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Noise Control of Engine Driven Portable Generator Set




Major noise sources in a noisy portable I. C. engine driven generator set have been identified. The generator set engine is petrol start and kerosene run. The exhaust silencer of the engine was providing substantial insertion loss. The separation of engine combustion and mechanical noise indicated that their contribution was almost equal. Since generally combustion noise is more than mechanical noise, the main noise sources were considered to be mechanical in nature. Sound intensity measurements were performed to identify major noise sources in the generator set when the exhaust was ducted away. The results of these measurements indicated that the main sources of noise in the generator set are: cooling fan cover, silencer shell, silencer cover and the engine crankcase. Noise control measures were applied to these parts. Sound pressure and power levels were measured before and after the application of noise control measures. Constrained layer damping treatment and stiffening of the cooling fan cover had a combined effect of reducing the sound pressure level by about 3dB(A). Rigid clamping of the silencer also reduced the noise level. A partial enclosure was designed for the generator set. The partial enclosure reduced the sound pressure and power levels by about 4 and 3.7dB(A), respectively. There was an increase in the engine cylinder head temperature due to the enclosure, but the increase in temperature was considered to be safe. An overall noise reduction of 8.5dB(A) was obtained on side 4 of the generator set as a result of the implementation of all the noise control measures. The noise reduction on the other sides of the generator set was also substantial. # 1998 Elsevier Science Ltd. All rights reserved

便携式汽油机发电机组的主要噪声来源已经确定,其中发电机组的发动机以燃烧汽油启动,运行时则使用煤油。发动机的排气消音器会提供大量的插入损失。将燃烧噪声和机械噪声分离开后发现他们两者的贡献几乎是相等的,一般情况下燃烧噪声的影响是超过机械噪声的,因此噪声的主要来源被认为是机械。声强测量可以检测出在排气过程中噪声的主要来源。测量结果表明,发电机组主要噪声来源包括冷却风扇盖、 消音器外壳、消音器盖和发动机曲轴箱。噪声控制的措施也会主要应用于这些部分。我们分别测量了噪声控制措施应用前后的噪声声压和声功率。分析测量结果得到,约束层的抑制处理和对冷却风扇罩的加强的综合作用下噪声声压降低了大约3 dB(A)。消音器的刚性夹紧也降低了噪音水平。针对发电机组设计的局部隔音罩使噪声的声压和声功率分别下降了4 dB(A)和3.7 dB(A)。虽然隔音罩引起了一个气缸盖的温度增长,但温度增长仍在安全范围内。在使用了所有的噪声控制措施后,在发电机组的第4侧上的整体噪声降低了8.5 dB(A).而安装了噪声控制装置的发电机组在其他方面仍保持着可观的性能。

# 1998爱思唯尔科学有限公司版权所有



The first task of any noise control programme is to identify the major sources of noise radiation. The greatest reduction in noise can only be achieved by reducing the noise radiated from the most noisy sources. A reduction of noise therefore requires not only the treatment of many different sources but also calls for different approaches in each particular case depending upon the degree of the contribution of the various individual sources to the total noise and finally upon the economical aspects. The noise of vehicles and machines is mainly defined by the noise generated by their power plant which is usually an engine. One of the predominating contributor to the total engine noise is the noise emitted by the engine surfaces. Techniques to find the important noise radiating areas of the engine surfaces and noise reduction measures have been reported in the literature. 1–6 Different techniques for measuring combustion noise have also been suggested. Analysis of noise produced by piston slap and methods of its control in diesel engines was given by Haddad and Howard 9 and Rohrle. Pope et al. 11 have shown the use of acoustic intensity scans for sound power measurement and for noise source identification on surface transport vehicles. A comparison of acoustic intensity measurement with surface intensity and lead wrapping measurements on a diesel engine was reported by Reinhart and Crocker.


Portable engine driven generators are used to supply electricity in shops, offices and homes when there is a break in power supply. In these generators, the alternator and engine are mounted on a frame through rubber mounts as shown in Fig. 1. Such generators are normally placed outside shops/offices and generate high noise levels causing annoyance to people in the neighbourhood. In the present study noise control of one such, particularly noisy generator set (Fig. 1), was undertaken.


Generator noise may be controlled by reducing the excitation applied to the structure by the engine combustion process and mechanical impacts. In addition noise may be controlled at source by modifying the structure so that (a) the basic engine structure accepts the forces applied to it by the combustion process and mechanical impacts, with the minimum structural deflection, (b) the panels and covers which radiate noise are isolated from structural vibration, or designed for minimum response to vibration excitation, (c) the vibration energy in the normal modes of vibration is rapidly dissipated as heat by vibration damping treatments, and (d) designing a partial or full enclosure. The methodology for investigating, evaluating and designing controls for noise emanating from an internal combustion engine or arising from the addition of necessary component has been described by Baxa.



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