Abstract
In a boiler having smaller thermal capacity, the amount of exhaust fume like NOx, CO, CO_2 should be decreased as soon as possible for the sake of reducing air-polluting substances. A premixed-combustion type boiler with a multi-port burner plate is promising for its reduction and thus has been used as a water heater for home and business use. But this type of boiler has a strong tendency of extremely loud noise and therefore it is necessary to propose a noise reduction method. In this paper, the proposed reduction method is based on synchronization of frequency, in which the frequency of oscillation noise that is close to the resonance frequency of combustion system can be shifted to that of external exciting signal. In experimental results, giving an appropriate exciting signal, the sound level of the total system can be lowered by about 30dB and it is found that the proposed noise reduction method is effective.
