Why is the noise of diesel generator louder than that of gasoline generator?

Simply put, according to the characteristics of diesel, diesel can't be ignited by electric spark as simple as gasoline, so it is doomed that diesel can only be ignited by compression ignition. In this way, the compression ratio of diesel engine must be set very high, generally around 20.

In gasoline generators, knocking is a fault phenomenon. The so-called deflagration means that the power of combustible gas incineration is opposite to the movement direction of engine piston. Poor knocking will not only cause engine damage, but also increase fuel consumption and make a lot of noise.

In addition to in-cylinder combustion, other tissues of diesel engines will also have more noise, such as the fuel pump of diesel engines. Unlike gasoline engines, gasoline engines are compressed air-fuel mixtures, while diesel engines are compressed pure air in the compression stroke.

In short, there are two sources of diesel engine noise, one is determined by the combustion characteristics in the cylinder, and the other is caused by the oil supply system.

The noise of diesel engine set is a complex sound source composed of many sound sources. According to the radiation mode of noise, it can be divided into aerodynamic noise, surface radiation noise and electromagnetic noise. According to the causes, the surface radiation noise of diesel generator sets can be divided into combustion noise and mechanical noise. Aerodynamic noise is the main noise source of diesel engine group noise

Aerodynamic noise is the noise of diesel generator set due to the unstable process of gas, that is, the disturbance of gas and the interaction between gas and objects. Aerodynamic noise radiated directly into the atmosphere includes intake noise, exhaust noise and cooling fan noise.

2. Electromagnetic noise is the noise of diesel generator set caused by the high-speed rotation of generator rotor in electromagnetic field.

3. It is difficult to strictly distinguish between combustion noise and mechanical noise. Usually, the noise of diesel engine unit is radiated by the pressure fluctuation caused by combustion in the cylinder of diesel engine unit through the cylinder head, piston, connecting shaft and engine body, which is called combustion noise. The noise generated by the impact of the piston on the cylinder liner and the mechanical impact vibration of the moving parts of the diesel engine unit is called mechanical noise. Generally, the combustion noise of direct injection diesel engine is higher than that of mechanical noise, and the mechanical noise of indirect injection diesel engine is higher than that of combustion noise. But at low speed, the combustion noise is higher than the mechanical noise.