Fig. 1 View of 10L80MC engine
Fig. 2 Spectrum of noise
3. PREDICTION OF EFFECT OF LAGGING AND ITS APPLICATION RESULT
Lagging is often used to reduce the noise radiated from the pipe. It is used inevitably in case of being unable to reduce noise source itself. But it has generally been used combining with heat insulation in the power plant and the chemical plant. Here assuming that it is difficult to suppress the aerodynamic noise generated by the impeller, the effect of the lagging on the noise reduction is studied.
A common lagging method is to combine an absorbed material (e.g. Rock wool) and a sound isolation material (e.g. lead). There are several types of lagging as shown in Fig. 3 and they are selected depending on demand. Examples of Transmission Loss (TL) by lagging are shown in Fig. 4 and Fig. 5.
These figures show the TL of the conventional method and the new method respectively.
The black and white symbol in these figures show the experimental and calculation result respectively. The calculation value is 70% of the value calculated by Eq. (2)
