Noise source analysis and noise control measures of Cummins diesel generator

With the rapid development of society, industrial technology is also constantly improving, followed by industrial noise has more impact on people's living environment. The results show that 70% of the noise sources in Chinese cities are from internal combustion engine. Noise, as a kind of environmental pollution, seriously affects people's lives. Improving noise environment has become an important part of environmental protection, among which diesel generator noise control is one of the aspects we pay attention to. How to control the noise of diesel generator?

Noise source analysis of diesel generator:

Diesel engine noise can be divided into gas power noise and surface radiation noise according to different radiation modes. Gas dynamic noise includes intake noise, exhaust noise and fan noise, and generally presents low and medium frequency characteristics. Surface radiated noise includes combustion noise and mechanical noise.

1. Exhaust noise in the above noise, exhaust noise is the most prominent, exhaust noise is the strongest noise source of diesel engine. For non-supercharged diesel engines, exhaust noise is the strongest, up to 110dB(A) ~ 120dB(A). Exhaust noise mainly comes from the pressure pulsation of the air flow in the exhaust pipe, which produces medium and low frequency noise, and the high frequency eddy current noise when the air flow passes through the exhaust valve section at high speed. Diesel engine speed, power, combustion chamber design, combustion process, exhaust back pressure, exhaust valve flow section and so on have a great impact on exhaust noise.

2. Combustion noise Combustion noise is generated by dynamic load caused by periodic changes of gas pressure in the cylinder and high-frequency vibration caused by shock wave, which increases with the increase of cylinder pressure. This part of the noise is radiated to the outside world through the crank connecting rod mechanism through the cylinder liner, body, cylinder head and other structural parts.

3. Mechanical noise Mechanical noise is mainly caused by the crank piston connecting rod mechanism, gas distribution mechanism, gear mechanism and fuel injection pump and other moving parts and their connecting parts have frequent mechanical impact, stimulate the structure vibration and generate noise. There are mainly as follows:

(1) piston knocking noise: piston knocking on cylinder wall is often the strongest mechanical noise of diesel engine. The main reason for knocking is the gap between the piston and the cylinder liner, and the gas pressure acting on the piston. Diesel engine in each working cycle, the piston repeatedly under the action of lateral thrust, from one side of the cylinder wall to the other side and the piston and cylinder wall impact, and make periodic changes;

(2) In the gear transmission system, the presence of gear meshing clearance, torsional and bending vibration of the crankshaft, as well as the fluctuation of torque of the gear and fuel injection pump, causes the vibration of the above moving parts to produce noise;

(3) Impact caused by torsional vibration and unbalance moment.

Diesel generator noise control measures:

1. The most effective and common method on the existing diesel engine is to improve and optimize the exhaust muffler. It is very important to design a muffler with good muffler performance to reduce the noise of the diesel engine.

2. The existing diesel engine can control and reduce the combustion noise by adjusting the injection timing appropriately, that is, the fuel advance Angle, so as to effectively reduce the noise of the whole diesel engine, which is a simple and feasible noise reduction measure.

3. There are many ways to reduce the mechanical excitation measures, according to the characteristics of different diesel engines, different methods can be taken:

⑴ Reduce the impact of the piston on the cylinder wall.

⑵ Control the gear tooth shape, improve the gear machining accuracy, reduce the gear meshing gap, that is, reduce the energy of the gear meshing collision, so as to reduce the gear meshing transmission noise.

(3) New materials are used, such as engineering plastic gears with high damping.

⑷ The use of torsional vibration damper to reduce the torsional vibration of the crankshaft, reduce the noise generated by torsional vibration. In particular, the press-in rubber shock absorber has the advantages of simple structure, reliable use and good noise reduction effect.

Improving the balance performance of moving parts and reducing torsional vibration is the key to keep low mechanical noise. Diesel generator which will be affected by the visible and the noise factor is various, adopts a kind of single governance measures is difficult to effectively reduce the noise, so by comprehensive used in a variety of technical means, reduce the exhaust noise of diesel generators, combustion noise and mechanical noise, so as to reduce the overall noise in diesel generators, achieve good noise reduction effect.

Jiangsu Meao Power Technology Co., Ltd. is an important manufacturer of diesel generators. The company mainly manufactures and sells diesel generator sets with power of 3-3000kW, mobile power station of 24-600kW, Marine emergency diesel generator set of 24-800kW, gas generator set, heavy oil generator set and all kinds of imported series, special series (trailer, static speaker, mobile lighthouse, container, etc.) diesel generator At the same time, we are engaged in generator set maintenance and after-sale service of generator set accessories.