Yongdaxing Electromechanical Equipment: Noise Treatment Methods of Diesel Generator Sets-24 hours free consultation hotline Li Sheng → 400-6088-009-13902465009]QQ:406256032

 

Abstract: Introduce an example of noise improvement project of high-power diesel generator in a narrow space. Through the transformation of the original machine room, sound insulation, sound absorption, ventilation and other measures have been added to make the generator noise emission up to the standard.

1 Introduction

IBM is located in Shenzhen Futian Free Trade Zone. There is a Cummins-Aonan DFLC 1 120KW diesel generator set in the company's factory. Originally, the generator noise control project was undertaken by a company in Hong Kong, and the noise value 3m outside the machine room was 62.7dB(A). Because the generator noise has exceeded the standard, the project needs to be renovated to meet the national standard GB3097-93 in the Class II area standard, that is, the noise value during the day is ≤60 dB(A), and the noise value at night is ≤60 dB(A).

2 Noise source

The noise of diesel generator set during operation mainly includes intake and exhaust noise, combustion noise, and mechanical noise generated by moving parts. When the unit is running (no load), the noise value in the engine room (measurement point 1) is 105.2 dB(A), and the noise value is 65.8 dB(A) at a distance of 3m from the exhaust louver after the original treatment (measurement point 2), and 1m outside the plant boundary At (measurement point 3) the noise value is 62.7 dB(A).

The path of noise inside and outside the engine room is at the air inlet of the engine room, the air outlet of the unit, the exhaust pipe, and the engine room door.

Due to the high sound pressure of the noise source and the small area of ​​the machine room, it must be rebuilt on the original basis, which makes it difficult.

3 Original noise control measures

3.1 Sound insulation room

Install the sound insulation room at the generator position, the size is 8.0m×3.0m×3.5m, the sound insulation room uses [10 channel steel as the support, and 100mm thick sound insulation board is applied. The outer wall of the sound insulation board is 1.2mm galvanized sheet. The inner wall is a 0.8mm perforated plate (aperture Φ3, opening rate 20%), the middle filling is 32kg/m3 ultra-fine glass wool, and the concave surface of the channel steel is filled with glass wool.

3.2 Exhaust air and noise

The generator relies on its own fan to exhaust the air, and an AES rectangular muffler is installed in the front of the exhaust room. The size of the muffler is 1.2m×1.1m×0.9m. The muffler is equipped with a muffler sheet thickness of 200mm and a spacing of 100mm. The muffler sheet adopts ultra-fine glass wool structure with galvanized perforated plates on both sides. Nine mufflers of the same size are assembled into a large muffler of 1.2m×3.3m×2.7m. 300mm in front of the muffler are exhaust louvers of the same size.

3.3 Inlet wind noise reduction

Install a natural inlet muffler on the top of the sound insulation room. The muffler is made of the same exhaust muffler, the net muffler length is 1.0m, the cross-sectional size is 3.4m×2.0m, the muffler thickness is 200mm, the spacing is 200mm, the muffler is connected to an unlined 90° muffler elbow, the muffler elbow length is 1.2 m.

3.4 Smoke exhaust and noise reduction

The noise is muffled by the original two residential mufflers of the generator, and the muffled smoke is merged into a Φ450mm smoke pipe and discharged upward from the exhaust louvers.

4 Advantages and disadvantages of original treatment measures

4.1 Advantages

(1) The exhaust air of the generator radiator is directly discharged outwards, without elbows, the resistance loss is about 172Pa, and the power loss is small. P = ερu2/2

Where P — pressure loss;

u — wind speed 6.7 m/s;

ε— drag coefficient, taken as 6.440;

ρ—The density of air, taking 1.2.

(2) Residential muffler is used for exhaust smoke and noise, which has low exhaust back pressure, high generator combustion efficiency and low power loss.

4.2 Disadvantages

(1) The machine room adopts natural air intake, and the air intake area is small (3.4m2). The machine room generates a large negative pressure, which is difficult to meet the combustion and heat dissipation of the generator.

(2) The sound insulation value of the sound insulation room is low, and the seal between the channel steel and the sound insulation board is poor. The noise value at 0.5m outside the sound insulation room (measurement point 4) is 86.3dB(A).

(3) Exhaust air noise is relatively large, and a too short muffler distance causes this problem.

(4) The exhaust noise is large, and the residential muffler can only attenuate the noise value by 25dB(A) at most.

5 Treatment and transformation measures

The reconstruction project must maintain the original computer room structure as much as possible, so the initial reconstruction measures are set as follows:

(1) Increase the thickness of the sound insulation wall of the sound insulation room.

(2) The exhaust air silencing distance is lengthened, and 300mm thick silencing louvers are installed.

(3) Add 300mm thick air inlet noise silencing shutters.

(4) Increase the installation of forced air fans.

(5) Add a three-stage expansion chamber muffler to the smoke exhaust system.

After negotiating with Party A, Party A believed that the noise absorbing shutters had changed the appearance of the computer room, so the noise absorbing shutters for air intake and exhaust could not be installed. After final discussion, the transformation plan is determined as follows:

(1) Increase the thickness of the sound insulation wall of the sound insulation room by 50mm in the two directions near the outer door of the sound insulation room. First install the original sound insulation wall with ∠50 angle iron to make the skeleton, and then fill with 32kg/m3 ultra-fine glass wool, the external panel is 1.2mm galvanized sheet, all joints are sealed with glass glue, and the joints are with the original groove The steel seams are staggered.

(2) The door of the original sound insulation room has poor sound insulation performance. To prevent noise leakage, a felt seal is used between the door room and the door frame.

(3) Due to the short distance of exhaust air and noise reduction, the exhaust room is changed to: a partition wall of 3.3m, 4.3m long and 0.2m high is set 2m away from the generator exhaust outlet, and the generator exhaust air moves upward. After the noise is silenced, it is discharged downward from the original shutter. The main body of the partition wall is 6mm thick steel plate, both sides are covered with 100mm thick 32kg/m3 ultra-fine glass wool, and then 1.2mm thick galvanized perforated board is used as the protective surface. The turning part of the exhaust air is made into an air duct with a larger curvature (the panel of the air duct is a 1.2mm thick galvanized perforated plate, filled with 2kg/m3 ultra-fine glass wool) to minimize the wind resistance and make the exhaust smooth.

(4) Install a forced air fan on the inner side of the machine room, and install a muffler elbow and AES muffler (effective muffler length 1.6m). The inlet air volume is 30000 m3/h, and the wind speed through the muffler is controlled to be ≤6m/s to prevent secondary noise. At the same time, the wind speed through the original natural inlet muffler is reduced to 4.32m/s, and the noise reduction effect will be better than before.

(5) Add a three-stage expansion chamber muffler to the smoke exhaust system, and lead two smoke pipes to the outdoors for discharge to avoid turbulence noise.

(6) Shock absorption measures. Because the base of the original generator was installed with JP rubber shock isolation pads, the damping work was mainly placed on the smoke exhaust pipe and the smoke exhaust muffler. Both the smoke pipe and the muffler were installed on the roof of the sound insulation room with DJ type shock absorber hangers. , To reduce low frequency noise propagation.

6 Conclusion

High-power diesel generator sets have high noise level and large heat generation. Without affecting the power of the set, reducing noise and ventilation and heat dissipation are the key to noise control projects. Through the above measures, we have basically eliminated the noise pollution of the generator set.

When the project was checked and accepted, the municipal environmental protection monitoring station measured 49.8dB(A) at 1m outside the factory boundary at 11:30 in the evening, which reached the national standard GB3097-93 in the Class II area standard, so the noise control and renovation project was successful .

【Contact person: Li Sheng 24-hour free consultation hotline →400-6088-009- 13902465009】QQ:406256032