Chapter+5-6

approximate limits of head range from 60 to 125% of design head.
Page 111(5.2)
8
Turbine Selection and Plant Capacity Determination
Propeller turbines have been developed for heads from 5 to 200 ft（1ft==0.3048m） but are normally used for heads less than 100 ft. For fixed blade propeller turbines the limits of flow operation should be between 75 and 100% of bestefficiency flow. Kaplan units may be operated between 25 and 125% of the best-efficiency discharge. The head range for satisfactory operation is from 20 to 140% of design head.
For practical purposes there are some definite limits of use that need to be understood in the selection of turbines for specific situations. Impulse turbines normally have most economical application at heads above 1000 ft, but for small units and cases where surge protection is important, impulse turbines are used with lower heads.
1
Turbine Selection and Plant Capacity Determination
Basic procedures
Turbine selection and plant capacity determination require that rather detailed information has been determined on head and possible plant discharge as described earlier. In practice, different selection procedures are used. Engineering firms or agency engineering staff do the selection using experience curves based on data from units that have already been built and installed or tested in laboratories.
Page 111(5.3)
10
Turbine Selection and Plant Capacity Determination
The difficulty of transporting large runners sometimes makes it necessary to limit their size. A runner with a maximum overall diameter of 18 ft (5.5 m) is about the largest that can be shipped by rail. Larger units require construction in segments and field fabrication with special care. Field fabrication is costly and practical only for multiple units where the cost of facilities can be spread over many units.
Page 111(5.2)
9
Turbine Selection and Plant Capacity Determination
• Determination of theቤተ መጻሕፍቲ ባይዱnumber of units
Normally, it is most cost effective to have a minimum number of units at a given installation. However, multiple units may be necessary to make the most efficient use of water where flow variation is great. Factors such as space limitations by geologic characteristics or existing structure may dictate larger or smaller units.
Page 111(5.3)
11
Turbine Selection and Plant Capacity Determination
Page 110(5.1)
Fig.4.25 Application ranges for conventional hydraulic turbines
6
Turbine Selection and Plant Capacity Determination
Limits of use of turbine types
Page 108(5.1)
5
Figure 5.1 Nomograph for determining installed capacity.
Turbine Selection and Plant Capacity Determination
Figure 4.25 is a useful selection chart for determining the type of
Page 107(5.1)
3
Turbine Selection and Plant Capacity Determination
It is seen that there are numerous parameters that can be varied to achieve the best selection. The usual practice is to base selection on the annual energy output of the plant and the least cost of that energy for the particular scale of hydropower installation. Thus one must recognize that determination of plant capacity requires analyses that vary the different parameters in Eq. (5.1) while applying economic analyses.
E = F(h, q, TW, d, n, H s , Pmax )
Page 107-108(5.1)
4
Turbine Selection and Plant Capacity Determination
For preliminary planning it is sometimes useful to get an order of magnitude estimate of the unit (or units) capacity and cost to be expected. A curve (Fig. 5.1) prepared by consulting engineers TippettsAbbett-McCarthy-Stratton is useful in making such trial evaluations. If the energy costs exceed 60 mills/kWh (1981 prices), the economics of the development will be marginal. The curves presented are for conditions of water flow and yield of rivers in the northeastern United States.
Page 107(5.1)
2
Turbine Selection and Plant Capacity Determination
Another approach that preferred by manufacturers is that they are provided with the basic data on head, water discharge, turbine setting possibilities, and load characteristics. The selection is then based on hill curves from model performance data that are proprietory in nature. Normally, the manufacturers provide a checklist similar to Table 5.1 which is the basis for making the selection. The manufacturer furnishes preliminary estimates of the cost of the turbines and necessary mechanical equipment and controls, together with basic characteristics and dimensions of the hydropower units.