沼氣發(fā)電機噪聲來源主要部分

　　Main sources of noise from biogas generators

　　從產(chǎn)生的原因和部位上來分，沼氣發(fā)電機組的噪聲可以包括以下幾部分：1. 排煙噪聲；2 .機械噪聲；3. 燃燒噪聲；4. 冷卻風扇和排風噪聲；5. 進風噪聲；6. 發(fā)電機噪聲。下邊分別就這六部分作一說明。

　　From the causes and locations of generation, the noise of biogas generators can include the following parts: 1 Smoke exhaust noise; 2 . Mechanical noise; 3. Combustion noise; 4. Cooling fan and exhaust noise; 5. Inlet air noise; 6. Generator noise. Below are explanations for each of these six parts.

　　1、排煙噪聲

　　1. Smoke exhaust noise

　　排煙噪聲是一種高溫、高速的脈動性氣流噪聲，是發(fā)動機噪聲中能量大，成分多的部分，比進氣噪聲及機體輻射的機械噪聲要高得多，是發(fā)動機總噪聲中主要的組成部分。它的基頻是發(fā)動機的發(fā)火頻率。排煙噪聲的主要成分有以下幾種：周期性的排煙引起的低頻脈動噪聲、排煙管道內(nèi)的氣柱共振噪聲、汽缸的亥姆霍茲共振噪聲、高速氣流通過氣門間隙及曲折的管道時所產(chǎn)生的噪聲、渦流噪聲以及排煙系統(tǒng)在管內(nèi)壓力波激勵下所產(chǎn)生的再生噪聲等，隨氣流速度增加，噪聲頻率顯著提高。

　　Smoke exhaust noise is a high-temperature, high-speed pulsating airflow noise, which is the high-energy and multi-component part of engine noise. It is much higher than intake noise and mechanical noise radiated by the engine body, and is the main component of the total engine noise. Its fundamental frequency is the firing frequency of the engine. The main components of smoke exhaust noise include low-frequency pulsating noise caused by periodic smoke exhaust, air column resonance noise in the smoke exhaust duct, Helmholtz resonance noise in the cylinder, noise generated by high-speed airflow passing through valve clearances and tortuous ducts, vortex noise, and regenerative noise generated by the smoke exhaust system under pressure wave excitation inside the duct. As the airflow velocity increases, the frequency of the noise significantly increases.

　　2、機械噪聲

　　2. Mechanical noise

　　機械噪聲主要是發(fā)動機各運動部件在運轉(zhuǎn)過程中受氣體壓力和運動慣性力的周期變化所引起的震動或相互沖擊而產(chǎn)生的，其中為嚴重的有以下幾種：活塞曲柄連桿機構(gòu)的噪聲、配氣機構(gòu)的噪聲、傳動齒輪的噪聲、不平衡慣性力引起的機械震動及噪聲。柴油機強烈的機械震動可通過地基遠距離傳播到室外各處，然后再通過地面的輻射形成噪聲。這種結(jié)構(gòu)噪聲傳播遠、衰減小，一旦形成很難隔絕。

　　Mechanical noise is mainly generated by the vibration or mutual impact caused by the periodic changes in gas pressure and motion inertia force of various moving parts of the engine during operation. Among them, the most serious ones are the noise of the piston crank connecting rod mechanism, the noise of the valve train mechanism, the noise of the transmission gear, and the mechanical vibration and noise caused by unbalanced inertia force. The strong mechanical vibration of diesel engines can be transmitted to various places outdoors through the foundation, and then generate noise through the radiation on the ground. This type of structural noise has a long propagation distance and low attenuation, making it difficult to isolate once formed.

　　3、燃燒噪聲

　　3. Combustion noise

　　燃燒噪聲是柴油在燃燒過程中產(chǎn)生的結(jié)構(gòu)震動和噪聲。在汽缸內(nèi)燃燒噪聲聲壓級是很高的，但是，發(fā)動機結(jié)構(gòu)中大多數(shù)零件的剛性較高，其自振頻率多處于中高頻區(qū)域，由于對聲波傳播頻率響應不匹配，因而在低頻段很高的汽缸壓力級峰值不能順利地傳出，而中高頻段的汽缸壓力級則相對易于傳出。

　　Combustion noise refers to the structural vibrations and noise generated during the combustion process of diesel fuel. The sound pressure level of combustion noise inside the cylinder is very high, but most of the components in the engine structure have high rigidity, and their natural frequencies are mostly in the mid to high frequency range. Due to the mismatch in response to the propagation frequency of sound waves, the peak pressure level of the cylinder in the low frequency range cannot be transmitted smoothly, while the cylinder pressure level in the mid to high frequency range is relatively easy to transmit.

　　水庫業(yè)用沼氣發(fā)電機噪聲來源主要部分

　　Main sources of noise for biogas generators used in reservoir industry

　　4、冷卻風扇和排風噪聲

　　4. Cooling fan and exhaust noise

　　機組風扇噪聲是由渦流噪聲和旋轉(zhuǎn)噪聲組成的，旋轉(zhuǎn)噪聲由風扇的葉片切割空氣產(chǎn)生周期性擾動而引起；渦流噪聲是氣流在旋轉(zhuǎn)的葉片截面上分離時，由于氣體的粘性引起的旋渦流，輻射一種非穩(wěn)定的流動噪聲。排風噪聲、氣流噪聲、風扇噪聲、機械噪聲均是通過排風的通道輻射出去的。

　　The noise of the unit fan is composed of eddy current noise and rotational noise. The rotational noise is caused by the periodic disturbance generated by the cutting of air by the blades of the fan; Vortex noise is a non stable flow noise radiated by the vortex flow caused by the viscosity of the gas when the airflow separates on the rotating blade section. Exhaust noise, airflow noise, fan noise, and mechanical noise are all radiated through the exhaust duct.

　　5、進風噪聲

　　5. Inlet air noise

　　沼氣發(fā)電機組在正常工作的時候需要有足夠的新風供應，一方面保證發(fā)動機的正常工作，另一方面要給機組創(chuàng)造良好的散熱條件，否則機組無法保證其使用性能。機組的進風系統(tǒng)基本包括進風通道和發(fā)動機本身的進氣系統(tǒng)，機組的進風通道必須能夠使新風能夠順暢的進入機房，同時機組的機械噪聲、氣流噪聲也可以通過這個進風通道輻射到機房外面。與自然進風的機組相比，采用渦輪增壓方式進氣的機組因為渦輪增壓器的轉(zhuǎn)速高，使得進氣噪聲要明顯高于自然進風的機組。

　　The biogas generator set needs sufficient fresh air supply during normal operation to ensure the normal operation of the engine and create good heat dissipation conditions for the unit. Otherwise, the performance of the unit cannot be guaranteed. The air intake system of the unit basically includes the air intake channel and the engine's own air intake system. The air intake channel of the unit must be able to allow fresh air to enter the machine room smoothly, and the mechanical noise and airflow noise of the unit can also be radiated outside the machine room through this air intake channel. Compared with units with natural air intake, units with turbocharging intake have significantly higher intake noise due to the high speed of the turbocharger.

　　6、發(fā)電機噪聲

　　6. Generator noise

　　發(fā)電機噪聲包括定子和轉(zhuǎn)子之間的磁場脈動引起的電磁噪聲，以及滾動軸承旋轉(zhuǎn)所產(chǎn)生的機械噪聲。 根據(jù)上面對沼氣發(fā)電機組的噪聲分析，一般對于發(fā)電機組的噪聲采用兩種處理方式：機房做降噪或者采用*機組（防音型機組）。機房降噪需要對以上的噪聲產(chǎn)生原因分別做處理，主要有以下方法：機房的進風口和排風口分別做隔音墻，同時風口要錯開，進風通道和排風通道內(nèi)設(shè)置進、排風消聲器，同時設(shè)置進、排風消聲百葉窗，這樣消聲量可以達到40分貝；機房內(nèi)頂部和四周墻上鋪設(shè)吸聲系數(shù)高的吸、隔聲板，主要用來消除室內(nèi)混響，降低機房內(nèi)聲能密度，降低聲源向外輻射的強度；為防止噪聲通過大門向外輻射，可以設(shè)兩極房門，并采用隔聲性能好的雙層隔聲門；排煙管處可以選擇標準9分貝的消聲器或者40分貝的消聲器，可以保證機組排煙噪聲的有效控制。以上的處理同樣可以抑制發(fā)電機的噪聲，通過降噪處理，機房的噪聲可以達到用戶的要求。

　　Generator noise includes electromagnetic noise caused by magnetic field pulsation between the stator and rotor, as well as mechanical noise generated by the rotation of rolling bearings. According to the noise analysis of the biogas generator set above, there are generally two ways to deal with the noise of the generator set: noise reduction in the machine room or the use of * units (soundproof units). The noise reduction in the computer room requires separate treatment of the causes of the above noise, mainly through the following methods: soundproof walls should be installed at the inlet and outlet of the computer room, and the air outlets should be staggered. Inlet and exhaust mufflers should be installed in the inlet and exhaust channels, and inlet and exhaust soundproof louvers should be installed to achieve a noise reduction of 40 decibels; High sound absorption and insulation panels with high sound absorption coefficients are installed on the top and surrounding walls of the computer room, mainly used to eliminate indoor reverberation, reduce the sound energy density inside the computer room, and decrease the intensity of external radiation from the sound source; To prevent noise from radiating outward through the main entrance, two pole doors can be installed and double-layer soundproof doors with good sound insulation performance can be used; Standard 9-decibel or 40 decibel mufflers can be selected at the exhaust pipe to ensure effective control of the unit's exhaust noise. The above processing can also suppress the noise of the generator. Through noise reduction processing, the noise in the computer room can meet the requirements of users.

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