According to the way of noise radiation, it can be divided into aerodynamic noise, surface radiation noise, and electromagnetic noise. According to the causes, the surface radiated noise of diesel engines can be divided into combustion noise and mechanical noise. Among them, aerodynamic noise is the main noise source.
1. Aerodynamic noise is caused by the unstable process of gas, that is, the disturbance of gas and the interaction between gas and object. Aerodynamic noise directly radiated to the atmosphere includes intake noise, exhaust noise, and cooling fan noise.
2. Combustion noise and mechanical noise are difficult to distinguish strictly. Generally, the noise radiated by the cylinder head, piston, Lianxuan, crankshaft, and engine body due to pressure fluctuations formed by combustion in the cylinder is called combustion noise. The noise generated by the impact of the piston on the cylinder liner and the mechanical impact and vibration of the moving parts is called mechanical noise. Generally, the combustion noise of direct injection diesel engines is higher than the mechanical noise, while the mechanical noise of non-direct injection diesel engines is higher than the combustion noise. However, the combustion noise of both is higher than the mechanical noise when running at low speed.
3. Electromagnetic noise is generated by the high-speed rotation of the generator rotor in the electromagnetic field.
