OTMT2015 CH4 - GIAI PHAP XU LY KHI THAI

Automotive and Air pollution Spring Semester 2015-2016 CHAPTER MEASURES FOR EMISSION CONTROL Huynh Thanh Cong Ho Chi Minh City University of Technology Exhaust gas emissions and some control technologies  Exhaust Gas Emissions  Internal Engine Measuring  Exhaust Gas Aftertreatment  Introduction  Oxidation Catalytic Converter  DeNOX Systems  Particulate Filter  Exhaust Gas Aftertreatment Systems Current Discussion  Internal engine measuring  External engine measuring  Internal Engine Measuring 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 Scheme of External Exhaust Gas Recirculation (EGR) EGR Control Valve EGR cooler Exhaust gas Air Main cooler EGR-valve EGR rate &R &R m m x EGR = I = A & & +m &R m m m& m& m& A R I Temperature sensor Trottle flap Main cooler flap [ kg / h ] fresh-air-flow [ kg / h ] EGR flow [ kg / h ] gas flow through the intake-valves (inlet flow) Micro-catalyst Pre-cooler flap Pre-cooler Source: 17 Aachener Kolloquium 2008, Dr M Gruber, Audi AG Influence of EGR Rate on Emissions NOX, ppm PM, µg/s 500 PM NOx 0.4 NOX, ppm HC, ppm C 500 500 HC NOx 400 400 400 0.3 300 300 0.2 200 0.1 100 300 200 100 200 0 10 20 30 40 50 EGR, % 10 20 30 40 50 EGR, % Effect of EGR Ratio on NOX/PM (A) and NOX/HC (B) Emission Trade-Off 1.9 liter, 1200 rpm, 30% load, HPL EGR Source: dieselnet.com 2005 ... 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 Scheme... Influence of Nozzle Hole Number on NOX and PM-Emissions comparison 8- to 7-hole nozzle trade-off 1500/min, part load Audi 4.2l-V8-TDI-engine 7-hole nozzle 8-hole nozzle specific NOX emission [g/kWh]... 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