Study On Hydraulic Characteristics And Sediment Removal Capacity Of Typical Filters

Filter is the key equipment in the irrigation system, which can remove all kinds of impurities to avoid clogging of emitter. It can improve irrigation quality and operation efficiency. Taking the irrigation system of irrigation district in Xinjiang as study object, this paper studied on the hydraulic characteristics and sediment removal capacity of five filtration systems which is composed of two kinds of filters, such as hydrocyclone with screen filter(80,100,120 mesh) and hydrocyclone with disc filter(75,120 mesh) . The results obtained are described as follows:(1) The local head loss of filters is closely related to flow rate. The local head loss increases with the flow rate increasing. The local head loss of filters is closely related to sediment content. With the sediment content increasing, the local head loss of filters increased before the filters aren't clogged seriously. Under the same composition of sediment particles, with the sediment content increasing, the amount of the big sediment particles increases. Therefore screen and disc filters are clogged obviously, and the allowable running time of system is shortened. Degree of clogging and allowable running time negatively correlates. In the same condition, the local head loss of screen filters is smaller than disc filters, but the running time of screen filters is longer than disc filters. The local head loss and the flow rate of filters change slowly then rapidly with running time increasing. When the local head loss of screen filters and disc filters reach 2~3m and 4~5m, the effect of the clogging becomes obvious, then the head loss begins to increase rapidly, and the flow rate begins to reduce rapidly, that affects the normal operation of system, therefore the screen and disc of filters should be flashed.(2) The general characteristics of the total separation efficiency in five filtration systems manifestation: the greater mesh, the greater total separation efficiency. Under experiment condition,the general characteristics of the grade efficiency in five filtration systems is that all the grade efficiency is less than ten percent when the size of sand particle is less than 50 m, and, that all the grade efficiency is one hundred percent when the size of sand particle is more than 100 m, that the grade efficiency of five filtration system has much difference when the size of sand particle between 50 m and 100 m, mainly manifestations: hydrocyclone-120 mesh disc> hydrocyclone-120 mesh screen> hydrocyclone-100 mesh screen> hydrocyclone-75 mesh disc> hydrocyclone-80 mesh screen. In terms of sediment separation effect, the sediment removal capacity of disc filters is better than screen filters.(3) Under experiment condition,the d50 of sediment filtered by five filtration systems have little difference, which are about 6~8 m. The d98 of sediment filtered by disc filters are smaller than that by screen filters, and all the d98 are less than 40 m, that can meet requirements of water quality in drip irrigation.