空氣調和用 Multi-Blade Fan의 流動特性에 관한 硏究

Abstract

As more people live in skyscrapers, the demands to live in pleasant indoor environment are increasing. The most important thing for pleasant indoor environment is air conditioning and ventilation for indoor heating and cooling is necessary. And the indoor air contaminated due to various indoor elements must be ventilated. For ventilation of indoor air, an air-conditioning fan is generally used. Recently, as main part of indoor air-conditioning system, high quality, high efficiency and low-noise production of the fan are importantly considered. In particular, as noise structures of hydraulic machinery are closely related with internal flowing conditions, internal flowing conditions of fan are very important. As a multi-blade fan (Sirocco Fan) has extensive flowing range and even functions compared to those of other fans and produces less noise, it is extensively used for air-conditioning or factory. The multi-blade fan was invented by Sam Davidson in England in 1864 and was used in the book by Eck in 1974. It is called squirrel-cage fan, drum-rotor fan, and FC(Forward-Curved) centrifugal fan in Europe or north America. It is also extensively used for massive work such as air-conditioning of buildings and industrial blowers or for everyday life such as air-conditioners, fan heaters, hair-dryers and automobiles' ventilators in small scale. In a design of the multi-blade fan, it is important to look at flowing at volute that is inhaled by a multi-blade fan in order to identify its correlations with functions and flowing inhaled by the multi-blade fan attached to automobile indoor air-conditioner within closed square ducts. This study as a flowing visualization test using PIV visualized velocity vector distribution at normal and compressed flowing and analysed flowing patterns of velocity distribution and re-stress according to change in rotation number of the multi-blade fan (950RPM, 1100RPM and 1250RPM). The results of this study are presented as follows: (1) The more revolution per minute, the more flowing is inclined to driving motors of multi-blade fan. (2) This is because of the eccentricity occurring by decreased output of multi-blade fan rather than the centrifugal force occurring during rotation of the driving motor (3) Maximum stress distribution occurs at a place remote from the driving motor in the horizontal axis at 1250 RPM of rotational number unlike velocity vector. (4) This is generated by centrifugal force at remote place and differences in pressure according to different structures of forms such as orifice on the wall.