The noise of gas generator set is the main noise source of gas generator set. The noise of gas generator set can be divided into aerodynamic noise, combustion noise, mechanical noise, exhaust noise and vibration noise. Aerodynamic noise mainly includes air vibration noise caused by intake, exhaust and fan rotation, which propagates directly into the air. The pressure vibration produced by combustion in cylinder is called combustion noise when it passes through cylinder head, and the noise radiated from cylinder block is called combustion noise. When the unit works, the exhaust gas rushes out of the exhaust valve at high speed, enters the muffler along the exhaust manifold, and finally discharges into the atmosphere from the tail pipe.
Exhaust noise is the biggest noise of the engine, which is usually 15 dB (A) higher than the main engine noise, followed by combustion noise and mechanical noise, fan noise, air intake noise. The original muffler is mainly based on resistive noise elimination, with high power consumption and poor noise elimination effect. After careful demonstration, the three level combined noise reduction technology is used to transform the muffler into a new combined muffler. The main components of the combined muffler are the muffler cavity, the muffler cover, the sound insulation layer and the sound absorption resonance plate. The noise energy of the medium and low frequency sound source can be fully dissipated by the first stage of the Counter-jet noise absorption cavity.
The second-stage porous resistance muffler can eliminate most of the high-frequency noise, increase the muffler's adaptability to high-frequency, and equipped with high-efficiency sound absorbing materials in the cavity, can fully absorb and change the direction of the noise, thereby maximizing the consumption of noise energy. The third stage is an exhaust pipe with resonant plates designed for gas generators, which is further silenced by the vibration of thin sheets. Tests show that the new muffler is superior to the original muffler in terms of muffling capacity, muffling frequency range (mainly the peak frequency range of muffling capacity) and resistance loss.
In addition, the muffler has the advantages of suitable size, good rigidity, convenient installation, and the function of suppressing regeneration noise. Moreover, the sound absorption and insulation layer at the rear has anti-corrosion property, which can effectively overcome the low temperature dew point corrosion of flue gas and prolong the service life of the muffler. Based on the working principle of gas-fired generator set, it is difficult to use the method of reducing the noise of sound source to eliminate noise, so the main way is to effectively block its noise transmission. The core of anechoic technology is to use the natural attenuation law of sound wave to reduce the noise pollution surface. Specific ways to reduce noise include the following: sound absorption, sound insulation and changing the direction of noise propagation. In practical engineering applications, only one of them is often used. In this paper, three methods are adopted and a new combined noise reduction technology is proposed for gas-fired generating units.
An effective way to control mechanical noise and combustion noise is vibration isolation. The gas engine, generator and steel chassis are equipped with composite vibration isolation cushion, and the chassis and foundation are also padded with high-efficiency damping rubber cushion. After two-stage vibration isolation, not only the vibration of the unit is effectively isolated, but also the unit runs more smoothly and the overall noise is significantly reduced. Gas-fired generator unit works in a closed room. Generally speaking, the air intake system includes the air intake channel of gas-fired generator unit and the air intake system of engine. The inlet and exhaust passages are directly connected with the outside world, and the air velocity is very high. The noise of the air flow and the noise of the unit operation are radiated through the inlet passage to the outside. The noise of the engine intake system is caused by the pressure fluctuation caused by the periodic opening and closing of the intake valve, and its noise frequency is generally in the low frequency range below 500 Hz.
Two anechoic inlets are arranged on the wall of the engine room as the air inlet of the engine room and the air inlet of the engine respectively. Due to the negative indoor pressure caused by exhaust air, cold air naturally enters the engine room through the anechoic inlet, and the heat emitted by the body is discharged smoothly. This ensures that there is enough fresh air in the computer room. Fan noise is composed of rotary noise and eddy noise. Rotating noise is caused by periodic disturbance of air flow cutting by rotating fan blades. Eddy current noise is a series of eddies formed by gas slipping or splitting when boundary layer separation occurs on the section of rotating blade, thus radiating an unsteady flow noise. The exhaust duct is directly connected with the outside world, and the air velocity is very high. The airflow noise, fan noise and mechanical noise radiate out through this passage.