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Why does noise of 4 stroke turbocharger diesel engine sound like a helicopter?

Views: 93     Author: Site Editor     Publish Time: 2020-07-07      Origin: Site

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Why does noise of 4 stroke turbocharger diesel engine sound like a helicopter?

Why does noise of 4 stroke turbocharger diesel engine sound like a helicopter?

The noise of 4 stroke turbocharger diesel engine mainly includes exhaust noise, mechanical noise, combustion noise, cooling fan noise, exhaust noise, inlet noise, generator noise and foundation vibration noise.


Source of diesel engine noise

Mechanical noise: the mechanical noise is mainly caused by the periodic change of gas pressure and inertia force of motion or generated by mutual impact and friction during the operation of each moving part.

Combustion noise: the sound pressure level of structural noise produced by diesel during combustion is often high, but most parts of the engine structure have high rigidity, which natural frequency is mostly in the middle and high frequency area. Because of the mismatching of the frequency response to the sound wave propagation, the peak value of the cylinder pressure stage in the low-frequency segment cannot be transmitted smoothly, while the cylinder pressure stage in the middle and high-frequency segments is relatively easy to be transmitted.

Fan noise: Fan noise is composed of eddy current noise, rotating noise and mechanical noise. Exhaust noise, airflow noise, fan noise and mechanical noise will be transmitted through the exhaust channel. Therefore, in order to ensure the normal operation of the 4 stroke 6 cylinder diesel engine and create good heat dissipation conditions for the generator set itself, the selected scheme should not only effectively reduce the environmental noise, but also organize the air activities in the machine room to meet the air flow required by the operation of the diesel generator set.


Noise management method of diesel generator 

Under the premise of ensuring that the 4 stroke electric starting diesel engine is ventilated and does not reduce the output power, the high-efficiency sound-absorbing material and noise reduction device are used to reduce the noise of the air inlet channel, exhaust channel and exhaust system, so as to make the noise emission reach the national standard of 85dB (a).


Reduce exhaust noise. Exhaust noise is the main noise source of the unit, which is characterized by high noise level, fast exhaust speed and difficult management. The noise can be reduced by 40-60 dB (a) by using a special impedance type compound muffler. Two problems must be considered to reduce the noise of axial flow fan and cooling fan of high speed 6 cylinder diesel engine. One is the allowable pressure loss of exhaust passage. The second is the required noise reduction. In view of the above two points, the resistive chip muffler can be selected.


The air inlet shall be set in a uniform straight line with the high speed 6 cylinder diesel engine generator and the air outlet.The air inlet should be equipped with a resistive chip muffler, because the pressure loss of the air inlet is also within the allowable range, which can make the air volume in and out of the machine room reach a balance and the ventilation and heat dissipation effect is significant. The AC of indoor air and the sound insulation of the machine room will make the air in the machine room not be convective when the closed water-cooled diesel generator unit is shut down and the high temperature in the room cannot be reduced in time. Therefore, the low-noise axial-flow fan can be used with the resistance chip muffler.


Shanghai Kaixun Engine co., ltd. is a comprehensive internal combustion engine enterprise, specializing in the research, development, production and sales of 135 and 138 diesel engines. Welcome customers to consult. Hotline: + 86 021-56788135.

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