Application of Noise Control Technology for Diesel Generators Lin Junming (Shantou Huanhai Engineering Corporation, Shantou 515041) has proved that the scheme design is reasonable and achieves the expected noise reduction effect. The equivalent sound level is less than 60dB(A), nighttime, etc. Effective sound level < 1 Foreword With the continuous development of industrialization and the tertiary industry, the demand for electricity in factories, hotels, hotels, resorts, entertainment venues and other units has increased greatly, resulting in tight power supply and insufficient power supply to the grid. Therefore, many units often bring their own diesel generator sets to alleviate the current situation of insufficient power supply. The resulting noise hazard and exhaust gas pollution problems interfere with people's daily life, affect work efficiency, damage human health, and cause serious pollution to the social environment in a wide range. To this end, the author has adopted comprehensive treatment programs such as sound insulation, noise reduction, vibration reduction, ventilation and heat dissipation in recent years. Through the treatment of diesel engines of several units such as Shantou and Chaoyang, the treatment effect is satisfactory, reaching the second-class hybrid of national urban areas. The standard value of the district.
2 Diesel generator set noise overview and management ideas Diesel generator set noise mainly includes engine exhaust noise, intake noise, combustion noise, connecting rods and pistons, gears and other moving parts during the work of reciprocating high-speed movement and impact of the machinery Noise, cooling water exhaust fan airflow noise. The integrated noise of diesel generator sets is very high, generally up to 100 depending on the power level. In general, noise control actually controls the noise source, the propagation path and the noise to the receiver to achieve the allowable noise. However, it is not easy to control the noise source to reduce the noise. It is limited by the technical conditions, so the sound reduction measures can only be taken in the sound transmission path.
The sound absorption in the machine room is fully covered. The ceiling sound absorption ceiling is made of 50mm thick ultra-fine glass wool (weight: 25kg/m3) felt outer glass cloth, and the galvanized keel is used as the support and perforated aluminum plate (perforation rate 23% ― 25% of the plate thickness is 0.6mm and then a layer of thin paper is used as the support and finish; the wall sound absorption finish is the same as above; the sound absorption and noise reduction of the whole machine room reaches 5-10dB(A), which effectively Radiated noise is controlled in the equipment room, which also reduces noise in the equipment room.
3.2 Vibration isolation and vibration reduction of the base Because the diesel generator has a high speed (most speeds n=1000 or 15001/min), the vibration is large, so consider the vibration isolation and noise reduction measures. The vibration isolation efficiency n can be determined by: where:: a transmission ratio; frequency ratio; - diesel generator operating frequency, / = the natural frequency of a vibration isolation system, using a coil spring damper or a V-type rubber damper, The natural frequency /0 is 40-8. According to the above formula, the number of coil spring dampers or V-type rubber dampers is selected by the load of diesel generators, at least 4, and added in even numbers. Generally choose 6 or 8. The actual application proves that the vibration isolation effect is between 85% and 95%. Through the above vibration isolation measures, vibration can be effectively prevented from being transmitted to the surroundings through the foundation.
3 exhaust pipe damping, muffling diesel generator exhaust is a high-temperature, high-speed pulsating airflow, its noise characteristics are related to the engine, working volume, cylinder gas pressure and engine load, speed and other factors, Obvious low-frequency broadband noise, the peak sound pressure level is in the range of 63-250Hz, but the medium-high frequency also reaches 100-110dB (A). For its high temperature and high speed characteristics, the exhaust pipe of the diesel generator is firstly isolated by a stainless steel bellows to avoid the vibration of the diesel generator passing through the exhaust pipe to the surroundings; then two mufflers are connected, one for the diesel generator itself. The self-contained muffler and the other are the inner-tube type muffler. The design parameters are: according to the exhaust pipe diameter of the diesel generator, the external exhaust pipe diameter is selected, and the air flow speed in the exhaust pipe is controlled within 35-45 m/s, and the muffler is expanded. Compared with m between 9 and 16, the high-power diesel generator has a large displacement, and the expansion ratio is selected to be m=9; the noise in the range of 63-500 Hz for low-power diesel can achieve 35-40dB (A). It effectively prevents noise from propagating from the exhaust pipe to the outside.
3.4 Installation of exhaust airflow fan, exhaust system Insulation Diesel generator set is a kind of power equipment with large heat generation, which is often controlled by noise, poorly solved by ventilation and heat dissipation, affecting the operation of diesel generator rated power, even Caused downtime, resulting in failure of noise management. In order to ensure that the temperature of the equipment room is controlled within the working environment temperature of the diesel generator, natural air intake and forced air exhausting measures are taken to timely dissipate the heat dissipated during the operation of the diesel generator while continuously replenishing fresh cold air. The heat dissipation on the surface of the unit is solved by installing the axial fan to force the exhaust. Generally, according to the size of the machine room, one or two 5-axis flow fans with a capacity of 70009000m3/h are selected, which can not only enhance the heat dissipation during the operation of the unit. In addition, the unit can be ventilated when the unit is stopped; the heat dissipation in the unit is forced out of the machine room through the air duct through its own cooling fan. In addition, the entire exhaust system, including the exhaust pipe and exhaust muffler, is insulated. The bottom layer of the system is wrapped with 5mm thick aluminum silicate cotton felt, and then two layers of 25mm thick ultra-fine glass wool, glass cloth, 0.5mm thick. Through the above methods, the aluminum plate effectively prevents noise from propagating through the exhaust pipe to the outside, and at the same time, the heat of the diesel generator exhaust pipe wall is not diffused into the machine room, reducing the heat source area and improving the room temperature environment of the machine room.
5Installing the inlet, exhaust and muffler, and the muffling elbow, due to the natural air intake and forced exhaust, create holes in the inlet and exhaust vents, resulting in leakage. In order to prevent noise from propagating outward from the inlet and exhaust ducts, a muffler must be installed at both the inlet and outlet ducts.
The input and exhaust air adopts an impedance composite chip muffler. For the air inlet and the exhaust fan of the diesel generator set, a 240mm thick brick muffler housing is used at the tuyere, the top is a reinforced concrete cover, and the inner muffler is double-layered with 0.6mm thick perforated galvanized steel sheets ( Perforation rate 23% 25%, aperture Y3mm) interlayer hollow 100120, filled with ultra-fine glass wool, and wrapped with glass cloth, the net spacing between the muffler pieces is 100mm, the length of the muffler is 20002400mm, and the wind speed is controlled within 45m/s; The flow fan, muffler and muffler elbow shell are made of 1.5mm thick steel plate, 50mm thick superfine glass wool is attached around the inner wall, and the glass cloth is wrapped, and then fixed by 0.6mm thick perforated galvanized steel plate. The middle muffler of the muffler is the same as above. As mentioned, the silencer elbow does not add silencer inside, the wind speed is controlled in 3.6 other diesel engine cooling water cooling fan water tank and air guide box, exhaust air flow fan and muffler connection using canvas as soft interface, wide generator exhaust Small selection expansion ratio elimination m degree is g50250 exhaust airflow fan support hanger pad damping pad equivalent sound level: dB(A) project Junhua Hotel 1750kW Waima Post and Telecommunications Building 1120kW Chaoyang Mobile Communication 640kW Huadu Entertainment City 450kW daytime nighttime nighttime daytime nighttime nighttime spacing diesel generator 1m at the exhaust vent boundary background facing the air inlet boundary background left side border background right side border background diesel exhaust pipe wear When passing through the wall of the machine room, the wall bushing must be installed and led to the roof top of the building, and sprayed through the spray tank with water. The wall around the machine room and the air duct in the machine room must be densely built, and no holes should be left. When the pipe passing through the machine room passes through the wall, the gap must be filled to prevent leakage.
4 Planar layout diesel engine room is generally built on the ground floor. In the process layout and noise control process, considering the full use of space and the convenience of maintenance, the intake and exhaust positions are generally set at the front and rear ends of the diesel generator to facilitate the air. Convection, while leaving room for proper maintenance.
5 Governance effect and conclusion After several units adopted the above governance plan, the environmental monitoring department monitored all units, and the treatment effect was satisfactory. It reached the national standard value category of urban mixed areas and passed the acceptance test.
The monitoring results are shown in Table 1. The comprehensive treatment measures such as sound insulation, noise reduction, vibration reduction, ventilation and heat dissipation are applied to the noise control of different power and various types of diesel generator sets. Practice has proved that the operation effect is good, the heat dissipation is fast, and the cooling water temperature is Constant, indoor and outdoor environmental temperature difference is small, the average noise reduction amount reaches 50-55dB (A), and achieved satisfactory economic, environmental and social benefits.
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