combustion Air Fuel Ratio Lambda Air Distance Fuel Formation of CO, HC, NOx HC formation HC formation HC formation Engine Modifications – CO  Formation incomplete combustion (e.g because of local or global shortage on oxygen)  Remedy avoidance of rich mixture zones Engine Modifications – HC  Formation - unburned or partly burned fuel - thermal cracking products, also from lube oil - quenching-effect  Remedy - good mixture formation - no extreme lean combustion operation - no extreme rich combustion operation - short piston land - small surface-to-volume ratio of combustion chamber - reduced sac hole volume of nozzle Engine Modifications – NOx  Formation - secondary product of combustion: - high temperatures - oxygen available - long dwell time - NOmax at λ  1,1 (local) - NOX IDI < NOX DI  Remedy - low temperature (local) - short dwell time - late injection - water injection - EGR ... temperatures - oxygen available - long dwell time - NOmax at λ  1,1 (local) - NOX IDI < NOX DI  Remedy - low temperature (local) - short dwell time - late injection - water injection - EGR ... operation - short piston land - small surface-to-volume ratio of combustion chamber - reduced sac hole volume of nozzle Engine Modifications – NOx  Formation - secondary product of combustion: - high... Formation - unburned or partly burned fuel - thermal cracking products, also from lube oil - quenching-effect  Remedy - good mixture formation - no extreme lean combustion operation - no extreme