The main noise source of the diesel generator set is generated by the diesel engine, including exhaust noise, mechanical noise and combustion noise, cooling fan and exhaust noise, air inlet noise, generator noise, noise generated by the transmission of foundation vibration, etc.:
1. Exhaust noise. Exhaust noise is a kind of pulsating airflow noise with high temperature and high speed, which is a kind of large energy in the engine noise. Its noise can reach more than 100db, and it is the main part of the total engine noise. The exhaust noise generated by the generator during operation is directly discharged through the simple exhaust pipe (the original exhaust pipe of the generator set), and the noise frequency increases significantly with the increase of air flow speed, which has a serious impact on the lives and work of nearby residents.
2. Mechanical noise and combustion noise. The mechanical noise is mainly caused by the vibration or mutual impact caused by the periodic changes of gas pressure and motion inertia force on the moving parts of the engine during operation. It has. points with far noise propagation and reduced attenuation. Combustion noise is the structural vibration and noise generated during the combustion of diesel fuel.
3. Cooling fan and exhaust noise. The noise of unit fan is composed of vortex noise, rotating noise and mechanical noise. Exhaust noise, air flow noise, fan noise and mechanical noise will spread through the exhaust channel, thus causing noise pollution to the environment.
4. Air inlet noise. The function of the air inlet channel is to ensure the normal operation of the engine and create good heat dissipation conditions for the unit itself. The air inlet channel of the unit must enable the air inlet to enter the machine room smoothly, but at the same time, the mechanical noise and airflow noise of the unit will also radiate outside the machine room through this air inlet channel.
The principle of noise reduction in the diesel generator room is to ensure the ventilation condition of the diesel generator set, that is, without reducing the output power, use efficient sound absorption materials and noise reduction and silencing devices to reduce the noise in the air inlet and exhaust channels and exhaust system, so that the noise emission can meet the standard (85db (a)). Generator noise reduction. The basic method is to start from the sound source and adopt some conventional noise reduction technologies; For example, muffler, sound insulation, sound absorption, vibration isolation, etc. are effective methods.
1. Reduce exhaust noise. The exhaust noise is the main noise source of the unit. Its main point is that the noise level is high, the exhaust speed is fast, and it is difficult to control. The exhaust noise can generally be reduced by 40-60 db (a) by using the impedance type compound muffler made of.
2. Reduce the noise of axial flow fan. When reducing the noise of cooling fan of generator set, two problems must be considered. One is the allowable pressure loss of exhaust channel. The second is the required noise reduction. For the above two points, resistive sheet muffler can be selected.
3. Sound insulation and absorption treatment of machine room and vibration isolation of unit
(1) Sound insulation of machine room. After the exhaust noise and cooling fan noise of the unit are reduced, the main remaining noise sources are diesel engine mechanical noise and combustion noise. The method adopted is to remove all the windows except for the necessary observation windows on the interior wall connected to the observation room. All holes and holes should be tightly sealed. The sound insulation of the brick wall should be 40 db
(a) Above. Fire and sound insulation doors and windows shall be adopted for machine room doors and windows.
(2) , air inlet and exhaust. After the sound insulation treatment of the machine room, the problem of ventilation and heat dissipation in the machine room should be solved. The air inlet shall be set in the same straight line with the generator set and air outlet. The air inlet shall be equipped with a resistive sheet muffler. Since the pressure loss at the air inlet is also within the allowable range, the air inlet and outlet in the machine room can naturally reach a balance, and the ventilation and heat dissipation effect is obvious.
(3) Sound absorption treatment. The five walls in the machine room, except the ground, can be used for sound absorption treatment. Perforated plate resonance sound absorption structure is adopted according to the frequency spectrum of the generator set.
(4) Indoor air exchange. The good sound insulation of the machine room will prevent the air in the machine room from convection when the closed water-cooled generator unit is shut down, and the high temperature in the room cannot be lowered in time. The problem can be solved by using low-noise axial flow fan, coupled with resistive sheet muffler.
(5) Vibration isolation of unit. Before the installation of the generator set, vibration isolation treatment shall be carried out in strict accordance with the relevant data provided by the manufacturer to avoid long-distance transmission of structural sound, and air sound shall be continuously radiated during the transmission, so that the noise level at the plant boundary cannot meet the standard. For the existing generator units that are required to be treated due to exceeding the standard, the vibration condition of the ground near the unit must be measured. If the vibration feeling is obvious, the generator units must be vibration isolated first.
4. Transmission noise of foundation vibration. The strong mechanical vibration of the diesel engine can be transmitted to various places outdoors through the foundation, and then radiated through the ground.
After effectively reducing the noise, in order to make the environment of the machine room more beautiful and practical, usually the wall and the sound absorption layer of the hanging are also decorated with microporous aluminum plastic perforated plates, and the lighting system is reasonably configured.
Shanghai Dongfeng Pump Valve Factory is a marine diesel unit. Guangzhou Haijun marine diesel unit adopts BE-160 pneumatic ball valve. The BE type vibration isolator has low natural frequency, appropriate damping ratio, lateral stiffness higher than vertical stiffness, and is suitable for horizontal, inverted, side hung and other installation forms. When used horizontally, the lateral stability is good.