噪声处理

　　Noise processing

　　燃气发电机组由燃气发动机、发电机、控制柜等部件组成,燃气发动机与发电机安装在同一个钢制底盘上。机组以天然气、井口伴生气、煤矿瓦斯气、水煤气、炼化尾气、沼气、焦炉煤气、高炉煤气等可燃性气体为燃料,启动迅速,经济性好,特别是由于高质量城市生活的需求,燃气发电机组已广泛应用于电信、邮局、银行、图书馆、医院、宾馆等部门,作为后备电源。最初燃气发电机组是针对矿场工况设计的,机组运行时产生的噪声一般为95~110 dB(A)。GB 3096-93城市区域环境噪声标准对市区的噪声状况进行了严格的规定,对于2类区域(居住、商业、工业混杂区)昼间为60 dB(A),夜间为50dB(A);对于1类区域(居住、文教机关区)昼间为55 dB(A)、夜间为45 dB(A)。机组运行时产生的噪声给城市环境带来了严重的噪声污染,影响了人们的正常工作和生活,也限制了燃气发电机组的广泛应用。本文就是针对燃气发电机组噪声污染问题,提出了一套整改措施,以期降低机组噪声,促进燃气发电机组的推广应用。

　　The gas generator set consists of gas engine, generator, control cabinet and other components. The gas engine and generator are installed on the same steel chassis. The unit is fueled by combustible gases such as natural gas, wellbore associated gas, coal mine gas, water gas, refining tail gas, biogas, coke oven gas, blast furnace gas, etc. It starts quickly and has good economy, especially due to the demand for high-quality urban life. Gas generator sets have been widely used in telecommunications, post offices, banks, libraries, hospitals, hotels and other departments as backup power sources. The initial gas generator set was designed for mining conditions, and the noise generated during operation is generally 95-110 dB (A). The GB 3096-93 Urban Regional Environmental Noise Standard strictly regulates the noise level in urban areas, with a daytime noise level of 60 dB (A) and a nighttime noise level of 50 dB (A) for Class 2 areas (residential, commercial, and industrial mixed areas); For Class 1 areas (residential, cultural and educational institutions), the daytime is 55 dB (A) and the nighttime is 45 dB (A). The noise generated during the operation of the unit has caused serious noise pollution to the urban environment, affecting people's normal work and life, and also limiting the widespread application of gas-fired power generation units. This article proposes a set of rectification measures to address the noise pollution problem of gas-fired power generation units, in order to reduce unit noise and promote the promotion and application of gas-fired power generation units.

　　1.声源分析

　　1. Sound source analysis

　　燃气发动机噪声是燃气发电机组的主要噪声来源,燃气发动机噪声可分为空气动力噪声、燃烧噪声、机械噪声、排气噪声和振动噪声。空气动力噪声主要包括进、排气和风扇旋转引起的空气振动噪声,这部分噪声直接向空气中传播。气缸内燃烧所形成的压力振动通过缸盖，机体向外辐射的噪声叫燃烧噪声;活塞对缸套的撞击,配气机构、喷气系统等运动部件产生的撞击振动噪声统称为机械噪声。机组工作时,废气从排气门高速冲出,沿排气歧管进入消声器,最后从尾管排入大气。排气噪声是发动机的最大噪声,往往比发动机主机噪声高15 dB(A)左右,其次分别是燃烧噪声和机械噪声、风扇噪声、进气噪声。

　　Gas engine noise is the main source of noise for gas generator sets. Gas engine noise 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 directly propagates into the air. The pressure vibration formed by combustion inside the cylinder passes through the cylinder head, and the noise radiated outward from the body is called combustion noise; The impact of the piston on the cylinder liner, as well as the impact vibration noise generated by moving parts such as the valve train and jet system, are collectively referred to as mechanical noise. When the unit is working, exhaust gas rushes out of the exhaust valve at high speed, enters the muffler along the exhaust manifold, and finally is discharged into the atmosphere through the tailpipe. Exhaust noise is the maximum noise of the engine, often about 15 dB (A) higher than the noise of the engine host, followed by combustion noise and mechanical noise, fan noise, and intake noise.

　　2.改造设计

　　2. Renovation design

　　基于燃气发电机组的工作原理,难以用降低声源噪声的方法来消声,所以主要是要有效阻断其噪声传播途径。消声技术的核心就是利用声波在传播中自然衰减的规律去缩小噪声的污染面。具体降低噪声的方法有以下几种:吸声、隔声及改变噪声传播方向。在实际工程应用中往往只用其中一种,本文采用三种方法并用的措施,针对燃气发电机组提出了新型组合降噪技术。

　　Based on the working principle of gas generator sets, it is difficult to use methods that reduce sound source noise to eliminate noise, so the main focus is to effectively block its noise propagation path. The core of noise reduction technology is to use the natural attenuation law of sound waves during propagation to reduce the pollution surface of noise. There are several specific methods to reduce noise, including sound absorption, sound insulation, and changing the direction of noise propagation. In practical engineering applications, only one of them is often used. This article proposes a new combination noise reduction technology for gas-fired generator sets by combining three methods.

　　（1）组合消声器

　　(1) Combination muffler

　　原来的消声器以阻性消声为主,功耗大,消声效果不理想。经仔细论证,应用三级组合降噪技术,将消声器改造为新型组合式消声器。该组合式消声器的主要组成部件有对喷消声减振腔、多孔式消声罩及吸声隔热层和吸声共振板等。声源通过第一级的对喷消声减振腔,可将中低频声源的噪声能量充分进行抗性耗散。二级的多孔式阻性消声罩可消去大部分高频噪声,增加了消声器对高频的适应性,而且在该腔内装有高效吸声材料,可对噪声进行充分的吸收和变向,从而最大限度地消耗噪声能量。第三级为专门设计的带共振板的排气管,进一步通过薄片的振动进行消声。经测试,新型消声器的消声量、消声频率范围(主要为消声量峰值的频率范围)及阻力损失三大指标均优于原来的消声器。此外该消声器尺寸适宜,结构刚性好,安装方便,并具有抑制再生噪声的功能。而且后部的吸声隔音层具有防腐性能,可有效地克服烟气的低温露点腐蚀,延长了消声器的使用寿命。

　　The original muffler mainly used resistive noise reduction, with high power consumption and unsatisfactory noise reduction effect. After careful demonstration, the application of three-level combined noise reduction technology has transformed the muffler into a new type of combined muffler. The main components of this combination muffler include a spray noise reduction and vibration reduction chamber, a porous noise reduction cover, a sound absorption and insulation layer, and a sound absorption resonance plate. The sound source can effectively dissipate the noise energy of the mid to low frequency sound source through the first stage of the anti spray noise reduction chamber. The secondary porous resistive muffler can eliminate most of the high-frequency noise, increasing the adaptability of the muffler to high frequencies. Moreover, high-efficiency sound-absorbing materials are installed in the cavity to fully absorb and redirect the noise, thereby maximizing the consumption of noise energy. The third level is a specially designed exhaust pipe with a resonant plate, which further reduces noise through the vibration of thin sheets. After testing, the three major indicators of the new muffler, including the noise reduction amount, noise reduction frequency range (mainly the frequency range of the peak noise reduction amount), and resistance loss, are all superior to the original muffler. In addition, the muffler has suitable size, good structural rigidity, easy installation, and the function of suppressing regenerative noise. Moreover, the sound-absorbing layer at the rear has anti-corrosion properties, which can effectively overcome the low-temperature dew point corrosion of smoke and extend the service life of the muffler.

　　（2）两级隔振衬垫

　　(2) Two level isolation pad

　　控制机械噪声和燃烧噪声的有效办法是对机组进行隔振处理。燃气机、发电机与钢制底盘间装设复合隔振减振垫,底盘与基础之间亦垫上高效减振胶垫。经过两级隔振处理,不仅使机组的振动被有效隔断,而且使机组运行更加平稳,整体噪声显著降低。

　　The effective way to control mechanical noise and combustion noise is to isolate the unit. Composite vibration isolation and damping pads are installed between the gas turbine, generator, and steel chassis, and high-efficiency damping rubber pads are also placed between the chassis and the foundation. After two-stage vibration isolation treatment, not only is the vibration of the unit effectively isolated, but the operation of the unit is also smoother, and the overall noise is significantly reduced.

　　（3）消声排风道

　　(3) Silencing exhaust duct

　　风扇噪声是由旋转噪声和涡流噪声组成。旋转噪声由旋转风扇叶片切割空气流产生周期性扰动而引起。涡流噪声是在旋转叶片截面上发生边界层分离时,气体滑脱或分裂而成的一系列的漩涡流,从而辐射出一种非稳定的流动噪声。排风道直接与外界相通,空气流速很大,气流噪声、风扇噪声和机械噪声经此通道辐射出去。为了控制风扇和排风通道的噪声,设计了一个消音排风道。这个消音排风道长度较大,由导风槽和排风降噪腔组成。排风降噪腔的工作原理,类似于阻性消声器。可通过更换吸音材料(改变材料的吸音系数),改变吸音材料厚度、排风通道长度和宽度等参数来提高消音效果。

　　Fan noise is composed of rotational noise and eddy current noise. Rotating noise is caused by periodic disturbances generated by the cutting of air flow by rotating fan blades. Eddy noise is a series of vortex flows formed by the detachment or splitting of gas during boundary layer separation on a rotating blade section, which radiates an unstable flow noise. The exhaust duct is directly connected to the outside world, and the air flow velocity is high. The airflow noise, fan noise, and mechanical noise are radiated out through this channel. In order to control the noise of the fan and exhaust duct, a soundproof exhaust duct was designed. This soundproof exhaust duct has a relatively long length and is composed of air ducts and exhaust noise reduction chambers. The working principle of the exhaust noise reduction chamber is similar to that of a resistive muffler. The sound-absorbing effect can be improved by replacing the sound-absorbing material (changing the sound-absorbing coefficient of the material), changing the thickness of the sound-absorbing material, the length and width of the exhaust duct, and other parameters.

　　（4）消声进气道

　　(4) Silencing intake duct

　　机组工作在封闭的机房里面,从广义上讲,进气系统包括机组的进风通道和发动机的进气系统。进风通道和排风通道一样直接与外界相通,空气的流速很大,气流的噪声和机组运转的噪声都经进风通道辐射到外面。发动机进气系统的噪声是由进气门周期性开、闭而产生的压力波动所形成,其噪声频率一般处于500Hz以下的低频范围。在机房墙上设置了两个消声进气道,分别作为机房的进风口和发动机的进气口。由于排风造成的室内负压,使冷空气自然通过消声进气道进入机房内,将机体散发的热量顺利排出。从而保证了机房内有足够的新鲜空气。

　　The crew works in a closed computer room, and in a broad sense, the intake system includes the intake duct of the crew and the intake system of the engine. The inlet duct, like the exhaust duct, is directly connected to the outside world. The air flow velocity is high, and the noise of the airflow and the operation of the unit are radiated to the outside through the inlet duct. The noise of the engine intake system is formed by pressure fluctuations caused by the periodic opening and closing of the intake valve, and its noise frequency is generally in the low frequency range below 500Hz. Two soundproof air intakes have been installed on the wall of the computer room, serving as the air inlet for the computer room and the engine. Due to the negative pressure caused by exhaust, cold air naturally enters the computer room through the soundproof intake duct, smoothly dissipating the heat emitted by the machine body. This ensures that there is sufficient fresh air in the computer room.

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