Effective closing time factor
Reduced free flow area in the throttle control system:
$f_r$ | reduced free flow area in the throttle control system | $\mathrm{-}$ |
$Q$ | flow coefficient | $\mathrm{-}$ |
$Q_{max}$ | max. flow coefficient | $\mathrm{-}$ |
Relative Flow:
$Q_p$ | relative Flow | $\mathrm{-}$ |
$f_r$ | reduced free flow area in the throttle control system | $\mathrm{-}$ |
$p$ | pressure parameter | $\mathrm{-}$ |
Pressure parameter:
$p$ | pressure parameter | $\mathrm{-}$ |
$∆h$ | theoretical pressure in the closure at full opening | $\mathrm{m}$ |
$h_0$ | rated net head | $\mathrm{m}$ |
Valve speed:
$v_0$ | valve speed | $\mathrm{m/s}$ |
$Q_0$ | flow | $\mathrm{m^3/s}$ |
$D_0$ | valve diameter | $\mathrm{mm}$ |
Effective closing time factor:
$c_{ef}$ | effective closing time factor | $\mathrm{-}$ |
$Q_{pn}$ | relative flow in position n | $\mathrm{-}$ |
Flow characteristics:
The flow characteristic is the dependence of the actual flow rate on the position of the control actuator of the control system.
The flow characteristics of Fig. 1-7 are the dependence of the actual flow rate on the position of the valve of the control system.
Example:
We have to determine the difference between the effective shut-off time for the flow characteristic of the valve and the flow characteristic of the control actuator (hydraulic cylinder) according to Fig. 8 shut-off butterfly valve $DN300$ with the following parameters:
$h_0 = 33\ \mathrm{m}$; $Q_0 = 0,314\ \mathrm{m^3/s}$; $\xi = 0,106$
$s/s_{max}$ | $Q_1$ | $Q_2$ |
---|---|---|
0 | 0,951 | 0,951 |
10 | 0,885 | 0,888 |
20 | 0,733 | 0,755 |
30 | 0,531 | 0,583 |
40 | 0,373 | 0,433 |
50 | 0,249 | 0,306 |
60 | 0,183 | 0,218 |
70 | 0,123 | 0,155 |
80 | 0,073 | 0,102 |
90 | 0,035 | 0,047 |
100 | 0 | 0 |
$Q_1$ | flow characteristic of the valve | $\mathrm{-}$ |
$Q_2$ | flow characteristic of the control actuator | $\mathrm{-}$ |
Valve speed:
Theoretical pressure in the closure at full opening:
Pressure parameter:
$s/s_{max}$ | $Q_{p1}$ | $Q_{p2}$ |
---|---|---|
0 | 1 | 1 |
10 | 0,997 | 0,998 |
20 | 0,989 | 0,99 |
30 | 0,964 | 0,973 |
40 | 0,918 | 0,941 |
50 | 0,827 | 0,879 |
60 | 0,729 | 0,787 |
70 | 0,577 | 0,667 |
80 | 0,385 | 0,505 |
90 | 0,196 | 0,259 |
100 | 0 | 0 |
$Q_{p1}$ | relative flow characteristic of the valve | $\mathrm{-}$ |
$Q_{p2}$ | relative flow characteristic of the control actuator | $\mathrm{-}$ |
$c_{ef1}$ | effective closing time factor (valve) | $\mathrm{-}$ |
$c_{ef2}$ | effective closing time factor (control actuator) | $\mathrm{-}$ |
Literature:
- F. Strohmer: Investigating the characteristics of shutoff valves by model tests. Water Power & Dam Construction 1977.
- By G. L. Beichley, M. ASCE and A. J. Peterka, F. ASCE: Hydraulic design of Hollow-Jet valve stilling basins. Journal of the hydraulics division 1961.
- Stanislav Kratochvil: Vodní nádrže a přehrady. 1961.
- Б. И. ЯНЬШИН: ЗАТВОРЫ И ПЕРЕХОДЫ ТРУБОПРОВОДОВ. 1962.