Reasons for Black Smoke Emission in National IV Electronic Fuel Injection Diesel Vehicles
1 Answers
National IV diesel vehicles emit black smoke due to insufficient compression pressure and oil leakage into the combustion chamber caused by wear of valves, piston rings, and cylinder liners. This alters the normal air-fuel mixture ratio at the end of the compression stroke, leading to fuel combustion under oxygen-deficient conditions. Such combustion process tends to produce carbon deposits, resulting in exhaust gases with heavy black smoke. Below are the detailed explanations: 1. Alteration in Combustion Chamber Shape: The shape of the combustion chamber changes due to manufacturing quality issues or prolonged usage, leading to deteriorated technical conditions. Excessive or insufficient compression clearance, as well as incorrect piston positioning, can modify the combustion chamber's shape and volume, adversely affecting the air-fuel mixture quality and worsening combustion conditions. 2. Poor Injector Performance: Diesel engine exhaust smoke levels are closely related to fuel atomization quality. During the injection process, as each injection cycle nears completion, the injection pressure drops, resulting in poor atomization. The droplet diameter at this stage can be 4-5 times larger than during the main injection phase (volume increases by approximately 100 times). These larger droplets have shorter evaporation and combustion times and encounter lower oxygen concentrations, making them prone to soot formation. Non-atomization, poor atomization, or dripping from the injector prevents proper mixing of fuel with air in the cylinder, leading to incomplete combustion.