The slope and flow rate of Channels

The building of micro hydropower station- The slope and flow rate of Channels

Channel between inlet and end to the forebay must be a certain slope gradient to make the water flow smoothly. Such as the channels along the horizontal direction of the 500 meters, the channel bottom fall 1 meter vertical direction in these 500 meters, the channel slope is known as 1/500.

Channel slope should take the following points as consideration:

The choice of excessive slope steep (channels), velocity will be large, although the cross section of the channel can be smaller, but the head loss is big, power generation will be less, and the erosion of the channels will be serious. On the other hand, too small of the channels slope (flat), slow velocity, cross section is larger, sediment deposition easily, easy to its weeds, finally affect the water flow through. Therefore, the slope cannot be too big or too small, according to the situation of channel base soil to make the appropriate design. If the head gap is big, water abundant, slope can be steep, and all this can reduce the channel cross section, channel area and civil works; Flat terrain area, small difference, the head is precious, slope can be smaller. Generally speaking, channel slope of micro hydro power station is less than 1/500.

Channel flow rate

Velocity is related to channel slope and water cross section, the micro hydropower station can take the channel base soil as the velocity reference to design the flow rate.

In actual construction, in order to prevent sediment deposition, require not less than 0.4 m/s average flow velocity. When the velocity is greater than 0.75 meters per second, there is not easy for grass inside the earth canal; when the flow rate is less than 0.5 m/s, weeds is easy to breed. As a result, the average flow velocity inside the earth canal had better use in 0.5m ~ 0.8m / SEC. Uneven stone channel average flow velocity optional 0.7 ~ 1.0 m/s, concrete casing channel average flow velocity can use 0.8 ~ 1.2 m/s.

The channel sand washing and drainage facilities

Circular channels around the mountain, there are often rain flow from the hill into the channel with mud, therefore a water outlet gate or lateral overflow dam in the terrain along the channel appropriate place is needed, part of the sediment will settle down, so the channel in every certain distance set to grit chamber (20 ~ 40 cm in general than canal bottom concave)