As the power system of construction machinery, the
diesel engine crane provides the power required for mechanical work. Once it fails, it will affect normal production. Therefore, it is very important to diagnose
diesel engine crane faults by observing the color of exhaust gas.
After the diesel fuel is completely burned, the normal color is generally light gray, and dark gray when the load is heavy. When the diesel engine is working, abnormal phenomena such as black smoke, white smoke, and blue smoke may occasionally occur. It is a condition for judging the malfunction of the
diesel engine crane. The analysis is as follows:
(1) Black smoke
Diesel is a complex hydrocarbon. The unburned diesel injected into the combustion chamber is decomposed by high temperature to form carbon black. When exhausted, it is discharged together with the exhaust gas to form black smoke. Black smoke is a manifestation of incomplete fuel combustion in the combustion chamber. The main influencing factors are as follows:
1. Wear of piston rings and cylinder liners
After the piston ring and cylinder liner are worn out, the compression pressure is insufficient, which changes the normal ratio of the mixture at the end of the cylinder compression stroke, which causes the fuel to burn under oxygen-free conditions, resulting in carbon deposits.
2. The injector is not working well
The fuel injector does not atomize or drip, so that the fuel cannot be fully mixed with the air in the cylinder and cannot be fully burned. The black smoke discharge caused by the poor operation of the fuel injector is more obvious when the diesel engine is running at low speed. Because the intake vortex in the cylinder is weak during low-speed operation, the possibility of oil droplets or oil beams being washed away by the airflow is reduced and the residence time is longer, and it is easier to form carbon black and be discharged.
3. The shape of the combustion chamber changes
The manufacturing quality of the shape of the combustion chamber does not meet the technical requirements, the compression gap is too large or small, and the piston position is incorrectly installed, which will change the shape of the combustion chamber, thereby affecting the quality of fuel and air mixing, and worsening the fuel combustion conditions.
4. Improper adjustment of fuel supply advance angle
(1) The fuel supply advance angle is too large, and the fuel is injected into the combustion chamber prematurely. Because the pressure and temperature in the cylinder are low at this time, the fuel cannot ignite and burn. When the piston moves up and the cylinder reaches a certain pressure and temperature, the combustible mixture burns.
(2) The fuel supply advance angle is too small, the fuel injected into the cylinder is too late, and part of the fuel is separated or discharged before it can form a combustible mixture. The fuel discharged with the exhaust gas is decomposed by high temperature to form black smoke.
5. Excessive oil supply
Excessive fuel supply will increase the amount of fuel entering the cylinder, resulting in incomplete fuel combustion due to excess fuel and less gas. In addition, heavy workload, poor fuel quality, and low operating temperature can also cause black smoke from the exhaust.
