汽车专业实用英语 作者 陈晟闽 07-Emissions Control Subsystems.ppt

Objectives Explain why hydrocarbon (HC) emissions are released from an engine’s exhaust. Explain how carbon monoxide (CO) emissions are formed in the combustion chamber. Describe oxygen (O2) emissions in relation to air/fuel ratio. Objectives Describe how carbon dioxide (CO2) is formed in the combustion chamber. Describe how oxides of nitrogen (NOX) are formed in the combustion chamber. Describe the operation of an evaporative control system during the canister purge and non-purge modes. Objectives Explain the purpose of the positive crankcase ventilation system. Describe the operation of the detonation sensor and electronic spark control module. Describe the operation of an exhaust gas recirculation valve. Objectives Explain the design and operation of a positive and negative backpressure EGR valve. Explain the operation of a digital EGR valve. Explain the operation of a linear EGR valve. Objectives Define the purpose of a catalytic converter. Describe the operation of a secondary air injection system. Emission Categories Transitional low-emission vehicle (TLEV) Low-emission vehicle (LEV) Ultra low-emission vehicle (ULEV) Clean fueled vehicle (CFV) Super ultra low-emission vehicle (SULEV) Partial zero emission vehicle (PZEV) Zero emission vehicle (ZEV) Exhaust Gasses Hydrocarbons (HC) Molecules of unburned gasoline Carbon Monoxide (CO) A byproduct of combustion Oxides of nitrogen (NOX) Formed when nitrogen and oxygen molecules combine at high temperature Exhaust Gasses Oxygen Part of the air in the air/fuel mixture Not a pollutant Carbon Dioxide Formed when carbon molecules join with oxygen molecules during combustion process Evaporative Emission System Components Special fuel tank filler Pressure/vacuum-release fuel filler cap Vapour separator in the tank One-way check valve(s) Hoses and tubes Charcoal canister An Evaporative Emissions System Charcoal Canister PCV Operation Idle or deceleration Blowby gasses flow through a small opening in the closed valve. Pa